Apparatus for multiplexing between units in a vehicle

Abstract: A multiplexing apparatus multiplexes between processing units and a battery unit of a vehicle which are connected to one another by wire harnesses, by grouping a variety of on-board controlled objects into a plurality of neighboring controlled objects and controlling each of the groups by respective processing units. The wire harness has electric conductors of which the outer peripheral portion are covered with a first insulating layer, electric conductivity layer which covers the electric conductors, a second insulating layer which covers the peripheral portion of the electric conductivity layer, means for applying an electric potential to said electric conductivity layer, and means for monitoring the electric potential of said electric conductivity layer.

Description: BACKGROUND OF THE INVENTION The present invention relates to an apparatus for multiplexing between on-board units of a vehicle by using wire harnesses. Recently, various controls in a vehicle are performed by an on-board computer and the associated electrically controlled equipments. Thus, large amounts of electric wiring are used in the vehicle. Those electric wiring such as the wire harnesses have the potential for causing short-circuit. Therefor, various apparatus for detecting the short-circuit of wire harnesses for power supply are proposed in the past. One of them is disclosed in Japanese Patent publication No.4-17809 (1992), in which the rated consumption currents for respective loads are calculated in advance, the occurrence of anormality due to the short-circuit is detected by comparing sum of the rated consumption currents with sum of the current one in the vehicle. A similar technique is disclosed in GB-A-2277618 and EP-A-0029406 which is related to a flexible electric connection cord of mobile cutting tools with a protection device. The document GB-A-2277618 discloses the preamble of claim 1. However, when a wire harness is installed into a vehicle body, the harness may be jammed into the vehicle body and/or the coating of the harness may be broken due to the rubbing of the harness on metal portions of the vehicle body. Therefore, a core wire of an electric power source may short to an ground portion of the vehicle body, and thus serious accidents such as the fire of the vehicle may break out in the worst case. In the above prior art, it is constructed such that the serious accidents can be prevented immediately by cutting off the whole current. Therefore, when such the accidents occurs during driving, a power source is cut off. As a result, the vehicle stops suddenly. Further, when the driver changes the load of an electric system, it is required to change the predetermined rated value. Therefore, there was a possibility that a malfunction occurs. In addition, while the short-circuit of the wire harness can be detected, the processing after the detection of the short-circuit can not be performed. SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus for multiplexing between on-board units of a vehicle, which can detect at an early stage the short-circuit of the wire harness. Another object of the present invention is to provide an apparatus for multiplexing between on-board units of a vehicle, which can perform a suitable processing when the short-circuit of the wire harness is detected, thereby the serious accident can be prevented in advance. These objects are achieved according to the present invention by an apparatus as defined in claim 1. Advantageous embodiments are claimed in dependent claims 2 to 11. BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, like reference numerals denote like parts in the various views. Fig. 1 is a perspective view showing the configuration of a wire harness used in an embodiment of the present invention. Fig.2 is a circuit diagram showing a short-circuit detecting circuit using the wire harness shown in Fig. 1. Fig. 3 is a perspective view showing a tape formed by a conductor member for detecting the short-circuit and an insulator member used in another embodiment of the present invention. Fig. 4 is a perspective view showing the structure of the wire harness in which the tape shown in Fig.3 is wound around electric conductor wires. Fig. 5 is a view showing the structure of the conductor member for detecting the short-circuit and insulator member used in a further embodiment of the present invention. Fig. 6 is a view showing the structure of the conductor member for detecting the short-circuit and insulator member used in a further embodiment of the present invention. Fig. 7 is a schematic view of connection means for fixing the conductor member and connecting it the conductor wire. Fig. 8 is a schematic view showing the structure of the wire harness to which the structure shown in Fig.7 is applied. Fig. 9 is a perspective view showing the structure of the wire harness which has double structure made of the conductor member and the insulator member. Fig.10 is a circuit diagram showing the short-circuit detecting circuit using the wire harness with the structure shown in Fib. 9. Fig. 11 is a circuit diagram showing an example of an alarm system for ground-short using the wire harness with the structure shown in Fig. 9. Fig. 12 is a flow chart showing the procedure of processing in the alarm system for ground-short using the wire harness with the structure shown in Fig. 9. Fig. 13 is a circuit diagram showing a lighting circuit for an on-board lamp using the wire harness, with the function of detection of the short-circuit used in the present invention. Fig. 14 is a circuit diagram showing the internal construction of a controller shown in Fig. 13. Fig. 15 is a block diagram showing an example in which the wire harness with the function of detection of the short-circuit is applied to a multiplex communication system used in a vehicle (In-vehicle LAN). Fig. 16 is a flow chart showing the procedure of communication processing in an In-vehicle LAN shown in Fig. 15. Fig. 17 is a flow chart showing the procedure of processing in a sub-routine of the processing shown in Fig. 16 carried out at the time of the cable short-circuit. Fig. 18 is a view showing the relationship between points, and place, frequency and importance in the sub-routine of step S41 of Fig.17. Fig. 19 is an illustration showing an example in which the conductor member for detection of the short-circuit having a resistance value is wound on a cylindrical form. PREFERRED EMBODIMENTS OF THE INVENTION Embodiments of the present invention will be explained hereinafter with reference to the drawings. Fig. 1 shows the structure of a wire harness according to the present invention. Electric wires 3, 4 and 5 are covered with an insulating layer, and further covered with an electric conductor member 2 for the detection of short-circuit. The wire harness 1 formed by covering the outside of the conductor member with an insulating member 6. The insulating member 6 protects the conductor member 2 for the detection of short-circuit and the electric wires 3, 4, 5, and ties them in a bundle. In addition, the insulating member 6 protects the conductor member 2 from short-circuitting to the ground of a vehicle. An electric conductor wire 7 is provided for the connection to an external equipment. The wire harness according to this embodiment has the structure substantially identical to a three-core shield wire. Therefore, in this embodiment, the electric wires 3, 4, 5 functions as electric conductivity means, and one of three electric wires acts as a electrical communication wire. Further, the conductor member 2 for the detection of short-circuit functions as an electric conductivity layer and the insulating member 6 functions as an electrically insulating layer. Fig.2 shows an example of a short-circuit detecting circuit. In Fig.2, an electric potential is applied through a pull-up resistor R1 to the conductor member 2 for the detection of short-circuit connected to a + (plus) terminal of a comparator 8. The voltage divided by resistors R and r is applied to a - (minus) terminal of the comparator 8. v = v * r / (R + r) An output S1 of the comparator 8 indicates a high level when the short-circuit detecting conductor member 2 is at a normal state, or when it is not short-circuited to the ground. While, the output S1 indicates a low level when the conductor member 2 is short-circuited to the ground, for example, due to the damage of the insulating member 6. It is, therefore, possible to detect the short-circuit of the wire harness to the ground by monitoring the output of the comparator 8. In this embodiment, the pull-up resistor acts as means for applying an electric potential to the electric conductivity layer, and the comparator acts as means for monitoring the electric potential. Fig. 3 shows another embodiment of the wire harness according to the present invention, which shows in detail a portion of the short-circuit detecting conductor member and the insulating member. The insulating member 9 is made of a flexible member such as a vinyl tape, inside of which a conductor member 10 is embeded. An adhesive agent 11 in addition to the insulating member 9 and the conductor member 10 forms a tape 12 wound around the wire harness. By forming in such a way, it becomes easy to detect the short-circuit, because the electric potential of the conductor member 10 drops to the ground potential when the ground-short is occurred by the breakage due to the rubbing of the insulating member 9. Fig. 4 shows the structure of the wire harness in which the tape 12 shown in Fig. 3 is wound around the conductor wires 3, 4 and 5. The short-circuit detecting circuit has the same construction as that shown in Fig. 2. The winding of the tape 12 may be overlapped, or may not be overlapped. Fig. 5 shows a further embodiment of the present invention, which shows the structure of the conductor member for detecting the short-circuit and the insulator member. In Fig. 5, the insulator member 13 is made of a flexible insulating member such as a vinyl tape. A conductor member 14 inside of the insulator member 13 is made of a flexible conductivity member such as an aluminium tape. The electric wires 3, 4, 5 are covered in order by the conductor member 14 and the insulating member 13 thereon. Further, there is no problem even if a different conductor or insulating member is provided between the electric wires 3, 4, 5 and the conductor member 14. The short-circuit detecting circuit has the same construction as that shown in Fig.2. Fig. 6 shows the structure of the conductor member for detecting the short-circuit and insulator member used in a further embodiment, of the present invention. In Fig.6, the insulator member 13 is made of a flexible insulating member such as a vinyl tape. The conductor member 14 inside of the insulator member 13 is made of a flexible conductivity member such as an alminium tape. The electric wires 16, 17, 18 are covered in order by the conductor member 14 and the insulating member 13 thereon. In this embodiment, the electric wires 16, 17, 18 is printed on a flexible substrate 19. The short-circuit detecting circuit has the same construction as that shown in Fig.2. Fig.7 shows connection means for fixing the conductor member 14 and connecting it the conductor wire 7. As understood from Fig.7, the connection means 15 has such the structure that the conductor wire 7 is connected to a ring-shaped conductor member 20 with a partially cut-away portion 20a. Fig. 8 shows the construction of the wire harness to which the connection means 15 shown in Fig. 7 is applied. In Fig. 8, the connection means 15 is made by attaching and swaging the ring-shaped conductor member 20 around the conductor member 14 of the wire harness 1, thereby holding a sufficient connection between the wire harness and the conductor member 20. The partially cut-away portion 20a is provided to ensure the margin for swaging. The connection provides the conductivity between the conductor member inside the insulating member 13 and the conductor member 20 of the connection means 15. Thereby, the electric potential is applied to the conductor member 14 through the conductor wire 7 connected to the conductor member 20. Further, the connection means 15 also act to bind the electric wires 3, 4, 5 and the conductor member 14. Fig.9 shows the structure of the wire harness which has double structure made of the conductor member and the insulator member. A first insulating member 21 at the outest periphery of the wire harness is used for protecting the whole wire harness. While a first conductor member 22 in the outest periphery is used as means for detecting the ground-short of the wire harness, only alarm is raised even if the conductor member 22 short-circuits, because there are provided a second conductor member 14 and a second insulating member inside the first conductor member. A conductor wire 23 is used for applying an electric potential to the first conductor member 22. If the second insulating member 13 suffers damage after the damage of the first conductor member 22, and the second conductor member 14 short-circuits to the ground, the inside wires 3, 4, 5 may suffer damage in a short time. Therefore, the abnormality is alerted to a driver in another way except the alarm. The conductor wire 7 is used for applying an electric potential to the second conductor member 14. while in this example the conductor members and the insulating members are combined double, it is possible to combine them more than double layers. Fig. 10 shows the short-circuit detecting circuit using the wire harness with the structure shown in Fig.9. In Fig. 10, an electric potential V1 is applied through a pull-up resistor R1 to the first conductor member 22 connected to a + (plus) terminal of a comparator 24. As described with respect to the equation (1), the voltage divided by resistors R and r is applied to a - (minus) terminal of the comparator 24. An output S1 of the comparator 24 indicates a high level when the first conductor member 22 is at a normal state, or when it is not short-circuited to the ground. While, the output S1 indicates a low level when the first conductor member 22 is short-circuited to the ground, for example, due to the damage of the insulating member of the first conductor member 22. Further, an electric potential v2 is applied through a pull-up resistor R2 to the second conductor member 14 connected to a + (plus) terminal of a comparator 25. As described with respect to the equation (1), the voltage obtained by dividing the voltage V by resistors R and r is applied to a - (minus) terminal of the comparator 25. An output S2 of the comparator 24 indicates the high level when the second conductor member 14 is at a normal state, or when it is not short-circuited to the ground. While, the output S1 indicates the low level when the second conductor member 14 is short-circuited to the ground, for example, due to the damage of the insulating member of the second conductor member 14. It is, therefore, possible to detect the ground-short of the wire harness including its risk by monitoring the outputs of the comparators 24 and 25. Fig.11 is a circuit diagram showing an example of an alarm system for ground-short using the double-layer type wire harness with the structure shown in Fig. 9. In Fig. 11, a current from the power source is supplied from a - (minus) terminal of the battery through link 31 and emergency cut-off relay 32 to other loads. The current from the power source is also supplied through a fuse 34 and a regulator 35 to the control means or a processor 33. The short-circuit of the first conductor member 22 is detected by the first comparator 24, and the short-circuit of the second member 14 is detected by the second comparator 25. Outputs of those comparators are input to processor 33. The processor 33 processes the outputs according to the procedure shown in Fig. 12, and determines the risk of short-circuit. Namely, when the first conductor member 22 is short-circuited, a alarm lamp is lighted and caution is given to a driver. When the second conductor member 14 is short-circuited, it is determined that the wire harness will become dangerous, and a driver 37 is cut off and thus a relay 32 is cut off. As a result, the whole power of a vehicle is cut off. Referring now to Fig. 12, Fig.12 is a flow chart showing the procedure of processing in the alarm system for ground-short using the wire harness with the double-layer structure shown in Fig. 9. In step S1, an output of the first comparator (A) 24 is checked, which detects the short-circuit of the first conductor member 22. If the output is at the low level, then the processing advances to step S7. In step S3, an output of the second comparator (B) 25 is checked, which detects the short-circuit of the second conductor member 14. If the output is at the high level, then it is determined that the wire harness is short-circuited, and a counter B for the detection of the short-circuit of the first conductor member 14 is incremented in step S4. If the output is at the low level, then the process advances to step S5. In step S5, the value of the counter B is compared with the predetermined threshold value N2. If the value of the counter B is equal to or larger than the predetermined threshold value N2, then it is determined that the short-circuit of the second conductor is deteriorated. In step S6, a main relay 32 for the power source is cut off and the system is shut down. While, if the value of the counter B is smaller than the predetermined threshold value N2, then the process returns to START. Further, if the output of the second comparater (B) is at the low level in step S3, then the value of the counter (A) is compared with the predetermined threshold value N1 in step S8. In this case, if the value of the counter (A) is equal to or larger than the value N1, then it is determined that the short-circuit of the first conductor 22 is deteriorated. In step S9, a warning flag is stood and the alarm lamp is lighted. If the value of the counter (A) is smaller than the value N1, then the process is returned to START. In step S7, it is checked whether or not the first conductor member 22 is short-circuited. If the first conductor member 22 has already been short-circuited, then the process advances to step S3, and if it has not been short-circuited, then the process returns to START. Fig. 13 shows a lighting circuit for an on-board lamp using the wire harness with the function of detection of the short-circuit used in the present invention. A current from the battery 30 is controlled by a switch 40 and a lamp load 41 is put on or off. Wires are connected through connectors 42 and 43. Short-circuit detecting conductor members 44, 45, 46, 47 are connected between the battery 30 and the connector 42, between the connector 42 and the controller 48, between the controller 48 and the connector 43, between the connector 43 and the lamp 41, respectively. Namely, the conductor members 44 to 47 are electrically connected to a single controller (control means) 48. When each of the short-circuit detecting conductor member is short-circuited over the predetermined times, the alarm is raised by an alarm lamp 49 connected to the controller 48. Fig. 14 shows the internal construction of the controller shown in Fig. 13. In the controller 18, there are provided comparators 51 to 54 in the controller 48, which check output voltages of the short-circuit detecting conductor members 44 to 47. When the wire harnesses are not short-circuited, voltages V1 to V4 are applied through pull-up resistors R1 to R4 to + (plus) input terminal of the comparators 51 to 54, respectively. An electric potential of the plus input terminal is at the ground when the wire harnesses are short-circuited. While, the voltage obtained by dividing a voltage v by using resistors R and r as shown in the equation (1) is applied to - (minus) input terminal. An output of each of the comparators is input to a CPU 55. When the output at the high level is occurred over the predetermined times, it is assumed that the conductor member is short-circuited to the ground. As a result, the alarm lamp is lighted. Fig.15 is a block diagram showing an example in which the wire harness with the function of detection of the short-circuit is applied to a multiplex communication system used in a vehicle (hereinafter, referred to as an In-vehicle LAN). The In-vehicle LAN comprises one BCM (Body Control Module - control processing unit) 102, a first, a second and a third LCU (Local Control Unit - terminal processing unit) 103, 104, 105, a first, a second and a third combination cable (wire harness) 107, 108, 109, each of which is connected between the processing units, a fourth combination cable 106, and a battery 101 connected through the fourth combination cable 106 to the BCM 102. This In-Vehicle LAN system is called as a central control type. A buzzer 110 and a first and a second lamp 111, 112 are connected to a BCM 102. A power cable (the fourth combination cable) connected between the battery 101 and the control processing unit BCM 102 is constructed as a combination cable of a communication wire and a short-circuit detecting wire harness. The first LCU 103 is connected through the first combination cable 107 to the BCM 102. The first LCU 103 is also connected to a first and a second motor 113, 114, and a first and a second operating switch 119, 120 each for operating these motors 113, 114. The second LCU 104 is connected through the second combination cable 108 to the first LCU 103. The second LCU 104 is also connected to a third and a fourth motor 115, 116, and a third and a fourth operating switch 121, 122. The third LCU 105 is connected through the first combination cable 109 to the second LCU 104. The third LCU 105 is also connected to a third and a fourth lamp 117, 118. The BCM 102 transmits and receives data through combination cables to and from the fist LCU 103 and the third LCU 105, and outputs a command signal to control an actuator connected to each of LCUs 103 to 105 on the basis of information obtained from the first, the second, the third LCUs 103, 104, 105 through electrical communication. There are provided the first to the fourth operation switches 119 to 122, the buzzer 110, the first to the fourth lamps 111, 112, 117, 118, the first to the fourth motors 113 to 116 in the neighborhood of a plurality of electric equipments in the system. They are connected to any one of the first to the third LCU 103 to 105 and the BCU 102. Further, the short-circuit detecting circuits or the combination cables 106 to 109 is incorporated in the BCU and the LCUs 103 to 105. The BCM 102 detects the short-circuit of the fourth combination cable, the first LCU 103 the first combination cable, the second LCU 104 the second combination cable, and the third LCU 105 the third combination cable. A brief explanation of a series of data transmission will be given next. When the BCM 102 transmits a certain data to an LCU, the LCU which received the data answers the input data itself back to the BCU. Therefore, first, a data transmission signal directed from the BCU 102 to any one of the LCU 103 to 105 appears in a communication wire of the combination cable, and then a data reception signal directed from any one of the LCU 103 to 105 to the BCM 102 appears in the same communication wire. A set of the transmission and reception signals as described above are supplied to other LUCs in the same way. The data answered to the LCU 103 to 105 is input to a self-contained load control unit, and operates actuators such as the said motors 113 to 116. Further, signals indicative of the state of various operating switches 119 to 122 is answered to the BCM 102, which the LCUs 103 to 105 input. these signals indicate operation to be required. Fig. 16 is a flow chart showing the procedure of the whole communication processing. The communication processing shown in Fig. 16(a) expresses the processing steps in which the BCH 102 communicates with the LCUs 103, 104 and 105, and BGJ (Back Ground Job) shown in Fig. 16(b) is the assembly of processing 1 (step S31) to processing n (step S3n) to determine how to control on the basis of the reception data. The BGJ processing is endless processing performed when other processing does not performed. For example, if it is required to perform the communication processing when the processing 1 (step S31) is now performing, the communication processing is performed after the communication processing 1 (step S31) is temporarily interrupted, and the processing 1 is performed from the point where the processing 1 is interrupted before. The communication processing is reception interruption processing performed when the reception data reaches from the LCUs 103 to 105 to the BCM 102. In this processing, the data from LCUs 103, 104, 105 is first received in step S21. After that, it is checked whether or not the combination cables 106 to 109 are short-circuited in step S22. If it is determined that the short-circuit is occurred in the combination cables, then the processing after the short-circuit of cable is performed in step S23. The next LCU to be accessed is selected in step S24 and the data is transmitted to the selected LCU in step S25. While, if in step S22, it is determined that no short-circuit is occurred, then the next LCU to be accessed is selected in step S24 without performing the processing after the cable short-circuit, and the processing for the data transmission is performed in step S25. Fig.17 is a flow chart showing the procedure of processing carried out at the time of the cable short-circuit. In step S41, the position of occurrence of the short-circuit in the combination cables 106 to 109 is identified. An described above, because the BGM 102 and each of the LCUs 103 to 105 detect the short-circuit of the combination cables 106 to 109, it is possible to detect easily which combination cable is short-circuited. After the short-circuit of the combination cables is detected, the number of occurrence of the short-circuit is detected. Where, the number of occurrence per unit time is expressed as frequency. Next, the importance, that is, the extent of whether or not the failure caused by the short-circuit extends to safety components such as a head-light, is detected. These detected data are used as parameters in the calculation of points. The points are calculated by using a map as shown in Fig.18, and the total points indicate the level of emergency. In other words, the processing in step S41 indicates the extent of the state of the currently occurred short-circuit. When the emergency level is calculated as described above, levels 1 to 4 are selected according to the calculated level in step S42. this processing is temporary alarm processing. If the conditions with respect to the points is satisfied, or the ignition key is turned on, the alarm indicative of them is raised just once. While, When the total points are equal to or more than 15 and less than 20, the processing corresponding to the emergency of level 2 is performed in step S44. This processing is continuous alarm processing. In this case, the alarm is raised continuously or interruptly. Therefore, the alarm is given earlier to a driver. When the total points are equal to or more than 20 and less than 40, the processing corresponding to the emergency of level 3 is performed in step S45. In this processing, a current from the power source to the downstream is cut off at the LCUs 103 to 105 upstream of the position where the short-circuit of the combination cable is occurred, and the continuous alarm is raised in step 46 in a way similar to that of Step 44. Because the current from the power source is cut off at the position of occurrence of the short-circuit, it becomes possible to prevent the worst condition which causes vehicle fire even if the short-circuit is deteriorated, and raise confirmly an alarm to a driver. Next, When the total points are equal to or more than 40, the processing corresponding to the emergency of level 4 is performed in step S47. This processing is performed in such a case that the short-circuit of the combination cable may occur at the position nearer the battery 101. In the level 4, the whole power source in the LAN system is cut off, thereby preventing the occurrence of fire of the short-circuit. When the total points are less than 5, no processing is performed. By performing the processing described above, it is possible to alert a driver with the occurrence of short-circuit and further repair, and prevent the occurrence of the vehicle fire in advance because the power source is cut off in the case that the short-circuit occurs frequently. It should be appreciated that it is possible to cut away only the cable at the position where the short-circuit is occurred such that the electric power can be supplied from another circuit by using looped combination cable. Further, the position where the short-circuit occurs can be easily known through the LAN communication. Furthermore, because the occurrence of the short-circuit is transmitted to each of the LCUs 103 to 105, at the occurrence of the short-circuit, it is possible to carry out special control processing, for example, the neglect of the data obtained from the position where the cable is cut away and the estimation of the data. Further, Because the LAN system grasps the conditions of operation, it is possible to detect the short-circuit of a wire harness also during driving or parking. Therefore, in the case that the wire harness is short-circuited due to external vibration, it is possible to cut off instantly the power source. Fig.19 is an illustration showing an example in which the conductor member 60 for detection of the short-circuit having a resistance value A (Ω / m) is wound on a cylindrical body with radius R. Fig. 19(a) shows the form of the wounded conductor member, and Fig. 19(b) shows the relationship between the angle to be wound and the width of the conductor member. Assumed that the width of the conductor member is d and the conductor member is wound around without gap. cos  = d / 4 R Therefore, the value of the resistor R0 per one round is When the voltage V is applied to the conductor member by using the pull-up resistor R2, the electric potential vx is Vx =V * R0 * N / (R0 * N + R2) where, N is a turn number. The determination of the position where the ground-short is occurred is calculated by measuring the Vx and obtaining the N. Namely, N=R2 / R0 * Vx / (V - Vx) Accordingly, it is possible to determined the position where the ground-short is occurred.

Claims: An multiplexing apparatus for multiplexing between processing units of a vehicle which are connected to one another and a battery unit by wire harnesses, by grouping a plurality of controlled on-board devices into a plurality of neighboring controlled devices and controlling each of the groups by respective processing units, said wire harness comprising electric conductors (3, 4, 5) of which the outer peripheral portions are covered with a first insulating layer, an electric conductivity layer (2) which covers said electric conductors (3, 4, 5), and a second insulating layer (6) which covers the outer peripheral portion of said electric conductivity layer (2), characterized in that said multiplexing apparatus includes applying means to apply to said electric conductivity layer (2) a known predetermined electric potential, a voltage comparing means (8) for comparing its reference voltage and the known predetermined electric potential to be capable of detecting a short-circuit abnormality on the basis of the difference between the reference voltage and the known predetermined electric potential, and data storing means for storing the data used to estimate damages by using at least one of the frequency of occurence of the short-circuit of the wire harness to the ground, the term of time of the short-circuit, the position of the short-circuit and the importance of the short-circuit, as parameters. The multiplexing apparatus according to claim 1, wherein said electric conductivity layer (2) is formed by a thin mesh wire. The multiplexing apparatus according to claim 1, further comprising alarm means for raising an alarm to a driver, and control means for starting up said alarm means to raise the alarm. The multiplexing apparatus according to claim 3, further comprising: a circuit breaker for cutting off the current passing through said electric conductor (3, 4, 5) from a power source when a short-circuit of the wire harness to the ground is detected by said detecting means. The multiplexing apparatus according to any one of the previous claims, further comprising: control means for setting the condition of cut-off of the circuit breaker on the basis of the data stored in the data storing means. The multiplexing apparatus according to any one of the previous claims 2 to 5, wherein a C-shaped electric conductivity body (20), a portion of which is notched, an electric conductor (7) connected to the electric conductivity body (20) for detecting an electric potential, and a pull-up resistor are used to apply an electric potential to said electric conductivity layer, and said electric conductivity body (20) is press-bonded to the electric conductor (7) from the outside of the electric conductivity layer (2) of the thin mesh wire. The multiplexing apparatus according to any one of the previous claims, further comprising: control means for changing an alarm level of the alarm means on the basis of the data stored in the data storing means. The multiplexing apparatus according to any one of the previous claims, further comprising a fail-safe means which allows the processing unit in charge of the group of the area where an abnormality occurred to notify the processing unit of another group of the occurrence of the abnormality when said wire harness becomes abnormal, cut away the abnormal area and leave the control to the processing unit of another group. The multiplexing apparatus according to any one of the previous claims, wherein said processing units include a terminal processing unit which performs only the processing at the associated group, and a control unit which performs all processing including the processing of the terminal processing units. The multiplexing apparatus according to claim 1, wherein there are provided a plurality of electric conductivity layers (14, 22) and insulating layers (13, 21) which are sandwiched alternatively. The multiplexing apparatus according to claim 10, further comprising: alarm means for raising an alarm to a driver, a power source circuit breaker for cutting off a current supplied from the battery unit, and control means for starting up said alarm means to raise an alarm and starting up said power source circuit breaker to cut-off the current from the battery unit when at least one of said electric conductivity layers (14, 22) is short-circuited to the ground.

Inventors: KONI MITSURU, SAITO HIROYUKI, KONI,MITSURU, SAITO,HIROYUKI
Applicants: HITACHI CAR ENG CO LTD, HITACHI LTD, HITACHI CAR ENGINEERING CO., LTD., HITACHI, LTD.
Application year: 1996
Main classification: B60R16
IPC codes: B60R16, B60R21