JP7804256B2 - Hybrid vehicles - Google Patents

Description

The present invention relates to a hybrid vehicle, and more particularly to a hybrid vehicle equipped with a low-speed supercharger and a high-speed supercharger.

Technology related to vehicles equipped with a low-speed supercharger used in the low-speed range of an internal combustion engine and a high-speed supercharger used in the high-speed range of an internal combustion engine is known. For example, Patent Document 1 describes a vehicle equipped with an engine, a first turbocharger that supercharges the engine at low speeds, a second turbocharger that supercharges the engine at high speeds, and first and second exhaust control valves for selecting exhaust passages associated with the first and second turbochargers and controlling the exhaust gas flow rate. In this vehicle, the opening and closing operation of the exhaust control valve is controlled according to the engine operating conditions to achieve stratified combustion or homogeneous combustion using the first and second turbochargers.

Japanese Patent Application Laid-Open No. 2007-177794

The vehicle described in Patent Document 1 is equipped with an internal combustion engine as a drive source, and selects which of the turbochargers to use depending on the operating conditions of the internal combustion engine. However, in a hybrid vehicle equipped with a traction motor as a drive source in addition to an internal combustion engine, the driving mode changes depending on multiple conditions, not just the operating conditions of the internal combustion engine. In such hybrid vehicles, it is necessary to appropriately select between a low-speed turbocharger and a high-speed turbocharger in order to improve fuel economy and drivability.

The present invention was made in light of these issues, and its purpose is to improve fuel economy and drivability by more appropriately selecting a low-speed supercharger and a high-speed supercharger in a hybrid vehicle capable of running in multiple driving modes.

To achieve the above objective, the hybrid vehicle of the present invention is equipped with an internal combustion engine and a traction motor, and switches between a series mode in which the vehicle runs using the traction motor as a drive source while generating electricity using power from the internal combustion engine, and a parallel mode in which the vehicle runs using the internal combustion engine and the traction motor as a drive source. The hybrid vehicle is equipped with a low-speed supercharger used in the low-speed to medium-speed range of the internal combustion engine, a high-speed supercharger used in the high-speed to medium-speed range of the internal combustion engine, and a control device that controls switching between the use of the low-speed supercharger and the high-speed supercharger. The control device uses the low-speed supercharger when the internal combustion engine is operated in the medium-speed range in the parallel mode, and uses the high-speed supercharger when the internal combustion engine is operated in the medium-speed range in the series mode.

This configuration expands the range of use of the high-speed supercharger in series mode, and expands the range of use of the low-speed supercharger in parallel mode. As a result, in a hybrid vehicle whose driving mode changes not only depending on the operating conditions of the internal combustion engine but also, for example, the temperature of the drive battery that supplies power to the driving motor, fuel economy can be improved in series mode, and output responsiveness can be improved in parallel mode. Therefore, the hybrid vehicle of the present invention, which can run in multiple driving modes, can more appropriately select the low-speed supercharger and the high-speed supercharger to improve drivability and fuel economy.

Furthermore, when the internal combustion engine is operated in a predetermined high-speed shaft vibration region that includes at least a portion of the medium-speed region, the shaft of the high-speed supercharger is more likely to vibrate than when the internal combustion engine is operated in other regions, and it is preferable that the control device use the low-speed supercharger when the internal combustion engine is operated in the predetermined high-speed shaft vibration region of the medium-speed region in the series mode.

With this configuration, in a specific high-speed shaft vibration range where the high-speed supercharger shaft is prone to vibration, the low-speed supercharger is used even in series mode, thereby suppressing vibration of the high-speed supercharger shaft. In this case, there is no need to increase the amount of lubricating oil supplied to the high-speed supercharger shaft, which suppresses the reduction in fuel efficiency caused by an increase in the amount of lubricating oil supplied.

Furthermore, it is preferable that the shaft of the low-speed supercharger is more likely to vibrate when the internal combustion engine is operated in a predetermined low-speed shaft vibration region that includes at least a portion of the medium-speed region than when the internal combustion engine is operated in other regions, and that the predetermined low-speed shaft vibration region and the predetermined high-speed shaft vibration region include an overlapping region in the medium-speed region where they overlap, and that the control device uses the high-speed supercharger and increases the amount of lubricating oil supplied to the shaft of the high-speed supercharger when the internal combustion engine is operated in the overlapping region of the medium-speed region in the series mode.

With this configuration, in the overlapping region where both the low-speed supercharger shaft and the high-speed supercharger shaft are prone to vibration, the amount of lubricating oil supplied to the high-speed supercharger shaft can be increased to suppress vibration of that shaft.

Furthermore, it is preferable that the control device use the low-speed supercharger when the internal combustion engine is operated in the medium speed range in the series mode and the charge level of the drive battery that supplies power to the traction motor falls below a predetermined value.

This configuration allows the use of a low-speed turbocharger to improve the responsiveness of the internal combustion engine's output when there is a possibility that a sudden increase in output from the internal combustion engine is required to charge the drive battery.

The hybrid vehicle of the present invention is capable of running in multiple driving modes, and allows for more appropriate selection of a low-speed supercharger and a high-speed supercharger to improve drivability and fuel economy.

1 is a schematic configuration diagram of a driving system of a hybrid vehicle according to a first embodiment. FIG. 2 is a schematic diagram showing the intake and exhaust system of the engine. FIG. 2 is an explanatory diagram showing the operating ranges of a low-speed turbo and a high-speed turbo. 4 is a flowchart showing a process of turbo switching control according to the first embodiment. 10 is a flowchart showing a process of turbo switching control according to a second embodiment. FIG. 10 is an explanatory diagram showing an example of a region where vibration is likely to occur in the shaft. 10 is a flowchart showing a process of turbo switching control according to a third embodiment.

[First embodiment]
A first embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a schematic diagram of a drivetrain of a hybrid vehicle according to the first embodiment. A hybrid vehicle 1 (hereinafter referred to as "vehicle 1") is a vehicle such as a plug-in hybrid vehicle (PHV) or hybrid vehicle that is capable of driving wheels using the output of an engine (internal combustion engine) 2 and is equipped with an electric front motor (driving motor) 4 that drives the wheels. A plug-in hybrid vehicle is a vehicle that can supply power from an external power source to a drive battery mounted on the vehicle and can supply power from the drive battery to electrical appliances outside the vehicle.

The engine 2 drives the drive shaft 8 of the front wheels 3 via the front transaxle 7, and also drives the motor generator 9 via the front transaxle 7 to generate electricity. The engine 2 and the front wheels 3 are connected via a clutch 16 located within the front transaxle 7. The vehicle 1 is also provided with a fuel tank 17 that stores fuel to supply to the engine 2.

The front motor 4 is powered by high-voltage power supplied from the drive battery 11 and motor generator 9 mounted on the vehicle 1 via the control unit 20, and drives the drive shaft 8 of the front wheels 3 via the front transaxle 7. The motor generator 9 is capable of charging the drive battery 11 with the generated power and supplying power to the front motor 4. The drive battery 11 is composed of a secondary battery such as a lithium-ion battery, and is provided with a charge rate detector 11a that detects its charge rate (SOC: State Of Charge). The drive battery 11 is also provided with a temperature detector 11b that detects its temperature.

The control unit 20 is a control device for the vehicle 1 and is composed of input/output devices, memory devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), a timer, etc. The control unit 20 has the function of controlling the driving mode, the output of the front motor 4, the power generation and output of the motor generator 9, the fuel injection amount and fuel injection timing of the engine 2, and the engagement and disengagement of the clutch 16 in the front transaxle 7, etc.

Driving modes include EV mode, series mode, and parallel mode. In EV mode, the engine 2 is stopped and the front motor 4 is driven by power supplied from the drive battery 11 to drive the vehicle. In series mode, the clutch 16 of the front transaxle 7 is disengaged and the engine 2 operates the motor generator 9 to generate electricity. The front motor 4 is then driven by the power generated by the motor generator 9 and the power supplied from the drive battery 11 to drive the vehicle. In series mode, the rotational speed of the engine 2 is set to an efficient value. In parallel mode, the clutch 16 of the front transaxle 7 is engaged, mechanically transmitting power from the engine 2 and driving the front motor 4 to drive the front wheels 3.

The control unit 20 switches the driving mode according to multiple conditions, such as vehicle speed, engine 2 load (target torque), and drive battery 11 charge rate and temperature. Specifically, the control unit 20 sets the driving mode to parallel mode when the vehicle speed is equal to or greater than a predetermined speed or when the target torque is equal to or greater than a predetermined torque. When the vehicle speed is less than the predetermined speed or when the target torque is less than the predetermined torque, the control unit 20 switches the driving mode between EV mode and series mode based on the drive battery 11 charge rate. This allows the output required for driving to be obtained in parallel mode when the engine 2 is efficient, such as in high-speed ranges, or when the target torque is high, and improves fuel economy in medium- to low-speed ranges by using series mode. Furthermore, the control unit 20 sets the driving mode to parallel mode when the drive battery 11 temperature is less than a predetermined low-temperature temperature or greater than a predetermined high-temperature temperature. This allows the output required for driving to be stably obtained in parallel mode when the drive battery 11's charge/discharge power is limited due to low or high temperatures.

Figure 2 is a schematic diagram showing an example of the intake and exhaust system of engine 2. Engine 2 is a diesel engine with multiple cylinders. However, engine 2 may also be a gasoline engine. An intake passage 31 of engine 2 is provided with, in order from upstream toward engine 2, an air filter 32, an intake throttle 33, etc. An exhaust passage 35 of engine 2 is provided with, in order from downstream toward engine 2, an oxidation catalyst 36, a particulate filter 37, an exhaust throttle 38, a muffler 39, etc. An EGR device (not shown) that recirculates a portion of the exhaust gas to the intake side may also be provided in engine 2.

The engine 2 is further provided with a low-speed turbocharger (low-speed supercharger) 50 (hereinafter referred to as the low-speed turbo 50) and a high-speed turbocharger (high-speed supercharger) 60 (hereinafter referred to as the high-speed turbo 60). The low-speed turbo 50 has a compressor 50c provided in the intake passage 31, a turbine 50t provided in the exhaust passage 35, and a shaft 50s connecting the compressor 50c and the turbine 50t. The intake passage 31 is provided with a bypass passage 51 that allows intake air to flow to the engine 2, bypassing the compressor 50c, and the bypass passage 51 is provided with a bypass valve 52 that opens and closes the bypass passage 51. The exhaust passage 35 is further provided with a bypass passage 53 that allows exhaust gas from the engine 2 to flow, bypassing the turbine 50t, and the bypass passage 53 is provided with a bypass valve 54 that opens and closes the bypass passage 53.

The high-speed turbo 60 has a compressor 60c provided in the intake passage 31, a turbine 60t provided in the exhaust passage 35, and a shaft 60s connecting the compressor 60c and the turbine 60t. The exhaust passage 35 is provided with a bypass passage 61 that allows exhaust from the engine 2 to bypass the turbine 60t, and the bypass passage 61 is provided with a wastegate valve 62 that opens and closes the bypass passage 61. The bypass valves 52, 54 and the wastegate valve 62 are controlled to open and close by the control unit 20, thereby switching between the low-speed turbo 50 and the high-speed turbo 60.

The vehicle 1 is also provided with a hydraulic circuit 70 for supplying lubricating oil to the shafts 50s and 60s. The hydraulic circuit 70 includes a lubricating oil storage tank, a pump, and multiple flow control valves (all not shown), and the control unit 20 controls the amount of lubricating oil (hydraulic pressure) supplied to each of the shafts 50s and 60s.

Figure 3 is an explanatory diagram showing the operating ranges of the low-speed turbo 50 and the high-speed turbo 60. As shown in the figure, the low-speed turbo 50 and the high-speed turbo 60 each have their operating ranges defined within the operating range of the engine 2, with the horizontal axis representing the engine 2 speed and the vertical axis representing torque. The low-speed turbo 50 is a small-capacity turbocharger used in the range extending from the low-speed range A1 to the medium-speed range A2 (the range marked with diagonal lines in Figure 3) of the engine 2. On the other hand, the high-speed turbo 60 is a large-capacity turbocharger used in the range extending from the medium-speed range A2 to the high-speed range A3 of the engine 2. The medium-speed range A2 is a range in which both the low-speed turbo 50 and the high-speed turbo 60 can be used.

Generally, when a small-capacity low-speed turbo 50 is used, the engine 2 output is more responsive (turbine speed is more likely to change quickly) and back pressure is more likely to increase than when a high-speed turbo 60 is used, resulting in reduced fuel economy. On the other hand, when a large-capacity high-speed turbo 60 is used, the engine 2 output is less responsive and back pressure is less likely to increase than when a low-speed turbo 50 is used, resulting in improved fuel economy.

Therefore, in the vehicle 1 of this embodiment, the turbo switching control described below is used to switch between the low-speed turbo 50 and the high-speed turbo 60, thereby achieving both improved fuel economy and improved drivability (improved output responsiveness). Figure 4 is a flowchart showing the turbo switching control process of the first embodiment. The process shown in Figure 4 is repeatedly executed by the control unit 20 at predetermined time intervals while the vehicle 1 is operating in series mode or parallel mode.

The control unit 20 first determines in which region the target output of the engine 2 (target rotation speed and target torque; hereinafter referred to as "engine target output") is located, i.e., whether the engine 2 is operating in the low rotation region A1, the medium rotation region A2, or the high rotation region A3 (step S11). If the control unit 20 determines in step S11 that the engine target output is in the low rotation region A1, it skips the processing of step S12, which will be described later, and uses the low rotation turbo 50 (step S13). Thereafter, the control unit 20 again executes the processing from step S11 onwards. As a result, the low rotation turbo 50 is used when the engine 2 is in the low rotation region A1.

On the other hand, when the control unit 20 determines in step S11 that the engine target output is in the high rotation range A3, it skips the processing of step S12 described below and uses the high rotation turbo 60 (step S14). The control unit 20 then executes the processing from step S11 onwards again. As a result, the high rotation turbo 60 is used in the high rotation range A3 of the engine 2.

When the control unit 20 determines that the engine target output is in the medium rotation range A2, it then determines whether the vehicle 1's driving mode is parallel mode or series mode (step S12). When the control unit 20 determines in step S12 that the driving mode is parallel mode, it uses the low rotation turbo 50 (step S13). Thereafter, the control unit 20 again executes the processing from step S11 onwards. That is, when the driving mode is parallel mode, the medium rotation range A2 of the engine 2 becomes the usage range for the low rotation turbo 50, and therefore the usage range for the low rotation turbo 50 is expanded by the amount of the medium rotation range A2 compared to when the driving mode is series mode.

On the other hand, when the control unit 20 determines in step S12 that the driving mode is series mode, it uses the high-speed turbo 60 (step S14). Thereafter, the control unit 20 executes the processing from step S11 onwards again. That is, when the driving mode is series mode, the medium speed range A2 of the engine 2 becomes the usage range of the high-speed turbo 60, and therefore the usage range of the high-speed turbo 60 is expanded by the amount of the medium speed range A2 compared to when the driving mode is parallel mode.

In this way, in the vehicle 1 of the first embodiment, the usage ranges of the low-speed turbo 50 and the high-speed turbo 60 are changed depending not only on the operating conditions of the engine 2 but also on the driving mode of the vehicle 1. In other words, in the series mode selected in the medium-low speed range, fuel efficiency can be improved by expanding the usage range of the high-speed turbo 60 rather than the low-speed turbo 50, which is normally used in the low-speed range of the engine 2. Furthermore, in the parallel mode selected in the high-speed range, the output responsiveness of the engine 2 can be improved by expanding the usage range of the low-speed turbo 50 rather than the high-speed turbo 60, which is normally used in the high-speed range.

Furthermore, as described above, when the temperature of the drive battery 11 in the vehicle 1 is below a predetermined temperature, charging and discharging of the drive battery 11 is restricted, and the driving mode switches to parallel mode, which uses the engine 2 as the drive source. A situation in which the temperature of the drive battery 11 is below a predetermined temperature is likely to occur when the front motor 4 has not been used for a long period of time, i.e., immediately after the vehicle 1 has started to operate. Therefore, it is expected that the engine target output will shift from the low rotation and low torque side to the high rotation and high torque side, as shown by the white arrow in Figure 3, for example. In other words, the engine target output is likely to shift between the low rotation region A1 and the medium rotation region A2 in Figure 3.

In the above-described situation, assume that the driver accelerates or decelerates the vehicle 1, causing the engine target output to shift between point P1 in the low-speed range A1 and point P2 in the medium-speed range A2, as shown in FIG. 3 . In this case, if the medium-speed range A2 is set as the range in which the high-speed turbo 60 is used, the turbocharger used will frequently switch as the engine target output shifts between point P1 and point P2. In the vehicle 1 of the first embodiment, the medium-speed range A2 is set as the range in which the low-speed turbo 50 is used, so even if the engine target output shifts between point P1 and point P2, the low-speed turbo 50 is always used. In this way, by expanding the range in which the low-speed turbo 50 is used when the driving mode is in parallel mode, frequent switching between the low-speed turbo 50 and the high-speed turbo 60 is suppressed when the drive battery 11 is in a low-temperature state, thereby stabilizing the output of the engine 2 and improving drivability.

As explained above, in the vehicle 1 of the first embodiment, the control unit 20 uses the low-speed turbo 50 when the engine 2 is operating in the medium-speed range A2 in parallel mode, and uses the high-speed turbo 60 when the engine 2 is operating in the medium-speed range A2 in series mode.

This configuration expands the range of use of the high-speed turbo 60 in series mode, and expands the range of use of the low-speed turbo 50 in parallel mode. As a result, fuel economy can be improved in series mode, and output responsiveness can be improved in parallel mode. It also reduces frequent switching of the turbocharger used. Therefore, according to the vehicle 1 of the first embodiment, in a vehicle 1 that can run in multiple driving modes, it is possible to more appropriately select the low-speed turbo 50 and the high-speed turbo 60, thereby improving drivability and fuel economy.

[Second embodiment]
Next, a description will be given of a vehicle 1 according to a second embodiment. The vehicle 1 according to the second embodiment has the same configuration and function as the first embodiment, except that the turbo switching control is different from that of the first embodiment. Therefore, the same components are denoted by the same reference numerals, and the description thereof will be omitted.

Figure 5 is a flowchart showing the turbo switching control process of the second embodiment. The process shown in Figure 5 is repeatedly executed by the control unit 20 at predetermined time intervals while the vehicle 1 is operating in series mode or parallel mode. Note that in the process shown in Figure 5, steps S21 to S23 and step S25 are similar to steps S11 to S13 and step S14 shown in Figure 4, and therefore their explanation will be omitted.

When the control unit 20 determines in step S22 that the driving mode is series mode, it determines whether the charge rate (charge amount) of the drive battery 11 is equal to or greater than a predetermined value (step S24) before proceeding to step S25. The predetermined value is set in advance as a value slightly higher than the charge rate at which the drive battery 11 needs to be charged.

When the control unit 20 determines that the charge rate of the drive battery 11 is equal to or higher than a predetermined value (Yes in step S24), it uses the high-speed turbo 60 (step S25). As a result, when the drive battery 11 does not need to be charged, fuel economy can be improved by using the high-speed turbo 60.

On the other hand, when the control unit 20 determines that the charge rate of the drive battery 11 is less than the predetermined value (No in step S24), it uses the low-speed turbo 50 (step S23). As a result, when the drive battery 11 needs to be charged, using the low-speed turbo 50 makes it easier to respond to requests to rapidly increase the output of the engine 2 for charging.

As explained above, in the vehicle 1 of the second embodiment, the control unit 20 uses the low-speed turbo 50 when the engine 2 is operated in the medium speed range A2 in series mode and the charge rate of the drive battery 11 that supplies power to the front motor 4 falls below a predetermined value. With this configuration, as mentioned above, when there is a possibility that a sudden increase in engine 2 output will be required to charge the drive battery 11, the low-speed turbo 50 can be used to improve the responsiveness of the engine 2 output.

[Third embodiment]
Next, a description will be given of a vehicle 1 according to a third embodiment. The vehicle 1 according to the third embodiment has the same configuration and function as the first and second embodiments, except that the turbo switching control is different from those of the first and second embodiments. Therefore, the same components are denoted by the same reference numerals, and the description thereof will be omitted.

Here, the low-speed turbo 50 and the high-speed turbo 60 are prone to vibration in the shafts 50s and 60s within their respective operating ranges. Figure 6 is an explanatory diagram showing an example of a range in which vibration is likely to occur in the shafts 50s and 60s. When the engine 2 is operated in the low-speed shaft vibration range A4 (encircled by a dashed line in the figure), which is located on the low-speed and high-load side of the operating range, the low-speed turbo 50 is prone to vibration in the shaft 50s compared to when the engine 2 is operated in other operating ranges. Similarly, when the engine 2 is operated in the high-speed shaft vibration range A5 (encircled by a dashed line in the figure), which is located on the low-speed and high-load side of the operating range, the high-speed turbo 60 is prone to vibration in the shaft 50s compared to when the engine 2 is operated in other operating ranges. Also, as shown in Figure 6, the low-speed shaft vibration range A4 and the high-speed shaft vibration range A5 overlap in the medium-speed range A2, forming an overlap region A6.

If the shafts 50s, 60s vibrate in each of the above-mentioned regions, this may cause wear or damage to the shafts 50s, 60s, or may prevent the turbochargers from operating stably, resulting in reduced fuel economy and drivability. Therefore, the vehicle 1 of the third embodiment executes the turbo switching control described below to appropriately suppress vibrations of the shafts 50s, 60s, particularly in the medium rotation region A2.

Figure 7 is a flowchart showing the turbo switching control process of the third embodiment. Note that in the process shown in Figure 7, steps S31 to S34 and step S38 are similar to steps S21 to S25 shown in Figure 5, and therefore their explanation will be omitted.

When the control unit 20 determines in step S34 that the charge rate of the drive battery 11 is equal to or greater than a predetermined value (Yes in step S34), it determines whether the engine target output is in the high-speed shaft vibration region A5 (step S35). When the control unit 20 determines that the engine target output is not in the high-speed shaft vibration region A5 (No in step S35), it skips steps S36 and S37 (described below) and uses the high-speed turbo 60 (step S38).

On the other hand, when the control unit 20 determines that the engine target output is in the high-speed shaft vibration region A5 (Yes in step S35), it further determines whether the engine target output is in the low-speed shaft vibration region A4, i.e., whether it is in the overlap region A6 (step S36).

When the control unit 20 determines that the engine target output is in the low-speed shaft vibration region A4 (in the overlap region A6; for example, see point P3 in Figure 6) (Yes in step S36), it increases the amount of lubricant supplied (oil pressure) to the shaft 60s of the high-speed turbo 60 (step S37) and uses the high-speed turbo 60 (step S38). In this way, in the medium-speed region A2 where either the low-speed turbo 50 or the high-speed turbo 60 is likely to cause vibration of the shafts 50s, 60s, the amount of lubricant supplied to the shaft 60s is increased and the high-speed turbo 60 is used, thereby suppressing vibration of the shafts 50s, 60s.

Furthermore, when the control unit 20 determines that the engine target output is not in the low rotation shaft vibration region A4 (it is in the high rotation shaft vibration region A5 outside the overlap region A6; for example, see point P4 in Figure 6) (No in step S36), it uses the low rotation turbo 50 (step S33). In this way, in the medium rotation region A2 where the shaft 60s of the high rotation turbo 60 is likely to vibrate but the shaft 50s of the low rotation turbo 50 is unlikely to vibrate, the vibration of the shafts 50s, 60s is suppressed by using the low rotation turbo 50.

Although not shown in Figure 7, if step S31 determines that the engine target output is in the low rotation region A1 and the engine target output is in the low rotation shaft vibration region A4, the amount of lubricating oil supplied to shaft 50s may be increased. Also, if step S31 determines that the engine target output is in the high rotation region A3 and the engine target output is in the high rotation shaft vibration region A5, the amount of lubricating oil supplied to shaft 60s may be increased. This makes it possible to suppress vibration of shafts 50s and 60s even in both the low rotation region A1 and the high rotation region A3.

As explained above, in the vehicle 1 of the third embodiment, when the engine 2 is operated in a predetermined high-speed shaft vibration region A5 that includes part of the medium-speed region A2, the high-speed turbo 60 is more likely to vibrate the shaft 60s than when the engine 2 is operated in other regions, and the control unit 20 uses the low-speed turbo 50 when the engine 2 is operated in the predetermined high-speed shaft vibration region A5 of the medium-speed region A2 in series mode.

With this configuration, in the specified high-speed shaft vibration region A5 where the shaft 60s of the high-speed turbo 60 is prone to vibration, the low-speed turbo 50 is used even in series mode, so there is no need to increase the amount of lubricating oil supplied to the shaft 60s of the high-speed turbo 60. As a result, it is possible to suppress a decrease in fuel efficiency due to an increase in the amount of lubricating oil supplied.

Furthermore, when the engine 2 is operated in a predetermined low-speed shaft vibration region A4, which includes part of the medium-speed region A2, the shaft 50s of the low-speed turbo 50 is more likely to vibrate than when the engine 2 is operated in other regions. The predetermined low-speed shaft vibration region A4 and the predetermined high-speed shaft vibration region A5 include an overlap region A6 in which they overlap in the medium-speed region A2. When the engine 2 is operated in the overlap region A6 of the medium-speed region A2 in series mode, the control unit 20 uses the high-speed turbo 60 and increases the amount of lubricating oil supplied to the shaft of the high-speed turbo 60.

With this configuration, in the overlap region A6 where both the shaft of the low-speed turbo 50 and the shaft of the high-speed turbo 60 are prone to vibration, the amount of lubricating oil supplied to the shaft 60s of the high-speed turbo 60 can be increased to suppress vibration of that shaft 60s.

This concludes the description of the embodiments, but the aspects of the present invention are not limited to the first to third embodiments. For example, the low-speed turbo 50 and the high-speed turbo 60 are not limited to turbochargers, and may also be superchargers or other superchargers.

Furthermore, in the third embodiment, it is possible that the low rotation shaft vibration region A4 does not overlap with the medium rotation region A2, and there is no overlap region A6 between the low rotation shaft vibration region A4 and the high rotation shaft vibration region A5. In this case, step S36 in FIG. 7 may be omitted, and the low rotation turbo 50 may be used (step S33) when it is determined in step S35 that the engine target output is in the high rotation shaft vibration region A5.

1. Vehicle 2. Engine (internal combustion engine)
4 Front motor (driving motor)
11 Drive battery 20 Control unit (control device)
50 Low-speed turbo (low-speed turbocharger, low-speed supercharger)
50s, 60s Shaft 60 High-speed turbo (high-speed turbocharger, high-speed supercharger)
A1 Low rotation range A2 Medium rotation range A3 High rotation range A4 Low rotation shaft vibration range A5 High rotation shaft vibration range A6 Overlap range

Claims (4)

A hybrid vehicle includes an internal combustion engine and a traction motor, and switches between a series mode in which the vehicle runs using the traction motor as a drive source while generating electricity using power from the internal combustion engine, and a parallel mode in which the vehicle runs using both the internal combustion engine and the traction motor as drive sources,
a low-speed supercharger used in a range from a low speed range to a medium speed range of the internal combustion engine;
a high-speed supercharger used in a range from a high speed range to a medium speed range of the internal combustion engine;
a control device that controls switching between the use of the low rotation supercharger and the high rotation supercharger,
The control device uses the low-speed supercharger when the internal combustion engine is operated in the medium speed range in the parallel mode, and uses the high-speed supercharger when the internal combustion engine is operated in the medium speed range in the series mode. the high-speed supercharger is such that, when the internal combustion engine is operated in a predetermined high-speed shaft vibration region including at least a part of the medium-speed region, the shaft is more likely to vibrate than when the internal combustion engine is operated in other regions;
The hybrid vehicle according to claim 1 , wherein the control device uses the low rotation supercharger when the internal combustion engine is operated in the predetermined high rotation shaft vibration region of the medium rotation region in the series mode. the low rotation supercharger is configured so that, when the internal combustion engine is operated in a predetermined low rotation shaft vibration region including at least a part of the medium rotation region, the shaft thereof is more likely to vibrate than when the internal combustion engine is operated in other regions;
the predetermined low rotation shaft vibration region and the predetermined high rotation shaft vibration region include an overlap region in which they overlap with each other in the medium rotation region,
3. The hybrid vehicle according to claim 2, wherein the control device uses the high-speed supercharger and increases the amount of lubricating oil supplied to a shaft of the high-speed supercharger when the internal combustion engine is operated in the overlap region in the series mode. A hybrid vehicle as described in any one of claims 1 to 3, wherein the control device uses the low-speed supercharger when the internal combustion engine is operated in the medium speed range in the series mode and the charge level of the drive battery that supplies power to the traction motor falls below a predetermined value.