Patent Publication Number: US-9421871-B2

Title: Motor controller

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based on Japanese Patent Application No. 2014-230774 filed on Nov. 13, 2014, the disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a motor controller which controls a motor mounted to a vehicle. 
     BACKGROUND 
     JP 2007-129827A discloses an intelligent brake assist system generating a regeneration braking force by utilizing a motor in a case where a vehicle is operating in an area necessary to use a brake assist operation. 
     SUMMARY 
     In the intelligent brake assist system, the regeneration braking force is generated in an emergency avoidance necessary to execute the brake assist operation. 
     The present disclosure is made in view of the above matters, and it is an object of the present disclosure to provide a motor controller which can suppress an own vehicle from approaching a front vehicle according to a speed-reduction request of a user and can efficiently generate an electric power. 
     According to an aspect of the present disclosure, the motor controller controls a motor mounted to a vehicle. The motor controller includes an inter-vehicle sensor, a speed sensor, an accelerator sensor, and a control portion. 
     The inter-vehicle sensor detects an inter-vehicle distance between an own vehicle and a front vehicle that is travelling in front of the own vehicle. 
     The speed sensor detects a speed difference between a speed of the own vehicle and a speed of the front vehicle. 
     The accelerator sensor detects an accelerator pressing quantity generated by a user driving the own vehicle. 
     The control portion controls a regeneration torque of the motor based on the inter-vehicle distance, the speed difference, and the accelerator pressing quantity. 
     When the control portion determines that the accelerator pressing quantity is less than or equal to a predetermined pressing quantity, the control portion determines that a speed-reduction request is generated by the user. When the control portion determines that the inter-vehicle distance is no more than a first predetermined distance and when the own vehicle is in an approaching state where the speed difference is greater than a predetermined speed, the control portion increases the regeneration torque of the motor to be greater than the regeneration torque of when the inter-vehicle distance is greater than the first predetermined distance or when the own vehicle is in a non-approaching state where the speed difference is no more than the predetermined speed, so as to generate a regeneration braking force. 
     Thus, an approaching of the own vehicle toward the front vehicle can be suppressed according to the speed-reduction request of the user, and an electric-power generation can be efficiently executed according to the regeneration braking force generated by increasing the regeneration torque. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: 
         FIG. 1  is a block diagram showing an outline of a hybrid vehicle; 
         FIG. 2  is a schematic diagram showing a power distribution mechanism; 
         FIG. 3  is a block diagram showing a control portion; 
         FIG. 4  is a flowchart showing a regeneration of a hybrid ECU of when a speed-reduction request is generated; 
         FIG. 5  is a schematic diagram showing a state that an inter-vehicle distance is a speed-reduction distance; 
         FIG. 6  is a schematic diagram showing a state that a speed difference becomes zero according to a generation of a regeneration-braking force and the inter-vehicle distance becomes a safe distance; 
         FIG. 7  is a graph showing a time variation of a vehicle speed generated according to an ideal regeneration torque; and 
         FIG. 8  is a block diagram showing a modification example of the hybrid vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure will be described hereafter referring to drawings. In the embodiments, a part that corresponds to a matter described in a preceding embodiment may be assigned with the same reference numeral, and redundant explanation for the part may be omitted. When only a part of a configuration is described in an embodiment, another preceding embodiment may be applied to the other parts of the configuration. The parts may be combined even if it is not explicitly described that the parts can be combined. The embodiments may be partially combined even if it is not explicitly described that the embodiments can be combined, provided there is no harm in the combination. 
     Hereafter, referring to drawings, a motor controller applied to a hybrid vehicle  100  according to an embodiment will be described. 
     First Embodiment 
     Referring to  FIGS. 1 to 7 , the hybrid vehicle  100  will be detailed. The motor controller includes a control portion  80  and a sensing portion  90 . 
     As shown in  FIG. 1 , the hybrid vehicle  100  includes an engine  10 , a first motor generator  20  and a second motor generator  30 . The engine  10  and the first motor generator  20  function as a motive power source, and the first motor generator  20  and the second motor generator  30  function as a power generating source. The hybrid vehicle  100  further includes a power distribution mechanism  40  distributing power to a vehicle travelling and an electric-power generation. The engine  10  generates a motive power by combusting a fuel, and the first motor generator  20  generates the motive power by rotating an output shaft according to an electric power. The first motor generator  20  generates the electric power when the output shaft is rotated by a rotational energy of a wheel, and the second motor generator  30  generates the electric power when the output shaft is rotated by the motive power of the engine  10 . 
     The hybrid vehicle  100  further includes a speed reducer  50 , a drive shaft  51 , a drive wheel  52 , a hydraulic brake  53 , an inverter  60 , a power storage portion  70 , the control portion  80 , and the sensing portion  90 . The power distribution mechanism  40  is connected to the speed reducer  50 , and the speed reducer  50  is connected to the drive wheel  52  through the drive shaft  51 . The motive power distributed to the speed reducer  50  by the power distribution mechanism  40  is transmitted to the drive wheel  52  through the drive shaft  51 , and then the hybrid vehicle  100  is driven to travel. The power storage portion  70  is electrically connected with the first motor generator  20  and the second motor generator  30  through the inverter  60 . The electric power supplied from the power storage portion  70  is supplied to the first motor generator  20  and the second motor generator  30  through the inverter  60 , and then the first motor generator  20  and the second motor generator  30  are rotated. Conversely, the electric power generated by the first motor generator  20  and the second motor generator  30  is supplied to the power storage portion  70  through the inverter  60 , and then the power storage portion  70  is electric charged. The inverter  60  is controlled by the control portion  80 . The control portion  80  controls the first motor generator  20  and the second motor generator  30  to generate the motive power or generate the electric power. A deceleration of a vehicle speed is controlled according to a braking force of the hydraulic brake  53  and a regeneration-braking force of the first motor generator  20 . 
     The engine  10  includes a cylinder, a piston, an injector, a plug, and a crank shaft. The cylinder and the piston constitute a combustion chamber, and a spray of a fuel is injected by the injector into the combustion chamber. The plug generates a spark in the combustion chamber. When the spray of the fuel is injected into the combustion chamber, the spark is generated, and then the fuel is combusted in the combustion chamber. A volume expansion and volume compression of a gas in the combustion chamber generated according to a combustion of the fuel, an intake gas of the combustion chamber, and an exhaust gas of the combustion chamber controls the piston to move reciprocally. In this case, a reciprocating motion of the piston is converted to a rotational motion by the crack shaft. The rotational motion is transmitted to the power distribution mechanism  40  as the power. The crank shaft is linked to a planetary carrier  42  of the power distribution mechanism  40 , and the planetary carrier  42  is rotated by a rotation of the crank shaft. When the engine  10  is not started, the crank shaft is cranked by a rotation of the planetary carrier  42 . 
     The first motor generator  20  has a function generating the motive power, and both the first motor generator  20  and the second motor generator  30  have a function generating the electric power. Both the first motor generator  20  and the second motor generator  30  have the output shaft, a rotor fastened to the output shaft, and a stator provided around the rotor. The rotor includes a permanent magnet, and the stator includes a fixing member wound by plural stator coils. According to the present embodiment, the fixing member may be made of iron. Since the inverter  60  controls a current to flow through the stator coils of the first motor generator  20  so as to generate a rotational torque on the rotor of the first motor generator  20 , the output shaft of the first motor generator  20  rotates together with the rotor, and the motive power is transmitted to the power distribution mechanism  40 . When the output shaft of the first motor generator  20  rotates together with the rotor of the first motor generator  20  by the rotational energy of the drive wheel  52 , a magnetic flux passing through the stator of the first motor generator  20  varies in time according to a rotation of the rotor, and a current flows through the plural stator coils of the first motor generator  20 . Thus, the first motor generator  20  executes the electric-power generation. When the output shaft of the second motor generator  30  rotates together with the rotor of the second motor generator  30  by the motive power of the engine  10 , the magnetic flux passing through the stator of the second motor generator  30  varies in time according to the rotation of the motor, and the current flows through the plural stator coils of the second motor generator  30 . Thus, the second motor generator  30  executes the electric-power generation. The current generated according to the electric-power generation is supplied to the power storage portion  70  through the inverter  60 , and the power storage portion  70  is electric charged. According to the present embodiment, the first motor generator  20  is referred to as a first MG  20 , and the second motor generator  30  is referred to as a second MG  30 . 
     As shown in  FIG. 2 , the power distribution mechanism  40  includes a sun gear  41 , the planetary carrier  42 , a ring gear  43 , and a pinion gear  44 . The sun gear  41  and the pinion gear  44  are a disk shape, and have teeth on an outer peripheral surface. The ring gear  43  is a disk shape, and has teeth on an inner peripheral surface. The sun gear  41  is placed at a position that is a center of an area surrounded by the inner peripheral surface of the ring gear  43 . The pinion gear  44  is interposed between the sun gear  41  and the ring gear  43 . The sun gear  41 , the pinion gear  44 , and the ring gear  43  mesh with each other. When a torque is generated in one gear of the above gears to rotate the one gear, other gears of the above gears also rotate together with the one gear. As shown in  FIG. 2 , a direction indicated by a solid arrow is a positive rotational direction that is a clockwise rotational direction, and a direction indicated by a dashed arrow is a negative rotational direction that is a counterclockwise rotational direction. 
     The sun gear  41  is connected to the output shaft of the second MG  30 , and the planetary carrier  42  is connected to the crank shaft of the engine  10 . The ring gear  43  is connected to the output shaft of the first MG  20 , and the pinion gear  44  is connected to the planetary carrier  42 . When the output shaft of the first MG  20  rotates in the positive rotational direction in a case where the engine  10  is stopped, a positive torque is generated in the ring gear  43 , and the ring gear  43  also rotates in the positive rotational direction. Then, the pinion gear  44  also rotates in the positive rotational direction according to a positive rotation of the ring gear  43 , and the sun gear  41  rotates in the negative rotational direction. In this case, since no torque is generated in the sun gear  41 , the pinion gear  44  only rotates in its axis, but not revolves around the sun gear  41 . Further, the planetary carrier connected to the pinion gear  44  does not rotate. When the positive torque is generated in the output shaft of the second MG  30 , a braking torque is generated in the sun gear  41 . In this case, a negative rotation of the sun gear  41  is weakened, and a number difference between a rotational number of the sun gear  41  and the rotational number of the ring gear  43  is generated. The positive torque is generated in the pinion gear  44  according to the number difference, and then the pinion gear  44  starts to revolve around the sun gear  41 . Further, the planetary carrier  42  connected to the pinion gear  44  also starts to rotate. Since the planetary carrier  42  is connected to the crank shaft, the crank shaft is cranked according to the rotation of the planetary carrier  42 . When the rotation number of the crank shaft exceeds a predetermined number, the fuel is injected by the injector, a spark is generated by the plug, and the engine  10  is started. 
     When the positive torque is generated in the planetary carrier  42  according to a start of the engine  10  in a case where the braking torque is generated in the sun gear  41 , the planetary carrier  42  rotates in the positive rotational direction, and the ring gear  43  and the sun gear  41  also rotate in the positive rotational direction. In this case, when the positive torque is generated in the ring gear  43 , the motive power generated by the engine  10  and the first MG  20  is transmitted to the drive shaft  51 . When the braking torque is generated in the sun gear  41 , the second MG  30  executes the electric-power generation. When the braking torque is generated in the ring gear  43  in a case where an accelerator pressing quantity becomes zero and the engine  10  is stopped, the first MG  20  executes the electric-power generation by utilizing the rotational energy of the wheel. The electric power generated by the first MG  20  is supplied to the power storage portion  70  through the inverter  60 . In addition, the electric power generated by the second MG  30  is used to charge the power storage portion  70  or to generate the positive torque of the first MG  20 . 
     The inverter  60  has a function that converts a direct-current electric power supplied from the power storage portion  70  into an alternating-current electric power, and a function that converts the alternating-current electric power supplied from the first MG  20  and the second MG  30  into the direct-current electric power. The inverter  60  includes plural transistor elements. Since the control portion  80  controls a drive of the transistor elements, a flowing direction of the current flowing through the stator coils is controlled, and the positive torque or the braking torque is generated in the first MG  20  and the second MG  30 . 
     The power storage portion  70  that is a battery supplies the direct-current electric power to the inverter  60 . 
     The control portion  80  is a control system of the hybrid vehicle  100 . As shown in  FIG. 3 , the control portion  80  includes a hybrid ECU  81 , an engine ECU  82 , a motor ECU  83 , a battery ECU  84 , a brake ECU  85 , and a bus wiring  86 . The hybrid ECU  81 , the engine ECU  82 , the motor ECU  83 , the battery ECU  84 , and the brake ECU  85  can send and receive signals to each other through the bus wiring  86 . 
     The hybrid ECU  81  cooperative controls the engine  10 , the first MG  20 , and the second MG  30  to control a travelling of the hybrid vehicle  100 . The hybrid ECU  81  calculates a torque and a rotational number which are necessary for the travelling, based on an accelerator opening degree or a battery charging capacity, and sends commands to the engine ECU  82  and the motor ECU  83 . The engine ECU  82  and the motor ECU  83  control the rotational number and the torque of the engine  10 , the first MG  20 , and the second MG  30 , and control a travelling state of the hybrid vehicle  100 . The hybrid ECU  81  generates the regeneration-braking force to control a speed difference between a speed of an own vehicle and a speed of a front vehicle to be zero in a case where a speed-reduction request of a user is generated. According to the present embodiment, the speed-reduction request may be generated in a normal travelling of the own vehicle. When the speed difference is not zero, the hybrid ECU  81  sends an operation command of the hydraulic brake  53  to the brake ECU  85 . The brake ECU  85  increases an oil pressure of the hydraulic brake  53  based on the operation command, and the braking force is generated in the hybrid vehicle  100 . 
     As shown in  FIG. 1 , the sensing portion  90  includes an inter-vehicle sensor  91 , an accelerator sensor  92 , and a battery sensor  93 . The inter-vehicle sensor  91  detects an inter-vehicle distance between the own vehicle and the front vehicle at a predetermined time. The front vehicle is a vehicle travelling in front of the own vehicle. The inter-vehicle sensor  91  is provided with a millimeter wave radar or a camera. The accelerator sensor  92  detects the accelerator pressing quantity generated by the user driving the own vehicle. The battery sensor  93  detects a battery state of the own vehicle including an available capacity of the power storage portion  70  and an electric quantity of the power storage portion  70  chargeable per unit time. The above sensor signals detected by the sensing portion  90  are transmitted to the control portion  80 . According to the present embodiment, the hybrid ECU  81  calculates the speed difference based on the inter-vehicle distance. The hybrid ECU  81  calculates the speed difference based on a time variation of the inter-vehicle distance. When the inter-vehicle distance is shortened, the speed difference is a positive value. When the inter-vehicle distance is increased, the speed difference is a negative value. When the speed difference is a positive value, the own vehicle travels faster than the front vehicle. When the speed difference is a negative value, the own vehicle travels slower than the front vehicle. When the speed difference is zero, the speed of the own vehicle is equal to the speed of the front vehicle. When the speed difference is maintained to a positive value, the own vehicle is in a state approaching the front vehicle. When the speed difference is maintained to a negative value, the own vehicle is in a state separating from the front vehicle. When the speed difference is maintained to zero, the inter-vehicle distance is maintained to be constant. According to the present embodiment, the hybrid ECU  81  functions as a speed sensor. In addition, the sensing portion  90  includes a vehicle-speed sensor detecting a speed of the own vehicle, or a navigation system storing a tilted angle of a road surface gradient. 
     Referring to  FIGS. 4 to 7 , the regeneration of the hybrid ECU  81  of when the speed-reduction request is generated will be described. As shown in  FIG. 4 , at S 10 , the hybrid ECU  81  loads the accelerator pressing quantity from the accelerator sensor  92 , and determines whether the accelerator pressing quantity is zero. In other words, the hybrid ECU  81  determines whether the user stops a pressing of the accelerator pedal and the speed-reduction request is generated. When the hybrid ECU  81  determines that the accelerator pressing quantity is zero and the speed-reduction request is generated, the hybrid ECU  81  proceeds to S 20 . When the hybrid ECU  81  determines that the accelerator pressing quantity is greater than zero, the hybrid ECU  81  repeatedly executes operations in S 10 . In other words, the hybrid ECU  81  waits until the speed-reduction request is generated. 
     At S 20 , the hybrid ECU  81  loads the inter-vehicle distance from the inter-vehicle sensor  91 . Further, the hybrid ECU  81  calculates the speed difference based on the inter-vehicle distance. Then, the hybrid ECU  81  proceeds to S 30 . 
     At S 30 , the hybrid ECU  81  determines whether the inter-vehicle distance is no more than a speed-reduction distance L1 and the speed difference is a positive value. In other words, the hybrid ECU  81  determines whether the own vehicle is approaching the front vehicle and the inter-vehicle distance is no less than a distance necessary to increase a regeneration torque to generate the regeneration braking force. When the hybrid ECU  81  determines that the inter-vehicle distance is no more than the speed-reduction distance L1 and the speed difference is a positive value, the hybrid ECU  81  proceeds to S 40 . In this case, when the speed difference is a positive value, the own vehicle is in an approaching state. When the hybrid ECU  81  determines that the inter-vehicle distance is greater than the speed-reduction distance L1 or the speed difference is not a positive value, the hybrid ECU  81  returns to S 10 . 
     The speed-reduction distance L1 is established based on a distance where a human feels the speed of the own vehicle is necessary to be reduced when the own vehicle is approaching the front vehicle and starts to reduce the speed of the own vehicle. The speed-reduction distance L1 may be a fixed value, or may be a variable value that is changed based on the speed difference, the road surface gradient, or weather. Alternatively, since an approaching time of the own vehicle approaching the front vehicle is determined by the inter-vehicle distance and the speed difference, the speed-reduction distance L1 may be established according to the inter-vehicle distance and the speed difference. According to the present embodiment, the speed-reduction distance L1 is a first predetermined distance. 
     At S 40 , the hybrid ECU  81  calculates an ideal deceleration speed that makes the speed difference become zero in a case where the inter-vehicle distance is changed from the speed-reduction distance L1 to a safe distance L2, and calculates an ideal regeneration torque to generate the ideal deceleration speed. As shown in  FIG. 5 , the speed of the own vehicle is expressed as v1, the speed of the front vehicle is expressed as v2 that is less than v1, and the inter-vehicle distance is the speed-reduction distance L1, at a time point t1. In this case, when the ideal regeneration torque is generated, the speed difference is gradually reduced as shown in  FIG. 7 . As shown in  FIG. 6 , the speed of the own vehicle becomes v2 that is equal to the speed of the front vehicle, and the speed difference becomes zero, and the inter-vehicle distance becomes the safe distance L2, at a time point t2. In other words, the speed of the own vehicle is gradually reduced from v1 to v2 in a time period from the time point t1 to the time point t2 where the own vehicle approaches the front vehicle by a distance (L1-L2). Then, the inter-vehicle distance is maintained to the safe distance L2, and a noticing to passengers of the own vehicle that a variation of a speed reduction generated by the regeneration braking force is suppressed. The speed reduction generated by the ideal regeneration torque is set to make a driveability optimum. 
     The ideal regeneration torque is greater than the regeneration torque of when the own vehicle is not in the approaching state. In other words, the ideal regeneration torque is greater than the regeneration torque of when the own vehicle is in a non-approaching state or is greater than the regeneration torque in S 10  to S 30 . The ideal regeneration torque is calculated such that a vehicle speed variation is constant in a case where the inter-vehicle distance varies from L1 to L2 and the speed of the own vehicle varies from v1 to v2. In this case, the vehicle speed variation is a variation of the speed of the own vehicle. Since the speed of the own vehicle varies not only according to the regeneration torque but also according to the road surface gradient, a calculation of the ideal regeneration torque not only considers the speed difference and the inter-vehicle distance but also may consider the speed of the own vehicle and the road surface gradient. The safe distance L2 is a distance that the own vehicle can prevent from being collided with the front vehicle when the front vehicle is sharply decelerated and a pressing of the hydraulic brake  53  or a travelling operation is executed by the user to maintain a sufficient inter-vehicle distance. In other words, the safe distance L2 a distance sufficiently greater than the inter-vehicle distance that is necessary for a brake assist. The safe distance L2 may be a fixed value, or may be a variable value that is changed based on the speed difference, the road surface gradient, or weather. Alternatively, since the approaching time of the own vehicle approaching the front vehicle is determined by the inter-vehicle distance and the speed difference, the safe distance L2 may be established according to the inter-vehicle distance and the speed difference. According to the present embodiment, the safe distance L2 is a second predetermined distance. 
     At S 50 , the hybrid ECU  81  loads the available capacity of the power storage portion  70  and the electric quantity of the power storage portion  70  chargeable per unit time by utilizing the battery sensor  93 . The hybrid ECU  81  stores an upper limit of the regeneration torque determined by the driveability, and calculates an allowable regeneration torque that is feasible in a current vehicle state, based on the available capacity of the power storage portion  70 , the electric quantity of the power storage portion  70  chargeable per unit time, and the upper limit of the regeneration torque. The allowable regeneration torque is greater than the regeneration torque of when the own vehicle is in the non-approaching state. The hybrid ECU  81  proceeds to S 60  after calculating the allowable regeneration torque. 
     At S 60 , the hybrid ECU  81  compares the ideal regeneration torque calculated at S 40  with the allowable regeneration torque calculated at S 50 . In other words, the hybrid ECU  81  determines whether the ideal regeneration torque is greater than the allowable regeneration torque. When the hybrid ECU  81  determines that the ideal regeneration torque is less than or equal to the allowable regeneration torque, the hybrid ECU  81  determines that the regeneration torque can be set to the ideal regeneration torque, and proceeds to S 70 . When the hybrid ECU  81  determines that the ideal regeneration torque is greater than the allowable regeneration torque, the hybrid ECU  81  determines that the regeneration torque cannot be set to the ideal regeneration torque, and proceeds to S 80 . 
     At S 70 , the hybrid ECU  81  outputs a command to the motor ECU  83  to set the regeneration torque to the ideal regeneration torque. Then, the hybrid ECU  81  returns to S 10  to execute the regeneration, and adjusts the regeneration torque at a predetermined time interval Δt. 
     At S 80 , the hybrid ECU  81  calculates a final regeneration torque that is closest to the ideal regeneration torque, based on the allowable regeneration torque. In other words, the hybrid ECU  81  calculates the final regeneration torque that makes the speed difference become close to zero at the safe distance L2 at the earliest stage and the driveability becomes highest, in the allowable regeneration torque. That is, the hybrid ECU  81  calculates the final regeneration torque that makes the speed difference become close to zero in a case where the inter-vehicle distance is changed to the safe distance L2, based on the allowable regeneration torque. The final regeneration torque is also calculated such that the vehicle speed variation is substantially constant in a case where the inter-vehicle distance varies from L1 to L2. Then, the hybrid ECU  81  proceeds to S 90 . 
     At S 90 , the hybrid ECU  81  outputs a command to the motor ECU  83  to set the regeneration torque to the final regeneration torque. Then, the hybrid ECU  81  returns to S 10  to execute the regeneration, and adjusts the regeneration torque at the predetermined time interval Δt. 
     As the above description, the hybrid ECU  81  repeatedly executes operations from S 10  to S 90  at the predetermined time interval Δt to adjust the regeneration torque. In other words, the hybrid ECU  81  executes operations to set the regeneration torque to the ideal regeneration torque or the final regeneration torque at the predetermined time interval Δt, until the inter-vehicle distance becomes the safe distance L2 and the speed difference becomes zero. 
     In addition, the hybrid ECU  81  continuously monitors the inter-vehicle distance and the speed difference in the regeneration. When the hybrid ECU  81  determines that the inter-vehicle distance is less than the safe distance L2 and the speed difference is a positive value in the regeneration where the speed of the own vehicle is reduced only by the regeneration braking force, the hybrid ECU  81  determines that it is necessary to generate the braking force by the hydraulic brake  53 . In this case, the hybrid ECU  81  outputs a command to the brake ECU  85  to generate the braking force by the hydraulic brake  53 . A condition that the braking force generated by the hydraulic brake  53  is necessary is assumed to be generated in a case where the speed of the front vehicle is sharply changed or the road surface gradient is sharply changed. In addition, since the speed difference is not zero at the safe distance L2 after the regeneration braking force is generated by the final regeneration torque, it is assumed that the braking force generated by the hydraulic brake  53  is necessary. 
     Next, effects of the hybrid vehicle  100  according to the present embodiment will be described. When the accelerator pressing quantity becomes zero, the hybrid ECU  81  determines that the speed-reduction request of the user is generated. When the hybrid ECU  81  determines that the own vehicle is in the approaching state where the own vehicle is approaching the front vehicle and the regeneration torque is necessary to be increased to generate the regeneration braking force, the hybrid ECU  81  sets the regeneration torque to the ideal regeneration torque or the final regeneration torque. Therefore, the hybrid ECU  81  increases the regeneration torque to be greater than the regeneration torque of when the own vehicle is in the approaching state, so as to generate the regeneration braking force. Thus, the approaching of the own vehicle toward the front vehicle can be suppressed according to the speed-reduction request of the user, and the electric-power generation can be efficiently executed according to the regeneration braking force generated by increasing the regeneration torque. 
     The ideal regeneration torque and the final regeneration torque are set such that the vehicle speed variation is substantially constant. Therefore, it is suppressed that the vehicle speed is sharply changed due to a generation of the regeneration braking force. In other words, it is suppressed that a variation of an acceleration generated according to the regeneration braking force is noticed to passengers of the own vehicle. 
     The regeneration torque is adjusted at the predetermined time interval. Therefore, the ideal regeneration torque or the final regeneration torque can be set according to a battery state of the own vehicle, a speed variation of the front vehicle, or a gradient variation of the road surface gradient. 
     When the hybrid ECU  81  determines that the inter-vehicle distance is less than the safe distance L2 and the speed difference is a positive value in the regeneration where the speed of the own vehicle is reduced only by the regeneration braking force, the hybrid ECU  81  outputs a command to the brake ECU  85  to generate the braking force by the hydraulic brake  53 . Therefore, when the inter-vehicle distance is less than the safe distance L2, it is suppressed that the own vehicle approaches the front vehicle. 
     The present disclosure is not limited to the embodiments mentioned above, and can be applied to various embodiments within the spirit and scope of the present disclosure. 
     According to the present embodiment, the hybrid vehicle  100  includes the first MG  20 , the second MG  30 , and the power distribution mechanism  40 . However, the hybrid vehicle  100  is not limited. As shown in  FIG. 8 , the hybrid vehicle  100  may only include the first MG  20  without including the second MG  30  and the power distribution mechanism  40 . As shown in  FIG. 8 , in the hybrid vehicle  100 , a power transmission shaft  56  is connected to the drive shaft  51  through a differential gear  55 , and the speed reducer  50  is arranged at the power transmission shaft  56 . The power transmission shaft  56  is provided with the engine  10 , the first MG  20 , a first clutch  54   a,  and a second clutch  54   b.  The first clutch  54   a  is interposed between the engine  10  and the first MG  20 , and the second clutch  54   b  is interposed between the first MG  20  and the speed reducer  50 . Thus, a power transmission level from the engine  10  to the power transmission shaft  56  is adjusted by the first clutch  54   a,  and a power transmission level from the engine  10  and the first MG  20  to the speed reducer  50  is adjusted by the second clutch  54   b.    
     In a modification example of the hybrid vehicle  100  as shown in  FIG. 8 , when the accelerator pressing quantity becomes zero, a connection state between the engine  10  and the power transmission shaft  56  is interrupted by the first clutch  54   a.  When the own vehicle is in the approaching state where the own vehicle is approaching the front vehicle and the regeneration torque is necessary to be increased to generate the regeneration braking force, the first MG  20  generates the regeneration braking force. When the connection state between the engine  10  and the power transmission shaft  56  is interrupted by the first clutch  54   a,  a combustion in the engine  10  may be terminated to save energy such that the engine  10  is in a non-drive state. 
     In another modification example of the hybrid vehicle  100 , the first clutch  54   a  is cancelled from a configuration shown in  FIG. 8 . In this case, when the accelerator pressing quantity becomes zero and the own vehicle is in the approaching state, the speed of the own vehicle is reduced by the engine  10 , and the regeneration braking force is generated by the first MG  20 . 
     According to the present embodiment, in the hybrid vehicle  100 , the regeneration braking force is generated by a motor such as the first MG  20 . However, other vehicles in which a motor generates the regeneration braking force may be used. Specifically, the regeneration braking force may be generated by a motor in a gasoline vehicle or an electric vehicle. In other words, the motor controller according to the present embodiment may be applied to any vehicles in which a motor can generate the regeneration braking force. 
     According to the present embodiment, both the first motor generator  20  and the second motor generator  30  have a rotor including a permanent magnet. However, the rotor may include a coil generating a magnetic flux instead of the permanent magnet. Alternatively, the rotor may include both the coil generating a magnetic flux and the permanent magnet. 
     According to the present embodiment, the control portion  80  includes the hybrid ECU  81 , the engine ECU  82 , the motor ECU  83 , the battery ECU  84 , and the brake ECU  85 . However, a configuration that the hybrid ECU  81  functions as the engine ECU  82  or a configuration that the hybrid ECU  81  functions as the motor ECU  83  may be used. In other words, the engine ECU  82  or the motor ECU  83  may be cancelled. 
     According to the present embodiment, the hybrid ECU  81  executes the regeneration shown in  FIG. 4  of when a speed-reduction request is generated. However, the brake ECU  85  may execute the regeneration shown in  FIG. 4  of when a speed-reduction request is generated. 
     According to the present embodiment, the hybrid ECU  81  calculates the speed difference between the speed of the own vehicle and the speed of the front vehicle based on the inter-vehicle distance detected at the predetermined time. However, an inter-vehicle communication may be used to detect the speed difference. In this case, the own vehicle and the front vehicle notice the speed and the torque to each other, and the hybrid ECU  81  calculates the speed difference based on the speed and the torque which are received. 
     According to the present embodiment, when the accelerator pressing quantity becomes zero, it is determined that the speed-reduction request of the user is generated. However, a value determining whether the speed-reduction request of the user is generated is not limited to zero, and a finite value may be used. In this case, at S 10  shown in  FIG. 4 , when the hybrid ECU  81  determines that the accelerator pressing quantity is no more than the finite value, the hybrid ECU  81  proceeds to S 20 . The finite value is a predetermined pressing quantity, and a condition that the accelerator pressing quantity is less than or equal to the finite value includes a condition that the accelerator pressing quantity becomes zero. 
     According to the present embodiment, when the inter-vehicle distance is no more than the speed-reduction distance L1 and when the speed difference is a positive value, it is determined that the own vehicle is in the approaching state where the own vehicle is approaching the front vehicle and the regeneration torque is necessary to be increased to generate the regeneration braking force. However, a reference value of the speed difference is not limited to be a positive value. Specifically, the reference value may be a predetermined value that is finite and positive. In this case, at S 30  shown in  FIG. 4 , when the hybrid ECU  81  determines that the inter-vehicle distance is no more than the speed-reduction distance L1 and the speed difference is greater than the predetermined value that is finite and positive, the hybrid ECU  81  determines that the own vehicle is in the approaching state and proceeds to S 40 . The predetermined value that is finite and positive, and zero are referred to as a predetermined speed. 
     While the present disclosure has been described with reference to the embodiments thereof, it is to be understood that the disclosure is not limited to the embodiments and constructions. The present disclosure is intended to cover various modification and equivalent arrangements. In addition, while the various combinations and configurations, which are preferred, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure.