Hybrid vehicles

Abstract

It outputs sufficient driving force without increasing the input limit of the energy storage device when the driver requires a large amount of torque during starting or low-speed driving. [Solution] The hybrid vehicle includes an engine, a first electric motor, a planetary gear with three rotating elements connected to three shafts: the output shaft of the engine, the rotating shaft of the first electric motor, and the drive shaft connected to the drive wheel, and a second electric motor capable of inputting and outputting power to the drive shaft. When the vehicle speed is below a predetermined vehicle speed and the required torque required for the drive shaft is above a predetermined torque, the engine, the first electric motor, and the second electric motor are controlled so that the required torque is output to the drive shaft while the power required for charging and discharging the energy storage device is limited to a predetermined upper limit power, and the energy storage device is charged and discharged according to the power required for charging and discharging.

Description

Technical Field

[0001] This disclosure relates to a hybrid vehicle.

Background Art

[0002] Conventionally, as this type of hybrid vehicle, when a driver demands a large torque during startup on an uphill slope or during low-speed driving, a low-sensation auxiliary machine that does not cause discomfort to passengers, typified by a cooling system auxiliary machine such as a cooling pump, is forcibly driven (see, for example, Patent Document 1). In this hybrid vehicle, the input limit of the battery is expanded by the amount of excess power set based on the accelerator opening, vehicle speed change, and battery temperature in a state where the low-sensation auxiliary machine is forcibly driven, and the engine and motor are controlled within the range of this expanded input limit, so that the battery is not charged with excessive power without causing discomfort to the passengers and a large torque is output.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described hybrid vehicle, since the input limit of the battery is expanded, it affects the battery life. Therefore, it is desired to output driving force without using the expansion of the battery input limit.

[0005] The main object of the hybrid vehicle of this disclosure is to output sufficient driving force without expanding the input limit of the power storage device when a driver demands a large torque during startup or low-speed driving.

Means for Solving the Problems

[0006] The hybrid vehicle of this disclosure employs the following means to achieve the primary objective described above.

[0007] The hybrid vehicle of this disclosure comprises an engine, a first electric motor, a planetary gear in which three rotating elements are connected to three shafts: the output shaft of the engine, the rotating shaft of the first electric motor, and a drive shaft connected to a drive wheel, a second electric motor capable of inputting and outputting power to the drive shaft, a power storage device that exchanges power with the first electric motor and the second electric motor, and a control device that controls the engine, the first electric motor, and the second electric motor so that, within the range of the allowable input / output limits of the power storage device, a required torque corresponding to the accelerator opening is output to the drive shaft and the power storage device is charged and discharged according to the charge / discharge required power corresponding to the state of the power storage device, wherein the control device controls the vehicle so that when the vehicle speed is below a predetermined vehicle speed and the required torque is above a predetermined torque, the required torque is output to the drive shaft while limiting the charge / discharge required power by a predetermined upper limit power, and the power storage device is charged and discharged according to the charge / discharge required power.

[0008] In the hybrid vehicle of this disclosure, when the vehicle speed is below a predetermined speed and the required torque required for the drive shaft is above a predetermined torque, the engine, the first motor, and the second motor are controlled so that the required torque is output to the drive shaft while the power required for charging and discharging the energy storage device is limited to a predetermined upper limit power, and the energy storage device is charged and discharged according to the power required for charging and discharging. This makes it possible to output sufficient driving force without increasing the input limit of the energy storage device when the driver requests a large torque during starting or low-speed driving. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing the configuration of the hybrid vehicle 20 according to the embodiment of the present disclosure. [Figure 2] This flowchart shows an example of drive control performed by HVECU70. [Figure 3]This is an explanatory diagram illustrating an example of how the target torque Te* and target rotational speed Ne* of the engine 22 are set using the fuel-efficient operation line. [Modes for carrying out the invention]

[0010] Next, embodiments for implementing this disclosure will be described. Figure 1 is a schematic diagram showing the configuration of a hybrid vehicle 20 as an embodiment of this disclosure. As shown in the figure, the hybrid vehicle 20 of the embodiment includes an engine 22, a planetary gear 30, motors MG1 and MG2, inverters 41 and 42, a battery 50, and a hybrid electronic control unit (hereinafter referred to as HVECU) 70.

[0011] The engine 22 is configured as a 6-cylinder internal combustion engine that outputs power through four strokes: intake, compression, expansion (explosive combustion), and exhaust, using a fuel such as gasoline or diesel. The engine 22 is operated and controlled by an electronic control unit (hereinafter referred to as the engine ECU) 24.

[0012] The planetary gear 30 is configured as a single-pinion type planetary gear mechanism. The rotor of the motor MG1 is connected to the sun gear of the planetary gear 30. The drive shaft 36, which is connected to the drive wheels 39a and 39b via a differential gear 38, is connected to the ring gear of the planetary gear 30. The crankshaft 23 of the engine 22 is connected to the carrier of the planetary gear 30.

[0013] Motors MG1 and MG2 are configured, for example, as synchronous generator motors. The rotor of motor MG2 is connected to the drive shaft 36. Inverters 41 and 42 are used to drive motors MG1 and MG2 and are also connected to the battery 50 via the power line 54. Motors MG1 and MG2 are driven by a motor electronic control unit (hereinafter referred to as "motor ECU") 40, which controls the switching of multiple switching elements (not shown) of inverters 41 and 42.

[0014] The battery 50 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery. The battery 50 is managed by a battery electronic control unit (hereinafter referred to as "battery ECU") 52. The battery ECU 52 receives inputs such as the battery voltage Vb from a voltage sensor 51a attached between the terminals of the battery 50, and the battery current Ib from a current sensor 51b attached to the output terminals of the battery 50. The battery ECU 52 calculates the input power Pin and output power Pout of the battery 50 based on the product of the battery voltage Vb and the battery current Ib. The battery ECU 52 also calculates the state of charge (SOC) of the battery 50 based on the integrated value of the battery current Ib. Furthermore, the battery ECU 52 calculates the input limit Win, which is the maximum input power that can be input to the battery 50, and the output limit Wout, which is the maximum output power, based on the battery temperature and other factors.

[0015] The HVECU70 receives inputs such as 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 the accelerator pedal 83 is pressed, the brake pedal position BP from the brake pedal position sensor 86 which detects the amount the brake pedal 85 is pressed, and the vehicle speed V from the vehicle speed sensor 87. The HVECU70 communicates with the engine ECU24, motor ECU40, and battery ECU52.

[0016] Next, the operation of the hybrid vehicle 20 of the embodiment will be described, particularly when the driver requests a large torque during starting or low-speed driving. Figure 2 is a flowchart showing an example of drive control performed by the HVECU 70. This flowchart is executed repeatedly at predetermined intervals.

[0017] When drive control is performed, the HVECU 70 first sets the required torque Td* required for the drive shaft 36 based on the accelerator opening Acc (step S100), and then sets the required power P* required for driving by multiplying the required torque Td* by the vehicle speed V and a conversion factor (step S110). Next, it sets the charge / discharge required power Pb* for charging and discharging the battery 50 based on the charge level SOC of the battery 50 (step S120). In this embodiment, the charge / discharge required power Pb* is set such that the charging power (negative power value) increases as the charge level SOC of the battery 50 decreases when it falls below the control center, and the discharge power (positive power value) increases as the charge level SOC of the battery 50 increases when it exceeds the control center.

[0018] Next, it is determined whether the input limit Win of the battery 50 is less than the threshold Wref, the vehicle speed V is less than the threshold Vref, and the required torque Td* is greater than or equal to the threshold Tref (step S130). Of these determinations, the condition that the vehicle speed V is less than the threshold Vref and the required torque Td* is greater than or equal to the threshold Tref indicates that the driver is requesting a large torque when starting or driving at low speeds. Also, the condition that the input limit Win of the battery 50 is less than the threshold Wref indicates that the battery 50 can receive a certain amount of power.

[0019] In step S130, if it is determined that the input limit Win of the battery 50 is greater than or equal to the threshold Wref, or that the vehicle speed V is greater than or equal to the threshold Vref, or that the required torque Td* is less than the threshold Tref, the lower limit of the charge / discharge required power Pb* is limited by the input limit Win and the upper limit is limited by the output limit Wout, thereby setting a new charge / discharge required power Pb* (step S140).

[0020] When it is determined in step S130 that the input limit Win of the battery 50 is less than the threshold value Wref, the vehicle speed V is less than the threshold value Vref, and the required torque Td* is greater than or equal to the threshold value Tref, the lower limit of the charge / discharge required power Pb* is limited by the input limit Win and the upper limit is limited by the upper limit value Pblim, and a new charge / discharge required power Pb* is set (step S150). The upper limit value Pblim can be, for example, a value of 0 or a value in the vicinity thereof.

[0021] When the charge / discharge required power Pb* is set in this way, the engine required power Pe* as the power required for the vehicle and required for the engine 22 is set by subtracting the charge / discharge required power Pb* from the required power P* required for running (step S160). Then, based on the engine required power Pe* and the operation line, the target torque Te* and the target rotational speed Ne* of the engine 22 are set (step S170). An example of the state of obtaining the target torque Te* and the target rotational speed Ne* of the engine 22 by the engine required power Pe* and the fuel consumption optimal operation line is shown in FIG. 3. Thus, the target torque Te* and the target rotational speed Ne* of the engine 22 can be obtained as the intersection of the fuel consumption optimal operation line and the equal power line of the engine required power Pe*.

[0022] When the target torque Te* and the target rotational speed Ne* of the engine 22 are set, the torque command Tm1* of the motor MG1 is set so that the rotational speed Ne of the engine 22 becomes the target rotational speed Ne* (step S180), and the torque command Tm2* of the motor MG2 is set so that the required torque Td* is output to the drive 36 (step S190). The torque command Tm1* of the motor MG1 can be calculated by the relational expression of feedback control having a proportional term and an integral term so that the difference between the rotational speed Ne of the engine 22 and the target rotational speed Ne* becomes small. The torque command Tm2* of the motor MG2 can be calculated by multiplying the torque (target torque Te*) output from the engine 22 by the gear ratio Gr of the planetary gear 30 from the required torque Td*.

[0023] When the target torque Te*, target rotational speed Ne*, and torque commands Tm1*, Tm2* of the engine 22 are set in this way, the target torque Te* and target rotational speed Ne* of the engine 22 are transmitted to the engine ECU 24, and the torque commands Tm1*, Tm2* are transmitted to the motor ECU 40 (step S200), and the drive control is terminated. The engine ECU 24 that has received the target torque Te* and target rotational speed Ne* performs intake air amount control, fuel injection control, ignition control, etc. so that the engine 22 operates at the operating point determined by the target torque Te* and target rotational speed Ne*. The motor ECU 40 that has received the torque commands Tm1*, Tm2* performs switching control of the switching elements of the inverter 41 so that the torque corresponding to the torque command Tm1* is output from the motor MG1, and also performs switching control of the switching elements of the inverter 42 so that the torque corresponding to the torque command Tm2* is output from the motor MG2.

[0024] In the hybrid vehicle 20 of the embodiment described above, when the conditions where the driver requests a large torque during starting or low-speed driving (the condition that the vehicle speed V is less than the threshold value Vref and the required torque Td* is greater than or equal to the threshold value Tref) are satisfied and the condition where the battery 50 can input a certain amount of power (the condition that the input limit Win of the battery 50 is less than the threshold value Wref) is satisfied, the lower limit of the charge / discharge required power Pb* is limited by the input limit Win and the upper limit is limited by the upper limit value Pblim to set a new charge / discharge required power Pb*, and the target torque Te*, target rotational speed Ne* of the engine 22 and the torque commands Tm1*, Tm2* of the motors MG1, MG2 are set using this charge / discharge required power Pb* and the required power P*. Thereby, sufficient driving force can be output without expanding the input limit Win of the battery 50 when the driver requests a large torque during starting or low-speed driving.

[0025] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be explained. In the embodiment, engine 22 corresponds to "engine", motor MG1 corresponds to "first electric motor", planetary gear 30 corresponds to "planetary gear", motor MG2 corresponds to "second electric motor", battery 50 corresponds to "energy storage device", and HVECU 70, engine ECU 24, motor ECU 40, and battery ECU 52 correspond to "control device".

[0026] Furthermore, the correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem is merely an example to specifically explain the form in which the embodiment carries out the invention described in the section on means for solving the problem, and does not limit the elements of the invention described in the section on means for solving the problem. In other words, the interpretation of the invention described in the section on means for solving the problem should be based on the description in that section, and the embodiment is merely one specific example of the invention described in the section on means for solving the problem.

[0027] While embodiments of this disclosure have been described above, 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]

[0028] This disclosure can be used in industries such as the hybrid vehicle manufacturing industry. [Explanation of symbols]

[0029] 20 Hybrid vehicle, 22 Engine, 30 Planetary gear, 50 Battery, 70 HVECU, 82 Shift position sensor, 84 Accelerator pedal position sensor, 86 Brake pedal position sensor, MG1, MG2 Motor.

Claims

[Claim 1] The engine and The first electric motor and, A planetary gear in which three rotating elements are connected to the output shaft of the engine, the rotating shaft of the first electric motor, and the drive shaft connected to the drive wheel, A second electric motor capable of inputting and outputting power to the aforementioned drive shaft, A power storage device that exchanges power with the first motor and the second motor, A control device that controls the engine, the first motor, and the second motor so that, within the allowable input / output limits of the energy storage device, a required torque corresponding to the accelerator opening is output to the drive shaft, and the energy storage device is charged and discharged according to the charge / discharge required power corresponding to the state of the energy storage device. A hybrid vehicle equipped with, The control device, when the vehicle speed is below a predetermined vehicle speed and the requested torque is above a predetermined torque, controls the system so that the requested torque is output to the drive shaft while limiting the requested power for charging and discharging by a predetermined upper limit power, and so that the energy storage device is charged and discharged by the requested power for charging and discharging. A hybrid vehicle characterized by the following features.

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