Patent Publication Number: US-2022219668-A1

Title: Vehicle control devices, vehicle control systems, and hybrid vehicles

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-002211 filed on Jan. 8, 2021, incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a vehicle control device, a vehicle control system, and a hybrid vehicle. 
     2. Description of Related Art 
     In a hybrid vehicle in which a battery can be charged with electromotive force generated by an engine, it is known a vehicle control device configured to, when it is determined that the vehicle is moving to a parking point where parking time is expected to be longer than predetermined time while driving by the engine, reduce a target charge rate of the battery and cause the vehicle to travel by electric power from a point preceding the parking point by a predetermined distance to reduce charge amount of the battery (for example, see Japanese Unexamined Patent Application Publication No. 2017-081416 (JP 2017-081416 A)). 
     SUMMARY 
     However, even when the hybrid vehicle travels by electric power from a point preceding a parking point, a battery charge rate may not be efficiently reduced to a target charge rate when the vehicle reaches the parking point depending on a travel state from the point preceding the parking point to the parking point. 
     According to aspects of the present disclosure, a vehicle control device, a vehicle control system, and a hybrid vehicle are provided. In the vehicle control device and the vehicle control system, the battery charge rate can be efficiently reduced to the target charge rate when the hybrid vehicle reaches the parking point. 
     An first aspect of the present disclosure relate to a vehicle control device configured to be mounted on a hybrid vehicle that is able to charge a battery with electric power generated by driving an engine. The vehicle control device includes a prediction unit configured to acquire position information of a parking point where parking time of the hybrid vehicle on a travel route is predicted to exceed a predetermined threshold value, a target setting unit configured to set a target charge rate of the battery and change the target charge rate to a second charge rate that is lower than a first charge rate in a normal state when the hybrid vehicle satisfies an approach condition that the hybrid vehicle approaches the parking point, and a battery control unit configured to control a charge and discharge amount of the battery such that a charge and discharge amount of the battery corresponding to the second charge rate when the target setting unit sets the target charge rate to the second charge rate is larger to a discharge side than a charge and discharge amount of the battery corresponding to the second charge rate in the normal state. 
     With the vehicle control device according to a first aspect, the charge and discharge amount of the battery corresponding to the second charge rate when the target setting unit sets the target charge rate to the second charge rate is larger to the discharge side than the charge and discharge amount of the battery corresponding to the second charge rate in the normal state. That is, electric energy (electric power) of the battery is consumed more actively. Therefore, when the hybrid vehicle reaches the parking point, the charge rate of the battery can be efficiently reduced to the target charge rate. 
     Further, the charge and discharge amount of the battery corresponding to the second charge rate when the target setting unit sets the target charge rate to the second charge rate may be set to an upper limit value of the charge and discharge amount of the battery corresponding to the second charge rate in the normal state. 
     With this configuration, the charge and discharge amount of the battery corresponding to the second charge rate when the target setting unit sets the target charge rate to the second charge rate is set to the upper limit value of the charge and discharge amount of the battery corresponding to the second charge rate in the normal state. Therefore, the electric energy of the battery is surely consumed. The “upper limit value” in the present disclosure includes a value that is equal to or less than the upper limit value and close to the upper limit value. 
     The upper limit value and a lower limit value of the charge and discharge amount of the battery in the normal state may be determined based on a charge capacity of the battery, a vehicle speed, and a driving characteristic. 
     With this configuration, the upper limit value and the lower limit value of the charge and discharge amount of the battery in the normal state are determined based on the charge capacity of the battery, the vehicle speed, and the driving characteristic. That is, in the normal state, the charge and discharge amount is controlled based on a traveling state (vehicle speed) and the driving characteristics of the hybrid vehicle. Therefore, even when the target setting unit sets the target charge rate to the second charge rate, the electric energy of the battery is consumed without deteriorating the battery. 
     Further, the approach condition may include a distance correction value set based on past data. 
     With this configuration, the approach condition includes the distance correction value set based on the past data. Therefore, when the hybrid vehicle reaches the parking point, the charge rate of the battery can be reduced more efficiently to the target charge rate than when the approach condition does not include the distance correction value. 
     Further, a charge and discharge amount correction value set based on the past data may be added to the charge and discharge amount of the battery corresponding to the second charge rate when the target setting unit sets the target charge rate to the second charge rate. 
     With this configuration, the charge and discharge amount correction value set based on the past data is added to the charge and discharge amount of the battery corresponding to the second charge rate when the target setting unit sets the target charge rate to the second charge rate. Therefore, when the hybrid vehicle reaches the parking point, the charge rate of the battery can be reduced more efficiently to the target charge rate than when the charge and discharge amount correction value is not added to the charge and discharge amount of the battery. 
     A second aspect of the present disclosure relates to a vehicle control system including the vehicle control device according to the first aspect, the vehicle control device being mounted on a hybrid vehicle, and an acquisition unit configured to be able to communicate with the vehicle control device and to acquire external information at the parking point. 
     With the vehicle control system according to the second aspect, the acquisition unit acquires the external information at the parking point. Therefore, when the hybrid vehicle reaches the parking point, the acquisition unit can efficiently reduce the battery charge rate of the battery to the target charge rate as compared with a case where the external information at the parking point is not acquired. 
     Further, a third aspect of the present disclosure relates to a hybrid vehicle including an engine, a battery that is able to be charged with electric power generated by driving the engine, a traction motor that is driven by the electric power charged in the battery, and the vehicle control device according to the first aspect. The vehicle control device is configured to cause the hybrid vehicle to travel by switching between driving by the engine and driving by the traction motor. 
     With the hybrid vehicle according to the third aspect, when the hybrid vehicle reaches the parking point, the charge rate of the battery can be efficiently reduced to the target charge rate as compared with a case where the vehicle control device is not provided. 
     As described above, according to the aspects of the present disclosure, when the hybrid vehicle reaches the parking point, the charge rate of the battery can be efficiently reduced to the target charge rate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein: 
         FIG. 1  is a block diagram showing a vehicle control device and a vehicle control system according to an embodiment; 
         FIG. 2  is a schematic diagram illustrating a method for charging in a cold state according to the embodiment; 
         FIG. 3  is a graph showing a relationship between an engine water temperature and an engine speed during warm-up operation of an engine when a state of charge (SOC) is high and low in the hybrid vehicle according to the embodiment; 
         FIG. 4  is a flowchart showing a control process according to a first embodiment; 
         FIG. 5  is a graph showing a charge/discharge amount of a battery with respect to the SOC according to the first embodiment; 
         FIG. 6  is a flowchart showing a control process according to a modification of the first embodiment; 
         FIG. 7  is a flowchart showing a control process according to a second embodiment; 
         FIG. 8  is a flowchart showing a control process according to a modification of the second embodiment; 
         FIG. 9  is a flowchart showing a control process according to a third embodiment; 
         FIG. 10  is a graph showing a charge/discharge amount of a battery with respect to the SOC according to the third embodiment; and 
         FIG. 11  is a flowchart showing a control process according to a modification of the third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the drawings. 
     First Embodiment 
     First, a first embodiment will be described. As shown in  FIG. 1 , a hybrid vehicle  10  is provided with an engine  12 , a battery (lithium ion secondary battery (storage battery))  16  capable of charging electric power (electric energy) generated by driving the engine  12 , a traction motor  14  that is driven by electric power charged in the battery  16 , a battery control unit  18  that controls a state of charge (hereinafter may be referred to as “SOC”) of the battery  16  by controlling the engine  12  and the traction motor  14 , and a vehicle control device  20  that is an electronic device. 
     That is, the hybrid vehicle  10  is configured to be able to travel while appropriately switching between two types of driving forces generated by the engine  12  and the motor  14 . Then, as described above, the engine  12  is driven not only for traveling but also for charging the battery  16 . The battery  16  can also be charged by regenerating the motor  14 . 
     The vehicle control device  20  includes a first control device  22  including an analysis unit  30 , a prediction unit  32 , a history information storage unit  34 , a recording unit  36 , and a target setting unit  38 , and a second control device  24  including a position detection unit  42  and a communication unit  44 . These are composed of an electronic control unit (ECU) and a software program executed on the ECU. The vehicle control device  20  is electrically connected to a sensor unit  26 , a car navigation system  28 , the engine  12 , the motor  14 , the battery  16 , and the battery control unit  18 . 
     The sensor unit  26  is configured to collect at least information on an external environment and a traveling locus (including a vehicle speed and a steering angle) of the hybrid vehicle  10 . The sensor unit  26  may include a steering angle sensor, a yaw rate sensor, a wheel pulse sensor, a radar, a direction indicator, and the like. 
     The analysis unit  30  is configured to acquire and process sensed information (hereinafter may be referred to as “primary information”) such as a current position, stop time, start time, a vehicle speed, etc. of the hybrid vehicle  10 , generate travel history information (hereinafter may be referred to as “secondary information”), and record the travel history information in the history information storage unit  34 . The stop time is time when the engine  12  is instructed to stop, and the start time is time when the engine  12  is instructed to start. 
     Further, the travel history information (secondary information) includes information on parking of the hybrid vehicle  10 , that is, information indicating parking date and time (time zone and day of a week), parking time, and a parking point (destination). Then, the analysis unit  30  is configured to predict one or more parking points (destinations) of the hybrid vehicle  10  based on the travel history information (secondary information) stored in the history information storage unit  34  and weather information stored in a weather information storage unit  52  to be described later. 
     The prediction unit  32  is configured to predict a travel route of the hybrid vehicle  10  based on information such as the vehicle speed and the steering angle collected in the sensor unit  26  and route setting information in the car navigation system  28 . Then, the prediction unit  32  is configured to acquire position information of a parking point (destination) where the parking time is expected to exceed a predetermined threshold value on the travel route of the hybrid vehicle  10  from among the one or more parking points (destinations) predicted by the analysis unit  30 , and set a point preceding the position by a predetermined distance α. 
     The history information storage unit  34  is configured to store the travel history information (secondary information) of the hybrid vehicle  10  based on vehicle identification (ID) of the hybrid vehicle  10 . The recording unit  36  is configured to record the primary information as appropriate. The target setting unit  38  is configured to set a target charge rate. 
     Here, a large change in the SOC in the battery  16  deteriorates the battery  16 . Therefore, an upper limit value CU and a lower limit value CD are set for the SOC (see  FIG. 2 ). That is, the battery  16  is controlled by the battery control unit  18  such that the SOC of the battery  16  falls within a range (allowable range) from the upper limit value CU to the lower limit value CD. 
     The position detection unit  42  is configured to acquire the current position (position information) of the hybrid vehicle  10  from the sensor unit  26  and the car navigation system  28 . The communication unit  44  periodically transmits information including the vehicle identification (ID) of the hybrid vehicle  10  to a management center  50  to be described later. The vehicle ID may be any information that can uniquely identify the hybrid vehicle  10 . 
     Further, a vehicle control system  40  is constructed by electrically connecting the vehicle control device  20  and the management center  50  via a communication network  46 . That is, each component of the vehicle control system  40  is realized by any combination of hardware and software based on a central processing unit (CPU) and a memory of any computer, a program loaded to the memory, a storage unit such as a hard disk for storing the program, and an interface for network connection. 
     The management center  50  is a server that communicates (transmits and receives information) with the vehicle control device  20 , and includes the weather information storage unit  52  as an acquisition unit and the communication unit  48 . The weather information storage unit  52  is configured to acquire weather information from the Japan Meteorological Agency as external information, and store the weather information indicating an expected temperature and the like of each location. The communication unit  48  is configured to periodically receive information from the vehicle control device  20 , and transmit the weather information stored in the weather information storage unit  52  to the vehicle control device  20 . 
     The hybrid vehicle  10  provided with the vehicle control device  20  described above actively drives the engine  12  for warming up the engine  12  at the time of starting the hybrid vehicle  10 . Traveling by the driving force generated by the engine, which also serves as warming up the engine as described above, is called “the engine running cold”. When the engine  12  is sufficiently warmed up (a period in which the engine runs cold is completed), the hybrid vehicle  10  travels while taking a balance between driving forces generated by the engine  12  and the motor  14 . 
     Further, in the hybrid vehicle  10 , the battery  16  is also charged simultaneously by rotating a power generation motor (not shown) with a part of the driving force of the engine  12  while the engine is running cold. Charging the battery  16  using the driving force of the engine  12  when the engine runs cold is called “charging in a cold state”, and a method for charging in a cold state will be described next. 
     As shown in  FIG. 2 , it is assumed that the hybrid vehicle  10  departs from a point S at time T 0 , reaches a point P 1  at time T 1 , reaches a point P 2  at time T 2 , and reaches a point G at time T 3 , for example. The point S is a starting point and the point G is a destination. Further, a section from the point S to the point P 1  is defined as a section in which the engine runs cold (hereinafter referred to as a “cold section”). 
     The upper part of  FIG. 2  shows a travel route of the hybrid vehicle  10 , and the lower part of  FIG. 2  shows a change in a SOC of the battery  16 . The SOC has a minimum value of 0% and a maximum value of 100%. The allowable range is set for the SOC. The allowable range is defined by the lower limit value CD and the upper limit value CU. For example, the lower limit value CD of the SOC is assumed to be about 40%, and the upper limit value CU of the SOC is assumed to be about 80%. 
     The target charge rate is set to, for example, about 65%. In the following, a first charge rate that is the target charge rate in the normal state is referred to as “basic target charge rate CM”. Therefore, the basic target charge rate CM in the embodiment is 65%. Based on the above, the method for charging in a cold state when the target charge rate is fixed to the basic target charge rate CM and a method for charging in a cold state when the target charge rate is variable will be described. 
     First, a case where the target charge rate is fixed to the basic target charge rate CM will be described. The target charge rate is fixed to the basic target charge rate CM between the lower limit value CD of the SOC and the upper limit value CU of the SOC. SOC-P 1  shown in  FIG. 2  shows a change in a charge/discharge amount when the target charge rate is the basic target charge rate CM. The charge/discharge amount for SOC-P 1  shown in  FIG. 2  is controlled to be maintained to the vicinity of the basic target charge rate CM. 
     As shown in  FIG. 2 , when the hybrid vehicle  10  starts at the point S, the hybrid vehicle  10  runs cold for a while, that is, the hybrid vehicle  10  runs with the driving force of the engine  12 . At this time, the engine  12  also rotates the power generation motor. Since the power generation motor functions as a generator, charging in a cold state can be performed. 
     Here, when the actual SOC is lower than the basic target charge rate CM that is the target charge rate, charging in a cold state is performed. However, in this case, since the SOC-P 1  of the hybrid vehicle  10  at time T 0  is close to the basic target charge rate CM, there is little effect of charging in a cold state. That is, when the hybrid vehicle  10  starts to run cold, there is little room for charging in a cold state since the actual SOC is already sufficiently large. 
     Next, a case where the target charge rate is variable will be described. When the target charge rate is variable, the target charge rate is also set to the basic target charge rate CM between the lower limit value CD of the SOC and the upper limit value CU of the SOC at the point S. This is the same as the case where the target charge rate is fixed to the basic target charge rate CM. However, the actual SOC in this case is reduced to the vicinity of the lower limit value CD. SOC-P 2  shown in  FIG. 2  shows a change in a charge/discharge amount at this time. The charge/discharge amount for SOC-P 2  shown in  FIG. 2  is also controlled to be maintained to the vicinity of the basic target charge rate CM. 
     As shown in  FIG. 2 , when the hybrid vehicle  10  starts at the point S, the SOC-P 2  increases, due to charging in a cold state, until SOC-P 2  reaches the basic target charge rate CM. That is, since the actual SOC at the time of starting the hybrid vehicle  10  is sufficiently lower than the basic target charge rate CM, there is a large effect of charging in a cold state (charging in a cold state is performed efficiently). 
     Further, since the engine  12  can be loaded by charging in a cold state, as shown in  FIG. 3 , there is a secondary effect in which the warming up of the engine  12  is promoted. That is, when the actual SOC at the time of starting the hybrid vehicle  10  is, for example, less than 50%, it is possible for the engine water temperature to reach a target temperature K (° C.) in a predetermined time J (for example, J is equal to several hundred seconds) or earlier than when the actual SOC at the time of starting the hybrid vehicle  10  is, for example, 50% or more, so that the cold section can be shortened (the engine  12  can be stopped early). 
     As described above, in order to enhance the effect of charging in a cold state (improve the utilization efficiency of charging in a cold state), the actual SOC needs to be sufficiently lowered when the hybrid vehicle  10  starts to run cold. Specifically, the actual SOC needs to be lowered compared with at least the target charge rate (basic target charge rate CM). Therefore, when the hybrid vehicle  10  restarts from the point G, it is desirable that the target charge rate be reduced to a second charge rate (hereinafter referred to as “special target charge rate”) that is the vicinity of the lower limit value CD (a charge/discharge amount is equal to the vicinity of zero: see  FIG. 5 ). 
     As a result, the effect of charging in a cold state can be enhanced when the hybrid vehicle  10  restarts from the point G. Further, warming up of the engine  12  is promoted due to charging in a cold state, so that the cold section can be shortened. As described above, the effect of charging in a cold state is enhanced, and the cold section is shortened, which lead to fuel saving (improvement of fuel efficiency). 
     It is necessary to accurately predict the point G (destination) in order for the target charge rate (target SOC) to be reduced to the special target charge rate when the hybrid vehicle  10  restarts from the point G. The prediction can be performed, for example, by a prediction model based on Bayesian statistics. 
     Specifically, the position detection unit  42  acquires the current position (position information) of the hybrid vehicle  10  from the sensor unit  26  and the car navigation system  28 . At this time, the analysis unit  30  acquires the vehicle speed, and when the hybrid vehicle  10  stops and starts, the analysis unit  30  also acquires the time when the hybrid vehicle  10  stops and starts. Then, the analysis unit  30  updates the travel history information (secondary information) stored in the history information storage unit  34 . 
     As a result, the travel history information (secondary information) of the hybrid vehicle  10  is accumulated in the history information storage unit  34 . When the analysis unit  30  detects parking of the hybrid vehicle  10 , traveling frequency from a previous parking point to a current parking point is updated. As a result, the travel route information is updated. Further, information sensed as the primary information is recorded in the recording unit  36 . 
     In addition, the analysis unit  30  predicts subsequent parking points based on prediction information on a travel route that is most likely to be selected based on the current position and the travel history information of the hybrid vehicle  10 . That is, the analysis unit  30  predicts one or more parking points as candidate sites for destinations. Further, the analysis unit  30  calculates expected arrival time when the hybrid vehicle  10  is expected to arrive at each candidate site. The expected arrival time can be calculated by an algorithm similar to the algorithm used by the car navigation system  28  or the like. 
     Then, the analysis unit  30  predicts parking time in each candidate site, and as shown in  FIG. 4 , predicts, as a destination, a candidate site that is expected to be parked for a long time (step S 11 ). The analysis unit  30  may correct the parking time according to an estimated temperature at expected arrival time when the hybrid vehicle  10  is expected to arrive at each candidate site, the estimated temperature being transmitted from the management center  50 . In the weather information storage unit  52  of the management center  50 , the estimated temperature of each location is stored as weather information. 
     The prediction unit  32  predicts the travel route based on a predicted destination and transit point, and sets the point P 2  at a point preceding the destination by a predetermined distance α. When the predicted destination and transit point are changed before the hybrid vehicle  10  reaches the destination, the prediction unit  32  resets the point P 2  as appropriate. 
     As described above, the hybrid vehicle  10  can predict the point G (destination) while traveling, and can set the point P 2  at a point preceding the point G (destination) by a predetermined distance α. When the point P 2  is set, the position detection unit  42  periodically detects the current position of the hybrid vehicle  10 , and the analysis unit  30  determines whether the hybrid vehicle  10  has reached the point P 2  (step S 12 ). 
     Then, when the analysis unit  30  determines that the hybrid vehicle  10  has actually reached the point P 2  (when the hybrid vehicle  10  satisfies an approach condition that the hybrid vehicle  10  approaches the parking point and satisfies a condition that a distance to the parking point is a or less in  FIG. 4 ), the target setting unit  38  reduces the target charge rate to the special target charge rate lower than the basic target charge rate CM. 
     As a result, after the point P 2 , the charge/discharge amount of the battery  16  is controlled to a discharge side by the battery control unit  18  such that the electric energy of the battery  16  is actively consumed. In the embodiment, however, the discharge amount of the charge/discharge amount of the battery  16  is forcibly specified such that the charge/discharge amount of the battery  16  can be efficiently controlled (step S 13 ). 
     For example,  FIG. 5  illustrates a case in which the target setting unit  38  sets the target charge rate to any charge rate (indicated by the point X). That is, in this case, the battery control unit  18  controls the battery  16  such that the charge/discharge amount of the battery  16  corresponding to the charge rate indicated by the point X (a part of the portion indicated by a range Y) is larger on the discharge side than an upper limit value Ym of the charge/discharge amount of the battery  16  corresponding to the charge rate indicated by the point X in a normal state (when the target setting unit  38  does not set the target charge rate to any charge rate). 
     More specifically, in the normal state, as shown by the solid line in  FIG. 5 , the battery  16  is controlled to the charge/discharge amount of the battery  16  corresponding to the battery charge rate indicated by the point X. The battery control unit  18  controls the battery  16  such that the upper limit value of the charge/discharge amount of the battery  16  on the discharge side is set to an upper limit value UL of the charge/discharge amount of the battery  16  on the discharge side (the portion indicated by the range Y) when the target setting unit  38  sets the target charge rate to any charge rate (indicated by the point X). 
     With such control, the electric energy of the battery  16  can be consumed more actively by the time the hybrid vehicle  10  reaches the point G (destination), and when the hybrid vehicle  10  reaches the point G, the actual charge rate (SOC) can be efficiently and surely reduced to the vicinity of a lower limit value CD shown in  FIG. 2  (the special target charge rate shown by the point A in  FIG. 5 ). 
     The “upper limit value UL” in the embodiment includes a value that is equal to or less than the upper limit value UL and close to the upper limit value UL. Further, in order to set the charge/discharge amount of the battery  16  corresponding to the special target charge rate indicated by the point A to the upper limit value UL, after the point P 2 , the electric energy of the battery  16  is not only preferentially used as the driving force of the traction motor  14  but used to charge an auxiliary battery (not shown), for example. 
     Further, loop processing by the vehicle control device  20  shown in  FIG. 4  is repeatedly executed at regular intervals, for example, every few seconds. Further, when parking for a long time is not expected and when the hybrid vehicle  10  does not reach the point P 2 , the control in the normal state is performed (step S 14 ). That is, as shown in  FIG. 5 , the charge/discharge amount of the battery  16  is controlled to be within a range between the upper limit value UL and the lower limit value DL at any charge rate indicated by, for example, the point X. 
     Further, the upper limit value UL and the lower limit value DL of the charge/discharge amount of the battery  16  in the normal state are determined based on a charge capacity of the battery  16 , a vehicle speed of the hybrid vehicle  10  (the number of rotations of a propeller shaft that transmits power generated by the engine  12  to wheels), and driving characteristics (such as accelerator operation amount, etc. of a driver, hereinafter referred to as a “request from a driver”). 
     That is, in the normal state, the charge/discharge amount is controlled based on not only the charge capacity of the battery  16  but also the traveling state (vehicle speed) and the driving characteristics (request from the driver) of the hybrid vehicle  10 . Therefore, even when the target setting unit  38  sets the target charge rate to the special target charge rate, the electric energy of the battery  16  can be consumed without deteriorating the battery  16 . 
     Further, instead of setting the point P 2  at the point preceding the destination by the predetermined distance α, the point P 2  may be set at a point where the hybrid vehicle  10  is located preceding the expected arrival time to the destination by predetermined time T (time T may be used instead of the distance α for the approach condition). In this case, as shown in  FIG. 6 , in step S 12 , the current time is periodically detected, and it is determined whether time taken to reach the parking point is equal to or less than the predetermined time T. Further, the approach condition may be determined not only based on the distance α or the time T but also based on the driving characteristics (request from the driver) and the like. 
     Further, since the communication information with the management center  50  is only the weather information, the charge/discharge amount of the battery  16  can be controlled in real time, and a risk of control failure due to communication interruption can be reduced. Further, when the communication information with the management center  50  includes information on other vehicles, congestion information and the like can be reflected to the charge/discharge control, so that the battery charge rate can reach the target charge rate accurately. 
     Second Embodiment 
     Next, a second embodiment will be described. In the second embodiment, as shown in  FIG. 7 , the condition of approaching the parking point includes a distance correction value β set based on data when the hybrid vehicle  10  was parked at the parking point. Specifically, first, as in the first embodiment, the analysis unit  30  predicts parking time at each candidate site, and predicts, as a destination, a candidate site that is expected to be parked for a long time (step S 21 ). 
     Then, the prediction unit  32  predicts the travel route based on a transition point and the destination, and sets the point P 2  at a point preceding the destination by a predetermined distance α. When the point P 2  is set, the position detection unit  42  periodically detects the current position of the hybrid vehicle  10 , and the analysis unit  30  determines whether the hybrid vehicle  10  has reached the point P 2  (step S 22 ). 
     When the analysis unit  30  determines that the hybrid vehicle  10  has actually reached the point P 2 , the target setting unit  38  reduces the target charge rate to the special target charge rate lower than the basic target charge rate CM. As a result, after the point P 2 , the charge/discharge amount of the battery  16  is controlled by the battery control unit  18  such that the electric energy of the battery  16  is consumed more actively. That is, the charge/discharge amount of the battery  16  is forcibly specified (step S 23 ). 
     Here, for example, when downward slopes continue around the destination, when the engine  12  continues to be driven due to a request for cooling or heating around the destination, when a request load from a driver is high (a vehicle speed that continuously requires the driving force of the engine  12 , sudden acceleration) and the like, the SOC of the battery  16  is hardly reduced. On the other hand, when upward slopes continue around the destination, the vehicle frequently stops due to traffic congestion around the destination, a request load from a driver is low (a vehicle speed and acceleration that allow the vehicle to continuously travel with a driving force generated by electric energy) and the like, the SOC of the battery  16  is extremely reduced. 
     Therefore, in such a case, an average value of an actual charge/discharge balance is calculated from the actual charge/discharge balance after switching the charge/discharge amount (setting the charge/discharge amount to the upper limit value UL), the charge/discharge balance being recorded for each destination where the hybrid vehicle  10  was parked (step S 24 ). Then, the distance correction value β is calculated based on a difference between a target balance set in advance based on the amount of charge to be reduced before the hybrid vehicle  10  reaches the destination and the actual balance derived from the average value (step S 25 ). 
     After calculating the distance correction value β as described above, the routine returns to step S 22  and the calculated distance correction value β is reflected to the distance c that is used as a reference for issuing an instruction for switching the charge/discharge amount. That is, in step S 22 , it is determined whether the distance to the parking point is equal to or less than a value obtained by adding the distance c and the distance correction value β. When the SOC is hardly reduced, the charge/discharge amount may be switched at an early timing. When the SOC is extremely reduced, the charge/discharge amount may be switched at a late timing. 
     According to the second embodiment, when the hybrid vehicle  10  reaches the parking point, the charge rate of the battery  16  can be reduced to the target charge rate more efficiently and surely than when the distance correction value β is not included in the approach condition. Further, when parking for a long time is not expected and when the hybrid vehicle  10  does not reach the point P 2 , as in the first embodiment, the control in the normal state is performed (step S 26 ). 
     Further, as shown in  FIG. 8 , in step S 84 , the average value may be calculated from the SOC when the hybrid vehicle  10  reached the destination, the SOC being recorded for each destination where the hybrid vehicle  10  was parked, instead of calculating the average value from the charge/discharge balance after switching the charge/discharge amount recorded for each destination where the hybrid vehicle  10  was parked. Then, in step S 25 , the distance correction value β may be calculated based on the difference between the target SOC (special target charge rate) and the actual SOC derived from the average value. 
     Third Embodiment 
     Next, a third embodiment will be described. In the third embodiment, as shown in  FIG. 9 , a charge/discharge amount correction value γ set based on the data when the hybrid vehicle  10  was parked at the parking point is added to the charge/discharge amount that is set to the upper limit value UL. Specifically, first, as in the first embodiment, the analysis unit  30  predicts parking time at each candidate site, and predicts, as a destination, a candidate site that is expected to be parked for a long time (step S 31 ). 
     Then, the prediction unit  32  predicts a travel route based on a transition point and the destination, and sets the point P 2  at a point preceding the destination by a predetermined distance α. When the point P 2  is set, the position detection unit  42  periodically detects the current position of the hybrid vehicle  10 , and the analysis unit  30  determines whether the hybrid vehicle  10  has reached the point P 2  (step S 32 ). 
     When the analysis unit  30  determines that the hybrid vehicle  10  has actually reached the point P 2 , the target setting unit  38  reduces the target charge rate to the special target charge rate lower than the basic target charge rate CM. As a result, after the point P 2 , the charge/discharge amount of the battery  16  is controlled by the battery control unit  18  such that the electric energy of the battery  16  is consumed more actively. That is, the charge/discharge amount of the battery  16  is forcibly specified (step S 33 ). 
     Here, as in the second embodiment, an average value is calculated from the actual charge/discharge balance after switching the charge/discharge amount (setting the charge/discharge amount to the upper limit value UL), the charge/discharge balance being recorded for each destination where the hybrid vehicle  10  was parked (step S 34 ). Then, the charge/discharge amount correction value γ is calculated based on a difference between a target balance set in advance based on the amount of charge to be reduced before the hybrid vehicle  10  reaches the destination and the actual balance derived from the average value (step S 35 ). 
     After calculating the charge/discharge amount correction value γ as described above, the routine returns to step S 33  and the charge/discharge amount correction value γ is reflected to the switched charge/discharge amount (the charge/discharge amount that is set to the upper limit value UL) (the charge/discharge amount correction value γ is added to the switched charge/discharge amount). When the SOC is hardly reduced, the discharge amount is increased, and when the SOC is extremely reduced, the discharge amount is reduced. That is, as shown in  FIG. 10 , the charge/discharge amount is adjusted to the vicinity of the upper limit value UL of the charge/discharge amount. 
     According to the third embodiment, when the hybrid vehicle  10  reaches the parking point, the charge rate of the battery  16  can be reduced to the target charge rate more efficiently and surely than when the charge/discharge amount correction value γ is not added to the charge/discharge amount that is set to the upper limit value UL. Further, when parking for a long time is not expected and when the hybrid vehicle  10  does not reach the point P 2 , as in the first embodiment, the control in the normal state is performed (step S 36 ). 
     Further, as shown in  FIG. 11 , in step S 114 , the average value may be calculated from the SOC when the hybrid vehicle  10  reached the destination, the SOC being recorded for each destination where the hybrid vehicle  10  was parked, instead of calculating the average value from the charge/discharge balance after switching the charge/discharge amount recorded for each destination where the hybrid vehicle  10  was parked. Then, in step S 35 , the charge/discharge amount correction value γ may be calculated based on the difference between the target SOC (special target charge rate) and the actual SOC derived from the average value. 
     The vehicle control device  20 , the vehicle control system  40 , and the hybrid vehicle  10  according to the embodiment have been described above with reference to the drawings, but the vehicle control device  20 , the vehicle control system  40 , and the hybrid vehicle  10  according to the embodiment are not limited to the illustrated embodiments and design thereof can be changed as appropriate within the scope of the present disclosure. For example, the Global Positioning System (GPS) function may be used instead of the car navigation system  28 . 
     Further, an analysis function, which has been included in the vehicle control device  20 , may be built in the management center  50  in the vehicle control system  40 . That is, the management center  50  may include the analysis unit  30  and the history information storage unit  34 . Accordingly, the specifications of the arithmetic processing device on the hybrid vehicle  10  side can be lowered. 
     Further, when external information is used in the management center  50 , there are following two forms in which all the data are transmitted to the hybrid vehicle  10  side and then the hybrid vehicle  10  side makes a determination, and the management center  50  makes a determination and then only the command is transmitted to the hybrid vehicle  10  side. The latter form allows the arithmetic load on the hybrid vehicle  10  side to be reduced.