Abstract:
In order to finish the regeneration step in a short time and improve fuel efficiency, a regeneration control device for a post-processing device of a hybrid vehicle is constructed such that, at the time of deceleration during the regeneration of the post-processing device, the hybrid vehicle is driven by the electric motor, and the engine is controlled so as to retain a rotation speed suitable for the regeneration of the post-processing device in a manner irrelevant to the driving system, and a control force equivalent to the braking force provided by the engine brake is generated by the recovery of the electric motor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a U.S. national stage of application No. PCT/JP2011/074178, filed on Oct. 20, 2011. Priority under 35 U.S.C.§119(a) and 35 U.S.C.§365(b) is claimed from Japanese Patent Application No. 2010-236611, filed on Oct. 21, 2010, the disclosure of which are also incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a regeneration control device, a hybrid vehicle, a regeneration control method, and a computer program. 
       BACKGROUND ART 
       [0003]    A vehicle having a diesel engine includes a post-processing device for removing, for example, the particulate matter contained in the exhaust gas. Such a post-processing device needs implementation of a process called “regeneration” in which the engine is operated under high load to burn off the particulate matter accumulated in a filter in order to prevent the filter to get clogged (for example, see patent literature PTL1). 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PTL1: JP 2006-275009 A 
       
     
         [0005]    During the implementation of the above-mentioned “regeneration”, the engine needs to be operated under high load. However, when the engine braking is used, for example, when the vehicle runs on a long downgrade, the fuel supply to the engine needs to be halted, and thus the process of the “regeneration” is suspended during that time. 
         [0006]    Once the process of the “regeneration” is suspended as described above, the temperature of the post-processing device decreases. This requires time to increase the temperature of the post-processing device again and delays the completion of the “regeneration”. Further, the “regeneration” requires the high load operation of the engine and thus the prolongation of the “regeneration” causes the fuel efficiency to become worse. 
         [0007]    In light of the foregoing, an objective of the present invention is to provide a regeneration control device, a hybrid vehicle, a regeneration control method, and a computer program that completes the process of “regeneration” in a short time so that the fuel efficiency can be improved. 
       Solution to Problem 
       [0008]    An aspect of the present invention relates to a regeneration control device. According to the present invention, there is provided a regeneration control device of a post-processing device in a hybrid vehicle that includes an engine and an electric motor and that is capable of running by the engine or the electric motor or capable of running by a cooperation between the engine and the electric motor, that is capable of performing regenerative power generation with the electric motor at least during deceleration, and that includes the post-processing device for exhaust gas. The regeneration control device, when the vehicle decelerates during the regeneration of the post-processing device, causes the vehicle to run with the electric motor, controls the engine to maintain a rotational speed appropriate for the regeneration of the post-processing device independently from a driving system, and generates braking force equivalent to braking force of engine braking by the regeneration with the electric motor. 
         [0009]    Further, the exhaust brake may be operated during the regeneration of the post-processing device. 
         [0010]    Another aspect of the present invention relates to a hybrid vehicle including the regeneration control device according to the present invention. 
         [0011]    Another aspect of the present invention relates to a regeneration control method. According to the present invention, there is provided a regeneration control method of a post-processing device in a hybrid vehicle that includes an engine and an electric motor and that is capable of running by the engine or the electric motor or capable of running by a cooperation between the engine and the electric motor, that is capable of performing regenerative power generation with the electric motor at least during deceleration, and that includes the post-processing device for exhaust gas. The regeneration control method, when the vehicle decelerates during the regeneration of the post-processing device, is a method for causing the vehicle to run with the electric motor, controlling the engine to maintain a rotational speed appropriate for the regeneration of the post-processing device independently from a driving system, and generating braking force equivalent to braking force of engine braking by the regeneration with the electric motor while the engine braking is required. 
         [0012]    Another aspect of the present invention relates to a computer program for causing an information processing apparatus to implement a function equivalent to a function of the regeneration control device according to the present invention. 
       Advantageous Effects of Invention 
       [0013]    According to the present invention, the process of “regeneration” is completed in a short time so that the fuel efficiency can be improved. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a block diagram for illustrating an exemplary structure of a hybrid vehicle according to an embodiment of the present invention. 
           [0015]      FIG. 2  is a block diagram for illustrating an exemplary configuration of a function implemented in a hybrid ECU illustrated in  FIG. 1 . 
           [0016]      FIG. 3  is a flowchart for illustrating a regeneration control process by a post-processing device regeneration control unit illustrated in  FIG. 2 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0017]    Hereinafter, the hybrid vehicle according to an embodiment of the present invention will be described with reference to  FIGS. 1 to 3 . 
       [Outline] 
       [0018]    A hybrid vehicle includes an engine and an electric motor and can run with the engine or the electric motor, or can run by the cooperation between the engine and the electric motor, and thus can use the regeneration torque of the electric motor as braking force instead of the engine braking. Accordingly, in the hybrid vehicle  1  according to the embodiment of the present invention, when the vehicle decelerates during the “regeneration” of the post-processing device, the regeneration torque of the electric motor provides braking force equivalent to the engine braking and the engine continues the high load operation for the “regeneration” even if the engine braking is required. 
       Embodiment of the Present Invention 
       [0019]      FIG. 1  is a block diagram for illustrating an exemplary structure of a hybrid vehicle  1 . The hybrid vehicle  1  is an example of a vehicle. 
         [0020]    The hybrid vehicle  1  includes the engine  10 , an engine Electronic Control Unit (ECU)  11 , a clutch  12 , the electric motor  13 , an inverter  14 , a battery  15 , a transmission  16 , a motor ECU  17 , a hybrid ECU  18 , a wheel  19 , a post-processing device  20 , an exhaust braking electromagnetic valve  21 , a key switch  22 , and a shift unit  23 . The transmission  16  includes an automated mechanical/manual transmission, and is operated by the shift unit  23  including a drive range (hereinafter, referred to as a D (Drive) range). Note that the automated mechanical/manual transmission is a transmission that can automatically perform a gear shifting operation while having the same structure as a manual transmission. Further, the “driving system” in claims includes, for example, the clutch  12 , the electric motor  13 , the transmission  16 , and the wheel  19 . 
         [0021]    The engine  10  is an example of an internal combustion engine, and is controlled by the engine ECU  11 . The engine  10  internally combusts gasoline, light oil, Compressed Natural Gas (CNG), Liquefied Petroleum Gas (LPG), alternative fuel, or the like in order to generate power for rotating a shaft and transmit the generated power to the clutch  12 . 
         [0022]    The engine ECU  11  is a computer working in coordination with the motor ECU  17  according to the instructions from the hybrid ECU  18 , and controls the engine  10 , for example, the amount of fuel injection and the valve timing. For example, the engine ECU  11  includes a Central Processing Unit (CPU), an Application Specific Integrated Circuit (ASIC), a microprocessor (micro-computer), a Digital Signal Processor (DSP), and the like, and internally has an operation unit, a memory, an Input/Output (I/O) port, and the like. 
         [0023]    The clutch  12  is controlled by the hybrid ECU  18 , and transmits the shaft output from the engine  10  to the wheel  19  through the electric motor  13  and the transmission  16 . In other words, the clutch  12  mechanically connects the rotating shaft of the engine  10  to the rotating shaft of the electric motor  13  by the control of the hybrid ECU  18  in order to transmit the shaft output of the engine  10  to the electric motor  13 . On the other hand, the clutch  12  cuts the mechanical connection between the rotating shaft of the engine  10  and the rotating shaft of the electric motor  13  so that the shaft of the engine  10  and the rotating shaft of the electric motor  13  can rotate at different rotational speeds from each other. 
         [0024]    For example, the clutch  12  mechanically connects the rotating shaft of the engine  10  to the rotating shaft of the electric motor  13 , for example, when the hybrid vehicle  1  runs by the power of the engine  10  and this causes the electric motor  13  to generate electric power, when the driving force of the electric motor  13  assists the engine  10 , and when the electric motor  13  starts the engine  10 . 
         [0025]    Further, for example, the clutch  12  cuts the mechanical connection between the rotating shaft of the engine  10  and the rotating shaft of the electric motor  13  when the engine  10  stops or is in an idling state and the hybrid vehicle  1  runs by the driving force of the electric motor  13 , and when the hybrid vehicle  1  reduces the speed or runs on the downgrade and the electric motor  13  generates (regenerates) electric power while the engine  10  stops or is in an idling state. 
         [0026]    Note that the clutch  12  differs from a clutch operated by the driver&#39;s operation of a clutch pedal, and is operated by the control of the hybrid ECU  18 . 
         [0027]    The electric motor  13  is a so-called motor generator that supplies a shaft output to the transmission  16  by generating the power for rotating the shaft using the electric power supplied from the inverter  14 , or that supplies electric power to the inverter  14  by generating the electric power using the power for rotating the shaft supplied from the transmission  16 . For example, when the hybrid vehicle  1  gains the speed or runs at a constant speed, the electric motor  13  generates the power for rotating the shaft to supply the shaft output to the transmission  16  in order to cause the hybrid vehicle  1  to run in cooperation with the engine  10 . Further, the electric motor  13  works as an electric generator, for example, when the electric motor  13  is driven by the engine  10 , or when the hybrid vehicle  1  runs without power, for example, when the hybrid vehicle  1  reduces the speed or runs on the downgrade. In that case, electric power is generated by the power for rotating the shaft supplied from the transmission  16  and is supplied to the inverter  14  in order to charge the battery  15 . 
         [0028]    The inverter  14  is controlled by the motor ECU  17 , and converts the direct voltage from the battery  15  into an alternating voltage or converts the alternating voltage from the electric motor  13  into a direct voltage. When the electric motor  13  generates power, the inverter  14  converts the direct voltage from the battery  15  into an alternating voltage and supplies the electric power to the electric motor  13 . When the electric motor  13  generates electric power, the inverter  14  converts the alternating voltage from the electric motor  13  into a direct voltage. In other words, in that case, the inverter  14  works as a rectifier and a voltage regulator for supplying a direct voltage to the battery  15 . 
         [0029]    The battery  15  is a secondary cell capable of being charged and discharged. The battery  15  supplies electric power to the electric motor  13  through the inverter  14  when the electric motor  13  generates power. Alternatively, the battery  15  is charged with the electric power generated by the electric motor  13  when the electric motor  13  generates electric power. 
         [0030]    The transmission  16  includes an automated mechanical/manual transmission (not shown in the drawings) that selects one of a plurality of gear ratios (change gear ratios) according to the shift instruction signal to shift gears from the hybrid ECU  18  in order to shift the change gear ratios and transmit the gear-shifted power of the engine  10  and/or of the electric motor  13  to the wheel  19 . Alternatively, the transmission  16  transmits the power from the wheel  19  to the electric motor  13 , for example, when the vehicle reduces the speed or runs on the downgrade. Note that the automated mechanical/manual transmission can also shift the gear position to a given gear number by the driver&#39;s hand operation of the shift unit  23 . 
         [0031]    The motor ECU  17  is a computer working in coordination with the engine ECU  11  according to the instructions from the hybrid ECU  18 , and controls the electric motor  13  by controlling the inverter  14 . For example, the motor ECU  17  includes a CPU, an ASIC, a microprocessor (micro-computer), a DSP, and the like, and internally has an operation unit, a memory, an I/O port, and the like. 
         [0032]    The hybrid ECU  18  is an example of a computer. For hybrid running, the hybrid ECU  18  obtains accelerator opening information, brake operation information, vehicle speed information, the gear position information obtained from the transmission  16 , and the engine rotational speed information obtained from the engine ECU  11  in order to refer to the information, control the clutch  12  and supply the shift instruction signal to shift gears in order to control the transmission  16 . For hybrid running, the hybrid ECU  18  further gives the instructions to the motor ECU  17  to control the electric motor  13  and the inverter  14  based on the obtained State of Charge (SOC) information on the battery  15  and other information, and gives the instruction to the engine ECU  11  to control the engine  10 . Further, once receiving a “clogging warning” sent from the post-processing device  20 , the hybrid ECU  18  gives instructions for implementing the process for “regeneration” to the engine ECU  11 , the clutch  12 , and the motor ECU  17 . For example, the hybrid ECU  18  includes a CPU, an ASIC, a microprocessor (micro-computer), a DSP, and the like, and internally has an operation unit, a memory, an I/O port, and the like. 
         [0033]    Note that a computer program to be executed by the hybrid ECU  18  can be installed on the hybrid ECU  18  that is a computer in advance by being stored in a non-volatile memory inside the hybrid ECU  18  in advance. 
         [0034]    The engine ECU  11 , the motor ECU  17 , and the hybrid ECU  18  are connected to each other, for example, through a bus complying with the standard of the Control Area Network (CAN) or the like. 
         [0035]    The wheel  19  is a drive wheel for transmitting the driving force to the road surface. Note that, although only a wheel  19  is illustrated in  FIG. 1 , the hybrid vehicle  1  actually includes a plurality of the wheels  19 . 
         [0036]    The post-processing device  20  is for cleaning up the exhaust gas from the engine  10  and sends the clogging warning of a filter (not illustrated in the drawings) to the hybrid ECU  18 . To prevent the filter from getting clogged, it is necessary to implement the process for “regeneration” with operating the engine  10  under high load when the filter almost gets clogged. Note that the clogging warning is the information warning that the filter can get clogged, so that the filter has not been clogged yet at the time when the clogging warning is sent. 
         [0037]    The exhaust braking electromagnetic valve  21  is positioned at an exhaust pipe of the engine  10  provided at the rear part of the post-processing device  20 . Closing the exhaust braking electromagnetic valve  21  increases the resistance generated when the exhaust gas is emitted outside. This increases the friction of the engine  10  and thus can increase the effect of the engine braking. In the present embodiment, the exhaust braking electromagnetic valve  21  is not used for increasing the effect of the engine braking but for increasing the load on the engine  10  in order to complete the “generation” in a short time. 
         [0038]    The key switch  22  is a switch that is turned ON/OFF, for example, by insertion of a key by the user at the start of drive. Turning ON the key switch activates each unit of the hybrid vehicle  1 , and turning OFF the key switch  22  stops each unit of the hybrid vehicle  1 . 
         [0039]      FIG. 2  is a block diagram for illustrating an exemplary configuration of a function implemented in the hybrid ECU  18  executing a computer program. In other words, when the hybrid ECU  18  executes a computer program, a post-processing device regeneration control unit  30  is implemented. 
         [0040]    Once receiving the clogging warning from the post-processing device  20 , the post-processing device regeneration control unit  30  sends instructions to each part in order to implement the process of the “regeneration”. 
         [0041]    Next, the process for a regeneration control of the post-processing device  20  implemented in the hybrid ECU  18  executing a computer program will be described with reference to the flowchart in  FIG. 3 . 
         [0042]    At the START in  FIG. 3 , the hybrid ECU  18  has executed a computer program and the post-processing device regeneration control unit  30  is implemented in the hybrid ECU  18 . Then, the process goes to step S 1 . Note that the fact that a value indicating the SOC of the battery  15  is equal to or less than a predetermined value can be added as a condition of the “START” because the regeneration for obtaining the regeneration torque equivalent to the engine braking cannot be performed in step S 5  if the value indicating the SOC of the battery  15  is high. 
         [0043]    In step S 1 , when the post-processing device regeneration control unit  30  receives the clogging warning from the post-processing device  20 , the process goes to step S 2 . 
         [0044]    In step S 2 , the post-processing device regeneration control unit  30  performs the “regeneration” and the process goes to step S 3 . 
         [0045]    In step S 3 , the post-processing device regeneration control unit  30  determines whether the hybrid vehicle  1  reduces the speed. When it is determined in step S 3  that the hybrid vehicle  1  reduces the speed, the process goes to step S 4 . On the other hand, when it is determined in step S 3  that the hybrid vehicle  1  does not reduce the speed, the process goes back to step S 2 . 
         [0046]    In step S 4 , the post-processing device regeneration control unit  30  disengages the clutch  12  and the process goes to step S 5 . 
         [0047]    In step S 5 , the post-processing device regeneration control unit  30  performs regeneration for obtaining regeneration torque generated by the electric motor  13  and equivalent to the engine braking. Then, the process goes to step S 6 . 
         [0048]    In step S 6 , the post-processing device regeneration control unit  30  determines whether to shorten the regeneration time. Note that the driver can set the shortening of the regeneration time from a setting unit (not illustrated in the drawings) in advance. When it is determined in step S 6  that the regeneration time is shortened, the process goes to step S 7 . On the other hand, when it is determined in step S 6  that it is not necessary to shorten the regeneration time, the process goes to step S 8 . 
         [0049]    In step S 7 , the post-processing device regeneration control unit  30  closes the exhaust braking electromagnetic valve  21  in order to use the exhaust brake with the engine braking and the process goes to step S 8 . 
         [0050]    In step S 8 , the post-processing device regeneration control unit  30  determines whether the clogging warning has been resolved. When it is determined in step S 8  that the clogging warning has been resolved, the process is terminated. On the other hand, when it is determined in step S 8  that the clogging warning has not been resolved yet, the process goes back to step S 2 . 
       [Effects] 
       [0051]    when decelerating in the duration of the regeneration of the post-processing device  20 , the hybrid vehicle  1  runs with the electric motor  13 , controls the engine  10  to maintain a rotational speed appropriate to the regeneration of the post-processing device  20  independently from the driving system, and generates braking force equivalent to the braking force of the engine braking by the regeneration of the electric motor  13 . Thus, the engine  10  can continue the high load operation appropriate to the “regeneration” independently from the driving system as long as necessary, so that the process for the “regeneration” can be completed in a short time and the fuel efficiency can be improved. 
         [0052]    Further, closing the exhaust braking electromagnetic valve  21  during the regeneration of the post-processing device  20  increases the load on the engine  10  more, and thus can complete the “regeneration” in a shorter time. As described above, completing the “regeneration” in a shorter time can improve the fuel efficiency. 
       Other Embodiment 
       [0053]    Although the clogging warning sent by the post-processing device  20  causes the post-processing device regeneration control unit  30  to implement the “regeneration” in the above-mentioned description of the embodiment, the “regeneration” can periodically be implemented once every predetermined travel distance or predetermined travel time without using such a clogging warning. 
         [0054]    Although the exhaust brake is used with the engine braking for the purpose of shortening the regeneration time in the above-mentioned embodiment, the exhaust braking can further be used with the engine braking for the purpose of regenerating the device with excessively accumulated particulate matter within a predetermined time. 
         [0055]    For example, once the post-processing device regeneration control unit  30  receives the clogging warning, regeneration is automatically implemented in the above-mentioned description of the embodiment. On the other hand, the vehicle can have a structure in which the clogging warning is notified also to the driver so that the driver can suspend the implementation of the regeneration. It seems that the driver suspends the implementation of the regeneration for the reason, for example, that the driver performs home delivery with the hybrid vehicle  1  in a quiet residential area and needs to reduce the noise of the regeneration from the engine  10 . 
         [0056]    In such a case, particulate matter is accumulated in the post-processing device  20  more than in the case in which a normal regeneration process is started. The exhaust braking can be used with the engine braking in order to complete burning off such particulate matter within a normal regeneration process time. 
         [0057]    However, it is preferable that the usage of the exhaust braking with the engine braking be not easily allowed because the usage causes the increase in the fuel consumption for the regeneration. For example, a threshold is set for the excess of accumulated particulate matter over the amount of accumulated particulate matter enough to start a normal regeneration so that the exhaust braking is used with the engine braking when the excess exceeds the threshold. 
         [0058]    Further, a threshold is provided for the value indicating the SOC of the battery  15  so that the post-processing device regeneration control unit  30  can control the regeneration process. For example, two-stage thresholds B&lt;A are provided for the value indicating the SOC. The threshold A is the upper limit of the value indicating the SOC. The threshold B is a value smaller than threshold A and in which the value indicating the SOC of the battery  15  reaches the threshold A in a relatively short time once a regenerative charge is performed. When the value indicating the SOC is equal to or more than the threshold A in that case, the regenerative charge cannot be performed any more. Thus, the regeneration is halted and the clutch  12  is engaged in order to perform a usual control. Further, if the value indicating the SOC is equal to or more than the threshold B and less than the threshold A, it is highly possible that the value indicating the SOC could reach the threshold A a short time later although the process currently goes without a problem. Thus, Yes is selected in step S 6  of the flowchart in  FIG. 3  in order to perform a control in step S 7  to shorten the regeneration time by using the exhaust braking with the engine braking. This enables the regeneration using the engine braking before the regenerative braking cannot be performed, and thus can reduce the usage of a service brake. Further, when the value indicating the SOC is less than the threshold B, the control as described in the flowchart of  FIG. 3  is performed. 
         [0059]    Although the engine  10  has been described as an internal combustion engine, the engine  10  can also be a heat engine including an external combustion engine. 
         [0060]    Further, while the computer program executed by the hybrid ECU  18  is installed on the hybrid ECU  18  in advance in the above-mentioned descriptions, the computer program can be installed on the hybrid ECU  18  as a computer by attaching removable media recording the computer program (storing the program), for example, to a drive (not shown in the drawings) and storing the computer program read from the removable media in a non-volatile memory inside the hybrid ECU  18  or receiving, with a communication unit (not shown in the drawings), a computer program transmitted through a wired or wireless transmission medium and storing the computer program in a non-volatile memory inside the hybrid ECU  18 . 
         [0061]    Further, each ECU can be implemented by an ECU combining some or all of the functions of the ECUs. Alternatively, an ECU can newly be provided by the further subdivision of the function of each ECU. 
         [0062]    Note that the computer program executed by the computer can be for performing the process in chronological order according to the order described herein or can be for performing the process in parallel or at the necessary timing, for example, when the computer program is invoked. 
         [0063]    Further, the embodiments of the present invention are not limited to the above-mentioned embodiment, and can variously be modified without departing from the gist of the invention.