Hybrid electric vehicle

Abstract

The invention provides a hybrid electric vehicle. The hybrid electric vehicle is provided with a control device that executes travel control and battery control, the battery control including: a first discharge control that sets the lower limit voltage of the battery to a first lower limit value and sets the dischargeable power of the battery to a first upper limit value when not being warmed up by the catalyst device, and a second discharge control that sets the dischargeable power of the battery to a second upper limit value when not being warmed up by the catalyst device; and a second discharge control for setting the lower limit voltage of the battery to a second lower limit value that is smaller than the first lower limit value and setting the battery dischargeable power to a second upper limit value that is larger than the first upper limit value when the catalyst device is being warmed up. The travel control includes a transient control that outputs, from the battery, electric power obtained by adding a temporary increase amount to battery dischargeable electric power.

Description

Technical Field

[0001] The present invention relates to hybrid electric vehicles. Background Art

[0002] Japanese Patent Application Laid-Open No. 2010-042700 discloses a hybrid electric vehicle equipped with a catalyst device for purifying engine exhaust. In the configuration described in Japanese Patent Application Laid-Open No. 2010-042700, when warming up the catalyst device is necessary, the engine is driven at idle speed when the battery output power meets the required power, and the catalyst device is warmed up using exhaust heat. Summary of the Invention

[0003] In the configuration described in Japanese Patent Application Laid-Open No. 2010-042700, even if the catalyst device needs to be warmed up, it is not warmed up if the required power exceeds the battery output limit. Therefore, if the catalyst device needs to be warmed up, it is considered possible to relax the battery output limit.

[0004] However, when the battery output limit is relaxed, the voltage drop increases as the output power increases. Therefore, when a higher-than-expected power level is used during catalyst device preheating, the voltage drop also increases. This can cause the battery voltage to reach the lower voltage limit prematurely and potentially lead to a voltage break. This is undesirable from a component protection perspective. To achieve component protection, the motor output torque is limited when the battery voltage reaches the lower voltage limit. In this case, the driving force is limited prematurely, resulting in shock, hysteresis, and other issues.

[0005] The present invention provides a hybrid electric vehicle capable of suppressing a decrease in drivability while achieving component protection when increasing the output power of a battery during warm-up of a catalyst device.

[0006] The hybrid electric vehicle of the present invention comprises:

[0007] internal combustion engine;

[0008] electric motor;

[0009] a battery storing electric power for supplying to the electric motor;

[0010] a catalyst device for purifying exhaust gas discharged from the internal combustion engine; and

[0011] a control device that performs driving control for controlling the internal combustion engine and the electric motor and performs battery control for managing the battery,

[0012] The battery control includes:

[0013] a first discharge control for controlling discharge of the battery in a first setting state in which the lower limit voltage of the battery is set to a first lower limit value and the dischargeable power of the battery is set to a first upper limit value when the catalyst device is not being warmed up; and

[0014] a second discharge control for controlling discharge of the battery in a second setting state in which the lower limit voltage of the battery is set to a second lower limit value smaller than the first lower limit value and the dischargeable power of the battery is set to a second upper limit value larger than the first upper limit value, while the catalyst device is being warmed up;

[0015] The driving control includes:

[0016] setting control for setting an increase amount when temporarily increasing the output power of the battery; and

[0017] Transition control, outputting from the battery the power obtained by adding the increased amount to the dischargeable power of the battery to cause the hybrid electric vehicle to travel,

[0018] The control device:

[0019] During execution of the first discharge control, the increase amount is set to a first increase amount.

[0020] During execution of the second discharge control, the increase amount is set to a second increase amount that is smaller than the first increase amount.

[0021] When the transition control is executed during execution of the second discharge control, electric power obtained by adding the second increase amount to the second upper limit value is output from the battery.

[0022] In the present invention, when the output power of the battery is increased during warm-up of the catalyst device, it is possible to suppress a decrease in drivability while achieving component protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0024] Figure 1 FIG. 1 is a diagram schematically showing a hybrid electric vehicle in an embodiment.

[0025] Figure 2 This is a diagram for explaining the dischargeable power and the lower limit voltage of the battery in a steady state.

[0026] Figure 3 It is a diagram for explaining transient dischargeable electric power.

[0027] Figure 4 This is a diagram for explaining a state in which the output power of the battery is temporarily increased during catalyst warm-up.

[0028] Figure 5 It is a flowchart showing the flow of setting processing.

[0029] Figure 6 It is a diagram for explaining control in a comparative example.

[0030] Figure 7 It is a diagram for explaining control in another comparative example. DETAILED DESCRIPTION

[0031] Hereinafter, a hybrid electric vehicle according to an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiment described below.

[0032] Figure 1 A hybrid electric vehicle 1 includes an engine (ENG) 2 , a first motor (MG1) 3 , a second motor (MG2) 4 , a power split device 5 , a PCU 6 , a battery 7 , and a control device 20 .

[0033] The hybrid electric vehicle 1 includes an engine 2, a first motor 3, and a second motor 4 as power sources. The engine 2 is an internal combustion engine such as a gasoline engine. The first motor 3 and the second motor 4 are both electric generators that function as both a motor and a generator, and are composed of electric motors such as synchronous motors (three-phase AC motors). The first motor 3 mainly functions as a generator. The second motor 4 mainly functions as a motor. The first motor 3 and the second motor 4 are electrically connected to the PCU 6. The first motor 3 is electrically connected to the second motor 4 via the PCU 6. The electric power generated by the first motor 3 is supplied to the second motor 4 via the PCU 6, and this electric power can be used to output torque from the second motor 4.

[0034] The PCU 6 includes a first inverter that drives the first motor 3 and a second inverter that drives the second motor 4. The PCU 6 is electrically connected to the battery 7. Each motor 3 and 4 is electrically connected to the battery 7 via the PCU 6. The first motor 3 is electrically connected to the battery 7 via the first inverter. The second motor 4 is electrically connected to the battery 7 via the second inverter. The battery 7 is a secondary battery that stores electric power to be supplied to each motor 3 and 4. The battery 7 can store electric power generated by each motor 3 and 4. The battery 7 is composed of a battery pack having a plurality of battery modules formed by stacking a plurality of battery cells.

[0035] The power split mechanism 5 splits the power output from the engine 2 to the first motor 3 and the drive shaft 11. The power split mechanism 5 is composed of a single-pinion planetary gear mechanism. The power split mechanism 5 includes a sun gear 5S, a ring gear 5R, and a planetary carrier 5C. The planetary carrier 5C holds a pinion gear that meshes with the sun gear 5S and the ring gear 5R in a rotatable and revolvable manner. The first motor 3 is connected to the sun gear 5S. The engine 2 is connected to the planetary carrier 5C. The ring gear 5R is the output element of the power split mechanism 5 and outputs power to the drive shaft 11. The output gear 8 is connected to the ring gear 5R. The ring gear 6R and the output gear 8 rotate integrally. The output gear 8 is connected to the differential mechanism 10 via the countershaft gear mechanism 9. The countershaft gear mechanism 9 includes a countershaft driven gear, a countershaft drive gear, and a countershaft. The differential mechanism 10 includes a differential gear. The differential mechanism 10 is connected to the drive wheels 12 via the drive shaft 11.

[0036] In the hybrid electric vehicle 1, the torque output by the second motor 4 can be added to the torque transmitted from the power split mechanism 5 to the drive shaft 11. The second motor 4 is connected to the countershaft gear mechanism 9 via the reduction gear 13. The engine 2, the first motor 3, and the second motor 4 are all connected to the drive shaft 11 via the countershaft gear mechanism 9 and the differential mechanism 10. The hybrid electric vehicle 1 can implement an HV driving mode in which the vehicle is driven by the torque output by the engine 2, and an EV driving mode in which the vehicle is driven only by the torque output by the second motor 4. In addition, in the HV driving mode, the torque output by the second motor 4 can be added.

[0037] The control device 20 is an electronic control device that controls the hybrid electric vehicle 1. The control device 20 is configured as a microcomputer including a CPU, RAM, ROM, and an input / output interface. The control device 20 performs signal processing according to a program pre-stored in the ROM. Signals from various sensors mounted on the hybrid electric vehicle 1 are input to the control device 20. For example, a vehicle speed signal from a vehicle speed sensor that detects vehicle speed, an accelerator opening signal from an accelerator opening sensor that detects the amount of accelerator pedal operation, and the like are input to the control device 20. Furthermore, for example, a temperature signal from a temperature sensor that detects the temperature of the battery 7, a current signal from a current sensor that detects the input and output currents of the battery 7, and a voltage signal from a voltage sensor that detects the voltage of the battery 7 are input to the control device 20. The control device 20 performs various controls based on the signals input from the various sensors. At this time, the control device 20 performs calculations using the input data and pre-stored data, and outputs the calculation results as command signals.

[0038] The control device 20 is composed of a hybrid electronic control unit (HV-ECU), a motor electronic control unit (MG-ECU), and a battery electronic control unit (battery ECU). The control device 20 performs driving control for the engine 2 and each motor 3 and 4, and performs battery control for managing the battery 7. The HV-ECU of the control device 20 outputs command signals to the engine 2, electrically controlling its output, starting, and stopping. The control device 20 electrically controls fuel injection, ignition timing, and other aspects of the engine 2. The MG-ECU of the control device 20 outputs command signals to the PCU 6, controlling the motor torque of each motor 3 and 4. The battery ECU of the control device 20 manages and monitors the battery 7.

[0039] The control device 20 performs discharge control to control the discharge of the battery 7 as a battery control. The control device 20 sets the lower limit voltage Vmin of the battery 7 and the dischargeable power Wout of the battery 7. The lower limit voltage Vmin is set to achieve component protection. The dischargeable power Wout is the maximum power that can be output, which limits the output power of the battery 7. The dischargeable power Wout indicates the output limit of the battery 7. The control device 20 calculates the dischargeable power Wout based on the state of charge (SOC) of the battery 7 and the temperature of the battery 7. The control device 20 calculates the SOC based on the input and output currents of the battery 7, the battery voltage, and other factors.

[0040] The control device 20 calculates the required driving force based on the accelerator pedal position and vehicle speed for driving control. The control device 20 also calculates the required power based on the required driving force and vehicle speed. The control device 20 sets the target speed and target torque of the engine 2 based on the required power.

[0041] Hybrid electric vehicle 1 includes a catalyst device 14 for purifying exhaust gas from engine 2. Catalytic device 14 is installed in the exhaust pipe of engine 2. Hybrid electric vehicle 1 can preheat catalyst device 14 using exhaust heat from engine 2. When preheating catalyst device 14 is necessary, control device 20 controls engine 2 to idle, allowing exhaust heat to preheat catalyst device 14. Idle refers to an operating state in which the engine 2's speed is controlled to the idle speed and the engine 2 rotates without outputting torque.

[0042] Hybrid electric vehicle 1 is configured to anticipate the need to increase the output power of battery 7 during warm-up of catalyst device 14, assuming that exhaust gas restriction is strengthened. Simply increasing the output power of battery 7 involves increasing the number of cells within battery 7. However, increasing the number of cells increases the size and weight of battery 7. Therefore, hybrid electric vehicle 1 maintains the number of cells within battery 7 and utilizes methods to increase the output power of battery 7.

[0043] The control device 20 executes Figure 2 The battery control and Figure 3 As shown in the driving control. Figure 2 As shown, the control device 20 sets the lower limit voltage Vmin of the battery 7 to a first lower limit value Vmin1 and the dischargeable power Wout_s in the steady state to a first upper limit value Wout_s1. The first upper limit value Wout_s1 is the power output time for which the battery 7 continuously discharges at the dischargeable power Wout until the voltage of the battery 7 reaches the first lower limit value Vmin1, which is a first duration. The first duration is 10 seconds. In other words, the power that reaches the lower limit voltage Vmin during the 10-second discharge at the dischargeable power Wout is the first upper limit value Wout_s1. The state in which the lower limit voltage Vmin is set to the first lower limit value Vmin1 and the dischargeable power Wout_s in the steady state is set to the first upper limit value Wout_s1 is the first setting state.

[0044] like Figure 3 As shown, control device 20 can cause battery 7 to output transient dischargeable power Wout_t, which is a temporary increase ΔW added to steady-state dischargeable power Wout_s. Transitional dischargeable power Wout_t is the power that, when discharged continuously at this dischargeable power Wout_t, allows the battery 7 voltage to reach lower limit voltage Vmin, resulting in a continuous output time of one second.

[0045] As an example of control, consider Figure 6The control of the comparative example shown. The control of the comparative example includes battery control and driving control. The battery control of the comparative example includes control to increase the dischargeable power W1 in the steady state when the catalyst is being warmed up compared to when the catalyst does not need to be warmed up. The definition of the dischargeable power W1 is the same as the definition of the first upper limit value Wout_s1. The dischargeable power W1 is the power required for the battery voltage to reach the lower limit voltage V1 for 10 seconds when the battery continuously discharges at the dischargeable power W1. In the battery control of the comparative example, the dischargeable power W1 in the steady state is set to different values ​​when the catalyst does not need to be warmed up and when the catalyst is being warmed up. The battery control of the comparative example includes control to increase the dischargeable power W1 in the steady state by lowering the lower limit voltage V1 of the battery when the catalyst is being warmed up. The lower limit voltage V1 is lower when the catalyst is being warmed up than when the catalyst is not being warmed up.

[0046] like Figure 6 As shown, the driving control of the comparative example includes transient control that temporarily increases the battery's output power. Transient control adds a preset increase ΔW to the steady-state dischargeable power W1. When transient control is executed during catalyst warm-up, the battery outputs transient dischargeable power W2, which is the sum of the increase ΔW temporarily added by driving control and the steady-state dischargeable power W1 increased by battery control.

[0047] Moreover, according to Figure 6 In the control of the comparative example shown, in order to increase the output power during catalyst warm-up, the following is considered: Figure 7 The other comparative examples shown are controls. Figure 7 In the other comparative example shown, control is performed to further increase the output power of the battery during catalyst warm-up. During catalyst warm-up, the definition of the dischargeable power W11 in the steady state is changed. The dischargeable power W11 in the steady state during catalyst warm-up is not the power at which the battery voltage reaches the lower limit voltage V11 due to 10 seconds of power use. In contrast, the dischargeable power W11 in the steady state during catalyst warm-up is the power at which the battery voltage reaches the lower limit voltage V11 due to 5 seconds of power use. In this case, the temporarily increased increase amount ΔW is unchanged. Figure 6 In the control shown, during catalyst warm-up, the transient dischargeable power W12 obtained by temporarily adding the increase ΔW to the steady-state dischargeable power W11 is larger than expected. Therefore, there is a possibility that the battery voltage may exceed the lower limit voltage V11.

[0048] Therefore, the control device 20 is as follows Figure 4As shown, in battery control, the definition of the dischargeable power Wout_s in a steady state is changed from 10 seconds to 5 seconds, and the battery 7 is used. In addition, the control device 20 changes the one-time increase ΔWout of the output power during driving control. The dischargeable power Wout_s in a steady state is set to different values ​​when the catalyst device 14 is not being warmed up and when the catalyst device 14 is being warmed up. The one-time increase ΔWout is set to different values ​​when the catalyst device 14 is not being warmed up and when the catalyst device 14 is being warmed up. The control device 20 is limited to executing control to increase the output power of the battery 7 compared to the past during the warming up of the catalyst device 14. In this way, component protection of the hybrid electric vehicle 1 is achieved.

[0049] During battery control, the control device 20 lowers the lower limit voltage Vmin of the battery 7 from a first lower limit value Vmin1 to a second lower limit value Vmin2 while the catalyst is being warmed up. This increases the dischargeable power Wout in the steady state from a first upper limit value Wout_s1 to a second upper limit value Wout_s2. The control device 20 performs the first discharge control when the catalyst device 14 is not being warmed up, and performs the second discharge control when the catalyst device 14 is being warmed up. Battery control includes the first discharge control and the second discharge control. The first discharge control controls the discharge of the battery 7 in a first setting state when the catalyst device 14 is not being warmed up. The first setting state sets the lower limit voltage Vmin of the battery 7 to the first lower limit value Vmin1 and the dischargeable power Wout_s of the battery 7 in the steady state to the first upper limit value Wout_s1. The second discharge control controls the discharge of battery 7 in a second setting state while catalyst device 14 is being warmed up. The second setting state sets lower limit voltage Vmin of battery 7 to a second lower limit value Vmin2 that is smaller than first lower limit value Vmin1, and dischargeable power Wout_s of battery 7 in a steady state to a second upper limit value Wout_s2 that is larger than first upper limit value Wout_s1.

[0050] The first upper limit value Wout_s1 is set to a value such that, when the battery 7 is continuously discharged at the dischargeable power Wout_s in a steady state, the continuous output time until the voltage of the battery 7 reaches the first lower limit value Vmin1 is a first duration. The first duration is, for example, 10 seconds. The second upper limit value Wout_s2 is set to a value such that the continuous output time is a second duration shorter than the first duration. This continuous output time is the time until the voltage of the battery 7 reaches the second lower limit value Vmin2 when the battery 7 is continuously discharged at the dischargeable power Wout_s in a steady state. The second duration is, for example, 5 seconds.

[0051] The control device 20 executes transition control during driving control. Transition control is control for driving while the vehicle outputs a transient dischargeable power Wout_t from the battery 7, which is a temporary increase ΔWout added to the battery 7's steady-state dischargeable power Wout_s. The control device 20 executes setting control to set the increase ΔWout when temporarily increasing the output power of the battery 7. Driving control includes setting control and transition control. During the execution of the first discharge control, the control device 20 sets the increase ΔWout to a first increase ΔWout1. During the execution of the second discharge control, the control device 20 sets the increase ΔWout to a second increase ΔWout2, which is smaller than the first increase ΔWout1.

[0052] The first increment ΔWout1 is set so that power is continuously output for a third duration, which is shorter than the second duration. This continuous output duration is the time from when the battery 7 continuously outputs power obtained by adding the increment ΔWout to the first upper limit value Wout_s1 until the voltage of the battery 7 reaches the first lower limit value Vmin1. The third duration is, for example, one second. The second increment ΔWout2 is set so that power is continuously output for the third duration. This continuous output duration is the time from when the battery 7 continuously outputs power obtained by adding the increment ΔWout to the second upper limit value Wout_s2 until the voltage of the battery 7 reaches the second lower limit value Vmin2.

[0053] Figure 5 It is a flowchart showing the flow of setting processing. Figure 2 The control shown is repeatedly performed by the control device 20 .

[0054] The control device 20 determines whether the catalyst device 14 is being warmed up ( S1 ).

[0055] If the catalyst device 14 is being warmed up ( S1 : YES), the control device 20 sets the lower limit voltage Vmin of the battery 7 to the lower limit voltage for 5 seconds ( S2 ). In S2 , the lower limit voltage Vmin is lowered from the first lower limit value Vmin1 set when the catalyst is not being warmed up. The control device 20 sets the lower limit voltage Vmin to the second lower limit value Vmin2.

[0056] The control device 20 sets the dischargeable power Wout_s in the steady state based on the lower limit voltage for 5 seconds (S3). In S3, the definition of the dischargeable power Wout_s in the steady state is changed to 5 seconds. The control device 20 sets the dischargeable power Wout_s based on the second lower limit value Vmin2. The control device 20 sets the dischargeable power Wout_s in the steady state to the second upper limit value Wout_s2, which is greater than the first upper limit value Wout_s1 set when the catalyst is not warming up.

[0057] The control device 20 sets an increase amount ΔWout for temporarily increasing the output power of the battery 7 based on the lower limit voltage at 5 seconds ( S4 ). In S4 , the temporary increase amount ΔWout is set as a second increase amount ΔWout2 .

[0058] The control device 20 sets the transient dischargeable power Wout_t as the power obtained by adding a temporary increase ΔWout to the steady-state dischargeable power Wout_s (S5). In S5, the value obtained by adding the second increase ΔWout set in S4 to the second upper limit value Wout_s2 set in S3 is set as transient dischargeable power Wout_t2. After executing S5, the control routine ends.

[0059] If the catalyst device 14 is not being warmed up ( S1 : NO), the control device 20 sets the lower limit voltage Vmin of the battery 7 to the lower limit voltage for 10 seconds ( S6 ). In S6 , the lower limit voltage Vmin is set to the first lower limit value Vmin1 .

[0060] The control device 20 sets the dischargeable power Wout_s in the steady state based on the lower limit voltage for 10 seconds ( S7 ). In S7 , the definition of the dischargeable power Wout_s in the steady state is set to 10 seconds. The control device 20 sets the dischargeable power Wout_s to the first upper limit value Wout_s1 .

[0061] The control device 20 sets an increase amount ΔWout for temporarily increasing the output power of the battery 7 based on the lower limit voltage at 10 seconds ( S8 ). In S8 , the temporary increase amount ΔWout is set as a first increase amount ΔWout1 . After executing S8 , the control routine proceeds to S5 .

[0062] When the process proceeds from S8 to S5 , a value obtained by adding the first increase amount ΔWout1 set in S8 to the first upper limit value Wout_s1 set in S7 is set as transient dischargeable power Wout_t1 .

[0063] As described above, according to the embodiment, increasing the steady-state dischargeable power Wout_s during catalyst warm-up prevents the voltage of battery 7 from dropping to the lower limit voltage Vmin. This prevents the motor output torque from being limited due to the voltage of battery 7 reaching the lower limit voltage Vmin during catalyst warm-up. As a result, it is possible to achieve component protection while also preventing a decrease in driving performance during catalyst warm-up.

Claims

1. A hybrid electric vehicle comprising: internal combustion engine; electric motor; a battery storing electric power for supplying to the electric motor; a catalyst device for purifying exhaust gas discharged from the internal combustion engine; as well as a control device that performs driving control for controlling the internal combustion engine and the electric motor and performs battery control for managing the battery, The battery control includes: a first discharge control for controlling discharge of the battery in a first setting state in which the lower limit voltage of the battery is set to a first lower limit value and the dischargeable power of the battery is set to a first upper limit value when the catalyst device is not being warmed up; and a second discharge control for controlling discharge of the battery in a second setting state in which the lower limit voltage of the battery is set to a second lower limit value smaller than the first lower limit value and the dischargeable power of the battery is set to a second upper limit value larger than the first upper limit value, while the catalyst device is being warmed up; The driving control includes: setting control for setting an increase amount when temporarily increasing the output power of the battery; and Transition control, outputting from the battery the power obtained by adding the increased amount to the dischargeable power of the battery to cause the hybrid electric vehicle to travel, The control device: During execution of the first discharge control, the increase amount is set to a first increase amount. During execution of the second discharge control, the increase amount is set to a second increase amount that is smaller than the first increase amount. When the transition control is executed during execution of the second discharge control, electric power obtained by adding the second increase amount to the second upper limit value is output from the battery.

2. The hybrid electric vehicle according to claim 1, wherein: The first upper limit value is set to a power whose continuous output time becomes a first duration until the voltage of the battery reaches the first lower limit value when the battery continues to discharge at the dischargeable power. The second upper limit value is set to power at which, when the battery continuously discharges at the dischargeable power, the continuous output time until the voltage of the battery reaches the second lower limit value becomes a second duration shorter than the first duration.

3. The hybrid electric vehicle according to claim 2, wherein: The first increase is set to a power such that, when the battery continuously outputs power obtained by adding the increase to the first upper limit, the continuous output time until the battery voltage reaches the first lower limit becomes a third duration shorter than the second duration. The second increase is set so that when the battery continuously outputs power obtained by adding the increase to the second upper limit, the continuous output time until the battery voltage reaches the second lower limit becomes the third duration.

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