WO2015159218A2

WO2015159218A2 - Hybrid vehicle and control method for hybrid vehicle

Info

Publication number: WO2015159218A2
Application number: PCT/IB2015/052712
Authority: WO
Inventors: Tomoaki Honda; Toshio Inoue; Keita Fukui; Hidekazu NAWATA; Yuta NIWA; Taichi OHSAWA
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2014-04-16
Filing date: 2015-04-14
Publication date: 2015-10-22
Anticipated expiration: 2016-10-16
Also published as: WO2015159218A3; JP2015202832A

Abstract

A hybrid vehicle includes an engine, an exhaust passage, a filter, an electrical storage device, a driving apparatus and an ECU. The exhaust passage is connected to the engine. The filter is configured to trap particulate matter flowing through the exhaust passage. The electrical storage device is configured to be charged when the engine is in operation. The driving apparatus is configured to generate a driving force of the hybrid vehicle by using an electric power of the electrical storage device. The ECU is configured to control a charge/discharge amount of the electrical storage device such that a state of charge of the electrical storage device falls within a control range. The ECU is configured to expand the control range such that the control range at the time when regeneration of the filter is required is wider than the control range at the time when regeneration of the filter is not required, reduce the state of charge toward a lower limit value of the control range, and then increase the state of charge toward an upper limit value of the control range.

Description

HYBRID VEHICLE AND CONTROL METHOD FOR HYBRID VEHICLE

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to a hybrid vehicle, which includes a filter that traps particulate matter flowing through an exhaust passage of an engine and an electrical storage device that is charged when the engine is in operation, and a control method for the hybrid vehicle.

2. Description of Related Art

[0002] There is known a hybrid vehicle on which an internal combustion engine and an electric motor are mounted. The internal combustion engine is, for example, a gasoline engine or a diesel engine. Exhaust gas from these engines contains particulate matter (PM). Therefore, a filter, such as a diesel particulate filter (DPF) and a gasoline particulate filter (GPF), may be installed in an exhaust passage of each of the engines for the purpose of reducing the PM.

[0003] When PM accumulates in these filters, exhaust resistance increases. Therefore, regeneration control for burning PM accumulated in the filters is executed by utilizing exhaust heat, or the like, at appropriate timing. As such regeneration control, Japanese Patent Application Publication No. 2005-090259 (JP 2005-090259 A) describes a controller for an internal combustion engine. The controller increases the output of the engine when regeneration control over a filter is being executed, and causes an electrical storage device to be able to be charged with an electric power corresponding to the increase in the output.

SUMMARY OF THE INVENTION

[0004] Incidentally, when the state of charge of the electrical storage device to be charged is high at the time when the engine is in operation, the state of charge of the electrical storage device can reach the upper limit of a control range of the state of charge before the temperature of the filter becomes a temperature suitable for regeneration. At this time, it may not be possible to ensure the operating time of the engine, which is required to increase the temperature of the filter.

[0005] The invention provides a hybrid vehicle that quickly regenerates a filter by ensuring the operating time of an engine, which is required to increase the temperature of the filter, and a control method for the hybrid vehicle.

[0006] An aspect of the invention provides a hybrid vehicle. The hybrid vehicle includes an engine, an exhaust passage, a filter, an electrical storage device, a driving apparatus and an ECU. The exhaust passage is connected to the engine. The filter is configured to trap particulate matter flowing through the exhaust passage. The electrical storage device is configured to be charged when the engine is in operation. The driving apparatus is configured to generate a driving force of the hybrid vehicle by using an electric power of the electrical storage device. The ECU is configured to control a charge/discharge amount of the electrical storage device such that a state of charge of the electrical storage device falls within a control range. The ECU is configured to expand the control range such that the control range at the time when regeneration of the filter is required is wider than the control range at the time when regeneration of the filter is not required, increase the state of charge toward a lower limit value of the control range, and then increase the state of charge toward an upper limit value of the control range.

[0007] With this configuration, when regeneration of the filter is required, the control range of the state of charge is expanded, and the state of charge is reduced toward the lower limit value of the control range. Thus, even when the electrical storage device is charged during operation of the engine thereafter, it is possible to extend the operating time of the engine such that the operating time is longer than the operating time of the engine at the time when the state of charge is not reduced. Therefore, it is possible to ensure the operating time of the engine, which is required to increase the temperature of the filter.

[0008] In the above aspect, the ECU may be configured to expand the control range by increasing the upper limit value such that the upper limit value at the time when regeneration of the filter is required is higher than the upper limit value at the time when regeneration of the filter is not required and reducing the lower limit value such that the lower limit value at the time when regeneration of the filter is required is lower than the lower limit value at the time when regeneration of the filter is not required, and the ECU may be configured to reduce the state of charge such that the state of charge is lower than the lower limit value at the time when regeneration of the filter is not required, and then increase the state of charge such that the state of charge is higher than the upper limit value at the time when regeneration of the filter is not required.

[0009] With this configuration, it is possible to reduce the state of charge at the time when regeneration of the filter is required such that the state of charge is lower than the lower limit value at the time when regeneration of the filter is not required. Therefore, even when the electrical storage device is charged during operation of the engine thereafter, it is possible to extend the operating time of the engine such that the operating time is longer than the operating time of the engine at the time when the state of charge is not reduced or the operating time of the engine at the time when the control range is not expanded. Therefore, it is possible to ensure the operating time of the engine, which is required to increase the temperature of the filter.

[0010] In the above aspect, the ECU may be configured to control the charge/discharge amount such that the electrical storage device is discharged when the state of charge is a value between a control reference value within the control range and the upper limit value and the electrical storage device is charged when the state of charge is a value between the control reference value and the lower limit value. The ECU may be configured to reduce the reference value at the time when regeneration of the filter is required such that the reference value is lower than the lower limit value at the time when regeneration of the filter is not required, and then increase the reference value such that the reference value is higher than the upper limit value at the time when regeneration of the filter is not required.

[0011] With this configuration, it is possible to reduce the state of charge at the time when regeneration of the filter is required such that the state of charge is lower than the lower limit value at the time when regeneration of the filter is not required, and then it is possible to increase the state of charge such that the state of charge is higher than the upper limit value at the time when regeneration of the filter is not required.

[0012] In the above aspect, the driving apparatus may include a rotary electric machine. The rotary electric machine may be connected to an output shaft of the engine. The ECU may be configured to, when the state of charge is increased toward the upper limit value, execute fuel cut control and motoring control when the state of charge exceeds a threshold. The fuel cut control is control for stopping fuel injection of the engine. The motoring control is control for rotating the output shaft with the use of the rotary electric machine.

[0013] With this configuration, when the state of charge exceeds the threshold, it is possible to supply air containing oxygen to the filter by executing the motoring control.

Therefore, it is possible to facilitate burning of particulate matter in the filter.

[0014] In the above aspect, the ECU may be configured to execute the motoring control until regeneration of the filter completes.

[0015] With this configuration, it is possible to execute the motoring control until regeneration of the filter completes. Therefore, it is possible to remove particulate matter that accumulates in the filter.

[0016] Another aspect of the invention provides a control method for a hybrid vehicle. The hybrid vehicle includes an engine, an exhaust passage, a filter, an electrical storage device, a driving apparatus and an ECU. The exhaust passage is connected to the engine. The filter is configured to trap particulate matter flowing through the exhaust passage. The electrical storage device is configured to be charged when the engine is in operation. The driving apparatus is configured to generate a driving force of the hybrid vehicle by using an electric power of the electrical storage device. The control method includes controlling, by the ECU, a charge/discharge amount of the electrical storage device such that a state of charge of the electrical storage device falls within a control range; expanding, by the ECU, the control range such that the control range at the time when regeneration of the filter is required is wider than the control range at the time when regeneration of the filter is not required; and reducing, by the ECU, the state of charge toward a lower limit value of the expanded control range, and then increasing, by the ECU, the state of charge toward an upper limit value of the expanded control range.

[0017] According to the invention, by expanding the control range of the state of charge and reducing the state of charge toward the lower limit value of the control range, even when the electrical storage device is charged during operation of the engine thereafter, it is possible to extend the operating time of the engine such that the operating time is longer than the operating time of the engine at the time when the state of charge is not reduced. Therefore, it is possible to ensure the operating time of the engine, which is required to increase the temperature of the filter. Thus, it is possible to provide a hybrid vehicle that quickly regenerates the filter by ensuring the operating time of the engine, which is required to increase the temperature of the filter, and a control method for the hybrid vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is an overall block diagram of a vehicle;

FIG. 2 is a graph that shows the correlation between an SOC and a required charge/discharge power;

FIG. 3 is a functional block diagram of an ECU;

FIG. 4 is a graph that shows the correlation between an SOC and a required charge/discharge power in the case where a control reference value is changed;

FIG. 5 is a flowchart that shows a control process that is executed by the ECU; and FIG. 6 is a timing chart that shows the operation of the ECU.

DETAILED DESCRIPTION OF EMBODIMENTS

[0019] Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. In the following description, like reference numerals denote the same components. The names and functions of the corresponding components are also the same. Thus, the detailed description of the corresponding components will not be repeated.

[0020] The overall block diagram of a hybrid vehicle 1 (hereinafter, simply referred to as vehicle 1) according to the present embodiment will be described with reference to FIG. 1. The vehicle 1 includes a transmission 8, an engine 10, a drive shaft 17, a power control unit (PCU) 60, a battery 70, drive wheels 72, and an electronic control unit (ECU) 200.

[0021] The transmission 8 includes an output shaft 16, a first motor generator (hereinafter, referred to as first MG) 20, a second motor generator (hereinafter, referred to as second MG) 30, a power split device 40, and a reduction gear 58. In the present embodiment, the transmission 8 corresponds to a driving apparatus that generates the driving force of the vehicle 1 by using the electric power of the battery 70.

[0022] The engine 10 includes a plurality of cylinders 112. One end of an exhaust passage 80 is connected to the engine 10. The other end of the exhaust passage 80 is connected to a muffler (not shown). A catalyst 82 and a filter 84 are provided in the exhaust passage 80.

[0023] An engine rotation speed sensor 11, a wheel speed sensor 14, an air- fuel ratio sensor 86, an oxygen sensor 88, an upstream-side pressure sensor 90, a downstream-side pressure sensor 92, a current sensor 152, a voltage sensor 154, a battery temperature sensor 156 and a pedal stroke sensor 162 are connected to the ECU 200 so that the ECU 200 is able to receive various signals from the sensors.

[0024] The thus configured vehicle 1 moves by using a driving force that is output from at least one of the engine 10 or the second MG 30. Power that is generated by the engine 10 is split by the power split device 40 into two paths. One of the two paths is a path through which power is transmitted to the drive wheels 72 via the reduction gear 58. The other one of the two paths is a path through which power is transmitted to the first MG 20.

[0025] The first MG 20 and the second MG 30 each are, for example, a three-phase alternating-current rotary electric machine. The first MG 20 and the second MG 30 are driven by the PCU 60.

[0026] The first MG 20 has the function of a generator (power generating device) that generates electric power by using power split from the power of the engine 10 by the power split device 40 and then charges the battery 70 via the PCU 60. The first MG 20 rotates a crankshaft upon reception of electric power from the battery 70. The crankshaft is an output shaft of the engine 10. Thus, the first MG 20 has the function of a starter that starts up the engine 10.

[0027] The second MG 30 has the function of a drive motor that provides a driving force to the drive wheels 72 by using at least one of electric power stored in the battery 70 or electric power generated by the first MG 20. The second MG 30 has the function of a generator for charging the battery 70 via the PCU 60 by using electric power generated by regenerative braking.

[0028] The engine 10 is a gasoline engine, and is controlled on the basis of a control signal SI from the ECU 200.

[0029] The engine rotation speed sensor 11 is provided at a location at which the engine rotation speed sensor 11 faces the crankshaft of the engine 10. The engine rotation speed sensor 11 detects the rotation speed Ne of the engine 10. The engine rotation speed sensor 11 transmits a signal indicating the detected rotation speed Ne of the engine 10 to the ECU 200.

[0030] In the present embodiment, the engine 10 includes the four cylinders 112, that is, the first cylinder to the fourth cylinder. An ignition plug (not shown) is provided at a top portion inside each of the plurality of cylinders 112.

[0031] The engine 10 is not limited to an in-line four-cylinder engine as shown in

FIG. 1. For example, the engine 10 may be an engine of any type, formed of a plurality of cylinders or a plurality of banks, such as an in-line three-cylinder engine, a V six-cylinder engine, a V eight-cylinder engine, an in-line six-cylinder engine, a horizontally-opposed four-cylinder engine and a horizontally-opposed six cylinder engine.

[0032] The engine 10 includes fuel injection devices (not shown) corresponding to the plurality of cylinders 112. The fuel injection devices may be respectively provided in the plurality of cylinders 112 or may be respectively provided in intake ports of the cylinders.

[0033] In the thus configured engine 10, the ECU 200 controls a fuel injection amount to each of the plurality of cylinders 112 by injecting fuel in an appropriate amount at appropriate timing to each of the plurality of cylinders 112 or stopping injection of fuel to each of the plurality of cylinders 112.

[0034] The catalyst 82 provided in the exhaust passage 80 oxidizes unburned components contained in exhaust gas that is emitted from the engine 10, or reduces oxidized components.

[0035] The filter 84 is arranged at a location downstream of the catalyst 82 in the exhaust passage 80. The filter 84 is a GPF. The filter 84 may have a similar function to that of the catalyst 82. In such a case, the catalyst 82 may be omitted. The filter 84 may be arranged at a location upstream of the catalyst 82 in the exhaust passage 80. The filter 84 traps particulate matter (PM) contained in exhaust gas. Trapped PM accumulates in the filter 84.

[0036] The air-fuel ratio sensor 86 is provided at a location upstream of the catalyst 82 in the exhaust passage 80. The oxygen sensor 88 is provided at a location downstream of the catalyst 82 and upstream of the filter 84 in the exhaust passage 80.

[0037] The air-fuel ratio sensor 86 is used to detect the air-fuel ratio of air-fuel mixture, that is, a mixture of fuel and air, which is supplied to each of the plurality of cylinders 112. The air-fuel ratio sensor 86 detects the air-fuel ratio in exhaust gas, and transmits a signal indicating the detected air-fuel ratio to the ECU 200.

[0038] The oxygen sensor 88 is used to detect the concentration of oxygen in air-fuel mixture, that is, a mixture of fuel and air, which is supplied to each of the plurality of cylinders 112. The oxygen sensor 88 detects the concentration of oxygen in exhaust gas, and transmits a signal indicating the detected concentration of oxygen to the ECU 200. The ECU 200 calculates the air-fuel ratio on the basis of the received signal.

[0039] The upstream-side pressure sensor 90 is provided at a location upstream of the filter 84 and downstream of the oxygen sensor 88 in the exhaust passage 80. The downstream-side pressure sensor 92 is provided at a location downstream of the filter 84 in the exhaust passage 80.

[0040] Each of the upstream-side pressure sensor 90 and the downstream-side pressure sensor 92 is used to detect the pressure in the exhaust passage 80. The upstream-side pressure sensor 90 transmits a signal (first pressure detection signal) indicating the detected pressure in the exhaust passage 80 (upstream-side pressure) to the ECU 200. The downstream-side pressure sensor 92 transmits a signal (second pressure detection signal) indicating the detected pressure in the exhaust passage 80 (downstream-side pressure) to the ECU 200.

[0041] The power split device 40 is configured to be able to split power, which is generated by the engine 10, into a path toward the drive shaft 17 via the output shaft 16 and a path toward the first MG 20. The power split device 40 may be formed of a planetary gear train. The planetary gear train includes three rotary shafts, that is, a sun gear, a planetary gear and a ring gear. For example, the rotor of the first MG 20 is connected to the sun gear, the output shaft of the engine 10 is connected to the planetary gear, and the output shaft 16 is connected to the ring gear. Thus, the engine 10, the first MG 20 and the second MG 30 are mechanically connected to the power split device 40.

[0042] The output shaft 16 is also connected to the rotor of the second MG 30. The output shaft 16 is mechanically connected to the drive shaft 17 via the reduction gear 58. The drive shaft 17 is used to rotationally drive the drive wheels 72. A transmission may be further assembled between the rotary shaft of the second MG 30 and the output shaft 16.

[0043] The PCU 60 converts direct-current power, which is supplied from the battery 70, to alternating-current power, and drives the first MG 20 and the second MG 30. The PCU 60 converts alternating-current power, generated by the first MG 20 or the second MG 30, to direct-current power, and charges the battery 70. For example, the PCU 20 includes an inverter (not shown) and a converter (not shown). The inverter is used to convert between direct-current power and alternating-current power. The converter is used to convert direct-current voltage between a direct-current link side of the inverter and the battery 70.

[0044] The battery 70 is an electrical storage device, and is a rechargeable direct-current power supply. The battery 70 includes, for example, a nickel-metal hydride secondary battery or a lithium ion secondary battery. Not only the battery 70 is charged with electric power generated by the first MG 20 and/or the second MG 30 as described above but also the battery 70 may be charged with electric power that is supplied from an external power supply (not shown). The battery 70 is not limited to a secondary battery. The battery 70 may be the one that is able to generate direct-current voltage, and may be, for example, a capacitor, a solar cell, a fuel cell, or the like.

[0045] The current sensor 152, the voltage sensor 154 and the battery temperature sensor 156 are provided at the battery 70. The current sensor 152 detects the current IB of the battery 70. The current sensor 152 transmits a signal indicating the current IB to the ECU 200. The voltage sensor 154 detects the voltage VB of the battery 70. The voltage sensor 154 transmits a signal indicating the voltage VB to the ECU 200. The battery temperature sensor 156 detects the battery temperature TB of the battery 70. The battery temperature sensor 156 transmits a signal indicating the battery temperature TB to the ECU 200.

[0046] The ECU 200 estimates a state of charge (hereinafter, referred to as SOC) of the battery 70 on the basis of the current IB, voltage VB and battery temperature TB of the battery 70. The ECU 200 may estimate an open circuit voltage (OCV) on the basis of, for example, the current, the voltage and the battery temperature and then estimate the SOC of the battery 70 on the basis of the estimated OCV and a predetermined map. Alternatively, the ECU 200 may estimate the SOC of the battery 70 by, for example, integrating a charge current of the battery 70 and a discharge current of the battery 70.

[0047] The wheel speed sensor 14 detects the rotation speed Nw of one of the drive wheels 72. The wheel speed sensor 14 transmits a signal indicating the detected rotation speed Nw to the ECU 200. The ECU 200 calculates a vehicle speed V on the basis of the received rotation speed Nw. The ECU 200 may calculate the vehicle speed V on the basis of the rotation speed of the second MG 30 instead of the rotation speed Nw.

[0048] An accelerator pedal 160 is provided at a driver seat. The pedal stroke sensor 162 is provided at the accelerator pedal 160. The pedal stroke sensor 162 detects a stroke (depression amount) AP of the accelerator pedal 160. The pedal stroke sensor 162 transmits a signal indicating the stroke AP to the ECU 200. Instead of the pedal stroke sensor 162, an accelerator pedal depression force sensor may be used. The accelerator pedal depression force sensor is used to detect the depression force exerted on the accelerator pedal 160 by an occupant of the vehicle 1.

[0049] The ECU 200 generates a control signal SI for controlling the engine 10, and outputs the generated control signal SI to the engine 10. The ECU 200 generates a control signal S2 for controlling the PCU 60, and outputs the generated control signal S2 to the PCU 60.

[0050] The ECU 200 is a controller that controls an overall hybrid system, that is, the charge/discharge state of the battery 70 and the operating states of the engine 10, first

MG 20 and second MG 30, so that the vehicle 1 is able to operate at the highest efficiency through control over the engine 10, the PCU 60, and the like.

[0051] The ECU 200 calculates a required vehicle power corresponding to the stroke AP of the accelerator pedal 160 and the vehicle speed V. The accelerator pedal 160 is provided at the driver seat. In addition, the ECU 200 calculates a required charge/discharge power on the basis of the current SOC of the battery 70. The ECU 200 controls the torque of the first MG 20, the torque of the second MG 30 or the output of the engine 10 on the basis of the calculated required power and the calculated required charge/discharge power.

[0052] FIG. 2 shows the correlation between an SOC and a required charge/discharge power. In FIG. 2, the ordinate axis represents required charge/discharge power [KW], and the abscissa axis represents SOC.

[0053] The ECU 200 uses, for example, the map shown in FIG. 2, sets the required charge/discharge power such that the battery 70 is discharged when the current SOC of the battery 70 is a value between a control reference value SOC(0) within the control range and an upper limit value SOC_H of the control range, and sets the required charge/discharge power such that the battery 70 is charged when the current SOC of the battery 70 is a value between the control reference value SOC(0) and a lower limit value SOC_L of the control range.

[0054] In FIG. 2, the control reference value SOC(0) indicates the SOC at which the required charge/discharge power is zero. The upper limit value SOC_H indicates the SOC at which the required charge/discharge power is a maximum required value. The lower limit value SOC_L indicates the SOC at which the required charge/discharge power is a minimum required value. When the required charge/discharge power is a positive value, the required charge/discharge power indicates a required power on the discharge side. When the required charge/discharge power is a negative value, the required charge/discharge power indicates a required power on the charge side. [0055] The ECU 200 suppresses the charging of the battery 70 when the SOC of the battery 70 reaches the upper limit value SOC_H. The ECU 200 suppresses the discharging of the battery 70 when the SOC of the battery 70 reaches the lower limit value SOCJL.

[0056] Therefore, when the vehicle 1 is controlled on the basis of the required vehicle power and the required charge/discharge power, the SOC of the battery 70 is controlled so as to change within the range between the upper limit value SOC H and the lower limit value SOC_L with respect to the control reference value SOC(0) as the center.

[0057] In the above-described configuration, in the case where regeneration of the filter 84 is required, when the temperature Tf of the filter 84 is lower than a temperature range suitable for regeneration (hereinafter, also referred to as regeneratable temperature range), the temperature of the filter 84 is required to be increased by operating the engine 10 until the temperature of the filter 84 falls within the regeneratable temperature range.

[0058] However, when the SOC of the battery 70 to be charged is high at the time when the engine 10 is in operation, the SOC of the battery 70 may reach the upper limit of the control range before the temperature Tf of the filter 84 falls within the regeneratable temperature range, and it may not be able to ensure the operating time of the engine 10, which is required to increase the temperature of the filter 84.

[0059] Therefore, in the present embodiment, the ECU 200 expands the control range of the SOC of the battery 70 such that the control range at the time when regeneration of the filter 84 is required is wider than the control range before regeneration of the filter 84 is required, reduces the SOC toward the lower limit value of the expanded control range and then increases the SOC toward the upper limit value of the expanded control range.

[0060] In the present embodiment, when regeneration of the filter 84 is required, the ECU 200 sets an upper limit value SOC_H' by increasing the upper limit value SOC_H of the control range of the SOC, and sets a lower limit value SOC_L' by reducing the lower limit value SOCJL. The ECU 200 expands the control range of the SOC in this way. In addition, the ECU 200 reduces the SOC until the SOC becomes lower than a threshold A lower than the lower limit value SOCJL, and increases the SOC until the SOC becomes a threshold B higher than the upper limit value SOC H.

[0061] When the SOC becomes higher than the threshold B, the ECU 200 executes fuel cut control for stopping fuel injection of the engine 10, and executes motoring control for rotating the output shaft of the engine 10 with the use of the first MG 20. The ECU 200 executes motoring control until regeneration of the filter 84 completes.

[0062] FIG. 3 shows the functional block diagram of the ECU 200 mounted on the vehicle 1 according to the present embodiment. The ECU 200 includes a regeneration request determination unit 202, a control range change unit 204, an SOC control unit 206, a fuel cut control unit 208, a motoring control unit 210, and a regeneration completion determination unit 212.

[0063] The regeneration request determination unit 202 determines whether regeneration of the filter 84 is required. When PM has accumulated in the filter 84 to such an extent that overtemperature (OT) is not caused through burning of the PM, the regeneration request determination unit 202 determines that regeneration of the filter 84 is required. In the present embodiment, the regeneration request determination unit 202 determines, by using the upstream-side pressure sensor 90 and the downstream-side pressure sensor 92, whether regeneration of the filter 84 is required.

[0064] Specifically, when the difference between the upstream-side pressure detected by the upstream-side pressure sensor 90 and the downstream-side pressure detected by the downstream-side pressure sensor 92 is larger than a threshold, the regeneration request determination unit 202 determines that regeneration of the filter 84 is required. The threshold is used to estimate that the amount of PM accumulated in the filter 84 is larger than or equal to a predetermined amount. The threshold may be a predetermined value adapted through an experiment or a design or may be a value that changes with the operating state or operation history of the engine 10.

[0065] A method of determining whether regeneration of the filter 84 is required is not limited to the above-described method that uses the upstream-side pressure sensor 90 and the downstream-side pressure sensor 92. For example, the method may be the following method. The ECU 200 estimates the temperature of the filter 84 by utilizing various sensors, such as the air-fuel ratio sensor 86, the oxygen sensor 88, an air flow meter, a throttle opening degree sensor and a coolant temperature sensor. Alternatively, the ECU 200 estimates the amount of PM accumulated in the filter 84 from an operation history, operating time, decrease in output, or the like, of the engine 10, and, when the estimated amount of PM accumulated is larger than a predetermined amount, determines that regeneration of the filter 84 is required.

[0066] When the regeneration request determination unit 202 determines that regeneration of the filter 84 is required, the control range change unit 204 executes the process of changing the control range of the SOC. Specifically, the control range change unit 204 obtains a value SOC_H' by increasing the upper limit value SOC H of the SOC by a predetermined value ASOC H, and sets the obtained value SOC_H' as a new upper limit value. In addition, the control range change unit 204 obtains a value SOCJL' by reducing the lower limit value SOCJL of the SOC by a predetermined value ASOCJL, and sets the obtained value SOC_L' as a new lower limit value. The increment ASOC H of the upper limit value SOC_H of the SOC may be different from the decrement ASOC_L of the lower limit value SOC L of the SOC or may be the same as the decrement ASOC_L of the lower limit value SOC L of the SOC.

[0067] When regeneration of the filter 84 has completed, the control range change unit 204 returns the upper limit value of the control range of the SOC to the SOC_H, and returns the lower limit value of the control range of the SOC to the SOC L.

[0068] When the process of changing the control range of the SOC is executed by the control range change unit 204, the SOC control unit 206 changes the control reference value from the SOC(0) to a value SOC(l) between the lower limit value SOC L and the lower limit value SOC_L'. When the control reference value is changed from the SOC(0) to the SOC(l), the correlation between an SOC and a required charge/discharge power is changed from the correlation indicated by the continuous line in FIG. 4 to the correlation indicated by the dashed line in FIG. 4.

[0069] Therefore, on the basis of the correlation indicated by the dashed line in FIG. 4, the SOC control unit 206 sets the required charge/discharge power such that the battery 70 is discharged when the current SOC of the battery 70 is a value between the control reference value SOC(l) and the upper limit value SOC_H', and sets the required charge/discharge power such that the battery 70 is charged when the current SOC of the battery 70 is a value between the control reference value SOC(l) and the lower limit value SOC_L'. Therefore, when the vehicle 1 is controlled on the basis of the required vehicle power and the required charge/discharge power, the SOC of the battery 70 is controlled so as to decrease toward the control reference value SOC(l).

[0070] When the current SOC of the battery 70 is smaller than the threshold A, the SOC control unit 206 changes the control reference value from the SOC(l) to a value SOC(2) between the upper limit values SOC_H, SOC H'. When the control reference value is changed from the SOC(l) to the SOC(2), the correlation between an SOC and a required charge/discharge power is changed from the correlation indicated by the dashed line in FIG. 4 to the correlation indicated by the alternate long and short dashed line in FIG. 4. The threshold A just needs to be a value lower than the not-yet-changed lower limit value SOCJL The threshold A may be, for example, the same value as the SOC(l), a value higher than the SOC(l) or a value lower than the SOC(l).

[0071] Therefore, on the basis of the correlation indicated by the alternate long and short dashed line in FIG. 4, the SOC control unit 206 sets the required charge/discharge power such that the battery 70 is discharged when the current SOC of the battery 70 is a value between the control reference value SOC(2) and the upper limit value SOC_H', and sets the required charge/discharge power such that the battery 70 is charged when the current SOC of the battery 70 is a value between the control reference value SOC(2) and the lower limit value SOCJL'. Therefore, when the vehicle 1 is controlled on the basis of the required vehicle power and the required charge/discharge power, the SOC of the battery 70 is controlled so as to increase toward the control reference value SOC(2).

[0072] When regeneration of the filter 84 has completed, the SOC control unit 206 returns the control reference value to the SOC(0).

[0073] When the SOC of the battery 70 is higher than the threshold B, the fuel cut control unit 208 executes fuel cut control for stopping fuel injection in the engine 10. The threshold B just needs to be a value higher than the not-yet-changed upper limit value SOC_H. The threshold B may be, for example, the same value as the SOC(2), a value higher than the SOC(2) or a value lower than the SOC(2). In this way, the thresholds A, B are set such that the range of the SOC, having the threshold A as the lower limit value and the threshold B as the upper limit value, is at least wider than the control range between the not-yet-changed lower limit value SOCJL and the not-yet-changed upper limit value SOC H. The thresholds A, B are set such that, when the SOC changes from the threshold A to the threshold B, degradation of the battery 70 is not facilitated. In addition, the thresholds A, B are set such that the temperature of the filter 84 is increased so as to fall within the regeneratable temperature range owing to the operating heat of the engine 10 before motoring control is executed as a result of a change in the SOC from the threshold A to the threshold B.

[0074] When the SOC of the battery 70 is higher than the threshold B or together with execution of fuel cut control by the fuel cut control unit 208, the motoring control unit 210 executes motoring control for rotating the crankshaft of the engine 10 with the use of the first MG 20.

[0075] The motoring control unit 210 controls the first MG 20 so that the rotation speed Ne of the engine 10 becomes a predetermined rotation speed. The rotation speed of the engine 10, which provides the amount of air at which the temperature of the filter 84 does not exceed an upper limit temperature of the filter 84, is set as the predetermined rotation speed. The motoring control unit 210 continues motoring control until regeneration of the filter 84 completes, and ends motoring control when regeneration of the filter 84 completes.

[0076] The regeneration completion determination unit 212 determines whether regeneration of the filter 84 has completed. The regeneration completion determination unit 212 determines, by using the upstream-side pressure sensor 90 and the downstream-side pressure sensor 92, whether regeneration of the filter 84 has completed.

[0077] Specifically, when the difference between the upstream-side pressure detected by the upstream-side pressure sensor 90 and the downstream-side pressure detected by the downstream-side pressure sensor 92 is smaller than a threshold, the regeneration completion determination unit 212 determines that regeneration of the filter 84 has completed.

[0078] The threshold that is used to determine whether regeneration of the filter 84 has completed may be a predetermined value that is adapted by an experiment or a design or may be a value that changes with the operating state of the engine 10.

[0079] The threshold that is used to determine whether regeneration of the filter

84 has completed may be the same value as the threshold that is used to determine whether regeneration of the filter 84 is required or may be smaller than the threshold that is used to determine whether regeneration of the filter 84 is required.

[0080] A control process that is executed by the ECU 200 mounted on the vehicle 1 according to the present embodiment will be described with reference to FIG. 5.

[0081] In step (hereinafter, step is abbreviated as "S") 100, the ECU 200 determines whether regeneration of the filter 84 is required. When it is determined that regeneration of the filter 84 is required (YES in SI 00), the process proceeds to SI 02. Otherwise (NO in SI 00), the process ends. The ECU 200 may, for example, set a regeneration request determination flag to an on state when regeneration of the filter 84 is required.

[0082] In SI 02, the ECU 200 executes the process of changing the control range of the SOC. Specifically, the ECU 200 expands the control range of the SOC by increasing the upper limit value SOC_H of the control range of the SOC to the upper limit value SOC_H' and reducing the lower limit value SOC_L of the control range of the SOC to the lower limit value SOCJL'. The ECU 200 may, for example, execute the process of changing the control range of the SOC when the regeneration request determination flag is in the on state.

[0083] In SI 04, the ECU 200 lowers the control reference value of the SOC from the SOC(0) to the SOC(l).

[0084] In SI 06, the ECU 200 determines whether the SOC of the battery 70 is lower than the threshold A. When it is determined that the SOC of the battery 70 is lower than the threshold A (YES in SI 06), the process proceeds to SI 08. Otherwise (NO in SI 06), the process is returned to SI 06. The ECU 200 may, for example, set a lower limit value reaching flag to an on state when it is determined that the SOC of the battery 70 is lower than the SOC(l).

[0085] In SI 08, the ECU 200 raises the control reference value of the SOC from the SOC(l) to the SOC(2). The ECU 200 may, for example, raise the control reference value of the SOC from the SOC(l) to the SOC(2) when the lower limit value reaching flag changes from an off state to the on state.

[0086] In SI 10, the ECU 200 determines whether the SOC of the battery 70 is higher than the threshold B. When it is determined that the SOC of the battery 70 is higher than the threshold B (YES in S 110), the process proceeds to S 112. Otherwise (N O in SI 10), the process is returned to SI 10. The ECU 200 may set an upper limit value reaching flag to an on state when it is determined that the SOC of the battery 70 is higher than the SOC(2).

[0087] In SI 12, the ECU 200 executes fuel cut control over the engine 10. The

ECU 200 may, for example, execute fuel cut control when the upper limit value reaching flag changes from an off state to the on state.

[0088] In SI 14, the ECU 200 executes motoring control for rotating the output shaft of the engine 10 with the use of the first MG 20. The ECU 200 may, for example, execute motoring control when the upper limit value reaching flag changes from the off state to the on state.

[0089] In S 116, the ECU 200 determines whether regeneration of the filter 84 has completed. When it is determined that regeneration of the filter 84 has completed (YES in SI 16), the process proceeds to SI 18. Otherwise (NO in SI 16), the process is returned to S116.

[0090] In SI 18, the ECU 200 returns to ordinary control. Specifically, the ECU 200 returns the upper limit value of the control range of the SOC from the SOC_H' to the SOC H, and returns the lower limit value of the control range of the SOC from the SOCJL' to the SOC_L. In addition, the ECU 200 lowers the control reference value of the SOC from the SOC(2) to the SOC(0). Furthermore, the ECU 200 stops fuel cut control and motoring control.

[0091] The operation of the ECU 200 mounted on the vehicle 1 according to the present embodiment based on the above-described structure and flowchart will be described with reference to FIG. 6.

[0092] For example, it is assumed that regeneration of the filter 84 is not required

(the regeneration request flag is in the off state). At this time, the required charge/discharge power is determined on the basis of the correlation between an SOC and a required charge/discharge power, indicated by the continuous line in FIG. 4, so the SOC (the continuous line (wide line) in FIG. 6) of the battery 70 changes with respect to the control reference value SOC(0) as the center (the alternate long and short dashed line (wide line) in FIG. 6). At this time, the SOC of the battery 70 is controlled within the control range between the SOC_H set as the upper limit value and the SOC_L set as the lower limit value.

[0093] At this time, the engine 10, for example, enters an operated state or enters a stopped state on the basis of the state of the vehicle 1 (ordinary control is executed). Therefore, the temperature Tf of the filter 84 is kept so as to be lower than a lower limit temperature Tf(0) of the PM regeneratable temperature range. [0094] At time t(0), when regeneration of the filter 84 is required because of the fact that the difference between the upstream-side pressure and the downstream-side pressure becomes larger than the threshold, the regeneration request flag is set to the on state, and the process of changing the control range of the SOC is executed. Therefore, as indicated by the dashed line (narrow line) in FIG. 6, the upper limit value SOC_H of the control range of the SOC increases to the SOC_H', and the lower limit value SOC_L of the control range of the SOC is reduced to the SOC_L'. In addition, the control reference value of the SOC is lowered from the SOC(0) to the SOC(l). At this time, because the discharging of the battery 70 is required (because the required charge/discharge power is a positive value), the engine 10 enters a stopped state, and the vehicle 1 moves by using the power of the second MG 30 (moves in an EV mode).

[0095] As a result, from time t(0), the SOC of the battery 70 decreases toward the lowered control reference value SOC(l) of the SOC. When the SOC of the battery 70 becomes lower than the threshold A at time t(l), the control reference value of the SOC is lowered from the SOC(l) to the SOC(2) at time t(2). At this time, because the charging of the battery 70 is required (because the required charge/discharge power is a negative value), the engine 10 enters an operated state.

[0096] Therefore, from time t(2), the SOC of the battery 70 increases toward the control reference value SOC(2). At this time, because the engine 10 enters an operated state, the filter temperature Tf also increases by the exhaust heat of the engine 10. At time t(3), the temperature of the filter 84 becomes higher than or equal to a lower limit temperature Tf(0).

[0097] When the SOC of the battery 70 becomes higher than the threshold B at time t(4), fuel cut control is executed, and motoring control is executed. Because air containing oxygen is supplied through motoring control to the filter 84 of which the temperature is higher than or equal to the lower limit temperature Tf(0), burning of PM is facilitated in the filter 84. The temperature Tf of the filter 84 further increases as a result of facilitation of burning of PM. When the PM has been removed from the filter 84, the temperature Tf of the filter 84 starts decreasing.

[0098] When it is determined at time t(5) that regeneration of the filter has completed as a result of the fact that the difference between the upstream-side pressure and the downstream-side pressure becomes smaller than or equal to the threshold, the regeneration request flag is set to the off state, and the ECU 200 returns to ordinary control.

[0099] Therefore, the upper limit value of the control range of the SOC is returned from the SOC_H' to the SOC_H, and the lower limit value of the control range of the SOC is returned from the SOC L' to the SOC L. The control reference value of the SOC is lowered from the SOC(2) to the SOC(0).

[0100] In this way, the operating time of the engine 10 in the period from time t(2) to time t(4) is longer than the operating time of the engine 10 at the time when the SOC is increased to the threshold B from time t(0) (the period from time t(0) to time t(l)), indicated by the dashed line (wide line) in FIG. 6.

[0101] In this way, with the vehicle 1 according to the present embodiment, when regeneration of the filter 84 is required, the control range of the SOC of the battery 70 is expanded, and the SOC is reduced toward the lower limit value SOC L'. Thus, even when the battery 70 is charged during operation of the engine 10 thereafter, it is possible to extend the operating time of the engine 10 such that the operating time is longer than that when the SOC is not reduced. Therefore, it is possible to ensure the operating time of the engine 10, which is required to increase the temperature of the filter 84. Thus, it is possible to provide the hybrid vehicle that quickly regenerates the filter by ensuring the operating time of the engine, which is required to increase the temperature of the filter.

[0102] The SOC is reduced so as to be lower than the lower limit value SOC L at the time when regeneration of the filter 84 is not required. Thus, even when the battery 70 is charged during operation of the gasoline engine thereafter, it is possible to extend the operating time of the engine 10 such that the operating time is longer than that when the SOC of the battery 70 is not reduced or when the control range is not expanded.

[0103] When the SOC becomes higher than the threshold B, it is possible to supply air containing oxygen through motoring control to the filter 84 having a temperature higher than or equal to the lower limit temperature Tf(0) of the regeneratable temperature range. Thus, it is possible to facilitate burning of PM accumulated in the filter 84.

[0104] By executing motoring control until regeneration of the filter 84 completes, it is possible to remove PM that accumulates in the filter 84.

[0105] Alternative embodiments will be described below. In the present embodiment, the control range is expanded by increasing the upper limit value SOC_H of the control range of the SOC and reducing the lower limit value SOC L. Instead, for example, the control range may be expanded by reducing only the lower limit value

SOC_L of the control range of the SOC or the control range may be expanded by increasing only the upper limit value SOC_H.

[0106] In the present embodiment, when the SOC becomes higher than the threshold B, fuel cut control and motoring control are executed. Instead, for example, when the filter temperature Tf becomes higher than or equal to a threshold higher than the lower limit temperature Tf(0), fuel cut control and motoring control may be executed. In this case, the filter temperature Tf may be directly detected by a sensor, or the like, or may be estimated by utilizing detected results of various sensors.

[0107] In the present embodiment, the timing at which it is determined that the SOC is lower than the threshold A is different from the timing at which the control reference value is raised from the SOC(0) to the SOC(l). Instead, these timings may be the same timing.

[0108] In the present embodiment, when the SOC of the battery 70 becomes higher than the threshold B, motoring control is continuously executed until regeneration of the filter completes. Instead, for example, intermittent motoring control may be executed until regeneration of the filter completes. In the intermittent motoring control, rotation of the output shaft of the engine 10 with the use of the first MG 20 (hereinafter, referred to as motoring) is intermittently carried out by repeating a series of operations in which motoring is carried out until a first time elapses from when motoring is started and motoring is stopped until a second time elapses from when the first time has elapsed. With this configuration, it is possible to appropriately adjust the amount of air that is supplied to the filter 84.

[0109] In the present embodiment, power control for controlling the vehicle 1 on the basis of the required vehicle power and the required charge/discharge power is described as an example. Particularly, the vehicle 1 may be controlled by another output control (for example, torque control) instead of power control. All or part of the above-described alternative embodiments may be combined with each other.

[0110] The embodiments described above should be regarded as only illustrative in every respect and not restrictive. The scope of the invention is defined by the appended claims rather than the description of the above embodiments. The scope of the invention is intended to encompass all modifications within the scope of the appended claims and equivalents thereof.

Claims

CLAIMS:

1. A hybrid vehicle comprising:

an engine;

an exhaust passage connected to the engine;

a filter configured to trap particulate matter flowing through the exhaust passage; an electrical storage device configured to be charged when the engine is in operation; a driving apparatus configured to generate a driving force of the hybrid vehicle by using an electric power of the electrical storage device; and

an ECU configured to

control a charge/discharge amount of the electrical storage device such that a state of charge of the electrical storage device falls within a control range,

expand the control range such that the control range at the time when regeneration of the filter is required is wider than the control range at the time when regeneration of the filter is not required, and

reduce the state of charge toward a lower limit value of the control range and then increase the state of charge toward an upper limit value of the control range.

2. The hybrid vehicle according to claim 1, wherein

the ECU is configured to

expand the control range by increasing the upper limit value such that the upper limit value at the time when regeneration of the filter is required is higher than the upper limit value at the time when regeneration of the filter is not required and reducing the lower limit value such that the lower limit value at the time when regeneration of the filter is required is lower than the lower limit value at the time when regeneration of the filter is not required,

reduce the state of charge such that the state of charge is lower than the lower limit value at the time when regeneration of the filter is not required, and then

increase the state of charge such that the state of charge is higher than the upper limit value at the time when regeneration of the filter is not required.

3. The hybrid vehicle according to claim 2, wherein

the ECU is configured to

control the charge/discharge amount such that the electrical storage device is discharged when the state of charge is a value between a control reference value within the control range and the upper limit value and the electrical storage device is charged when the state of charge is a value between the control reference value and the lower limit value,

reduce the reference value at the time when regeneration of the filter is required such that the reference value is lower than the lower limit value at the time when regeneration of the filter is not required, and then

increase the reference value such that the reference value is higher than the upper limit value at the time when regeneration of the filter is not required.

4. The hybrid vehicle according to any one of claims 1 to 3, wherein

the driving apparatus includes a rotary electric machine, the rotary electric machine is connected to an output shaft of the engine, and

the ECU is configured to, when the state of charge is increased toward the upper limit value, execute fuel cut control and motoring control when the state of charge exceeds a threshold, the fuel cut control is control for stopping fuel injection of the engine, and the motoring control is control for rotating the output shaft with the use of the rotary electric machine.

5. The hybrid vehicle according to claim 4, wherein

the ECU is configured to execute the motoring control until regeneration of the filter completes.

6. A control method for a hybrid vehicle, the hybrid vehicle including an engine, an exhaust passage, a filter, an electrical storage device, a driving apparatus and an ECU, the exhaust passage being connected to the engine, the filter being configured to trap particulate matter flowing through the exhaust passage, the electrical storage device being configured to be charged when the engine is in operation, the driving apparatus being configured to generate a driving force of the hybrid vehicle by using an electric power of the electrical storage device, the control method comprising:

controlling, by the ECU, a charge/discharge amount of the electrical storage device such that a state of charge of the electrical storage device falls within a control range;

expanding, by the ECU, the control range such that the control range at the time when regeneration of the filter is required is wider than the control range at the time when regeneration of the filter is not required; and

reducing, by the ECU, the state of charge toward a lower limit value of the expanded control range, and then increasing, by the ECU, the state of charge toward an upper limit value of the expanded control range.