Patent Publication Number: US-8983700-B2

Title: Drive control device of hybrid vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to a drive control device of a hybrid vehicle that includes a plurality of power sources, combines the power thereof using a differential gear mechanism, and inputs or outputs the power to or from a driving shaft, and more particularly, to a drive control device of a hybrid vehicle that controls the engine operating point of an internal combustion engine and the torque of a motor generator. 
     BACKGROUND ART 
     Conventionally, as a form of a hybrid vehicle including an electric motor and an internal combustion engine other than a serial form and a parallel form, as disclosed in U.S. Pat. Nos. 3,050,125, 3,050,138, 3,050,141, 3,097,572, and the like, there is a form in which the torque of the power of the internal combustion engine is converted by dividing the power of the internal combustion engine to a power generator and a driving shaft using one planetary gear mechanism (a differential gear mechanism having three rotating components) and two electric motors and driving an electric motor arranged at the driving shaft by using electric power generated by the power generator. This will be referred to as a “three-axis type”. 
     According to this conventional technology, the engine operating point of the internal combustion engine can set to an arbitrary point including stop, and accordingly, the fuel efficiency can be improved. However, although not as much as for the serial form, since an electric motor having relatively high torque is necessary for acquiring sufficient driving-shaft torque, and the amount of transmission and reception of power between the power generator and the electric motor increases in a low gear ratio region, the electric loss increases, and there is still a room for improvement. 
     As methods for solving this point, there are methods disclosed in U.S. Pat. No. 3,578,451 and Japanese Patent Application Laid-Open (JP-A) No. 2004-15982, and JP-A Nos. 2002-281607 and 2008-12992 applied by the applicants of the present invention. 
     In the method disclosed in JP-A No. 2002-281607, a driving shaft connected to an output shaft of an internal combustion engine, a first motor generator (hereinafter, referred to as “MG1”), a second motor generator (hereinafter, referred to as “MG2”), and a drive wheel is connected to each rotating component of a differential gear mechanism having four rotating components, the power of the internal combustion engine and the power of the MG1 and MG2 are combined, and the combined power is output to the driving shaft. 
     In addition, in the method disclosed in JP-A No. 2002-281607, by arranging an output shaft of an internal combustion engine and a drive shaft connected to a drive wheel in a rotating component arranged on the inner side on an alignment chart and arranging the MG1 (the internal combustion engine side) and MG2 (the driving shaft side) in a rotating component disposed on the outer side on the alignment chart, the ratio of power that is in charge of the MG1 and MG2 to the power delivered to the driving shaft from the internal combustion engine can decrease, whereby the MG1 and MG2 can be miniaturized, and the transmission efficiency of the driving device can be improved. This will be referred to as a “four-axis type”. 
     In addition, a method disclosed in U.S. Pat. No. 3,578,451 similar to the above-described method has been proposed, in which an additional fifth rotating component is included, and a brake stopping this rotating component is arranged. 
     In JP-A No. 2008-12992, in a drive control device of a hybrid vehicle including an internal combustion engine and a plurality of motor generators, a technology for controlling the internal combustion engine has been disclosed in which the engine rotation speed is set high at the operating point of the internal combustion engine. 
     In the above-described conventional technology, as disclosed in U.S. Pat. No. 3,050,125, the power to be output by the internal combustion engine is calculated by adding the driving force required for the vehicle and the electric power required for charging a battery, and, out of a combination of the engine torque and the engine rotation speed corresponding to the power, a point at which the efficiency is high as possibly as can is calculated and is set as a target engine operating point. Then, the engine rotation speed is controlled by controlling the MG1 such that the engine operating point of the internal combustion engine becomes the target operating point. 
     CITATION LIST 
     Patent Literature 
     
         
         [PTL 1] U.S. Pat. No. 3,050,125 
         [PTL 2] U.S. Pat. No. 3,050,138 
         [PTL 3] U.S. Pat. No. 3,050,141 
         [PTL 4] U.S. Pat. No. 3,097,572 
         [PTL 5] U.S. Pat. No. 3,578,451 
         [PTL 6] JP-A No. 2004-15982 
         [PTL 7] JP-A No. 2002-281607 
         [PTL 8] JP-A No. 2008-12992 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in a conventional drive control device of a hybrid vehicle, in the case of the “three-axis type”, the torque of the MG2 does not have an effect on the torque balance. Accordingly, torque output from the driving shaft by the internal combustion engine and the MG1 is calculated based on the torque of the MG1 wherein the torque of the MG1 is feedback-controlled so as to allow the engine rotation speed to approach a target value, and the torque of the MG2 is controlled so as to have a value acquired by subtracting the calculated value from a target driving force, whereby the target driving force can be output from the driving shaft even in a case where the engine torque changes. 
     However, in the case of the “four-axis type”, the driving shaft and the MG2 form mutually-different shafts, and the torque of the MG2 influences the torque balance so as to have an effect on the control of the engine rotation speed, and accordingly, there is a disadvantage that the control method of the “three-axis” type cannot be used. 
     In addition, in JP-A No. 2004-15982, which is the case of the “four-axis type”, a method for controlling the engine rotation speed and the driving force has been disclosed in which the torques of the MG1 and the MG2 in a case of driving without charging or discharging a battery are calculated using a torque balance equation, and the feedback control of the rotation speeds of the MG1 and MG2 is performed. 
     However, in JP-A No. 2004-15982 described above, a case where the battery is charged or discharged and a case where the engine torque changes have not been mentioned. 
     In JP-A No. 2008-12992 described above, while the technology for controlling an internal combustion engine has been disclosed in which the engine rotation speed is set high at the operating point of the internal combustion engine, the control of a plurality of motor generators is not clear, and the control of a plurality of motor generators in a case where the battery is charged and discharged is not clear. 
     In JP-A No. 2008-12992 described above, the internal combustion engine and a plurality of motor generators are mechanically operated to be connected to each other, and it is necessary to perform control with the plurality of motor generators being associated with each other so as to balance the torque thereof while the operating point of the internal combustion engine is maintained at a target value, and, in a case where the battery is charged and discharged, the electric power needs to be balanced. In other words, it is necessary to perform control such that both the torque of the plurality of motor generators and the electric power are balanced. 
     In addition, as disclosed in JP-A No. 2008-12992 described above, while the control is performed with the electric power being balanced, the electric power of the battery may be set to be used by limiting the power generation according to the driving the internal combustion engine. By forming the charge state SOC of the battery to be a predetermined (range) state while the electric power of the battery is more positively used, the breadth of the control is secured, whereby the efficiency of the whole system can be improved. 
     However, as disclosed in JP-A No. 2008-12992 described above, when uniform control is performed in which target engine power is determined based only on the target driving power and the target charged/discharged power that are based on a map or a table, there is a problem in that it is difficult to have the breath of the control. 
     Objects of the present invention are to set up control of a plurality of motor generators in a case where a battery is charged or discharged, to secure both a target driving force and target charging/discharging in consideration of an operating point of an internal combustion engine, and to have the breath of control of using the electric power of the battery under a more specific condition in a drive control device of a hybrid vehicle including the internal combustion engine and the plurality of motor generators. 
     Solution to Problem 
     According to the present invention, there is provided a drive control device of a hybrid vehicle that controls driving of the vehicle using outputs of an internal combustion engine and a plurality of motor generators, the drive control device including: an accelerator opening degree detecting means that detects the accelerator opening degree; a vehicle speed detecting means that detects a vehicle speed; a battery charge state detecting means that detects a charge state of a battery; a target driving power setting means that sets target driving power based on the accelerator opening degree that is detected by the accelerator opening degree detecting means and the vehicle speed detected by the vehicle speed detecting means; a target charge/discharge power setting means that sets target charge/discharge power based on at least the charge state of the battery that is detected by the battery charge state detecting means; a target engine power calculating means that calculates target engine power from the target driving power setting means and the target charge/discharge power setting means; a target engine operating point setting means that sets a target engine operating point based on the target engine power and total system efficiency; and a motor torque instruction value calculating means that sets torque instruction values of the plurality of motor generators, wherein the target driving power setting means sets driving power corresponding to a state in which power assistance depending on electric power of the battery is received as a maximal value of the target driving power in advance, the target engine power calculating means sets a maximal value of the target engine power corresponding to a maximal output that can be output by the internal combustion engine in advance, compares the target engine power and the maximal value of the target engine power calculated by the target driving power setting means and the target charge/discharge power setting means with each other, and updates the target engine power with a smaller value thereof, a target electric power calculating means calculating target electric power that is a target value of input/output electric power for the battery based on a difference between the target driving power and the target engine power is arranged, and the motor torque instruction value calculating means calculates torque instruction values of the plurality of motor generators by using a torque balance equation including target engine torque required at the target engine operating point and an electric power balance equation including the target electric power. 
     Advantageous Effects of Invention 
     According to the present invention, the charge state of a battery can be formed within a predetermined range while the engine operating point is controlled so as to match a target value, and a power assistance region in which the electric power of the battery is used can be arranged. 
     According to the present invention, driving using the electric power of the battery can be performed using the power assistance region in accordance with a driver&#39;s request. 
     In addition, according to the present invention, the control of a plurality of motor generators in a case where the battery is charged and discharged can be performed. 
     According to the present invention, both a target driving force and target charging/discharging can be secured in consideration of an engine operating point of an internal combustion engine. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a system configuration diagram of a drive control device of a hybrid vehicle. 
         FIG. 2  is a control block diagram of calculating a target engine operating point and target electric power. 
         FIG. 3  is a control block diagram of calculating a torque instruction value of a motor generator. 
         FIG. 4  is a control flow chart of calculating a target engine operating point. 
         FIG. 5  is a control flowchart of calculating a torque instruction value of a motor generator. 
         FIG. 6  is a target driving force search map according to a vehicle speed and the accelerator opening degree. 
         FIG. 7  is a target charging/discharging power search table according to the charge state of a battery. 
         FIG. 8  is a target engine operating point search map according to engine torque and an engine rotation speed. 
         FIG. 9  is an alignment chart in a case where the vehicle speed is changed at the same engine operating point. 
         FIG. 10  is a diagram that illustrates a line of the highest engine efficiency and a line of the highest total efficiency in a target engine operating point search map formed by engine torque and an engine rotation speed. 
         FIG. 11  is a diagram that illustrates the efficiency on a power line formed by efficiency and an engine rotation speed. 
         FIG. 12  is an alignment chart of points (D, E, and F) on an equi-power line. 
         FIG. 13  is an alignment chart of the state of a low gear ratio. 
         FIG. 14  is an alignment chart of the state of an intermediate gear ratio. 
         FIG. 15  is an alignment chart of the state of a high gear ratio. 
         FIG. 16  is an alignment chart of the state in which power circulation occurs. 
     
    
    
     DESCRIPTION EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 
     Embodiments 
       FIGS. 1 to 16  illustrate an embodiment of the present invention. In  FIG. 1 , reference numeral  1  represents a drive control device of a hybrid vehicle. The drive control device  1  of the hybrid vehicle, as a driving system, includes: an output shaft  3  of an internal combustion engine  2  that generates a driving force in accordance with combustion of fuel; a first motor generator  4  and a second motor generator  5  that generate a driving force using electricity and generate electrical energy through driving; a driving shaft  7  that is connected to a drive wheel  6  of the hybrid vehicle, and a differential gear mechanism  8  that is a power transmission system connected to the output shaft  3 , the first and second motor generators  4  and  5 , and the driving shaft  7 . 
     The internal combustion engine  2  includes: an air content adjusting means  9  such as a throttle valve that adjusts the air volume to be suctioned in accordance with the accelerator opening degree (the amount of pressing an accelerator pedal using a foot); a fuel supplying means  10  such as a fuel injection valve that supplies fuel corresponding to the suctioned air volume; and an ignition means  11  such as an ignition device that ignites the fuel. In the internal combustion engine  2 , the combustion state of the fuel is controlled by the air content adjusting means  9 , the fuel supplying means  10 , and the ignition means  11 , and a driving force is generated by the combustion of the fuel. 
     The first motor generator  4  includes: a first motor rotor shaft  12 ; a first motor rotor  13 ; and a first motor stator  14 . The second motor generator  5  includes: a second motor rotor shaft  15 ; a second motor rotor  16 ; and a second motor stator  17 . The first motor stator  14  of the first motor generator  4  is connected to a first inverter  18 . The second motor stator  17  of the second motor generator  5  is connected to a second inverter  19 . 
     The power terminals of the first and second inverters  18  and  19  are connected to a battery  20 . The battery  20  is an electricity accumulating means that can exchange electric power between the first motor generator  4  and the second motor generator  5 . The first motor generator  4  and the second motor generator  5  generate driving forces in accordance with electricity of which the amount of electricity supplied from the battery  20  is controlled by the first and second inverters  18  and  19  and generate electrical energy using the driving force supplied from the drive wheel  6  at the time of regeneration and store the generated electrical energy in the battery  20  to be charged. 
     The differential gear mechanism  8  includes a first planetary gear mechanism  21  and a second planetary gear mechanism  22 . The first planetary gear mechanism  21  includes: a first sun gear  23 ; a first planetary carrier  25  supporting a first planetary gear  24  engaged with the first sun gear  23 ; and a first ring gear  26  that is engaged with the first planetary gear  24 . The second planetary gear mechanism  22  includes: a second sun gear  27 ; a first planetary carrier  29  supporting a second planetary gear  28  engaged with the second sun gear  27 ; and a second ring gear  30  that is engaged with the second planetary gear  28 . 
     The differential gear mechanism  8  arranges the rotational center lines of rotating components of the first planetary gear mechanism  21  and the second planetary gear mechanism  22  on a same axis, arranges the first motor generator  4  between the internal combustion engine  2  and the first planetary gear mechanism  21 , and arranges the second motor generator  5  on a side of the second planetary gear mechanism  22  that is separated away from the internal combustion engine  2 . The second motor generator  5  has performance capable of driving the vehicle using only the output thereof. 
     The first motor rotor shaft  12  of the first motor generator  4  is connected to the first sun gear  23  of the first planetary gear mechanism  21 . The first planetary carrier  25  of the first planetary gear mechanism  21  and the second sun gear  27  of the second planetary gear mechanism  22  are connected to the output shaft  3  of the internal combustion engine  2  in a combined manner through a one-way clutch  31 . The first ring gear  26  of the first planetary gear mechanism  21  and the second planetary carrier  29  of the second planetary gear mechanism  22  are combined and are connected to an output unit  32 . The output unit  32  is connected to the driving shaft  7  through an output transmission mechanism  33  such as a gear or a chain. The second motor rotor shaft  15  of the second motor generator  5  is connected to the second ring gear  30  of the second planetary gear mechanism  9 . 
     The one-way clutch  31  is a mechanism that fixes the output shaft  3  of the internal combustion engine  2  so as to rotate only in the output direction and prevents the output shaft  3  of the internal combustion engine  2  from reversely rotating. The driving power of the first motor generator  4  is transmitted as driving power of the output unit  32  through a reaction force of the one-way clutch  31 . 
     The hybrid vehicle outputs the power generated by the internal combustion engine  2  and the first and second motor generators  4  and  5  to the driving shaft  7  through the first and second planetary gear mechanisms  21  and  21 , thereby driving the drive wheel  6 . In addition, the hybrid vehicle transmits the driving force delivered from the drive wheel  6  to the first and second motor generators  4  and  5  through the first and second planetary gear mechanisms  21  and  22 , thereby generating electrical energy so as to charge the battery  20 . 
     The differential gear mechanism  8  sets four rotating components  34  to  37 . The first rotating component  34  is formed by the first sun gear  23  of the first planetary gear mechanism  21 . The second rotating component  35  is formed by combining the first planetary carrier  25  of the first planetary gear mechanism  21  and the second sun gear  27  of the second planetary gear mechanism  22 . The third rotating component  36  is formed by combining the first ring gear  26  of the first planetary gear mechanism  21  and the second planetary carrier  29  of the second planetary gear mechanism  22 . The fourth rotating component  37  is formed by the second ring gear  30  of the second planetary gear mechanism  22 . 
     The differential gear mechanism  8 , as illustrated in  FIGS. 9 and 12  to  16 , on an alignment chart in which the rotation speeds of four rotating components  31  to  34  can be represented as a straight line, sets the four rotating components  34  to  37  as the first rotating component  34 , the second rotating component  35 , the third rotating component  36 , and the fourth rotating component  37  from one end (the left side in each figure) toward the other end (the right side in each figure). A ratio of distances among the four rotating components  34  to  37  is represented as k1:1:k2. In each figure, MG1 represents the first motor generator  4 , MG2 represents the second motor generator  5 , ENG represents the internal combustion engine  2 , and OUT represents the output unit  32 . 
     The first motor rotor shaft  12  of the first motor generator  4  is connected to the first rotating component  34 . The output shaft  3  of the internal combustion engine  2  is connected to the second rotating component  35  through the one-way clutch  31 . The output unit  32  is connected to the third rotating component  36 . The driving shaft  7  is connected to the output unit  32  through the output transmission mechanism  33 . The second motor rotor shaft  15  of the second motor generator  5  is connected to the fourth rotating component  37 . 
     From this, the differential gear mechanism  8  includes the four rotating components  34  to  37  connected to the output shaft  3 , the first motor generator  4 , the second motor generator  5 , and the driving shaft  7  and transmits power and receives power to/from the output shaft  3  of the internal combustion engine  2 , the first motor generator  4 , the second motor generator  5 , and the driving shaft  7 . Accordingly, the drive control device  1  employs the control form of the “four-axis type”. 
     The hybrid vehicle  1  connects the air content adjusting means  9 , the fuel supplying means  10 , the ignition means  11 , the first inverter  18 , and the second inverter  19  to the drive control unit  38 . In addition, an accelerator opening degree detecting means  39 , a vehicle speed detecting means  40 , an engine rotation speed detecting means  41 , and a battery charge state detecting means  42  are connected to the drive control unit  38 . 
     The accelerator opening degree detecting means  39  detects the accelerator opening degree that is the amount of pressing the accelerator pedal using a foot. The vehicle speed detecting means  40  detects a vehicle speed (car speed) of the hybrid vehicle. The engine rotation number detecting means  41  detects the engine rotation speed of the internal combustion engine  2 . The battery charge state detecting means  42  detects the charge state SOC of the battery  20 . 
     In addition, the drive control unit  38  includes: a target driving force setting means  43 ; a target driving power setting means  44 ; a target charge/discharge power setting means  45 ; a target engine power calculating means  46 ; a target engine operating point setting means  47 ; a target electric power setting means  48 ; and a motor torque instruction value calculating means  49 . 
     The target driving force setting means  43 , as illustrated in  FIG. 2 , searches a target driving force search map illustrated in  FIG. 6  for the target driving force used for driving the hybrid vehicle in accordance with the accelerator opening degree detected by the accelerator opening degree detecting means  39  and the vehicle speed detected by the vehicle speed detecting means  40  and determines the target driving force. The target driving force is set to a negative value so as to be a driving force in a deceleration direction corresponding to engine brake in a high vehicle speed region at the accelerator opening degree=0 and is set to a positive value for creep driving in a low vehicle speed region. 
     The target driving power setting means  44  sets target driving power based on the accelerator opening degree detected by the accelerator opening degree detecting means  39  and the vehicle speed detected by the vehicle speed detecting means  40 . Then, the target driving power setting means  44  is set in advance such that the driving power corresponding to a state in which power assistance depending on the electric power of the battery  20  is received is a maximal value of the target driving power. In this embodiment, as illustrated in  FIG. 2 , target driving power required for driving the hybrid vehicle at the target driving force is set by multiplying the target driving force set by the target driving force setting means  43  by the vehicle speed. 
     The target charge/discharge power setting means  45  sets target charge/discharge power based on at least the charge state SOC of the battery  20  that is detected by the battery charge state detecting means  42 . In this embodiment, target charge/discharge power is searched from a target charge/discharge power search table illustrated in  FIG. 7  in accordance with the charge state SOC of the battery  20  and the vehicle speed and is set. The target charge/discharge power is set such that the absolute value thereof decreases as the vehicle speed is lowered. 
     The target engine power calculating means  46 , as illustrated in  FIG. 2 , calculates target engine power based on the target driving power set by the target driving power setting means  44  and the target charge/discharge power set by the target charge/discharge power setting means  45 . In this embodiment, by subtracting the target charge/discharge power from the target driving power, the target engine power is acquired. 
     The target engine operating point setting means  47  sets a target engine operating point (a target engine rotation speed and target engine torque) based on the target engine power and the efficiency of the whole system of the drive control device  1 . In this embodiment, the target engine operating point is searched from a target engine operating point search map illustrated in  FIG. 8  in consideration of the vehicle speed. 
     The target electric power setting means  48  sets target electric power that is a target value of the input/output electric power from the battery  20  based on the target driving power set by the target driving power setting means  44  and the target engine power set by the target engine power calculating means  46 . 
     The motor torque instruction value calculating means  49  sets torque instruction values of the first and second motor generators  4  and  5 . 
     The torque instruction value of the first motor generator  4  and the torque instruction value of the second motor generator  5  set by the motor torque instruction value calculating means  49 , as illustrated in  FIG. 3 , are calculated by first to seventh calculation units  50  to  56 . In  FIG. 3 , MG1 represents the first motor generator  4 , and MG2 represents the second motor generator  5 . 
     The first calculation unit  50  calculates a target rotation speed Nmg1t of the first motor generator  4  and a target rotation speed Nmg2t of the second motor generator  5  in a case where the engine rotation speed is the target engine rotation speed based on the target engine rotation speed set by the target engine operating point setting means  47  and the vehicle speed detected by the vehicle speed detecting means  40 . 
     The second calculation unit  51  calculates basic torque Tmg1i of the first motor generator  4  based on the target rotation speed Nmg1t of the first motor generator  4  and the target rotation speed Nmg2t of the second motor generator  5 , which are calculated by the first calculation unit  50 , the target electric power set by the target electric power setting means  48 , and the target engine torque set by the target engine operating point setting means  47 . 
     The third calculation unit  52  calculates basic torque Tmg2i of the second motor generator  6  based on the basic torque Tmg1i of the first motor generator  4  that is calculated by the second calculation unit  51  and the target engine torque set by the target engine operating point setting means  47 . 
     The fourth calculation unit  53  calculates feedback correction torque Tmg1fb of the first motor generator  4  based on the engine rotation speed detected by the engine rotation speed detecting means  41  and the target engine rotation speed set by the target engine operating point setting means  47 . 
     The fifth calculation unit  54  calculates feedback correction torque Tmg2fb of the second motor generator  5  based on the engine rotation speed detected by the engine rotation speed detecting means  41  and the target engine rotation speed set by the target engine operating point setting means  47 . 
     The sixth calculation unit  55  calculates a torque instruction value Tmg1 of the first motor generator  4  based on the basic torque Tmg1i of the first motor generator  4  that is calculated by the second calculation unit  51  and the feedback correction torque Tmg1fb of the first motor generator  4  that is calculated by the fourth calculation unit  53 . 
     The seventh calculation unit  56  calculates a torque instruction value Tmg2 of the second motor generator  6  based on the basic torque Tmg2i of the second motor generator  5  that is calculated by the third calculation unit  52  and the feedback correction torque Tmg2fb of the second motor generator  5  that is calculated by the fifth calculation unit  54 . 
     The drive control device  1  of the hybrid vehicle performs control of the drive states of the air content adjusting means  9 , the fuel supplying means  10 , and the ignition means  11  such that the internal combustion engine  2  operates at the target engine operating point (the target engine rotation speed and the target engine torque) set by the target engine operating point setting means  47  by using the drive control unit  38 . In addition, the drive control unit  38  performs control of the drive states of the first and second motor generators  4  and  5  using the torque instruction values set by the motor torque instruction value calculating means  49  such that the charge state (SOC) of the battery  20  is the target electric power set by the target electric power setting means  48 . 
     The drive control device  1  of the hybrid vehicle, as illustrated in the flowchart of controlling the calculation of the target engine operating point represented in  FIG. 4 , calculates a target engine operating point (the target engine rotation speed and the target engine torque) based on the amount of a driver&#39;s operation of the accelerator and the vehicle speed and, as illustrated in the flowchart of controlling the calculation of the motor torque instruction value represented in  FIG. 5 , calculates torque instruction values of the first and second motor generators  4  and  5  based on the target engine operating point. 
     In the calculation of the target engine operating point, as illustrated in  FIG. 4 , when the control program starts ( 100 ), various signals of the accelerator opening degree detected by the accelerator opening degree detecting means  39 , the vehicle speed detected by the vehicle speed detecting means  40 , the engine rotation speed detected by the engine rotation speed detecting means  41 , and the charge state SOC of the battery  20  detected by the battery charge state detecting means  42  are acquired ( 101 ) and a target driving force is calculated based on the target driving force detection map (see  FIG. 6 ) ( 102 ). 
     The target driving force is set to a negative value so as to be a driving force in a deceleration direction corresponding to engine brake in a high vehicle speed region at the accelerator opening degree=0 and is set to a positive value for creep driving in a low vehicle speed region. 
     Next, target driving power required for driving the hybrid vehicle with the target driving force is calculated by multiplying the target driving force calculated in Step  102  by the vehicle speed ( 103 ) and target charge/discharge power is calculated based on the target charge/discharge power search table (see  FIG. 7 ) ( 104 ). 
     In Step  103 , target driving power is set such that the driving power corresponding to a state in which power assistance depending on the electric power of the battery  20  is received is a maximal value of the target driving power. 
     In Step  104 , in order to control the charge state SOC of the battery  20  in a normal use range, a target charge/discharge amount is calculated based on the target charge/discharge power search table illustrated in  FIG. 7 . In a case where the charge state SOC of the battery  20  is low, the target charge/discharge power is increased on the charge side so as to prevent excessive discharge of the battery  20 . In a case where the charge state SOC of the battery  20  is high, the target charge/discharge power is increased on the discharge side so as to prevent excessive charge. The target charge/discharge power, for the convenience of description, the discharge side is set as a positive value, and the charge side is set as a negative value. 
     In addition, target engine power to be output by the internal combustion engine  2  is calculated based on the target driving power and the target charge/discharge power ( 105 ). The power to be output by the internal combustion engine  2  has a value acquired by adding (subtracting in the case of discharge) the power required for charging the battery  20  to the power required for driving the hybrid vehicle. Here, since the charge side is handled as a negative value, the target engine power is calculated by subtracting the target charge/discharge power from the target driving power. 
     Next, it is determined whether the target engine power calculated in Step  105  exceeds an upper limit value ( 106 ). In the case of “Yes” in the determination ( 106 ), the target engine power is replaced by the upper limit value ( 107 ), and the process proceeds to Step  108 . In the case of “No” in the determination ( 106 ), the process proceeds to Step  108 . In Steps  106  and  107 , restriction according to the upper limit value of the target engine power is performed. The upper limit value is a maximal value of the output that can be output by the internal combustion engine  2 . 
     In Step  108 , target power is calculated by subtracting the target engine power from the target driving power. In a case where the target driving power is higher than the target engine power, the target electric power has a value representing assistance power according to the electric power of the battery  20 . In addition, in a case where the target engine power is higher than the target driving power, the target electric power has a value representing charging electric power for the battery  20 . 
     After the target electric power is calculated in Step  108 , a target engine operating point (the target engine rotation speed and the target engine torque) corresponding to the vehicle speed is calculated based on the target engine operating point search map illustrated in  FIG. 8  ( 109 ), and the process is returned ( 110 ). 
     The target engine operating point search map ( FIG. 8 ) selects points at which the total efficiency acquired by adding the efficiency of the power transmission system configured by the differential gear mechanism  8  and the first and second motor generators  4  and  5  to the efficiency of the internal combustion engine  2  is high on the equi-power line for each power level and sets a line acquired by joining the points as a target engine operating point line. Each target engine operating point line is set for each vehicle speed (40 km/h, 80 km/h, and 120 km/h in  FIG. 8 ). The set value of the target engine operating point line may be acquired through an experiment or may be acquired through a calculation that is based on the efficiency of the internal combustion engine  2  and the first and second motor generators  4  and  5 . In addition, the target engine operating point line is set to move to the high rotation side as the vehicle speed increases. 
     The reason for this is as follows. 
     In a case where the same engine operating point is set as the target engine operating point regardless of the vehicle speed, as illustrated in  FIG. 9 , the rotation speed of the first motor generator  4  is positive in a case where the vehicle speed is low, and the first motor generator  4  serves as a power generator, and the second motor generator  5  serves as an electric motor (A). Then, as the vehicle speed increases, the rotation speed of the first motor generator  4  approaches zero (B), and, when the vehicle speed further increases, the rotation speed of the first motor generator  4  becomes negative. In this state, the first motor generator  4  operates as an electric motor, and the second motor generator  5  operates as a power generator (C). 
     In a case where the vehicle speed is low (states A and B), since the circulation of the power does not occur, and the target engine operating point, like the target engine operating point line of the vehicle speed=40 km/h illustrated in  FIG. 8 , is close to a point at which the efficiency of the internal combustion engine  2  is high on the whole. 
     However, in a case where the vehicle speed is high (state C), the first motor generator  4  operates as an electric motor, the second motor generator  5  operates as a power generator, and accordingly, the circulation of the power occurs, whereby the efficiency of the power transmission system is lowered. Accordingly, as illustrated at a point C illustrated in  FIG. 11 , the efficiency of the power transmission system is lowered even when the efficiency of the internal combustion engine  2  is high, and accordingly, the total efficiency is lowered. 
     Thus, in order not to cause the circulation of power to occur in the high vehicle speed region, like E in the alignment chart illustrated in  FIG. 12 , the rotation speed of the first motor generator  4  may be set to zero or higher. However, in such a case, the engine operating point of the internal combustion engine  2  moves in a direction in which the engine rotation speed of the internal combustion engine  2  increases. Thus, as illustrated in point E illustrated in  FIG. 11 , even when the efficiency of the power transmission system is high, the efficiency of the internal combustion engine  2  is lowered much, whereby the total efficiency is lowered. 
     Accordingly, as illustrated in  FIG. 11 , a point at which the total efficiency is high is D therebetween, and, by setting this point as the target engine operating point, an operation having the highest efficiency can be performed. 
     As above, in  FIG. 10 , three engine operating points C, D, and E are represented on the target engine operating point search map. It can be understood that an operating point at which the total efficiency is the highest moves to a further high rotation side than an operating point at which the engine efficiency is the highest in a case where the vehicle speed is high. 
     Next, the calculation of torque instruction values that are the target torque of the first motor generator  4  and the target torque of the second motor generator  5  used for setting the amount of charge/discharge of the battery  20  as a target value while the target driving force is output will be described along the flowchart of controlling the calculation of the motor torque instruction values illustrated in  FIG. 5 . In  FIG. 5 , MG1 represents the first motor generator  4 , and MG2 represents the second motor generator  5 . 
     In the calculation of the motor torque instruction values, as illustrated in  FIG. 5 , when a control program starts ( 200 ), first, in Step  201 , the driving shaft rotation speed No of the driving shaft  7  to which the first and second planetary gear mechanisms  21  and  22  are connected is calculated based on the vehicle speed. Next, the rotation speed Nmg1t of the first motor generator  4  and the rotation speed Nmg2t of the second motor generator  5  in a case where the engine rotation speed Ne is the target engine rotation speed Net set by the target engine operating point setting means  47  are calculated by using the following Equations (1) and (2). These Equations (1) and (2) for the calculation are acquired based on the relation between the rotation speeds of the first and second planetary gear mechanisms  21  and  22 .
 
 Nmg 1 t =( Net−No )* k 1 +Net   Equation (1)
 
 Nmg 2 t =( No−Net )* k 2 +No   Equation (2)
 
     Here, k1 and k2, as will be described later, are values that are determined based on the gear ratio between the first and second planetary gear mechanisms  21  and  22 . 
     Next, in Step  202 , basic torque Tmg1i of the first motor generator  4  is calculated by using the following Equation (3) based on the rotation speed Nmg1t of the first motor generator  4  and the rotation speed Nmg2t of the second motor generator  5 , which have been acquired in Step  201 , and the target electric power Pbatt′ set by the target electric power setting means  48  and the target engine torque Tet set by the target engine operating point setting means  47 .
 
 Tmg 1 i =( Pbatt′* 60/2 π−Nmg 2 t*Tet/k 2)/( Nmg 1 t+Nmg 2 t *(1 +k 1)/ k 2)  Equation (3)
 
     This Equation (3) for the calculation can be derived by solving certain simultaneous equations from a torque balance equation (4) representing the balance of torques input to the first and second planetary gear mechanisms  21  and  22  and an electric power balance equation (5) representing that the electric power generated or consumed by the first and second motor generators  4  and  5  and the input/output electric power (Pbatt′) for the battery  20  are the same.
 
 Tet +(1 +k 1)* Tmg 1 =k 2 *Tmg 2  Equation (4)
 
 Nmg 1 *Tmg 1*2π/60 +Nmg 2 *Tmg 2*2π/60 =Pbatt′   Equation (5)
 
     Next, in Step  203 , the basic torque Tmg2i of the second motor generator  5  is calculated by using the following Equation (6) based on the basic torque Tmg1i of the first motor generator  4  and the target engine torque Tet.
 
 Tmg 2 i =( Tet +(1 +k 1)* Tmg 1 i )/ k 2  Equation (6)
 
     This equation is derived from Equation (4) described above. 
     Next, in Step  204 , in order to make the engine rotation speed approach the target, the feedback correction torque Tmg1fb of the first motor generator  4  and the feedback correction torque Tmg2fb of the second motor generator  5  are calculated by multiplying the deviation of the engine rotation speed Ne from the target engine rotation speed Net by a predetermined feedback gain set in advance. 
     In Step  205 , torque instruction values Tmg1 and Tmg2 that are control instruction values of the first and second motor generators  4  and  5  are calculated by adding the feedback correction torques Tmg1fb and Tmg2fb of the first and second motor generators  4  and  5  to the basic torques Tmg1i and Tmg2i, and the process is returned ( 206 ). 
     The drive control unit  38  controls the first and second motor generators  4  and  5  in accordance with the torque instruction values Tmg1 and Tmg2, whereby the amount of charge/discharge for the battery  20  can be the target value while the target driving force is output. 
       FIGS. 13 to 16  illustrate alignment charts in representative operation states. In the alignment charts, four rotating components  34  to  37  of the differential gear mechanism  8  formed by the first and second planetary gear mechanisms  21  and  22  are aligned in order of the first rotating component  34  connected to the first motor generator  4  (MG1), the second rotating component  35  connected to the internal combustion engine  2  (ENG), the third rotating component  36  connected to the driving shaft  7  (OUT), and the fourth rotating component  37  connected to the second motor generator  5  (MG2) in the alignment chart, and the mutual lever ratio among the rotating components  34  to  37  is arranged to be k1:1:k2 in the same order. 
     Here, values k1 and k2 determined based on the gear ratio of the differential gear mechanism  8  formed by the first and second planetary gear mechanisms  21  and  22  are defined as below.
 
 k 1 =ZR 1 /ZS 1
 
 k 2 =ZS 2 /ZR 2
 
ZS1: the number of teeth of first sun gear
 
ZR1: the number of teeth of first ring gear
 
ZS2: the number of teeth of second sun gear
 
ZR2: the number of teeth of second ring gear
 
     Next, the operation states will be described using an alignment chart. In the rotation speed, the rotation direction of the output shaft  3  of the internal combustion engine  2  is set as a positive direction. In addition, in the torque that is input/output to/from each shaft, a direction in which torque having the same direction as that of the torque of the output shaft  3  of the internal combustion engine  2  is input is defined as positive. Accordingly, in a case where the torque of the driving shaft  7  is positive, a state is formed in which torque for driving the hybrid vehicle to the rear side is output (deceleration at the time of forward driving and driving at the time of backward driving). On the other hand, in a case where the torque of the driving shaft  7  is negative, a state is formed in which torque for driving the hybrid vehicle to the front side is output (driving at the time of forward driving, and deceleration at the time of backward driving). 
     In a case where power generation or backward driving (acceleration by transmitting power to the drive wheel  7  or maintaining a balanced speed on an ascending slope) is performed by the first and second motor generators  4  and  5 , there are losses due to heat generation in the first and second inverters  18  and  19  and the first and second motor generators  4  and  5 , and accordingly, the efficiency is not 100% in a case where a conversion between electric energy and mechanical energy is made. However, for the simplification of description, it is assumed that there is no loss. In a case where the loss is considered for practical implementation, power generation is controlled so as to additionally generate power corresponding to the energy consumed due to the loss. 
     (1) Low Gear Ratio State ( FIG. 13 ) 
     Driving is performed using the internal combustion engine  2 , and a state is formed in which the rotation speed of the second motor generator  5  is zero. The alignment chart at this time is illustrated in  FIG. 13 . Since the rotation speed of the second motor generator  5  is zero, no power is consumed. Thus, in a case where there is no charge/discharge of the battery  20 , power generation using the first motor generator  4  does not need to be performed, and the torque instruction value Tmg1 of the first motor generator  4  is zero. 
     In addition, the ratio between the engine rotation speed of the output shaft  3  and the driving shaft rotation speed of the driving shaft  7  is (1+k2)/k2. 
     (2) Intermediate Gear Ratio State ( FIG. 14 ) 
     Driving is performed using the internal combustion engine  2 , and a state is formed in which the rotation speeds of the first and second motor generators  4  and  5  are positive. The alignment chart at this time is illustrated in  FIG. 14 . In this case, in a case where there is no charge/discharge of the battery  20 , the first motor generator  4  is regenerated, and the second motor generator  5  is reversely operated using the regenerated electric power. 
     (3) High Gear Ratio State ( FIG. 15 ) 
     Driving is performed using the internal combustion engine  2 , and a state is formed in which the rotation speed of the first motor generator  4  is zero. The alignment chart at this time is illustrated in  FIG. 15 . Since the rotation speed of the first motor generator  4  is zero, regeneration is not performed. Accordingly, in a case where there is no charge/discharge of the battery  20 , the reverse operation or the regeneration is not performed by the second motor generator  5 , and the torque instruction value Tmg2 of the second motor generator  5  is zero. 
     In addition, the ratio between the engine rotation speed of the output shaft  3  and the driving shaft rotation speed of the driving shaft  7  is k1/(1+k1). 
     (4) State in which Power Circulation is Performed ( FIG. 16 ) 
     In a state in which the vehicle speed is higher than the high gear ratio state, a state is formed in which the first motor generator  4  is reversely rotated. In this state, the first motor generator  4  is reversely operated, thereby consuming the electric power. Accordingly, in a case where there is no charge/discharge of the battery  20 , the second motor generator  5  is regenerated and performs power generation. 
     As above, in the drive control device  1  of the hybrid vehicle, the target driving power setting means  44  sets the driving power corresponding to the state in which power assistance depending on the electric power of the battery  20  is received as a maximal value of the target driving power in advance, the target engine power calculating means  46  sets the maximal value of the target engine power corresponding to the maximal output that can be output by the internal combustion engine  2  in advance, compares the target engine power and the maximal value of the target engine power calculated by the target driving power setting means  44  and the target charge/discharge power setting means  45  with each other, and updates the target engine power with a smaller value thereof, a target electric power calculating means  48  calculating the target electric power that is a target value of the input/output electric power for the battery  20  based on a difference between the target driving power and the target engine power is arranged, and the motor torque instruction value calculating means  49  calculates the torque instruction values of a plurality of the first and second motor generators  4  and  5  by using the torque balance equation including the target engine torque required at the target engine operating point and the electric power balance equation including the target electric power. 
     In the torque balance equation, as illustrated in Equation (4) described above, the torque instruction values of a plurality of the first and second motor generators  4  and  5  that are target torques thereof and the target engine torque of the internal combustion engine  2  are balanced based on a lever ratio that is based on the gear ratio of the differential gear mechanism  8  of the power input/output device that mechanically operates and connects a plurality of the first and second motor generators  4  and  5  and the internal combustion engine  2 . 
     Thus, according to the drive control device  1  of the hybrid vehicle, the charge state SOC of the battery  20  can be formed within a predetermined range while the engine operating point is controlled so as to match a target value, and a power assistance region in which the electric power of the battery  20  is used can be arranged, and driving using the electric power of the battery  20  can be performed using the power assistance region in accordance with a driver&#39;s request. 
     In addition, according to the drive control device  1  of the hybrid vehicle, a plurality of the first and second motor generators  4  and  5  in a case where there is charge/discharge of the battery  20  can be controlled, and both the target driving force and target charging/discharging can be secured in consideration of the engine operating point of the internal combustion engine  2 . 
     The motor torque instruction value calculating means  49  sets feedback correction amounts in the torque instruction values of a plurality of the first and second motor generators  4  and  5  such that actual engine rotation speed converges on the target engine rotation speed required at the target engine operating point. 
     The feedback correction amounts set in the torque instruction values of a plurality of the first and second motor generators  4  and  5  are set in association with the gear ratio or the lever ratio of the differential gear mechanism  8  including four rotating components  34  to  37  connected to the plurality of the first and second motor generators  4  and  5 , the driving shaft  7 , and the internal combustion engine  2 . 
     As above, according to the drive control device  1  of the hybrid vehicle, by finely correcting the torque instruction values of the plurality of the first and second motor generators  4  and  5 , the engine rotation speed can converge on the target engine rotation speed in a speedy manner. In addition, according to the drive control device  1  of the hybrid vehicle, the engine operating point can match the target operating point, whereby an appropriate operating state can be formed. 
     The motor torque instruction value calculating means  49  calculates the target engine rotation speed required at the target engine operating point and the rotation speeds of the plurality of the first and second motor generators  4  and  5  based on the vehicle speed, calculates the torque instruction value of the first motor generator based on the rotation speeds of the plurality of the first and second motor generators  4  and  5 , the target electric power, and the target engine torque, and calculates the torque instruction value of the second motor generator  5  based on the torque instruction value of the first motor generator  4  and the target engine torque. 
     From this, according to the drive control device  1  of the hybrid vehicle, in addition to the above-described advantages, the torque instruction values of the plurality of the first and second motor generators  4  and  5  are separately calculated, and accordingly, feedback correction can be individually performed for the torque instruction values. 
     INDUSTRIAL APPLICABILITY 
     The present invention sets up control of a plurality of motor generators in a case where a battery is charged or discharged, secures both a target driving force and target charging/discharging in consideration of an operating point of an internal combustion engine, and has the breath of control of using the electric power of the battery under a more specific condition and can be applied to the control of the driving force of a hybrid vehicle. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  drive control device of hybrid vehicle 
               2  internal combustion engine 
               3  output shaft 
               4  first motor generator 
               5  second motor generator 
               7  driving shaft 
               8  differential gear mechanism 
               18  first inverter 
               19  second inverter 
               20  battery 
               21  first planetary gear mechanism 
               22  second planetary gear mechanism 
               31  one-way clutch 
               32  output unit 
               34  first rotating component 
               35  second rotating component 
               36  third rotating component 
               37  fourth rotating component 
               38  drive control unit 
               39  accelerator opening degree detecting means 
               40  vehicle speed detecting means 
               41  engine rotation speed detecting means 
               42  battery charge state detecting means 
               43  target driving force setting means 
               44  target driving power setting means 
               45  target charge/discharge power setting means 
               46  target engine power calculating means 
               47  target engine operating point setting means 
               48  target electric power setting means 
               49  motor torque instruction value calculating means