Vehicle-mounted communication system

Abstract

A communication network in which a plurality of terminals are connected to a common bus is a vehicle-mounted communication system which connects a plurality of ECUs though the bus, transmits messages at predetermined communication intervals between the ECUs, and receives the transmitted messages. The messages transmitted/received between the ECUs through a CAN communication line are divided into a plurality of groups such as a first group, a second group to an Nth group according to the type of message information. Each of the ECUs is provided with a transmission timing operation part for computing the transmission timing for each message group to be transmitted. The transmission timing operation part adjusts so as to bring the transmission timing of message belonging to the first group transmitted from its own ECU closer to the transmission timing of message belonging to the first group received from another electronic control unit.

What is claimed is: 
     
         1 . A communication system to be mounted on a car having a communication network in which a plurality of terminals is connected to a common bus, a plurality of electronic control units is connected to one another via said bus, and messages are sent among said electronic control units at predetermined transmission intervals and said sent messages are received thereby,
 wherein said messages sent and received among said electronic control units via said bus are divided into a plurality of groups such as a first group, a second group, . . . and an Nth group in dependence on a kind of message information;   each of said electronic control units has a transmission timing operation part computing transmission timings of messages of each group to be sent; and   said transmission timing operation part makes transmission timings of messages, belonging to the same group, which are to be sent from one of said electronic control units closer to transmission timings of messages, belonging to the same group, which are received from said other electronic control units than transmission timings of messages belonging to other groups.   
     
     
         2 . The communication system to be mounted on a car according to  claim 1 , wherein said transmission timing operation part adjusts transmission timings of messages so that transmission timings of messages, belonging to said first group, which are to be sent from one of said electronic control units are closer to transmission timings of messages, belonging to said first group, which are received from said other electronic control units than transmission timings of messages belonging to said second group through said Nth group; and
 adjusts transmission timings of messages so that said transmission timings of said messages belonging to said first group are distant from said transmission timings of said messages belonging to said second group through said Nth group which are different from said first group.