Abstract:
A communication system includes a main power line and a plurality of PLC networks connected to the main power line in common. At least one of the PLC networks includes a plurality of nodes. One node of the nodes in the PLC network is connected to the main power line. The other nodes are interconnected via a sub power line so as to receive power from the main power line through the one node. An inductor provided in the one node is connected to the main power line and the sub power line.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a vehicle information communication technology including a vehicle-mounted equipment control technology using PLC (Power Line Communication) for transmitting a control signal as well as power by using a power line for feeding power to a load.  
         [0002]     Power line communication (hereinafter referred to as PLC) is used as a communication method for controlling various types of electrical equipment mounted on an automobile such as a power window and a wiper.  
         [0003]      FIG. 3  is a conceptual illustration showing a configuration of a vehicle-mounted equipment control system using PLC as an example of a vehicle information communication system. The system shown in  FIG. 3  supplies power from a battery (not shown) to a plurality of loads  73  including electrical equipment, and a master controller  74  (hereinafter referred to simply as a master) and a slave controller  75  (hereinafter referred to simply as a slave) for controlling these loads via a junction connector (J/C)  72  connected to a power line  71 . The slave  75  is a controller provided for each load  73  while the master  74  is a controller for controlling the loads  73  via the slaves  75 . In this system, the master  74  transmits a communication signal M to the slave  75  as a distant party via a power line (a power line in the PLC network is hereinafter referred to as a sub power line)  77  in a PLC network  76  interconnected by the junction connector  72 . The slave  75  receives the communication signal M via the sub power line  77  and transmits, via the sub power line  77 , a communication signal S indicating the state of the load  73  controlled by the slave  75 . The master  74  transmits a communication signal M corresponding to the communication signal S received from the slave  75 . The master  74  and each slave  75  control the respective loads  72  while communicating with each other via the sub power line  76  (refer to JP-A-2003-118509).  
         [0004]     A vehicle-mounted equipment control system using PLC is capable of performing proper control operation in case the PLC network exists alone as shown in  FIG. 3 , because communication between the master and the slaves are kept stable. In case two PLC networks  89 ,  90  are adjacent to each other via the main power line  71  as shown in  FIG. 4 , interference between the PLC networks  80 ,  90  may cause improper control operation. In the example of  FIG. 4 , a communication signal SigA communicated between the master  83  and the slave  84  in the PLC network  80  invades, via the main power line  71 , the PLC network  90  that is adjacent to the PLC network  80 , thus interfering with the communication in the PLC network  90 . Conversely, a communication signal SigB in the PLC network  90  invades the PLC network  80  via the main power line  71 , thus interfering with the communication in the PLC network  80 .  
         [0005]     In order to solve such a problem, a related art technology inserts an inductor into a main power line between PLC networks coupled to a pole-mounted transformer for feeding power to a home or office in order to prevent interference between PLC networks (refer to JP-A-2001-358618).  
         [0006]     By applying the related art to the vehicle-mounted equipment control system shown in  FIG. 3 , that is, by additionally inserting an inductor into the main power line  71  or sub power line connecting the PLC networks  80  and  90 , it is possible to interrupt an interference-causing signal over the main power line  71 . In a system that performs driving control of equipment mounted on a vehicle, it is difficult to reserve a space for inserting an inductor. Moreover, an additional inductor results in a higher cost. Thus, the approach is not impractical.  
       SUMMARY OF THE INVENTION  
       [0007]     The invention has been accomplished in view of the above circumstances and has as an object to provide a vehicle information communication system using PLC capable of preventing interference between PLC networks connected to a common main power line without additionally inserting an inductor into the main power line.  
         [0008]     In order to attain the object, the invention provides a communication system, comprising:  
         [0009]     a main power line; and  
         [0010]     a plurality of PLC networks connected to the main power line in common,  
         [0011]     wherein at least one of the PLC networks includes a plurality of nodes  
         [0012]     wherein one node of the nodes in the PLC network is connected to the main power line;  
         [0013]     wherein the other nodes are interconnected via a sub power line so as to receive power from the main power line through the one node; and  
         [0014]     wherein the one node has an inductor that is connected to the main power line and the sub power line.  
         [0015]     Preferably, a circuit for reserving impedance in the one node serves as the inductor.  
         [0016]     Preferably, the other nodes are sub controllers that are respectively connected to loads. The one node is a master controller that controls the loads through the sub controllers.  
         [0017]     According to the present invention, there is also provided a PLC network, comprising:  
         [0018]     a plurality of nodes,  
         [0019]     wherein one node of the nodes is connected to a main power line, the main power line being connected to other PLC network in common;  
         [0020]     wherein the other nodes are interconnected via a sub power line so as to receive power from the main power line through the one node; and  
         [0021]     wherein the one node has an inductor that is connected to the main power line and the sub power line.  
         [0022]     Preferably, a circuit for reserving impedance in the one node serves as the inductor.  
         [0023]     Preferably, the other nodes are sub controllers that are respectively connected to loads. The one node is a master controller that controls the loads through the sub controllers.  
         [0024]     With the configurations, a signal leaving the PLC network, that is, a signal leaking into the main power line must pass through the inductor in the one node so that the leaked signal is attenuated. Similarly, a signal invading the PLC network from another PLC network via the main power line must pass through the inductor in the one node thus the invaded signal is attenuated. Therefore, it is possible to prevent interference between PLC networks connected to a common main power line without additionally inserting an inductor into the main power line.  
         [0025]     In the communication system according to the invention, an existing circuit for reserving impedance in the one node such as an LC resonator circuit may be used as the inductor.  
         [0026]     The communication system according to the invention uses an existing inductor in a node in a PLC network to prevent interference between PLC networks connected to a common main power line. This eliminates the need fir additionally inserting an inductor for attenuating a signal into a main power line. It is thus possible to provide, readily and cost-effectively, a system capable of precisely controlling vehicle-mounted equipment without malfunction caused by interference between PLC networks.  
         [0027]     The invention has been briefly described. Details of the invention will be further clarified by reading the following description of the best embodiments for implementing the invention while referring to the attached drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]     The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein:  
         [0029]      FIG. 1A  is a conceptual illustration showing a vehicle-mounted equipment control system as an example of a vehicle information communication system according to a first embodiment of the invention;  
         [0030]      FIG. 1B  is a conceptual illustration showing an example of a PLC network;  
         [0031]      FIG. 2  is a conceptual illustration showing a vehicle-mounted equipment control system according to a second embodiment of the invention;  
         [0032]      FIG. 3  is a conceptual illustration of a vehicle-mounted equipment control system having a single PLC network; and  
         [0033]      FIG. 4  is a conceptual illustration of a vehicle-mounted equipment control system in which interference between adjacent PLC networks is occurred. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]     Best embodiments for implementing the invention will be described below.  
         [0035]      FIG. 1A  is a conceptual illustration showing a vehicle-mounted equipment control system as an example of a vehicle information communication system according to a first embodiment of the invention. In  FIG. 1 , numerals  10 ,  20  represent PLC networks. These networks are in such close proximity to each other as to cause serious interference. The PLC networks  10 ,  20  are respectively connected to a main power line  30  for transmitting power from a battery (not shown).  
         [0036]     The PLC networks  10 ,  20  respectively have four nodes; that is, one master  40  ( 40 A,  40 B) and three slaves  50  ( 50 A,  50 B). The master  40  of each PLC network  10 ,  20  is connected to the main power line  30  via a wire harness  35  ( 35 A,  35 B). The master  40  also functions as a junction connector. The master  40  and the slaves  50  in each PLC network  10 ,  20  are interconnected via a sub power line  36  ( 36 A,  36 B) so as to feed power from the main power line  30  to the slaves  50  via the master  40 . The slave  50  is a controller provided for each load  55  ( 55 A,  55 B) while the master  40  is a controller for controlling each load  55  via each slave  50 .  
         [0037]      FIG. 1B  shows the internal configuration of the master  40  and the slave  50 .  
         [0038]     The master  40  has a transceiver  41 , a band-pass filter (BPF)  42 , and an inductor  43  for reserving impedance. The transceiver  41  and the band-pass filter  42  are connected via a signal line  45 . The band-pass filter  42  is connected to a sub power line  36  and transmits only a communication signal in a predetermined band superimposed over the sub power line  36 . The transceiver  41  communicates with each slave  50  while using the sub power line  36  as a signal transmission line through the band-pass filter  42 . The inductor  43  for reserving impedance is inserted midway in a power line  44  connecting the transceiver  41  and the main power line  30 . A wire harness  35  is connected between the inductor  43  for reserving impedance and the transceiver  41 . Power transmitted from the main power line  30  via the wire harness  35  is fed to the transceiver  41  in the master  40  as well as fed to each slave  50  via the inductor  43  for reserving impedance and in the master  40  and the sub power line  36 .  
         [0039]     Each slave  50  has a transceiver  51 , a band pass filter  52 , an inductor  53  for reserving impedance, and a load controller  54 . The transceiver  51  and the band-pass filter  52  are interconnected via a signal line  56 . The band-pass filter  52  is connected to a sub power line  36  and transmits only communication signals M (MA, MB) and S(SA, SB) in a predetermined band superimposed over the sub power line  36 . The transceiver  51  communicates with the master  40  while using the sub power line  36  as a signal transmission line through the band-pass filter  52 . The inductor  53  for reserving impedance is inserted midway in a power line  57  connecting the transceiver  51  and the sub power line  36 . Power transmitted to the slave  50  via the sub power line  36  is fed to the transceiver  51  via the inductor  53  for reserving impedance. The load controller  54  receives a communication signal M from the master  40  via the transceiver  51  and controls the load  55  in accordance with the communication signal M as well as transmits a communication signal S corresponding to the state of the load  55  to the master  40  via the transceiver  51 .  
         [0040]     PLC operation of the vehicle-mounted equipment thus configured is as follows.  
         [0041]     The master  40 A in the first PLC network  10  transmits a communication signal MA to the slave  50 A as a distant party via the sub power line  36 A in the first PLC network  10 . The slave  50 A, receiving the communication signal MA from the master  40 A, transmits a communication signal SA indicating the state of the load  55 A controlled by the slave  50 A to the master  40 A via the sub power line  36 A in the first PLC network  10 . The master  40 A transmits the communication signal MA corresponding to the communication signal SA received from the slave  50 A. In this way, the master  40 A and each slave  50 A in the first PLC network  10  control the respective loads  55 A while communicating with each other via the sub power line  36 A in the first PLC network  10 .  
         [0042]     The master  40 B in the second PLC network  20  transmits a communication signal MB to the slave  50 B as a distant party via the sub power line  36 B in the second PLC network  20 . The slave  50 B, receiving the communication signal MB from the master  40 B, transmits a communication signal SB indicating the state of the load  55 B controlled by the slave  50 B to the master  40 B via the sub power line  36 B in the second PLC network  20 . The master  40 B transmits the communication signal MB corresponding to the communication signal SB received from the slave  50 B. In this way, the master  40 B and each slave  50 B in the second PLC network  20  control the respective loads  55 B while communicating with each other via the sub power line  36 B in the second PLC network  20 .  
         [0043]     While each PLC network  10 ,  20  is performing PLC-based master-slave communication, part of a communication signal communicated in each PLC network  10 ,  20  leaks into the main power line  30 . The signal leaking into the main power line  30  from each PLC network  10 ,  20  must pass through the inductor  43  for reserving impedance in the master  40  so that the leaked signal is attenuated. Similarly, a signal invading the PLC network  10 ,  20  from outside must pass through the inductor  43  for reserving impedance so that the invaded signal is attenuated. As a result, interference between the PLC networks  10  and  20  is prevented.  
         [0044]     As mentioned above, the vehicle-mounted equipment control system according to the first embodiment uses the existing inductor  43  in the master  40  that is a node in the PLC network  10 ,  20  as an inductor for attenuating a signal in order to, prevent interference between the PLC networks  10  and  20 . With this system configuration, it is not necessary to additionally insert an inductor for attenuating a signal into the main power line  30 . It is thus possible to provide, readily and cost-effectively, a system capable of precisely controlling vehicle-mounted equipment without malfunction caused by interference between the PLC networks  10  and  20 .  
         [0045]     While the inductor  53  for reserving impedance in the master  40  is used as an inductor for attenuating a signal in the above embodiments, an LC resonator circuit  46  may be used as an inductor for attenuating a signal (a circuit for reserving impedance) as shown in  FIG. 2 .  
         [0046]     While power is fed to each slave  50  via the master  40  in the first and second embodiments, it is also possible to feed power to any one slave  50  and then to the master  40  and the remaining slaves  50  as well as use the inductor  53  in the one slave  50  as an inductor for attenuating a signal.  
         [0047]     The invention is not limited to the embodiments but various changes or improvements of the invention are possible as required. The form, quantity, and location of each component in the foregoing embodiments are arbitrary and are not limited as long as the purpose of the invention is attained.