Hybrid vehicles

Abstract

To provide a hybrid vehicle that can protect components and reduce a decrease in drivability when the output power of a battery is increased during warm-up of a catalyst device.SOLUTION: A hybrid vehicle includes a control device that performs travel control and battery control. The battery control includes: first discharge control that, when a battery is not in a warm-up state of a catalyst device, sets a lower limit voltage of the battery to a first lower limit value and also sets battery dischargeable power to a first upper limit value; and second discharge control that, when the battery is in a warm-up state of the catalyst device, sets the lower limit voltage of the battery to a second lower limit value that is smaller than the first lower limit value and also sets the battery dischargeable power to a second upper limit value that is larger than the first upper limit value. The travel control includes transient control for causing the battery to output power that is a sum of the battery dischargeable power and a temporary increase. The control device is configured to: set the increase to a first increase amount during executing the first discharge control; and set the increase to a second increase amount smaller than the first increase amount during executing the second discharge control.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a hybrid vehicle.

Background Art

[0002] Patent Literature 1 discloses a hybrid vehicle provided with a catalyst device that purifies engine exhaust gas. In the configuration described in Patent Literature 1, when the catalyst device needs to be warmed up and the required power can be satisfied by the output power of the battery, the engine is driven at idle speed to warm up the catalyst device by exhaust heat.

Prior Art Literature

Patent Literature

[0003]

Patent Literature 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the configuration described in Patent Literature 1, the catalyst device is not warmed up even when the catalyst device needs to be warmed up if the required power exceeds the output limit of the battery. Accordingly, it has been considered to relax the output limit of the battery when the catalyst device needs to be warmed up.

[0005] However, when the output limit of the battery is relaxed, an increase in the output power leads to an increase in the amount of voltage drop. Therefore, if a larger amount of power than expected is used during the warming up of the catalyst device, the amount of voltage drop also becomes larger than expected. Consequently, in addition to the battery voltage reaching the lower limit voltage earlier, there is a risk that the voltage will drop below the lower limit. A voltage drop below the lower limit is not preferable from the viewpoint of component protection. In order to ensure component protection, when the battery voltage reaches the lower limit voltage, the output torque of the motor is limited. In this case, the driving force is limited at an earlier timing, which causes shock, sluggish response and other problems.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a hybrid vehicle that can suppress a decrease in driving performance while ensuring component protection when increasing the output power of the battery during the warm-up of the catalytic converter. [Means for solving the problem]

[0007] The present invention relates to a hybrid vehicle comprising an internal combustion engine, an electric motor, a battery for storing power to supply to the electric motor, a catalytic converter for purifying exhaust gases discharged from the internal combustion engine, and a control device that performs driving control to control the internal combustion engine and the electric motor, and also performs battery control to manage the battery, wherein the battery control includes a first discharge control that sets the lower limit voltage of the battery to a first lower limit value and controls the discharge of the battery in a first setting state in which the dischargeable power of the battery is set to a first upper limit value when the catalytic converter is not warming up, and sets the lower limit voltage of the battery to a second lower limit value which is smaller than the first lower limit value and controls the dischargeable power of the battery The driving control includes a second discharge control which controls the discharge of the battery in a second setting state set to a second upper limit greater than the first upper limit, and the driving control includes a setting control which sets the amount of increase when temporarily increasing the output power of the battery, and a transient control which drives by outputting power from the battery that is the sum of the dischargeable power of the battery and the increase, and the control device is characterized in that, while the first discharge control is being executed, the increase is set to a first increase amount, while the second discharge control is being executed, the increase is set to a second increase amount that is smaller than the first increase amount, and when the transient control is being executed while the second discharge control is being executed, power that is the sum of the second upper limit and the second increase amount is output from the battery. [Effects of the Invention]

[0008] In this invention, when increasing the battery output power during the warm-up of the catalytic converter, it is possible to protect the components while suppressing a decrease in driving performance. [Brief explanation of the drawing]

[0009] [Figure 1]This is a schematic diagram illustrating a hybrid vehicle in an embodiment. [Figure 2] This diagram illustrates the dischargeable power and the lower limit voltage of the battery in a steady state. [Figure 3] This is a diagram to explain transient dischargeable power. [Figure 4] This diagram illustrates the state in which the battery's output power is temporarily increased during catalyst warm-up. [Figure 5] This is a flowchart illustrating the configuration process flow. [Figure 6] This is a diagram illustrating the control of the comparative example. [Figure 7] This diagram illustrates the control of another comparative example. [Modes for carrying out the invention]

[0010] The following describes a hybrid vehicle in an embodiment of the present invention. However, the present invention is not limited to the embodiments described below.

[0011] Figure 1 is a schematic diagram showing a hybrid vehicle in an embodiment. The hybrid vehicle 1 comprises an engine (ENG) 2, a first motor (MG1) 3, a second motor (MG2) 4, a power split mechanism 5, a PCU 6, a battery 7, and a control device 20.

[0012] Hybrid vehicle 1 is equipped with an engine 2, a first motor 3, and a second motor 4 as power sources. Engine 2 is an internal combustion engine such as a gasoline engine. Both the first motor 3 and the second motor 4 are motor generators that function as electric motors and generators, 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 an electric motor. The first motor 3 and the second motor 4 are electrically connected to a PCU 6. The first motor 3 is electrically connected to the second motor 4 via the PCU 6. The electricity generated by the first motor 3 is supplied to the second motor 4 via the PCU 6, and torque can be output from the second motor 4 using that electricity.

[0013] The PCU6 includes a first inverter that drives the first motor 3 and a second inverter that drives the second motor 4. The PCU6 is electrically connected to the battery 7. Each motor 3 and 4 is electrically connected to the battery 7 via the PCU6. 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 power to supply each motor 3 and 4. The battery 7 can store the power generated by each motor 3 and 4. The battery 7 is composed of a battery pack comprising multiple battery modules, each consisting of multiple stacked battery cells.

[0014] The power split mechanism 5 splits the power output by the engine 2 between the first motor 3 and the drive shaft 11. The power split mechanism 5 is composed of a single-pinion type planetary gear mechanism. The power split mechanism 5 includes a sun gear 5S, a ring gear 5R, and a carrier 5C that holds the pinion gears meshing with the sun gear 5S and ring gear 5R so that they can rotate and revolve. The first motor 3 is connected to the sun gear 5S. The engine 2 is connected to the carrier 5C. The ring gear 5R is the output element of the power split mechanism 5 and outputs power toward 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 together. The output gear 8 is connected to the differential mechanism 10 via a counter gear mechanism 9. The counter gear mechanism 9 includes a counter driven gear, a counter drive gear, and a counter shaft. The differential mechanism 10 includes a differential ring gear. The differential mechanism 10 is connected to the drive wheels 12 via the drive shaft 11.

[0015] In hybrid 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 counter gear mechanism 9 via a 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 counter gear mechanism 9 and the differential mechanism 10. Hybrid vehicle 1 can operate in an HV driving mode, which is driven by the torque output by the engine 2, and an EV driving mode, which is driven only by the torque output by the second motor 4. In HV driving mode, it is possible to add the torque output by the second motor 4.

[0016] The control device 20 is an electronic control device that controls the hybrid vehicle 1. The control device 20 consists of a microcomputer equipped with 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 vehicle 1 are input to the control device 20. For example, the control device 20 receives a vehicle speed signal from a vehicle speed sensor that detects the vehicle speed, an accelerator opening signal from an accelerator opening sensor that detects the amount the accelerator pedal is operated, 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 / output current of the battery 7, and a voltage signal from a voltage sensor that detects the voltage of the battery 7. The control device 20 performs various controls based on the signals input from the various sensors. At that time, the control device 20 performs calculations using the input data and pre-stored data, and outputs the calculation result as a command signal.

[0017] The control unit 20 comprises a hybrid electronic control unit (HV-ECU), a motor electronic control unit (MG-ECU), and a battery electronic control unit (battery ECU). The control unit 20 performs driving control that controls the engine 2 and each of the motors 3 and 4, and also performs battery control that manages the battery 7. The HV-ECU of the control unit 20 outputs command signals to the engine 2, electrically controlling the output, starting, and stopping of the engine 2. The engine 2's fuel injection and ignition timing are electrically controlled by the control unit 20. The MG-ECU of the control unit 20 outputs command signals to the PCU 6, controlling the motor torque of each of the motors 3 and 4. The battery ECU of the control unit 20 manages and monitors the battery 7.

[0018] As battery control, the control device 20 executes discharge control for controlling discharge of the battery 7. The control device 20 sets a lower limit voltage Vmin of the battery 7 and a dischargeable power Wout of the battery 7. The lower limit voltage Vmin is a value set to achieve component protection. The dischargeable power Wout is the maximum outputtable power that defines a limit on the output power of the battery 7. The dischargeable power Wout indicates an output limit of the battery 7. The control device 20 calculates the dischargeable power Wout based on an SOC indicating a state of charge of the battery 7 and a temperature of the battery 7. The control device 20 calculates the SOC based on an input / output current of the battery 7, a battery voltage, and the like.

[0019] As travel control, the control device 20 calculates a required driving force based on an accelerator opening degree and a vehicle speed. The control device 20 calculates a required power based on the required driving force and the vehicle speed. The control device 20 sets a target rotation speed and a target torque of the engine 2 based on the required power.

[0020] The hybrid vehicle 1 includes a catalyst device 14 that purifies exhaust gas from the engine 2. The catalyst device 14 is provided in an exhaust pipe of the engine 2. The hybrid vehicle 1 can warm up the catalyst device 14 by exhaust heat from the engine 2. When it is necessary to warm up the catalyst device 14, the control device 20 controls the engine 2 to an idling state to warm up the catalyst device 14 by exhaust heat. The idling state refers to an operating state in which the rotation speed of the engine 2 is controlled to an idling rotation speed, and is a state in which the engine 2 rotates without outputting torque.

[0021] The hybrid vehicle 1 has a configuration that assumes it may be necessary to increase the output power of the battery 7 during warm-up of the catalyst device 14 in accordance with the tightening of exhaust gas regulations. When simply increasing the output power of the battery 7, it is conceivable to increase the number of battery cells included in the battery 7. In this case, increasing the number of battery cells increases the size and weight of the battery 7. Therefore, the hybrid vehicle 1 is configured such that, while keeping the number of battery cells included in the battery 7 unchanged, the output power of the battery 7 is increased by devising how the battery 7 is used.

[0022] The control device 20 performs battery control as shown in Figure 2 and driving control as shown in Figure 3. As shown in Figure 2, the control device 20 sets the lower limit voltage Vmin of the battery 7 to the first lower limit value Vmin1 and the dischargeable power Wout_s in the steady state to the first upper limit value Wout_s1. The first upper limit value Wout_s1 is the power whose first duration is the output duration until the voltage of the battery 7 reaches the first lower limit value Vmin1 when the battery 7 continues to discharge at the dischargeable power Wout. The first duration is 10 seconds. That is, the power at which the lower limit voltage Vmin is reached when the battery discharges at the dischargeable power Wout for 10 seconds is the first upper limit value Wout_s1. The first setting state is when 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.

[0023] As shown in Figure 3, the control device 20 can output a transient dischargeable power Wout_t to the battery 7, which is the sum of the steady-state dischargeable power Wout_s and a temporary increase ΔW. The transient dischargeable power Wout_t is the power at which, if discharged continuously, the output duration until the voltage of the battery 7 reaches the lower limit voltage Vmin is 1 second.

[0024] As an example of conventional control, the control of the comparative example shown in Figure 6 can be considered. The control of the comparative example includes battery control and driving control. The battery control of the comparative example includes a control that increases the dischargeable power W1 in the steady state when the catalyst is warming up compared to when the catalyst warm-up is not required. 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 at which the time it takes for the battery voltage to reach the lower limit voltage V1 when the battery continues to discharge at the dischargeable power W1 is 10 seconds. In the battery control of the comparative example, the dischargeable power W1 in the steady state is set to a different value depending on whether the catalyst warm-up is not required or when the catalyst is warming up. The battery control of the comparative example includes a control that increases the dischargeable power W1 in the steady state by lowering the lower limit voltage V1 of the battery when the catalyst is warming up. The lower limit voltage V1 is smaller when the catalyst is warming up than when the catalyst is not warming up.

[0025] As shown in Figure 6, the driving control of the comparative example includes transient control that temporarily increases the battery's output power. Transient control is a control that adds a preset increase ΔW to the steady-state dischargeable power W1. When transient control is performed during catalyst warm-up, the battery outputs a transient dischargeable power W2 which is the sum of the steady-state dischargeable power W1 increased by battery control and the temporary increase ΔW from the driving control.

[0026] Furthermore, based on the control of the comparative example shown in Figure 6, another comparative example control, as shown in Figure 7, can be considered to increase the output power during catalyst warm-up. In the other comparative example shown in Figure 7, control is performed to further increase the battery output power 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 when the catalyst is not warm-up is the power at which the battery voltage reaches the lower limit voltage V11 after 10 seconds of power use. In contrast, the dischargeable power W11 in the steady state when the catalyst is warm-up is the power at which the battery voltage reaches the lower limit voltage V11 after 5 seconds of power use. In this case, if the temporary increase ΔW remains the same as in the control shown in Figure 6, the transient dischargeable power W12, which is the steady-state dischargeable power W11 plus the temporary increase ΔW, will be larger than expected during catalyst warm-up. Therefore, there is a risk that the battery voltage will fall below the lower limit voltage V11.

[0027] Therefore, as shown in Figure 4, the control device 20 is configured to change the primary increase in output power ΔWout in the driving control in accordance with the use of the battery 7 by changing the definition of the dischargeable power Wout_s in the steady state from 10 seconds to 5 seconds in the battery control. The dischargeable power Wout_s in the steady state is set to a different value depending on whether the catalytic converter 14 is warming up or not. The primary increase ΔWout is set to a different value depending on whether the catalytic converter 14 is warming up or not. The control device 20 performs control that increases the output power of the battery 7 compared to the conventional method, but only when the catalytic converter 14 is warming up. This ensures the protection of the components of the hybrid vehicle 1.

[0028] In battery control, the control device 20 lowers the lower limit voltage Vmin of the battery 7 from the first lower limit Vmin1 to the second lower limit Vmin2 when the catalyst is warming up, thereby raising the dischargeable power Wout in the steady state from the first upper limit Wout_s1 to the second upper limit Wout_s2. The control device 20 performs a first discharge control when the catalyst device 14 is not warming up, and performs a second discharge control when the catalyst device 14 is warming up. Battery control includes a first discharge control and a second discharge control. The first discharge control is a discharge control that controls the discharge of the battery 7 in a first setting state in which the lower limit voltage Vmin of the battery 7 is set to the first lower limit Vmin1 when the catalyst device 14 is not warming up, and the dischargeable power Wout_s of the battery 7 in the steady state is set to the first upper limit Wout_s1. The second discharge control is a discharge control that controls the discharge of the battery 7 in a second setting state, in which the lower limit voltage Vmin of the battery 7 is set to a second lower limit value Vmin2 which is smaller than the first lower limit value Vmin1 when the catalyst device 14 is warming up, and the dischargeable power Wout_s of the battery 7 in a steady state is set to a second upper limit value Wout_s2 which is larger than the first upper limit value Wout_s1.

[0029] The first upper limit value Wout_s1 is set to the power level at which the output duration until the voltage of battery 7 reaches the first lower limit value Vmin1, when battery 7 continues to discharge at the steady-state dischargeable power Wout_s, is the first duration. The first duration is, for example, 10 seconds. The second upper limit value Wout_s2 is set to the power level at which the output duration until the voltage of battery 7 reaches the second lower limit value Vmin2, when battery 7 continues to discharge at the steady-state dischargeable power Wout_s, is shorter than the first duration, is the second duration. The second duration is, for example, 5 seconds.

[0030] In driving control, the control device 20 performs transient control by outputting a transient dischargeable power Wout_t from the battery 7, which is the sum of the steady-state dischargeable power Wout_s of the battery 7 and a temporary increase ΔWout, and then driving. The control device 20 performs setting control to set the increase ΔWout when temporarily increasing the output power of the battery 7. Driving control includes setting control and transient control. While the first discharge control is being performed, the control device 20 sets the increase ΔWout to the first increase amount ΔWout1. While the second discharge control is being performed, the control device 20 sets the increase ΔWout to the second increase amount ΔWout2, which is smaller than the first increase amount ΔWout1.

[0031] The first increment ΔWout1 is set to a power level such that, when power output from battery 7 is continuously generated by adding the increment ΔWout to the first upper limit Wout_s1, the output duration until the battery 7 voltage reaches the first lower limit Vmin1 is shorter than the second duration, resulting in a third duration. The third duration is, for example, 1 second. The second increment ΔWout2 is set to a power level such that, when power output from battery 7 is continuously generated by adding the increment ΔWout to the second upper limit Wout_s2, the output duration until the battery 7 voltage reaches the second lower limit Vmin2 is the third duration.

[0032] Figure 5 is a flowchart showing the configuration process flow. The control shown in Figure 2 is repeatedly performed by the control device 20.

[0033] The control device 20 determines whether or not the catalytic converter 14 is warming up (step S1).

[0034] If the catalytic converter 14 is being warmed up (step S1: Yes), the control device 20 sets the lower limit voltage Vmin of the battery 7 to the lower limit voltage for 5 seconds (step S2). In step S2, the lower limit voltage Vmin is lowered to the first lower limit value Vmin1 that is set when the catalytic converter is not being warmed up. The control device 20 sets the lower limit voltage Vmin to the second lower limit value Vmin2.

[0035] The control device 20 sets the dischargeable power Wout_s in the steady state based on the lower limit voltage at 5 seconds (step S3). In step 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 Vmin2. The control device 20 sets the dischargeable power Wout_s in the steady state to a second upper limit Wout_s2 that is greater than the first upper limit Wout_s1 that is set when the catalyst is not warming up.

[0036] The control device 20 sets an increment ΔWout to temporarily increase the output power of the battery 7 based on the lower limit voltage over 5 seconds (step S4). In step S4, the temporary increment ΔWout is set to a second increment ΔWout2.

[0037] The control device 20 sets the transient dischargeable power Wout_t to the power obtained by adding a temporary increase ΔWout to the dischargeable power Wout_s in the steady state (step S5). In step S5, the transient dischargeable power Wout_t2 is set to the value obtained by adding the second upper limit Wout_s2 set in step S3 to the second increase ΔWout2 set in step S4. After the processing in step S5 is performed, this control routine terminates.

[0038] If the catalytic converter 14 is not warming up (step S1: No), the control device 20 sets the lower limit voltage Vmin of the battery 7 to the lower limit voltage for 10 seconds (step S6). In step S6, the lower limit voltage Vmin is set to the first lower limit value Vmin1.

[0039] The control device 20 sets the dischargeable power Wout_s in the steady state based on the lower limit voltage over 10 seconds (step S7). In step 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.

[0040] The control device 20 sets an increment ΔWout to temporarily increase the output power of the battery 7 based on the lower limit voltage over 10 seconds (step S8). In step S8, the temporary increment ΔWout is set to the first increment ΔWout1. After the process in step S8 is completed, the control routine proceeds to step S5.

[0041] If the process proceeds from step S8 to step S5, the transient dischargeable power Wout_t1 is set to the sum of the first upper limit Wout_s1 set in step S7 and the first increase ΔWout1 set in step S8.

[0042] As described above, according to this embodiment, when increasing the dischargeable power Wout_s in a steady state during catalyst warm-up, the voltage of the battery 7 is less likely to drop to the lower limit voltage Vmin. This suppresses the limitation of the motor's output torque due to the battery 7 reaching the lower limit voltage Vmin during catalyst warm-up. As a result, it is possible to suppress the deterioration of driving performance during catalyst warm-up while ensuring component protection. [Explanation of Symbols]

[0043] 1. Hybrid vehicle 2 engines 3. First motor 4. Second motor 7 Batteries 14. Catalytic converter 20 Control device

Claims

1. Internal combustion engines, Electric motor and, A battery for storing power to supply to the aforementioned electric motor, A catalytic converter for purifying exhaust gases discharged from the internal combustion engine, A control device that performs driving control to control the internal combustion engine and the electric motor, and also performs battery control to manage the battery, A hybrid vehicle equipped with, The aforementioned battery control is, A first discharge control that controls the 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 warming up, The second discharge control includes setting the lower limit voltage of the battery to a second lower limit value which is smaller than the first lower limit value, and setting the dischargeable power of the battery to a second upper limit value which is larger than the first upper limit value, while the catalyst device is warming up, and controlling the discharge of the battery in a second set state, The aforementioned driving control is, A setting control that sets the amount of increase when temporarily increasing the output power of the aforementioned battery, This includes transient control, which involves outputting power from the battery equal to the battery's dischargeable power plus the increase, to drive the vehicle. The control device is While the first discharge control is being executed, the increase is set to the first increase amount. While the second discharge control is being executed, the increase is set to a second increase that is smaller than the first increase. When the transient control is performed while the second discharge control is being performed, the battery outputs power equal to the second upper limit plus the second increase. A hybrid vehicle characterized by the following features.

2. The first upper limit is set to a power level such that the output duration until the voltage of the battery reaches the first lower limit is the first duration when the battery continues to discharge at the dischargeable power level. The second upper limit is set to a power level such that the output duration until the battery voltage reaches the second lower limit is shorter than the first duration when the battery continues to discharge at the dischargeable power. The hybrid vehicle according to feature 1.

3. The first increase is set to a power level such that, when the battery continues to output power equal to the first upper limit plus the increase, the output duration until the battery voltage reaches the first lower limit is shorter than the second duration, resulting in a third duration. The second increase is set to a power level such that the output duration until the battery voltage reaches the second lower limit, when the power output from the battery is continuously increased by the second upper limit plus the increase, is the third duration. The hybrid vehicle according to feature 2.

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