Patent Publication Number: US-2022227318-A1

Title: Onboard network system

Description:
TECHNICAL FIELD 
     The present disclosure belongs to the technical field related to an on-board network system. 
     BACKGROUND 
     Japanese Patent 1 discloses providing a gateway ECU that relays communications between ECUs of different networks and waking up only the network including a transmission target ECU to which signals start being transmitted first after all the networks have entered a sleep mode. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Unexamined Patent Publication No. 2016-201740 
     SUMMARY 
     Technical Problem 
     The technique disclosed in Patent Document 1 reduces the power consumption of an on-board communication system. There is however room for improvement. Specifically, at the time of waking up the transmission target ECU, the network (hereinafter referred to as a “transmission target network”) including the transmission target ECU is woken up. Accordingly, unused ECUs are also woken up in the transmission target network, which may cause excessive power consumption. 
     The technology disclosed herein was made in view of the problem. It is an objective of the present disclosure to achieve individual disconnections of electronic devices without increasing the number of power supply lines. 
     Solution to the Problems 
     In order to achieve the objective, the technique disclosed herein is directed to an on-board network system including: for each of a plurality of zones defined in a vehicle, a power distributor connected to an on-board battery; a plurality of electronic devices supplied with power from the power distributor via a common power supply line; and a zone control unit configured to control the plurality of electronic devices; and individual relays each between one of the electronic devices and a body ground of the vehicle to individually turn on and off connection between the one of the electronic devices and the body ground based on a control signal from the zone control unit. 
     This configuration includes individual relays between the electronic devices and the body ground of the vehicle so that the zone ECU individually disconnects the unused electronic devices in accordance with the scenes or other aspects. Accordingly, the power supply to the unused electronic devices stops, which reduces unnecessary standby currents or dark currents flowing to the unused electronic devices. 
     In the on-board network system according to one aspect, the electronic devices, which are turned on and off at a common timing in each of the zones, are collectively connected to the body ground via one of the individual relays. 
     This configuration requires a smaller number of individual relays. This configuration also simplifies a negative electrode circuit connected to the body ground. 
     In the on-board network system according to one aspect, the vehicle includes a body ground connector electrically connected to a metal body of the vehicle and connectable to a ground wire of each of the electronic devices. Each of the individual relays is built in the body ground connector. 
     This configuration allows efficient placement of the individual relays. 
     Advantage 
     As described above, the technique disclosed herein allows individual disconnections of electronic devices within a zone without increasing the number of power supply lines. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a schematic configuration of a power supply topology of a vehicle. 
         FIG. 2  is a block diagram showing an example of a power supply topology within a front left zone of the vehicle. 
         FIG. 3  is a table showing an example of unused electronic devices in scenes. 
         FIG. 4  is a block diagram showing another example of the power supply topology within the front left zone of the vehicle. 
         FIG. 5  is a block diagram showing further another example of the power supply topology within the front left zone of the vehicle. 
         FIG. 6  is a table showing example combinations of electronic devices unused simultaneously. 
         FIG. 7  is a diagram showing an example of the location of an individual relay. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     An exemplary embodiment will now be described in detail with reference to the drawings. The following description of a preferred embodiment is merely illustrative in nature and is not intended to limit the present invention and applications or uses thereof 
       FIG. 1  is a block diagram showing a schematic configuration of a power supply topology of a vehicle  10 . In the configuration shown in  FIG. 1 , the vehicle  10  is divided into four zones Z. The on and off of the power supply can be controlled in each zone. 
     Each zone Z includes a power distributor  21 , a plurality of electronic devices D, and a zone ECU  31 . The power distributor  21  is connected to an on-board battery  20  via a power supply line P. The electronic devices D are supplied with the power from the power distributor via one of common power supply lines PC. The zone ECU  31  manages the electronic devices D. Each of individual relays RL is interposed between one of the electronic devices D and the body ground of the vehicle  10  to individually turn on and off the one of the electronic devices D.  FIG. 1  shows an example where the plurality of electronic devices D are connected to the common power supply lines PC. Each individual relay RL is interposed between the one of the electronic devices D and the body ground of the vehicle  10 . Each individual relay RL is controlled to be on and off based on control signals Q output from the zone ECU  31 . The zone ECU  31  is an example of the zone control unit. 
     The zone ECU  31  operates in response to, for example, control signals SZ from a main arithmetic unit  30  that collectively controls the vehicle as a whole. The zone ECU  31  functions to manage and control the electronic devices D. For example, the zone ECU  31  receives results of detection by sensors to use the results for processing in the own unit or transmit the results to the main arithmetic unit  30 . For example, the zone ECU  31  controls the operations of the actuators. The sensors and actuators described above are examples of the electronic devices D. The zone ECU  31  includes a processor  31   a  (see  FIG. 2 ) and a memory  31   b  (see  FIG. 2 ). The memory  31   b  stores modules that are software executable by the processor  31 a. The functions of the zone ECU  31  described in the present embodiment are implemented by the processor  31   a  executing one or more modules stored in the memory  31   b.  A plurality of processors  31   a  and a plurality of memories  31   b  may be provided. The main arithmetic unit  30  includes a processor  30   a  and a memory  30   b.  The memory  30   b  stores modules that are software executable by the processor  30   a.  The functions of the main arithmetic unit  30  are implemented by the processor  30   a  executing one or more modules stored in the memory  30 b. A plurality of processors  30   a  and a plurality of memories  30 b may be provided. 
     In the following description, numerals may follow the reference characters for the sake of simplicity. For example, in  FIG. 1 , with respect to the zones Z, reference characters Z 1 , Z 2 , Z 3 , and Z 4  represent the front left, front right, rear right, and rear left zones, respectively, in the traveling direction of the vehicle. With respect to the power supply lines P, reference characters P 1 , P 2 , P 3 , and P 4  represent the power supply lines to the zones Z 1 , Z 2 , Z 3 , and Z 4 , respectively.  FIG. 1  shows, in the front left zone Z 1 , an example where electronic devices D 1 , D 2 , . . . , Dn (n is any integer) are as the electronic devices D connected to a common power supply line PC 1 . Individual relays RL 1 , RL 2 , . . . , RLn are interposed between the electronic devices D 1 , D 2 , . . . , Dn and the body ground of the vehicle  10 , respectively. The individual relays RL 1 , RL 2 , . . . , RLn are turned on and off based on control signals Q 1 , Q 2 , . . . , Qn output from the zone ECU  31 . Reference characters C 1 , C 2 , . . . , Cn represent signals for communications between the electronic devices D 1 , D 2 , . . . , Dn and the zone ECU  31 . In  FIG. 1 , the arrows C 1 , C 2 , . . . , Cn are directed from the zone ECU  31  toward the electronic devices D, but may be reversed or bidirectional depending on the types of the electronic devices D. For example, if the electronic devices D are sensors, output signals of the electronic devices D are input to the zone ECU  31 . For example, if the electronic devices D are cameras, setting and synchronization signals of the cameras are output from the zone ECU  31  to the cameras, and imaging signals are output from the cameras to the zone ECU  31 . 
     In  FIG. 1 , the zone ECUs  31 , the power distributors  21 , the electronic devices D, and the individual relays RL are denoted by the common reference characters. It is however not intended to indicate that the specific configurations are the same. For example, the electronic devices D include various sensors, various actuators, ECUs that control various actuators, various electronic components such as lights. The zone ECUs  31  and the power distributors  21  also have common functions in principle, but their specific functions or configurations may differ depending on the electronic devices D or other elements to be connected. 
     The on-board battery  20  supplies the power necessary for the operation of the vehicle  10 . For example, the on-board battery  20  supplies the power to the electronic devices D (including the ECUs) mounted on the vehicle  10  and the power for driving a motor in the case of an electronic vehicle. The power supply lines P and PC only need to be electric wires capable of supplying the power and may be wire harnesses, for example. 
       FIG. 2  shows an example of a power supply topology within the front left zone Z 1  of the vehicle.  FIG. 2  illustrates, as the electronic devices D: a rear monitoring sensor D 11  used for parking (hereinafter referred to as a “rear sensor D 11  for parking”), a theft monitoring device D 12  for theft monitoring, an external charging device D 13  used for external charging, radars D 21 , in-vehicle cameras D 22 , out-of-vehicle cameras D 23 , headlamps D 31 , clearance lamps D 32 , an air conditioner D 41 , and an audio device D 42 . Dli to D 13 , D 21  to D 23 , D 31 , D 32 , D 41 , and D 42  may be collectively and simply referred to as the “electronic devices D”. 
     In  FIG. 2 , as described above, the electronic devices D are supplied with the power from the on-board battery  20  via the common power supply line PC 1  connected to the power distributor  21 . The individual relays RL for individually turning on and off the electronic devices D based on the control signals Q from the zone ECU are interposed between the electronic devices D and the body ground of the vehicle  10 . In  FIG. 2 , as in the case of  FIG. 1 , the reference numerals corresponding to the electronic devices D follow the reference characters of the individual relays RL and the control signals Q. 
     The configuration described above allows the zone ECU  31  to individually disconnect the unused electronic devices D in accordance with the conditions, driving scenes, external environment of the vehicle or other factors. For example, when the rear monitoring sensor Dll and the theft monitoring device D 12  are not used while the vehicle  10  travels forward, the zone ECU  31  controls and turns off the individual relays RL 11  and RL 12 . On the other hand, for example, when the radars, the in-vehicle cameras, and the out-of-vehicle cameras are not used while the vehicle  10  stops, the zone ECU  31  controls and turns off the individual relays RL 21  to RL 23 . Accordingly, the power supply to the unused electronic devices D stops, which reduces unnecessary currents (including operating currents, standby currents, and dark currents) flowing to the unused electronic devices D. In addition, the zone ECU  31  grasps, in advance, the electronic devices D to be turned off and thus instructs the electronic devices D to store necessary parameters or extracts or stores setting data as necessary to collect or store information necessary for the next activation. 
     Some of the electronic devices D are unused in common in some scenes. The electronic devices D unused simultaneously in some scenes may be collectively controlled. 
       FIG. 3  shows an example of a table obtained by grouping the electronic devices D shown in  FIG. 2  and unused simultaneously in some scenes. For example, a group G 1  in  FIG. 3  is an example group of the electronic devices unused while the vehicle  10  “travel[s] forward”. The group G 1  includes, for example, the rear sensor Dll for parking, the theft monitoring device D 12 , and the external charging device D 13 . Similarly, a group G 2  is an example group of the electronic devices unused while the vehicle  10  “stop[s]” without any occupant. The group G 2  includes, for example, the radars D 21 , the in-vehicle cameras D 22 , and the out-of-vehicle cameras D 23 . A group G 3  indicates the group of the electronic devices unused when the “driver switch” of the vehicle  10  is “off” and the external environment is “bright” as in the daytime. The group G 3  includes, for example, the headlamps D 31 , the clearance lamps D 32 , and an interior lamp. In  FIG. 2 , each group of G 1  to G 3  is surrounded by a broken line. Note that there may be some electronic devices D out of the groups. 
     The scenes may be determined based on the information obtained by, for example, (1) the plurality of out-of vehicle cameras D 23 , (2) the plurality of radars D 21 , (3) a position sensor (not shown) (4) a vehicle condition sensor (not shown), (5) an occupant condition sensor (not shown), and (6) a drive operation information acquisition unit (not shown). The cameras D 23  are arranged on the body or other parts of the vehicle  10  and capture images of the environment outside the vehicle. The radars D 21  are arranged on the body or other parts of the vehicle  10  and detect objects, for example, outside the vehicle. The position sensor detects the position of the vehicle  10  (i.e., obtains vehicle position information) utilizing a global positioning system (GPS). The vehicle condition sensor includes outputs of sensors such as a vehicle speed sensor, an acceleration sensor, and a yaw rate sensor, detecting the behavior of the vehicle, and obtains the information on the conditions of the vehicle  10 . The occupant condition sensor includes the in-vehicle cameras D 22 , for example, and obtains the information on the conditions of an occupant(s) of the vehicle  10 . The drive operation information acquisition unit is for detecting the drive operation of the driver. While the determination on the scene is mainly executed by the main arithmetic unit  30 , some of the scenes may be determined by each zone ECU  31  independently. 
       FIG. 4  shows an example where the individual relays RL connected to the plurality of electronic devices D belonging to the same groups in  FIG. 3  are controlled by common control signal lines. Specifically, in  FIG. 4 , the individual relay RL 11  connected to the rear sensor Dli for parking, the individual relay RL 12  connected to the theft monitoring device D 12 , and the individual relay RL 13  connected to the external charging device D 13  are connected by a common control line. These individual relays RL 11 , RL 12  and RL 13  are controlled to be on and off based on common control signals Q 10 . Similarly, individual relays RL 21 , RL 22 , and RL 23  corresponding to the radars D 21 , the in-vehicle cameras D 22 , and the out-of-vehicle cameras D 23  are connected by a common control line and controlled to be on and off based on common control signals Q 20 . Individual relays RL 31  and RL 32  corresponding to the headlamps D 31  and the clearance lamps D 32  are connected by a common control line, and controlled to be on and off based on common control signals Q 30 . 
     In this manner, the wiring region necessary for wiring the control lines can be reduced using the common control lines. This configuration also simplifies control programs of the zone ECU  31  used for controlling the individual relays. The “method of controlling the individual relays” will be described later, and detailed description thereof will thus be omitted here. 
       FIG. 5  shows an example where the plurality of electronic devices D belonging to the same groups described above are connected to the body ground of the vehicle  10  via common individual relays RL. Specifically, in  FIG. 5 , the rear sensor Dli for parking, the theft monitoring device D 12 , and the external charging device D 13  are connected by the body ground of the vehicle  10  via a common individual relay RL 10 . The individual relay RL 10  is controlled to be on and off by the control signals Q 10  output from the zone ECU  31 . Similarly, the headlamps D 31  and the clearance lamps D 32  are connected to the body ground of the vehicle  10  via a common individual relay RL 30 . The individual relay RL 30  is controlled to be on and off by the control signals Q 30  output from the zone ECU  31 . The control signals Q 10  and Q 30  are similar to the control signals Q described above, and detailed description thereof is omitted here. The common individual relays RL 10  and RL 30  may be placed, if a plurality of corresponding electronic devices are located relatively close to each other. 
     In this manner, the number of the individual relays RL can be reduced using the common individual relays. This configuration also simplifies the negative electrode circuit connected to the body ground. 
     In the configurations of  FIGS. 1, 2, 4, and 5 , the locations of the individual relays RL are not particularly limited. For example, as shown in  FIG. 7 , each individual relay RL may be built in one of body ground connectors  40  on the body ground. This configuration allows efficient placement of the individual relays RL. Specifically, the body ground connectors  40  are fastened and fixed to body ground points in various locations of the body of the vehicle  10 . Each individual relay RL is located in, for example, a resin cover  42  of the one of the body ground connectors  40 . The example, a terminal  41  of the body ground connector  40  is fastened and fixed to a screw hole  12  in a metal body  11  of the vehicle  10  using a screw  43 . The terminal  41  is electrically connected to harnesses  43 . The harnesses  43  are connected to ground terminals (not shown) of the electronic devices D. A signal cable  44  for supplying the control signals Q from the outside to each individual relay RL is drawn to the body ground connector  40  of the type including a built-in individual relay RL. The individual relay RL only needs to be located in an intermediate point of the electrical path from one of the electronic devices D to the body ground. The individual relay RL may be located on the electronic substrate of one of the electronic device D, and is arranged on a joint in the intermediate point of the electrical path where the electronic substrate is connected to associated one of the harnesses  43  for the body ground. The body ground of the vehicle is well known and includes the metal body  11  of the vehicle  10 , for example. 
     &lt;Method of Controlling Individual Relays&gt; 
     Now, a method of controlling the individual relays will be described. 
     In the configuration of  FIG. 2 , each relay RL is interposed between one of the electronic devices D and the body ground of the vehicle. Assume that there is an electronic device D supplied with power which can be stopped. In this case, the zone ECU  31  controls and turns off the individual relay RL corresponding to the electronic device D to stop the power supply to the electronic device D. For example, while the vehicle travels forward, the zone ECU  31  controls and turns off the individual relay RL 11  to disconnect the path between the rear sensor Dli for parking and the body ground to make the rear sensor Dli for parking non-conductive. Accordingly, no current (e.g., no standby current or no dark current) flows to the rear sensor Dli for parking. 
     Next, a method of controlling the individual relays using the table of  FIG. 3  will be described. Where to store the table of  FIG. 3  is not particularly limited. For example, the table may be stored in advance in a storage unit (i.e., the memory  31 b) built in the zone ECU  31  or may be stored in another storage unit (e.g., the memory  30 b) in the vehicle  10 . 
     The zone ECU  31  refers to the table of  FIG. 3 , for example, and controls the plurality of electronic devices D simultaneously in accordance with the scenes. As described above, the zone ECU  31  determines the information on the scenes from time to time based on the scene information transmitted from the main arithmetic unit  30 , for example. 
     For example, assume that the vehicle travels forward (the scene is hereinafter referred to as a “travel scene of the vehicle”). At this time, the zone ECU  31  refers to the group G 1  in  FIG. 3  and controls and turns off the individual relays RL corresponding to the electronic devices D unused in the travel scene of the vehicle. In the example of  FIG. 3 , the zone ECU  31  controls and turns off the individual relays RL 11  to RL 13 . Accordingly, the rear sensor Dli for parking, the theft monitoring device D 12 , and the external charging device D 13  are disconnected from the body ground. The zone ECU  31  controls and turns off the individual relays RL 11  to RL 13  using control signals Q 11  to Q 13  in the configuration of  FIG. 2  and the control signals Q 10  in the configurations of  FIGS. 4 and 5 . Similarly, for example, while the vehicle stops without any occupant, the zone ECU  31  refers to the group G 2  in  FIG. 3  and controls and turns off the individual relays RL 21  to RL 23 . Accordingly, the radars D 21 , the in-vehicle cameras D 22 , and the out-of-vehicle cameras D 23  are disconnected from the body ground. 
     As described above, in the present embodiment, the combination table of the electronic devices D unused in common in some scenes is stored in advance in the storage unit, for example, and referred to by the zone ECU  31  to collectively control the plurality of individual relays RL. With this configuration, what is controlled in each vehicle can be changed by varying the table, that is, for example, the power management for each vehicle grade can be set simply by varying the table. 
     Next, a method of controlling the individual relays using the table of  FIG. 6  will be described. Like the table of  FIG. 3 , where to store the table of  FIG. 6  is not particularly limited. For example, the table is stored in a storage unit (not shown) in the zone ECU  31  or any other place. 
     The table of  FIG. 6  is obtained by listing up combinations of the electronic devices unused simultaneously. Specifically,  FIG. 6  shows a list of electronic devices D in the following relationship. While one electronic device group M 1  is used, the other electronic device group M 2  is unused. While the other electronic device group M 2  is used, the one electronic device group M 1  is unused. In another point of view, in  FIG. 6 , the electronic devices listed in the same row in the electronic device group M 1  are used or unused simultaneously. The same applies to the electronic device group M 2 . The electronic devices D, of the electronic device group M 2 , listed in the same row are used or unused simultaneously. 
     Specifically, in the first row of  FIG. 6  (Y 1  in  FIG. 6 ), a keyless entry system and the theft monitoring device listed in the electronic device group M 1  are not used simultaneously with the steering system and the brake system listed in the electronic device group M 2 . More specifically, while the vehicle  10  stops in a parking lot or any other place and the occupant(s) is/are out of the vehicle  10 , the keyless entry system and the theft monitoring device need to be in an operable state (including a standby state) with the power supplied. On the other hand, the keyless entry system and the theft monitoring device are unused while the vehicle  10  travels. The power supply may thus be shut off without any problem. The steering system and the brake system are unused while the vehicle  10  stops in a parking lot or any other place and the occupant(s) is/are out of the vehicle  10 . The power supply may thus be shut off without any problem. On the other hand, while the vehicle  10  travels, the steering system and the brake system need to be in an operable state (including a standby state) with the power supplied. 
     Based on the table of  FIG. 6 , in use of one of the groups of the electronic devices unused simultaneously, the zone ECU  31  shuts off the power supply to the electronic devices of the other group. For example, in the example of  FIG. 6 , the zone ECU  31  shuts off the power supply to the keyless entry system and the theft monitoring device (i.e., in the electronic device group M 1 ) when at least one of the steering system and the brake system (i.e., in the electronic device group M 2 ) operates with the power supplied. How to shut off the power supply is not particularly limited. For example, the individual relays RL may be interposed between the electronic devices D described above and the body ground of the vehicle  10  so that the zone ECU  31  turns on or off the individual relays RL to shut off the power supply. 
     At this time, as shown in  FIG. 4 , the electronic devices D belonging to the electronic device group M 1  may be controlled by the common control signals Q. Alternatively, as shown in  FIG. 5 , the electronic devices D belonging to the electronic device group M 1  may be connected to the body ground of the vehicle  10  via the common individual relays RL. The same applies to the electronic device group M 2 . 
       FIG. 6  shows, in addition to the above-described Yl, three examples (Y 2 , Y 3 , and Y 4 ) of the groups M 1  and M 2  of the electronic devices unused simultaneously. 
       FIG. 6  illustrates, in Y 2 , a power lift gate and a power sliding door in the electronic device group Ml, and door glass regulators for raising and lowering respective door glasses, wipers, and washers in the electronic device group M 2 . For example, when the power sliding door operates, the power supply to the door glass regulator is shut off not to catch an arm or any other body part of the occupant(s). In this manner, the configuration and control according to the present embodiment are used for electronic devices that are unused simultaneously and would better operate not simultaneously. While one electronic device group operates, the power supply to the other electronic device group can be shut off, that is, the operation of the other electronic device group stops more reliably. 
       FIG. 6  illustrates, in Y 3 , an electric parking brake in the electronic device group M 1 , and a 4WD coupling system (e.g., a multi-plate electromagnetic clutch) in the electronic device group M 2 . Although not limited to the electric parking brake and the 4WD coupling system, a plurality of devices or circuits may be used in combination to fulfil certain functions. In this case, a predetermined functional configuration (e.g., the electric parking brake) may be implemented by an electronic device group including a plurality of electronic devices or electronic circuits which are also included in the “electronic device groups” according to the present disclosure. 
       FIG. 6  illustrates, in Y 4 , the keyless entry system and the theft monitoring device in the electronic device group M 1 , and an audio device and an infotainment display are in the electronic device group M 2 . In this manner, in the table of  FIG. 6 , the electronic devices of one of the groups may overlap. In addition, some of the electronic devices in each of the electronic device groups M 1  and M 2  may overlap. For example, a plurality of individual relays RL may be provided for the overlapping devices to allow operations corresponding to control of the respective rows. 
     To sum up, the on-board network system according to the present embodiment includes, for each predetermined zone of the vehicle, the zone ECU  31 , the power distributor  21  connected to the on-board battery  20 , and the plurality of electronic devices D supplied with the power from the power distributor  21  via the common power supply line PC. Each of the individual relays RL is interposed between one of the electronic devices D and the body ground of the vehicle  10  to individually turn on and off the connection between the electronic device D and the body ground based on the control signals Q from the zone ECU  31 . 
     In this manner, each of the individual relays RL is interposed between one of the electronic devices D and the body ground of the vehicle  10 . Accordingly, the zone ECU  31  individually shuts off the unused electronic devices D in accordance to the scenes, for example. As a result, the power supply to the unused electronic devices D stops, which reduces unnecessary standby currents or dark currents flowing to the unused electronic devices D. 
     Here, in order to individually turn on and off the power supply of to the electronic devices D, connecting the power distributors  21  and all the electronic devices D by individual power supply lines is conceivable. There is, however, a need to prepare the number of the wire harnesses corresponding to the number of the electronic devices. By contrast, in the configuration according to the present embodiment, the unused electronic devices D can be individually disconnected while the power distributor  21  and the plurality of electronic devices D are connected by the common power supply lines PC. There is thus no need to prepare a great number of wire harnesses to achieve the individual disconnection of the electronic devices D. 
     In the embodiment described above, each electronic device D may belong to a plurality of groups G. In this case, the individual relays RL may be, between the electronic device D and the body ground of the vehicle, connected in series according to the number of groups. The power supply may be shut off based on the control signals according to the groups G. 
       FIG. 3  shows the example of using the table obtained by grouping the electronic devices unused simultaneously in the respective scenes, the table is not limited thereto. For example, the table may be prepared by grouping the electronic devices used simultaneously in specific scenes or by grouping the electronic devices used and unused in common in scenes. 
     INDUSTRIAL APPLICABILITY 
     The technology disclosed herein is useful as an on-board network system. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
           10  Vehicle 
           21  Power Distributor 
           31  Zone ECU (Zone Control Unit) 
         D Electronic Device 
         PC Common Power Supply Line 
         RL Individual Relay 
         Z Zone