Patent Publication Number: US-2021188116-A1

Title: Vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2019-229539 filed on Dec. 19, 2019, incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a vehicle having a replaceable battery pack mounted thereon. 
     2. Description of Related Art 
     Japanese Unexamined Patent Application Publication No. 2019-156007 (JP 2019-156007 A) discloses a control device that controls input power of a secondary battery mounted on a vehicle by using a power upper limit value (W) indicating an upper limit value of the input power of the secondary battery. 
     SUMMARY 
     Recently, an electrically driven vehicle (for example, an electric vehicle or a hybrid vehicle) that uses a secondary battery as a power source has become popular. In the electrically driven vehicle, when the capacity or performance of the secondary battery is reduced due to deterioration, or the like, of the battery, replacing the secondary battery mounted on the electrically driven vehicle can be considered. 
     A secondary battery is generally mounted on a vehicle in a form of a battery pack. The battery pack includes a secondary battery, a sensor that detects a state (for example, current, voltage, and temperature) of the secondary battery, and a control device. Hereinafter, the control device and the sensor included in the battery pack are sometimes referred to as a “battery ECU” and a “battery sensor”, respectively. Peripheral devices (for example, a control device and a sensor) appropriate for the secondary battery are mounted on the battery pack. The battery pack is maintained such that the secondary battery and the peripheral devices thereof normally operate. For this reason, when the secondary battery mounted on the vehicle is replaced, it is considered desirable that the entire battery pack mounted on the vehicle as well as the secondary battery be replaced for the purpose of vehicle maintenance. 
     As described in JP 2019-156007 A, the control device which is mounted on the vehicle separately from a battery pack and controls input power of the secondary battery by using the power upper limit value is well-known. The control device is configured to execute a power-based input limitation. The power-based input limitation is a process for controlling the input power of the secondary battery such that the input power of the secondary battery does not exceed the power upper limit value. Generally, on a vehicle that employs a control device executing the power-based input limitation, a battery pack including a battery ECU which obtains the power upper limit value using a detection value of a battery sensor is mounted. 
     When such a battery pack is replaced, a configuration may be considered in which a control device that relays communication is provided separately for enabling communication between the replacement battery pack and a control device of the vehicle after the replacement. In a vehicle having such a configuration, in a case where prescribed information exchanged during communication is stored in a separately provided control device, for example, when a defect, such as the temperature of the secondary battery rising higher than expected, occurs, the separately provided control device needs to be installed such that the control device is not influenced by heat generated in the battery pack. 
     The present disclosure provides a vehicle having a replaceable battery pack mounted thereon, in which a control device that relays communication between the battery pack and a control device of the vehicle is installed at an appropriate position. 
     A vehicle according to one aspect of the present disclosure includes a battery pack including a secondary battery, a first battery sensor configured to detect a state of the secondary battery, and a first electronic control device, a second electronic control device including a storage device that stores prescribed information acquired from the battery pack, and a third electronic control device provided separately from the battery pack and the second electronic control device and configured to control any one of battery power and battery current of the secondary battery as a control target. The second electronic control device is installed at a position outside the battery pack. The second electronic control device is configured to relay communication between the first electronic control device and the third electronic control device. 
     In such a manner, since the second electronic control device is installed at a position outside the battery pack, it is possible to prevent the second electronic control device from being influenced by the heat generated when a defect occurs in the battery pack. Therefore, it is possible to protect a storage device that stores the prescribed information acquired from the battery pack in which a defect has occurred. 
     In the above aspect, the second electronic control device may be installed at a position not immediately above the battery pack in the vehicle. 
     The influence of the heat generated when a defect occurs in the battery pack is greater at a position immediately above the battery pack in the vehicle than at the position not immediately above the battery pack. Therefore, by providing the second electronic control device at the position not immediately above the battery pack, it is possible to prevent the second electronic control device from being influenced by the heat generated when a defect occurs in the battery pack. 
     In the above aspect, the battery pack may be installed outside a cabin of the vehicle. The second electronic control device may be installed inside the cabin of the vehicle. 
     In such a manner, since the heat generated when a defect occurs in the battery pack outside the cabin of the vehicle is less likely to be transferred by the cabin of the vehicle, it is possible to prevent the second electronic control device from being influenced by the heat generated when a defect occurs in the battery pack. 
     In the above aspect, the second electronic control device may be installed in a state of being covered with a thermal insulation material. 
     In such a manner, since the heat generated when a defect occurs in the battery pack is less likely to be transferred by the thermal insulation material, it is possible to prevent the second electronic control device from being influenced by the heat generated when a defect occurs in the battery pack. 
     In the above aspect, the second electronic control device may store, in the storage device, history information on information exchanged between the first electronic control device and the third electronic control device. 
     In such a manner, the storage device of the second electronic control device that relays communication between the first electronic control device and the third electronic control device stores the history information on the information exchanged between the first electronic control device and the third electronic control device. Therefore, when any defect related to the control of the battery power occurs during use of the battery pack, it is possible to easily separate a cause of the defect in the battery pack from a cause of the defect in the vehicle using the stored history information. 
     In the above aspect, the second electronic control device may store, in the storage device, the history information in a latest predetermined period. 
     In such a manner, it is possible to store the history information in the storage device without unnecessarily increasing a storage capacity of the storage device. 
     In the above aspect, the first electronic control device may calculate a first limit value for the other one of the battery power and the battery current, using a detection value of the first battery sensor. The second electronic control device may convert the first limit value calculated by the first electronic control device into a second limit value corresponding to the control target. The third electronic control device may control the control target, using the second limit value. 
     In such a manner, the first limit value calculated by the first electronic control device is converted into the second limit value by the second electronic control device, such that the third electronic control device controls any one of the battery power and the battery current of the secondary battery as a control target without changing a configuration of the third electronic control device. 
     With the foregoing aspect of the present disclosure, it is possible to provide a vehicle having a replaceable battery pack mounted thereon, in which a control device that relays communication between the battery pack and a control device of the vehicle is installed at an appropriate position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the present disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein: 
         FIG. 1  is a diagram illustrating a configuration of an electrically driven vehicle according to an embodiment of the present disclosure; 
         FIG. 2  is a diagram illustrating a connection state of each control device included in the vehicle according to the embodiment of the present disclosure; 
         FIG. 3  is a diagram illustrating an example of a map used for determining target battery power; 
         FIG. 4  is a diagram illustrating detailed configurations of a battery pack, an HVECU, and a gate ECU; 
         FIG. 5  is a diagram illustrating an example of a position of a gate ECU viewed from above the vehicle; 
         FIG. 6  is a diagram illustrating an example of a position of the gate ECU inside a cabin of the vehicle; and 
         FIG. 7  is a diagram illustrating an example of a position of the gate ECU viewed from a side of the vehicle. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts will be denoted by the like signs, and description thereof will not be repeated. Hereinbelow, an electronic control unit is also referred to as an “ECU”. 
       FIG. 1  is a diagram illustrating a configuration of an electrically driven vehicle (hereinafter, referred to as a “vehicle”)  100  according to an embodiment of the present disclosure. In the present embodiment, it is assumed that the vehicle  100  is a front-wheel drive four-wheel vehicle (more specifically, a hybrid vehicle), but the number of wheels and a drive method can be appropriately changed. For example, the drive method may be rear-wheel drive or four-wheel drive. 
     Referring to  FIG. 1 , a battery pack  10  including a battery ECU  13  is mounted on the vehicle  100 . Further, separate from the battery pack  10 , a motor ECU  23 , an engine ECU  33 , an HVECU  50 , and a gate ECU  60  are mounted on the vehicle  100 . In the present embodiment, the battery ECU  13 , the gate ECU  60 , and the HVECU  50  respectively correspond to examples of a “first control device”, a “second control device”, and a “third control device”, according to the present disclosure. 
     The battery pack  10  includes a battery  11 , a voltage sensor  12   a , a current sensor  12   b , a temperature sensor  12   c , a battery ECU  13 , and a system main relay (SMR)  14 . The battery  11  functions as a secondary battery. In the present embodiment, an assembled battery including a plurality of electrically connected lithium-ion batteries is employed as the battery  11 . Each secondary battery that composes the assembled battery is also referred to as a “cell”. In the present embodiment, each lithium-ion battery that composes the battery  11  corresponds to the “cell”. Moreover, the secondary battery included in the battery pack  10  is not limited to the lithium-ion battery, and may be a different type of secondary battery (for example, a nickel-hydrogen battery). An electrolytic solution type of secondary battery or an all-solid-state type of secondary battery may be employed as the secondary battery. 
     The voltage sensor  12   a  detects voltage of each cell of the battery  11 . The current sensor  12   b  detects current flowing through the battery  11  (the charging side is negative). The temperature sensor  12   c  detects the temperature of each cell of the battery  11 . Each sensor outputs the detection result to the battery ECU  13 . The current sensor  12   b  is provided on a current path of the battery  11 . In the present embodiment, one voltage sensor  12   a  and one temperature sensor  12   c  are provided in each cell. However, an applicable embodiment of the present disclosure is not limited thereto, and one voltage sensor  12   a  and one temperature sensor  12   c  may be provided for each of a plurality of cells, or for one assembled battery. Hereinafter, the voltage sensor  12   a , the current sensor  12   b , and the temperature sensor  12   c  are collectively referred to as a “battery sensor  12 ”. The battery sensor  12  may be a battery management system (BMS) that further has, in addition to the above sensor functions, a state of charge (SOC) estimation function, a state of health (SOH) estimation function, a cell voltage equalization function, a diagnosis function, and a communication function. 
     The SMR  14  is configured to switch between connection and disconnection of a power path that connects external connection terminals T 1 , T 2  of the battery pack  10  to the battery  11 . As the SMR  14 , for example, an electromagnetic mechanical relay can be employed. In the present embodiment, a power control unit (PCU)  24  is connected to the external connection terminals T 1 , T 2  of the battery pack  10 . The battery  11  is connected to the PCU  24  via the SMR  14 . When the SMR  14  is in a closed state (a connection state), power can be exchanged between the battery  11  and the PCU  24 . On the other hand, when the SMR  14  is in an open state (a disconnection state), a power path that connects the battery  11  to the PCU  24  is disconnected. In the present embodiment, the SMR  14  is controlled by the battery ECU  13 . The battery ECU  13  controls the SMR  14  according to an instruction from the HVECU  50 . The SMR  14  is in the closed state (the connection state) during, for example, traveling of the vehicle  100 . 
     The vehicle  100  includes, as power sources used for traveling, an engine  31 , a first motor generator  21   a  (hereinafter, referred to as an “MG  21   a ”), and a second motor generator  21   b  (hereinafter, referred to as an “MG  21   b ”). Each of the MGs  21   a ,  21   b  is a motor generator functioning both as a motor that outputs torque using supplied drive power and as a generator that generates power using supplied torque. An alternating current motor (for example, a permanent magnet synchronous motor or an induction motor) is used as each of the MGs  21   a ,  21   b . Each of the MGs  21   a ,  21   b  is electrically connected to the battery  11  via the PCU  24 . The MGs  21   a ,  21   b  have rotor shafts  42   a ,  42   b , respectively. The rotor shafts  42   a ,  42   b  correspond to rotation shafts of the MGs  21   a ,  21   b , respectively. 
     The vehicle  100  further includes a single-pinion type of planetary gear  42 . Each of an output shaft  41  of the engine  31  and the rotor shaft  42   a  of the MG  21   a  is connected to the planetary gear  42 . The engine  31  may be, for example, a spark-ignition type of internal combustion engine including a plurality of cylinders (for example, four cylinders). The engine  31  generates power by burning fuel in each cylinder, and rotates a crankshaft (not shown) common to all the cylinders, using the generated power. The crankshaft of the engine  31  is connected to the output shaft  41  via a torsional damper (not shown). The output shaft  41  rotates by the rotation of the crankshaft. 
     The planetary gear  42  has three rotation elements, that is, an input element, an output element, and a reaction element. More specifically, the planetary gear  42  includes a sun gear, a ring gear that is arranged coaxially with the sun gear, a pinion gear that meshes with the sun gear and the ring gear, and a carrier that rotatably and revolvably holds the pinion gear. The carrier corresponds to the input element, the ring gear corresponds to the output element, and the sun gear corresponds to the reaction element. 
     Each of the engine  31  and the MG  21   a  is mechanically connected to drive wheels  45   a ,  45   b  via the planetary gear  42 . The output shaft  41  of the engine  31  is connected to the carrier of the planetary gear  42 . The rotor shaft  42   a  of the MG  21   a  is connected to the sun gear of the planetary gear  42 . Torque output from the engine  31  is input to the carrier. The planetary gear  42  is configured to divide the torque output from the engine  31  to the output shaft  41  into two parts, and deliver the two parts to the sun gear (further, to the MG  21   a ) and to the ring gear, respectively. When the torque output from the engine  31  is output to the ring gear, reaction torque caused by the MG  21   a  acts on the sun gear. 
     The planetary gear  42  and the MG  21   b  are configured such that power output from the planetary gear  42  and power output from the MG  21   b  are combined and delivered to the drive wheels  45   a ,  45   b . More specifically, an output gear (not shown) that meshes with a driven gear  43  is attached to the ring gear of the planetary gear  42 . In addition, a drive gear (not shown) attached to the rotor shaft  42   b  of the MG  21   b  also meshes with the driven gear  43 . The driven gear  43  acts to combine torque output from the MG  21   b  to the rotor shaft  42   b  and torque output from the ring gear of the planetary gear  42 . The driving torque combined in the above manner is delivered to a differential gear  44 , and further delivered to the drive wheels  45   a ,  45   b  via drive shafts  44   a ,  44   b  extending from the differential gear  44  to the right and left sides. The transmission  4  is composed of MGs  21   a ,  21   b , the planetary gear  42 , the rotor shafts  42   a ,  42   b , the driven gear  43 , and the differential gear  44  that are described above. 
     The MGs  21   a ,  21   b  are provided with motor sensors  22   a ,  22   b , respectively, which detect states (for example, current, voltage, temperature, and rotation speed) of the MGs  21   a ,  21   b . Each of the motor sensors  22   a ,  22   b  outputs the detection result to the motor ECU  23 . The engine  31  is provided with an engine sensor  32  which detects a state (for example, an intake air amount, an intake pressure, an intake temperature, an exhaust pressure, an exhaust temperature, a catalyst temperature, an engine coolant temperature, and rotation speed) of the engine  31 . The engine sensor  32  outputs the detection result to the engine ECU  33 . 
     The HVECU  50  is configured to output, to the engine ECU  33 , a command (a control command) for controlling the engine  31 . The engine ECU  33  is configured to control various actuators (for example, a throttle valve, an ignition device, and an injector (neither shown)) of the engine  31  according to the command from the HVECU  50 . The HVECU  50  can execute engine control via the engine ECU  33 . 
     The HVECU  50  is configured to output, to the motor ECU  23 , a command (a control command) for controlling each of the MGs  21   a ,  21   b . The motor ECU  23  is configured to generate a current signal (for example, a signal indicating the magnitude and frequency of the current) corresponding to target torque of each of the MGs  21   a ,  21   b  according to the command from the HVECU  50 , and output the generated current signal to the PCU  24 . The HVECU  50  can execute motor control via the motor ECU  23 . 
     The PCU  24  includes, for example, two inverters provided corresponding to the MGs  21   a ,  21   b , and converters arranged between each inverter and the battery  11 . The PCU  24  is configured to supply power accumulated in the battery  11  to each of the MGs  21   a ,  21   b , and supply power generated by each of the MGs  21   a ,  21   b  to the battery  11 . The PCU  24  is configured to separately control states of the MGs  21   a ,  21   b . For example, the PCU  24  can set the MG  21   b  to a powering state while setting the MG  21   a  to a regenerative state (that is, a power generation state). The PCU  24  is configured to supply power generated by one of the MGs  21   a ,  21   b  to the other. In other words, the MG  21   a  and the MG  21   b  are configured to exchange power between each other. 
     The vehicle  100  is configured to execute hybrid vehicle (HV) traveling and electric vehicle (EV) traveling. The HV traveling is executed by the engine  31  and the MG  21   b  while the engine  31  generates a traveling driving force. The EV traveling is executed by the MG  21   b  while the engine  31  is stopped. When the engine  31  is stopped, combustion in each cylinder is stopped. When the combustion in each cylinder is stopped, the engine  31  does not generate combustion energy (further, a traveling driving force of the vehicle). The HVECU  50  is configured to switch between the EV traveling and the HV traveling depending on the situation. 
       FIG. 2  is a diagram illustrating a connection state of each control device included in the vehicle  100  according to the embodiment of the present disclosure. Referring to  FIG. 2 , the vehicle  100  includes a local bus B 1  and a global bus B 2 . Each of the local bus B 1  and the global bus B 2  may be, for example, a controller area network (CAN) bus. 
     The battery ECU  13 , the motor ECU  23 , and the engine ECU  33  are connected to the local bus B 1 . Although not shown in  FIG. 2 , for example, a human-machine interface (HMI) control device is connected to the global bus B 2 . Examples of the HMI control device include a control device that controls a navigation system or a meter panel. In addition, the global bus B 2  is connected to another global bus via a central gateway (CGW, not shown). 
     The HVECU  50  is connected to the global bus B 2 . The HVECU  50  is configured to execute CAN communication with each control device connected to the global bus B 2 . Further, the HVECU  50  is connected to the local bus B 1  via the gate ECU  60 . The gate ECU  60  is configured to relay communication between the HVECU  50  and each control device (for example, the battery ECU  13 , the motor ECU  23 , and the engine ECU  33 ) connected to the local bus B 1 . The HVECU  50  is configured to execute the CAN communication with each control device connected to the local bus B 1  via the gate ECU  60 . As described above, in the present embodiment, a vehicle control system is composed of each control device connected to the local bus B 1 . 
     In the present embodiment, a microcomputer is employed as each of the battery ECU  13 , the motor ECU  23 , the engine ECU  33 , the HVECU  50 , and the gate ECU  60 . The battery ECU  13 , the motor ECU  23 , the engine ECU  33 , the HVECU  50 , and the gate ECU  60  include processors  13   a ,  23   a ,  33   a ,  50   a ,  60   a , random access memories (RAM)  13   b ,  23   b ,  33   b ,  50   b ,  60   b , storage devices  13   c ,  23   c ,  33   c ,  50   c ,  60   c , and communication interfaces (I/Fs)  13   d ,  23   d ,  33   d ,  50   d ,  60   d , respectively. For example, a central processing unit (CPU) can be employed as each processor. Each communication I/F includes a CAN controller. The RAM functions as a working memory that temporarily stores data processed by the processor. Each storage device is configured to store prescribed information. Each storage device includes, for example, a read-only memory (ROM) and a rewritable non-volatile memory (for example, an electrically erasable programmable read-only memory (EEPROM) and a data flash memory). In addition to a program, each storage device stores information (for example, maps, mathematical expressions, and various parameters) used in the program. When the processors respectively execute the programs stored in the storage devices, various controls of the vehicle are executed. However, an applicable embodiment of the present disclosure is not limited thereto, and the various controls may be executed by dedicated hardware (an electronic circuit). The number of processors included in each ECU is also optional, and any ECU may include a plurality of processors. 
     Returning to  FIG. 1 , charging/discharging control of the battery  11  will be described. Hereinafter, input power of the battery  11  and output power of the battery  11  are collectively referred to as “battery power”. The HVECU  50  determines target battery power using the SOC of the battery  11 . Then, the HVECU  50  controls the charging/discharging of the battery  11  such that the battery power is close to the target battery power. However, such charging/discharging control of the battery  11  is restricted by input and output limitations to be described below. Hereinafter, target battery power on the charging side (the input side) may be sometimes referred to as “target input power”, and target battery power on the discharging side (the output side) may be sometimes referred to as “target output power”. In the present embodiment, the power on the discharging side is represented by a positive sign (+) and the power on the charging side is represented by a negative sign (−). However, when comparing the magnitude of power, the absolute value is used regardless of the sign (+/−). In other words, power of which a value is closer to zero is smaller. When an upper limit value and a lower limit value for power are set, the upper limit value is positioned on the side where the absolute value of power is greater, and the lower limit value is positioned on the side where the absolute value of power is smaller. When power exceeds the upper limit value on the positive side, it means that the power becomes greater than the upper limit value on the positive side (that is, farther away from zero on the positive side). When power exceeds the upper limit value on the negative side, it means that the power becomes greater than the upper limit value on the negative side (that is, farther away from zero on the negative side). The SOC indicates a remaining charge amount and represents, for example, a ratio of a current charge amount to a charge amount in a fully charged state by 0% to 100%. As a method of measuring the SOC, a well-known method, such as a current integration method and an OCV estimation method, can be employed. 
       FIG. 3  is a diagram illustrating an example of a map used for determining the target battery power. In  FIG. 3 , a reference value C 0  represents an SOC control center value, a power value P A  represents an upper limit value of the target input power, and a power value P B  represents an upper limit value of the target output power. By referring to a map illustrated in  FIG. 3  together with  FIG. 1 , when the SOC of the battery  11  is the reference value C 0 , the target battery power becomes zero and the charging/discharging of the battery  11  is not executed. In a region (a region of excessive discharging) where the SOC of the battery  11  is smaller than the reference value C 0 , the target input power increases as the SOC of the battery  11  decreases until the target input power reaches the upper limit value (the power value P A ). On the other hand, in a region (a region of excessive charging) where the SOC of the battery  11  is greater than the reference value C 0 , the target output power increases as the SOC of the battery  11  increases until the target output power reaches the upper limit value (the power value P B ). When the HVECU  50  determines the target battery power according to the map illustrated in  FIG. 3  and executes the charging/discharging of the battery  11  such that the battery power becomes close to the determined target battery power, the SOC of the battery  11  can become close to the reference value C 0 . The reference value C 0  of the SOC may be fixed or variable depending on the situation of the vehicle  100 . 
     The HVECU  50  is configured to provide input and output limitations of the battery  11  using the battery ECU  13  and the gate ECU  60 . The HVECU  50  sets the upper limit value W in  of the input power of the battery  11  and the upper limit value W out  of the output power of the battery  11 , and controls the battery power such that the battery power does not exceed the set W in  and W out . The HVECU  50  adjusts the battery power by controlling the engine  31  and the PCU  24 . When the W in  or the W out  is smaller than the target battery power (that is, close to zero), the battery power is controlled such that the battery power does not exceed the W in  or the W out , instead of the target battery power. 
     The battery ECU  13  is configured to set an upper limit value IW in  of input current of the battery  11  using a detection value of the battery sensor  12 . The battery ECU  13  is also configured to set an upper limit value IW out  of output current of the battery  11  using the detection value of the battery sensor  12 . Meanwhile, the HVECU  50  is configured to control the input power of the battery  11  using the W in . The HVECU  50  is configured to execute a power-based input limitation (that is, a process for controlling the input power of the battery  11  such that the input power of the battery  11  does not exceed the W in ). Further, the HVECU  50  is configured to control the output power of the battery  11  using the W out . The HVECU  50  is configured to execute a power-based output limitation (that is, a process for controlling the output power of the battery  11  such that the output power of the battery  11  does not exceed the W out ). 
     In such a manner, corresponding to the IW in  and the IW it  output from the battery pack  10 , the W in  and the W out  used for controlling the battery power are obtained by the HVECU  50 . For this reason, the gate ECU  60 , interposed between the battery pack  10  and the HVECU  50 , relays communication between the battery pack  10  and the HVECU  50 , and converts the IW in  and the IW out  into the W in  and the W out , respectively. With such a configuration, the HVECU  50  can appropriately execute the power-based input and output limitations of the battery  11  included in the battery pack  10 . 
     In the vehicle  100  having such a configuration, when the capacity or performance of the battery  11  is reduced due to deterioration, or the like, of the battery  11 , replacing the battery  11  mounted on the vehicle  100  can be considered. 
     The battery  11  is mounted on the vehicle  100 , generally in a form of the battery pack  10  as described above. Peripheral devices (for example, the battery sensor  12  and the battery ECU  13 ) appropriate for the battery  11  are mounted on the battery pack  10  as described above. The battery pack  10  is maintained such that the battery  11  and the peripheral devices thereof can normally operate. For this reason, when the battery  11  mounted on the vehicle  100  is replaced, it is considered desirable that the entire battery pack  10  mounted on the vehicle  100  as well as the battery  11  be replaced for the purpose of vehicle maintenance. 
     In the case where such a battery pack is replaced, the gate ECU  60  that relays communication as described above is separately provided so as to enable communication between the replacement battery pack  10  and the HVECU  50  after the replacement. In a vehicle having such a configuration, in a case where prescribed information exchanged during communication in the gate ECU  60  is stored in a storage device  60   c , for example, when a defect, such as the temperature of the battery pack  10  rising higher than expected, occurs, the gate ECU  60  needs to be installed such that the ECU  60  is not influenced by the heat generated in the battery pack  10 . 
     Therefore, in the present embodiment, it is assumed that the gate ECU  60  is installed at a position outside the battery pack  10 . More specifically, it is assumed that the gate ECU  60  is installed at a position not immediately above the battery pack  10 . 
     In such a manner, since the gate ECU  60  is installed at a position outside the battery pack  10 , it is possible to prevent the gate ECU  60  from being influenced by the heat generated when a defect occurs in the battery pack  10 . Therefore, it is possible to protect the storage device  60   c  that stores prescribed information acquired from the battery pack  10  in which a defect has occurred. 
     The motor ECU  23 , the engine ECU  33 , and the HVECU  50  are also installed at predetermined positions outside the battery pack  10 . Further, the battery ECU  13  is installed at a predetermined position inside the battery pack  10 . 
     Hereinafter, an example of a configuration of each of the battery ECU  13 , the HVECU  50 , and the gate ECU  60  in the present embodiment will be described, and an example of prescribed information stored in the gate ECU  60  and an example of a position at which the gate ECU  60  is installed will be described in detail. 
       FIG. 4  is a diagram illustrating detailed configurations of the battery pack  10 , the HVECU  50 , and the gate ECU  60 . By referring to  FIG. 4  together with  FIG. 2 , in the present embodiment, the battery  11  included in the battery pack  10  is an assembled battery including a plurality of cells  111 . Each cell  111  may be, for example, a lithium-ion battery. Each cell  111  includes a positive electrode terminal  111   a , a negative electrode terminal  111   b , and a battery case  111   c . In the battery  11 , the positive electrode terminal  111   a  of one cell  111  and the negative electrode terminal  111   b  of another adjacent cell  111  are electrically connected to each other by a conductive bus bar  112 . The cells  111  are connected in series. 
     The battery pack  10  includes the battery sensor  12 , the battery ECU  13 , and the SMR  14  in addition to the battery  11 . A signal (hereinafter, also referred to as a “battery sensor signal”) output from the battery sensor  12  to the battery ECU  13  includes a signal indicating voltage VB output from the voltage sensor  12   a , a signal indicating current IB output from the current sensor  12   b , and a signal indicating the temperature TB output from the temperature sensor  12   c . The voltage VB indicates an actually measured value of the voltage of each cell  111 . The current IB indicates an actually measured value of the current flowing through the battery  11  (the charging side is negative). The temperature TB indicates an actually measured value of the temperature of each cell  111 . 
     The battery ECU  13  repeatedly acquires a latest battery sensor signal. An interval (hereinafter, also referred to as a “sampling cycle”) at which the battery ECU  13  acquires a battery sensor signal may be fixed or variable. In the present embodiment, the sampling cycle is assumed to be 8 milliseconds. However, an applicable embodiment of the present disclosure is not limited thereto, and the sampling cycle may be variable within a predetermined range (for example, a range from 1 millisecond to 1 second). 
     The battery ECU  13  includes an IW in  calculation unit  131  and an IW out  calculation unit  132 . The IW in  calculation unit  131  is configured to obtain the IW in  using a detection value (that is, a battery sensor signal) of the battery sensor  12 . A well-known method can be employed as an IW in  calculation method. The IW in  calculation unit  131  may determine the IW in  such that a charge current limitation for protecting the battery  11  is executed. The IW in  may be determined to prevent, for example, excessive charging, Li deposition, high rate deterioration, and overheating of the battery  11 . The IW out  calculation unit  132  is configured to obtain the IW out  using a detection value (that is, a battery sensor signal) of the battery sensor  12 . A well-known method can be employed as an IW out  calculation method. The IW out  calculation unit  132  may determine the IW out  such that a discharge current limitation for protecting the battery  11  is executed. The IW out  may be determined to prevent, for example, excessive discharging, Li deposition, high rate deterioration, and overheating of the battery  11 . In the battery ECU  13 , the IW in  calculation unit  131  and the IW out  calculation unit  132  are embodied by, for example, the processor  13   a  illustrated in  FIG. 2  and the program executed by the processor  13   a . However, an applicable embodiment of the present disclosure is not limited thereto, and each of these units may be embodied by dedicated hardware (an electronic circuit). 
     The battery pack  10  outputs, to the gate ECU  60  as a command signal S 1 , the IW in  obtained by the IW in  calculation unit  131 , the IW out  obtained by the IW out  calculation unit  132 , and the signal (that is, the battery sensor signal) input from the battery sensor  12 . These pieces of information are output from the battery ECU  13  included in the battery pack  10  to the gate ECU  60  provided outside the battery pack  10 . As illustrated in  FIG. 2 , the battery ECU  13  and the gate ECU  60  exchange information via the CAN communication. 
     The gate ECU  60  includes a W in  conversion unit  61  and a W out  conversion unit  62  to be described below. In the gate ECU  60 , the W in  conversion unit  61  and the W out  conversion unit  62  are embodied by, for example, the processor  60   a  illustrated in  FIG. 2  and the program executed by the processor  60   a . However, an applicable embodiment of the present disclosure is not limited thereto, and each of these units may be embodied by dedicated hardware (an electronic circuit). 
     The W in  conversion unit  61  converts the IW in  into the W in  using the following equation (1). The equation (1) is stored in advance in the storage device  60   c  (see  FIG. 2 ): 
         W   in   =IW   in   ×VBs   (1)
 
     In the equation (1), VBs represents an actually measured value of the voltage of the battery  11  detected by the battery sensor  12 . In the present embodiment, the average cell voltage (for example, the average of the voltages of all the cells  111  composing the battery  11 ) is employed as the VBs. However, an applicable embodiment of the present disclosure is not limited thereto, and instead of the average cell voltage, the maximum cell voltage (that is, the highest voltage from among the voltages of all the cells  111 ) and the minimum cell voltage (that is, the lowest voltage from among the voltages of all the cells  111 ), or the inter-terminal voltage of the assembled battery (that is, the voltage applied between the external connection terminal T 1  and the external connection terminal T 2  when the SMR  14  is in the closed state) may be employed as the VBs. The W in  conversion unit  61  can acquire the VBs using the battery sensor signal (in particular, the voltage VB). The W in  conversion unit  61  converts the IW in  into the W in  by multiplying the IW in  by the VBs according to the above equation (1). 
     The W out  conversion unit  62  converts the IW out  into the W out  using the following equation (2). The VBs in the equation (2) is the same as that in the equation (1). The equation (2) is stored in advance in the storage device  60   c  (see  FIG. 2 ): 
         W   out   =IW   out   ×VBs   (2)
 
     The W out  conversion unit  62  can acquire the VBs (that is, the actually measured value of the voltage of the battery  11  detected by the battery sensor  12 ) using the battery sensor signal (in particular, the voltage VB). The W out  conversion unit  62  converts the IW out  into the W out  by multiplying the IW out  by the VBs according to the above equation (2). 
     When the IW in  the IW out , and the battery sensor signal are input from the battery pack  10  to the gate ECU  60 , the W in  conversion unit  61  and the W out  conversion unit  62  of the gate ECU  60  convert the IW in  and the IW out  into the W in  and the W out , respectively. Then, a command signal S 2  including the W in , the W out , and the battery sensor signal is output from the gate ECU  60  to the HVECU  50 . As illustrated in  FIG. 2 , the gate ECU  60  and the HVECU  50  exchange information via the CAN communication. 
     Further, a storage area (hereinafter, simply referred to as a “ring buffer”)  60   e  that functions as a ring buffer is set in the storage device  60   c . The storage device  60   c  is configured to keep at least the information stored in the ring buffer  60   e  even after the power supply of the vehicle  100  is disconnected. The ring buffer  60   e  stores information including various detection results, various calculation results, and various control commands exchanged between the battery ECU  13  and the HVECU  50 . In other words, the ring buffer  60   e  stores the IW in , IW out , IB, VB, and TB that are input from the battery ECU  13 , the W in  that is a calculation result of the W in  conversion unit  61 , the W out  that is a calculation result of the W out  conversion unit  62 , and control commands S M1 , S M2 , and S E  to be described below. 
     The information exchanged between the battery ECU  13  and the HVECU  50  is repeatedly acquired and stored in the ring buffer  60   e . When a predetermined period has elapsed since the information is acquired, it is overwritten by newly acquired information. For this reason, the ring buffer  60   e  stores information exchanged between the battery ECU  13  and the HVECU  50  in a latest predetermined period. 
     The HVECU  50  includes a control unit  51  to be described below. In the HVECU  50 , the control unit  51  is embodied by, for example, the processor  50   a  illustrated in  FIG. 2  and the program executed by the processor  50   a . However, an applicable embodiment of the present disclosure is not limited thereto, and the control unit  51  may be embodied by dedicated hardware (an electronic circuit). 
     The control unit  51  is configured to control the input power of the battery  11  using the upper limit value W in . Further, the control unit  51  is configured to control the output power of the battery  11  using the upper limit value W out . In the present embodiment, the control unit  51  prepares the control commands S M1 , S M2 , and S E  for the MGs  21   a ,  21   b , and the engine  31 , illustrated in  FIG. 1 , respectively such that the input power and output power of the battery  11  do not exceed the upper limit values W 1 , W out , respectively. The control unit  51  outputs, to the gate ECU  60 , a command signal S 3  including the control commands S M1 , S M2  for the MGs  21   a ,  21   b , and the control command S E  for the engine  31 . Then, the control commands S M1 , S M2  in the command signal S 3  output from the HVECU  50  are transmitted to the motor ECU  23  via the gate ECU  60 . The motor ECU  23  controls the PCU  24  (see  FIG. 1 ) according to the received control commands S M1 , S M2 . Further, the control command S E  in the command signal S 3  output from the HVECU  50  is transmitted to the engine ECU  33  via the gate ECU  60 . The engine ECU  33  controls the engine  31  according to the received control command S E . The MGs  21   a ,  21   b , and the engine  31  are controlled according to the control commands S M1 , S M2 , and S E , respectively, and thus the input power and output power of the battery  11  are controlled such that the input power and output power of the battery  11  do not exceed the upper limit values W in , W out , respectively. By controlling the engine  31  and the PCU  24 , the HVECU  50  can adjust the input power and output power of the battery  11 . 
     Hereinafter, in the present embodiment, an example of a position at which the gate ECU  60  is installed will be described with reference to  FIGS. 5 to 7 . 
       FIG. 5  is a diagram illustrating an example of a position of the gate ECU  60  viewed from above the vehicle  100 .  FIG. 6  is a diagram illustrating an example of a position of the gate ECU  60  inside a cabin of the vehicle  100 .  FIG. 7  is a diagram illustrating an example of a position of the gate ECU  60  viewed from a side of the vehicle  100 . 
     As illustrated in  FIG. 5 , the gate ECU  60  is installed, for example, between a dashboard  80  and a dash panel  82  that serves as a boundary between an engine room, provided with the engine  31  and the transmission  4 , and the vehicle cabin. As illustrated in  FIG. 6 , the dashboard  80  is provided with, for example, a display  83   a  of a navigation system, a glove box  83   b , an air outlet  83   c  of an air conditioner, and the like. The battery pack  10  is provided between the drive wheels  45   a ,  45   b  that are front wheels, and driven wheels  45   c ,  45   d  that are rear wheels. As illustrated in  FIG. 5 , the gate ECU  60  is provided at a position inside the vehicle cabin which does not overlap the battery pack  10  viewed from above the vehicle  100 . 
     As illustrated in  FIG. 7 , the battery pack  10  is installed under the floor  84  of the vehicle  100 . In other words, the battery pack  10  is provided at a position outside the vehicle cabin. Further, the gate ECU  60  is installed at a position not immediately above the battery pack  10 . 
     As described above, the vehicle  100  according to the present embodiment includes the battery pack  10  including the battery ECU  13 , and the HVECU  50  and the gate ECU  60  that are provided separately from the battery pack  10 . 
     The battery ECU  13  is configured to obtain the IW in  (that is, a current upper limit value indicating the upper limit value of the input current of the battery  11 ) and the IW out  (that is, a current upper limit value indicating the upper limit value of the output current of the battery  11 ) using the detection value of the battery sensor  12 . The battery pack  10  is configured to output the IW in  and the IW out . 
     The gate ECU  60  is configured to relay communication between the battery ECU  13  and the HVECU  50 . The W in  conversion unit  61 , the W out  conversion unit  62 , and the storage device  60   c  including the ring buffer  60   e  are mounted on the gate ECU  60 . When the IW in  and the IW out  are input from the battery pack  10  to the gate ECU  60 , the W in  conversion unit  61  and the W out  conversion unit  62  of the gate ECU  60  convert the IW in  and the IW out  into the W in  and the W out , respectively. Then, the W in  and the W out  are output from the gate ECU  60  to the HVECU  50 . Further, the gate ECU  60  stores, in the ring buffer  60   e  of the storage device  60   c , the IW in , IW out , W in , W out , IB, VB, TB, S M1 , S M2 , and S E . For this reason, the ring buffer  60   e  stores the history information on the above-described information in the latest predetermined period. 
     The HVECU  50  is configured to control the input power of the battery  11  using the upper limit value W in  input from the gate ECU  60 . Further, the HVECU  50  is configured to control the output power of the battery  11  using the upper limit value W out  input from the gate ECU  60 . For this reason, the HVECU  50  can appropriately execute the power-based input and output limitations using the upper limit values W in , W out . 
     As described above, since the storage device  60   c  of the gate ECU  60  stores the history information on the information exchanged between the battery ECU  13  and the HVECU  50 , when any defect related to the control of the battery power occurs during the use of the replacement battery pack  10  after the replacement, it is possible to easily separate a cause of the defect in the battery pack  10  from a cause of the defect in the vehicle  100  excluding the battery pack  10 , using the stored history information. 
     When the cause of various defects that have occurred in the vehicle is analyzed, the information exchanged between the battery ECU  13  and the HVECU  50  in the latest predetermined period is read out from the ring buffer  60   e  of the gate ECU  60 . When the information received from the battery pack  10  includes some abnormal information (for example, when there is a value in the detection history of the temperature sensor exceeding a range that can be normally obtained), it can be determined that the cause of the defect is in the battery pack  10 . On the other hand, when the information received from the battery pack  10  is normal and the information received from the HVECU  50  includes some abnormal information (for example, when a value indicating a control command to the MG  21   a , the MG  21   b  or the engine  31  exceeds a range that can be normally obtained), it can be determined that the cause of the defect is in the HVECU  50 . For this reason, it is possible to easily separate a cause of the defect in the battery pack  10  from a cause of the defect in the vehicle  100  excluding the battery pack  10 . 
     Further, since the gate ECU  60  that stores the information with which the cause of such a defect can be easily separated is provided at a position outside the battery pack  10 , it is possible to prevent the gate ECU  60  from being influenced by the heat generated when a defect occurs in the battery pack  10 . Therefore, it is possible to protect the storage device  60   c  that stores the above prescribed information acquired from the battery pack in which a defect has occurred. In particular, the influence of the heat generated when a defect occurs in the battery pack  10  is greater at a position immediately above the battery pack  10  in the vehicle  100  than at a position not immediately above the battery pack  10 . Therefore, by providing the gate ECU  60  at a position not immediately above the battery pack  10 , it is possible to prevent the gate ECU  60  from being influenced by the heat generated when a defect occurs in the battery pack  10 . Further, since the heat generated when a defect occurs in the battery pack  10  outside the vehicle cabin is less likely to be transferred by the vehicle cabin, it is possible to prevent the gate ECU  60  from being influenced by the heat generated when a defect occurs in the battery pack  10 . 
     Therefore, it is possible to provide a vehicle having a replaceable battery pack mounted thereon, in which a control device that relays communication between the battery pack and a control device of the vehicle is installed at an appropriate position. 
     In addition, since the ring buffer  60   e  stores the history information in the latest predetermined period, it is possible to store the history information without unnecessarily increasing a storage capacity of the storage device  60   c.    
     Further, when the battery current limit values IW in , IW out  calculated in the battery ECU  13  differ from the limit values of the control target in the HVECU  50 , the gate ECU  60  converts the IW in  and the IW out  into the W in  and the W out , respectively. Therefore, it is possible to control the battery power of the battery pack  10  using the information from the battery pack  10  without changing a configuration of the HVECU  50 . 
     Hereinafter, a modified example will be described. In the above-described embodiment, although an example in which the battery ECU  13 , the motor ECU  23 , and the engine ECU  33  are connected to the local bus B 1  has been described, the motor ECU  23  and the engine ECU  33  may be connected to the global bus B 2 . 
     Further, in the above-described embodiment, as a configuration of the electrically driven vehicle, although an example of a configuration of a hybrid vehicle as illustrated in  FIG. 1  has been described, an applicable embodiment of the present disclosure is not particularly limited thereto. The electrically driven vehicle may be, for example, an electric vehicle on which an engine is not mounted, or a plug-in hybrid vehicle (PHV) in which a secondary battery of a battery pack is charged using power supplied from the outside of the vehicle. 
     Moreover, in the above-described embodiment, although an example in which the HVECU  50  is configured to control the SMR  14  via the battery ECU  13  has been described, the HVECU  50  may be configured to directly control the SMR  14 , not via the battery ECU  13 . 
     In addition, in the above-described embodiment, although an example in which the battery  11  (the secondary battery) included in the battery pack  10  is an assembled battery has been described, the battery  11  may be, for example, a single battery. 
     Further, in the above-described embodiment, although the gate ECU  60  storing, in the ring buffer  60   e  of the storage device  60   c , the IW in , IW out , W m , W out , IB, VB, TB, S M1 , S M2 , and S E  as information exchanged between the battery ECU  13  and the HVECU  50  has been described, the gate ECU  60  may store, in the ring buffer  60   e  of the storage device  60   c , for example, at least one piece of information, from among the above pieces of information, using which it is possible to separate causes of defects assumed in advance. 
     Furthermore, in the above-described embodiment, although the gate ECU  60  storing the information exchanged between the battery ECU  13  and the HVECU  50  in the ring buffer  60   e  of the storage device  60   c  has been described, the gate ECU  60  may store, in the ring buffer  60   e  of the storage device  60   c , at least one of the information exchanged between the motor ECU  23  and the HVECU  50 , and the information exchanged between the engine ECU  33  and the HVECU  50 , in addition to the above-described information. As such, it is possible to easily identify a part in which a defect has occurred. 
     In addition, in the above-described embodiment, although the gate ECU  60  storing the information exchanged between the battery ECU  13  and the HVECU  50  in the ring buffer  60   e  of the storage device  60   c  has been described, an interval at which the gate ECU  60  stores the information may be the same as, or longer than, an interval at which the gate ECU  60  acquires the information. As such, it is possible to set the interval at which the gate ECU  60  stores the information according to speed at which the information can be written on the storage device  60   c . For this reason, it is possible to broaden the types of memories that can be selected as the ring buffer  60   e . Further, for example, by setting the interval at which the information is stored to be longer than the interval at which the information is acquired, it is possible to store history information in a predetermined period without unnecessarily increasing the storage capacity. 
     Moreover, in the above-described embodiment, although the HVECU  50  executing the power-based input and output limitations has been described, the HVECU  50  may execute, for example, current-based input and output limitations. In this case, the W in  conversion unit  61  and the W out  conversion unit  62  of the gate ECU  60  are omitted. 
     In addition, in the above-described embodiment, although the battery ECU  13  calculating the upper limit values IW in , IW out  of the battery current has been described, the battery ECU  13  may calculate, for example, the upper limit values W in , W out , of the battery power. In this case, the W in  conversion unit  61  and the W out  conversion unit  62  of the gate ECU  60  are omitted. 
     Furthermore, in the above-described embodiment, an example in which the gate ECU  60  is installed between the dash panel  82  and the dashboard  80  has been described, but an applicable embodiment of the present disclosure is not limited thereto, and the gate ECU  60  may be installed inside the vehicle  100  and at least outside the battery pack  10 . For example, the gate ECU  60  may be installed in a trunk on the rear side of the vehicle  100 , or installed on an inner side of an exterior of the vehicle  100 , such as the roof and a pillar. Alternatively, for example, when the battery pack  10  is installed under the trunk on the rear side of vehicle  100 , the gate ECU  60  may be installed under a seat, in the center of the vehicle  100 , or the like. As such, it is possible to avoid damage to the gate ECU  60  caused by an accident, or the like. 
     Moreover, in the above-described embodiment, an example in which the gate ECU  60  is installed between the dash panel  82  and the dashboard  80  has been described. However, for example, the gate ECU  60  may be installed in a state of being covered with a thermal insulation material. As such, since the heat generated when a defect occurs in the battery pack  10  is less likely to be transferred by the thermal insulation material, it is possible to prevent the gate ECU  60  from being influenced by the heat generated when a defect occurs in the battery pack. 
     Further, a part or the whole of the above modified example may be appropriately combined and executed. The embodiments disclosed in the present disclosure should be considered as illustrative in all points, and not be considered as limited. The scope of the present disclosure is shown by the claims, not by the above description, and is intended to include meanings equivalent to the claims and all modifications within the scope thereof.