Hybrid vehicle

Abstract

To provide a hybrid vehicle which makes, when allowable input power of a power storage device is small, requested brake force apply to a vehicle and start an engine to activate an engine brake.SOLUTION: A hybrid vehicle comprises, to activate an engine brake when allowable input power of a power storage device is less than a specified power in accelerator-off operation at a state where an engine is stopped, the steps of: preventing electric power inputted into the power storage device from exceeding the allowable input power through applying brake force of a brake device to the vehicle when a first electric motor cranks the engine to start the engine; and controlling the first electric motor, the second electric motor and the brake device to apply requested brake force to the vehicle.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to hybrid vehicles. [Background technology]

[0002] Conventionally, a hybrid vehicle of this type has been proposed in which one of a plurality of patterns relating to control of engine required power is selected and the engine required power is controlled in accordance with that pattern (see, for example, Patent Document 1). In this hybrid vehicle, the plurality of patterns include a first pattern in which a required value is generated when the engine begins to start, a second pattern in which a required value is not generated during engine start but is generated after the engine has started, and a third pattern in which a required value is not generated either during engine start or after the engine has started. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-042216 Summary of the Invention [Problem to be solved by the invention]

[0004] In a hybrid vehicle equipped with a planetary gear mechanism in which three axes—the rotating shaft of a first electric motor, the output shaft of the engine, and the drive shaft connected to the drive wheels—are connected in that order on a nomographic diagram, the required braking force is applied to the vehicle by regeneratively controlling the second electric motor, which inputs and outputs power to the drive shaft, when the accelerator is released, and the regenerative power generated by regeneratively controlling the second electric motor is stored in a battery or other storage device. In recent hybrid vehicles, some vehicles keep the storage device fully charged at home or elsewhere, drive on electric power as much as possible, and start the engine once the storage rate in the storage device has decreased. In such hybrid vehicles, when traveling down a long slope with the battery relatively nearly fully charged, if the storage device's allowable input power is low and the regenerative power of the second electric motor cannot be absorbed, part of the required braking force may be supplied by engine braking. At this time, the engine needs to be started, but when the engine is started, the first motor needs to be controlled regeneratively, and when the regenerative power of the first motor is taken into account in addition to the regenerative power of the second motor, the allowable input power of the storage device is exceeded, making it necessary to limit the regenerative control by the second motor, and making it difficult to apply the required braking force to the vehicle.

[0005] The hybrid vehicle of the present disclosure has a main purpose of starting the engine and applying engine braking while applying a required braking force to the vehicle when the allowable input power of the power storage device is low. [Means for solving the problem]

[0006] The hybrid vehicle of the present disclosure employs the following measures to achieve the above-mentioned main object.

[0007] The hybrid vehicle of the present disclosure includes an engine, a first electric motor, a planetary gear mechanism in which three shafts, namely, a rotary shaft of the first electric motor, an output shaft of the engine, and a drive shaft connected to drive wheels, are connected to three rotary elements in this order in a nomographic diagram, a second electric motor capable of inputting and outputting power to the drive shaft, an electricity storage device that exchanges electric power with the first electric motor and the second electric motor, a brake device capable of applying braking force to the vehicle, and a front brake control system that controls the engine, the first electric motor, the second electric motor, and the brake device and causes the second electric motor to apply a required braking force to the vehicle by regenerative control when the accelerator is released. and a control device that controls the second electric motor, wherein when the engine is cranked and started by the first electric motor to apply engine braking when the allowable input power of the power storage device is less than a predetermined power when the accelerator is released with the engine stopped, the control device controls the first electric motor, the second electric motor, and the brake device so that the braking force of the brake device is applied to the vehicle so that the power input to the power storage device does not exceed the allowable input power and so that the required braking force is applied to the vehicle.

[0008] The hybrid vehicle disclosed herein controls the second electric motor so that a required braking force is applied to the vehicle through regenerative control of the second electric motor when the accelerator is released. Then, when the engine is stopped and the accelerator is released and the allowable input power of the power storage device is less than a predetermined power, the hybrid vehicle controls the first electric motor, the second electric motor, and the brake device so that braking force is applied to the vehicle by the brake device so that the power input to the power storage device does not exceed the allowable input power and the required braking force is applied to the vehicle. That is, by cranking the engine using the first electric motor, braking force corresponding to the regenerative power generated by the first electric motor is applied to the vehicle by the brake device. This allows the engine to be started while the required braking force is applied to the vehicle when the allowable input power of the power storage device is low, thereby enabling engine braking to be applied. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing an outline of the configuration of a hybrid vehicle 20 according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is an explanatory diagram showing an example of a collinear diagram of the planetary gear 30. [Figure 3] 4 is a flowchart showing an example of an engine start process when the engine is started with the accelerator released. [Figure 4] 3 is an explanatory diagram showing an example of the power balance before the engine 22 is started and at the time of starting the engine 22 in the embodiment and the comparative example. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, a mode (embodiment) for carrying out the present disclosure will be described. Fig. 1 is a configuration diagram showing an outline of the configuration of a hybrid vehicle 20 equipped with an on-vehicle control device according to one embodiment of the present 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, a charger 60, and a hybrid electronic control unit (hereinafter referred to as "HVECU") 70.

[0011] The engine 22 is configured as an internal combustion engine that outputs power using gasoline, diesel, or the like as fuel. The operation of the engine 22 is controlled by an engine electronic control unit (hereinafter referred to as "engine ECU") 24. Signals from various sensors required for controlling the operation of the engine 22 are input to the engine ECU 24, and various control signals for controlling the operation of the engine 22 are output from the engine ECU 24.

[0012] The planetary gear 30 is configured as a single-pinion planetary gear mechanism. A rotor of a motor MG1 is connected to a sun gear of the planetary gear 30. A drive shaft 36, which is coupled to drive wheels 38a, 38b via a differential gear 37, is connected to a ring gear of the planetary gear 30. A crankshaft 26 of the engine 22 is connected to a carrier of the planetary gear 30 via a damper 28.

[0013] The motor MG1 is configured as, for example, a synchronous generator motor, and as described above, its rotor is connected to the sun gear of the planetary gear 30. The motor MG2 is configured as, for example, a synchronous generator motor, and its rotor is connected to the drive shaft 36. The inverters 41 and 42 are connected to a battery 50 via a power line 54. The motors MG1 and MG2 are driven and rotated by a motor electronic control unit (hereinafter referred to as "motor ECU") 40, which controls the switching of multiple switching elements (not shown) of the inverters 41 and 42. The motor ECU 40 receives inputs from various sensors required for driving and controlling the motors MG1 and MG2, such as rotational positions θm1 and θm2 from rotational position detection sensors 43 and 44 that detect the rotational positions of the rotors of the motors MG1 and MG2, and phase currents from current sensors that detect currents flowing through each phase of the motors MG1 and MG2. The motor ECU 40 outputs switching control signals and the like to multiple switching elements (not shown) of the 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. As described above, the battery 50 is connected to the inverters 41, 42 via the power line 54. 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 a battery voltage Vb from a voltage sensor 51a installed between the terminals of the battery 50, a battery current Ib from a current sensor 51b attached to the output terminal of the battery 50, and a battery temperature Tb from a temperature sensor 51c attached to the battery 50. The battery ECU 52 calculates a power storage ratio SOC based on an integrated value of the battery current Ib from the current sensor 51b. The power storage ratio SOC is the ratio of the amount of power that can be discharged from the battery 50 to the total capacity of the battery 50. The battery ECU 52 also sets an input limit Win and an output limit Wout as allowable input power and allowable output power that can be input to and output from the battery 50 based on the power storage ratio SOC and battery temperature Tb of the battery 50. The input limit Win is set to decrease as the storage rate SOC of the battery 50 increases (closer to full charge), and the output limit Wout is set to decrease as the storage rate SOC of the battery 50 decreases (closer to full discharge).

[0015] The charger 60 is connected to the power line 54, and is configured to be able to charge the battery 50 using power from the external power source 69 when the power plug 61 is connected to an external power source 69 such as a household power source. The charger 60 includes an AC / DC converter and a DC / DC converter, not shown. When the power plug 61 is connected to the external power source 69, the charger 60 charges the battery 50 using power from the external power source 69 by controlling the AC / DC converter and the DC / DC converter by the HVECU 70.

[0016] Although not shown, the HVECU 70 is configured as a microprocessor centered around a CPU. The HVECU 70 receives, for example, an ignition signal from an ignition switch 80, a shift position SP from a shift position sensor 82 that detects the operating position of a shift lever 81, and an accelerator opening Acc from an accelerator pedal position sensor 84 that detects the depression amount of an accelerator pedal 83. The HVECU 70 also receives a vehicle speed V from a vehicle speed sensor 88 and a connection signal SWC from a connection switch 62 that is attached to a power plug 61 and determines whether the power plug 61 is connected to an external power source 69. The HVECU 70 outputs a control signal to the charger 60, etc. The HVECU 70 communicates with the engine ECU 24, the motor ECU 40, and the battery ECU 52.

[0017] The brake device 90 is configured as a well-known hydraulically driven brake device, and is configured to be able to apply braking force resulting from the brake depression force applied by depressing a brake pedal 85 and braking force resulting from hydraulic pressure adjustment to the drive wheels 38a, 38b and driven wheels. The brake device 90 is controlled by a brake electronic control unit (hereinafter referred to as "brake ECU") 92. The brake ECU 92 receives a brake pedal position BP from a brake pedal position sensor 86 that detects the depression amount of the brake pedal 85. The brake ECU 92 controls the brake device 90, specifically, controls the braking force resulting from the brake depression force applied by the brake device 90 and braking force resulting from hydraulic pressure adjustment. The brake ECU 92 communicates with the HVECU 70 via a communication port.

[0018] In the hybrid vehicle 20 of this embodiment configured as described above, the battery 50 is fully charged at home or elsewhere. After the system is started, the vehicle runs in EV mode, essentially running on power from the motor MG2 without operating the engine 22, until the state of charge (SOC) of the battery 50 falls below the threshold value Sref. When traveling downhill, the hybrid vehicle 20 of this embodiment applies the required braking force when the accelerator is released to the vehicle by regeneratively controlling the motor MG2, and charges the battery 50 with the regenerative power of the motor MG2. When the battery 50 is nearly fully charged, the input limit Win of the battery 50 decreases, making it impossible for the battery 50 to receive the regenerative power of the motor MG2. Therefore, the required braking power is partially supplied by engine braking. At this time, the engine 22 needs to be started. Starting the engine 22 requires cranking the engine 22 by the motor MG1. However, regenerative power is generated by the motor MG1, and this power must be received by the battery 50. This prevents the motor MG2 from receiving the regenerative power. An example of a nomogram of the planetary gear 30 in this case is shown in FIG. 3. In the diagram, the S-axis represents the rotation speed Ns of the sun gear of the planetary gear 30, which is the rotation speed Nm1 of the motor MG1; the C-axis represents the rotation speed Nc of the carrier 34, which is the rotation speed Ne of the engine 22; and the R-axis represents the rotation speed Nr of the ring gear (drive shaft 36) of the planetary gear 30, which is the rotation speed Nm2 of the motor MG2. In the diagram, torque Tm1 is the torque (regenerative torque) of cranking the engine 22 by the motor MG1; torque (-Tm1 / ρ) is the torque output from the motor MG1 and acting on the drive shaft 36 via the planetary gear 30; and torque Tm2 is the torque (regenerative torque) of the motor MG2. In this case, as shown in the diagram, in order to receive the regenerative power due to the torque Tm1 of the motor MG1 into the battery 50, it is necessary to reduce the regenerative power due to the torque Tm2 of the motor MG2. Based on this, in the hybrid vehicle 20 of this embodiment, the engine start process illustrated in FIG. 3 is executed to start the engine 22 and apply a required braking force to the vehicle so that the input limit Win of the battery 50 is not exceeded.

[0019] In the engine start process, first, it is determined whether or not it is necessary to start the engine 22 (step S100). This determination can be made by determining whether or not the sum of the power required to apply a required braking force to the vehicle when the accelerator is released (required braking power Pd*) and the power consumption Wh of accessories, etc. is less than the input limit Win of the battery 50. That is, when the sum of the required braking power Pd* and the power consumption Wh is less than the input limit Win, it is determined that the battery 50 cannot accept the power equal to the sum of the required braking power Pd* and the power consumption Wh, and it is determined that it is necessary to start the engine 22. When it is determined that it is not necessary to start the engine 22, this process is unnecessary, and therefore this process is terminated.

[0020] When it is determined in step S100 that it is necessary to start the engine 22, cranking of the engine 22 by the motor MG1 is started (step S110), and power equivalent to the regenerative power of the motor MG1 (engine starting power) is output from the brake device 90 as braking power (braking force x vehicle speed x conversion coefficient) by cranking the engine 22 by the motor MG1 (step S120).

[0021] Then, after waiting for the start of the engine 22 to be completed (step S130), the engine brake is started (step S140), and the output of braking power from the brake device 90 is stopped (step S150), and this process is terminated.

[0022] FIG. 4 is an explanatory diagram showing an example of the power balance before and during the start of the engine 22 in the embodiment and the comparative example. The comparative example is a case where no braking power is output from the brake device 90 when the engine 22 is cranked. As shown in FIG. 4, before the engine 22 is started, the sum of the regenerative power of the motor MG2 and the consumed power Wh balances with the input limit Win of the battery 50. In the comparative example, because there is no braking power from the brake device 90, the sum of the regenerative power of the motor MG1 and the regenerative power of the motor MG2 and the consumed power Wh exceeds the input limit Win of the battery 50. On the other hand, in the embodiment, because braking power equivalent to the regenerative power of the motor MG1 is output from the brake device 90, the sum of the regenerative power of the motor MG1 and the regenerative power of the motor MG2 and the consumed power Wh balances with the input limit Win of the battery 50.

[0023] In the hybrid vehicle 20 of the embodiment described above, when the sum of the required braking power Pd* and the power consumption Wh is less than the input limit Win with the engine 22 stopped and the accelerator released, it is determined that the engine 22 needs to be started to apply engine braking, and power equivalent to the regenerative power of the motor MG1 is output as braking power from the brake device 90 by cranking the engine 22 using the motor MG1. As a result, when the input limit Win of the battery 50 is small, the engine 22 can be started and engine braking can be applied while the required braking force is applied to the vehicle.

[0024] The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problem" section will be described below. In the embodiment, the engine 22 corresponds to the "engine," the motor MG1 corresponds to the "first electric motor," the planetary gear 30 corresponds to the "planetary gear mechanism," the motor MG2 corresponds to the "second electric motor," the battery 50 corresponds to the "electricity storage device," the brake device 90 corresponds to the "brake device," and the engine ECU 24, the motor ECU 40, the battery ECU 52, the brake ECU 92, the HVECU 70, etc. correspond to the "control device."

[0025] The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, since the embodiments are examples for specifically explaining the mode for implementing the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely specific examples of the invention described in the "Means for Solving the Problem" section.

[0026] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to these embodiments, and it goes without saying that the present disclosure can be embodied in various forms without departing from the spirit of the present disclosure. [Industrial Applicability]

[0027] The present disclosure is applicable to the hybrid vehicle manufacturing industry and the like. [Explanation of symbols]

[0028] 20 hybrid vehicle, 22 engine, 24 engine electronic control unit (engine ECU), 40 motor electronic control unit (motor ECU), 41, 42 inverter, 50 battery, 52 battery electronic control unit (battery ECU 52), 60 charger, 70 hybrid electronic control unit (HVECU), 90 brake device, 92 brake electronic control unit (brake ECU), MG1, MG2 motor.

Claims

[Claim 1] a hybrid vehicle comprising: an engine; a first electric motor; a planetary gear mechanism in which three shafts, namely, a rotary shaft of the first electric motor, an output shaft of the engine, and a drive shaft connected to drive wheels, are connected to three rotary elements in this order in a nomographic diagram; a second electric motor capable of inputting and outputting power to the drive shaft; an electricity storage device that exchanges electric power with the first electric motor and the second electric motor; a brake device capable of applying braking force to a vehicle; and a control device that controls the engine, the first electric motor, the second electric motor, and the brake device, and also controls the second electric motor so that a required braking force is applied to the vehicle by regenerative control when an accelerator is released, a control device that, when cranking and starting the engine using the first electric motor to apply engine braking when the allowable input power of the power storage device is less than a predetermined power when the accelerator is released with the engine stopped, controls the first electric motor, the second electric motor, and the brake device so that a braking force from the brake device is applied to the vehicle so that the power input to the power storage device does not exceed the allowable input power and so that the required braking force is applied to the vehicle.

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