Patent Publication Number: US-9895993-B2

Title: State of charge indicator of hybrid vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from Japanese Patent Application No. 2015-032488 filed on Feb. 23, 2015, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     The technology relates to an SOC indicator that provides an indication of an SOC of a hybrid vehicle having an EV traveling mode. 
     An engine-electric motor hybrid vehicle (HV) includes an engine and a motor generator as power sources for traveling, allowing for motor assistance on occasions such as acceleration by using electric power. The electric power may be generated in association with use of a regeneration brake, etc. and charged in a battery. 
     In recent years, such a hybrid vehicle is further provided with a function of charging from an external power supply such as a domestic power supply and a commercial power supply, attaining expansion of a range of usability of an electric vehicle (EV) traveling mode that allows for traveling with sole use of the motor generator without using the engine. This type of hybrid vehicle has been spreading as a plug-in hybrid vehicle (PHEV). 
     The plug-in hybrid vehicle as mentioned above may include a secondary battery such as, but not limited to, a lithium ion battery and a nickel hydrogen battery, as power storage to accumulate electric power to be used in traveling. 
     In such a secondary battery, a ratio of residual electric power to chargeable electric power (total capacity) is called a state of charge (SOC). 
     In the plug-in hybrid vehicle, SOC control (charge and discharge control) of the battery may differ as follows between the EV traveling mode that involves traveling with sole use of the motor generator and an HV traveling mode with combined use of the engine and the motor generator. 
     In the EV traveling mode, in many cases, traveling may be started in a range of a relatively high SOC (almost full-charged); when the SOC decreases to the extent that continuation of the EV traveling mode becomes difficult, the EV traveling mode may be switched to the HV traveling mode. 
     In contrast, in the HV traveling mode, the SOC control may be targeted to a relatively low SOC state; within a relatively narrow SOC range, charge (e.g., regenerative power generation) and discharge (motor drive) may be repeated with high frequency. 
     The plug-in hybrid vehicle as mentioned above may include an SOC indicator (a battery residual capacity indicator) in order to present information on residual capacity of the battery to a driver. 
     As one example of existing techniques concerning such an SOC indicator, Japanese Patent (JP-B) No. 5223822 describes a residual capacity indicator that changes display colors of a bar graph in accordance with a first traveling mode and a second traveling mode. The first traveling mode gives priority to traveling with sole use of a motor. The second traveling mode involves use of an internal combustion engine and the generator. 
     JP-B No. 5223822 also provides a description that, in the display in the first traveling mode, the bar graph is color-divided at a position corresponding to residual capacity where the first traveling mode is switched to the second traveling mode. 
     Although the existing technique as mentioned above enables a grasp of a current SOC, it provides a driver with little information on a timing when the traveling mode will be returned to the EV traveling mode again, in a case of recovery of an SOC by charging such as regenerative power generation in traveling in the HV traveling mode. Hence, it is difficult to forecast switching of traveling modes. 
     Moreover, the HV traveling mode generally involves repetitive charge and discharge within a relatively narrower SOC range than that of the EV traveling mode. However, in the existing technique as mentioned above, an SOC indication is regularly performed on a scale of a full SOC range. Thus, charge and discharge in the HV traveling mode may only cause minute fluctuation within a narrow range in the SOC indication, leading to difficulties for a driver in grasping SOC transition. 
     SUMMARY 
     It is desirable to provide an SOC indicator of a hybrid vehicle that allows for an intuitive grasp of a change of traveling modes in response to a change in SOC and SOC transition in each traveling mode. 
     An aspect of the technology provides an SOC indicator including a first indication unit that provides an indicator display within a predetermined display range including a first end and a second end, in accordance with an increase and a decrease in an SOC of a battery of a hybrid vehicle. The first indication unit allows, in an EV traveling mode, the first end to correspond to an upper limit of an SOC range directed to the EV traveling mode, and allows the second end to correspond to a first threshold that defines switching from the EV traveling mode to an HV traveling mode, in which the EV traveling mode gives priority to driving with sole use of an electric motor, and the HV traveling mode involves driving with combined use of an engine and the electric motor, and controlling charge and discharge of the battery to allow the SOC to be within a prescribed range. The first indication unit allows, in the HV traveling mode, the first end to correspond to a second threshold that defines switching from the HV traveling mode to the EV traveling mode, and allows the second end to correspond to a lower limit of an SOC range directed to the HV traveling mode. 
     In the SOC indicator, the first indication unit may provide an indication of a minimum of the indicator display in the EV traveling mode, prior to the switching from the EV traveling mode to the HV traveling mode. The first indication unit may provide an indication of a maximum of the indicator display in the HV traveling mode, prior to the switching from the HV traveling mode to the EV traveling mode. 
     The SOC indicator may further include a second indication unit that provides an indication of the SOC. The second indication unit may include a movable index and a fixed index. The movable index may be movable in accordance with the increase and the decrease in the SOC, and may be movable between positions corresponding to a maximum and a minimum of an SOC range directed to the EV traveling mode and the HV traveling mode. The fixed index is disposed along a movement range of the movable index. 
     In the SOC indicator, the fixed index may include: a first sign that indicates a position corresponding to the first threshold; and a second sign that indicates a position corresponding to the second threshold. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a schematic configuration of a power train and relevant parts of a hybrid vehicle including an SOC indicator according to an implementation of the technology. 
         FIG. 2  illustrates a pointer SOC meter in the SOC indicator according to the implementation. 
         FIG. 3  illustrates an SOC indication, in an EV traveling mode, on an MFD in the SOC indicator according to the implementation. 
         FIG. 4  illustrates an SOC indication, in an HV traveling mode, on the MFD in the SOC indicator according to the implementation. 
         FIG. 5  illustrates one example of SOC transition and switching operation of traveling modes in the hybrid vehicle according to the implementation. 
         FIG. 6  illustrates one example of transition of the SOC indication on the pointer SOC meter and the MFD in the SOC indicator according to the implementation. 
     
    
    
     DETAILED DESCRIPTION 
     An implementation of the technology may involve expanding an indication of an SOC range substantially to an entire region of a display range of a bar graph display. The SOC range may be directed to each of an EV traveling mode and an HV traveling mode. 
     In the following, some implementations of the technology are described in detail with reference to the drawings. 
     An SOC indicator of a hybrid vehicle (hereinafter simply referred to as an “SOC indicator”) according to an implementation may be provided in an engine-electric motor hybrid vehicle that may be, for instance, an automobile such as, but not limited to, a passenger car, and may have a plug-in charging function and an EV traveling mode. The EV traveling mode involves traveling mainly with sole use of a motor. 
       FIG. 1  is a block diagram of a schematic configuration of a power train and relevant parts of a hybrid vehicle including the SOC indicator according to the implementation. 
     Referring to  FIG. 1 , the vehicle may be an engine-electric motor hybrid AWD vehicle including, for example, an engine  10 , a torque converter  20 , an engine clutch  30 , a steering reverser  40 , a variator  50 , an output clutch  60 , a front differential  70 , a rear differential  80 , a transfer clutch  90 , a motor generator  100 , an engine controller  210 , a transmission controller  220 , a motor generator controller  230 , a hybrid integrated controller  240 , a battery  300 , a charger  310 , a combination meter  410 , and a multi-function display (MFD)  420 . 
     The engine  10  may be an internal combustion engine used as a power source for traveling of the vehicle, together with the motor generator  100 . 
     As the engine  10 , for instance, a four-stroke gasoline engine may be used. 
     The engine  10  may include a main body and auxiliaries. The main body and the auxiliaries may be controlled by the engine controller  210 . The engine  10  may generate output torque corresponding to request torque specified by the hybrid integrated controller  240 , based on, for example, an accelerator operation by a driver. 
     The torque converter  20  may be a fluid coupling that transmits an output of the engine  10  to the engine clutch  30 . 
     The torque converter  20  may serve as a starting device that allows for transmission of engine torque in a stop state of the vehicle. 
     The torque converter  20  may be controlled by the transmission controller  220 , and may include an undepicted lock-up clutch that directly couples input side (impeller side) and output side (turbine side). 
     The engine clutch  30  may be provided between the torque converter  20  and the steering reverser  40 , allowing for connection and disconnection of a power transmission route therebetween. 
     For instance, the engine clutch  30  may be disengaged in response to an instruction from the transmission controller  220  on occasions such as, but not limited to, the EV traveling mode. In the EV traveling mode, the vehicle travels with sole use of an output of the motor generator  100 . 
     The steering reverser  40  may be provided between the engine clutch  30  and the variator  50 , allowing for switching between an advance mode and a retreat mode in response to an instruction from the transmission controller  220 . The advance mode may involve direct coupling of the torque converter  20  and the variator  50 . The reverse mode may involve reversing a rotation output of the torque converter  20  and transmitting the reversed rotation output to the variator  50 . 
     The steering reverser  40  may include, for instance, a planetary gear set. 
     The variator  50  may be a transmission mechanism that continuously changes a rotation output of the engine  10  and a rotation output of the motor generator  100 . The rotation output of the engine  10  may be transmitted from the steering reverser  40 . 
     The variator  50  may be, for instance, a chain type continuously variable transmission (CVT) including a primary pulley  51 , a secondary pulley  52 , and a chain  53 . 
     The primary pulley  51  may be provided on input side of the variator  50  in driving of the vehicle, i.e., on output side in regenerative power generation. The primary pulley  51  may be supplied with the rotation outputs of the engine  10  and the motor generator  100 . 
     The secondary pulley  52  may be provided on output side of the variator  50  in driving of the vehicle, i.e., on input side in regenerative power generation. 
     The secondary pulley  52  may be adjacent to the primary pulley  51  and turnable around a rotation axis that is parallel to a rotation axis of the primary pulley  51 . 
     The chain  53  may be annularly formed and wound around the primary pulley  51  and the secondary pulley  52 , allowing for power transmission therebetween. 
     The primary pulley  51  and the secondary pulley  52  each may include a pair of sheaves with the chain  53  interposed therebetween. The primary pulley  51  and the secondary pulley  52  each may change an interval between the pair of sheaves in response to transmission control by the transmission controller  220 , allowing for a continuous change in an effective diameter. 
     The output clutch  60  may be provided between the secondary pulley  52  of the variator  50  and the front differential  70 , and between the secondary pulley  52  of the variator  50  and the transfer clutch  90 , allowing for connection and disconnection of power transmission routes therebetween. 
     The output clutch  60  may be normally engaged in traveling of the vehicle, and may be disengaged in stopping of the vehicle on occasions such as, but not limited to, battery charge by driving the motor generator  100  with use of the output of the engine  10 . 
     The front differential  70  may transmit, to right and left front wheels, driving force transmitted from the output clutch  60 . 
     The front differential  70  may include a final reduction gear and a differential mechanism. The differential mechanism absorbs a difference in rotation speeds of the right and left front wheels. 
     The output clutch  60  and the front differential  70  may be substantially directly coupled to each other. 
     The rear differential  80  may transmit, to right and left rear wheels, driving force transmitted from the output clutch  60 . 
     The rear differential  80  may include a final reduction gear and a differential mechanism. The differential mechanism absorbs a difference in rotation speeds of the right and left rear wheels. 
     The transfer clutch  90  may be provided in the middle of a rear wheel driving force transmission mechanism that transmits driving force from the output clutch  60  to the rear differential  80 , allowing for connection and disconnection of a power transmission route therebetween. 
     The transfer clutch  90  may be, for instance, hydraulic or electromagnetic wet multiplate clutch that makes it possible to continuously change fastening force in engagement, i.e., transmission torque capacity. 
     The fastening force of the transfer clutch  90  may be controlled by the transmission controller  220 . 
     Changing the fastening force of the transfer clutch  90  may allow for adjustment of driving torque distribution to the front and rear wheels. 
     Also, the transfer clutch  90  may decrease or release the fastening force to cause a slip, allowing for absorption of a difference in rotation speeds of the front and rear wheels, when it is necessary to allow the difference in the rotation speeds of the front and rear wheels in turning the vehicle or in executing control such as, but not limited to, anti-lock brake control or vehicle behavior control. 
     The transfer clutch  90  may transmit, to the motor generator  100  through the output clutch  60  and the variator  50 , torque inputted from rear-wheel side through the rear differential  80 , etc. in energy regeneration by the motor generator  100 . 
     The motor generator  100  may be a rotary electric machine that generates the driving force of the vehicle and performs energy regeneration by regenerative power generation with use of torque transmitted from wheel side in deceleration. 
     The motor generator  100  may be disposed concentrically with the primary pulley  51  of the variator  50 . 
     The primary pulley  51  may be coupled to an undepicted rotor of the motor generator  100  through the rotation axis of the primary pulley  51 . 
     As the motor generator  100 , a permanent magnet synchronous motor may be used, for instance. 
     The motor generator  100  may have output torque in driving and an amount of regenerative energy (input torque) in regenerative power generation controlled by the motor generator controller  230 . 
     The engine controller  210  may totally control the engine  10  and its auxiliaries. 
     The transmission controller  220  may totally control parts such as, but not limited to, the lock-up clutch of the torque converter  20 , the engine clutch  30 , the steering reverser  40 , the variator  50 , the output clutch  60 , and the transfer clutch  90 . 
     The motor generator controller  230  may control characteristics such as, but not limited to, the output torque and the amount of regenerative energy of the motor generator  100 . 
     The hybrid integrated controller  240  may integrally control parts such as, but not limited to, the engine controller  210 , the transmission controller  220 , and the motor generator controller  230  in response to the request torque specified based on, for example, the acceleration operation by a driver. 
     Each of these units may include an information processor such as a CPU, a memory such as a RAM and a ROM, an input output interface, and a bus that couples them to one another. 
     Also, these units may communicate with one another through a communication system such as, but not limited to, a CAN communication system, allowing for transmission of necessary information. The CAN communication system is a kind of on-vehicle LAN system. 
     The hybrid integrated controller  240  may change traveling modes of the vehicle between the electric vehicle (EV) traveling mode and a hybrid vehicle (HV) traveling mode based on an SOC as remaining electric energy of the battery  300 . 
     The EV traveling mode may be a traveling mode that involves driving the motor generator  100  with use of power of the battery  300  and gives priority to traveling with sole use of the output of the motor generator  100 . 
     In the EV traveling mode, the engine  10  may be started to allow for traveling with combined use of engine torque, only when driver request torque is large and it is difficult for the motor generator  100  to solely generate sufficient torque. 
     Otherwise, the EV traveling mode may involve traveling of the vehicle with sole use of the output of the motor generator  100  with the engine clutch  30  disengaged. 
     The HV traveling mode may be a traveling mode that involves traveling of the vehicle with combined use of the output torque of the engine  10  and the motor generator  100 . 
     The HV traveling mode may involve traveling of the vehicle with use of the output torque of the motor generator  100  when the driver request torque is small and there is a margin in the SOC; otherwise, the HV traveling mode may involve traveling of the vehicle with use of the output torque of the engine  10 . 
     Also, in a region where the driver request torque is large, the HV traveling mode may involve traveling of the vehicle with combined use of the output torque of the engine  10  and the motor generator  100 . 
     The hybrid integrated controller  240  may allow for automatic transition to the HV traveling mode when, in the EV traveling mode, the SOC of the battery  300  is lower than a predetermined first threshold. 
     Also, the hybrid integrated controller  240  may allow for automatic return to the EV traveling mode when, in the HV traveling mode, the SOC of the battery  300  exceeds a predetermined second threshold. 
     The motor generator controller  230  may supply the drive power to the motor generator  100  from the battery  300  in response to an instruction from the hybrid integrated controller  240 . 
     The motor generator controller  230  may include, for example, an inverter and a converter. The inverter may AC-convert DC power supplied from the battery  300 , and may supply the AC-converted power to the motor generator  100 . The converter may DC-convert AC power supplied from the motor generator  100 , and may supply the DC-converted power to the battery  300 . 
     The battery  300  may be a power source or power storage that supplies the motor generator  100  with power for traveling. 
     As the battery  300 , a secondary battery such as, but not limited to, a lithium ion battery and a nickel hydrogen battery may be used, for instance. 
     The battery  300  may include an SOC detector that detects the SOC, i.e., a percentage of the remaining power to total capacity of the battery. A detected SOC value may be transmitted to the hybrid integrated controller  240 . 
     The battery  300  may be charged with, for instance, power generated by the motor generator  100  on occasions such as, but not limited to, use of a regenerative brake. 
     The battery  300  may further include a plug-in charging function that allows for charging with an external power source. 
     The charger  310  may charge the battery  300  with use of power supplied from an external power source such as, but not limited to, a domestic power source and a commercial power source. 
     The charger  310  may include, for example, a connection device to the external power source, an AC-DC converter, and a transformer. 
     The combination meter  410  may be an instrument panel disposed in a vehicle room and faced with a driver, for instance. 
     The combination meter  410  may include, for example, various instruments such as, but not limited to, a speed meter, an engine tachometer, a fuel meter, a water thermometer, and various indication lamps. The instruments and the indication lamps may be unitized in a common housing. 
     The combination meter  410  may include a pointer SOC meter  411  whose description is given below. 
       FIG. 2  illustrates the pointer SOC meter in the SOC indicator according to the implementation. 
     Referring to  FIG. 2 , the pointer SOC meter  411  may include a pointer  412  and graduations  413   a  to  413   i.    
     The pointer  412  may serve as a “movable index” in one implementation of the technology. The pointer  412  may be of a rotary type, and may be swayable within an angle range of, for instance, about 180°. 
     The pointer  412  may point one end of a movement range (e.g. upward in an instance illustrated in  FIG. 2 ) when the SOC of the battery  300  is a practical upper limit (e.g. 85%) in the EV traveling mode. The pointer  412  may point another end of the movement range (e.g. downward in the instance illustrated in  FIG. 2 ) when the SOC is a practical lower limit (e.g. 15%) in the EV traveling mode and the HV traveling mode. 
     The graduations  413   a  to  413   i  may serve as a “fixed index” in one implementation of the technology. The graduations  413   a  to  413   i  may be provided on a dial or a scale plate as a plate member disposed behind the pointer  412  (or on farther side from a driver). 
     The graduations  413   a  to  413   i  may be disposed substantially along a movement locus of a tip of the pointer  412 , from the one end to the other end of the movement range of the pointer  412 , at substantially equal intervals in a discrete pattern. The movement locus may be shaped substantially as an arc with a central angle of 180°. 
     Near the uppermost graduation  413   a , a letter “F” may be provided as an indication of a substantially full-charged state. 
     Near the lowermost graduation  413   i , a letter “E” may be provided as an indication of emptiness of substantially available power. 
     The graduations  413   a  to  413   i  may be classified into a first group, a second group, and a third group. The first group may include the graduations  413   a  to  413   e . The second group may include the graduations  413   f  and  413   g . The third group may include the graduations  413   h  and  413   i . These groups may be in different indication modes, e.g. in different indication colors from one another. 
     For one instance, the first group, the second group, and the third group may be respectively color-coded in green, light blue, and blue. 
     A region including the graduations  413   a  to  413   e  of the first group may provide an indication of a region that involves executing solely the EV traveling mode. 
     The pointer  412  may point the graduation  413   a  as an indication of a practically full-charged state. As the SOC decreases, the pointer  412  may turn counterclockwise to point the graduations  413   b ,  413   c ,  413   d , and  413   e  sequentially. 
     A region including the graduations  413   f  and  413   g  of the second group may provide an indication of a region that involves executing possibly both the EV traveling mode and the HV traveling mode. 
     Specifically, in the EV traveling mode, when the SOC decreases and the pointer  412  points the region of the second group including the graduations  413   f  and  413   g , the EV traveling mode may be maintained. 
     In the HV traveling mode, when the SOC increases and the pointer  412  points the region of the second group including the graduations  413   f  and  413   g , the HV traveling mode may be maintained. 
     Here, the graduation  413   f  may provide an indication of an automatic return line from HV to EV at which switching (or the automatic return) from the HV traveling mode to the EV traveling mode is performed. In the HV traveling mode, when the SOC increases to a value corresponding to the graduation  413   f , a change from the HV traveling mode to the EV traveling mode may be automatically performed. In one implementation of the technology, the automatic return line from HV to EV may serve as a “second sign”. 
     A region including the graduations  413   h  and  413   i  of the third group may provide an indication of a region that involves executing solely the HV traveling mode. 
     Here, the graduation  413   h  may provide an indication of an automatic switching line from EV to HV at which switching from the EV traveling mode to the HV traveling mode is performed. In the EV traveling mode, when the SOC decreases to a value corresponding to the graduation  413   h , a change from the EV traveling mode to the HV traveling mode may be automatically performed. In one implementation of the technology, the automatic switching line from EV to HV may serve as a “first sign”. 
     The combination meter  410  may include an undepicted indicator. The indicator may be adjacent to the pointer SOC meter  411 , and may provide an indication of whether the current traveling mode is the EV traveling mode or the HV traveling mode by, for instance, lighting and extinction of an icon. 
     The combination meter  410  may further include a predicted duration distance indicator. The predicted duration distance indicator may constantly indicate a predicted duration distance in the EV traveling mode and a predicted duration distance with combined use of the EV traveling mode and the HV traveling mode. 
     The MFD  420  may be an image display such as, but not limited to, an LCD. The MFD  420  may be disposed at a position to be viewed by a driver in a vehicle room. 
     The MFD  420  may include, for instance, a group of a number of pixels arranged in a matrix and variable in luminance and display colors, allowing any text or graphics to be displayed within its range of resolution. 
     The MFD  420  may be disposed, for instance, in a center region in a vehicle widthwise direction of the instrument panel and near an upper end of the instrument panel. 
     The MFD  420  may have, in part of its display region, a function of SOC indication that provides, for instance, bar graph display of the SOC in each of the EV traveling mode and the HV traveling mode. 
     The SOC indication on the MFD  420  may differ in indication modes as described below, depending on whether the EV traveling mode or the HV traveling mode is selected. 
       FIG. 3  illustrates the SOC indication, in the EV traveling mode, on the MFD in the SOC indicator according to the implementation. 
     The MFD  420  may provide the SOC indication in the form of a bar graph whose length is variable in accordance with an increase or a decrease of the SOC. The bar graph may be superimposed on an illustration  421  of a battery. 
     In the EV traveling mode, as illustrated in  FIG. 3 , a bar graph  422  of full segment display may be displayed. 
     The bar graph  422  of the full segment display illustrated in  FIG. 3  may be displayed in, for instance, a rectangular shape. An upper end of the bar graph  422  may be substantially continuously raised and lowered by one pixel of the group of the pixels included in the MFD  420 . 
     In accordance with the decrease in the SOC, the upper end of the bar graph  422  may be lowered, decreasing a length L of the bar graph  422 . 
       FIG. 3  illustrates a non-limiting example of the bar graph  422  with its upper end located on an upper end of a display range specified in advance. 
     At this occasion, the SOC of the battery  300  may be the practical upper limit (e.g. 85%) of the SOC use range in the EV traveling mode. 
     When the SOC decreases to reach the switching line from the EV traveling mode to the HV traveling mode (refer to  FIG. 5  to be described later), the length of the bar graph  422  may become substantially zero, and the bar graph  422  may disappear on the MFD  420 . In other words, only the illustration  421  may remain displayed on the MFD  420 . 
       FIG. 4  illustrates the SOC indication, in the HV traveling mode, on the MFD in the SOC indicator according to the implementation. 
     In the HV traveling mode, a plurality of (e.g. eight) segments  423   a  to  423   h  may be displayed in a sequential arrangement from top to bottom. The plurality of segments  423   a  to  423   h  may be superimposed on the illustration  421  of the battery. 
     In the HV traveling mode, the SOC may be indicated by the number of the segments displayed. 
     All of the segments  423   a  to  423   h  may be displayed near the SOC upper limit (the automatic return line from the EV traveling mode) in the HV traveling mode. As the SOC decreases, the segments  423   a  to  423   h  may disappear sequentially from the uppermost segment  423   a.    
     When the SOC becomes near the lower limit in the HV traveling mode, all the segments  423   a  to  423   h  may disappear. In other words, only the illustration  421  may remain displayed. 
     Here, the bar graph  422  of the full segment display and the segments  423   a  to  423   h  of the 8-segment display may be provided in different indication modes such as, but not limited to, colors and luminance. 
     For instance, the bar graph  422  may be displayed in green, and the segments  423   a  to  423   h  may be displayed in blue. 
     The hybrid integrated controller  240  may perform calculation processing of an SOC value for the full segment display at any time. The SOC value for the full segment display may be used in the pointer SOC meter  411  and in the full segment display in the MFD  420 . 
     The hybrid integrated controller  240  may also perform calculation processing of an SOC value for the 8-segment display. The SOC value for the 8-segment display may be used in the 8-segment display in the MFD  420 . 
     The calculated SOC values may be received and subjected to display processing by ECUs included in the pointer SOC meter  411  and in the MFD  420 . 
     The ECU of the MFD  420  may further receive a flag of determination on operation of the EV traveling mode and the HV traveling mode, and may perform switching between the full segment display (in the EV traveling mode) and the 8-segment display (in the HV traveling mode). The flag of determination on operation of the EV traveling mode and the HV traveling mode may be outputted from the hybrid integrated controller  240 . 
     Description is given below on SOC transition of the battery  300  and switching operation of traveling modes in accordance with a change in the SOC, in a hybrid vehicle according to an implementation. 
       FIG. 5  illustrates one instance of the SOC transition and switching operation of traveling modes, in the hybrid vehicle according to the implementation. 
     In  FIG. 5 , a vertical axis denotes the SOC of the battery  300 , and a horizontal axis denotes time. 
     In  FIG. 5 , the SOC may be, for instance, about 85% at a point A, corresponding to a practically full-charged state of the battery  300 . 
     When traveling in the EV traveling mode is started at the state of the point A, the SOC may gradually decrease in accordance with passage of traveling time, although the SOC may be temporality recovered by regenerative power generation, etc. Power consumption due to traveling, use of electrical components, or other factors may usually exceed an amount of the regenerative power generation in braking, or any other power generation. 
     When the SOC passes a point B and a point C sequentially, and decreases to a level of a point D, the hybrid integrated controller  240  may automatically perform switching from the EV traveling mode to the HV traveling mode. The point B may correspond to the automatic return line from HV to EV. The point C may correspond to the upper limit of an ordinary use range of HV. The point D may correspond to the automatic switching line from EV to HV. 
     The automatic switching line from EV to HV may be set in a region where, for instance, the SOC substantially coincides with SOC control center in the HV traveling mode. 
     The automatic return line from HV to EV may be set in a region where, for instance, the predicted duration distance in the EV traveling mode after the return to the EV traveling mode is equal to or larger than a prescribed value. 
     In the HV traveling mode, the hybrid integrated controller  240  may perform charge and discharge control to allow the SOC of the battery  300  to be between a level corresponding to the point C and a level corresponding to a point E. The point C may be the upper limit of the ordinary use range of HV. The point E may be a lower limit of the ordinary use range of HV. 
     There may be cases that the SOC falls below the lower limit of the ordinary use range of HV for some reason such as, but not limited to, insufficient opportunities of regenerative power generation. In such cases, when the SOC reaches a level corresponding to a point F as a motor-traveling unallowable level, motor traveling may become difficult. Further, when the SOC reaches a level corresponding to a point G as a lower limit of a battery use range, the hybrid integrated controller  240  may drive the motor generator  100  with use of the output of the engine  10  to allow for power generation, performing control to charge the battery  300  to prevent the SOC from further decreasing. 
       FIG. 6  illustrates one instance of transition of the SOC indication of the pointer SOC meter and the MFD in the SOC indicator according to the implementation. 
     In  FIG. 6 , columns A to G respectively correspond to the points A to G in  FIG. 5  as described above. 
     The pointer SOC meter  411  may maintain a common indication mode over all of the columns A to G, and may provide the SOC indication solely by a positional change or sway of the pointer  412 . 
     In a state of the column A, the pointer  412  may point the graduation  413   a  that indicates the full-charged state. 
     The pointer  412  may start here to turn counterclockwise in accordance with the decrease in the SOC. In a state of the column B, the pointer  412  may point the graduation  413   f  that indicates the automatic return line from the HV traveling mode to the EV traveling mode. 
     In a state of the column C, the pointer  412  may point the graduation  413   g  that indicates the upper limit of the ordinary use range of HV. 
     In a state of the column D, the pointer  412  may point the graduation  413   h  that indicates the automatic switching line from the EV traveling mode to the HV traveling mode. 
     At this occasion, a driver may forecast, based on how the pointer  412  comes close to the graduation  413   h , switching from the EV traveling mode to the HV traveling mode. 
     With a further decrease in the SOC, in states of the columns E and F, the pointer  412  may shift toward the graduation  413   i . In a state of the column G, the pointer  412  may point the graduation  413   i.    
     In a case of an increase of the SOC, the pointer  412  may turn clockwise to point a position corresponding to the current SOC. 
     The SOC indication on the MFD  420  in the state of the column A (in the EV traveling mode) may be the full segment display as illustrated in  FIG. 3 , where the length or height of the bar graph  422  may be at its maximum. 
     The length of the bar graph  422  may start here to decrease continuously with the decrease in the SOC. The bar graph  422  may disappear in the state of the column D as the automatic switching line from the EV traveling mode to the HV traveling mode. 
     In a case of automatic switching from the EV traveling mode to the HV traveling mode, prior to the switching, the bar graph  422  may be set to disappear for a prescribed period. 
     When switching from the EV traveling mode to the HV traveling mode is performed, the SOC indication on the MFD  420  may be changed to the 8-segment display illustrated in  FIG. 4 . 
     In the state of the column D, i.e. immediately after the switching to the HV traveling mode, the segments  423   e  to  423   h  may be displayed. At this occasion, the segments  423   a  to  423   d  may disappear. 
     When the SOC starts here to decrease, the segment  423   e  and the segment  423   f  may disappear sequentially. In the state of the column E, the segments  423   g  and  423   h  may be displayed. 
     With a further decrease in the SOC, in the state of the column F, the segment  423   g  may disappear, and the segment  423   h  may be displayed. 
     With a further decrease in the SOC, in the state of the column G, all of the segments  423   a  to  423   h  may disappear. 
     In the state of the column D, when the SOC increases due to regenerative power generation, etc., the segments  423   d ,  423   c ,  423   b , and  423   a  may be sequentially displayed. 
     In the state of the column C, the segments  423   c  to  423   h  may be displayed. 
     In the state of the column B as the automatic return line from the HV traveling mode to the EV traveling mode, all of the segments  423   a  to  423   h  may be displayed. 
     In a case of the automatic return (switching) from the HV traveling mode to the EV traveling mode, prior to the switching, all of the segments  423   a  to  423   h  may be set to be displayed for a prescribed period. 
     When the switching from the HV traveling mode to the EV traveling mode is performed, the SOC indication on the MFD  420  may be returned to the full segment display, and a lower part of the bar graph  422  with one-third of its length may be displayed. 
     As described above, according to the implementation, in the SOC indication on the MFD  420 , the SOC ranges directed to the EV traveling mode and the HV traveling mode are expanded to the entire display range of the bar graph  422 . Hence, it is possible to easily grasp the SOC transition in each traveling mode. 
     Moreover, in the EV traveling mode, the indication of the minimum of the bar graph  422  in which the bar graph  422  disappears means that a change to the HV traveling mode is about to be made immediately thereafter (after an elapse of predetermined time). In the HV traveling mode, the indication of the maximum of the segments  423   a  to  423   h  in which all of the segments  423   a  to  423   h  are displayed means that a change to the EV traveling mode is about to be made immediately thereafter (after an elapse of predetermined time). Hence, it is possible to easily grasp, based on the current indicator display, a possible timing of, for example, switching of traveling modes. 
     Moreover, providing the pointer SOC meter  411  makes it possible to easily grasp a relative state of the current SOC to total battery capacity, regardless of the indication state of the MFD  420 . 
     In addition, the pointer SOC meter  411  is provided with the graduation corresponding to the traveling-mode switching (return) line. Hence, also with the pointer SOC meter  411 , it is possible to easily grasp the switching of traveling modes. 
     As described above, according to the implementation, it is possible to provide an SOC indicator of a hybrid vehicle that allows for an intuitive grasp of a change of traveling modes in response to a change in SOC and SOC transition in each traveling mode. 
     (Modifications) 
     The technology is by no means limited to the implementations described above. The technology may be modified or altered in a variety of ways, and is intended to include such modifications and alterations. 
     First, configurations of a hybrid vehicle and an SOC indicator are not limited to the implementations described above, and may be modified as appropriate. 
     For instance, in the foregoing description, described is one implementation in which the vehicle is a plug-in hybrid vehicle having a plug-in charging function. However, the technology may be applied to a vehicle that has an EV traveling mode, i.e., a function of traveling with sole use of a motor generator without starting an engine, even when the vehicle has no plug-in charging function. 
     Also, the engine is not limited to a gasoline engine as described in the forgoing implementation. A diesel engine or any other internal combustion engine may be used. 
     Second, the pointer SOC meter in the forgoing implementation includes a mechanical pointer and a scale plate. Instead, an image corresponding to such a pointer SOC meter may be displayed on an image display such as, but not limited to, an LCD. 
     Also, in the forgoing implementation, the three regions are provided with graduations in the respective three colors. However, the intermediate region may be provided in gradation or in a separately-colored pattern in a plurality of colors. In this case, one end of the gradationed region, or one end of the separately-colored-patterned region may serve as the automatic switching line from EV to HV. Another end of the gradationed region, or another end of the separately-colored-patterned region may serve as the automatic return line from HV to EV. 
     Third, the SOC indication on the MFD in the forgoing implementation involves the full segment display in the EV traveling mode and the 8-segment display in the HV traveling mode. However, separate use of plural segment display and the full segment display is not limited to the forgoing implementation, and may be modified as appropriate. 
     For instance, the full segment display may be used in both the EV traveling mode and the HV traveling mode. Alternatively, the plural segment display may be used in both the EV traveling mode and the HV traveling mode. 
     Also, the number of segments in the plural segment display is not limited to eight as in the forgoing implementation. The number of segments may be increased or reduced as appropriate. 
     Although some preferred implementations of the technology have been described in the foregoing by way of example with reference to the accompanying drawings, the technology is by no means limited to the implementations described above. It should be appreciated that modifications and alterations may be made by persons skilled in the art without departing from the scope as defined by the appended claims. The technology is intended to include such modifications and alterations in so far as they fall within the scope of the appended claims or the equivalents thereof.