JP5406079B2 - In-vehicle communication system - Google Patents

Description

  The present invention relates to an in-vehicle communication system including a plurality of control units that are connected to a communication line arranged in a vehicle and transmit / receive data to / from each other via the communication line.

  2. Description of the Related Art Conventionally, vehicles such as automobiles are equipped with a plurality of ECUs (Electronic Control Units) corresponding to each control as the various functions become more sophisticated and complicated. Each ECU is connected to each other by an in-vehicle LAN (Local Area Network) built in the vehicle, and various data can be transmitted and received between the ECUs. As a result, it is not necessary to provide a wire harness for each ECU, and it is possible to realize the mountability and weight reduction of the wire harness, thereby improving the fuel efficiency of the vehicle.

  For in-vehicle LAN, for example, LIN (Local Interconnect Network) used for body systems such as air conditioners and power windows with a bit rate of 1 to 20kbps, and used for power train systems such as engines and transmissions with a bit rate of 10k to 1Mbps. CAN (Controller Area Network) is known. LIN employs a single master-event-driven communication system using one communication line (Bus), and CAN employs a multi-master-event-driven communication system using two communication lines. These LIN and CAN can coexist in the vehicle through an integrated unit such as a gateway.

  Since CAN employs a multi-master-event-driven communication system, data can be sent simultaneously from a plurality of ECUs to a communication line. As a result, it is suitable for powertrain control that requires real-time performance. On the other hand, when a plurality of data are simultaneously sent to the communication line, there is a concern that the bit rate may be reduced due to communication congestion (bottleneck). Therefore, it is necessary to devise a technique for reducing the weight of data sent to the communication line in response to the higher functionality and complexity of various controls. Furthermore, by reducing the weight of the data, the ECU can be replaced with low-spec specifications. In other words, as the data is lightened, the number of reception buffers and transmission buffers provided in each ECU can be reduced, and a low-spec ECU can achieve cost reduction while ensuring high reliability of the in-vehicle communication system.

  FIG. 5 is a circuit diagram showing an example of an in-vehicle communication system with room for reducing the weight of data. The in-vehicle communication system 100 shown in FIG. 5 includes a cruise control unit (C-CU) 101, an engine control unit (EG -CU) 102, a transmission control unit (T-CU) 103, and a meter control unit (M-CU) 104. The in-vehicle communication system 100 employs CAN as a communication protocol, and each control unit (ECU) 101 to 104 is connected by a pair of communication lines (twist lines) 105.

  Each of the ECUs 101 to 104 includes a plurality of reception buffers and a plurality of transmission buffers for storing data (data frames) transmitted from the communication line 105. Here, in C-CU101, EG-CU102, and M-CU104, only a transmission buffer is shown, and in T-CU103, only a reception buffer is shown.

  Then, when the in-vehicle communication system 100 is energized from the initial system state after the in-vehicle communication system 100 is assembled, that is, the non-energized state after the assembly, as indicated by a dashed line arrow in the figure, the first transmission buffer 104a of the M-CU 104 To the first reception buffer 103a of the T-CU 103, the vehicle specification data of the identifier ID 400 is transmitted via the communication line 105. As a result, vehicle specification data (ID400) indicating that the vehicle has the cruise control function, that is, the C-CU 101, is stored in the first reception buffer 103a.

  The second reception buffer 103b of the T-CU 103 can receive the data with the identifier ID500, triggered by the reception of the vehicle specification data (ID400) by the first reception buffer 103a. Thereafter, the second reception buffer 103b of the T-CU 103 receives the T-CU cooperation data (ID500) transmitted from the first transmission buffer 101a of the C-CU 101, and thereby the C-CU 101 and the T-CU 103. And cooperative control is executed.

  As described above, the first reception buffer 103a (ID400) of the T-CU 103 is used only to enable reception of T-CU cooperation data (ID500) from the second reception buffer 101a of the C-CU101. That is, the first reception buffer 103a used only in the system initial state of the in-vehicle communication system 100 is not used after the in-vehicle communication system 100 is energized once. Therefore, weight reduction of data is realizable by devising which eliminates the 1st receiving buffer 103a.

  In addition, as techniques for reducing the load on the ECU and the bus (communication line) by reducing the weight of data, techniques described in Patent Document 1 and Patent Document 2 are known.

  The technology described in Patent Document 1 is a technology that reduces the processing load of the ECU, and in order to share the ECU regardless of differences in communication protocols (CAN, LIN, etc.), a communication control LSI is provided separately from the ECU. And a receiving filtering means is provided in the communication control LSI. The reception filtering means discriminates the destination node number described in the header part of the received data, forwards the data destined for the ECU connected to itself to the ECU, and does not address the ECU connected to itself. Discard the data. This reduces the processing load on the ECU.

  On the other hand, in the technique described in Patent Document 2, a gateway ECU is provided between two CAN networks in order to suppress an increase in load on the bus. The gateway ECU is provided with message relay control means, so that the abnormal message is not relayed by the message relay control means, thereby suppressing the load on the bus.

JP 2006-192970 A (FIG. 3) JP 2007-038904 A (FIG. 1)

  However, according to the technique described in Patent Document 1 described above, it is necessary to attach a communication connector having a communication control LSI or the like to the terminal of the communication line. For this reason, problems such as an increase in weight due to the communication connector and restrictions on installation space in the vehicle arise, and a problem arises that the manufacturing cost increases because the communication connector needs to be provided corresponding to each ECU. In the technique described in Patent Document 2 described above, the gateway ECU having the message relay control means is provided, which causes a problem that the manufacturing cost increases. As described above, each of the above-described technologies is intended to reduce the weight of data sent to the communication line. In the present invention, however, the ECU particularly focuses on unnecessary data as shown in FIG. It was invented to simplify the structure.

  An object of the present invention is to provide an in-vehicle communication system capable of reducing the number of buffers provided in a control unit by reducing the weight of data transmitted to a communication line, and ensuring high reliability and cost reduction.

  An in-vehicle communication system according to the present invention is an in-vehicle communication system that includes a plurality of control units that are connected to a communication line arranged in a vehicle and transmit / receive data to / from each other via the communication line. The detection data from the sensor is stored in a reception buffer, the traveling state data of the vehicle is obtained and stored in a transmission buffer, the traveling state control unit for sending the traveling state data to the communication line, and the traveling state data is received A driving source control unit that stores in the buffer, obtains driving state data of a driving source provided in the vehicle, stores the driving state data in a transmission buffer, and sends the traveling state data and the driving state data to the communication line; and the traveling state A reception buffer for receiving the data and the driving state data, the driving state data and the driving state A transmission ratio control unit that controls a transmission ratio of the vehicle based on data, and the transmission ratio control unit operates from the drive source control unit by operating the traveling state control unit in an initial system state of the vehicle. When the traveling state data is received, the traveling state data is directly received from the traveling state control unit from the next control cycle.

  In the in-vehicle communication system according to the present invention, the traveling state control unit is a cruise control unit that performs a follow-up control that maintains a constant inter-vehicle distance from a preceding vehicle.

  In the in-vehicle communication system of the present invention, a meter control unit is connected to the communication line, vehicle specification data is stored in a transmission buffer of the meter control unit, and the meter control unit includes the running state control unit, the drive source The vehicle specification data is sent to a controller other than the control unit and the gear ratio control unit.

  According to the in-vehicle communication system of the present invention, the traveling state control unit, the drive source control unit, and the transmission ratio control unit are connected to the communication line arranged in the vehicle, and the transmission ratio control unit is in the initial system state of the vehicle. When the traveling state control unit is activated and the traveling state data is received from the drive source control unit, the traveling state data is directly received from the traveling state control unit from the next control cycle. Therefore, the transmission ratio control unit does not need to be provided with a reception buffer for storing vehicle specification data indicating that the traveling state control unit is provided. Therefore, the data sent to the communication line can be reduced in weight, and the number of reception buffers provided in the transmission ratio control unit can be reduced. As a result, high reliability and cost reduction of the in-vehicle communication system can be realized.

  According to the in-vehicle communication system of the present invention, the traveling state control unit can be a cruise control unit that performs follow-up control that maintains a constant inter-vehicle distance from the preceding vehicle.

  According to the in-vehicle communication system of the present invention, the meter control unit is connected to the communication line, the vehicle specification data is stored in the transmission buffer of the meter control unit, and other than the traveling state control unit, the drive source control unit, and the gear ratio control unit. The vehicle specification data can be transmitted to the control unit from the meter control unit.

It is the schematic which shows the vehicle carrying the vehicle-mounted communication system in this invention. It is explanatory drawing explaining the internal structure of each ECU which forms the vehicle-mounted communication system of FIG. It is a circuit diagram explaining the transmission / reception state of the data between C-CU of FIG. 1, EG-CU, T-CU, and M-CU. It is a flowchart figure explaining the operation | movement content of T-CU of FIG. It is a circuit diagram which shows the example of the vehicle-mounted communication system with the room which aims at weight reduction of data.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  1 is a schematic diagram showing a vehicle equipped with an in-vehicle communication system according to the present invention, FIG. 2 is an explanatory diagram for explaining the internal structure of each ECU forming the in-vehicle communication system of FIG. 1, and FIG. 4 is a circuit diagram for explaining the data transmission / reception state among the CU, EG-CU, T-CU, and M-CU, and FIG. 4 is a flowchart for explaining the operation content of the T-CU in FIG. .

  As shown in FIG. 1, an automobile 10 as a vehicle includes a high-speed CAN 20 having a bit rate (data transfer speed) of 500 kbps used for power train control and a low speed of 125 kbps used for body control. CAN30 is built. The high-speed CAN 20 is standardized as ISO11898 (high-speed version), and the low-speed CAN 30 is standardized as ISO11519 (low-speed version). The high-speed CAN 20 and the low-speed CAN 30 are electrically connected to each other via an integrated unit 11 such as a gateway so that data can be transmitted and received. Here, the in-vehicle communication system according to the present invention includes the high-speed CAN 20, the low-speed CAN 30, and the integrated unit 11.

  The high-speed CAN 20 forming the in-vehicle communication system 12 includes a cruise control unit (C-CU) 21, an engine control unit (EG-CU) 22, a transmission control unit (T-CU) 23 and a meter control unit (M- CU) 24. Each control unit (ECU) 21 to 24 is electrically connected to a pair of communication lines 25 (see FIG. 2 for details) arranged in the automobile 10. The control units 21 to 24 transmit / receive data to / from each other via the communication line 25. In addition to various sensors provided in the automobile 10, other control units (not shown) are electrically connected to the communication line 25.

  The high-speed CAN 20 employs a differential transmission system that determines “0 (dominant)” and “1 (recessive)” based on the voltage difference of each communication line 25, and is hardly affected by external noise. Each communication line 25 has CAN_H and CAN_L as shown in FIG. 2, and each ECU 21 to 24 reads the level of the communication line 25, that is, the bus level by this voltage difference (for example, voltage difference of 1.8V), A logic “0” or a logic “1” is determined. As a result, it is determined whether the data (data frame) transmitted to the communication line 25 is data addressed to itself or data addressed to another ECU, and various data are transmitted / received between the ECUs 21 to 24. The ECUs 21 to 24 can be operated individually.

  Here, the identifier (ID) indicating the destination is stored in the arbitration field (11 bits) forming the data frame, and the data content is stored in the data field (0 to 8 bytes) forming the data frame. The data field is an area defined by the user.

  Next, the high-speed CAN 20 to which the present invention is applied will be described in detail with reference to FIG. Here, since the ECUs 21 to 24 have substantially the same configuration, the internal structure thereof will be described with reference to the drawings, with reference numerals 21 to 24.

  Each ECU 21-24 includes a CPU 40, a CAN controller 41, and a transceiver 42. The CPU 40 includes a plurality of reception buffers 40a and a plurality of transmission buffers 40b. Each reception buffer 40a stores detection data from various sensors, data from other ECUs, and the like. The CPU 40 executes predetermined arithmetic processing based on the data stored in each reception buffer 40a, and generates data suitable for the functions of the ECUs 21 to 24. The generated data is temporarily stored in each transmission buffer 40b and sent to the communication line 25 in accordance with the control timing of each ECU 21-24.

  Further, the CPU 40 is provided with a backup RAM 40c. The backup RAM 40c stores and holds data generated in the previous control cycle when the system power supply of the in-vehicle communication system 12 is turned off.

  The CAN controller 41 is electrically connected to the CPU 40, and communicates data processed by the CPU 40 with the transceiver 42 according to the communication protocol of the high-speed CAN 20. That is, the CAN controller 41 performs communication control of data to other ECUs via the transceiver 42 and the communication line 25.

  The transceiver 42 converts the output level from the CAN controller 41 to the bus level (CAN_H, CAN_L) of the high-speed CAN 20, that is, adjusts the generated data to a bus voltage that can be sent to the communication line 25.

  Next, functions of the ECUs 21 to 24 will be described in detail with reference to FIG.

  Each reception buffer 40a provided in the CPU 40 in the C-CU 21 stores detection data from various sensors. The CPU 40 of the C-CU 21 executes predetermined arithmetic processing based on the detection data stored in each reception buffer 40a, and generates T-CU cooperation data (running state data) for cooperation with the T-CU 23. The generated T-CU cooperation data is temporarily stored in the transmission buffer 40b and transmitted to the communication line 25 in accordance with the control timing of the C-CU 21. Also, detection data from a laser radar unit (not shown) provided at the front end portion of the automobile 10 is stored in each reception buffer 40a of the C-CU 21. Based on the detection data from the laser radar unit, the C-CU 21 calculates an inter-vehicle distance from a preceding vehicle that travels in front of the automobile 10, and performs follow-up control that keeps the calculated inter-vehicle distance constant. ing. In addition to this, the C-CU 21 performs throttle control automatically, and executes constant speed control for keeping the vehicle speed of the automobile 10 constant. Here, the C-CU 21 constitutes a traveling state control unit in the present invention.

  Detection data from various sensors is stored in each reception buffer 40 a provided in the CPU 40 in the EG-CU 22. The CPU 40 of the EG-CU 22 executes predetermined calculation processing based on the detection data stored in each reception buffer 40a, and drives the rotational speed, torque, etc. of an engine (not shown) as a drive source provided in the automobile 10 Generate state data. The other reception buffer 40a provided in the CPU 40 in the EG-CU 22 stores cruise control data (running state data) indicating that the C-CU 21 is in operation, and the cruise control data and drive state data are And temporarily stored in each transmission buffer 40b provided in the CPU 40 in the EG-CU22. Thereafter, as with the C-CU 21, the data is sent to the communication line 25 in accordance with the control timing of the EG-CU 22. Here, the EG-CU 22 constitutes a drive source control unit in the present invention.

  Each reception buffer 40a provided in the CPU 40 in the T-CU 23 stores T-CU cooperative data from the C-CU 21, cruise control data from the EG-CU 22, and driving state data. The CPU 40 of the T-CU 23 executes predetermined arithmetic processing based on the T-CU cooperation data and the driving state data stored in each reception buffer 40a, and calculates the optimum gear ratio of the automobile 10. Then, the CPU 40 of the T-CU 23 controls a transmission device (not shown) based on the calculated gear ratio, thereby controlling the automobile 10 to an optimal traveling state. Here, the T-CU 23 constitutes a gear ratio control unit in the present invention.

  Note that the T-CU 23 is set not to receive T-CU cooperative data from the C-CU 21 in the initial system state after the in-vehicle communication system 12 (the automobile 10) is assembled, that is, in the non-energized state after the assembly. ing. The T-CU 23 can directly receive the T-CU cooperation data from the C-CU 21 after the C-CU 21 is activated when the vehicle-mounted communication system 12 is first energized and receives the cruise control data from the EG-CU 22. . That is, the T-CU 23 is triggered by the reception of cruise control data from the EG-CU 22, and thereafter (from the next control cycle) based on the T-CU cooperation data directly received from the C-CU 21, The gear ratio is calculated.

  Each reception buffer 40a provided in the CPU 40 in the M-CU 24 stores detection data from various sensors and drive state data from the EG-CU 22. The CPU 40 of the M-CU 24 executes predetermined arithmetic processing based on the detection data and driving state data stored in each reception buffer 40a, and a speedometer, an engine tachometer, a warning light, etc. provided on the instrument panel of the automobile 10 (Not shown) is controlled to inform the driver of the traveling state of the automobile 10 and the like. Further, the vehicle specification data of the automobile 10 is stored in the transmission buffer 40b provided in the CPU 40 in the M-CU 24. This vehicle specification data is transmitted to the ECUs other than the ECUs 21 to 24 via the communication line 25. Are sent out. As a result, the other ECUs can execute control corresponding to the specifications of the automobile 10 (vehicle weight, equipped functions, etc.).

  The low-speed CAN 30 forming the in-vehicle communication system 12 includes an air conditioner control unit (AC-CU) 31, a power window control unit (PW-CU) 32, and a door lock control unit (DL-CU) as shown in FIG. 33 is provided. Each control unit (ECU) 31 to 33 is also electrically connected by a pair of communication lines 34, similarly to the high-speed CAN 20. Also, the ECUs 31 to 33 have substantially the same configuration as the ECUs 21 to 24 forming the high-speed CAN 20.

  Next, the operation of the high-speed CAN 20 forming the in-vehicle communication system 12 formed as described above will be described in detail with reference to FIGS.

  Here, in FIG. 2, reference numerals 40a and 40b are assigned to the respective reception buffers and transmission buffers of the ECUs 21 to 24, respectively, and are described with reference to one drawing. However, in FIG. In order to make the data transmission / reception state easy to understand, a and b are added after the signs 21, 22, 23, and 24 attached to each ECU, and the data is subdivided into a first reception buffer and a second reception buffer. explain. 3, similarly to the in-vehicle communication system 100 shown in FIG. 5, only the transmission buffer is shown in C-CU21, EG-CU22, and M-CU24, and only the reception buffer is shown in T-CU23. .

  As shown in FIG. 3, the first transmission buffer 21 a (shaded portion) of the C-CU 21 stores T-CU cooperation data with an identifier ID500. The first transmission buffer 22a (shaded portion) of the EG-CU 22 stores cruise control data and drive state data with an identifier ID600. Here, the cruise control data is formed by data “0” indicating a non-control state (crucon off), data “1” indicating a constant speed control state, and data “2” indicating a follow-up control state.

  The first reception buffer 23a (shaded portion) of the T-CU 23 receives the data of the identifier ID 600 from the communication line 25 and stores it. The second reception buffer 23b (shaded portion) of the T-CU 23 has no identifier (ID) setting in the system initial state after the in-vehicle communication system 12 has been assembled, that is, the de-energized state after the assembly, and the EG-CU 22 When the cruise control data of the identifier ID600 from “2” (ID600 [2]), that is, the EG-CU 22 recognizes the follow-up control of the C-CU 21 as a trigger, the T-CU of the identifier ID 500 from the C-CU 21 Receive cooperative data.

  The first transmission buffer 24a (shaded portion) of the M-CU 24 stores vehicle specification data (ID400) indicating the vehicle weight of the automobile 10, functions provided in the automobile 10, etc. (specifications). The vehicle specification data in the first transmission buffer 24a is sent to a control unit other than the C-CU 21, EG-CU 22 and T-CU 23, and is sent to a control unit (not shown) such as an anti-lock brake system.

  As shown in FIG. 4, the T-CU 23 is activated by energizing the in-vehicle communication system 12 by turning on an ignition switch (not shown) (step S <b> 1). In the subsequent step S2, the backup up RAM 40c of the T-CU 23 is read and it is determined whether or not the following cruise control presence flag bTK indicating whether or not the automobile 10 is equipped with the following cruise control function is set (bTK = 1?). To do. If it is determined in step S2 that the following cruise control is present (yes determination), the process proceeds to step S5. If it is determined in step S2 that no tracking cruise control is present (no determination), the process proceeds to step S3.

  In step S3, the reception state of the data of the identifier ID 600 (the cruise control data and the driving state data) transferred from the EG-CU 22 is confirmed. Here, it is determined whether or not the data of the identifier ID 600 is normal reception NG. If it is determined as normal reception NG (yes determination) in step S3, the process proceeds to step S8. If it is determined normal reception OK (no determination) in step S3, the process proceeds to step S4.

  In step S4, in response to the fact that the T-CU 23 has successfully received the data of the identifier ID 600 from the EG-CU 22, whether or not the data content of the identifier ID 600 is in operation of the following cruise control. It is determined whether it is other than “2”. If it is determined in step S4 that the control is not follow-up control (data “2”) (yes determination), the process proceeds to step S8. If it is determined in step S4 that the control is follow-up (no determination), the process proceeds to step S5.

  In step S5, in response to the yes determination in step S2, that is, the follow-up cruise control presence flag bTK is set, and in step S4, in response to the no determination, that is, the data content of the identifier ID 600 is the follow-up control. The port of the second reception buffer 23b is opened so that the data of identifier ID500 (T-CU cooperation data) can be received. In step S5, a follow cruise control presence flag bTK is further set (bTK = 1). Here, the time required from the tracking control operation to the reception of the data of the identifier ID500 is about 20 ms, and this delay time (about 20 ms) affects the cooperative control between the T-CU 23 and the C-CU 21. Will not affect.

  In the subsequent step S6, the information of the following cruise control presence flag bTK set in step S5 is stored in the backup RAM 40c of the T-CU 23. Here, the follow-up cruise control flag bTK is cleared only when the vehicle-mounted battery (not shown) is removed. Further, by storing the following cruise control presence flag bTK in the backup RAM 40c, the next time the ignition switch is turned on, the T-CU 23 can recognize from the beginning that there is a following cruise control (cruise control unit). As a result, an abnormal state of the following cruise control can be detected at an early stage, and a warning light or the like provided on the instrument panel or the like can be turned on to promptly notify the driver of the abnormal state.

  Thereafter, the process proceeds to step S7, and the recognition process of the C-CU 21 by the T-CU 23 ends. Note that the flowchart (C-CU recognition process) shown in FIG. 4 is always executed while the ignition switch is on.

  In step S8, yes determination is made in step S3, that is, the data of the identifier ID 600 transferred from the EG-CU 22 is normal reception NG (abnormal reception), and the data content of the identifier ID 600 transferred from the EG-CU 22 follows. In response to not being control (data “2”), the setting of the second reception buffer 23b of the T-CU 23 is set in the same manner as the previous control cycle, that is, the follow-up cruise control flag is set to bTK = bTKn-1 (previous value) And As a result, when communication abnormality occurs, data up to immediately before the abnormality detection is retained, cruise control at the time of abnormal recovery can be performed in a state closer to the specifications of the vehicle, and until the trigger of the following cruise control operation is detected, C -It is possible to stop the fault diagnosis for the communication of the CU 21 and suppress the erroneous diagnosis.

  As described above in detail, according to the in-vehicle communication system 12 according to the present embodiment, the C-CU 21, the EG-CU 22, and the T-CU 23 are connected to the communication line 25 arranged in the automobile 10, and the T- When the C-CU 21 operates and receives cruise control data from the EG-CU 22 in the system initial state of the automobile 10, the CU 23 directly receives T-CU coordination data from the C-CU 21 from the next control cycle. Therefore, it is not necessary to provide the T-CU 23 with a reception buffer for storing vehicle specification data indicating that the C-CU 21 is provided. Therefore, the data sent to the communication line 25 can be reduced in weight, and the number of reception buffers 40a (see FIG. 2) provided in the T-CU 23 can be reduced. As a result, high reliability and low cost of the in-vehicle communication system 12 can be ensured. Can be realized.

  It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the above embodiment, the present invention is applied to the high-speed CAN 20 that forms the in-vehicle communication system 12, but the present invention is not limited to this, and the present invention is applied to the low-speed CAN 30 that forms the in-vehicle communication system 12. Can be applied. Further, the present invention can be applied to both the high-speed CAN 20 and the low-speed CAN 30.

  In the above embodiment, the C-CU 21 is shown as the running state control unit. However, the present invention is not limited to this, and a brake control unit (BR-CU) for controlling the anti-lock brake system, etc. A control unit capable of cooperative control with the EG-CU 22 and the T-CU 23 can also be used.

  Further, in the above embodiment, the drive source control unit is the EG-CU 22, but the present invention is not limited to this, and the motor generator control unit (MG-CU) for controlling the motor generator of the electric vehicle is not limited thereto. ), Etc., and can be a control unit that can be cooperatively controlled with the C-CU 21 and the T-CU 23.

10 Automobile (vehicle)
12 In-vehicle communication system 21 C-CU (running state control unit)
22 EG-CU (drive source control unit)
23 T-CU (speed ratio control unit)
24 M-CU (Meter Control Unit)
40a reception buffer 40b transmission buffer 25 communication line

Claims (3)

An in-vehicle communication system comprising a plurality of control units connected to a communication line arranged in a vehicle and transmitting / receiving data to / from each other via the communication line,
A detection state from various sensors provided in the vehicle is stored in a reception buffer, a traveling state data of the vehicle is obtained and stored in a transmission buffer, and a traveling state control unit that sends the traveling state data to the communication line;
Drive source control for storing the running state data in a reception buffer, obtaining driving state data of a driving source provided in the vehicle, storing the driving state data in a transmission buffer, and sending the running state data and the driving state data to the communication line Unit,
A transmission ratio control unit that has a reception buffer for receiving the traveling state data and the driving state data, and that controls a transmission ratio of the vehicle based on the traveling state data and the driving state data;
The gear ratio control unit receives the traveling state data from the next control cycle when the traveling state control unit operates and receives the traveling state data from the drive source control unit in an initial system state of the vehicle. An in-vehicle communication system characterized by receiving directly from a state control unit.   The in-vehicle communication system according to claim 1, wherein the traveling state control unit is a cruise control unit that performs a follow-up control that maintains a constant inter-vehicle distance from a preceding vehicle.   The in-vehicle communication system according to claim 1 or 2, wherein a meter control unit is connected to the communication line, vehicle specification data is stored in a transmission buffer of the meter control unit, and the meter control unit includes the travel state control unit. The vehicle specification data is sent to a control unit other than the drive source control unit and the gear ratio control unit.

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