Patent Description:
There is a known 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, 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.

When PM accumulates in these filters, exhaust resistance increases. Therefore, regeneration control for burning the PM accumulated in the filters is executed by utilizing exhaust heat, or the like, of the engine at appropriate timing.

In the hybrid vehicle, there is known that the vehicle is controlled in accordance with any one of a plurality of control modes having different numbers of opportunities for the engine to operate. For example, International Application Publication No. <CIT> describes a controller for a hybrid vehicle. The controller varies an engine start-up condition during a charge sustaining (CS) mode and an engine start-up condition during a charge depleting (CD) mode from each other. Other hybrid vehicles and control methods are disclosed in <CIT> and <CIT>.

Incidentally, the CD mode described in Internal Application Publication No. <CIT> has a smaller number of opportunities for the engine to operate than the CS mode, so the CD mode is a control mode in which the vehicle tends to travel in a state where the engine is stopped. Therefore, in a hybrid vehicle on which a filter for trapping PM is mounted, if regeneration control is executed over the filter during the CD mode, there is a case where the engine stops before regeneration of the filter completes and, as a result, regeneration of the filter does not complete.

The invention provides a hybrid vehicle and a control method for a hybrid vehicle, which reliably complete regeneration of a filter when a control mode having a smaller number of opportunities for an engine to operate is selected.

An aspect of the invention provides a hybrid vehicle according to claim <NUM>.

With this configuration, when the filter is regenerated, the vehicle is controlled in the charge sustaining mode having a larger number of opportunities for the engine to operate than the charge depleting mode. Thus, it is possible to extend the operating time of the engine as compared to when the vehicle is controlled in the charge depleting mode. Therefore, it is possible to reliably complete regeneration of the filter by increasing the temperature of the filter to a regeneratable temperature.

In the above aspect, the ECU may be configured to change the control mode of the hybrid vehicle from the charge depleting mode to the charge sustaining mode when the control mode is the charge depleting mode and when the regeneration of the filter is required.

With this configuration, when the control mode is the charge depleting mode and when the filter is regenerated, the control mode of the vehicle is changed from the charge depleting mode to the charge sustaining mode. Thus, it is possible to increase the number of opportunities for the engine to operate as compared to when the control mode is the charge depleting mode. Therefore, it is possible to extend the operating time of the engine as compared to when the control mode is the charge depleting mode, so it is possible to reliably complete regeneration of the filter by increasing the temperature of the filter to the regeneratable temperature.

In the above aspect, the ECU may be configured to keep the charge sustaining mode until regeneration of the filter completes when the filter is regenerated and when the control mode is changed into the charge sustaing mode.

With this configuration, the charge sustaining mode is kept until regeneration completes, so it is possible to keep a state where there is a large number of opportunities for the engine to operate as compared to when the control mode is the charge depleting mode. Therefore, it is possible to reliably complete regeneration of the filter by increasing the temperature of the filter to the regeneratable temperature.

In the above aspect, the ECU may be configured to change the control mode from the charge sustaining mode to the charge depleting mode after regeneration of the filter has completed when the filter is regenerated and when the control mode is changed into the charge sustaining mode.

With this configuration, the control mode of the vehicle is changed into the charge depleting mode after regeneration of the filter has completed. Thus, it is possible to return from a state where there is a large number of opportunities for the engine to operate to a state before regeneration of the filter is started. Therefore, it is possible to quickly eliminate the state where there is a large number of opportunities for the engine to operate although a user recognizes that the charge depleting mode is selected.

In the above aspect, the hybrid vehicle may further include an electrical storage device. The electrical storage device is configured to be charged by using a power of the engine. The ECU may be configured to change the control mode from the charge sustaining mode to the charge depleting mode when regeneration of the filter completes and when a state of charge of the electrical storage device is higher than or equal to a predetermined value. The ECU may be configured to keep the charge sustaining mode mode when regeneration of the filter completes and when the state of charge is lower than the predetermined value.

With this configuration, it is possible to change the control mode of the vehicle into the charge depleting mode when regeneration of the filter has completed and when the state of charge of the electrical storage device is higher than or equal to the predetermined value. In this way, it is possible to return a state where there is a large number of opportunities for the engine to operate to a state before regeneration of the filter is started. It is possible to keep the charge depleting mode when regeneration of the filter has completed and when the SOC of the electrical storage device is lower than the predetermined value. Thus, it is possible to suppress a decrease in the state of charge of the electrical storage device.

In the above aspect, the ECU may be configured to change the control mode from the charge depleting mode to the charge sustaining mode after the engine has been started up when the control mode is the charge depleting mode and when regeneration of the filter is required.

With this configuration, when regeneration of the filter is required, the control mode of the vehicle is changed into the charge sustaining mode after the engine is started up. In this way, it is possible to increase the number of opportunities for the engine to operate as compared to when the control mode is the first control mode. Therefore, it is possible to reliably complete regeneration of the filter by increasing the temperature of the filter to the regeneratable temperature.

In the above aspect, the ECU may be configured to start up the engine when the control mode is the charge depleting mode and when a power of the hybrid vehicle exceeds a first start-up threshold. The ECU may be configured to start up the engine when the control mode is the charge sustaining mode and when the power of the hybrid vehicle exceeds a second start-up threshold. The second start-up threshold is a value lower than the first start-up threshold.

With this configuration, because the second start-up threshold is lower than the first start-up threshold, it is possible to increase the number of opportunities for the engine to operate when the control mode is the charge sustaining mode as compared to the number of opportunities for the engine to operate when the control mode is the first control mode.

In the above aspect, the ECU may be configured to start up the engine when the control mode is the charge depleting mode and when a speed of the vehicle exceeds a third start-up threshold. The ECU may be configured to start up the engine when the control mode is the charge sustaining mode and when the speed of the vehicle exceeds a fourth start-up threshold. The fourth start-up threshold is a value lower than the third start-up threshold.

With this configuration, because the second start-up threshold is lower than the first start-up threshold, it is possible to increase the number of opportunities for the engine to operate when the control mode is the charge sustaining mode as compared to the number of opportunities for the engine to operate when the control mode is the charge depleting mode.

In the above aspect, the engine may be a gasoline engine. The gasoline engine is smaller in the amount of PM generated than a diesel engine having a comparable power, and may be permitted to temporarily stop the engine even when regeneration of the filter is required as compared to a diesel engine. Therefore, as a result of a change of the control mode into the charge sustaining mode, the number of opportunities for the engine to operate is increased, and it is possible to reliably complete regeneration of the filter by increasing the temperature of the filter to the regeneratable temperature.

Another aspect of the invention provides a control method according to claim <NUM>.

According to the invention, when the filter is regenerated, the vehicle is controlled in the charge sustaining mode having a larger number of opportunities for the engine to operate than the charge depleting mode. Thus, it is possible to extend the operating time of the engine as compared to when the vehicle is controlled in the charge depleting mode. Therefore, it is possible to reliably complete regeneration of the filter by increasing the temperature of the filter to a regeneratable temperature. Thus, it is possible to provide the hybrid vehicle and the control method for a hybrid vehicle, which reliably complete regeneration of the filter in the case where the control mode having a smaller number of opportunities for the engine to operate is selected.

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. A first embodiment will be described as following. The overall block diagram of a hybrid vehicle <NUM> (hereinafter, simply referred to as vehicle <NUM>) according to the present embodiment will be described with reference to <FIG>. The vehicle <NUM> includes a transmission <NUM>, an engine <NUM>, a drive shaft <NUM>, a power control unit (PCU) <NUM>, a battery <NUM>, drive wheels <NUM>, a charging device <NUM>, an accelerator pedal <NUM>, and an electronic control unit (ECU) <NUM>.

The transmission <NUM> includes an output shaft <NUM>, a first motor generator (hereinafter, referred to as first MG) <NUM>, a second motor generator (hereinafter, referred to as second MG) <NUM>, a power split device <NUM>, and a reduction gear <NUM>.

The engine <NUM> includes a plurality of cylinders <NUM>. One end of an exhaust passage <NUM> is coupled to the engine <NUM>. The other end of the exhaust passage <NUM> is coupled to a muffler (not shown). A catalyst <NUM> and a filter <NUM> are provided in the exhaust passage <NUM>.

A wheel speed sensor <NUM>, an air-fuel ratio sensor <NUM>, an oxygen sensor <NUM>, an upstream-side pressure sensor <NUM>, a downstream-side pressure sensor <NUM>, a current sensor <NUM>, a voltage sensor <NUM>, a battery temperature sensor <NUM> and a pedal stroke sensor <NUM> are connected to the ECU <NUM> so that the ECU <NUM> is able to receive various signals from the sensors.

The thus configured vehicle <NUM> travels by using driving force that is output from at least one of the engine <NUM> or the second MG <NUM>. Power that is generated by the engine <NUM> is split by the power split device <NUM> into two paths. One of the two paths is a path through which power is transmitted to the drive wheels <NUM> via the reduction gear <NUM>. The other one of the two paths is a path through which power is transmitted to the first MG <NUM>.

The first MG <NUM> and the second MG <NUM> each are, for example, a three-phase alternating-current rotary electric machine. The first MG <NUM> and the second MG <NUM> are driven by the PCU <NUM>.

The first MG <NUM> has the function of a generator (power generating device) that generates electric power by using power split from the power of the engine <NUM> by the power split device <NUM> and then charges the battery <NUM> via the PCU <NUM>. The first MG <NUM> rotates a crankshaft upon reception of electric power from the battery <NUM>. The crankshaft is an output shaft of the engine <NUM>. Thus, the first MG <NUM> has the function of a starter that starts up the engine <NUM>.

The second MG <NUM> has the function of a drive motor that provides driving force to the drive wheels <NUM> by using at least one of electric power stored in the battery <NUM> or electric power generated by the first MG <NUM>. The second MG <NUM> has the function of a generator for charging the battery <NUM> via the PCU <NUM> by using electric power generated by regenerative braking.

The engine <NUM> is a gasoline engine, and is controlled on the basis of a control signal S1 from the ECU <NUM>.

In the present embodiment, the engine <NUM> includes four cylinders <NUM>, 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 <NUM>.

The engine <NUM> is not limited to an in-line four-cylinder engine as shown in <FIG>. For example, the engine <NUM> 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.

The engine <NUM> includes fuel injection devices (not shown) corresponding to the plurality of cylinders <NUM>. The fuel injection devices may be respectively provided in the plurality of cylinders <NUM> or may be respectively provided in intake ports of the cylinders.

In the thus configured engine <NUM>, the ECU <NUM> controls a fuel injection amount to each of the plurality of cylinders <NUM> by injecting fuel in an appropriate amount at appropriate timing to each of the plurality of cylinders <NUM> or stopping injection of fuel to each of the plurality of cylinders <NUM>.

The catalyst <NUM> provided in the exhaust passage <NUM> oxidizes unburned components contained in exhaust gas that is emitted from the engine <NUM>, or reduces oxidized components. Specifically, the catalyst <NUM> 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 <NUM> is able to reduce the oxidized components and occlude released oxygen. Therefore, the percentage of nitrogen dioxide (NO<NUM>) contained in exhaust gas increases because of the catalyst <NUM>.

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

The air-fuel ratio sensor <NUM> is provided at a location upstream of the catalyst <NUM> in the exhaust passage <NUM>. The oxygen sensor <NUM> is provided at a location downstream of the catalyst <NUM> and upstream of the filter <NUM> in the exhaust passage <NUM>.

The air-fuel ratio sensor <NUM> 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 <NUM>. The air-fuel ratio sensor <NUM> detects the air-fuel ratio in exhaust gas, and transmits a signal indicating the detected air-fuel ratio to the ECU <NUM>.

The oxygen sensor <NUM> 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 <NUM>. The oxygen sensor <NUM> detects the concentration of oxygen in exhaust gas, and transmits a signal indicating the detected concentration of oxygen to the ECU <NUM>. The ECU <NUM> calculates the air-fuel ratio on the basis of the received signal.

The upstream-side pressure sensor <NUM> is provided at a location upstream of the filter <NUM> and downstream of the oxygen sensor <NUM> in the exhaust passage <NUM>. The downstream-side pressure sensor <NUM> is provided at a location downstream of the filter <NUM> in the exhaust passage <NUM>.

Each of the upstream-side pressure sensor <NUM> and the downstream-side pressure sensor <NUM> is used to detect the pressure in the exhaust passage <NUM>. The upstream-side pressure sensor <NUM> transmits a signal (first pressure detection signal) indicating the detected pressure in the exhaust passage <NUM> (upstream-side pressure) to the ECU <NUM>. The downstream-side pressure sensor <NUM> transmits a signal (second pressure detection signal) indicating the detected pressure in the exhaust passage <NUM> (downstream-side pressure) to the ECU <NUM>.

The power split device <NUM> is configured to be able to split power, which is generated by the engine <NUM>, into a path toward the drive shaft <NUM> via the output shaft <NUM> and a path toward the first MG <NUM>. The power split device <NUM> 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 <NUM> is connected to the sun gear, the output shaft of the engine <NUM> is connected to the planetary gear, and the output shaft <NUM> is connected to the ring gear. Thus, the engine <NUM>, the first MG <NUM> and the second MG <NUM> are allowed to be mechanically connected to the power split device <NUM>.

The output shaft <NUM> is also connected to the rotor of the second MG <NUM>. The output shaft <NUM> is mechanically coupled to the drive shaft <NUM> via the reduction gear <NUM>. The drive shaft <NUM> is used to rotationally drive the drive wheels <NUM>. A transmission may be further assembled between the rotary shaft of the second MG <NUM> and the output shaft <NUM>.

The PCU <NUM> converts direct-current power, which is supplied from the battery <NUM>, to alternating-current power, and drives the first MG <NUM> and the second MG <NUM>. The PCU <NUM> converts alternating-current power, generated by the first MG <NUM> or the second MG <NUM>, to direct-current power, and charges the battery <NUM>. For example, the PCU <NUM> 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 <NUM>.

The battery <NUM> is an electrical storage device, and is a rechargeable direct-current power supply. The battery <NUM> includes, for example, a nickel-metal hydride secondary battery or a lithium ion secondary battery. The voltage of the battery <NUM> is , for example, about <NUM> V. Not only the battery <NUM> is charged with electric power generated by the first MG <NUM> and/or the second MG <NUM> as described above but also the battery <NUM> may be charged with electric power that is supplied from an external power supply (not shown). The battery <NUM> is not limited to a secondary battery. The battery <NUM> 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 <NUM> may be equipped with a charging device that allows the battery <NUM> to be charged with the use of an external power supply.

The current sensor <NUM>, the voltage sensor <NUM> and the battery temperature sensor <NUM> are provided at the battery <NUM>. The current sensor <NUM> detects the current IB of the battery <NUM>. The current sensor <NUM> transmits a signal indicating the current IB to the ECU <NUM>. The voltage sensor <NUM> detects the voltage VB of the battery <NUM>. The voltage sensor <NUM> transmits a signal indicating the voltage VB to the ECU <NUM>. The battery temperature sensor <NUM> detects the battery temperature TB of the battery <NUM>. The battery temperature sensor <NUM> transmits a signal indicating the battery temperature TB to the ECU <NUM>.

The ECU <NUM> estimates a state of charge (hereinafter, referred to as SOC) of the battery <NUM> on the basis of the current IB, voltage VB and battery temperature TB of the battery <NUM>. The ECU <NUM> 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 <NUM> on the basis of the estimated OCV and a predetermined map. Alternatively, the ECU <NUM> may estimate the SOC of the battery <NUM> by, for example, integrating a charge current of the battery <NUM> and a discharge current of the battery <NUM>.

The charging device <NUM> charges the battery <NUM> with electric power that is supplied from an external power supply <NUM> when a charging plug <NUM> is attached to the vehicle <NUM> during a stop of the vehicle <NUM>. The charging plug <NUM> is connected to one end of a charging cable <NUM>. The other end of the charging cable <NUM> is connected to the external power supply <NUM>. The positive electrode terminal of the charging device <NUM> is connected to a power supply line PL. The power supply line PL connects the positive electrode terminal of the PCU <NUM> to the positive electrode terminal of the battery <NUM>. The negative electrode terminal of the charging device <NUM> is connected to a ground line NL. The ground line NL connects the negative electrode terminal of the PCU <NUM> to the negative electrode terminal of the battery <NUM>. In addition to or instead of a charging method in which electric power is supplied from the external power supply <NUM> to the battery <NUM> of the vehicle <NUM> through contact power supply using the charging plug <NUM>, and the like, a charging method in which electric power is supplied from the external power supply <NUM> to the battery <NUM> of the vehicle <NUM> through contactless power supply, such as a resonance method and electromagnetic induction, may be used.

The wheel speed sensor <NUM> detects the rotation speed Nw of one of the drive wheels <NUM>. The wheel speed sensor <NUM> transmits a signal indicating the detected rotation speed Nw to the ECU <NUM>. The ECU <NUM> calculates a vehicle speed V on the basis of the received rotation speed Nw. The ECU <NUM> may calculate the vehicle speed V on the basis of the rotation speed Nm2 of the second MG <NUM> instead of the rotation speed Nw.

The accelerator pedal <NUM> is provided at a driver seat. The pedal stroke sensor <NUM> is provided at the accelerator pedal <NUM>. The pedal stroke sensor <NUM> detects a stroke (depression amount) AP of the accelerator pedal <NUM>. The pedal stroke sensor <NUM> transmits a signal indicating the stroke AP to the ECU <NUM>. Instead of the pedal stroke sensor <NUM>, 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 <NUM> by an occupant of the vehicle <NUM>.

The ECU <NUM> generates a control signal S1 for controlling the engine <NUM>, and outputs the generated control signal S1 to the engine <NUM>. The ECU <NUM> generates a control signal S2 for controlling the PCU <NUM>, and outputs the generated control signal S2 to the PCU <NUM>.

The ECU <NUM> is a controller that controls an overall hybrid system, that is, the charge/discharge state of the battery <NUM> and the operating states of the engine <NUM>, first MG <NUM> and second MG <NUM>, so that the vehicle <NUM> is able to operate at the highest efficiency through control over the engine <NUM>, the PCU <NUM>, and the like.

The ECU <NUM> calculates a required vehicle power corresponding to the stroke AP of the accelerator pedal <NUM> and the vehicle speed V. The accelerator pedal <NUM> is provided at the driver seat. When an auxiliary is operated, the ECU <NUM> 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 <NUM> is charged, the ECU <NUM> adds a power, required to charge the battery, to the calculated required vehicle power. The ECU <NUM> controls the torque of the first MG <NUM>, the torque of the second MG <NUM> or the output of the engine <NUM> on the basis of the calculated required vehicle power. In the present embodiment, a configuration, including the transmission <NUM> and the PCU <NUM>, corresponds to a power conversion device. The transmission <NUM> includes the first MG <NUM> and the second MG <NUM>. The PCU <NUM> exchanges electric power with the first MG <NUM> or the second MG <NUM>. The power conversion device is able to convert the power of the engine <NUM> to electric power for charging the battery <NUM>, and is able to convert the electric power of the battery <NUM> to power for propelling the vehicle <NUM>.

In the present embodiment, the ECU <NUM> controls the PCU <NUM> and the engine <NUM> in accordance with any one of control modes. The control modes include a mode (hereinafter, referred to as charge depleting (CD) mode) and a mode (hereinafter, referred to as charge sustaining (CS) mode). In the CD mode, the vehicle <NUM> travels by consuming electric power of the battery <NUM> without keeping the SOC of the battery <NUM>. In the CS mode, the engine <NUM> is operated or stopped and the vehicle <NUM> travels while keeping the SOC of the battery <NUM>. The CD mode is not specifically limited to not keeping the SOC, and may be, for example, a mode that gives a higher priority to traveling by consuming electric power of the battery <NUM> in an EV mode than to traveling while keeping the SOC of the battery <NUM>. The control modes may include a control mode other than the CD mode or the CS mode. The control modes are not limited to control over the vehicle <NUM> while the vehicle <NUM> is traveling. The control modes are used in control over the vehicle <NUM> while the vehicle <NUM> is traveling or while the vehicle <NUM> is stopped.

The ECU <NUM>, for example, automatically changes between the CD mode and the CS mode. For example, the ECU <NUM> controls the PCU <NUM> and the engine <NUM> in accordance with the CD mode when the SOC of the battery <NUM> is higher than a threshold SOC(<NUM>), and controls the PCU <NUM> and the engine <NUM> in accordance with the CS mode when the SOC of the battery <NUM> is lower than the threshold SOC(<NUM>). The ECU <NUM> may change between the CD mode and the CS mode in response to the fact that an operation member, such as a switch and a lever, is operated by a user in order to change the control mode.

While the vehicle <NUM> is traveling in accordance with the CD mode, because the operation of the engine <NUM> for power generation is suppressed (that is, because a decrease in the SOC of the battery <NUM> is permitted), the SOC of the battery <NUM> is not kept, electric power of the battery <NUM> is consumed in accordance with an increase in travel distance, and the SOC of the battery <NUM> decreases.

During the CD mode, the ECU <NUM> controls the PCU <NUM> so that the vehicle <NUM> travels by using only the output of the second MG <NUM> as long as a required vehicle power does not exceed a start-up threshold Pr(<NUM>) of the engine <NUM>.

When the vehicle <NUM> is traveling by using only the output of the second MG <NUM> during the CD mode, after the required vehicle power exceeds the start-up threshold Pr(<NUM>) of the engine <NUM> (that is, after it is determined that the required vehicle power is not satisfied by only the output of the second MG <NUM>), the ECU <NUM> starts up the engine <NUM>, and controls the PCU <NUM> and the engine <NUM> so that the required vehicle power is satisfied by the output of the second MG <NUM> and the output of the engine <NUM>. That is, the CD mode is a control mode in which the operation of the engine <NUM> for satisfying the required vehicle power is allowed although the operation of the engine <NUM> for power generation is suppressed. Instead of the required vehicle power, the engine <NUM> may be started up when an actual power of the vehicle <NUM> exceeds a start-up threshold of the engine <NUM>. When the required vehicle power becomes lower than a stop threshold of the engine <NUM> during the CD mode, the ECU <NUM> stops the engine <NUM>. The stop threshold during the CD mode is a predetermined value lower than or equal to the start-up threshold Pr(<NUM>).

When the vehicle <NUM> travels in accordance with the CS mode, the operation of the engine <NUM> for power generation is allowed, and a decrease in the SOC of the battery <NUM> is suppressed by keeping the SOC of the battery <NUM> or recovering the SOC of the battery <NUM>.

For example, the ECU <NUM> may execute charge/discharge control over the battery <NUM> so that the SOC of the battery <NUM> falls within a predetermined control range (for example, a control range including the above-described threshold SOC(<NUM>)) during the CS mode or may execute charge/discharge control over the battery <NUM> so that the SOC of the battery <NUM> keeps a predetermined target SOC (for example, the above-described threshold SOC(<NUM>)).

Charge control over the battery <NUM> includes, for example, charge control that uses regenerated electric power that is generated through regenerative braking of the second MG <NUM> and charge control that uses electric power generated by the first MG <NUM> by using the power of the engine <NUM>.

During the CS mode, when the SOC of the battery <NUM> significantly exceeds the predetermined control range or the predetermined target SOC, the ECU <NUM> controls the PCU <NUM> so that the vehicle travels by using only the output of the second MG <NUM> as long as the required vehicle power does not exceed a start-up threshold Pr(<NUM>) of the engine <NUM>.

When the vehicle <NUM> is traveling by using only the output of the second MG <NUM> during the CS mode as described above, after the required vehicle power exceeds the start-up threshold Pr(<NUM>) of the engine <NUM> (that is, after it is determined that the required vehicle power is not satisfied by only the output of the second MG <NUM>), the ECU <NUM> starts up the engine <NUM>, and controls the PCU <NUM> and the engine <NUM> so that the required vehicle power is satisfied by both the output of the second MG <NUM> and the output of the engine <NUM>. That is, the CS mode is a control mode in which the operation of the engine <NUM> for power generation or the operation of the engine <NUM> for satisfying the required vehicle power is allowed. When the required vehicle power becomes lower than a stop threshold of the engine <NUM> during the CS mode, the ECU <NUM> stops the engine <NUM>. The stop threshold during the CS mode is a predetermined value lower than or equal to the start-up threshold Pr(<NUM>).

In the present embodiment, description will be made on the assumption that the start-up threshold Pr(<NUM>) during the CD mode is higher than the start-up threshold Pr(<NUM>) during the CS mode and the stop threshold during the CD mode is higher than the stop threshold during the CS mode. Each of the start-up thresholds Pr(<NUM>), Pr(<NUM>) is a value lower than or equal to an upper limit value of the output of the second MG <NUM> and lower than or equal to an upper limit value (Wout) of the output of the battery <NUM>. With this configuration, as will be described below, there occurs a difference in opportunity for the engine <NUM> to operate between during the CD mode and during the CS mode.

For example, as shown in <FIG>, assuming the case where a required output of the vehicle <NUM> similarly changes during the CD mode and during the CS mode.

In this case, during the CS mode, in a period from time t(<NUM>) to time t(<NUM>), a period from time t(<NUM>) to time t(<NUM>), a period from time t(<NUM>) to time t(<NUM>) and a period from time t(<NUM>) to time t(<NUM>), the required output exceeds the start-up threshold Pr(<NUM>) of the engine <NUM>, with the result that the engine <NUM> is operated.

On the other hand, during the CD mode, only in a period from time t(<NUM>) to time t(<NUM>), the required output exceeds the start-up threshold Pr(<NUM>) of the engine <NUM>, and the engine <NUM> is operated.

Thus, when the control mode is the CD mode, the number of opportunities for the engine <NUM> to operate (operating period) is smaller than that when the control mode is the CS mode. In other words, the number of opportunities for the engine <NUM> to operate (operating period) when the control mode is the CS mode is larger than that when the control mode is the CD mode.

In the vehicle <NUM> having the above-described configuration, because the CD mode has a smaller number of opportunities for the engine <NUM> to operate than the CS mode, the CD mode is a control mode in which the vehicle <NUM> tends to travel in a state where the engine <NUM> is stopped. Therefore, in the vehicle <NUM> on which the filter <NUM> for trapping PM is mounted, even when the engine <NUM> operates during the CD mode, there is a case where the engine <NUM> stops before regeneration of the filter <NUM> completes and regeneration of the filter <NUM> does not complete.

Therefore, the present embodiment has such a characteristic that, when the filter <NUM> is regenerated, the ECU <NUM> controls the vehicle <NUM> in the CS mode having a larger number of opportunities for the engine <NUM> to operate than the CD mode.

That is, in the present embodiment, the ECU <NUM> changes the control mode from the CD mode to the CS mode when the control mode is the CD mode and when regeneration of the filter <NUM> is required. Thus, the number of opportunities for the engine <NUM> to operate is increased, and regeneration of the filter <NUM> is completed.

When regeneration of the filter <NUM> is required and when the control mode has been changed into the CS mode, the ECU <NUM> keeps the CS mode until regeneration of the filter <NUM> completes.

In addition, when regeneration of the filter <NUM> is required and when the control mode has been changed into the CS mode, the ECU <NUM> may change the control mode of the vehicle <NUM> from the CS mode to the CD mode after regeneration of the filter <NUM> has completed.

For example, in the case where regeneration of the filter <NUM> has completed, the ECU <NUM> changes the control mode from the CS mode to the CD mode when the SOC of the battery <NUM> is higher than or equal to a threshold SOC(<NUM>), and keeps the CS mode when the SOC of the battery <NUM> is lower than the threshold SOC(<NUM>).

<FIG> shows the functional block diagram of the ECU <NUM> mounted on the vehicle <NUM> according to the present embodiment. The ECU <NUM> includes a mode determination unit <NUM>, a regeneration request determination unit <NUM>, a completion determination unit <NUM>, an SOC determination unit <NUM>, and a mode change unit <NUM>.

The mode determination unit <NUM> determines whether the currently selected control mode is the CD mode.

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

Specifically, when the difference between the upstream-side pressure detected by the upstream-side pressure sensor <NUM> and the downstream-side pressure detected by the downstream-side pressure sensor <NUM> is larger than a threshold, the regeneration request determination unit <NUM> determines that regeneration of the filter <NUM> is required. The threshold is used to estimate that the amount of PM accumulated in the filter <NUM> 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 <NUM>.

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

The completion determination unit <NUM> determines whether regeneration of the filter <NUM> has completed. The completion determination unit <NUM> determines, by using the upstream-side pressure sensor <NUM> and the downstream-side pressure sensor <NUM>, whether regeneration of the filter <NUM> has completed.

Specifically, when the difference between the upstream-side pressure that is detected by the upstream-side pressure sensor <NUM> and the downstream-side pressure that is detected by the downstream-side pressure sensor <NUM> is smaller than a threshold, the completion determination unit <NUM> determines that regeneration of the filter <NUM> has completed.

The threshold that is used to determine whether regeneration of the filter <NUM> has completed may be a predetermined value that is adapted by an experiment or a design or may be a value that changes in accordance with the operating state of the engine <NUM>.

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

When the completion determination unit <NUM> determines that regeneration of the filter <NUM> has completed, the SOC determination unit <NUM> determines whether the SOC of the battery <NUM> is higher than or equal to the threshold SOC(<NUM>). The threshold SOC(<NUM>) is a threshold of the SOC for changing between the CD mode and the CS mode.

When the mode determination unit <NUM> determines that the control mode is the CD mode and when the regeneration request determination unit <NUM> determines that regeneration of the filter <NUM> is required, the mode change unit <NUM> changes the control mode from the CD mode to the CS mode.

When the mode determination unit <NUM> determines that the control mode is not the CD mode (the control mode is the CS mode) and when the regeneration request determination unit <NUM> determines that regeneration of the filter <NUM> is required, the mode change unit <NUM> keeps the CS mode.

When the completion determination unit <NUM> determines that regeneration of the filter <NUM> has completed and when the SOC determination unit <NUM> determines that the SOC of the battery <NUM> is higher than or equal to the threshold SOC(<NUM>), the mode change unit <NUM> changes the control mode from the CS mode to the CD mode.

When the completion determination unit <NUM> determines that regeneration of the filter <NUM> has completed and when the SOC determination unit <NUM> determines that the SOC of the battery <NUM> is lower than the threshold SOC(<NUM>), the mode change unit <NUM> keeps the CS mode.

A control process that is executed by the ECU <NUM> mounted on the vehicle <NUM> according to the present embodiment will be described with reference to <FIG>.

In step (hereinafter, step is abbreviated as "S") <NUM>, the ECU <NUM> determines whether the control mode is the CD mode. For example, on the basis of a state (on state or off state) of a flag (mode determination flag) that changes each time the control mode changes, the ECU <NUM> determines whether the currently selected control mode is the CD mode.

For example, it is assumed that the mode determination flag enters the on state when the CD mode is selected, and enters the off state when the CS mode is selected. For example, when the mode determination flag is in the on state, the ECU <NUM> may determine that the CD mode is selected; whereas, when the mode determination flag is in the off state, the ECU <NUM> may determine that the CD mode is not selected (that is, the CS mode is selected).

When it is determined that the control mode is the CD mode (YES in S102), the process proceeds to S104. Otherwise (NO in S102), the process proceeds to S114.

In S104, the ECU <NUM> determines whether regeneration of the filter <NUM> is required. For example, when the control mode is the CD mode and when the difference between the upstream-side pressure and downstream-side pressure of the filter <NUM> is larger than the threshold (that is, the amount of PM accumulated in the filter <NUM> is larger than or equal to the predetermined amount), the ECU <NUM> determines that regeneration of the filter <NUM> is required. When the ECU <NUM> determines that regeneration of the filter <NUM> is required, the ECU <NUM> sets a regeneration request flag to an on state.

When it is determined that regeneration of the filter <NUM> is required (YES in S104), the process proceeds to S106. Otherwise (NO in S104), the process ends.

In S106, the ECU <NUM> changes the control mode from the CD mode to the CS mode. For example, when both the regeneration request flag and the mode determination flag are in the on state, the ECU <NUM> may change the control mode from the CD mode to the CS mode.

In S108, the ECU <NUM> determines whether regeneration of the filter <NUM> has completed. Determination as to whether regeneration of the filter <NUM> has completed is as described above, so the detailed description thereof will not be repeated.

For example, when the regeneration request flag is in the on state, the ECU <NUM> determines whether regeneration of the filter <NUM> has completed. When the ECU <NUM> determines that regeneration of the filter <NUM> has completed, the ECU <NUM> sets the regeneration request flag to the off state.

When it is determined that regeneration of the filter <NUM> has completed (YES in S108), the process proceeds to S110. Otherwise, (NO in S108), the process is returned to S106.

In S110, the ECU <NUM> determines whether the SOC of the battery <NUM> is higher than or equal to the threshold SOC(<NUM>). For example, when the regeneration request flag has been changed from the on state to the off state, the ECU <NUM> may determine whether the SOC of the battery <NUM> is higher than or equal to the threshold SOC(<NUM>), and, when the SOC of the battery <NUM> is higher than or equal to the threshold SOC(<NUM>), the ECU <NUM> may set the SOC determination flag to the on state.

When it is determined that the SOC of the battery <NUM> is higher than or equal to the threshold SOC(<NUM>) (YES in S110), the process proceeds to S112. Otherwise (NO in S110), the process proceeds to S114.

In S112, the ECU <NUM> changes the control mode from the CS mode to the CD mode. For example, when the regeneration request flag is changed from the on state to the off state and the SOC determination flag is in the on state, the ECU <NUM> may change the control mode from the CS mode to the CD mode.

In S114, the ECU <NUM> keeps the CS mode. For example, when the mode determination flag is in the off state, the ECU <NUM> may keep the CS mode. Alternatively, for example, when the regeneration request flag is changed from the on state to the off state and when the SOC determination flag is in the off state, the ECU <NUM> may keep the CS mode.

The operation of the ECU <NUM> mounted on the vehicle <NUM> according to the present embodiment based on the above-described structure and flowchart will be described with reference to <FIG> and <FIG>.

Hereinafter, the regeneration operation of the filter <NUM> in the case where the control mode is changed into the CS mode at the time when regeneration of the filter <NUM> is required during the CD mode will be described with reference to <FIG>.

For example, it is assumed that the control mode is the CD mode (YES in S102)As shown in <FIG>, when the required output exceeds the start-up threshold Pr(<NUM>) of the engine <NUM> at time t(<NUM>), the engine <NUM> starts up. After start-up of the engine <NUM>, when the differential pressure between the upstream-side pressure and the downstream-side pressure does not exceed the threshold (that is, when the amount of PM accumulated in the filter <NUM> is smaller than the predetermined amount), it is not determined that regeneration of the filter <NUM> is required (NO in S104), so the regeneration request flag remains in the off state. When the engine <NUM> is operated, the temperature of the filter <NUM> increases by the heat of exhaust gas of the engine <NUM>. When the required output becomes lower than the start-up threshold Pr(<NUM>) of the engine <NUM> at time t(<NUM>), the engine <NUM> is stopped. When the engine <NUM> is stopped, an increase in the temperature of the filter <NUM> is suppressed. Therefore, the temperature of the filter <NUM> decreases with a lapse of time from time t(<NUM>).

When the required output exceeds the start-up threshold Pr(<NUM>) of the engine <NUM> at time t(<NUM>), the engine <NUM> starts up again. After start-up of the engine <NUM>, when the differential pressure between the upstream-side pressure and downstream-side pressure of the filter <NUM> exceeds a threshold (that is, the amount of PM accumulated in the filter <NUM> becomes larger than the predetermined amount), it is determined that regeneration of the filter <NUM> is required (YES in S104), so the regeneration request flag enters the on state.

As a result of the fact that the regeneration request flag enters the on state, the control mode is changed from the CD mode to the CS mode (S106). When the control mode is changed from the CD mode to the CS mode, the start-up threshold of the engine <NUM> is changed from Pr(<NUM>) to Pr(<NUM>). Therefore, in a period from time t(<NUM>) to time t(<NUM>), the engine <NUM> is more easy to start up than when the CS mode is selected as described with reference to <FIG>.

Thus, in a period from time t(<NUM>) to time t(<NUM>), a period from time t(<NUM>) to time t(<NUM>), a period from time t(<NUM>) to time t(<NUM>) and a period from time t(<NUM>) to time t(<NUM>), when the required output exceeds the start-up threshold Pr(<NUM>) of the engine <NUM>, the engine <NUM> is operated.

On the other hand, in a period from time t(<NUM>) to time t(<NUM>), a period from time t(<NUM>) to time t(<NUM>) and a period from time t(<NUM>) to time t(<NUM>), when the required output does not exceed the start-up threshold Pr(<NUM>) of the engine <NUM> (when the required output becomes lower than the stop threshold during the CS mode), the engine <NUM> is stopped.

Therefore, in a period from time t(<NUM>) to time t(<NUM>), the SOC is controlled so that the SOC at the timing of time t(<NUM>) at which the control mode has been changed into the CS mode is kept. As a result, the SOC of the battery <NUM> fluctuates with reference to the SOC at the timing of time t(<NUM>) at which the control mode has been changed into the CS mode.

When the engine <NUM> is operated, the temperature of the filter <NUM> increases by the heat of exhaust gas of the engine <NUM>. On the other hand, when the engine <NUM> is stopped, an increase in the temperature of the filter <NUM> is suppressed.

Therefore, after the timing at which the control mode has been changed from the CD mode to the CS mode at time t(<NUM>), the temperature of the filter <NUM> increases in a stepwise manner with a lapse of time, and exceeds a regeneratable temperature Tf(<NUM>) after time t(<NUM>). When the temperature of the filter <NUM> exceeds the regeneratable temperature Tf(<NUM>), the filter <NUM> can be regenerated. At this time, in the filter <NUM>, for example, PM is burned and removed by an oxygen component that is contained in gas flowing through the exhaust passage, and regeneration of the filter advances.

When it is determined at time t(<NUM>) that regeneration of the filter <NUM> has completed (YES in S108), because the SOC of the battery <NUM> is higher than or equal to the threshold SOC(<NUM>) (YES in S110), the regeneration request flag is changed to the off state, and the control mode is changed from the CS mode to the CD mode (S112).

When the control mode is changed from the CS mode to the CD mode, the start-up threshold of the engine <NUM> is changed from Pr(<NUM>) to Pr(<NUM>). As a result, the required output does not exceed Pr(<NUM>) after time t(<NUM>), so the engine <NUM> is kept stopped.

When the control mode is changed into the CD mode from time t(<NUM>), the number of opportunities for the engine <NUM> to operate is smaller than that during the CS mode. Therefore, the SOC of the battery <NUM> decreases (is not kept) from time t(<NUM>).

When it is determined that regeneration of the filter <NUM> has completed (YES in S108), and when the SOC of the battery <NUM> is lower than the threshold SOC(<NUM>) (NO in S110), the CS mode is kept as the control mode (S114).

Hereinafter, a comparative embodiment of the regeneration operation of the filter <NUM> in the case where the control mode is not changed into the CS mode at the time when regeneration of the filter is required during the CD mode will be described with reference to <FIG>.

For example, it is assumed that the control mode is the CD mode. The regeneration operation from time t(<NUM>) to time t(<NUM>) in <FIG> is similar to that from time t(<NUM>) to time t(<NUM>) in <FIG>. Therefore, the detailed description will not be repeated. As described above, the regeneration request flag enters the on state at time t(<NUM>).

When the required output becomes lower than the start-up threshold Pr(<NUM>) of the engine <NUM> at time t(<NUM>), the engine <NUM> is stopped. In a period from time t(<NUM>) to time t(<NUM>), when the required output does not exceed the start-up threshold Pr(<NUM>) of the engine <NUM>, the engine <NUM> is kept stopped. In a period from time t(<NUM>) to time t(<NUM>), when the engine <NUM> is kept stopped, the temperature of the filter <NUM> decreases with a lapse of time.

When the SOC of the battery <NUM> becomes lower than the threshold SOC(<NUM>) at time t(<NUM>), the control mode is changed from the CD mode to the CS mode. When the control mode is changed from the CD mode to the CS mode, the start-up threshold of the engine <NUM> is changed from Pr(<NUM>) to Pr(<NUM>). Therefore, as described with reference to <FIG>, the engine <NUM> becomes easy to start up.

As a result, in a period from time t(<NUM>) to time t(<NUM>), a period from time t(<NUM>) to time t(<NUM>), a period from time t(<NUM>) to time t(<NUM>) and a period from time t(<NUM>) to time t(<NUM>), when the required output exceeds the start-up threshold Pr(<NUM>) of the engine <NUM>, the engine <NUM> is operated.

On the other hand, in a period from time t(<NUM>) to time t(<NUM>), a period from time t(<NUM>) to time t(<NUM>) and a period from time t(<NUM>) to time t(<NUM>), when the required output does not exceed the start-up threshold Pr(<NUM>) of the engine <NUM>, the engine <NUM> is stopped.

Therefore, from time t(<NUM>), the SOC is controlled so that the SOC at the timing of time t(<NUM>) at which the control mode has been changed into the CS mode is kept. As a result, the SOC of the battery <NUM> fluctuates with reference to the SOC at the timing of time t(<NUM>) at which the control mode has been changed into the CS mode.

When the engine <NUM> is operated, the temperature of the filter <NUM> increases by the heat of exhaust gas from the engine <NUM>. On the other hand, when the engine <NUM> is stopped, an increase in the temperature of the filter <NUM> is suppressed.

Therefore, after the timing at which the control mode has been changed from the CD mode to the CS mode at time t(<NUM>), the temperature of the filter <NUM> increases in a stepwise manner with a lapse of time, and exceeds the regeneratable temperature Tf(<NUM>) after time t(<NUM>). When the temperature of the filter <NUM> exceeds the regeneratable temperature Tf(<NUM>), the filter <NUM> can be regenerated. At this time, in the filter <NUM>, for example, PM is burned and removed by an oxygen component that is contained in gas flowing through the exhaust passage, and regeneration of the filter advances.

In this way, with the hybrid vehicle according to the present embodiment, as shown in <FIG>, when the control mode is the CD mode and when regeneration of the filter <NUM> is required, the control mode of the vehicle <NUM> is changed from the CD mode to the CS mode, so it is possible to extend the operating time of the engine <NUM> by increasing the number of opportunities for the engine <NUM> to operate as compared to the case where the control mode is not changed into the CS mode as shown in <FIG> (that is, the case where the CD mode is kept). Therefore, it is possible to reliably regenerate the filter <NUM> by early increasing the temperature of the filter <NUM> to the regeneratable temperature Tf(<NUM>) as compared to the case shown in <FIG>. Thus, it is possible to provide the hybrid vehicle and the control method for a hybrid vehicle, which reliably complete regeneration of the filter in the case where the control mode having a smaller number of opportunities for the engine to operate is selected.

When the control mode is changed from the CD mode to the CS mode as a result of the fact that it is determined that regeneration of the filter <NUM> is required, because the CS mode is kept until regeneration of the filter <NUM> completes, it is possible to keep a state where there is a large number of opportunities for the engine <NUM> to operate. Therefore, it is possible to reliably complete regeneration of the filter <NUM> by increasing the temperature of the filter to the regeneratable temperature.

When the control mode is changed from the CD mode to the CS mode as a result of the fact that it is determined that regeneration of the filter <NUM> is required, and when the SOC of the battery <NUM> is higher than or equal to the threshold SOC(<NUM>) after regeneration of the filter <NUM> has completed, by changing the control mode from the CS mode to the CD mode, it is possible to quickly eliminate a state where there is a large number of opportunities for the engine <NUM> to operate although the user recognizes that the CD mode is selected. When the SOC of the battery <NUM> is lower than the threshold SOC(<NUM>) after regeneration of the filter <NUM> has completed, it is possible to suppress a decrease in the SOC by keeping the CS mode. Therefore, when regeneration of the filter <NUM> has completed, it is possible to appropriately select the control mode in accordance with the SOC of the battery <NUM>. In the present embodiment, description is made on the assumption that, when the control mode is the CD mode and when regeneration of the filter <NUM> is required, the control mode is changed from the CD mode to the CS mode. Instead, as alternative embodiment to first embodiment, for example, when the control mode is the CD mode and when regeneration of the filter <NUM> is required, the engine <NUM> may be started up if the engine <NUM> is stopped and then the control mode may be changed from the CD mode to the CS mode.

In this case, for example, in a state where the engine <NUM> is stopped, the ECU <NUM> determines whether regeneration of the filter <NUM> is required. Specifically, when the travel history of the vehicle <NUM> coincides with a predetermined travel history (for example, when a total travel distance or total travel time of the vehicle <NUM> is longer than or equal to a threshold), the ECU <NUM> determines that regeneration of the filter <NUM> is required.

The ECU <NUM>, for example, assumes that the control mode is the CD mode, the engine is stopped and the regeneration request flag is in the off state, as shown in <FIG>. When the travel history of the vehicle <NUM> coincides with the predetermined travel history at time t(<NUM>), the ECU <NUM> sets the regeneration request flag to the on state. Thereafter, at time t(<NUM>), the ECU <NUM> starts up the engine <NUM> and changes the control mode from the CD mode to the CS mode. In this way as well, it is possible to early complete regeneration of the filter. The ECU <NUM> may start up the engine <NUM> and change the control mode from the CD mode to the CS mode a predetermined time after the regeneration request flag is set to the on state, or may start up the engine <NUM> when the required output exceeds the start-up threshold Pr(<NUM>), or may start up the engine <NUM> just after the regeneration request flag is set to the on state.

In the present embodiment, description is made on the assumption that the engine <NUM> is started up when the required vehicle power exceeds the start-up threshold and the engine <NUM> is stopped when the required vehicle power becomes lower than the stop threshold. Instead, for example, the engine <NUM> may be started up when the vehicle speed V instead of the required vehicle power exceeds a start-up threshold, and may be stopped when the vehicle speed V becomes lower than a stop threshold.

In this case, for example, during the CD mode, the engine <NUM> may be started up when the vehicle speed V exceeds a first start-up threshold Vr(<NUM>), and may be stopped when the vehicle speed V becomes lower than a first stop threshold Vs(<NUM>); whereas, during the CS mode, the engine <NUM> may be started up when the vehicle speed V exceeds a second start-up threshold Vr(<NUM>), and may be stopped when the vehicle speed V becomes lower than a second stop threshold Vs(<NUM>). In this case, the first start-up threshold Vr(<NUM>) is higher than the second start-up threshold Vr(<NUM>), and the first stop threshold Vs(<NUM>) is higher than the second stop threshold Vs(<NUM>). The first stop threshold Vs(<NUM>) is a predetermined value lower than or equal to the first start-up threshold Vr(<NUM>), and the second stop threshold Vs(<NUM>) is a predetermined value lower than or equal to the second start-up threshold Vr(<NUM>).

With this configuration, as shown in <FIG>, when the control mode is the CS mode, the vehicle speed V exceeds the start-up threshold Vr(<NUM>) at time t(<NUM>) and at time t(<NUM>), so the engine <NUM> is started up. When the control mode is the CS mode, the vehicle speed V becomes lower than the stop threshold Vs(<NUM>) at time t(<NUM>) and at time t(<NUM>), so the engine <NUM> is stopped.

On the other hand, when the control mode is the CD mode, the vehicle speed V exceeds the start-up threshold Vr(<NUM>) only at time t(<NUM>), so the engine <NUM> is started up. When the control mode is the CD mode, the vehicle speed V becomes lower than the stop threshold Vs(<NUM>) at time t(<NUM>), so the engine <NUM> is stopped.

In this way, when the control mode is the CS mode, the engine <NUM> starts up at a lower speed than that when the control mode is the CD mode, so it is possible to increase the number of opportunities for the engine <NUM> to operate. The first start-up threshold and second start-up threshold of the engine <NUM> are desirably set from the viewpoint of, for example, preventing excessive rotation of the first MG <NUM> due to a high vehicle speed V.

In the present embodiment, description is made on the assumption that, when the control mode is the CD mode and when regeneration of the filter <NUM> is required, the control mode is changed into the CS mode. Instead, for example, when the vehicle <NUM> is traveling in the CD mode and when the engine <NUM> starts up, the ECU <NUM> may set the regeneration request flag to the on state, and may change the control mode from the CD mode to the CS mode.

For example, as shown in <FIG>, it is assumed that the control mode is the CD mode. When the required output exceeds the start-up threshold Pr(<NUM>) of the engine <NUM> at time t(<NUM>), the ECU <NUM> starts up the engine <NUM>. The ECU <NUM> starts up the engine <NUM> and sets the regeneration request flag to the on state irrespective of the differential pressure between the upstream-side pressure and the downstream-side pressure (that is, irrespective of the amount of PM accumulated in the filter <NUM>). The ECU <NUM> sets the regeneration request flag to the on state, and changes the control mode from the CD mode to the CS mode. When the control mode is changed from the CD mode to the CS mode, the start-up threshold of the engine <NUM> is changed from Pr(<NUM>) to Pr(<NUM>). The operation after time t(<NUM>) is similar to the operation after time t(<NUM>) in <FIG>, so the detailed description thereof will not be repeated.

In the present embodiment, description is made on the assumption that the ECU <NUM> changes from any one of the two control modes, that is, the CD mode and the CS mode, to the other one. Instead, for example, the ECU <NUM> may change the control mode from any one of a plurality of control modes, including the CD mode, the CS mode and a control mode other than the CD mode or the CS mode, to another one.

In the present embodiment, description is made on the assumption that the CD mode and the CS mode are control modes having different start-up thresholds of the engine <NUM>. Instead, the CD mode and the CS mode may be set from the viewpoint of having relatively different numbers of opportunities for the engine <NUM> to operate between the two control modes. Hereinafter, a vehicle according to a second embodiment will be described. The vehicle <NUM> according to the present embodiment differs from the configuration of the vehicle <NUM> shown in <FIG> according to the above-described first embodiment in the operation of a controller <NUM>. The other components are the same as the components of the vehicle <NUM> shown in <FIG> according to the first embodiment. Like reference numerals denote the same components. The functions of the corresponding components are also the same. Therefore, the detailed description thereof will not be repeated.

In the above-described embodiment, description is made on the assumption that, when the control mode is the CD mode and when regeneration of the filter <NUM> is required, regeneration of the filter <NUM> is facilitated by increasing the temperature of the filter <NUM> to the regeneratable temperature Tf(<NUM>) or higher as a result of increasing the number of opportunities for the engine <NUM> to operate by changing the control mode from the CD mode to the CS mode. However, when an increase in the temperature of the filter <NUM> is suppressed depending on a traveling situation, a time may be required to regenerate the filter <NUM>.

Therefore, the present embodiment has such a characteristic that, when the control mode is the CD mode and when the filter <NUM> is regenerated, the ECU <NUM> changes the control mode from the CD mode to the CS mode and executes regeneration control over the filter <NUM>.

Regeneration control over the filter <NUM> increases the temperature of the filter <NUM> to a regeneratable temperature (activation temperature) Tf(<NUM>) or higher (hereinafter, also referred to as temperature increasing control), and burns and removes PM accumulated in the filter <NUM> by supplying air including oxygen to the filter <NUM>. PM accumulated in the filter <NUM> oxidizes by burning reaction with O<NUM> through regeneration control, and is removed from the filter <NUM>. Supply of air to the filter <NUM> may be, for example, carried out in a state where supply of fuel to the engine <NUM> is stopped and by setting the opening degree of a throttle valve (not shown) to a predetermined opening degree (for example, fully opening the throttle valve) and rotating the output shaft of the engine <NUM> by using the output torque of the first MG <NUM>.

<FIG> shows the functional block diagram of the ECU <NUM> mounted on the vehicle <NUM> according to the present embodiment. The functional block diagram of the ECU <NUM> shown in <FIG> differs from the functional block diagram of the ECU <NUM> shown in <FIG> in that a regeneration control unit <NUM> is included.

In the present embodiment, when the control mode is the CD mode and when regeneration of the filter <NUM> is required, the regeneration control unit <NUM> executes regeneration control when the engine <NUM> is operated. That is, when the regeneration request determination unit <NUM> determines that regeneration of the filter <NUM> is required, the regeneration control unit <NUM> executes regeneration control over the filter <NUM>.

Temperature increasing control over the filter <NUM> at the time when regeneration control is executed in the present embodiment, for example, includes output raising control and ignition retardation control. The regeneration control unit <NUM> executes at least one of output raising control or ignition retardation control as temperature increasing control at the time when regeneration control is executed.

Output raising control raises the output of the engine <NUM> so that exhaust gas temperature increases. Specifically, output raising control increases the temperature of the filter <NUM> to the regeneratable temperature Tf(<NUM>) by raising the output of the engine <NUM> over an ordinary value so that the exhaust gas temperature of the engine <NUM> increases. The output of the engine <NUM> is raised by adjusting at least one of the throttle opening degree, the fuel injection amount, or the ignition timing.

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

Part or all of redundant output resulting from raising the output of the engine <NUM> is converted to electric power generated by the first MG <NUM>, and is supplied to the battery <NUM> (the battery <NUM> is charged).

The output of the engine <NUM> 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 <NUM> 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.

The predetermined raising amount is, for example, set in consideration of the response of an increase in the temperature of the filter <NUM>, 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 <NUM> and an acceptable electric power based on the SOC, temperature, and the like, of the battery <NUM>.

Because the exhaust gas temperature is increased by raising the output of the engine <NUM> over the ordinary value as compared to that in the case where the output of the engine <NUM> is controlled in accordance with the ordinary value, it is possible to early increase the temperature of the filter <NUM> to the regeneratable temperature Tf(<NUM>). Therefore, it is possible to early remove PM accumulated in the filter <NUM>.

Ignition retardation control retards the ignition timing of the engine <NUM> so that the exhaust gas temperature increases. Specifically, ignition retardation control increases the temperature of the filter <NUM> to the regeneratable temperature Tf(<NUM>) by retarding the ignition timing of the engine <NUM> with respect to an ordinary value by a predetermined retardation amount so that the exhaust temperature of the engine <NUM> increases.

For example, when the output power of the engine <NUM> is determined, the ECU <NUM> obtains a base ignition timing on the basis of the determined output power. The ECU <NUM> 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 <NUM> corrects the base ignition timing with a correction amount corresponding to a predetermined amount in addition to the correction amount for the intake air temperature, the EGR amount, and the like, when regeneration control is executed.

The amount of decrease in the output of the engine <NUM>, 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 <NUM>, or the like. Therefore, the amount of discharge from the battery <NUM> increases.

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. Alternatively, the ignition timing 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.

The predetermined retardation amount is, for example, set in consideration of the response of an increase in the temperature of the filter <NUM>, 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 (the amount of PM accumulated) in the filter <NUM>, the state of the battery <NUM>, or the like.

Because the exhaust gas temperature is increased by retarding the ignition timing of the engine <NUM> 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 <NUM> to the regeneratable temperature Tf(<NUM>). Therefore, it is possible to early remove PM accumulated in the filter <NUM>.

As temperature increasing control, in addition to at least one of the above-described engine output raising control or ignition retardation control, heating control for heating the filter <NUM> with the use of a heat source (for example, a heating device, such as a heater) other than the engine may be executed.

In the present embodiment, during execution of regeneration control as well, the engine <NUM> intermittently operates or continuously operates on the basis of the state of the vehicle <NUM> (the state of the battery <NUM>, an accelerator operation amount, the speed of the vehicle, and the like). In this case, the regeneration control unit <NUM> executes temperature increasing control each time the engine <NUM> is operated (each time the engine <NUM> starts up).

For example, when regeneration control is executed together with start-up of the engine <NUM>, the regeneration control unit <NUM> may execute regeneration control until the temperature of the filter <NUM> reaches a predetermined temperature (the regeneratable temperature Tf(<NUM>) of the filter <NUM>), and may stop regeneration control when the temperature of the filter <NUM> reaches the predetermined temperature.

For example, when the temperature of the filter <NUM> significantly exceeds a predetermined temperature (for example, the temperature of the filter <NUM> is close to an upper limit temperature of the filter <NUM> or falls within an overheat region of the filter <NUM>) or when it is estimated that the temperature of the filter <NUM> significantly exceeds the predetermined temperature, the regeneration control unit <NUM> may stop the operation of the engine <NUM> or temperature increasing control until the temperature of the filter <NUM> falls within a predetermined range higher than or equal to the regeneratable temperature Tf(<NUM>) and lower than the upper limit temperature or until it is estimated that the temperature of the filter <NUM> falls within the predetermined range even during execution of regeneration control.

A control process that is executed by the ECU <NUM> mounted on the vehicle according to the present embodiment will be described with reference to <FIG>.

The process shown in the flowchart of <FIG> differs from the process shown in the flowchart of <FIG> in that the process of S206 is executed instead of S106 in <FIG>, and the process other than that is the same. Therefore, the detailed description thereof will not be repeated.

When it is determined that regeneration of the filter <NUM> is required (YES in S104), the ECU <NUM> changes the control mode from the CD mode to the CS mode and executes regeneration control in S206. The control details of regeneration control are as described above, so the detailed description thereof will not be repeated.

For example, when the regeneration request flag is in the on state, the ECU <NUM> may execute regeneration control. The ECU <NUM> may, for example, set a regeneration control execution flag to the on state together with execution of regeneration control. For example, when regeneration control is stopped as a result of stop of the engine <NUM> during execution of regeneration control or when regeneration control is stopped as a result of the fact that it is determined that regeneration of the filter <NUM> has completed, the ECU <NUM> may set the regeneration control execution flag to the off state.

The operation of the ECU <NUM> mounted on the vehicle <NUM> according to the present embodiment based on the above-described structure and flowchart will be described with reference to <FIG>.

<FIG> differs from <FIG> in that the operation of the ECU <NUM> before time t(<NUM>) is not shown, the degree of increase in temperature of the filter <NUM> is large because of regeneration control, the state of the regeneration control execution flag is indicated and the timing at which regeneration of the filter <NUM> completes (that is, the timing at which the control mode returns to the CD mode), and changes and operations other than the above are as described with reference to <FIG>. Therefore, in the following description, the operations and changes different from the details described with reference to <FIG> will be mainly described.

As shown in <FIG>, when the required output exceeds the start-up threshold Pr(<NUM>) of the engine <NUM> at time t(<NUM>), the engine <NUM> starts up. When the engine <NUM> starts up and when it is determined that regeneration of the filter <NUM> is required (YES in S <NUM>), the regeneration request flag enters the on state.

As a result of the fact that the regeneration request flag enters the on state, the control mode is changed from the CD mode to the CS mode, and regeneration control is executed (S206). Therefore, the regeneration control execution flag enters the on state.

In a period from time t(<NUM>) to time t(<NUM>), each time the engine is operated, regeneration control is executed and the regeneration control execution flag enters the on state; whereas each time the engine <NUM> is stopped, regeneration control is stopped and the regeneration control execution flag enters the off state.

When regeneration control is executed, it is possible to increase the temperature of the filter <NUM> to the regeneratable temperature Tf(<NUM>) or higher earlier than when regeneration control is not executed by temperature increasing control. At this time, in the filter <NUM>, PM is burned and removed by an oxygen component contained in gas flowing through the exhaust passage <NUM>.

After the control mode has been changed into the CS mode, when the engine <NUM> is stopped (supply of fuel is stopped), the output shaft of the engine <NUM> is rotated by using the output torque of the first MG <NUM>. Thus, the operation of supplying air (O<NUM>) to the filter <NUM> may be executed. With this configuration, it is possible to further facilitate regeneration of the filter <NUM>.

When it is determined that regeneration of the filter <NUM> has completed (YES in S108) at time t(<NUM>) that is the timing earlier than time t(<NUM>) at which it is determined that regeneration of the filter <NUM> has completed in the case shown in <FIG>, because the SOC of the battery <NUM> is higher than or equal to the threshold SOC(<NUM>) (YES in S110), the regeneration request flag and the regeneration control execution flag enter the off state, and the control mode is changed from the CS mode to the CD mode (S112).

In this way, with the hybrid vehicle according to the present embodiment, in addition to the operation and advantageous effects described in the above-described embodiment, it is possible to early increase the temperature of the filter <NUM> by changing the control mode from the CD mode to the CS mode and executing regeneration control. Therefore, it is possible to early start regeneration of the filter <NUM>, so it is possible to early and reliably complete regeneration of the filter <NUM>. The invention is also applicable to a diesel engine; however, it is further effective to apply the invention to a gasoline engine as described below. When it is assumed that the engine <NUM> is a diesel engine, it is conceivable that the process shown in the flowchart of <FIG> is executed. Hereinafter, the process shown in the flowchart of <FIG> will be described.

The process shown in the flowchart of <FIG> differs from the process shown in the flowchart of <FIG> in that the process of S306 is executed instead of S106 in <FIG>, and the other processes are the same. Therefore, the detailed description thereof will not be repeated.

When it is determined that regeneration of the filter is required (YES in S104), the ECU <NUM> executes regeneration control over the filter <NUM> (DPF) in S306. When regeneration control is executed over the DPF, and when the engine <NUM> is stopped, the engine <NUM> is forcibly started up, and the operation of the engine <NUM> is continued until regeneration of the filter <NUM> completes. For example, output raising control or heating control is one example of temperature increasing control in regeneration control over the DPF.

The engine <NUM> that is a diesel engine is larger in the amount of PM generated and lower in exhaust gas temperature than a gasoline engine having a comparable output. Particularly, during the CD mode, when the engine starts up in a state where warm-up has not been completed, the amount of PM generated increases.

Therefore, when regeneration of the filter <NUM> is required, it is desirable that a temporary stop of the engine according to the control mode be suppressed in order to early complete regeneration of the filter <NUM> and the operation of the engine <NUM> be continued until regeneration of the filter <NUM> completes as shown in the flowchart of <FIG>.

On the other hand, a gasoline engine to which the invention is applied is smaller in the amount of PM generated and higher in exhaust gas temperature than a diesel engine having a comparable output. Therefore, even when it is determined that regeneration of the filter <NUM> is required, a temporary stop (intermittent operation) of the engine <NUM> according to the control mode is permitted. Therefore, it is more effective that the invention that changes the control mode from the CD mode to the CS mode having a larger number of opportunities for the engine <NUM> to operate than the CD mode in the case where regeneration of the filter <NUM> is required is applied to a gasoline engine.

In the present embodiments, as described with reference to <FIG>, the hybrid vehicle on which the gasoline engine and the two motor generators, including the first MG <NUM> and the second MG <NUM>, are mounted is described as an example. However, particularly, the number of motor generators mounted on the hybrid vehicle is not limited to two, and may be one or three or more. The hybrid vehicle may be a series hybrid vehicle or may be a parallel hybrid vehicle.

In the present embodiments, as illustrated in <FIG>, the layout of the exhaust passage in which the catalyst <NUM> and the filter <NUM> 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 <NUM> and the filter <NUM> is provided in two or more numbers may be employed.

For example, the layout of the exhaust passage may be the layout shown in <FIG>. That is, as shown in <FIG>, when the engine <NUM> 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.

In this case, as shown in <FIG>, 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.

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.

In the thus configured vehicle, the ECU <NUM> 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 or 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.

The ECU <NUM>, 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 or the second differential pressure is larger than a threshold. The ECU <NUM>, 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 <NUM>, 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.

The ECU <NUM> may execute regeneration control over at least any one of the first filter 84a or 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.

The ECU <NUM>, 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.

Alternatively, the layout of the exhaust passage may be the layout shown in <FIG>. That is, as in the case of the layout of the exhaust passage shown in <FIG>, 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 <NUM> 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 <NUM> 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.

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

Alternatively, the layout of the exhaust passage may be the layout shown in <FIG>. That is, as in the case of the layout of the exhaust passage shown in <FIG>, 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 <NUM> 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.

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>, so the detailed description thereof will not be repeated.

Claim 1:
A hybrid vehicle comprising:
an engine (<NUM>) including an exhaust passage;
a rotary electric machine (<NUM>) that is a driving source of the hybrid vehicle;
a filter (<NUM>) configured to trap particulate matter flowing through the exhaust passage; and
an electronic control unit (<NUM>) configured to
control the hybrid vehicle in any one of a plurality of control modes, the plurality of control modes including a charge depleting mode and a charge sustaining mode, the number of opportunities for the engine (<NUM>) to operate when the control mode is the charge sustaining mode being larger than the number of opportunities for the engine (<NUM>) to operate when the control mode is the charge depleting mode, and
control the hybrid vehicle in the charge sustaining mode when the filter (<NUM>) is regenerated;
characterized in that the electronic control unit is further configured so that, when the electronic control unit is already controlling the hybrid vehicle in the charge sustaining mode when the regeneration of the filter is required, the charge sustaining mode is kept during regeneration of the filter until regeneration of the filter is complete.