WO2015049565A1

WO2015049565A1 - Hybrid vehicle, controller for hybrid vehicle, and control method for hybrid vehicle

Info

Publication number: WO2015049565A1
Application number: PCT/IB2014/001934
Authority: WO
Inventors: Hidekazu NAWATA; Toshio Inoue; Tsukasa Abe; Tomoaki Honda; Keita Fukui; Yuta NIWA; Taichi OSAWA
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2013-10-04
Filing date: 2014-09-29
Publication date: 2015-04-09
Also published as: JP5854023B2; JP2015074233A

Abstract

A hybrid vehicle includes a gasoline engine, a filter, an electrical storage device, a converter, and a controller. The gasoline engine is configured to start up when driving force of the vehicle exceeds a start-up threshold. The filter is configured to trap particulate matter flowing through an exhaust passage of the gasoline engine. The converter is configured to convert power of the gasoline engine to electric power for charging the electrical storage device, and is configured to convert electric power of the electrical storage device to driving force of the vehicle. The controller is configured to, when regeneration of the filter is required, change the start-up threshold so that a state quantity of the electrical storage device changes in a direction opposite to a direction in which the state quantity varies as a result of execution of regeneration control, and execute the regeneration control when the state quantity changes into a predetermined range in which execution of the regeneration control is allowed. The regeneration control is executed when the filter is regenerated. The regeneration control is control so that a temperature of the filter increases to a regeneratable temperature. The state quantity indicates a state of charge of the electrical storage device.

Description

HYBRID VEHICLE, CONTROLLER FOR 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 including a filter that traps particulate matter flowing through an exhaust passage of a gasoline engine, a controller for the hybrid vehicle, 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), so a filter may be installed in an exhaust passage of each of the engines for the purpose of reducing the PM. These are, for example, a diesel particulate filter (DPF), a gasoline particulate filter (GPF), and the like.

[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 sets a battery so that the battery has a predetermined allowance in order for the battery to be charged with the amount of increase in the output of the engine.

SUMMARY OF THE INVENTION

[0004] Incidentally, in a gasoline engine, the amount of emission of PM is smaller than that of a diesel engine having a comparable output. Therefore, the frequency of executing regeneration control and the required response are lower than those of the diesel engine. Thus, when the battery is set so as to have a predetermined allowance for the purpose of executing regeneration control as in the case of JP 2005-090259 A, it is desirable to ensure the allowance that is set by placing importance on efficiency in a gasoline engine as compared to a diesel engine. [0005] The invention provides a hybrid vehicle that efficiently executes regeneration control over a filter, a controller for the hybrid vehicle, and a control method for the hybrid vehicle.

[0006] A first aspect of the invention provides a hybrid vehicle. The hybrid vehicle includes a gasoline engine, a filter, an electrical storage device, a converter, and a controller. The gasoline engine is configured to start up when driving force of the vehicle exceeds a start-up threshold. The filter is configured to trap particulate matter flowing through an exhaust passage of the gasoline engine. The converter is configured to convert power of the gasoline engine to electric power for charging the electrical storage device, and is configured to convert electric power of the electrical storage device to driving force of the vehicle. The controller is configured to, when regeneration of the filter is required, change the start-up threshold so that a state quantity of the electrical storage device changes in a direction opposite to a direction in which the state quantity varies as a result of execution of regeneration control, and execute the regeneration control when the state quantity changes into a predetermined range in which execution of the regeneration control is allowed. The regeneration control is executed when the filter is regenerated. The regeneration control is control so that a temperature of the filter increases to a regeneratable temperature. The state quantity indicates a state of charge of the electrical storage device.

[0007] In the above aspect, the regeneration control may be executed such that output of the gasoline engine when regeneration of the filter is required is higher than output of the gasoline engine when regeneration of the filter is not required. The predetermined range may be the state quantity lower than a first value. The first value may be a value obtained by subtracting an amount of increase in the state quantity as a result of execution of the regeneration control from an upper limit value of the state quantity. The controller may be configured to, when the state quantity is higher than the first value, change the start-up threshold to a value larger than the start-up threshold that is used when the state quantity is lower than the first value.

[0008] In the above aspect, the controller may be configured to, in any one of a case Where the state quantity is lower than the first value and a case where the regeneration control has completed, change the start-up threshold to a value smaller than the start-up threshold that is used when the state quantity is higher than the first value.

[0009] In the above aspect, the regeneration control may be executed such that an ignition timing of the gasoline engine when regeneration of the filter is required is more retarded than an ignition timing of the gasoline engine when regeneration of the filter is not required. The predetermined range may be the state quantity higher than a second value. The second value may be a value obtained by adding an amount of reduction in the state quantity as a result of execution of the regeneration control to a lower limit value of the state quantity. The controller may be configured to, when the state quantity is lower than the second value, change the start-up threshold to a value smaller than the start-up threshold that is used when the state quantity is higher than the second value.

[0010] In the above aspect, the controller may be configured to, in any one of a case where the state quantity is higher than the second value and a case where the regeneration control has completed, change the start-up threshold to a value larger than the start-up threshold that is used when the state quantity is lower than the second value.

[0011] Another aspect of the invention provides a controller for a hybrid vehicle.

The controller includes an ECU. The hybrid vehicle includes a gasoline engine, a filter, an electrical storage device and a converter. The gasoline engine is configured to start up when driving force of the vehicle exceeds a start-up threshold. The filter is configured to trap particulate matter flowing through an exhaust passage of the gasoline engine. The converter is configured to convert power of the gasoline engine to electric power for charging the electrical storage device, and is configured to convert electric power of the electrical storage device to driving force of the vehicle. The ECU is configured to: when regeneration of the filter is required, change the start-up threshold so that a state quantity of the electrical storage device changes in a direction opposite to a direction in which the state quantity varies as a result of execution of regeneration control; and execute the regeneration control when the state quantity changes into a predetermined range in which execution of the regeneration control is allowed. The regeneration control is executed when the filter is regenerated. The regeneration control is control so that a temperature of the filter increases to a regeneratable temperature. The state quantity indicates a state of charge of the electrical storage device.

[0012] Further another aspect of the invention provides a control method for a hybrid vehicle. The hybrid vehicle includes a gasoline engine, a filter, an electrical storage device, a converter, and an ECU. The gasoline engine is configured to start up when driving force of the vehicle exceeds a start-up threshold. The filter is configured to trap particulate matter flowing through an exhaust passage of the gasoline engine. The converter is configured to convert power of the gasoline engine to electric power for charging the electrical storage device, and is configured to convert electric power of the electrical storage device to driving force of the vehicle. The control method includes: when regeneration of the filter is required, changing, by the ECU, the start-up threshold so that a state quantity of the electrical storage device changes in a direction opposite to a direction in which the state quantity varies as a result of execution of regeneration control; and executing, by the ECU, the regeneration control when the state quantity changes into a predetermined range in which execution of the regeneration control is allowed. The regeneration control is executed when the filter is regenerated. The regeneration control is control so that a temperature of the filter increases to a regeneratable temperature. The state quantity indicates a state of charge of the electrical storage device.

[0013] According to these aspects, when the state quantity of the electrical storage device is changed by changing the start-up threshold, it is possible to avoid deterioration of the efficiency as compared to when the state quantity is changed by adjusting the amount of charge of the electrical storage device and the amount of discharge of the electrical storage device. Deterioration of the efficiency is due to an increase in electrical path at the time when the amount of charge increases or a decrease in engine load at the time when the amount of discharge increases. Therefore, by changing the start-up threshold, it is possible to efficiently change the state quantity of the electrical storage device into the predetermined range in which regeneration control is allowed. Thus, it is possible to provide the hybrid vehicle that is able to efficiently execute regeneration control over the filter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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 functional block diagram of an ECU;

FIG. 3 is a flowchart that shows the control structure of a program that is executed in the ECU according to a first embodiment;

FIG. 4 is a timing chart that shows a change in SOC, a change in start-up threshold, and the operation of the ECU according to the first embodiment;

FIG. 5 is a flowchart that shows the control structure of a program that is executed in the ECU according to a second embodiment;

FIG. 6 is a timing chart that shows a change in SOC, a change in start-up threshold, and the operation of the ECU according to the second embodiment;

FIG. 7 is a first view that shows another example of the layout of an exhaust passage;

FIG 8 is a second view that shows another example of the layout of the exhaust passage; and

FIG. 9 is a third view that shows another example of the layout of the exhaust passage. DETAILED DESCRIPTION OF EMBODIMENTS

[0015] Hereinafter, embodiments 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.

[0016] 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 torsional damper 18, a power control unit (PCU) 60, a battery 70, drive wheels 72, and an electronic control unit (ECU) 200.

[0017] The transmission 8 includes a drive 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.

[0018] The vehicle 1 travels by using driving force that is output from at least one of the engine 10 and 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.

[0019] - 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.

[0020] 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.

[0021] The second MG 30 has the function of a drive motor that provides driving force to the drive wheels 72 by using at least one of electric power stored in the battery 70 and 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.

[0022] The engine 10 is a gasoline engine, and is controlled on the basis of a control signal SI from the ECU 200. [0023] A crank position sensor 11 is provided at a location at which the crank position sensor 11 faces the crankshaft of the engine 10. The crank position sensor 11 detects the rotation speed Ne of the engine 10. The crank position sensor 11 transmits a signal indicating the detected rotation speed Ne of the engine 10 to the ECU 200.

[0024] The crank position sensor 11 may detect the rotation angle and angular velocity of the crankshaft of the engine 10, and the ECU 200 may calculate the rotation speed Ne of the engine 10 on the basis of the rotation angle and angular velocity received from the crank position sensor 11.

[0025] In the present embodiment, the engine 10 includes four cylinders 112, that is, the first cylinder to the fourth cylinder. An ignition plug (not shown) is provided at each of top portions inside the plurality of cylinders 112.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] An exhaust passage 80 is coupled to the engine 10. The layout of the exhaust passage 80 according to the present embodiment will be described later.

[0030] The torsional damper 18 is provided between the crankshaft of the engine 10 and an input shaft of the transmission 8. The torsional damper 18 absorbs torque fluctuations at the time of transmitting power between the crankshaft of the engine 10 and the input shaft of the transmission 8.

[0031] The power split device 40 is a power transmission device that mechanically couples three elements, that is, the drive shaft 16, the output shaft of the engine 10 and the rotary shaft of the first MG 20. The drive shaft 16 is coupled to the drive wheels 72. The power split device 40 sets any one of the three elements as a reaction element to enable transmission of power between the other two elements. The rotary shaft of the second MG 30 is coupled to the drive shaft 16. [0032] The power split device 40 is a planetary gear train including a sun gear 50, pinion gears 52, a carrier 54 and a ring gear 56. The pinion gears 52 are in mesh with each of the sun gear 50 and the ring gear 56. The carrier 54 supports the pinion gears 52 such that each pinion gear 52 is rotatable on its axis. The carrier 54 is coupled to the crankshaft of the engine 10. The sun gear 50 is coupled to the rotary shaft of the first MG 20. The ring gear 56 is coupled to the rotary shaft of the second MG 30 and the reduction gear 58 via the drive shaft 16.

[0033] The reduction gear 58 transmits power from the power split device 40 or the second MG 30 to the drive wheels 72. The reduction gear 58 transmits reaction received by the drive wheels 72 from a road surface to the power split device 40 or the second MG 30.

[0034] The PCU 60 converts direct-current power stored in the battery 70 to alternating-current power for driving the first MG 20 and the second MG 30. The PCU 60 includes a converter and an inverter (which are not shown) that are controlled on the basis of a control signal S2 from the ECU 200. The converter steps up the voltage of direct-current power received from the battery 70, and outputs the resultant direct-current power to the inverter. The inverter converts the direct-current power output from the converter to alternating-current power, and outputs the alternating- current power to the first MG 20 and/or the second MG 30. Thus, the first MG 20 and/or the second MG 30 are driven by using electric power stored in the battery 70. The inverter converts alternating-current power generated by the first MG 20 and/or the second MG 30 to direct-current power, and outputs the direct-current power to the converter. The converter steps down the voltage of the direct-current power output from the inverter, and outputs the resultant direct-current power to the battery 70. Thus, the battery 70 is charged with electric power generated by the first MG 20 and/or the second MG 30. The converter may be omitted.

[0035] 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. The voltage of the battery 70 is , for example, about 200 V. 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. The vehicle 1 may be equipped with a charging apparatus that allows the battery 70 to be charged with the use of an external power supply.

[0036] A current sensor 152, a voltage sensor 154 and a 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.

[0037] The ECU 200 estimates a state quantity on the basis of the current IB, voltage VB and battery temperature TB of the battery 70. The state quantity indicates the state of charge (hereinafter, referred to as SOC) 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.

[0038] A first resolver 12 is provided in the first MG 20. The first resolver 12 detects the rotation speed Nml of the first MG 20. The first resolver 12 transmits a signal indicating the detected rotation speed Nml to the ECU 200.

[0039] A second resolver 13 is provided in the second MG 30. The second resolver 13 detects the rotation speed Nm2 of the second MG 30. The second resolver 13 transmits a signal indicating the detected rotation speed Nm2 to the ECU 200.

[0040] A 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 Nm2 of the second MG 30 instead of the rotation speed Nw.

[0041] An accelerator pedal 160 is provided at a driver seat. A 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 of an occupant of the vehicle 1, which is exerted on the accelerator pedal 160.

[0042] The ECU 200 generates a control signal S 1 for controlling the engine 10, and outputs the generated control signal SI to the engine 10. The ECU 200 generates a control signal for controlling the PCU 60, and outputs the generated control signal S2 to the PCU 60. [0043] 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.

[0044] 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. When an auxiliary is operated, the ECU 200 adds a power, required to operate the auxiliary, to the calculated required vehicle power. The auxiliary is, for example, an air conditioner. In addition, when the battery 70 is charged, the ECU 200 adds a power, required to charge the battery, to the calculated required vehicle power. 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 vehicle power.

[0045] In the present embodiment, the ECU 200 may calculate a required vehicle power on the basis of the stroke AP and the vehicle speed V, and controls the power of the vehicle 1 on the basis of the calculated required vehicle power. Instead, for example, the ECU 200 may calculate a required driving force (required driving torque) on the basis of the stroke AP and the vehicle speed V, and may control the driving force (driving torque) of the vehicle 1 so that the calculated required driving force is generated in the vehicle 1.

[0046] In the present embodiment, a configuration, including the transmission 8 and the PCU 60, corresponds to a converter. The transmission 8 includes the first MG 20 and the second MG 30. The PCU 60 exchanges electric power with the first MG 20 and the second MG 30. The converter is able to convert the power of the engine 10 to electric power for charging the battery 70, and is able to convert the electric power of the battery 70 to power (driving force) for propelling the vehicle 1.

[0047] The ECU 200, for example, executes charge/discharge control over the battery 70 so that the SOC of the battery 70 falls within a predetermined control range. The ECU 200 may execute charge/discharge control over the battery 70 so that the SOC of the battery 70 keeps a predetermined target SOC.

[0048] Charge control over the battery 70 includes, for example, charge control that uses regenerated electric power that is generated through regenerative braking of the second MG 30 and charge control that uses electric power generated by the first MG 20 by using the power of the engine 10.

[0049] When the SOC of the battery 70 falls outside the predetermined control range (or exceeds the target SOC), the ECU 200 controls the PCU 60 so that the vehicle travels by using only the output of the second MG 30 (travels in an electric vehicle (EV) mode) as long as the required vehicle power does not exceed a start-up threshold Pr(l) of the engine 10.

[0050] When the vehicle 1 is traveling by using only the output of the second MG 30 as described above, the ECU 200 starts up the engine 10 after the required vehicle power exceeds the start-up threshold Pr(l) of the engine 10 (that is, after it is determined that the required vehicle power is not satisfied with only the output of the second MG 30), the ECU 200 starts up the engine 10 and controls the PCU 60 and the engine 10 so that the required vehicle power is satisfied with the output of the second MG 30 and the output of the engine 10.

[0051] In the present embodiment, the start-up threshold Pr(l) is lower than or equal to an upper limit value of the output of the second MG 30 and is lower than or equal to an output limit value (Wout) of the output of the battery 70.

[0052] A catalyst 82 is arranged in the exhaust passage 80. The catalyst 82 oxidizes unburned components contained in exhaust gas that is emitted from the engine 10, or reduces oxidized components. Specifically, the catalyst 82 has occluded oxygen, and oxidizes unburned components, such as HC and CO, by using occluded oxygen when the unburned components are contained in exhaust gas. When oxidized components, such as NOx, are contained in exhaust gas, the catalyst 82 is able to reduce the oxidized components and occlude released oxygen. Therefore, the percentage of nitrogen dioxide (N0₂) contained in exhaust gas increases because of the catalyst 82.

[0053] A 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.

[0054] An air-fuel ratio sensor 86 is provided at a location upstream of the catalyst 82 in the exhaust passage 80. An oxygen sensor 88 is provided at a location downstream of the catalyst 82 and upstream of the filter 84 in the exhaust passage 80.

[0055] Each of the air- fuel ratio sensor 86 and the oxygen sensor 88 is used to detect the air-fuel ratio of air-fuel mixture, that is, a mixture of fuel and air, which are supplied to each of the plurality of cylinders 112. Each of the air- fuel ratio sensor 86 and 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.

[0056] An 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. A downstream-side pressure sensor 92 is provided at a location downstream of the filter 84 in the exhaust passage 80.

[0057] 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.

[0058] When the ECU 200 determines that regeneration of the filter 84 is required, the ECU 200 executes regeneration control over the filter 84. Regeneration control over the filter 84 increases the temperature of the filter 84 to a regeneratable temperature (activation temperature) or higher. When the temperature of the filter 84 increases to the regeneratable temperature as a result of regeneration control, PM accumulated in the filter 84 oxidizes by burning reaction with N0₂. As a result, the PM accumulated in the filter 84 is removed from the filter 84.

[0059] When PM accumulates in the filter 84 to such an extent that over temperature (OT) due to burning of PM does not occur, the ECU 200 determines that regeneration of the filter 84 is required. In the present embodiment, the ECU 200 determines, by using the upstream-side pressure sensor 90 and the downstream-side pressure sensor 92, whether regeneration of the filter 84 is required.

[0060] Specifically, the ECU 200 determines that regeneration of the filter 84 is required 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 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 of the engine 10.

[0061] 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. The ECU 200 may estimate the temperature of the filter 84 by utilizing various sensors, such as the oxygen sensor, the air- fuel ratio sensor, an air flow meter, a throttle opening degree sensor and a coolant temperature sensor. Alternatively, the ECU 200 may estimate the amount of PM accumulated in the filter 84 on the basis of an operation history of the engine 10, an operating time, or the amount of decrease in output, or the like.

[0062] Regeneration control over the filter 84 includes, for example, output raising control and ignition timing retardation control.

[0063] Output raising control increases the output of the gasoline engine when regeneration of the filter is required as compared to the output of the gasoline engine when regeneration of the filter is not required. That is, output raising control increases exhaust gas temperature by raising the output of the engine 10. Specifically, output raising control increases the exhaust gas temperature of the engine 10 by raising the output of the engine 10 over an ordinary value, with the result that the temperature of the filter 84 is increased to the regeneratable temperature. The output of the engine 10 is raised by adjusting at least one of the throttle opening degree, the fuel injection amount and the ignition timing.

[0064] For example, when the ECU 200 executes regeneration control, the ECU 200 determines the output power of the engine 10 on the basis of a required driving power and then causes the engine 10 to output the output power obtained by increasing the determined output power (ordinary value) by a predetermined raising amount.

[0065] Part or all of redundant output as a result of raising the output of the engine 10 is converted to electric power generated by the first MG 20, and is supplied to the battery 70 (the battery 70 is charged).

[0066] The output of the engine 10 may be raised by stepwisely changing from the ordinary value to a value increased by the predetermined raising amount when regeneration control is executed. Alternatively, the output of the engine 10 may be raised by linearly or non-linearly increasing from the ordinary value to a value increased by the predetermined raising amount with a lapse of time.

[0067] The predetermined raising amount is, for example, set in consideration of the response of an increase in the temperature of the filter 84, or the like. The raising amount is not limited to a predetermined amount. The raising amount may be set on the basis of the degree of PM clogged (the amount of PM accumulated) in the filter 84 and an acceptable electric power based on the SOC, temperature, and the like, of the battery 70.

[0068] Because the exhaust gas temperature is increased by raising the output of the engine 10 over the ordinary value as compared to that in the case where the output of the engine 10 is controlled in accordance with the ordinary value, it is possible to early increase the temperature of the filter 84 to the regeneratable temperature. Therefore, it is possible to early remove PM accumulated in the filter 84. [0069] Ignition timing retardation control retards the ignition timing of the gasoline engine when regeneration of the filter is required as compared to the ignition timing of the gasoline engine when regeneration of the filter is not required. That is, ignition timing retardation control increases the exhaust gas temperature by retarding the ignition timing. Specifically, ignition timing retardation control increases the exhaust gas temperature of the engine 10 by retarding the ignition timing of the engine 10 with respect to an ordinary value by a predetermined retardation amount, with the result that the temperature of the filter 84 is increased to the regeneratable temperature.

[0070] For example, when the output power of the engine 10 is determined, the ECU 200 obtains a base ignition timing on the basis of the determined output power. The ECU 200 controls an actual ignition timing by using a result obtained by correcting the obtained base ignition timing with a correction amount associated with an intake air temperature, an EGR amount, and the like. Therefore, the ECU 200 corrects the base ignition timing with a correction amount corresponding to a predetermined amount in addition to the correction amount, such as the intake air temperature and the EGR amount, when regeneration control is executed.

[0071] The amount of decrease in the output of the engine 10, which occurs as a result of retarding the ignition timing with respect to the ordinary value by the predetermined retardation amount, is, for example, compensated by an increase in the output of the second MG 30, or the like. Therefore, the amount of discharge from the battery 70 increases.

[0072] The ignition timing may be retarded by stepwisely changing from the ordinary value to a value retarded by the predetermined retardation amount when regeneration control is executed or may be retarded by linearly or non-linearly changing from the ordinary value to the value retarded by the predetermined retardation amount with a lapse of time when regeneration control is executed.

[0073] The predetermined retardation amount is, for example, set in consideration of the response of an increase in the temperature of the filter 84, or the like. The retardation amount is not limited to the predetermined amount. The retardation amount may be set on the basis of the degree of PM clogged in the filter 84, the state of the battery 70, or the like.

[0074] Because the exhaust gas temperature is increased by retarding the ignition timing of the engine 10 with respect to the ordinary value as compared to that in the case where the ignition timing is set to the ordinary value, it is possible to early increase the temperature of the filter 84 to the regeneratable temperature. Therefore, it is possible to early remove PM accumulated in the filter 84.

[0075] In the thus configured vehicle, when the regeneration control is executed, the battery 70 is charged or the amount of discharge of the battery 70 increases as described above, so the SOC of the battery 70 increases or decreases. Therefore, for example, when the SOC of the battery 70 is close to a limit value (an upper limit value or a lower limit value), the ECU 200 changes the SOC of the battery 70 into a predetermined range by changing the SOC of the battery 70 in a direction opposite to a direction in which the SOC varies as a result of execution of regeneration control in order to execute regeneration control. Within the predetermined range, execution of regeneration control is allowed. After that, (that is, after the allowance of a change in the SOC of the battery 70 is ensured), the ECU 200 executes regeneration control.

[0076] Incidentally, the engine 10 that is a gasoline engine provides a less amount of

PM generated as compared to a diesel engine having a comparable output, so the frequency of executing regeneration control and the required response are also lower than those of the diesel engine. Therefore, when the SOC of the battery 70 is changed in order to execute regeneration control, the gasoline engine desirably ensures the allowance of change in the SOC of the battery 70 by placing importance on efficiency over response as compared to the diesel engine.

[0077] Therefore, in the present embodiment, when regeneration of the filter 84 is required, the ECU 200 changes the start-up threshold of the engine 10 so that the SOC of the battery 70 changes in a direction opposite to a direction in which the SOC varies as a result of execution of regeneration control, and then executes regeneration control after the SOC has changed into the predetermined range in which execution of regeneration control is allowed.

[0078] In the present embodiment, the case where output raising control is executed as regeneration control is described as an example. In this case, the direction in which the SOC varies as a result of execution of regeneration control is a direction in which the SOC increases.

[0079] Therefore, in the present embodiment, the ECU 200 raises the start-up threshold of the engine 10 when regeneration of the filter 84 is required and the SOC falls outside the predetermined range.

[0080] The predetermined range is an SOC lower than a first value (hereinafter referred to as threshold SOC a) obtained by subtracting the amount of increase in the SOC (the amount of charge), which occurs as a result of execution of regeneration control, from the upper limit value of the SOC of the battery 70. The predetermined range may include the threshold SOC_a. In the present embodiment, the predetermined range is described as a range lower than or equal to the threshold SOC_a.

[0081] That is, when regeneration of the filter 84 is required and the SOC is higher than the threshold SOC a, the ECU 200 changes the start-up threshold to a value larger than the start-up threshold that is used when the SOC is lower than the threshold SOC a.

[0082] In the present embodiment, the ECU 200, for example, raises the start-up threshold by changing the start-up threshold to a value Pr(2) obtained by adding a predetermined value to the original start-up threshold Pr(l).

[0083] In the present embodiment, description will be made on the assumption that, for example, after the start-up threshold of the engine 10 is raised, when the SOC is lower than or equal to the threshold SOC_a and regeneration control has completed, the ECU 200 lowers the start-up threshold by changing the start-up threshold from Pr(2) to Pr(l) that is the original start-up threshold. For example, after the start-up threshold Pr(2) of the engine 10 is changed, in any one of the case where the SOC becomes lower than or equal to the threshold SOC_a and the case where regeneration control has completed, the start-up threshold may be changed to a value lower than the start-up threshold that is used when the SOC is higher than the threshold SOC a.

[0084] FIG. 2 shows a functional block diagram of the ECU 200 mounted on the vehicle 1 according to the present embodiment. The ECU 200 includes a regeneration necessity determination unit 202, an SOC determination unit 204, a start-up threshold setting unit 206, a regeneration control unit 208, a completion determination unit 210 and a return control unit 212.

[0085] The regeneration necessity determination unit 202 determines whether regeneration of the filter 84 is required. A method of determining whether regeneration of the filter 84 is required is as described above, so the detailed description will not be repeated. The regeneration necessity determination unit 202 may, for example, set a regeneration control request flag to an on state when the regeneration necessity determination unit 202 determines that regeneration of the filter 84 is required.

[0086] When the regeneration necessity determination unit 202 determines that regeneration of the filter 84 is required, the SOC determination unit 204 determines whether the SOC of the battery 70 is lower than or equal to the threshold SOC a. The threshold SOC a is as described above, so the detailed description will not be repeated.

[0087] For example, when the regeneration control request flag is in the on state, the

SOC determination unit 204 determines whether the SOC of the battery 70 is lower than or equal to the threshold SOC_a. When the SOC of the battery 70 is lower than or equal to the threshold SOC_a, the SOC determination unit 204 may set an SOC determination flag to an on state.

[0088] When the SOC determination unit 204 determines that the SOC of the battery 70 is higher than the threshold SOC_a, the start-up threshold setting unit 206 changes the start-up threshold of the engine 10 so that the SOC of the battery 70 changes in a direction opposite to a direction in which the SOC varies as a result of execution of regeneration control.

[0089] In the present embodiment, the start-up threshold setting unit 206 raises the start-up threshold of the engine 10. The raising amount may be a predetermined amount. The raising amount may be changed on the basis of the state of the vehicle 1 (for example, a vehicle speed, a road surface gradient, or the like) or the state of the engine 10 (for example, the state of progression of warm-up (coolant temperature), or the like).

[0090] The start-up threshold setting unit 206 may raise the start-up threshold so as to stepwisely increase the start-up threshold of the engine 10 from a value before raising to a value after raising. The start-up threshold setting unit 206 may raise the start-up threshold so as to linearly or non-linearly increase from a value before raising to a value after raising with a lapse of time.

[0091] When the start-up threshold of the engine 10 is raised, the start-up frequency of the engine 10 decreases. As a result, a region (EV traveling region) in which the vehicle travels by using the second MG 30 in a state where the engine 10 is stopped (EV mode) expands. That is, the frequency or duration of EV mode increases, with the result that a decrease in the SOC of the battery 70 is facilitated.

[0092] The start-up threshold setting unit 206, for example, may change the start-up threshold when the SOC determination flag is in an off state.

[0093] When the SOC determination unit 204 determines that the SOC of the battery 70 is lower than or equal to the threshold SOC a, the regeneration control unit 208 executes regeneration control over the filter 84. In the present embodiment, the regeneration control unit 208 executes output raising control over the engine 10 as regeneration control over the filter 84. Output raising control is as described above, so the detailed description will not be repeated.

[0094] In the present embodiment, during execution of regeneration control as well, the engine 10 intermittently operates or continuously operates on the basis of the state of the vehicle 1 (the state of the battery 70, an accelerator operation amount, the speed of the vehicle, and the like).

[0095] Description will be made on the assumption that the regeneration control unit 208, for example, executes output raising control during operation of the engine 10 until the completion determination unit 210 (described later) determines that regeneration control over the filter 84 has completed. The regeneration control unit 208 may, for example, continue the operation of the engine 10 (suppress or prohibit a stop of the engine 10) until the completion determination unit 210 determines that regeneration control over the filter 84 has completed.

[0096] Alternatively, when the temperature of the filter 84 significantly exceeds a predetermined temperature (for example, the temperature of the filter 84 is close to an upper limit temperature of the filter 84) or when it is estimated that the temperature of the filter 84 significantly exceeds the predetermined temperature, the regeneration control unit 208 may, for example, stop the operation of the engine 10 or the output raising control until the temperature of the filter 84 becomes the regeneratable temperature or until it is estimated that the temperature of the filter 84 becomes the regeneratable temperature even during execution of regeneration control.

[0097] The regeneration control unit 208 may execute regeneration control, for example, when the SOC determination flag is in the on state. The regeneration control unit 208 may, for example, execute regeneration control and set a regeneration control execution flag to an on state.

[0098] After regeneration control is executed by the regeneration control unit 208, the completion determination unit 210 determines whether regeneration control over the filter 84 has completed. The completion determination unit 210 uses the upstream-side pressure sensor 90 and the downstream-side pressure sensor 92 to determine whether regeneration control over the filter 84 has completed.

[0099] Specifically, when the difference between the upstream-side pressure that is detected by the upstream-side pressure sensor 90 and the downstream-side pressure that is detected by the downstream-side pressure sensor 92 is smaller than a threshold, the completion determination unit 210 determines that regeneration control over the filter 84 has completed.

[0100] The threshold that is used to determine whether regeneration control has completed may be a predetermined value that is adapted by an experiment or a design or may be a value that changes on the basis of the operating state of the engine 10.

[0101] The threshold that is used to determine whether regeneration control 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.

[0102] For example, when the regeneration control execution flag is in the on state, the completion determination unit 210 may determine whether regeneration of the filter 84 has completed, and a completion determination flag may be set to an on state when it is determined that regeneration control over the filter 84 has completed.

[0103] When the completion determination unit 210 determines that regeneration of the filter 84 has completed, the return control unit 212 executes return control. In the present embodiment, the return control unit 212 ends output raising control and lowers the start-up threshold of the engine 10 to the original value as return control.

[0104] For example, when the SOC determination unit 204 determines that the SOC of the battery 70 is lower than or equal to the threshold SOC_a, the return control unit 212 may lower the start-up threshold of the engine 10 to the original value before execution of regeneration control or together with execution of regeneration control.

[0105] With this configuration, it is possible to set the start-up frequency of the engine 10 during execution of regeneration control such that the start-up frequency of the engine 10 is equivalent to that during non-execution of regeneration control. Therefore, it is possible to early complete regeneration of the filter 84 by suppressing a decrease in the start-up frequency of the engine 10.

[0106] The return control unit 212 may execute return control, for example, when the completion determination flag is in the on state.

[0107] A control process that is executed by the ECU 200 mounted on the vehicle according to the present embodiment will be described with reference to FIG. 3.

[0108] 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. When it is determined that regeneration of the filter 84 is not required (NO in S 100), the process ends.

[0109] In S 102, the ECU 200 determines whether the SOC of the battery 70 is lower than or equal to the threshold SOC a. When it is determined that the SOC of the battery 70 is lower than or equal to the threshold SOC_a (YES in SI 02), the process proceeds to SI 04. When it is determined that the SOC of the battery 70 is larger than the threshold SOC_a (NO in SI 02), the process proceeds to SI 06.

[0110] In S104, the ECU 200 executes output raising control as regeneration control. In SI 06, the ECU 200 raises the start-up threshold of the engine 10. In SI 08, 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 08), the process proceeds to SI 10. When it is determined that regeneration of the filter 84 has not completed (NO in SI 08), the process returns to SI 04.

[0111] In SI 10, the ECU 200 ends output raising control, and lowers the start-up threshold of the engine 10 to the original value. [0112] 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. 4.

[0113] For example, it is assumed that the SOC of the battery 70 is SOC(0) (> SOC a) and the regeneration control request flag is in the off state. It is also assumed that the start-up threshold of the engine 10 is Pr(l) and the regeneration control execution flag is in the off state.

[0114] When it is determined at time T(0) that regeneration of the filter 84 is required on the basis of the fact the difference between the upstream-side pressure that is detected by the upstream-side pressure sensor 90 and the downstream-side pressure that is detected by the downstream- side pressure sensor 92 is larger than the threshold (YES in SI 00), the regeneration control request flag is set to the on state.

[0115] Because the SOC of the battery 70 is higher than the threshold SOC_a (NO in SI 02), the start-up threshold of the engine 10 is raised from Pr(l) to Pr(2) higher by the predetermined value (SI 06). When the start-up threshold of the engine 10 is raised, the start-up frequency of the engine 10 decreases, so the EV traveling region of the vehicle 1 expands. As a result, the SOC of the battery 70 decreases with a lapse of time.

[0116] In FIG. 4, for the sake of convenience of description, the SOC of the battery 70 is shown so as to linearly decrease or increase with a lapse of time. However, the SOC of the battery 70 is not limited to such a change. The SOC of the battery 70 may decrease or increase non-linearly or decrease or increase as a whole while repeating a small increase and decrease depending on the traveling condition of the vehicle 1.

[0117] When the SOC of the battery 70 becomes lower than or equal to the threshold SOC_a at time T(l) (YES in S102), output raising control is executed as regeneration control. Together with execution of regeneration control, the regeneration control execution flag is set to the on state. A redundant amount of the output of the engine 10 as a result of execution of output raising control is converted to electric power that is generated by the first MG 20, and the electric power is supplied to the battery 70 (the battery 70 is charged). Therefore, the SOC of the battery 70 increases.

[0118] The exhaust gas temperature of the engine 10 increases as a result of execution of output raising control, so the temperature of the filter 84 also increases. When the temperature of the filter 84 increases to the regeneratable temperature range, PM accumulated in the filter 84 is oxidized, and the PM is removed from the filter 84.

[0119] When it is determined at time T(2) that regeneration of the filter 84 has completed on the basis of the fact that the difference between the upstream-side pressure that is detected by the upstream-side pressure sensor 90 and the downstream-side pressure that is detected by the downstream-side pressure sensor 92 becomes smaller than the threshold (YES in SI 08), output raising control ends, the regeneration control request flag and the regeneration control execution flag both are set to the off state, and the start-up threshold of the engine 10 is lowered from Pr(2) to Pr(l) that is the original value (S 110).

[0120] As described above, with the vehicle according to the present embodiment, the start-up threshold of the engine 10 is raised so that the SOC changes in a direction opposite to a direction in which the SOC varies as a result of execution of regeneration control. As a result of the fact that the start-up threshold is raised, the SOC is reduced and is changed to a value lower than or equal to the threshold SOC_a, with the result that it is possible to suppress a situation that the SOC reaches the upper limit value before completion of regeneration control in the case where regeneration control is executed. As a method of changing the SOC before execution of regeneration control, it is conceivable to adjust the amount of charge of the battery 70 and the amount of discharge of the battery 70. However, an increase in the amount of charge leads to an increase in loss due to an increase in electrical path, and an increase in the amount of discharge leads to deterioration of fuel economy due to a decrease in the load of the engine, so the efficiency deteriorates. Therefore, in comparison with this method, changing the SOC by changing the start-up threshold allows to avoid the above-described deterioration of the efficiency, so it is possible to efficiently change the SOC into the predetermined range in which execution of regeneration control is allowed. Thus, it is possible to provide the hybrid vehicle that efficiently executes regeneration control over the filter.

[0121] Because the amount of PM generated from the diesel engine is larger than that of the gasoline engine, as a method of adjusting the SOC before execution of regeneration control over a DPF, it is desirable to adjust the SOC due to an increase in the amount of charge and an increase in the amount of discharge by placing importance on response in order to quickly execute regeneration control. In contrast, by applying the invention to the gasoline engine from which the amount of PM generated is smaller than a diesel engine, it is possible to efficiently execute regeneration control over the filter as compared to the case of a diesel engine.

[0122] When the SOC is higher than the threshold SOC_a, it is possible to adjust the SOC before execution of regeneration control at appropriate timing by raising the start-up threshold.

[0123] When output raising control is executed as regeneration control, the SOC tends to increase. Therefore, by raising the start-up threshold of the engine, it is possible to adjust the SOC so that the SOC falls within the predetermined range (lower than or equal to the threshold SOC_a) in which execution of regeneration control is allowed. By adjusting the SOC within the predetermined range, it is possible to provide an allowance for the SOC to execute regeneration control.

[0124] When the start-up threshold has been raised, the start-up threshold is lowered when the SOC changes into the predetermined range thereafter or when regeneration control has completed thereafter. Thus, unnecessary continuation of a state where the start-up threshold is raised is suppressed.

[0125] In the present embodiment, output raising control is executed as regeneration control. However, the SOC of the battery 70 just needs to increase as a result of execution of regeneration control, and, particularly, regeneration control is not limited to output raising control.

[0126] In the present embodiment, when regeneration of the filter 84 is required, the start-up threshold is raised when the SOC is higher than the threshold SOC a. However, when the ECU 200 controls the vehicle 1 in accordance with any one of a plurality of drive modes including a first drive mode and a second drive mode in which the start-up threshold is higher than that in the first drive mode, the ECU 200 may shift the drive mode from the first drive mode to the second drive mode when the SOC is higher than the threshold SOC a in the case where regeneration of the filter 84 is required in the first drive mode. With this configuration as well, it is possible to raise the start-up threshold of the engine 10.

[0127] Hereinafter, a vehicle according to a second embodiment will be described. The vehicle according to the present embodiment differs from the configuration of the vehicle 1 according to the first embodiment in that ignition timing retardation control is executed as regeneration control and part of the operation of the ECU 200 is changed. The other components are the same as the components of the vehicle 1 according to the first embodiment shown in FIG. 1. Like reference numerals denote the same components.. The functions of the corresponding components are also the same. Thus, the detailed description of the corresponding components will not be repeated.

[0128] In the present embodiment, the case where ignition timing retardation control is executed as regeneration control will be described as an example. The direction in which the SOC varies as a result of execution of regeneration control in this case is a direction in which the SOC decreases.

[0129] Therefore, in the present embodiment, the ECU 200 lowers the start-up threshold of the engine 10 when regeneration of the filter 84 is required and the SOC falls outside the predetermined range. [0130] In the present embodiment, the predetermined range is an SOC higher than a second value (hereinafter, referred to as threshold SOC b) obtained by adding the amount of reduction in SOC (the amount of discharge), which occurs as a result of execution of regeneration control, to the lower limit value of the SOC of the battery 70. The predetermined range may include the threshold SOC b. In the present embodiment, the predetermined range is described as a range higher than or equal to the threshold SOC_b.

[0131] That is, when regeneration of the filter 84 is required and the SOC is lower than the threshold SOC_b, the ECU 200 changes the start-up threshold to a value smaller than the start-up threshold that is used when the SOC is higher than the threshold SOC_b.

[0132] In the present embodiment, it is assumed that the ECU 200, for example, lowers the start-up threshold by changing the start-up threshold to a value Pr(3) obtained by subtracting a predetermined value from the start-up threshold Pr(l).

[0133] In the present embodiment, description will be made on the assumption that, after the start-up threshold of the engine 10 is lowered, when the SOC is higher than or equal to the threshold SOC_b and regeneration control has completed, the ECU 200, for example, raises the start-up threshold by changing the start-up threshold from Pr(3) to Pr(l) that is the original start-up threshold. After the start-up threshold of the engine 10 is changed to Pr(3), in at least one of the case where the SOC becomes higher than or equal to the threshold SOC_b and the case where regeneration control has completed, the ECU 200 may change the start-up threshold to a value larger than the start-up threshold that is used when the SOC is lower than the threshold SOC b.

[0134] The functional block diagram of the ECU 200 mounted on the vehicle 1 according to the present embodiment is the same as the functional block diagram shown in FIG. 2 described in the first embodiment, and part of the components described below have different functions, and the other components have the same functions. The detailed description of the components having the same functions will not be repeated.

[0135] In the present embodiment, when the regeneration necessity determination unit 202 determines that regeneration of the filter 84 is required, the SOC determination unit 204 determines whether the SOC of the battery 70 is higher than or equal to the threshold SOC_b. The threshold SOC_b is as described above, so the detailed description will not be repeated.

[0136] Fop example, when the regeneration control request flag is in the on state, the SOC determination unit 204 determines whether the SOC of the battery 70 is higher than or equal to the threshold SOC b. When the SOC of the battery 70 is higher than or equal to the threshold SOC b, the SOC determination unit 204 may set an SOC determination flag to an on state.

[0137] When the SOC determination unit 204 determines that the SOC of the battery 70 is lower than the threshold SOC_b, the start-up threshold setting unit 206 changes the start-up threshold of the engine 10 so that the SOC of the battery 70 changes in a direction opposite to a direction in which the SOC varies as a result of execution of regeneration control.

[0138] In the present embodiment, the start-up threshold setting unit 206 lowers the start-up threshold of the engine 10. The lowering amount may be a predetermined amount. The lowering amount may be changed on the basis of the state of the vehicle 1 (for example, a vehicle speed, a road surface gradient, or the like) or the state of the engine 10 (for example, the state of progression of warm-up (coolant temperature), or the like).

[0139] The start-up threshold setting unit 206 may lower the start-up threshold so as to stepwisely reduce the start-up threshold of the engine 10 from a value before lowering to a value after lowering. The start-up threshold setting unit 206 may lower the start-up threshold so as to linearly or non-linearly decrease from a value before lowering to a value after lowering with a lapse of time.

[0140] When the start-up threshold of the engine 10 is lowered, the start-up frequency of the engine 10 increases, so the EV traveling region of the vehicle 1 shrinks. That is, the start-up frequency or operation duration of the engine 10 increases, with the result that an increase in the SOC of the battery 70 is facilitated.

[0141] When the SOC determination unit 204 determines that the SOC of the battery 70 is higher than or equal to the threshold SOC_b, the regeneration control unit 208 executes regeneration control over the filter 84. In the present embodiment, the regeneration control unit 208 executes ignition timing retardation control over the engine 10 as regeneration control over the filter 84. Ignition timing retardation control is as described above, so the detailed description will not be repeated.

[0142] When the completion determination unit 210 determines that regeneration of the filter 84 has completed, the return control unit 212 executes return control. In the present embodiment, the return control unit 212 ends ignition timing retardation control and raises the start-up threshold of the engine 10 to the original value as return control.

[0143] For example, when the SOC determination unit 204 determines that the SOC of the battery 70 is higher than or equal to the threshold SOC_b, the return control unit 212 may raise the start-up threshold of the engine 10 to the original value. The start-up threshold of the engine 10 may be raised before execution of regeneration control or together with execution of regeneration control. [0144] The control structure of a program that is executed in the ECU 200 mounted on the vehicle according to the present embodiment will be described with reference to FIG. 5.

[0145] In S200, 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 S200), the process proceeds to S202. When it is determined that regeneration of the filter 84 is not required (NO in S200), the process ends.

[0146] In S202, the ECU 200 determines whether the SOC of the battery 70 is higher than or equal to the threshold SOC_b. When it is determined that the SOC of the battery 70 is higher than or equal to the threshold SOC_b (YES in S202), the process proceeds to S204. When it is determined that the SOC of the battery 70 is lower than the threshold SOC b (NO in S202), the process proceeds to S206.

[0147] In S204, the ECU 200 executes ignition timing retardation control as regeneration control. In S206, the ECU 200 lowers the start-up threshold of the engine 10. In S208, 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 S208), the process proceeds to S210. When it is determined that regeneration of the filter 84 has not completed (NO in S208), the process proceeds to S204.

[0148] In S210, the ECU 200 ends ignition timing retardation control, and raises the start-up threshold of the engine 10 to the original value.

[0149] 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.

[0150] For example, it is assumed that the SOC of the battery 70 is SOC(l) (< SOC_b) and the regeneration control request flag is in the off state. It is also assumed that the start-up threshold of the engine 10 is Pr(l) and the regeneration control execution flag is in the off state.

[0151] When it is determined at time T'(0) that regeneration of the filter 84 is required on the basis of the fact the difference between the upstream-side pressure that is detected by the upstream-side pressure sensor 90 and the downstream-side pressure that is detected by the downstream-side pressure sensor 92 is larger than the threshold (YES in S200), the regeneration control request flag is in the on state.

[0152] Because the SOC of the battery 70 is lower than the threshold SOC b (NO in S202), the start-up threshold of the engine 10 is lowered from Pr(l) to Pr(3) lower by the predetermined value (S206). When the start-up threshold of the engine 10 is lowered, the start-up frequency of the engine 10 increases, so the EV traveling region of the vehicle 1 shrinks. As a result, the SOC of the battery 70 increases with a lapse of time.

[0153] In FIG. 6, for the sake of convenience of description, the SOC of the battery 70 is shown so as to linearly increase or decrease with a lapse of time. However, the SOC of the battery 70 is not limited to such a change. The SOC of the battery 70 may decrease or increase non-linearly or decrease or increase as a whole while repeating a small increase and decrease depending on the traveling condition of the vehicle 1.

[0154] When the SOC of the battery 70 becomes higher than or equal to the threshold SOC b at time T'(l) (YES in S202), ignition timing retardation control is executed as regeneration control. Together with execution of regeneration control, the regeneration control execution flag is set to the on state. The amount of decrease in the output of the engine 10 as a result of execution of ignition timing retardation control is compensated by an increase in the output of the second MG 30, so the amount of discharge of the battery 70 increases. Therefore, the SOC of the battery 70 decreases.

[0155] The exhaust gas temperature of the engine 10 increases as a result of execution of ignition timing retardation control, so the temperature of the filter 84 also increases. When the temperature of the filter 84 increases to the regeneratable temperature range, PM accumulated in the filter 84 is oxidized, and the PM is removed from the filter 84.

[0156] When it is determined at time T'(2) that regeneration of the filter 84 has completed on the basis of the fact that the difference between the upstream-side pressure that is detected by the upstream-side pressure sensor 90 and the downstream-side pressure that is detected by the downstream-side pressure sensor 92 becomes smaller than the threshold (YES in S208), ignition timing retardation control ends, the regeneration control request flag and the regeneration control execution flag both are set to the off state, and the start-up threshold of the engine 10 is raised from Pr( 3 ) to Pr( 1 ) that is the original value (S210).

[0157] As described above, with the vehicle according to the present embodiment, the start-up threshold of the engine 10 is lowered so that the SOC changes in a direction opposite to a direction in which the SOC varies as a result of execution of regeneration control. As a result of the fact that the start-up threshold is lowered, the SOC is increased and is changed to a value higher than or equal to the threshold SOC_b, with the result that it is possible to suppress a situation that the SOC reaches the lower limit value before completion of regeneration control in the case where regeneration control is executed. In comparison with a method of changing the SOC by adjusting the amount of charge of the battery 70 and the amount of discharge of the battery 70, which is used in the case of a diesel engine by placing importance on response, it is possible to efficiently change the SOC when the SOC is changed by changing the start-up threshold. Thus, it is possible to provide the hybrid vehicle that efficiently executes regeneration control over the filter.

[0158] When the SOC is lower than the threshold SOC b, it is possible to adjust the SOC before execution of regeneration control at appropriate timing by lowering the start-up threshold.

[0159] When ignition timing retardation control is executed as regeneration control, the SOC tends to decrease. Therefore, by lowering the start-up threshold of the engine, it is possible to adjust the SOC so that the SOC falls within the predetermined range (higher than or equal to the threshold SOC b) in which execution of regeneration control is allowed. By adjusting the SOC within the predetermined range, it is possible to provide an allowance for the SOC to execute regeneration control.

[0160] When the start-up threshold has been lowered, the start-up threshold is raised when the SOC changes into the predetermined range thereafter or when regeneration control has completed thereafter. Thus, unnecessary continuation of a state where the start-up threshold is lowered is suppressed.

[0161] In the present embodiment, ignition timing retardation control is executed as regeneration control. However, the SOC of the battery 70 just needs to decrease as a result of execution of regeneration control. Particularly, regeneration control is not limited to ignition timing retardation control.

[0162] In the present embodiment, when regeneration of the filter 84 is required, the start-up threshold is lowered when the SOC is lower than the threshold SOC_b. For example, when regeneration of the filter 84 is required in a CD mode, the mode may be changed to a CS mode when the SOC is lower than the threshold SOC_b. With this configuration as well, it is possible to lower the start-up threshold of the engine 10.

[0163] A combination of the configuration of the first embodiment (the configuration that executes output raising control as regeneration control) and the configuration of the second embodiment (the configuration that executes ignition timing retardation control as regeneration control) may be employed.

[0164] In the first and second embodiments, as described with reference to FIG. 1, the power of the gasoline engine is converted by the first MG 20 to electric power for charging the battery 70, and the electric power of the battery 70 is converted by the second MG 30 to power for propelling the vehicle 1. For example, both conversions may be carried out by a single motor generator, or both conversions may be carried out by three or more motor generators.

[0165] In the first and second embodiments, as illustrated in FIG. 1, the layout of the exhaust passage in which the catalyst 82 and the filter 84 are provided one by one is described as an example. Instead, the layout of an exhaust passage in which at least one of the catalyst 82 and the filter 84 is provided in two or more numbers may be employed.

[0166] For example, the layout of the exhaust passage may be the layout shown in FIG. 7. That is, as shown in FIG. 7, when the engine 10 is a V-engine having cylinders in each of a first bank 10a and a second bank 10b, a first catalyst 82a and a first filter 84a may be provided in a first exhaust passage 80a coupled to the cylinders formed in the first bank 10a, and a second catalyst 82b and a second filter 84b may be provided in a second exhaust passage 80b coupled to the cylinders formed in the second bank 10b.

[0167] In this case, as shown in FIG. 7, a first air- fuel ratio sensor 86a is provided at a location upstream of the first catalyst 82a in the first exhaust passage 80a, and a first oxygen sensor 88a is provided at a location just downstream of the first catalyst 82a. A first upstream-side pressure sensor 90a is provided at a location upstream of the first filter 84a in the first exhaust passage 80a, and a first downstream-side pressure sensor 92a is provided at a location just downstream of the first filter 84a.

[0168] In addition, a second air-fuel ratio sensor 86b is provided at a location upstream of the second catalyst 82b in the second exhaust passage 80b, and a second oxygen sensor 88b is provided at a location just downstream of the second catalyst 82b. A second upstream-side pressure sensor 90b is provided at a location upstream of the second filter 84b in the second exhaust passage 80b, and a second downstream-side pressure sensor 92b is provided at a location just downstream of the second filter 84b.

[0169] In the thus configured vehicle, the ECU 200 determines whether regeneration of the first filter 84a and/or the second filter 84b is required on the basis of at least one of a first differential pressure between a first upstream-side pressure that is detected by the first upstream-side pressure sensor 90a and a first downstream-side pressure that is detected by the first downstream-side pressure sensor 92a and a second differential pressure between a second upstream-side pressure that is detected by the second upstream-side pressure sensor 90b and a second downstream- side pressure that is detected by the second downstream-side pressure sensor 92b.

[0170] The ECU 200, for example, may determine that regeneration of the first filter 84a and the second filter 84b is required when at least one of the first differential pressure and the second differential pressure is larger than a threshold. The ECU 200, for example, may determine that regeneration of the first filter 84a and the second filter 84b is required when both the first differential pressure and the second differential pressure are larger than a threshold. The ECU 200, for example, may determine that regeneration of the first filter 84a is required when the first differential pressure is larger than a threshold, and may determine that regeneration of the second filter 84b is required when the second differential pressure is larger than a threshold.

[0171] The ECU 200 may execute regeneration control over at least any one of the first filter 84a and the second filter 84b, of which regeneration is required, or may execute regeneration control over both the first filter 84a and the second filter 84b.

[0172] The ECU 200, for example, may execute regeneration control over only the first bank 10a in order to increase the temperature of the first filter 84a when it is determined that regeneration of only the first filter 84a is required, and may execute regeneration control over only the second bank 10b in order to increase the temperature of the second filter 84b when it is determined that regeneration of only the second filter 84b is required.

[0173] Alternatively, the layout of the exhaust passage may be the layout shown in FIG. 8. That is, as in the case of the layout of the exhaust passage shown in FIG. 7, the first catalyst 82a, the first air-fuel ratio sensor 86a and the first oxygen sensor 88a may be provided in the first exhaust passage 80a coupled to the cylinders of the first bank 10a of the engine 10 that is a V-engine having a plurality of banks, the second catalyst 82b, the second air- fuel ratio sensor 86b and the second oxygen sensor 88b may be provided in the second exhaust passage 80b coupled to the cylinders of the second bank 10b, and the filter 84 may be provided in a third exhaust passage 80c of which one end is coupled to a location at which the first exhaust passage 80a and the second exhaust passage 80b are collected.

[0174] In this case, as shown in FIG. 8, the upstream-side pressure sensor 90 is provided at a location upstream of the filter 84 in the third exhaust passage 80c, and the downstream-side pressure sensor 92 is provided at a location downstream of the filter 84 in the third exhaust passage 80c. A method of determining whether regeneration of the filter 84 is required and regeneration control in this case are similar to the method of determining whether regeneration of the filter 84 is required and regeneration control that are described with reference to FIG. 1, so the detailed description thereof will not be repeated.

[0175] Alternatively, the layout of the exhaust passage may be the layout shown in FIG. 9. That is, as in the case of the layout of the exhaust passage shown in FIG. 7, the first catalyst 82a, the first air-fuel ratio sensor 86a, the first oxygen sensor 88a, the first filter 84a, the first upstream-side pressure sensor 90a and the first downstream-side pressure sensor 92a may be provided in the first exhaust passage 80a coupled to the cylinders of the first bank 10a of the engine 10 that is a V-engine, the second catalyst 82b, the second air- fuel ratio sensor 86b, the second oxygen sensor 88b, the second filter 84b, the second upstream-side pressure sensor 90b and the second downstream-side pressure sensor 92b may be provided in the second exhaust passage 80b coupled to the cylinders of the second bank 10b, and one end of the third exhaust passage 80c is coupled to a location at which the first exhaust passage 80a and the second exhaust passage 80b are collected.

[0176] A method of determining whether regeneration of the filters 84a, 84b is required and regeneration control in this case are similar to the method of determining whether regeneration of the filters 84a, 84b is required and regeneration control that are described with reference to FIG. 7, so the detailed description thereof will not be repeated.

[0177] 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:

a gasoline engine configured to start up when driving force of the vehicle exceeds a start-u threshold;

a filter configured to trap particulate matter flowing through an exhaust passage of the gasoline engine;

an electrical storage device;

a converter configured to convert power of the gasoline engine to electric power for charging the electrical storage device and configured to convert electric power of the electrical storage device to driving force of the vehicle; and

a controller configured to:

(a) when regeneration of the filter is required, change the start-up threshold so that a state quantity of the electrical storage device changes in a direction opposite to a direction in which the state quantity varies as a result of execution of regeneration control; and

(b) execute the regeneration control when the state quantity changes into a predetermined range in which execution of the regeneration control is allowed, the regeneration control being executed when the filter is regenerated, the regeneration control being executed so that a temperature of the filter increases to a regeneratable temperature, and the state quantity indicating a state of charge of the electrical storage device.

2. The hybrid vehicle according to claim 2, wherein

the controller is configured to execute the regeneration control such that output of the gasoline engine when regeneration of the filter is ' required is higher than output of the gasoline engine when regeneration of the filter is not required,

the predetermined range is the state quantity lower than a first value, and

the controller is configured to, when the state quantity is higher than the first value, change the start-up threshold to a value larger than the start-up threshold that is used when the state quantity is lower than the first value, the first value being a value obtained by subtracting an amount of increase in the state quantity as a result of execution of the regeneration control from an upper limit value of the state quantity.

3. The hybrid vehicle according to claim 2, wherein the controller is configured to, in any one of a case where the state quantity is lower than the first value and a case where the regeneration control has completed, change the start-up threshold to a value smaller than the start-up threshold that is used when the state quantity is higher than the first value.

4. The hybrid vehicle according to claim 1, wherein

the controller is configured to execute the regeneration control such that an ignition timing of the gasoline engine when regeneration of the filter is required is more retarded than an ignition timing of the gasoline engine when regeneration of the filter is not required,

the predetermined range is the state quantity higher than a second value, and

the controller is configured to, when the state quantity is lower than the second value, change the start-up threshold to a value smaller than the start-up threshold that is used when the state quantity is higher than the second value, the second value being a value obtained by adding an amount of reduction in the state quantity as a result of execution of the regeneration control to a lower limit value of the state quantity.

5. The hybrid vehicle according to claim 4, wherein

the controller is configured to, in any one of a case where the state quantity is higher than the second value and a case where the regeneration control has completed, change the start-up threshold to a value larger than the start-up threshold that is used when the state quantity is lower than the second value.

6. A controller for a hybrid vehicle, the hybrid vehicle including a gasoline engine, a filter, an electrical storage device and a converter,

the gasoline engine being configured to start up when driving force of the vehicle exceeds a start-up threshold,

the filter being configured to trap particulate matter flowing through an exhaust passage of the gasoline engine,

the converter being configured to convert power of the gasoline engine to electric power for charging the electrical storage device and configured to convert electric power of the electrical storage device to driving force of the vehicle,

the controller comprising:

an ECU configured to:

7. A control method for a hybrid vehicle, the hybrid vehicle including a gasoline engine, a filter, an electrical storage device, a converter and an ECU,

the control method comprising:

(a) when regeneration of the filter is required, changing, by the ECU, the start-up threshold so that a state quantity of the electrical storage device changes in a direction opposite to a direction in which the state quantity varies as a result of execution of regeneration control; and

(b) executing, by the ECU, the regeneration control when the state quantity changes into a predetermined range in which execution of the regeneration control is allowed, the regeneration control being executed when the filter is regenerated, the regeneration control being executed so that a temperature of the filter increases to a regeneratable temperature, and the state quantity indicating a state of charge of the electrical storage device.