Hybrid vehicles

Abstract

We aim to further improve fuel efficiency. [Solution] The system estimates the future required engine torque based on the future accelerator opening angle, which is estimated based on the accelerator opening angle operated by the driver. It also estimates the future maximum engine torque based on the change in boost pressure from the turbocharger and the engine speed. If the future required engine torque remains below the future maximum engine torque for a predetermined period of time, the system limits the required engine torque to the future required engine torque, and reduces the boost pressure if the required boost pressure from the turbocharger is above atmospheric pressure.

Description

Technical Field

[0001] The present disclosure relates to a hybrid vehicle including an engine with a supercharger and a stepped automatic transmission.

Background Art

[0002] Conventionally, as this type of hybrid vehicle, in a hybrid vehicle equipped with an internal combustion engine having a turbocharger and an electric motor, the assist torque of the electric motor is calculated based on the boost pressure difference, which is the difference between the target boost pressure and the measured boost pressure at each time point until reaching the final target torque calculated based on the accelerator opening of the operated accelerator, and the assist torque is applied to the crankshaft of the internal combustion engine (see, for example, Patent Document 1). In this hybrid vehicle, both the reduction of the time in the region with poor combustion efficiency during the transient period and the reduction of the fuel consumption by the assist of the motor generator are achieved by the above control.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a hybrid vehicle including an engine having a supercharger and a stepped automatic transmission with a clutch connected to the output shaft of the engine on the input shaft, the engine speed is determined by the gear stage of the stepped automatic transmission, so it may be difficult to operate the engine in a fuel-efficient region. In particular, when controlling to achieve the target torque based on the accelerator opening, the change in the boost pressure is delayed when shifting from the acceleration state to the constant-speed driving state, and the engine may be operated in a region with poor fuel consumption. The main object of the hybrid vehicle of the present disclosure is to further improve the fuel efficiency.

Means for Solving the Problems

[0005] The hybrid vehicle of this disclosure employs the following means to achieve the main objective described above. The hybrid vehicle of this disclosure comprises an engine having a supercharger, a stepped automatic transmission with a clutch connected to the output shaft of the engine, an electric motor that inputs and outputs power to the input shaft of the automatic transmission, and a control device that controls the engine, the stepped automatic transmission, and the electric motor, wherein the control device estimates the future required engine torque based on the future accelerator opening estimated based on the accelerator opening operated by the driver, and estimates the future maximum engine torque based on the change in boost pressure from the supercharger and the rotational speed of the engine, and when the future required engine torque remains below the future maximum engine torque for a predetermined period of time, it limits the required engine torque to the future required engine torque and reduces the boost pressure when the required boost pressure from the supercharger is equal to or greater than atmospheric pressure.

[0006] The hybrid vehicle control device described herein estimates the future accelerator opening based on the accelerator opening operated by the driver, and estimates the future required engine torque based on the estimated future accelerator opening. It also estimates the future maximum engine torque based on the change in boost pressure from the turbocharger and the engine speed. When the future required engine torque remains below the future maximum engine torque for a predetermined period of time, the device limits the required engine torque to the future required engine torque and reduces the boost pressure if the required boost pressure from the turbocharger is above atmospheric pressure. This prevents the required engine torque from rapidly increasing beyond the future required engine torque and avoids excessive boosting by the turbocharger. As a result, it suppresses the delay in boost pressure changes when transitioning from an acceleration state to a constant speed driving state, allowing the engine to operate in a more fuel-efficient range. This further improves fuel efficiency. [Brief explanation of the drawing]

[0007] [Figure 1]A schematic diagram showing the configuration of the hybrid vehicle 20 according to the embodiment of this disclosure. [Figure 2] A flowchart illustrating an example of engine torque adjustment processing. [Figure 3] This is an explanatory diagram showing an example of the time variation of accelerator opening Acc, required driving force Td*, required engine torque Te*, actual engine torque Te, and motor torque Tm. [Modes for carrying out the invention]

[0008] Next, embodiments of the present disclosure will be described. Figure 1 is a schematic diagram showing the configuration of a hybrid vehicle 20 according to an embodiment of the present disclosure. As shown in the figure, the hybrid vehicle 20 of the embodiment includes an engine 22, a motor 30, an inverter 32, a clutch K0, an automatic transmission 40, a high-voltage battery 60, a low-voltage battery 62, a DC / DC converter 64, and a hybrid electronic control unit (hereinafter referred to as "HVECU") 70.

[0009] The engine 22 is configured as an internal combustion engine that outputs power using fuel such as gasoline. The crankshaft 23 of this engine 22 is connected to the rotating shaft 31 (rotor) of the motor 30 via a clutch K0. This engine 22 is equipped with a turbo-type supercharger (so-called turbocharger) 28 that uses exhaust energy to provide boost.

[0010] The supercharger 28 includes a compressor 28a located in the intake pipe 26 connected to the air cleaner 25, a turbine 28b located in the exhaust pipe 27, a connecting shaft 28c connecting the compressor 28a and the turbine 28b, a bypass pipe 28d attached to the exhaust pipe 27 to bypass the turbine 28b, and a wastegate valve 28e provided in the bypass pipe 28d. In this supercharger 28, by adjusting the opening degree of the wastegate valve 28e, the distribution ratio of the amount of exhaust gas flowing through the bypass pipe 28d and the amount of exhaust gas flowing through the turbine 28b is adjusted, the rotational driving force of the turbine 28b is adjusted, the amount of compressed air from the compressor 28a is adjusted, and the boost pressure (intake pressure) Padd of the engine 22 is adjusted. An intercooler 26a is installed downstream of the compressor 28a in the intake pipe 26 to cool the intake air.

[0011] The engine 22 is controlled by an electronic engine control unit (hereinafter referred to as "engine ECU") 24. The engine ECU 24 is configured as a microcomputer centered on a CPU. The engine ECU 24 receives inputs such as the crank angle θcr from the crank position sensor and the intake air volume Qa from the airflow meter. The engine ECU 24 outputs various control signals for controlling the operation of the engine 22, such as control signals to the throttle valve, fuel injector, spark plug, wastegate valve 28e, etc. The engine ECU 24 calculates the rotational speed Ne of the engine 22 based on the crank angle θcr of the engine 22 from the crank position sensor.

[0012] The crankshaft 23 of the engine 22 is connected to a starter motor 29a for cranking the engine 22 and an alternator 29b for generating electricity using power from the engine 22. The starter motor 29a and alternator 29b are connected to a low-voltage power line 63 along with a low-voltage battery 62.

[0013] The motor 30 is configured as a synchronous generator-motor. The rotating shaft 31 to which the rotor of the motor 30 is fixed is connected to the crankshaft 23 of the engine 22 via a clutch K0 and is also connected to the input shaft 41 of the automatic transmission 45. The inverter 32 is used to drive the motor 30 and is connected to the high-voltage power line 61. The motor 30 is rotationally driven by the switching control of multiple switching elements of the inverter 32 by an electronic motor control unit (hereinafter referred to as "motor ECU") 34.

[0014] The motor ECU 34 is configured as a microcomputer centered around a CPU. The motor ECU 34 receives input such as the rotational position θm of the motor 30's rotor from the rotational position sensor 30a, and the phase currents Iu and Iv of each phase of the motor 30. The motor ECU 34 outputs control signals to the inverter 32. The motor ECU 34 calculates the rotational speed Nm of the motor 30 based on the rotational position θm from the rotational position sensor 30a.

[0015] Clutch K0 is configured, for example, as a hydraulically driven friction clutch, controlled by HVECU70, and connects and disconnects the crankshaft 23 of engine 22 and the rotating shaft 31 of motor 30. Clutch K0 is controlled by HVECU70.

[0016] The automatic transmission 40 includes a torque converter 43 and a 6-speed automatic transmission 45. The torque converter 43 is configured as a general fluid transmission device and transmits power from the input shaft 41 connected to the rotating shaft 31 of the motor 30 to the transmission input shaft 44, which is the input shaft of the automatic transmission 45, with amplified torque, or transmits the torque directly without amplification. The automatic transmission 45 includes the transmission input shaft 44, an output shaft 42 connected to the drive wheel 49 via a differential gear 48, a plurality of planetary gears, and a plurality of hydraulically driven friction engagement elements (clutch, brake). The automatic transmission 45 transmits power between the transmission input shaft 44 and the output shaft 42 by engaging and disengaging the plurality of friction engagement elements to form forward and reverse gears from the 1st to the 6th gear. The clutch K0 and the automatic transmission 45 are supplied with hydraulic fluid from a mechanical oil pump or an electric oil pump, which is regulated by a hydraulic control device (not shown).

[0017] The high-voltage battery 60 is configured as, for example, a lithium-ion secondary battery and is connected to the high-voltage power line 61 together with the inverter 32. The low-voltage battery 62 is configured as, for example, a lead-acid battery and is connected to the low-voltage power line 63 together with the starter motor 29a and the alternator 29b. The DC / DC converter 64 is connected to the high-voltage power line 61 and the low-voltage power line 63 and supplies power from the high-voltage power line 61 to the low-voltage power line 63 with a voltage reduction.

[0018] HVECU70, although not shown in the diagram, is configured as a microcomputer centered around a CPU. HVECU70 receives inputs such as the rotational speed Nin of the input shaft 41 of the automatic transmission 40 from rotational speed sensor 41a, the rotational speed Nmi of the transmission input shaft 44 of the automatic transmission 40 from rotational speed sensor 44a, the rotational speed Nout of the output shaft 42 of the automatic transmission 40 from rotational speed sensor 42a, the voltage Vbh of the high-voltage battery 60, the current Ibh of the high-voltage battery 60, the voltage Vbl of the low-voltage battery 62, the ignition signal from the ignition switch 80, the shift position SP from the shift position sensor 82 which detects the operating position of the shift lever 81, the accelerator opening Acc from the accelerator pedal position sensor 84 which detects the amount of depression of the accelerator pedal 83, the brake pedal position BP from the brake pedal position sensor 86 which detects the amount of depression of the brake pedal 85, and the vehicle speed V from the vehicle speed sensor 87.

[0019] HVECU70 outputs control signals to, for example, the starter motor 29a, the alternator 29b, the clutch K0 and the automatic transmission 40 (hydraulic control device), and the DC / DC converter 64. HVECU70 calculates the rotational speed ratio Gt of the automatic transmission 40 by dividing the rotational speed Nin of the input shaft 41 of the automatic transmission 40, which is received from the rotational speed sensor 41a, by the rotational speed Nout of the output shaft 42 of the automatic transmission 40, which is received from the rotational speed sensor 42a. HVECU70 also communicates with the engine ECU24 and the motor ECU34.

[0020] Next, the operation of the hybrid vehicle 20 of the embodiment configured in this way, and the operation of the engine 22 when the clutch K0 is turned on and the vehicle is running on power from the engine 22 will be described. Figure 2 is a flowchart showing an example of the engine torque adjustment process performed by the engine ECU 24.

[0021] When the engine torque adjustment process is executed, the engine ECU 24 first determines whether the engine 22 is operating (step S100). When it is determined that the engine 22 is not operating (is stopped), this process is unnecessary, so this process ends.

[0022] When it is determined in step S100 that the engine 22 is operating, the future accelerator opening Accf is estimated based on the past accelerator opening Acc and the change amount of the accelerator opening Acc (step S110). The future accelerator opening Accf can be, for example, the accelerator opening Acc from before the first predetermined time, the change amount of the accelerator opening Acc, and the accelerator opening Acc after the second predetermined time as input data, and machine learning is performed so that the accelerator opening Acc after the second predetermined time with respect to the accelerator opening Acc from before the first predetermined time and the change amount of the accelerator opening Acc becomes the learning result, and the accelerator opening Acc after the second predetermined time obtained by applying the accelerator opening Acc from before the first predetermined time and the change amount of the accelerator opening Acc to the learning result can be used as the future accelerator opening Accf.

[0023] Next, the future required driving force Tdf is calculated based on the vehicle speed V and the future accelerator opening Accf (step S120). The future required driving force Tdf may be derived from a map defined such that it increases as the future accelerator opening Accf increases and decreases as the vehicle speed V increases, similar to the required driving force. When the future required driving force Tdf is calculated, the future required engine torque Tef is calculated based on the future required driving force Tdf and the state of charge SOC of the high-voltage battery 60 (step S120). The future required engine torque Tef can be calculated, for example, as the product of the future required driving force Tdf and the gear ratio of the gear stage minus the output torque of the motor 30 obtained so that the state of charge SOC of the high-voltage battery 60 heads towards the target SOC. Then, the maximum engine torque Tefmax that can be achieved in the future is calculated based on the engine speed Ne of the engine 22 and the change amount of the boost pressure ΔPadd (step S140).

[0024] <L Next, it is determined whether the state in which the future required engine torque Tef is less than the future maximum engine torque Tefmax continues for a predetermined time (step S150). This is a process to determine whether an increase in engine torque Te is unnecessary in the future. Note that when the accelerator pedal 83 is pressed or released, the accelerator opening Acc changes and the vehicle speed V also changes, so the future required engine torque Tef and the future maximum engine torque Tefmax also change. For this reason, in order for the state in which the future required engine torque Tef is less than the future maximum engine torque Tefmax continues for a predetermined time, it is required that the accelerator pedal 83 is not pressed or released, or if it is pressed or released, it is only slightly. If it is determined that the state in which the future required engine torque Tef is less than the future maximum engine torque Tefmax has not continued for a predetermined time, it is determined that this process is not yet necessary, and this process is terminated.

[0025] In step S150, if it is determined that the future required engine torque Tef remains below the future maximum engine torque Tefmax for a predetermined period of time, the required engine torque Te*, calculated based on the accelerator opening Acc, is capped at the future required engine torque Tef, similar to how the future required engine torque Tef is calculated based on the future accelerator opening Accf (step S160). This prevents the required engine torque Te* from rapidly exceeding the future required engine torque Tef.

[0026] Next, the required boost pressure Padd* is determined from the required engine torque Te* (step S170), and it is determined whether the required boost pressure Padd* is equal to or greater than atmospheric pressure (step S180). If it is determined that the required boost pressure Padd* is equal to or greater than atmospheric pressure, the wastegate valve 28e is opened to reduce the boost pressure Padd (step S190), and this process is terminated. This reduces the boost pressure and suppresses the delay in the change of boost pressure when transitioning from an acceleration state to a constant speed driving state, allowing the engine 22 to be operated in a more fuel-efficient range.

[0027] Figure 3 is an explanatory diagram showing an example of the time changes of accelerator pedal position Acc, required driving force Td*, required engine torque Te*, actual engine torque Te, and motor torque Tm. At time T1, the accelerator pedal 83 is pressed down, and at time T2, the amount of depression of the accelerator pedal 83 reaches a constant value. As a result, the accelerator pedal position Acc increases, and the required driving force Td* and required engine torque Te* also increase. The actual engine torque Te also increases, but there is a lag compared to the required engine torque Te*. The torque shortage due to the lag in the actual engine torque Te is compensated for by the motor torque Tm. At time T3, the vehicle has accelerated to the target speed, and as the accelerator pedal 83 is released to maintain a constant speed, the accelerator pedal position Acc decreases accordingly, and the required driving force Td* and required engine torque Te* also decrease. On the other hand, the actual engine torque Te increases due to the lag in the change of the boost pressure Pad. In this embodiment, the required engine torque Te* is capped at the future required engine torque Tef, and the boost pressure Pad is lowered, so the actual engine torque Te is suppressed as shown by the dashed line in the column for actual engine torque Te in Figure 3. This allows the engine 22 to be operated in a more fuel-efficient range.

[0028] The above describes the forms for implementing this disclosure using embodiments, but this disclosure is not limited in any way to these embodiments, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0029] This disclosure can be used in industries such as the hybrid vehicle manufacturing industry. [Explanation of Symbols]

[0030] 20 Hybrid vehicle, 22 Engine, 24 Engine ECU, 28 Supercharger, 28e Wastegate valve, 30 Motor, 32 Inverter, 34 Motor ECU, 40 Automatic transmission, 60 High-voltage battery, 70 HVECU.

Claims

[Claim 1] A hybrid vehicle comprising: an engine with a supercharger; a stepped automatic transmission with a clutch connected to the output shaft of the engine; an electric motor that inputs and outputs power to the input shaft of the automatic transmission; and a control device that controls the engine, the stepped automatic transmission, and the electric motor. The control device estimates the future required engine torque based on the future accelerator opening angle estimated based on the accelerator opening angle operated by the driver, and estimates the future maximum engine torque based on the change in boost pressure from the supercharger and the engine speed. When the future required engine torque remains below the future maximum engine torque for a predetermined period of time, the control device limits the required engine torque to the future required engine torque and reduces the boost pressure if the required boost pressure from the supercharger is equal to or greater than atmospheric pressure. A hybrid vehicle characterized by the following features.

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