JP7600842B2 - Hybrid Vehicles - Google Patents

Description

This disclosure relates to hybrid vehicles, and in particular to hybrid vehicles equipped with an electrically heated catalyst as a catalyst for purifying exhaust gas from an internal combustion engine.

Hybrid vehicles equipped with an internal combustion engine and a traction motor are known to be equipped with an electrically heated catalyst as a catalyst for purifying the exhaust gas from the internal combustion engine. For example, JP 2014-8914 A (Patent Document 1) discloses a technology that can ensure the power required to start the internal combustion engine and start the internal combustion engine normally even if a request to start the internal combustion engine occurs while the electrically heated catalyst is being heated by electrical current.

JP 2014-8914 A

In an internal combustion engine equipped with an electrically heated catalyst, the exhaust purification rate can be increased by passing electricity through the electrically heated catalyst before starting the internal combustion engine, and starting the internal combustion engine after the temperature of the electrically heated catalyst has reached its activation temperature and the warm-up of the electrically heated catalyst has been completed. When the power for the electrically heated catalyst is provided by the power of the driving battery, the power stored in the battery is consumed by the electrically heated catalyst and the driving motor.

When the hybrid vehicle system is stopped and there is a long time until the next trip (system startup), the temperature of the electrically heated catalyst drops to the outside air temperature, so that at the start of the next trip, more power is required to warm up the electrically heated catalyst, and it takes longer for the electrically heated catalyst to warm up. This also increases the amount of power consumed by the drive motor until the electrically heated catalyst warms up. Therefore, in order to increase the purification rate of exhaust gases, if current is applied to the electrically heated catalyst before the internal combustion engine is started at the start of a trip, and the internal combustion engine is started after the temperature of the electrically heated catalyst reaches the activation temperature and the warm-up of the electrically heated catalyst is completed, a lot of power will be consumed. For this reason, if the amount of storage in the power storage device is low, the amount of storage in the power storage device will decrease before the electrically heated catalyst warms up, and the internal combustion engine may be started to generate electricity, which may result in a decrease in the purification rate of exhaust gases.

The objective of this disclosure is to prevent a decrease in the exhaust purification rate in a hybrid vehicle at the start of a trip.

The hybrid vehicle disclosed herein is a hybrid vehicle that includes a hybrid system made up of a traction motor, a power storage device that supplies power to the traction motor, a generator that is driven by the internal combustion engine and generates power to be supplied to the power storage device, and a control device, and is capable of EV driving by running on the power of the traction motor with the internal combustion engine stopped. The internal combustion engine includes an electrically heated catalyst that can be heated with the power of the power storage device, and the control device is configured to operate the internal combustion engine until the SOC reaches or exceeds the predetermined value to charge the power storage device and then stop the internal combustion engine if the SOC of the power storage device falls below a predetermined value when the hybrid system is stopped. The predetermined value is an SOC that heats the electrically heated catalyst until the temperature of the electrically heated catalyst reaches an activation temperature when the hybrid system is started, and allows EV driving.

With this configuration, the hybrid vehicle is capable of EV driving, running on the power of the traction motor with the internal combustion engine stopped. If the SOC of the power storage device falls below a predetermined value when the hybrid system is stopped, the control device operates the internal combustion engine until the SOC reaches or exceeds the predetermined value to charge the power storage device, and then stops the internal combustion engine. The predetermined value is an SOC that allows the electrically heated catalyst to be heated until the temperature of the electrically heated catalyst reaches its activation temperature when the hybrid system is started, and allows EV driving. The SOC (State Of Charge) of the power storage device is a value that indicates the amount of electricity stored in the power storage device, and is expressed, for example, as a percentage of the current amount of electricity stored in the power storage device relative to the full charge capacity of the power storage device.

Therefore, when the hybrid system is started at the start of a trip, the SOC of the power storage device is at a value (amount of stored electricity) that allows the electrically heated catalyst to be heated until its temperature reaches its activation temperature and allows EV driving, so that after the temperature of the electrically heated catalyst reaches its activation temperature and warm-up of the electrically heated catalyst is completed, the internal combustion engine can be started and a decrease in the purification rate of the exhaust gas can be prevented.

Preferably, the predetermined value may be set based on a parameter representing the outside air temperature at the time of starting the hybrid system.

The temperature of the electrically heated catalyst when the hybrid system is started is affected by the outside air temperature. For example, the lower the outside air temperature, the lower the temperature of the electrically heated catalyst, and the more power is required to warm up the electrically heated catalyst and the longer it takes to complete warming up of the electrically heated catalyst. With this configuration, when the hybrid system is started, the electrically heated catalyst is heated until the temperature of the electrically heated catalyst reaches its activation temperature, and the SOC at which EV driving is possible is set based on a parameter that represents the outside air temperature when the hybrid system is started, so it can be set relatively accurately.

Preferably, the predetermined value may be calculated by heating the electrically heated catalyst until its temperature reaches its activation temperature when the hybrid system is started, and learning the amount of electricity discharged from the power storage device when EV driving is performed.

The temperature of the electrically heated catalyst at the start of the hybrid system is affected by the outside air temperature, which changes depending on the environment (season, climate, region, etc.) in which the hybrid vehicle is placed. In addition, the driving pattern (power consumption) during EV driving while the electrically heated catalyst is warming up differs depending on the user of the hybrid vehicle. With this configuration, the SOC at which the electrically heated catalyst is heated to its activation temperature at the start of the hybrid system and EV driving is possible is calculated by learning the amount of power discharged from the power storage device when the electrically heated catalyst is heated to its activation temperature at the start of the hybrid system and EV driving is performed, so that the calculation can be performed taking into account the environment in which the hybrid vehicle is placed and the driving characteristics of the user.

Preferably, the control device may be configured to heat the electrically heated catalyst when the hybrid system is started, and when the SOC of the power storage device falls below a lower limit while the vehicle is running in EV mode, start the internal combustion engine, generate electricity using the generator, and charge the power storage device.

According to this configuration, if the amount of electricity consumed by EV driving becomes greater than initially expected, and the SOC of the power storage device falls to the lower limit before the warm-up of the electrically heated catalyst is completed, the internal combustion engine is started to generate electricity using the generator, and the power storage device is charged. This makes it possible to prevent the power storage device from deteriorating.

Preferably, the control device may be configured to heat the electrically heated catalyst when the hybrid system is started up until the temperature of the electrically heated catalyst reaches an activation temperature, and to limit the output of the traction electric motor when EV driving is being performed.

This configuration limits the power consumed by the traction motor during EV driving, preventing the SOC of the power storage device from dropping to the lower limit before the electrically heated catalyst has finished warming up.

Preferably, the control device may be configured to limit the output of the traction motor when the SOC of the power storage device falls below an output limit threshold.

With this configuration, the output of the traction motor is not limited until the SOC of the power storage device falls to the output limit threshold, ensuring good drivability until the SOC of the power storage device falls to the output limit threshold.

Preferably, the internal combustion engine is equipped with an electric supercharger driven by the power of the power storage device, and the control device may be configured to heat the electrically heated catalyst until the temperature of the electrically heated catalyst reaches an activation temperature when the hybrid system is started, and to drive the electric supercharger when EV driving is being performed.

With this configuration, when the electric supercharger is driven, air heated by electricity flows through the electrically heated catalyst, accelerating the warming up of the electrically heated catalyst.

Preferably, the internal combustion engine is equipped with an air pump that supplies air to the exhaust passage upstream of the electrically heated catalyst, and the control device may be configured to heat the electrically heated catalyst until the temperature of the electrically heated catalyst reaches an activation temperature when the hybrid system is started, and to drive the air pump when EV driving is being performed.

With this configuration, when the air pump is driven, air heated by electricity flows through the electrically heated catalyst, accelerating the warming up of the electrically heated catalyst.

Preferably, the control device may further include an alarm device, and the control device may be configured to notify the user by the alarm device that the internal combustion engine is operating when the hybrid system is stopped and the internal combustion engine is operating until the SOC of the power storage device reaches or exceeds a predetermined value.

With this configuration, even if the internal combustion engine is still operating after the hybrid system has been stopped, it is possible to inform the driver that the engine is operating normally (not abnormally).

According to the present disclosure, in a hybrid vehicle, it is possible to suppress a decrease in the exhaust purification rate at the start of a trip.

1 is an overall configuration diagram of a hybrid vehicle V according to an embodiment of the present invention. 1 is a schematic configuration diagram of an engine 1. FIG. 13A and 13B are diagrams showing changes in the temperature and SCO of the SCR catalyst 74 when the SOC is low at the start of a trip during startup control. 13A and 13B are diagrams showing changes in the temperature and SCO of the SCR catalyst 74 during startup control when the SOC at the start of a trip is high. 3 is a schematic flowchart illustrating a process of stop-time SOC control executed by an HV-ECU 100. 4 is a schematic flowchart of a process for calculating a lower limit value Sl at the start of traveling, which is executed by an HV-ECU 100. FIG. 4 is a diagram illustrating a transition of SOC in stop-time SOC control. 3 is a schematic flowchart illustrating a startup control process executed by an HV-ECU 100. 10 is a schematic flowchart illustrating a startup control process executed by an HV-ECU in a second modified example. 13 is a schematic flowchart illustrating a startup control process executed by an HV-ECU in a third modified example.

The following describes in detail the embodiments of the present disclosure with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated.

Figure 1 is an overall configuration diagram of a hybrid vehicle V according to this embodiment. The hybrid vehicle V is equipped with a hybrid system H that is composed of an engine 1, a first motor generator (hereinafter referred to as the "first MG") 2, a second motor generator (hereinafter referred to as the "second MG") 3, an electricity storage device 7, and an HV-ECU (Electronic Control Unit) 100.

Engine 1 is a compression ignition type internal combustion engine (diesel engine) equipped with an exhaust purification device, the details of which will be described later. The first MG2 and the second MG3 are AC rotating electric machines, for example, three-phase AC synchronous motors with permanent magnets embedded in the rotor.

The hybrid vehicle V is a series hybrid vehicle, and the first MG2 is used as a generator driven by the engine 1. The AC power generated by the first MG2 is converted to DC power by the first inverter 4 and supplied to the power storage device 7 via the boost converter 6 to charge the power storage device 7. At this time, the boost converter 6 operates as a step-down circuit. The power generated by the first MG2 is supplied to the second MG3 via the second inverter 5. The first inverter 4 may convert the DC power supplied from the power storage device 7 to AC power for driving the first MG2, and the engine 1 may be cranked or motored using the first MG2.

The second MG3 mainly operates as an electric motor and drives the drive wheels 8. The second MG3 corresponds to the "driving motor" of this disclosure. The second MG3 is driven by at least one of the electric power from the power storage device 7 and the electric power generated by the first MG2, and the drive force of the second MG3 is transmitted to the drive wheels 8. On the other hand, when the hybrid vehicle V is braking or going downhill, the second MG3 operates as a generator and performs regenerative power generation. The electric power generated by the second MG3 is charged to the power storage device 7 via the second inverter 5. The second inverter 5 also converts the DC power of the power storage device 7, boosted by the boost converter 6, into AC power for driving the second MG3.

The power storage device 7 is a rechargeable DC power source, and is configured to include a secondary battery such as a lithium-ion battery or a nickel-metal hydride battery. The power storage device 7 is charged by receiving electric power generated by at least one of the first MG2 and the second MG3. The power storage device 7 then supplies the stored electric power to the second inverter 5 and the first inverter 4. Note that an electric double layer capacitor or the like can also be used as the power storage device 7.

The power storage device 7 is provided with a monitoring unit 7a. The monitoring unit 7a includes a voltage sensor, a current sensor, and a temperature sensor (none of which are shown) that detect the voltage, input/output current, and temperature of the power storage device 7, respectively. The monitoring unit 7a outputs the detection values of each sensor (the voltage, input/output current, and temperature of the power storage device 7) to the BAT-ECU 110.

The step-down converter 9 steps down the DC power from the power storage device 7 and supplies it to the electric supercharger 30 and electric heater 78, which will be described later.

The hybrid vehicle V further includes a BAT-ECU 110, various sensors 120, a communication device 130, a navigation device 140, an HMI (Human Machine Interface) device 150, and an E/G-ECU 200. The HV-ECU 100, the BAT-ECU 110, and the E/G-ECU 200 are configured to be able to communicate with each other via a CAN (Controller Area Network) 150.

The HV-ECU 100 as a control device includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores processing programs, etc., a RAM (Random Access Memory) that temporarily stores data, and an input/output port (not shown) for inputting and outputting various signals, and executes predetermined calculation processing based on information stored in the memory (ROM and RAM), information from various sensors 120, and information from the BAT-ECU 110 and E/G-ECU 200. Then, based on the results of the calculation processing, the HV-ECU 100 controls the first inverter 4, the second inverter 5, and the boost converter 6, and outputs commands to the E/G-ECU 200.

When the power switch (ignition switch) 121 is operated while the hybrid system H is stopped, the HV-ECU 100 starts the hybrid system H and makes the hybrid vehicle V ready to run. Also, when the power switch 121 is operated while the hybrid system H is operating (started), the HV-ECU 100 stops the hybrid system H. This puts the hybrid vehicle V into a stopped state in preparation for the next trip.

The BAT-ECU 110 also includes a CPU, ROM, RAM, input/output ports, etc. (none of which are shown). The BAT-ECU 110 calculates the SOC, which indicates the amount of electricity stored in the storage device 7, based on the detection values of the input/output current and/or voltage of the storage device 7 from the monitoring unit 7a. The SOC is expressed as a percentage of the current amount of electricity stored in the storage device 7 relative to the full charge capacity. The BAT-ECU 110 then outputs the calculated SOC to the HV-ECU 100. The SOC may also be calculated in the HV-ECU 100.

The various sensors 120 include, for example, an accelerator pedal sensor, an engine speed sensor, a vehicle speed sensor, an outside air temperature sensor, a catalyst temperature sensor, and the like. The accelerator pedal sensor detects the amount of accelerator pedal operation by the user (hereinafter also referred to as "accelerator opening") AP. The engine speed sensor detects the rotation speed (revolutions) NE of the engine 1. The vehicle speed sensor detects the speed (vehicle speed) SPD of the hybrid vehicle V. The outside air temperature sensor detects the outside air temperature. The catalyst temperature sensor 122 (see FIG. 2) detects the temperature of the selective reduction catalyst described below.

The communication device 130 is configured to include various communication I/Fs (interfaces). The communication device 130 may include a DCM (Data Communication Module). The communication device 130 may include a communication I/F compatible with 5G (fifth generation mobile communication system). The HV-ECU 100 is configured to perform wireless communication with a communication device external to the hybrid vehicle V via the communication device 130.

The navigation device 140 includes a navigation ECU, a map information database (DB), a GPS (Global Positioning System) receiver, and a traffic information receiver (not shown). The navigation ECU includes a CPU, ROM, RAM, input/output ports, etc., and outputs the current position of the hybrid vehicle V, as well as surrounding map information and traffic congestion information, etc., to the HV-ECU 100 and the HMI device 150 based on various information and signals received from the map information DB, the GPS receiver, and the traffic information receiver.

The HMI device 150 is a device that provides the user with information to assist in driving the hybrid vehicle V. The HMI device 150 is typically a display installed inside the vehicle cabin and also includes a speaker, etc. The HMI device 150 provides the user with various information by outputting visual information (graphical information, textual information), auditory information (audio information, sound information), etc.

The E/G-ECU 200, which controls the operating state of the engine 1, similar to the HV-ECU 100, includes a CPU, memory (ROM and RAM), input/output ports for inputting and outputting various signals, and executes predetermined calculations based on information from the various sensors 120 and information from the HV-ECU 100 to control the engine 1.

Figure 2 is a schematic diagram of the engine 1. The engine 1 is a diesel engine, an internal combustion engine that injects fuel from a fuel injector 14 into a combustion chamber formed in a cylinder 12 of the engine body 10, and performs compression self-ignition. An air cleaner 22, an intercooler 24, and an intake throttle valve (electronically controlled throttle) 26 are provided in the intake passage 20 of the engine 1. Fresh air from which foreign matter has been removed by the air cleaner 22 is supercharged (compressed) by a compressor 32 of an electric supercharger 30, cooled by the intercooler 24, and supplied to an intake manifold 28, and supplied to each combustion chamber from an intake port. The compressor 32 of the electric supercharger 30 is rotated and driven by a motor 34.

The exhaust gas discharged from the combustion chamber is collected in the exhaust manifold 50 and released to the outside air via the exhaust passage 52. Although not shown, the engine 1 is equipped with an EGR (Exhaust Gas Recirculation) device that recirculates a portion of the exhaust gas to the intake manifold 28.

In the exhaust passage 52, an oxidation catalyst 70, a DPF (Diesel Particulate Filter) 72, a selective reduction catalyst 74, and an oxidation catalyst 76 are provided from the upstream side. The oxidation catalyst 70 oxidizes carbon monoxide (CO) in the exhaust gas to carbon dioxide (CO2), and oxidizes hydrocarbons (HC) in the exhaust gas to water ( _H2O ) and _CO2 . It also oxidizes nitrogen monoxide (NO) in the exhaust gas to nitrogen dioxide ( _NO2 ). This is because the reduction reaction of nitrogen oxides (NOx) has a fast reaction rate when the ratio of NO to _NO2 is 1:1, and since diesel engine exhaust gas contains a large amount of NO, the NO in the exhaust gas is oxidized to _NO2 to bring the ratio of NO to _NO2 closer to 1:1.

The DPF 72 collects particulate matter in the exhaust gas and purifies it by appropriately burning and removing the collected particulate matter. The selective reduction catalyst (hereinafter also referred to as the SCR (Selective Catalytic Reduction) catalyst) 74 reduces and purifies NOx in the exhaust gas. The oxidation catalyst 76 oxidizes and purifies ammonia discharged (slips) from the SCR catalyst 74.

The SCR catalyst 74 is, for example, a ceramic carrier carrying copper (Cu) ion-exchanged zeolite as a catalyst, and exhibits a high purification rate by using ammonia (NH3) as a reducing agent. The ammonia used as the reducing agent is generated by hydrolysis of urea water supplied to the exhaust passage upstream of the SCR catalyst 74. A urea addition valve (urea water injection injector) 80 is provided in the exhaust passage upstream of the SCR catalyst 74, and urea water pumped from a urea water tank 82 by a pump (not shown) is injected from the urea addition valve 80 into the exhaust passage 52 upstream of the SCR catalyst 74.

In this embodiment, the SCR catalyst 74 is configured as an electrically heated catalyst (EHC (Electrically Heated Catalyst)). An electric heater 78 is provided integrally with the SCR catalyst 74 on the upstream side of the SCR catalyst 74, and the carrier carrying the catalyst can be heated by passing electricity through the electric heater 78. The catalyst carrier of the SCR catalyst 74 may be formed from a material (e.g., SiC (silicon carbide)) that becomes electrically resistant and generates heat when electricity is passed through it, to serve as an electrically heated catalyst.

The catalyst temperature sensor 122 detects the temperature of the SCR catalyst 74, for example, the catalyst bed temperature. The motor 34 and electric heater 78 of the electric supercharger 30 are driven by the power of the power storage device 7, the voltage of which is stepped down by the step-down converter 9.

In the engine 1 configured as described above, NOx in the exhaust gas is reduced and purified by the SCR catalyst 74. In order for the SCR catalyst 74 to effectively purify the NOx in the exhaust gas, it is desirable for the temperature of the SCR catalyst 74 to reach its activation temperature and be sufficiently activated. For example, when the temperature of the SCR catalyst 74 is 200°C or higher, a purification rate of 90% or more is achieved, demonstrating good purification performance.

<Normal control>
In the present embodiment, the HV-ECU 100 executes normal control when the temperature of the SCR catalyst 74 reaches the activation temperature and is sufficiently activated. The normal control executed by the HV-ECU 100 is, for example, the following control.

First, the required driving force is calculated using the accelerator opening AP and vehicle speed SPD as parameters, and the command torque Tm of the second MG3 is obtained based on the required driving force. The power (driving power) PWs required for the second MG to output the command torque Tm is calculated, and the charging power PWb (which will be a negative value when the SOC is greater than the target SOC*) is calculated based on the difference between the SOC of the storage device 7 and the target SOC*. The driving power PWs and the charging power PWb are then added together to calculate the required power generation amount PW*.

The HV-ECU 100 calculates the target rotation speed NG* of the first MG2 based on the required power generation PW*, and determines the target torque TG* of the first MG2 from the required power generation PW* and the target rotation speed NG*. The HV-ECU 100 controls the second inverter 5 so that the second MG3 is driven by the command torque Tm, and outputs the target torque TG* to the engine ECU 200. The engine ECU 200 determines the fuel injection amount so that the torque of the first MG2 becomes the target torque TG*, and operates (runs) the engine 1.

In order for the SCR catalyst 74 to effectively purify NOx in the exhaust gas, it is desirable that the temperature of the SCR catalyst 74 reaches the activation temperature and is sufficiently activated. In particular, when the hybrid system H is stopped and there is a long time until the next trip (activation of the hybrid system H), the temperature of the SCR catalyst 74 drops to the outside air temperature. In this way, when the temperature of the SCR catalyst 74 is low, the operation (driving) of the engine 1 is stopped, electricity is passed through the electric heater 78 to heat the SCR catalyst 74, and after the temperature of the SCR catalyst 74 reaches the activation temperature and the warm-up of the SCR catalyst 74 is completed, the engine 1 is started, thereby improving the purification rate of the exhaust gas.

In this embodiment, when the temperature of the SCR catalyst 74 is low at the start of a trip (when the hybrid system H is started), the operation (driving) of the engine 1 is stopped, the electric heater 78 is energized to heat the SCR catalyst 74, and until the temperature of the SCR catalyst 74 reaches the activation temperature and warm-up of the SCR catalyst 74 is completed, the control of running the vehicle as an EV running powered by the second MG 3 with the engine 1 stopped is also referred to as startup control. In this embodiment, by setting the required power generation amount PW* to 0 until warm-up of the SCR catalyst 74 is completed, it is possible to run the vehicle as an EV running powered by the second MG 3 with the engine 1 stopped.

Figure 3 shows the transition of the temperature and SCO of the SCR catalyst 74 in startup control when the SOC at the start of the trip is small. Figure 3(A) shows the change in temperature of the SCR catalyst 74, and Figure 3(B) shows the change in SOC. When the hybrid system H starts at time t0, electricity is started to be supplied to the electric heater 78, and EV driving is started. The SCR catalyst 74 is heated by the electric heater 78, and as shown in Figure 3(A), the temperature of the SCR catalyst 74 rises, and at time t2, the temperature of the SCR catalyst 74 reaches the activation temperature Ta. The activation temperature Ta may be, for example, a temperature at which the purification rate of the SCR catalyst 74 is 90% or more.

The electric power stored in the storage device 7 is consumed by the electric heater 78 and by the second MG3 during EV driving (note that, as described later, when the electric supercharger 30 is driven, it is also consumed by the motor 34), and no power is generated by the first MG2. Therefore, as shown in FIG. 3B, the SOC decreases, and at time t1, it decreases to the lower limit value Sf. The lower limit value Sf is set as a value below which the deterioration of the storage device 7 (battery) progresses, and is, for example, 20%. At time t1 when the SOC has decreased to the lower limit value Sf, the engine 1 is started to generate power by the first MG2, and the storage device 7 is forcibly charged. Therefore, the SOC gradually increases after time t1.

When engine 1 is started at time t1, the temperature of SCR catalyst 74 is lower than activation temperature Ta, which raises the concern that engine 1 may be operated with relatively low exhaust purification performance.

Figure 4 shows the changes in temperature and SCO of the SCR catalyst 74 during startup control when the SOC is high at the start of a trip. Figure 4(A) shows the change in temperature of the SCR catalyst 74, and Figure 4(B) shows the change in SOC. When the hybrid system H starts up at time t0, electricity begins to be supplied to the electric heater 78, and EV driving begins.

As shown in FIG. 4(A), the temperature of the SCR catalyst 74 rises, and at time t2, similar to FIG. 3(A), the temperature of the SCR catalyst 74 reaches the activation temperature Ta.

As shown in FIG. 4(B), the SOC of the storage device 7 is large at the start of the trip, and is maintained at or above the lower limit Sf at time t2 when the temperature of the SCR catalyst 74 reaches the activation temperature Ta. Then, when the warm-up of the SCR catalyst 74 is completed at time t2, the system transitions from startup control to normal control, and at time t3 the engine 1 is started. The engine 1 and the first MG2 are controlled so that the power generation amount of the first MG2 becomes the required power generation amount PW*, and the SOC gradually increases. When the engine 1 is started at time t3, the warm-up of the SCR catalyst 74 is completed, and therefore a decrease in the purification rate of the exhaust gas can be suppressed.

In this way, if the SOC at the start of the trip is such that the electric heater 78 is energized until the temperature of the SCR catalyst 74 reaches the activation temperature Ta, and the amount of stored electricity is sufficient for EV driving, the engine 1 is started after the SCR catalyst 74 is warmed up, so that a decrease in the purification rate of the exhaust gas at the start of the trip can be suppressed.

<SOC control during stop>
In this embodiment, when the hybrid system H is stopped, stop-time SOC control is executed so that the SOC at the start of the trip is such that electricity is supplied to the electric heater 78 until the temperature of the SCR catalyst 74 reaches the activation temperature Ta, and the amount of stored electricity is sufficient for EV driving.

Figure 5 is a schematic flow chart illustrating the process of stop-time SOC control executed by the HV-ECU 100. This flow chart shows the process executed when the power switch 121 is operated while the hybrid system H is in operation (started) and the hybrid system H is stopped.

When the power switch 121 is operated while the hybrid system H is in operation, first, in step (hereinafter, step is abbreviated as S) 10, it is determined whether the SOC of the power storage device 7 is equal to or greater than the lower limit value Sl at the start of driving. The SOC may be the SOC calculated by the BAT-ECU 110. The lower limit value Sl at the start of driving is the amount of electricity stored in the power storage device 7 at which the electric heater 78 is energized until the temperature of the SCR catalyst 74 reaches the activation temperature Ta and EV driving is possible, and is calculated by the lower limit value Sl calculation process at the start of driving. The lower limit value Sl at the start of driving corresponds to the "predetermined value" in this disclosure.

Figure 6 is a schematic flowchart of the process for calculating the lower limit value Sl at the start of driving, which is executed by the HV-ECU 100. This flowchart is also executed when the power switch 121 is operated while the hybrid system H is in operation (started) and the hybrid system H is stopped. Referring to Figure 6, in S20, the current position of the hybrid vehicle V is obtained. For example, the current position may be obtained based on GPS information received by a GPS receiver of the navigation device 140.

Next, in S21, the outside air temperature TH at the start of the next trip is estimated based on the current position of the hybrid vehicle V. For example, communication may be performed via the communication device 130 with a server 500 (see FIG. 1) having a weather information database (DB), and the change in the outside air temperature (air temperature) at the current position within the past 24 hours may be obtained from the weather information DB of the server 500, and the lowest temperature may be estimated as the outside air temperature TH at the start of the next trip. Note that if the user has input (set) the planned date and time of the next trip start into the navigation device 140, the outside air temperature (air temperature) at the current position at the input planned trip start date and time may be obtained from the weather information DB of the server 500 and estimated as the outside air temperature TH.

In the next step S22, the heating power requirement KW is calculated based on the outside air temperature TH estimated in S21 at the start of the next drive. The heating power requirement KW is the amount of power required to raise the temperature of the SCR catalyst 74 to the activation temperature Ta by heating the electric heater 78, assuming that the temperature of the SCR catalyst 74 is the outside air temperature TH (the outside air temperature TH at the start of drive). The heating power requirement KW can be calculated using the difference between the activation temperature Ta and the outside air temperature TH, the heat capacity of the SCR catalyst 74, the amount of heat released from the exhaust passage 52 and the SCR catalyst 74, etc., but in this embodiment, the relationship between the outside air temperature TH and the heating power requirement KW is obtained in advance through experiments, etc., and a map is created in advance and stored in memory. Then, the heating power requirement KW is calculated by referring to the map using the outside air temperature TH as a parameter.

Next, in S23, the amount of electric power DW required for EV driving is calculated. The amount of electric power DW required for EV driving is the amount of electric power consumed by the second MG3 during EV driving during the time required for heating the electric heater 78 to raise the temperature of the SCR catalyst 74 to the activation temperature Ta, assuming that the temperature of the SCR catalyst 74 is the outside air temperature TH (the outside air temperature TH at the start of driving). The amount of electric power DW required for EV driving is calculated by creating a map using the outside air temperature TH as a parameter in advance through experiments or the like, and storing it in memory. For example, when the outside air temperature is the outside air temperature TH and the temperature of the SCR catalyst 74 is the outside air temperature TH, the city mode of the Worldwide harmonized Light duty Test Cycle (WLTC) mode is applied to drive the hybrid vehicle V in EV driving. During this EV driving, the rated power is applied (supplied) to the electric heater 78 to heat the SCR catalyst 74. Then, the amount of power consumed by (supplied to) the second MG3 from the start of driving until the temperature of the SCR catalyst 74 reaches the activation temperature Ta is calculated as the amount of power required for EV driving DW, and a map is created with the outside air temperature TH as a parameter. The amount of power required for EV driving DW is calculated by referring to the map with the outside air temperature TH as a parameter. Note that the map of the amount of power required for heating KW with the outside air temperature TH as a parameter is also created in this experiment etc. from the amount of power consumed by the electric heater 78 from the start of driving until the temperature of the SCR catalyst 74 reaches the activation temperature Ta.

Next, in S24, a lower limit value Sl at the start of driving is calculated based on the amount of power required for heating KW calculated in S22 and the amount of power required for EV driving DW calculated in S23. For example, an SOC equivalent to the amount of power stored at the lower limit value Sf of the SOC of the power storage device 7 plus the amount of power required for heating KW and the amount of power required for EV driving DW is calculated as the lower limit value Sl at the start of driving, and the process proceeds to S25.

In S25, it is determined whether the lower limit value Sl at the start of running calculated in S24 exceeds the upper limit value Su of the SOC of the storage device 7. The upper limit value Su is a value at which the SOC of the storage device 7 deteriorates rapidly, and may be, for example, 90%. If the lower limit value Sl at the start of running is equal to or less than the upper limit value Su, a negative determination is made and the current routine is terminated. If the lower limit value Sl at the start of running is greater than the upper limit value Su, a positive determination is made and the process proceeds to S26, where the lower limit value Sl at the start of running is guarded against by the upper limit value Su (the value of Sl is replaced with Su), and the current routine is terminated.

Returning to FIG. 5, in S10, it is determined whether the SOC of the storage device 7 is equal to or greater than the lower limit S1 at the start of driving calculated as described above. If the SOC is less than the lower limit S1 at the start of driving, a negative determination is made and the process proceeds to S11.

In S11, it is determined whether the engine 1 is running or not. If the engine 1 is stopped and the determination is negative, the process proceeds to S12, where the engine 1 is started, and then to S13. If the engine 1 is running, the determination is positive and the process proceeds to S13.

In S13, the engine 1 and the first MG2 are controlled so that the amount of power generated by the first MG2 becomes the required power generation amount PW*. The required power generation amount PW* may be set to a value at which the engine 1 can be operated in a region where the fuel consumption rate of the engine 1 is low and the operating noise of the engine 1 is small, or may be set to an operating region where the power generation efficiency is high. As a result, power is generated by the first MG2 and the storage device 7 is charged, thereby increasing the SOC.

Next, in S14, the display of the HMI device 150 indicates that the engine 1 is running, and then the process returns to S10. Note that the process in S14 only needs to notify the user that the engine 1 is running, and may be, for example, a notification by sound or voice.

If the SOC is equal to or greater than the lower limit Sl when the hybrid system H is stopped, or if the power storage device 7 is charged and the SOC is equal to or greater than the lower limit Sl when the vehicle starts to travel, a positive determination is made in S10 and the process proceeds to S15.

In S15, engine 1 is stopped, and then the current routine is terminated. In S15, when engine 1 is stopped, the crank angle is adjusted by first MG2 to stop engine 1 so that engine 1 is stopped with the valve timing of the intake valve and exhaust valve overlapping in at least one cylinder. Note that if the display shows in S14 that engine 1 is operating, the display is stopped.

7 is a diagram illustrating the transition of the SOC in the stop SOC control. In FIG. 7, the vertical axis is the SOC of the storage device 7, and the horizontal axis is time. At time ts, the power switch 121 is operated while the hybrid system H is in operation (started), and the hybrid system H is stopped. If the SOC is smaller than the lower limit value S1 at the start of running at time ts, a negative determination is made in S10 of FIG. 5, and S13 is processed, so that the first MG2 generates electricity and the storage device 7 is charged, thereby increasing the SOC. At time te, when the storage device 7 is charged and the SOC becomes equal to or greater than the lower limit value S1 at the start of running, the engine 1 is stopped. As a result, the SOC at the start of the next trip becomes equal to or greater than the lower limit value S1 at the start of running, and the SOC at the start of the trip can be stored enough to energize the electric heater 78 and enable EV running until the temperature of the SCR catalyst 74 reaches the activation temperature Ta.

In FIG. 7, the target SOC* is the target value of the SOC of the storage device 7 under normal control, and in this embodiment, it is set as an SOC range having a predetermined width. Therefore, the charging power PWb under normal control is a positive value when the SOC falls below the target SOC* range, and is a negative value when the SOC exceeds the target SOC* range. Also, when the SOC is within the target SOC* range, the charging power PWb is set to 0.

Start-up control
In this embodiment, at the start of a trip, power is supplied to the electric heater 78 until the temperature of the SCR catalyst 74 reaches the activation temperature Ta, and startup control is performed to run the vehicle as an EV. Figure 8 is a schematic flowchart illustrating the startup control process executed by the HV-ECU 100. This flowchart is executed when the power switch 121 is operated while the hybrid system H is stopped, and the hybrid system H is started up.

When the power switch 121 is operated and the hybrid system H is started, first in S30, it is determined whether the temperature Tc of the SCR catalyst detected by the catalyst temperature sensor 122 is equal to or higher than the activation temperature Ta. If the temperature Tc of the SCR catalyst 74 is lower than the activation temperature Ta, a negative determination is made and the process proceeds to S31.

In S31, the rated power is applied (supplied) to the electric heater 78, and power is supplied to the motor 34 of the electric supercharger 30 to drive the compressor 32. If the valve timing of the intake valve and the exhaust valve do not overlap in at least one cylinder of the engine 1, the first MG2 is driven to set the crank angle at which the valve timing of the intake valve and the exhaust valve overlap in at least one cylinder.

Next, in S32, with the engine 1 stopped, the second inverter 5 is controlled so that the second MG3 is driven with command torque Tm, and EV driving is performed. As with normal control, the command torque Tm is calculated by calculating the required driving force using the accelerator opening AP and vehicle speed SPD as parameters, and the command torque Tm of the second MG3 is obtained so that the required driving force is output from the drive wheels 8.

In S33, it is determined whether the SOC is equal to or lower than the lower limit Sf. If the SOC is greater than the lower limit Sf and the determination is negative, the process returns to S30.

If the temperature Tc of the SCR catalyst is equal to or higher than the activation temperature Ta and a positive judgment is made in S30, or if the SOC is equal to or lower than the lower limit Sf and a positive judgment is made in S33, the process proceeds to S34. In S34, the process transitions from startup control to normal control, and the current routine ends.

In this embodiment, by executing the startup control, at the start of a trip, the electric heater 78 is energized and EV driving is performed until the temperature of the SCR catalyst 74 reaches the activation temperature Ta. At this time, the electric supercharger 30 is driven, and fresh air (air) that has flowed from the intake passage 20 into the combustion chamber where the valve timing overlaps flows through the exhaust passage 52. As a result, the air heated by the electric heater 78 flows through the SCR catalyst 74, so that the SCR catalyst 74 can be heated efficiently.

In addition, if the amount of power consumed by EV driving becomes greater than initially expected, and the SOC of the power storage device 7 falls to the lower limit Sf before the warm-up of the SCR catalyst 74 is completed (if a positive determination is made in S33), the system transitions to normal control. When the system transitions to normal control, the engine 1 is started, power is generated by the first MG2, the power storage device 7 is charged, and deterioration of the power storage device 7 can be prevented.

According to this embodiment, by executing the stop SOC control, the SOC at the start of the trip is equal to or greater than the lower limit Sl at the start of driving, and the SOC at the start of the trip is set to a storage amount that allows EV driving by energizing the electric heater 78 until the temperature of the SCR catalyst 74 reaches the activation temperature Ta. Then, by executing the start-up control, at the start of the trip, electricity is energized to the electric heater 78 until the temperature of the SCR catalyst 74 reaches the activation temperature Ta, and EV driving is performed. Therefore, a decrease in the purification rate of the exhaust gas can be suppressed at the start of the trip.

(Variation 1)
In the present embodiment, when the electric heater 78 is energized during the startup control, the electric supercharger 30 is driven. However, an electric air pump may be provided in the exhaust passage 52, and the electric air pump may be driven instead of or in addition to driving the electric supercharger 30. For example, with reference to FIG. 1 , an electric air pump 40 shown by a dashed line may be provided in the exhaust passage 52 upstream of the electric heater 78. Then, when the electric heater 78 is energized during the startup control, the electric air pump 40 may be driven so that air heated by the electric heater 78 flows through the SCR catalyst 74.

(Variation 2)
In the present embodiment, the lower limit value S1 at the start of traveling is calculated based on the outside air temperature TH at the start of the next traveling. However, the method of calculating the lower limit value S1 at the start of traveling is not limited to this. In the second modification, the lower limit value S1 at the start of traveling is calculated by energizing the electric heater 78 until the temperature of the SCR catalyst 74 reaches the activation temperature Ta at the start of the hybrid system H and learning the amount of electric power discharged from the power storage device 7 when EV traveling is performed.

Figure 9 is a schematic flowchart illustrating the startup control process executed by HV-ECU 100 in variant 2. In variant 2, the lower limit value Sl at the start of driving is calculated during startup control. The flowchart shown in Figure 9 is the flowchart in Figure 8 to which S41 to S46 have been added, and S30 to S34 are the same as those in the flowchart in Figure 8, so their description will be omitted.

In FIG. 9, if a negative determination is made in S33, i.e., the electric heater 78 is energized until the temperature of the SCR catalyst 74 reaches the activation temperature Ta, and EV driving is performed, the discharged power amount HW of the power storage device 7 is calculated in S41. For example, the discharged power may be calculated from the value of the output current detected by the current sensor of the monitoring unit 7a, and the discharged power amount HW may be calculated by integrating the discharged power.

If the result of S33 is positive, proceed to S42, add the margin α to the discharged power amount HW (HW+α) to set the discharged power amount HW (replace the discharged power amount HW with HW+α), and then proceed to S43.

In S43, the power amount learned value GW is calculated using the following formula (1).
GW=GWn*(1-k)+HW*k...(1)
GWn is the previous value of the power amount learned value GW. k is a weighting coefficient, which is set to a value greater than 0 and less than 1, and may be, for example, 0.1.

In S43, the power amount learning value GW calculated using formula (1) is stored in memory as the previous value GWn, and then the process proceeds to S44.

In S44, the lower limit value Sl at the start of driving is calculated based on the power amount learning value GW calculated in S43. For example, the SOC corresponding to the amount of electricity stored in the power storage device 7 at the lower limit value Sf of the SOC plus the power amount learning value GW is calculated as the lower limit value Sl at the start of driving, and the process proceeds to S45.

In S45, it is determined whether the lower limit value Sl at the start of running calculated in S44 exceeds the upper limit value Su of the SOC of the storage device 7. If the lower limit value Sl at the start of running is equal to or less than the upper limit value Su, a negative determination is made and the process proceeds to S34. If the lower limit value Sl at the start of running is greater than the upper limit value Su, a positive determination is made and the process proceeds to S46, where the lower limit value Sl at the start of running is guarded against the upper limit value Su (the value of Sl is replaced with Su), and the process proceeds to S34.

According to the second modification, when the hybrid system H is started, the electric heater 78 is energized to heat the SCR catalyst 74 until the temperature of the SCR catalyst 74 reaches the activation temperature Ta, and the SOC (start-of-travel lower limit Sl) at which EV driving is possible is calculated based on the power amount learning value GW that learns the amount of power discharged from the power storage device 7 when EV driving is performed, while the electric heater 78 is energized until the temperature of the SCR catalyst 74 reaches the activation temperature Ta at the start of the hybrid system H. Therefore, the start-of-travel lower limit Sl can be calculated with high accuracy, taking into account the environment in which the hybrid vehicle V is placed and the driving characteristics of the user.

(Variation 3)
8, in the startup control, the second inverter 5 is controlled so that the second MG3 is driven with the command torque Tm while the engine 1 is stopped, and EV running is performed. At this time, the command torque Tm is calculated by calculating the required driving force using the accelerator opening AP and the vehicle speed SPD as parameters, as in the normal control, and the command torque Tm of the second MG3 is obtained so that the required driving force is output from the drive wheels 8.

In the hybrid vehicle V, the capacity of the power storage device 7 is relatively small. For this reason, if the amount of power consumed by the second MG3 during EV driving in startup control is large, there is a concern that the SOC will frequently drop to the lower limit Sf before the warm-up of the SCR catalyst 74 is complete. In the third modification, when EV driving is performed, the output of the second MG3 is limited, and the power consumed by the second MG3 is limited, making it possible to prevent the SOC from dropping to the lower limit Sf before the warm-up of the SCR catalyst 74 is complete.

Figure 10 is a schematic flowchart illustrating the startup control process executed by HV-ECU 100 in Modification 3. The flowchart shown in Figure 10 is the flowchart in Figure 8 to which S51 and S52 have been added, and S30 to S34 are the same as those in the flowchart in Figure 8, so their description will be omitted.

In FIG. 10, when EV driving is performed in S32, in S51, it is determined whether the SOC is equal to or lower than the output limit threshold Sd. The output limit threshold Sd is set as a value between the lower limit value Sl at the start of driving and the lower limit value Sf. If the SOC is greater than the output limit threshold Sd, a negative determination is made and the process proceeds to S33. If the SOC is equal to or lower than the output limit threshold Sd, a positive determination is made and the process proceeds to S52.

In S52, the magnitude of the command torque Tm is limited. For example, an upper limit may be set for the command torque Tm, and the command torque Tm may be limited so as not to exceed the upper limit. Alternatively, the command torque Tm may be multiplied by a coefficient kd (e.g., 0.7) that is smaller than 1, and the value may be replaced with the command torque Tm (Tm←Tm*kd) to drive the second MG3. After S52, the process proceeds to S33.

According to this modification 3, during EV driving in startup control, the output of the second MG3 is limited, and the power consumed by the second MG3 is limited, thereby preventing the SOC from dropping to the lower limit value Sf before the warm-up of the SCR catalyst 74 is completed.

In this embodiment, in the stop-time SOC control, when the SOC becomes equal to or greater than the lower limit Sl at the start of driving, the engine 1 is stopped and charging of the storage device 7 is terminated. However, even if the SOC becomes equal to or greater than the lower limit Sl at the start of driving, charging of the storage device 7 may not be terminated. Instead, as shown by the dotted line in FIG. 7, the engine 1 may be stopped and charging of the storage device 7 may be terminated when the SOC reaches an upper limit Su. Also, when the SOC reaches an arbitrary value between the lower limit Sl at the start of driving and the upper limit Su, the engine 1 may be stopped and charging of the storage device 7 may be terminated. In this case, the arbitrary value may be a value several percent smaller than the upper limit Su.

In this embodiment, an electric heater 78 is provided upstream of the SCR catalyst 74 and is integrated with the SCR catalyst 74, and the SCR catalyst 74 is configured as an EHC, but instead of or in addition to the SCR catalyst 74, the oxidation catalyst 70 may be configured as an EHC.

In this embodiment, a diesel engine has been described as the engine 1, but the engine 1 may also be a gasoline engine (spark ignition engine). In this case, a three-way catalyst provided in the exhaust passage of the gasoline engine may be configured as the EHC.

In this embodiment, a series hybrid vehicle has been described as the hybrid vehicle V. However, the hybrid vehicle V may also be, for example, a series-parallel type hybrid vehicle in which the first MG2 and the second MG3 are connected by a power split mechanism formed of a planetary gear device.

The following are examples of embodiments of the present disclosure.
1) A hybrid vehicle (V) that is equipped with a hybrid system (10) including a traction motor (3), a power storage device (7) that supplies power to the traction motor (3), a generator (2) that is driven by an internal combustion engine (1) and generates power to be supplied to the power storage device (7), and a control device (100), and that is capable of EV running by running on the power of the traction motor (3) with the internal combustion engine (1) stopped, wherein the internal combustion engine (1) is equipped with an electrically heated catalyst (74, 78) that can be heated by the power of the power storage device (7), and the control device A hybrid vehicle (100) is configured to operate an internal combustion engine (7) to charge an electric storage device (7) until the SOC reaches or exceeds a predetermined value when the hybrid system (10) is stopped, and then to stop the internal combustion engine (1), if the SOC of the electric storage device (7) falls below a predetermined value, the predetermined value being an SOC that allows an electric heating catalyst (74, 78) to be heated until the temperature of the electric heating catalyst (74, 78) reaches an activation temperature when the hybrid system (10) is started, and that enables EV driving.

2) In 1, when the hybrid system (10) is stopped and the SOC of the power storage device (7) falls below a predetermined value, the internal combustion engine (7) is operated to charge the power storage device (7) until the SOC reaches an upper limit value, and then the internal combustion engine (1) is stopped.

3) In 2, the upper limit of the SOC is the value at which the deterioration of the storage device (7) progresses rapidly.
The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims.

1 engine, 2 first motor generator (first MG), 3 second motor generator (second MG), 4 first inverter, 5 second inverter, 6 boost converter, 7 power storage device, 7a monitoring unit, 8 drive wheels, 9 step-down converter, 10 engine body, 12 cylinder, 14 fuel injection valve, 20 intake passage, 22 air cleaner, 24 intercooler, 26 intake throttle valve, 28 intake manifold, 30 electric supercharger, 32 compressor, 34 motor, 40 electric air pump, 50 exhaust manifold, 52 exhaust passage, 70 oxidation catalyst, 72 DPF, 74 selective reduction catalyst (SCR catalyst), 76 oxidation catalyst, 78 electric heater, 80 urea addition valve, 82 urea water tank, 100 HV-ECU, 110 BAT-ECU, 120 Various sensors, 121 power switch, 122 catalyst temperature sensor, 130 communication device, 140 navigation device, 150 HMI device, 200 E/G-ECU, 500 server, H hybrid system, V hybrid vehicle.

Claims (4)

A hybrid vehicle that is capable of EV running by running on power from the traction motor while the internal combustion engine is stopped, the hybrid system including a traction motor, a power storage device that supplies power to the traction motor, a generator that is driven by an internal combustion engine and generates power to be supplied to the power storage device, and a control device,
the internal combustion engine includes an electrically heated catalyst that can be heated by the electric power of the power storage device;
the control device is configured to, when the hybrid system is stopped, operate the internal combustion engine to charge the power storage device until the SOC becomes equal to or greater than the predetermined value, and then stop the internal combustion engine if an SOC of the power storage device falls below a predetermined value;
the predetermined value is an SOC that allows the electrically heated catalyst to be heated until the temperature of the electrically heated catalyst reaches an activation temperature when the hybrid system is started, and allows the EV driving to be performed;
the internal combustion engine includes an electric supercharger driven by electric power from the power storage device,
The control device is configured to heat the electrically heated catalyst until the temperature of the electrically heated catalyst reaches an activation temperature when the hybrid system is started, and to drive the electric supercharger when the EV driving is being performed. A hybrid vehicle that is capable of EV running by running on power from the traction motor while the internal combustion engine is stopped, the hybrid system including a traction motor, a power storage device that supplies power to the traction motor, a generator that is driven by an internal combustion engine and generates power to be supplied to the power storage device, and a control device,
the internal combustion engine includes an electrically heated catalyst that can be heated by the electric power of the power storage device;
the control device is configured to, when the hybrid system is stopped, operate the internal combustion engine to charge the power storage device until the SOC becomes equal to or greater than the predetermined value, and then stop the internal combustion engine if an SOC of the power storage device falls below a predetermined value;
the predetermined value is an SOC that allows the electrically heated catalyst to be heated until the temperature of the electrically heated catalyst reaches an activation temperature when the hybrid system is started, and allows the EV driving to be performed;
the internal combustion engine includes an air pump that supplies air to an exhaust passage upstream of the electrically heated catalyst;
The control device is configured to heat the electrically heated catalyst until the temperature of the electrically heated catalyst reaches an activation temperature when the hybrid system is started, and to drive the air pump when the EV driving is performed. 3. The hybrid vehicle according to claim 1, wherein the control device is configured to heat the electrically heated catalyst until the temperature of the electrically heated catalyst reaches an activation temperature when the hybrid system is started, and to limit the output of the traction electric motor when the EV driving is being performed . 4. The hybrid vehicle according to claim 3 , wherein the control device is configured to limit the output of the traction motor when an SOC of the power storage device becomes equal to or lower than an output limit threshold.

Images