US20070204594A1

US20070204594A1 - Exhaust purification system for hybrid vehicle

Info

Publication number: US20070204594A1
Application number: US11/711,438
Authority: US
Inventors: Hiroshi Ishii
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2006-03-02
Filing date: 2007-02-27
Publication date: 2007-09-06

Abstract

An exhaust purification system for a hybrid vehicle with an internal combustion engine and an electric motor capable of being driven by the engine includes a battery, an exhaust gas passage, an exhaust purification device and at least one controller. The battery is connected to the electric motor and selectively charged with electric power generated by the electric motor. The exhaust gas passage is connected to the internal combustion engine and the exhaust purification device is disposed in the exhaust gas passage. The at least one controller selectively performs regeneration control of the exhaust purification device and controls the engine and the electric motor to ensure that the battery does not become overcharged.

Description

CROSS-REFERENCES TO RELATED APPLICATION

This application claims priority from Japanese Patent Application Serial Nos. tokugan2006-055628 filed Mar. 2, 2006, and tokugan2006-057522 filed Mar. 3, 2006, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

An exhaust purification system is disclosed related to hybrid vehicles including, as vehicle drive sources, an internal combustion engine and an electric motor serving as a power generator concurrently. More specifically, the disclosed system relates to regeneration techniques for exhaust purification devices such as particulate matter (PM) collecting filters and NOx absorber catalysts for use with an internal combustion engine.

BACKGROUND

Japanese Patent Application Laid-Open No. 2004-278465 (Patent Document 1, hereafter) discloses a hybrid vehicle. In the hybrid vehicle deposits (e.g., sulfur) accumulated in an exhaust purification device, such as one utilizing a NOx absorber catalyst, provided in an exhaust passageway of an internal combustion engine is removed by combustion, thereby to implement regeneration (poison removal) of the exhaust purification device. During regeneration power output of the engine is increased, the engine undertaking a high load power generation operation. The exhaust temperature is increased by operating the engine with a high load. By raising exhaust temperature, the engine power generation quickly raises the temperature of the exhaust purification device to a point necessary for regeneration. At the same time a separate electric motor is activated using at least some of the additional power output of the engine. In such an operation, the amount of power generated (or “power generation amount”, herein below) is stored into a battery, so that surplus energy is usable later on, thereby to restrain fuel consumption from being aggravated by the regeneration.
However, the technique described in Patent Document 1 has problems. For example, when the amount of charge (or “charge amount”, herein below) in the battery is increased to an overcharged state, the battery may undesirably deteriorate. As such, depending on the case, the high load power generation operation cannot be continued further from that state. In turn, temperature elevation cannot be maintained. Thus, regeneration could be hindered.
In view of these circumstances, it is desirable to enable a high load power generation operation without causing deterioration of a battery affected by the operation, thereby improving regeneration efficiency.

SUMMARY

An exhaust purification system for a hybrid vehicle with an internal combustion engine and an electric motor capable of being driven by the engine includes a battery, an exhaust gas passage, an exhaust purification device and at least one controller. The battery is connected to the electric motor and selectively charged with electric power generated by the electric motor. The exhaust gas passage is connected to the internal combustion engine and the exhaust purification device is disposed in the exhaust gas passage. The at least one controller selectively performs regeneration control of the exhaust purification device and controls the engine and the electric motor to ensure that the battery does not become overcharged. This enables the regeneration control to be implemented without causing deterioration of the battery due to overcharging. Consequently, the regeneration efficiency can be improved.

BRIEF DESCRIPTION OF DRAWINGS

While the claims are not limited to the illustrated embodiments, an appreciation of various aspects of the system is best gained through a discussion of various examples thereof. Referring now to the drawings, illustrative embodiments are shown in detail. Although the drawings represent the embodiments, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain an innovative aspect of an embodiment. Further, the embodiments described herein are not intended to be exhaustive or otherwise limiting or restricting to the precise form and configuration shown in the drawings and disclosed in the following detailed description. Exemplary embodiments of the present invention are described in detail by referring to the drawings as follows.

FIG. 1 is a system diagram of a hybrid vehicle, which shows a first exemplary embodiment of the system;

FIG. 2 is a control block diagram of the hybrid vehicle of the first embodiment;

FIG. 3 is a diagram showing a power output distribution table in a normal mode (M=0);

FIG. 4 is a diagram showing an engine operation point table;

FIG. 5 is a diagram showing a motor operation point table;

FIG. 6 is a diagram showing a power output distribution table in a mode (M=1) during DPF regeneration;

FIG. 7 is a diagram showing a power output distribution table in a mode (M=2) before DPF regeneration;

FIG. 8 is a diagram showing an example of a PM deposition amount-SOC target value table;

FIG. 9 is a diagram showing the relation between a deviation amount from a target value of a charge amount and a power output boundary value;

FIG. 10 is a diagram showing a power output distribution table in a DPF regeneration initiation mode (M=3);

FIG. 11 is a flow chart showing a control flow;

FIG. 12 is a timing chart showing a control flow;

FIG. 13 is a diagram showing another example of the PM deposition amount-SOC get value table;

FIG. 14 is a diagram showing another example of the PM deposition amount-SOC get value table;

FIG. 15 is a system diagram of a series hybrid vehicle;

FIG. 16 is a diagram showing a motor operation point table in the series hybrid vehicle;

FIG. 17 is a diagram showing a sulfur deposition amount-SOC target value table;

FIG. 18 is a control block diagram of a hybrid vehicle according to another exemplary embodiment of the system;

FIG. 19 is a diagram showing a power output distribution table in a normal mode (M=4);

FIG. 20 is a diagram showing an engine operation point table;

FIG. 21 is a diagram showing a motor operation point table;

FIG. 22 is a diagram showing a power output distribution table in a power generation amount increase mode (M=5);

FIG. 23 is a diagram showing a power output distribution table in a power generation amount restriction mode (M=6, 7);

FIG. 24 is a diagram showing an engine operation point table in the power generation amount restriction mode (M=6, 7);

FIG. 25 is a characteristic diagram of an mount of retardation of fuel injection timing in the power generation amount restriction mode (M=6, 7);

FIG. 26 is a diagram showing a current compensation characteristic in a current compensation mode (M=7);

FIG. 27 is a diagram showing the relation between a DPF temperature and an engine speed in a motor driven travel mode (M=8);

FIG. 28 is a flow chart showing a control flow in the exemplary embodiment of FIG. 18;

FIG. 29 is a timing chart (1) showing the control flow in the exemplary embodiment of FIG. 18; and

FIG. 30 is a timing chart (2) showing the control flow in the exemplary embodiment of FIG. 18.

DETAILED DESCRIPTION

FIG. 1 is a system diagram of a hybrid vehicle, which shows a first exemplary embodiment.
The hybrid vehicle includes, as vehicle drive sources, an internal combustion engine I (or, simply “engine,” here below) and an electric motor 2 (alternately called “motor generator”) 2 concurrently serving as a power generator. The motor 2 is electrically connected to a battery 4 through an inverter 3.
Output shafts of the engine 1 and the motor 2, respectively, are coupled to an input shaft of a final reduction gear device 7 through transmissions (belt continuous variable transmissions 5 e and 5 m (each of which herein below will be referred to as “CVT”) and clutches 6 e and 6 m. Driving wheels are fitted onto output shafts 8 (axle) of the final reduction gear device 7.
The engine 1 is, for example, a diesel engine, and is capable of generating an arbitrary torque by controlling the amount of fuel injection or the like.
The motor 2 can generate an arbitrary torque by consuming the power of the battery 4.
The engine 1 and the motor 2 are each independently or both cooperatively capable of driving the vehicle through the clutches 6 e and 6 m, respectively.
During deceleration of the vehicle, engine braking by the engine 1 can be used. Moreover, regenerative braking is possible whereby the motor 2 functions as a power generator to recapture at least a portion of the kinetic energy that would otherwise be lost to heat when braking and making use of that power by charging the battery 4 through the inverter 3. In addition, during driving by the engine 1, the motor 2 is driven through the clutch 6 m and the transmission 5 m. Thus, the vehicle and the motor 2 are driven by the engine 1, permitting the generation of power within motor 2 that is also chargeable to the battery 4 through the inverter 3.
As exemplary exhaust purification devices, an oxidation catalyst 9, NOx absorber catalyst 10, and diesel particulate filter (DPF) 11 are provided in an exhaust passageway 12 of the diesel engine 1.
The oxidation catalyst 9 performs oxidation treatment of exhaust and evaporative pollutant of hydrogen and carbon atoms (HC) and Carbon Monoxide (CO) resulting from unburned fuel contained in the exhaust gas.
The NOx absorber catalyst 10 absorbs oxides of nitrogen (NOx) contained in the exhaust gas, and is capable of performing absorption purification of NOx in a rich atmosphere.
The DPF 11 collects a particulate matter (PM) contained in the exhaust gas, and contains a catalyst that promotes combustion of PM during regeneration.
The DPF 11 is subject to plugging through the collection of increasing deposits of PM, thereby introducing deterioration of operability due to an increased exhaust resistance. When the accumulated level or amount of PM deposits (or, “PM deposit amount,” herein below) is larger than a predetermined value, regeneration is desired. Regeneration timing is the event timing for addressing the PM deposit amount. When regeneration takes place, a temperature rise of the DPF 11 is carried out resulting in combustion of the PM deposit amounts. Thereby, combustion removal of the PM deposits on the DPF 11 takes place, reducing the PM deposit amount, and the DPF 11 is regenerated.
When used for a long time, the NOx absorber catalyst 10 is poisoned by sulfur (S), thereby being deteriorated in NOx adsorption efficiency. For this reason, the amount or level of amount of sulfur deposits (amount of sulfur poisoning) is estimated. When the estimated amount of sulfur becomes larger than a predetermined value, regeneration is necessary as a poison removal process. As with DPF 11, when regeneration takes place, a temperature rise of the NOx absorber catalyst is carried out, resulting in combustion of the sulfur deposits. Thereby, combustion removal of the sulfur deposits on the NOx absorber catalyst takes place, reducing the amount of sulfur, and the NOx absorber catalyst is regenerated (poison-removed).
In the event of regeneration of an exhaust purification device (DPF 11, NOx absorber catalyst 10), the power output of the engine 1 is increased, and the motor 2 is driven by using an excess power output with respect to a requested power output, thereby to generate power. As a consequence, the high load power generation operation of the diesel engine 1 is carried out to cause temperature rise of the exhaust temperature, and the amount of generated power is charged to the battery 4.
A controller 100 is connected to the engine 1 and the motor 2. While a single controller 100 is shown, one or more controllers working together is also possible. The controller 100 performs the above-described operations of control, such as engine control, motor control, and control for cooperative control between the engine and motor, such as distribution of the engine power output and motor power output with respect to a requested total power output.
In addition, in the present exemplary embodiment, the internal combustion engine 1 and the electric motor 2 undergo cooperative control before the regeneration control. The cooperative control is so performed such that the charge amount in the battery 4 is reduced corresponding to the amount of deposits (PM, sulfur) in the exhaust purification devices. As a result, the battery is prevented from being overcharged in the event of the regeneration control. An example of cooperative control may be illustrated using the regeneration of the DPF.
FIG. 2 is a control block diagram of the hybrid vehicle. As illustrated in FIG. 2, the vehicle includes an operation state detecting mechanism B1 that detects the operation state of the vehicle; an operation point determining mechanism B2 that determines respective operation points of the engine and motor in accordance with the detection results; an engine control mechanism B3, which controls the engine 1 in accordance with a determined engine operation point; and a motor control mechanism B4 that controls the motor in accordance with a determined motor operation point.
More specifically, the operation point determining mechanism B2 is configured to alter an operation point in accordance with an operation mode specified by an operation mode altering mechanism B5 in the relation with the regeneration control of the DPF 11. The operation mode altering mechanism B5 contains information input from a DPF deposit amount estimating mechanism B6, a DPF temperature detecting mechanism B7, and a charge amount detecting mechanism B8.
The DPF deposit amount estimating mechanism B6 uses, for example, a differential pressure sensor that detects a differential pressure between an upstream exhaust pressure in the DPF 11 and a downstream exhaust pressure therein, thereby to estimate a PM deposit amount, C, from the detected differential pressure and an engine operation state (volume of exhaust flow or engine speed and load defining the volume of exhaust flow). Alternatively, the PM deposit amount, C, can be estimated using mechanism B6 in such a manner that the amounts of collected PM per unit time are estimated from the engine operation state and the results are integrated.
The DPF temperature detecting mechanism B7 detects a DPF temperature T by using a sensor that detects, for example, the temperature of a DPF carrier or exhaust temperatures of a downstream side and/or upstream side of the DPF 11.
The charge amount detecting mechanism B8 detects a battery charge amount, SOC, through the integration of charge and discharge currents by using a current sensor that detects charge and discharge currents of the battery. Normally, the charge amount, SOC, is obtained as a ratio (%) to the full amount of charge.
Operation modes to be specified by the operation mode altering mechanism B5 correspondingly to, for example, the state of the DPF 11 will now be described here below.
The operation modes are a normal mode (M=0), a DPF regeneration mode (M=1) during DPF generation, a motor power output increase mode (charge amount reduction mode; M=2) before DPF generation, and an engine power output increase mode (power generation amount increase mode; M=3) in a DPF generation initiation event. The respective modes will be described here below.
The normal mode (M=0) is a normal operation mode. In this mode, a requested total power output Pt0 requested for the vehicle is calculated in accordance with operation state information received from the operation state detecting mechanism B1. In addition, an engine power output Pe0 and a motor power output Pm0 are determined from the requested total power output Pt0 by using a hybrid power output (engine/motor power output) distribution table of FIG. 3, which shows a distribution of hybrid power output with respect to the total power output. Then, the determined power outputs Pe0 and Pm0 are supplied for commands to the engine control mechanism B3 and the motor control mechanism B4. FIG. 3 also illustrates a total power output lower limit value, Pmc, which is discussed in greater below with respect to FIG. 7.
In the engine control mechanism B3, an operation point is determined by using an engine operation point table as illustrated in FIG. 4 in accordance with the determined motor power output Pm0. The operation point table is created by setting combinations of torques (Te0, Te1, . . . ) and rotational speeds (Ne0, Ne1, . . . ), which optimize fuel consumption, with respect to the respective engine power output values (Pe0, Pe1, . . . ).
In the motor control mechanism B4, an operation point is determined by using a motor operation point table as illustrated in FIG. 5 in accordance with the determined engine power output Pe0. The operation point table is created by setting combinations of torques (Tm0, Tm1, . . . ) and rotational speeds (Nm0, Nm1, . . . ), which optimize fuel consumption, with respect to the respective motor power output values (Pm0, Pm1, . . . ).
The DPF regeneration mode (M=1) is an operation mode during DPF regeneration, and is used to increase the amount of power generated by slightly increasing the engine power output so as not to reduce the exhaust temperature. As such, an engine power output Pe0 and a motor power output Pm0 are determined from a requested total power output Pt0 by using a hybrid power output distribution table as illustrated in FIG. 6. Then the determined power outputs Pe0 and Pm0 are supplied for commands to the engine control mechanism B3 and the motor control mechanism B4. In the hybrid power output distribution table of FIG. 6, particularly the engine power output Pe0 is maintained at a value greater than or equal to a specified power output P0, whereby, in a low power output zone, an excess amount (Pe0−Pt0) of the engine power output Pe0 with respect to the requested total power output Pt0 is set to be an amount of power generated in the motor.
The motor power output increase mode (M=2) is an operation mode before DPF generation (preparatory stage), in which a charge amount SOC is progressively reduced by increasing the motor power output ratio. As such, an engine power output Pe0 and a motor power output Pm0 are determined from a requested total power output Pt0 by using a hybrid power output distribution table of FIG. 7. Then the determined power outputs Pe0 and Pm0 are supplied for commands to the engine control mechanism B3 and the motor control mechanism B4. In the hybrid power output distribution table of FIG. 7, a requested total power output lower limit value Pmc for starting the engine power output is increased, and concurrently, an upper limit value Pec of the engine power output is reduced, thereby to reduce the engine power output ratio to the requested total power output.
Further, in the motor power output increase mode (M=2), by referencing table of FIG. 8, a target value Et of the charge amount SOC is set corresponding to the PM deposit amount C. In the event that the PM deposit amount C is a predetermined value Cp or more, the target value Et of the charge amount SOC is reduced to be smaller as the PM deposit amount C becomes larger. In addition, where the PM deposit amount C is close to a predetermined value for regeneration timing determination (regeneration-request occurring deposit amount) Ce, it is set as Et=Es (fixed value).
Then, as the target value Et of the charge amount SOC becomes smaller, the engine power output ratio to the requested total power output is reduced to be smaller, and the motor power output ratio is increased.
More specifically, as shown in FIG. 9, as a deviation amount (ΔE=SOC−Et), i.e., the amount of deviation of an actual value SOC of the charge amount with respect to the target value Et, is larger, the requested total power output lower limit value Pmc for raising the engine power output in the hybrid power output distribution table of FIG. 7 is compensated to be increased, and the upper limit value Pec of the engine power output in the same table is compensated to be reduced. That is, in the motor power output increase mode (M=2), with respect to the normal mode (M=0), the requested total power output lower limit value Pmc for raising the engine power output is compensated to be increased, and the upper limit value Pec of the engine power output is decrementally compensated to be reduced. However, instead of the decremental compensation of the upper limit value Pec of the engine power output, the ratio of the engine power output Pe to either the requested total power output Pt0 or motor power output Pm can be reduced. The compensation in this case is carried out when the actual value SOC of the charge amount is larger than the target value Et (i.e., when ≢E>0). The amount of compensation is set to 0 when the actual value SOC of the charge amount is smaller than the target value Et (i.e., when ΔE<0). That is, the table of FIG. 3 is set with Pmc and Pec set as defaults or initial values.
The engine power output increase mode (M=3) is an operation mode for use in the DPF regeneration initiation event (when a DPF regeneration request is present and the DPF temperature is low). In this mode, the engine power output is largely increased to thereby largely increase the amount of power generated. The mode is thus set for the reason that the exhaust temperature is raised by the high load operation of the engine to thereby promote the elevation of the DPF temperature. As such, an engine power output Pe0 and a motor power output Pm0 are determined from a requested total power output Pt0 by using a hybrid power output distribution table as illustrated in FIG. 10. Then the determined power outputs Pe0 and Pm0 are supplied for commands to the engine control mechanism B3 and the motor control mechanism B4. In the hybrid power output distribution table of FIG. 10, the engine power output Pe0 is set to a large fixed value in the entire zone. Thereby, in a low/intermediate power output zone, an excess amount (Pe0−Pt0) of the engine power output Pe0 with respect to the requested total power output Pt0 is set to be an amount of power generated in the motor.
A flow of control will now be described with reference to a flow chart as illustrated in FIG. 11.
In step A1, a determination is made as to the presence or absence of a DPF regeneration request. More specifically, the process reads a PM deposit amount (estimated value) C in the DPF 11, which is calculated in a different routine. Then, the process determines whether or not the read value is greater than or equal to a predetermined value Ce for regeneration timing determination. Alternatively, as shown in FIG. 11, C can simply be required to be greater than Ce.
If a DPF regeneration request is absent (C<Ce) as a result of the determination in step A1, the process proceeds to step A2. In step A2, it is determined whether or not preparation for DPF regeneration is necessary, that is, whether or not the state is prior to regeneration control. More specifically, it is determined whether or not the PM deposit amount (estimated value) C is greater than or equal to the predetermined value Cp for regeneration preparation timing determination. Cp is smaller than Ce (Cp<Ce).
If the DF regeneration preparation is not necessary (if C<Cp) as a result of the determination in step A2, the process proceeds to step A3. In step A3, the mode is set to and maintained in the normal mode (M=0).
Alternately, if the DPF regeneration preparation is necessary (if C>Cp) as a result of the determination in step A2, the process proceeds to step A6. In step A6, it is determined whether or not the charge amount SOC in the battery 4, which is calculated by the different routine, is greater than or equal to the predetermined value Es. Alternatively, as shown in FIG. 11, SOC can simply be required to be greater than Es. The predetermined value Es corresponds to a target charge amount at DPF regeneration timing (DPF-regeneration-request deposit amount Ce) (see FIG. 10); that is, after the charge amount is reduced to the level of the value, the value is sufficiently achievable for charging.
If SOC>Es as a result of the determination in step A6, the process proceeds to step A7. In step A7, the mode is set to the motor power output increase mode (M=2), which is the charge amount reduction mode before regeneration. Thereby, the charge amount SOC is reduced to Es.
Alternately, if SOC<Es as a result of the determination in step A6, the process proceeds to step A9, in which the mode is set to the engine power output increase mode (M=3), which is the power generation amount increase mode. Thereby, conversely to the above case, the charge amount is prevented from being over-reduced, and the charge amount SOC is maintained at Es.
Thereafter, if a DPF regeneration request is present (i.e., if C>Ce) as a result of the determination in step A1, the process proceeds to step A4, in which it is determined whether or not the mode is the DPF regeneration mode (M=1). If the mode is not the mode (M=1), the process proceeds to step A5, in which it is determined whether or not the mode is the motor power output increase mode (M=2).
If the mode is the motor power output increase mode (M=2) as a result of the determination in step A5, the process proceeds to step A6. If, in step A6, SOC>Es, the motor power output increase mode (M=2), which is the charge amount reduction mode, is maintained in step A7.
Alternately, if SOC<Es as a result of the determination in step A6, the process proceeds to step A9. In step A9, the mode is shifted to the engine power output increase mode (M=3), which is the power generation amount increase mode in the regeneration initiation event.
After the mode has been set to the mode (M=3), the mode (M=2) is not detected in the determination in step A5, so that the process proceeds from the step A5 to step A8. In step A8, a DPF temperature T calculated by the different routine is read, and unless the DPF temperature T is a predetermined value Th or more, the process proceeds to step A9, in which the engine power output increase mode (M=3), which is the power generation amount increase mode in the regeneration initiation event is maintained. Thereby, the high load power generation operation of the engine 1 is performed, thereby to raise the exhaust temperature for DPF regeneration.
Thereafter, if T (DPF temperature)>Th as a result of the determination in step A8, the process proceeds from step A8 to step A10, in which the mode is set to the DPF regeneration mode (M=1), which is the mode during regeneration. The predetermined value Tb represents a DPF-regeneration target temperature at which PM deposited in the DPF 11 is combustible.
Then, the mode is determined in step A4 to be the DPF regeneration mode (M=1) until termination of DPF regeneration. Therefore, the process proceeds from step A4 to step A10, in which the DPF regeneration mode (M=1) is maintained.
FIG. 12 illustrates a timing chart for flow control. In the event that the PM deposit amount C (estimated value) in the DPF 11 exceeds the predetermined value Cp at time t0, the timing of the event is determined to be pre-generation timing. In this case, the mode is shifted from the normal mode (M=0) to the motor power output increase mode (M=2), which is the charge amount reduction mode before regeneration. Thereby, the motor power output is increased to thereby reduce the charge amount SOC before regeneration. In this event, the target charge amount Es is reduced corresponding to the PM deposit amount C or is reduced to be smaller as the PM deposit amount C is increased to be larger, thereby to progressively reduce the charge amount SOC.
Thereafter, in the event that the PM deposit amount C in the DPF 11 exceeds the predetermined value Ce at time t1, the timing of the event is determined to be the regeneration timing. However, during the period of time in which the battery charge amount SOC reduces to the final target value Es, the motor power output increase mode (M=2), which is the charge amount reduction mode, is maintained.
Then, in the event that the charge amount SOC has reduced to the final target value Et at time t2, the mode is shifted to the engine power output increase mode (M=3), which is the power generation amount increase mode in the regeneration initiation event. Thereby, the engine power output is increased and the motor 2 is driven by an excess power output of the engine 1 to thereby generate the power. Then, with the high load power generation operation of the engine 1, the exhaust temperature is raised, and the DPF temperature T is raised. While the amount of power generated in this event is used to charge the battery 4, the amount of charge stored in the battery 4 is preliminarily reduced, so that the battery 4 is prevented from being overcharged. An upper limiter for the charge amount SOC can be set higher than usual.
Subsequently, in the event that, at time t3, the DPF temperature T has reached the target value Tb at which regeneration is possible, the mode is shifted to the DPF regeneration mode (M=1), in which operation at a power level not reducing the DPF temperature is carried out.
As described above, according to the present embodiment, control is carried out in the following manner. In the event of regeneration of the DPF, the power output of the engine is increased to thereby drive the motor, whereby the high load power generation operation is carried out to increase the exhaust temperature. Before the regeneration, the power output of the motor is increased, thereby to reduce the amount of charge stored in the battery. Thereby, in the event of regeneration, even more sufficiently high load power generation operation can be implemented. Consequently, the exhaust temperature can be quickly increased, and the battery can be prevented from being deteriorated due to overcharge.
Further, according to the exemplary embodiment, the amount of charge in the battery is varied corresponding to the amount of deposits of PM in the DPF. Consequently, the amount of charge in the battery can be adjusted in preparation for a request for the regeneration of the DPF.
Control is performed such that, when the PM deposit amount in the DPF is the predetermined value or more, the charge amount is reduced to be smaller as the deposit amount is larger. Thereby, the charge amount is progressively reduced before the initiation of DPF regeneration, consequently making it possible to implement a long-term high load power generation operation in the regeneration initiation event.
Further, according to the present exemplary embodiment, the determination of whether or not a mode underway is anterior to regeneration control is made in accordance with the estimate value of the amount of deposits. Thereby, the time before the regeneration can be quantitatively determined, so that the charge amount reduction control can be performed at appropriate timing before occurrence of a regeneration request.
Further, according to the present illustrated embodiment, the reduction control for the charge amount SOC is carried out in the following manner. In the power output distribution control for the engine and the motor with respect to the requested total power output, at least one of the following processes of control is performed. They are the incremental compensation for the requested total power output lower limit value Pmc for raising the engine power output, decremental compensation for the upper limit value Pec of the engine power output, and decremental compensation for the engine power output ratio with respect to the requested total power output. With the process of control, the cooperative control is carried out to cause variations of the power output distributions of the engine and the motor, thereby to direct the power balance of the motor to the negative trend, whereby the charge amount SOC can be securely reduced. 100
According to the present embodiment, the amount of the compensation described above amount is varied corresponding to the deviation amount (ΔE=SOC−Et), i.e., the amount of deviation of an actual value SOC of the charge amount with respect to the target value Et set corresponding to the PM deposit amount. Thereby, the power balance of the motor is further directed in the negative trend as the deviation amount ΔE is larger, thereby to enable it to improve followability to the target value Et.
Further, according to the present embodiment, the compensation described above is performed in the event that the actual value SOC of the charge amount is larger than the target value Et, but is not performed in the event that the actual value SOC is smaller than the target value Et. As a consequence, even in the case of SOC reduced to a level appropriate for “temperature-rise power generation”, SOC can be maintained to be that reduced in an early stage when the influence thereof is considered less on the operability. That is, SOC is not forcedly increased, thereby to enable the operation to be performed as in an even more appropriately selected pattern.
In the present embodiment described above, as shown in FIG. 8, the target value Et of the charge amount SOC corresponding to the PM deposit amount C is set as a single value. As an alternative case, however, the target value Et can be set as a target range defined by an upper limit value and a lower limit value.
More specifically, for example, as shown in FIG. 13, the target value can be set as a target range defined by a SOC upper limit value and a SOC lower limit value. In this case, when the PM deposit amount C is the predetermined value or more, the SOC upper limit value is reduced to be smaller as the PM deposit amount C is larger.
Still alternatively, the target value can be set as a target range defined by a SOC upper limit value and a SOC lower limit value, as shown in FIG. 14. After the PM deposit amount C has reached a predetermined value C1 larger than the regeneration-request occurring deposit amount Ce, the SOC upper limit value is reduced to be smaller as the PM deposit amount is larger. More specifically, depending on the case, there occurs an instance in which the charge amount SOC naturally reduces. Therefore, such an instance is awaited, and SOC is forcedly reduced at the level larger than the predetermined value C1 in the event that SOC does not reduce. In this case, the timing of the regeneration initiation is set to an instance at which the DPF regeneration request is present and SOC has reached the regeneration initiation SOC.
In the event that the target value of the charge amount is set as a target range such as described above, the amount of compensation of the respective power output boundary value Pmc, Pec of FIG. 9 is increased to be greater as the actual SOC, i.e., an upper limit value (ΔE=actual SOC−SOC), is greater than the SOC upper limit value in the target range. That is, as the followability of the actual SOC deviates more greatly with respect to the SOC upper limit value, the power balance of the motor is further directed in a negative trend, thereby to improve the SOC followability.
While the embodiment has been described with reference to the parallel hybrid vehicle (shown in FIG. 1), it is adaptable as well to a series hybrid vehicle.
FIG. 15 is a system diagram of a series hybrid vehicle to which the system is adaptable.
In the system, an output shaft of an engine 1 and an output shaft of a motor 2 are coaxial and directly coupled together. The single output shaft is coupled to an input shaft of a final reduction gear device 7 through a transmission (belt continuous variable transmission (CVT)) 5 and a clutch 6.
The illustrated embodiment is adaptable as well to the hybrid vehicle of the type illustrated in FIG. 1. In this case, however, the engine 1 and the motor 2 have the same rotational speed. For this reason, by using the engine operation point table of FIG. 4, the engine control mechanism B3 determines respective engine operation points (rotational speeds Ne0 and Ne1, and torques Te0 and Te1) from the requested engine power outputs Pe0 and Pe1. However, the motor control mechanism B4 uses an operation point table as illustrated in FIG. 16 in place of the motor operation point table illustrated in FIG. 5. As already noted, the engine 1 and the motor 2 have the same rotational speed. Therefore, in the event of the rotational speeds of Ne0 and Ne1, when the request motor power outputs are Pm0 and Pm1, motor torques are determined to be Tm0=Pm0/Ne0 and Tm1=Pm1/Ne1, respectively, as shown in FIG. 16.
Thus, the first embodiment has been described with reference to the case where the exhaust purification device is the DPF, and PM deposited therein is burned out under the predetermined regeneration condition. However, the embodiment can be applied as well to the case where the exhaust purification device is a NOx absorber catalyst, and sulfur deposited therein is burned out under a predetermined regeneration condition.
In this case, as shown in FIG. 17, the target value Et of the charge amount SOC in the battery is set corresponding to the amount of sulfur deposits (amount of sulfur poisoning) in the NOx absorber catalyst.
The amount of sulfur deposits (amount of sulfur poisoning) can be estimated in such a manner that the amounts of sulfur poisoning per unit time are estimated from an operational state of the engine and integrated. Alternatively, the amount of sulfur poisoning can be simply estimated from an integrated travel distance.
The exhaust purification system may be implemented using an approach both similar to and in some ways different from the approach discussed above. Once again referring to FIG. 1, the engine 1 is, for example, a diesel engine, which is capable of generating an arbitrary torque by controlling the fuel injection quantity and the like. Further, the engine 1 is capable of raising the exhaust temperature through retardation in fuel injection timing (including post-injection in either the expansion stroke or exhaust stroke).
However, when the elevation of the exhaust temperature is implemented simply by the retardation in fuel injection timing, fuel consumption and exhaust gas (HC) become aggravated, especially at low speed and low load. Further, there arises a concern about oil dilution (fuel deposits onto a cylinder wall widely exposed in a piston descending state, and the fuel deposited on the wall is mixed into the oil, whereby the oil is diluted).
Thus, under some circumstances it may be desirable for the fuel injection timing in the engine 1 to be retarded in a temperature elevation request event for regeneration of the exhaust purification device (DPF 11, NOx absorber catalyst 10) as described above, thereby to elevate the exhaust temperature and to increase the power output of the engine 1. In addition, the motor 2 is driven by an excess power output with respect to a requested power output to generate the power, whereby the high load power generation operation of the engine 1 is carried out to thereby elevate the exhaust temperature. That is, the internal combustion engine 1 and the electric motor 2 undergo the cooperative control to prevent the battery 4 from being overcharged in the event of regeneration control. Consequently, the amount of retardation in the fuel injection timing is maintained to a level that substantially does not cause, for example, an undesirable aggravation of the fuel consumption and exhaust gas and oil dilution. Concurrently, the amount of power generated in the power generation operation is maintained to a level that does not cause overcharge, thereby to make it possible to obtain a sufficient temperature elevation effect. Once again, an example of cooperative control may be illustrated using the regeneration of the DPF 11.
FIG. 18 is a control block diagram of the hybrid vehicle. For convenience, while the actual mechanisms may be somewhat different as discussed below, the same nomenclature is used between FIGS. 2 and 18.
The vehicle includes operation state detecting mechanism BI for detecting the operation state of the vehicle; operation point determining mechanism B2 for determining respective operation points of the engine and motor in accordance with the detection results; engine control mechanism B3 for controlling the engine in accordance with a determined engine operation point; and motor control mechanism B4 for controlling the motor in accordance with a determined motor operation point.
More specifically, the operation point determining mechanism B2 is configured to alter an operation point in accordance with an operation mode specified by operation mode altering mechanism B5 in the relation with the regeneration control of the DPF 11. The operation mode altering mechanism B5 contains information input from a DPF deposit amount estimating mechanism B6 (sometimes called the temperature elevation specifying mechanism), DPF temperature detecting mechanism B7, and charge amount detecting mechanism B8.
The DPF deposit amount estimating mechanism B6 estimates a PM deposit amount in the DPF 11, and determines timing at which the estimated result is a predetermined value or more to be regeneration timing, thereby to generate a temperature elevation request. The DPF deposit amount estimating mechanism B6 uses, for example, a differential pressure sensor that detects between an upstream exhaust pressure in the DPF 11 and a downstream exhaust pressure therein, thereby to estimate a PM deposit amount from the detected differential pressure and an engine operation state (volume of exhaust flow or engine speed and load defining the volume of exhaust flow). Alternatively, the PM deposit amount can be estimated in such a manner that the amounts of collected PM per unit time are estimated from the engine operation state, and the results are integrated.
The DPF temperature detecting mechanism B7 detects a DPF temperature T by using, for example, a sensor that detects, for example, the temperature of a DPF carrier or exhaust temperatures of a downstream side and/or upstream side of the DPF 11.
The charge amount detecting mechanism B8 detects a charge amount SOC in the battery through the integration of charge and discharge currents by using a current sensor that detects charge and discharge currents of the battery 4. Normally, the charge amount SOC is obtained as a ratio (%) with respect to the full amount of charge.
A current compensating mechanism B9 is provided in communication with the motor control mechanism B4. The current compensating mechanism B9 performs current control to reduce the power generation efficiency of the motor 2 via an inverter under a predetermined condition. More specifically, the current compensating mechanism B9 can reduce the power generation efficiency by carrying out current compensation via an inverter to supply AC power corresponding to a phase component with an advance of an electrical angle of 180 degrees with respect to magnetic fields of the magnet of the motor 2 (thereby increasing the amplitude of the AC current).
Operation modes to be specified by the operation mode altering mechanism B5 correspondingly to, for example, the state of the DPF will be described here below.
The operation modes are a normal mode (M=4), a power generation amount increase mode (M=5), a power generation amount restriction mode (M=6), a power generation amount restriction-plus-current compensation mode (M=7), and a motor driven travel mode (M=8). The respective modes will be described here below.
The normal mode (M=4) is a normal operation mode. In this mode, a total power output Pt requested for the vehicle is calculated in accordance with operation state information received from the operation state detecting mechanism B1. In addition, an engine power output Pe and a motor power output Pm are determined from the total power output Pt by using a hybrid power output (engine/motor power output) distribution table as illustrated in FIG. 19, which shows a distribution of hybrid power output with respect to the total power output. Then, the determination results are supplied for commands to the engine control mechanism B3 and the motor control mechanism B4.
In the engine control mechanism B3, an operation point is determined by using an engine operation point table such as that illustrated in FIG. 4 in accordance with the determined engine power output Pe. The operation point table is created by setting combinations of torques (Te0, Te1, . . . ) and rotational speeds (Ne0, Ne1, . . . ), which optimize fuel consumption, with respect to respective engine power output values (Pe0, Pe1, . . . ).
In the motor control mechanism B4, an operation point is determined by using a motor operation point table as illustrated in FIG. 21 in accordance with the determined motor power output Pm0. The operation point table is created by setting combinations of torques (Tm0, Tm1, . . . ) and rotational speeds (Nm0, Nm1, . . . ), which optimize fuel consumption, with respect to the respective motor power output values (Pm0, Pm1, . . . ).
The power generation amount increase mode (M=5) is an operation mode for use in the case when a temperature elevation request for the DPF 11 is present, and the charge amount SOC in the battery 4 is smaller than a first predetermined value EmL. In this mode, the engine power output is largely increased to thereby largely increase the amount of power generated. The mode is thus set for the reason that the exhaust temperature is raised through a high load operation of the engine 1 to thereby promote the elevation of the DPF temperature. As such, the engine power output Pe and the motor power output Pm are determined from the requested total power output Pt by using a hybrid power output distribution table of FIG. 22. Then the determination results are supplied for commands to the engine control mechanism B3 and the motor control mechanism B4. In the hybrid power output distribution table as shown in FIG. 22, the engine power output Pe is set to a relatively large fixed value Pec in the entire zone. Thereby, in a low/intermediate power output zone, an excess amount (Pec−Pt) of the engine power output with respect to the requested total power output Pt is set to be the amount of power generated in the motor.
The power generation amount restriction mode (M=6) is an operation mode for use in the case when a DPF temperature elevation request is present, and the battery charge amount SOC is larger than the first predetermined value EmL and is smaller than a second predetermined value EmH. In this mode, the amount of power generated is increased by increasing the engine power output for exhaust temperature elevation. However, the charge amount SOC is relatively large, such that the amount of power generated is restricted, and the fuel injection timing is retarded corresponding to the restriction, thereby to elevate the exhaust temperature. More specifically, compared to the case of the power generation amount increase mode (M=5), in the power generation amount restriction mode (M=6), the fuel injection timing is retarded, and the power output increase amount in the internal combustion engine or the power generation amount corresponding to the power output increase in the engine is reduced. In this event, a power output increase amount in the internal combustion engine or the power generation amount corresponding to the power output increase in the engine is determined so that the amount of retardation in the fuel injection timing falls within a range of amount of retardations that does not cause exhaust gas aggravation or oil dilution. As such, an engine power output Pe and a motor power output Pm are determined from a requested total power output Pt by using a hybrid power output distribution table as illustrated in FIG. 23. Then, the determined power outputs Pe and Pm are supplied for commands to the engine control mechanism B3 and the motor control mechanism B4. In the hybrid power output distribution table of FIG. 23, the engine power output Pe is set to a relatively small fixed value Pes in the entire zone. Thereby, in a low power output zone, an excess amount (Pes−Pt) of the engine power output with respect to the requested total power output Pt is set to be an amount of power generated in the motor.
The engine operation point table to be used in the power generation amount restriction mode (M=6) can be identical to the table of FIG. 20. In this case, however, there occurs no operation such as that, as shown in FIG. 24, in a low speed-plus-low load region (hatched range) in which, for example, oil dilution and HC aggravation tend to be caused by the retardation in the fuel injection timing.
Further, as shown in FIG. 25, the amount of retardation in the fuel injection timing (with respect to the power generation amount increase mode (M=5)) in the power generation amount restriction mode (M=6) is reduced toward the higher load side in correspondence to the rotational speed and the torque.
The power generation amount restriction-plus-current compensation mode (M=7) is an operation mode for use in the case where a DPF temperature elevation request is present, the battery charge amount SOC is larger than the second predetermined value EmH, and the DPF temperature T is relatively low (in the case where the catalyst is inactive). In this mode, the power generation amount has to be further restricted, so that current compensation is carried out in addition to the operation in the power generation amount restriction mode (M=6).
More specifically, in the event of power generation, the power generation efficiency of the motor 2 is reduced by carrying out the current compensation via the inverter 3 to supply AC power corresponding to a phase component with an advance of an electrical angle of 180 degrees with respect to magnetic fields of the magnet of the motor 2 (thereby increasing the amplitude of the AC current). In other words, in the event of control of the AC current by using the inverter 3, of the amplitudes of components with a high efficient (loss-free) phase and a low efficient phase (D-axis phase) of the AC current, the amplitude of components with the low efficient phase is controlled to be large than usual. Thereby, the power generation efficiency is reduced, and the energy is converted to heat.
In this case, by using the hybrid power output distribution table of FIG. 23, a current compensation value ΔId (D-axis current compensation value) is preferably determined corresponding to a motor power generation amount ΔP (=Pes−Pt) at which the engine power output is higher than the requested total power output Pt. More specifically, as shown in FIG. 26, the current compensation value ΔId is preferably set to be larger as the motor power generation amount AP becomes larger.
The motor driven travel mode (M=8) is an operation mode for use in the case where a DPF temperature elevation request is present, the charge amount SOC in the battery is higher than the second predetermined value EmH, and the DPF temperature T is relatively higher (in the case where the catalyst is active). In this mode, the power output is obtained only from the motor 2 (motor power output: 100%). More specifically, the battery charge amount SOC is reduced by the motor driven travel, and concurrently, the engine 1 is draggedly rotated (“dragged,” herein below) along at a predetermined rotational speed, whereby air for combustion is supplied to the DPF 11. Oxygen contained in the supplied air reacts with PM in the DPF 11 and causes combustion, thereby making it possible to elevate the temperature of the exhaust purification device. In this case, the predetermined rotational speed is a rotational speed at which a DPF-temperature elevatable amount of air is supplied, and is set to be not excessively high to the extent of causing air cooling.
Under a predetermined condition where the temperature is reduced by air supply to the DPF 11, however, (where the DPF temperature is relatively low and the temperature is reduced by air cooling) and in the event of the motor driven travel, any one of control processes (1) to (3) described here below may be implemented.
(1) The drag rotation is cancelled, and the engine 1 is stopped, thereby to stop air supply to the DPF 11. More specifically, as shown in FIG. 27, while the engine 1 is dragged by bringing a clutch 6 e into engagement (as illustrated in FIG. 1) only when the DPF temperature is not lower than a predetermined value Tc, the engine 1 is stopped by releasing the clutch 6e when the DPF temperature is lower than the predetermined value Tc.
(2) While the engine 1 is dragged, the air supply to the DPF 11 is reduced by setting a throttle valve in an intake system to a full open position in a fuel cut state.
(3) While the engine 1 is dragged, the air supply to the DPF 11 is reduced in such a manner that an exhaust gas recirculation (EGR) valve provided in an EGR passageway for returning the exhaust gas to the intake system is set to a full open position in a fuel cut state.
FIG. 28 is a flow chart illustrating a flow of control. In step A1, the process determines the presence or absence of a DPF temperature elevation command (regeneration request). More specifically, the process reads a PM deposit amount (estimated value) in the DPF 11, which is calculated in a different routine. Then, the process determines whether or not the read value is greater than or equal to a predetermined value for regeneration timing determination.
If a DPF temperature elevation command is absent as a result of the determination in step A1, the process proceeds to step A1. In step A1, the mode is set to and maintained in the normal mode (M=4).
If a DPF temperature elevation command is present as a result of the determination in step A1, the process proceeds to step A2. In step A2, it is determined whether or not the battery charge amount SOC is larger than a first predetermined value EmL. The first predetermined value EmL is a value set to a level on a relatively low side, and a value lower than the level does not cause over discharge even when the battery is sufficiently charged.
If SOC<Eml (if SOC is a low level) as a result of the determination in step A2, the process proceeds to step A9. In step A9, the mode is set to the power generation amount increase mode (M=5).
If SOC>EmL as a result of the determination in step A2, the process proceeds to step A3, in which the process determines whether or not the battery charge amount SOC is higher than a second predetermined value EmH. The second predetermined value EmH is set to a level on a relatively high side (EmH>EmL), and a level higher than the level is determined to be a level at which the power generation is desired to be stopped as early as possible.
If SOC<EmH, that is, if EmL<SOC<EMH (i.e., if SOC is an intermediate level as a result of the determination in step A3, the process proceeds to step A6. Unless the present mode is the motor driven travel mode (M=8) as a result of the determination in step A6, the process proceeds to step A8, in which the mode is set to the power generation amount restriction mode (M=6). Step A6 will be described further below.
Alternately, if SOC>EmH (that is, if SOC is the high level) as a result of the determination in step A3, the process proceeds to step A4, wherein the process determines whether or not the DPF temperature is a catalyst activation temperature or higher.
If SOC is at a high level and the DPF temperature is low (if the DPF 11 is in an inactive state), the process proceeds from step A4 to step A7. In step A7, the process sets the mode to the power generation amount restriction-plus-current compensation mode (M=7).
Alternately, if SOC is the high level and the DPF temperature is high (if the DPF 11 is in an active state), the process proceeds from step A4 to step A5, in which the mode is set to the motor driven travel mode (M=8).
Thus, if the exhaust purification device is inactive, then current control is carried out to reduce the power generation efficiency of the motor 2. Alternately, if the exhaust purification device is active, the hybrid vehicle is driven only or exclusively by the power output of the motor 2, and the internal combustion engine 1 is driven (rotated). Thereby, the air is supplied to the exhaust purification device.
Step A6 will now be further described. As described above, as SOC reaches a high level, the DPF temperature is at a high temperature state (active state), and the mode is set in step A5 to the motor driven travel mode (M=8). Thereafter, SOC is reduced to an intermediate level by the SOC reduction due to the motor driven travel operation, and the process proceeds from step A3 to step A6. As a result of the determination in step A6, “M=8” is detected as a mode, so that the process proceeds to step A4. If the DPF temperature is in the high temperature state in step A4, the motor driven travel mode (M=8) set in step A5 is continued. Alternately, if the DPF temperature is in the low temperature state, the mode is shifted to the power generation amount restriction-plus-current compensation mode (M=7) corresponding to step A7. In the event that SOC remains in the intermediate level in the state where a temperature elevation command is present, the process again proceeds to from step A3 to step A6 in the next operation cycle. As a result of the determination in step A6, “M=4” is detected, so that the process proceeds to step A8, in which the mode is set to the engine power output increase mode (M=3).
The flow control of FIG. 28 is now discussed with reference to timing charts of FIGS. 29 and 30. First, the process related to the timing chart of FIG. 29 is addressed. At time t1, a temperature elevation command for DPF regeneration turns ON. In this event, if the battery charge amount SOC is smaller than the first predetermined value EmL, the mode is shifted from the normal mode (M=4) to the power generation amount increase mode (M=5). Thereby, the motor 2 is driven by the engine 1 to generate the power without retardation in the fuel injection timing in the engine 1. Concurrently, the exhaust temperature is elevated by the high load power generation operation of the engine 1, thereby to elevate the DPF temperature T. The amount of power generated in this case is charge into the battery 4.
If the battery charge amount SOC exceeds the first predetermined value EmL at time t2, the mode is shifted to the power generation amount restriction mode (M=6). Thereby, the fuel injection timing in the engine 1 is retarded, and the motor 2 is driven by the engine 1 to generate the power. Then, the exhaust temperature is elevated by both the engine 1 and motor 2, thereby to elevate the DPF temperature T. The amount of power generated in this case can be reduced corresponding to the temperature elevated by the retardation in the fuel injection timing.
Suppose that, at time t3, the battery charge amount SOC has reached the second predetermined value EmH and the DPF temperature T has reached the catalyst activation temperature. In this event, the mode is shifted to the motor driven travel mode (M=8). Thereafter, even if the battery charge amount SOC reduces, the motor driven travel mode (M=8) is maintained as long as the value is not lower than the first predetermined value EmL. Thereby, the battery charge amount SOC is reduced by the motor driven travel operation, the engine 1 is dragged along by the motor 2 at a predetermined rotational speed, and the air for combustion is supplied to the DPF 11, whereby the temperature elevation is continued.
When the temperature elevation command turns OFF at time t4, the mode is shifted to the normal mode (M=4).
The case of the timing chart of FIG. 30 will now be described.
In the same manner as in the case of FIG. 29, the mode is shifted from the normal mode (M=4) to the power generation amount increase mode (M=5) at time t1, and the mode is shifted to the power generation amount restriction mode (M=6) at time t2.
However, if at time t3, the battery charge amount SOC has reached the second predetermined value EmH, but the DPF temperature T has not yet reached the catalyst activation temperature, the mode is shifted to the power generation amount restriction-plus-current compensation mode (M=7). Thereby, the fuel injection timing in the engine 1 is retarded, the motor 2 is driven by the engine 1 to thereby generate the power, and current compensation is carried out to reduce the power generation efficiency of the motor 2. Consequently, while increase in the battery charge amount SOC is restrained, and concurrently, the requested temperature elevation can be accomplished.
At time t4, the mode is shifted to the normal mode (M=4) when the temperature elevation command turns OFF.
As described above, according to the present embodiment, in response to a temperature elevation request for the DPF 11, the fuel injection timing in the engine 1 is retarded and the motor 2 is driven by the engine 1 to generate the power. Consequently, the amount of retardation in the fuel injection timing is restrained to a level that substantially does not cause, for example, aggravation of the fuel consumption and exhaust gas. Further, while the power generation amount in the power generation operation is restrained that does not cause overcharging, sufficient temperature elevation effects can be secured.
Further, according to the present embodiment, the amount of power generated in the power generation is set to a range in which the engine power output is maintained at a sufficiently large level that does not cause aggravation of the exhaust gas due to the retardation in the fuel injection timing. Consequently, significant aggravation of the exhaust gas (HC) or oil dilution can be securely restrained, and the amount of charge can be reduced.
Further, according to the present embodiment, the configuration includes a mechanism that detects the battery charge amount SOC. In the configuration, if the battery charge amount SOC is lower than the first predetermined value EmL when a DPF temperature elevation request is present, the motor 2 is driven by the engine 1 to generate the power without retardation in the fuel injection timing in the engine 1. On the other hand, if the battery charge amount SOC is higher than the first predetermined value EmL, and the motor 2 is driven by the engine 1 to generate the power. Thus, the amount of power generated in this case is reduced to be smaller than the amount of power generated in the case where the battery charge amount SOC is lower than the first predetermined value EmL. This makes it possible to implement appropriate control of the power generation amount corresponding to the battery charged state.
Further, according to the present embodiment, regardless of variation in the requested total power output Pt0, the power generation is performed by controlling the engine power output Pe to be the fixed value. When the battery charge amount SOC is higher than the first predetermined value EmL, the constant value is reduced to be smaller than the constant value in the case where the battery charge amount SOC is lower than the first predetermined value EmL (the fixed value Pes in the case of SOC larger than EmL is reduced to be smaller than the fixed value Pec in the case of SOC lower than EmL). Thereby, power generation is performed in a lower power output zone while the motor power output ratio is increased to increase the number of discharge instances in an intermediate/high power output zone. Consequently, aggravation of the exhaust gas (HC) and oil dilution due to the injection timing retardation in the low power output zone can be restrained, and the exhaust temperature can be elevated.
Further, according to the present embodiment, in the event of power generation, current control is carried out to reduce the power generation efficiency of the motor 2. Consequently, while the temperature elevation effects are enhanced by increasing the engine load, the amount of charge into the battery is reduced to thereby make it possible to prevent overcharging.
Further, according to the present embodiment, when the battery charge amount SOC is higher than the second predetermined value EmH set higher than the first predetermined value EmL in the presence of a temperature elevation request for the exhaust purification device (DPF), the fuel injection timing in the engine 1 is retarded. In addition, the motor 2 is driven by the engine 1 to generate the power, and current control is carried out to reduce the power generation efficiency of the motor 2. Consequently, in the state where the charge amount SOC is high, the temperature elevation effects are enhanced by increasing the engine load, the amount of charge into the battery is reduced to thereby make it possible to prevent overcharging.
Further, according to the present embodiment, the current control is carried out corresponding to the power generation amount ΔP (=Pes−Pt) at which the engine power output is higher than the requested total power output Pt. In this manner, the power generation efficiency is reduced to be lower as the excess amount of generated power is larger, thereby to prevent the amount of generated power being used for discharging. In addition, when the excess amount of generated power is small, heat generation in the motor 2 can be prevented by enhancing the power generation efficiency
Further, according to the present embodiment, when the battery charge amount SOC is higher than the second predetermined value EmH set higher than the first predetermined value EmL in the presence of a temperature elevation request for the exhaust purification device (DPF), the operation is shifted to the motor driven travel operation in which the power output is obtained only from the motor 2. Concurrently, the engine 1 is dragged by the motor 2 at the predetermined rotation speed to supply the combustion air (oxygen) to the exhaust purification device (DPF). Thereby, while the charge amount SOC is reduced by the motor driven travel operation, combustion (PM combustion) can be promoted, and either temperature elevation can be promoted or temperature reduction can be restrained.
Further, according to the present embodiment, the predetermined rotational speed is set to the rotational speed at which the amount of air capable of elevating the temperature of the exhaust purification device (DPF) can be supplied. Thereby, it is possible to prevent an event where the rotational speed is excessively high to the extent of causing air cooling. Consequently, temperature elevation can be promoted effectively.
Further, according to the present embodiment, under the predetermined condition where the temperature is reduced by air supply to the exhaust purification device (DPF) (for example, the condition where either the DPF is inactive or the PM deposit amount corresponding to the DPF temperature is not larger than the predetermined value) during the motor driven travel operation, the engine 1 is stopped by canceling the drag rotation (by releasing the clutch) to stop air supply to the exhaust purification device (DPF). Thereby, while the charge amount SOC is reduced by the motor driven travel operation, heat insulation of the exhaust purification device (DPF) can be implemented by cutting out gases that can serve as coolant.
Further, according to the present embodiment, under the predetermined condition where the temperature is reduced by air supply to the exhaust purification device (DPF) during the motor driven travel operation, the throttle valve in the engine I is set to the full open position to reduce the amount of air supply to the exhaust purification device (DPF). In this manner, while the charge amount SOC is reduced by the motor driven travel operation, heat insulation of the exhaust purification device (DPF) can be implemented by either cutting out or reducing gases that can serve as coolant.
Additionally, according to the present embodiment, under the predetermined condition where the temperature is reduced by air supply to the exhaust purification device (DPF) during the motor driven travel operation, the EGR valve in the engine 1 is set to the full open position to reduce the amount of air supply to the exhaust purification device (DPF). In this manner, while the charge amount SOC is reduced by the motor driven travel operation, heat insulation of the exhaust purification device (DPF) can be implemented by either cutting out or reducing gases that can serve as coolant.
While the embodiment first discussed with respect to FIG. 18 has been described with reference to the parallel hybrid vehicle (shown in FIG. 1), it is adaptable as well to a series hybrid vehicle.
FIG. 15 is a system diagram of a series hybrid vehicle to which the present embodiment is adaptable.
In the system, an output shaft of an engine 1 and an output shaft of a motor 2 are coaxial and directly coupled together. The single output shaft is coupled to an input shaft of a final reduction gear device 7 through a transmission (belt continuous variable transmission (CVT)) 5 and a clutch 6.
The embodiment is adaptable as well to the hybrid vehicle of the above-described type. In this case, however, the engine 1 and the motor 2 have the same rotational speed. As such, by using the engine operation point table of FIG. 20, the engine control mechanism B3 determines respective engine operation points (rotational speeds Ne0 and Ne1, and torques Te0 and Te1) from the requested engine power outputs Pe0 and Pe1. However, the motor control mechanism B4 uses the operation point table of FIG. 16 in place of the motor operation point table of FIG. 21. The engine 1 and the motor 2 have the same rotational speed. For this reason, when the request motor power outputs are Pm0 and Pm1 in the event of the rotational speeds of Ne0 and Ne1, motor torques are determined to be Tm0=Pm0/Ne0 and Tm1=Pm1/Ne1, respectively, as shown in FIG. 16.
Thus, the embodiment discussed in FIG. 18 has been described with reference to the case where the exhaust purification device is the DPF, and PM deposited therein is burned out under the predetermined regeneration condition. However, the embodiment can be applied as well to the case where the exhaust purification device is a NOx absorber catalyst, and sulfur deposited therein is burned out under a predetermined regeneration condition. However, the characteristics in FIG. 27 in the motor driven travel mode (M=8) are adapted only during the DPF regeneration.
The preceding description has been presented only to illustrate and describe exemplary embodiments of the claimed invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. The invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. The scope of the invention is limited solely by the following claims.

Claims

1. An exhaust purification system for a hybrid vehicle comprising:

an internal combustion engine having an exhaust purification device disposed in an exhaust gas passage of the engine to treat exhaust gas components contained in exhaust gas from the engine;

a motor generator capable of generating electric power by being driven by the engine;

a battery arranged and configured to be selectively charged with electric power generated by the motor generator; and

at least one controller arranged and configured to selectively perform a regeneration control of the exhaust purification device under a predetermined regeneration condition, in which deposits accumulated in the exhaust purification device are burned and removed by increasing exhaust gas temperature through an increase in power output of the engine, and an excess power output caused by the increase in power output of the engine is used to generate the electric power by the motor generator, and

wherein the at least one controller is further arranged and configured to control the engine and the motor generator so that the battery is prevented from overcharging by the electric power associated with the regeneration control of the exhaust purification device.

2. The exhaust purification system according to claim 1, wherein a state of charge of the battery is reduced by selectively increasing a power output of the motor generator before the regeneration control.

3. The exhaust purification system according to claim 2, wherein a target value of the state of charge of the battery is determined corresponding to an accumulated level of the deposits in the exhaust purification device.

4. The exhaust purification system according to claim 3, wherein the target value of the state of charge of the battery becomes smaller as the accumulated level of the deposits becomes larger.

5. The exhaust purification system according to claim 2, wherein a determination as to timing for increasing the power output of the motor generator before the regeneration control is made in accordance with an accumulated level of the deposits.

6. The exhaust purification system according to claim 2, further including a compensation selectively adjusting a distribution of the power output of the engine with respect to a requested total power output of the vehicle.

7. The exhaust purification system according to claim 6, wherein the requested total power output where the engine starts the power output of the internal combustion engine is set to increase with the compensation.

8. The exhaust purification system according to claim 6, wherein an upper limit value that is set for the power output of the engine is set to reduce with the compensation.

9. The exhaust purification system according to claim 6, wherein the distribution of the power output of the engine with respect to at least one of the requested total power output and the power output of the motor generator is set to reduce with the compensation.

10. The exhaust purification system according to claim 6, wherein a compensation amount of the compensation is varied corresponding to a deviation amount between an actual value and a target value of the state of charge of the battery.

11. The exhaust purification system according to claim 10, wherein the compensation selectively performs when the actual value of the state of charge is larger than the target value of the state of charge, but not to perform when the actual value is smaller than the target value.

12. The exhaust purification system according to claim 1, wherein a fuel injection timing of the engine is retarded in the regeneration control of the exhaust purification device.

13. The exhaust purification system according to claim 12, wherein at least one of an amount of the increase in power output of the engine and an amount of the electric power generated by the motor generator associated with the increase in power output of the engine is determined so that a retard amount of the fuel injection timing is prevented from falling within a range of retard amount that causes exhaust gas aggravation or oil dilution.

14. The exhaust purification system according to claim 12, wherein when the state of charge of the battery is lower than a first predetermined value, the electric power generation by the increase in power output of the engine is performed without retarding the fuel injection timing, and when the state of charge of the battery is higher than the first predetermined value, the fuel injection timing is retarded and the electric power generation by the increase in power output of the internal combustion engine is performed.

15. The exhaust purification system according to claim 14, wherein the power output of the engine during the regeneration control is set at a fixed value regardless of a requested total power output.

16. The exhaust purification system according to claim 14, wherein at least one of an amount of the increase in power output of the engine and an amount of the electric power generated by the motor generator associated with the increase in power output of the engine in the case where the state of charge of the battery is larger than the first predetermined value is smaller than that in the case where the state of charge is lower than the first predetermined value.

17. The exhaust purification system according to claim 12, wherein a current control is performed so that an electric power generation efficiency of the motor generator is reduced when the motor generator generate the electric power.

18. The exhaust purification system according to claim 14, wherein a current control is performed so that an electric power generation efficiency of the motor generator is reduced when the state of charge of the battery is greater than a second predetermined value that is higher than the first predetermined value.

19. The exhaust purification system according to claim 17, wherein the current control is performed corresponding to an amount of the electric power generated by the motor generator at which the power output of the engine is larger than the requested total power output.

20. The exhaust purification system according to claim 14, wherein, when the state of the charge of the battery is greater than a second predetermined value that is greater than the first predetermined value, the hybrid vehicle is driven only by the power output of the motor generator and the engine is rotated by the motor generator to supply air to the exhaust purification device.

21. The exhaust purification system according to claim 20, wherein the engine is rotated by the motor generator at a rotational speed where an amount of the air is capable of elevating the temperature of the exhaust purification device through combustion in the exhaust purification device.

22. The exhaust purification system according to claim 20, wherein, under a condition where the exhaust purification device is cooled down by the air supplied to the exhaust purification device when the hybrid vehicle is driven only by the power output of the motor generator, the rotation of the engine driven by the motor generator is stopped so that the air supply to the exhaust purification device is stopped.

23. The exhaust purification system according to claim 20, wherein, under a condition where the exhaust purification device is cooled down by the air supplied to the exhaust purification device when the hybrid vehicle is driven by the power output of the motor generator, a throttle valve of the engine is fully closed so that the air supply to the exhaust purification device is stopped.

24. The exhaust purification system according to. Claim 20, wherein, under a condition where the exhaust purification device is cooled down by the air supplied to the exhaust purification device when the hybrid vehicle is driven by the power output of the motor generator, an EGR valve of the engine is fully opened so that the air supply to the exhaust purification device is reduced.

25. The exhaust purification system according to claim 14, wherein in the event that the state of charge of the battery is larger than a second predetermined value that is larger than the first predetermined value, when the exhaust purification device is inactive, a current control is performed so that an electric power generation efficiency of the motor generator is reduced, and when the exhaust purification device is active, the hybrid vehicle is driven by the power output of the motor generator and the engine is rotated by the motor generator, providing an air supply to the exhaust purification device.

26. An exhaust purification system for a hybrid comprising:

an internal combustion engine;

first means for treating exhaust gas components contained in exhaust gas from the engine;

second means for generating electric power by being driven by the engine;

a battery being selectively charged with electric power generated by the second means; and

third means for performing a regeneration of the first means under a predetermined regeneration condition, in which deposits accumulated in the first means are removed by increasing exhaust gas temperature through an increase in power output of the internal combustion engine, and an excess power output caused by the increase in power output of the internal combustion engine is used to generate electric power by the second means, and wherein the internal combustion engine and the second means is controlled so that the battery is prevented from overcharging by the electric power associated with the regeneration of the first means.

27. A method of controlling an exhaust purification system for a hybrid vehicle including an engine and an electric motor capable of being driven by the engine, a battery being selectively charged with electric power generated by the electric motor; an exhaust purification device provided in an exhaust passageway of the engine, comprising:

performing a regeneration of an exhaust purification device under a predetermined regeneration condition in which deposits accumulated in the exhaust purification device is removed by increasing exhaust gas temperature through an increase in power output of an engine;

absorbing an excess power output associated with the increase in power output of the engine by an electric motor; and

controlling the engine and the electric motor so that a battery is prevented from overcharging by the electric power caused by the regeneration of the exhaust purification device.

28. The method as recited in claim 27, wherein a power output of the electric motor is increased before performing the regeneration such that a state of charge of the battery is reduced.

29. The method as recited in claim 27, wherein a fuel injection timing of the engine is retarded during the regeneration of the exhaust purification device.