Abstract:
The system provides for controlling the connection of electrical power sources to electrical loads installed on a motor vehicle and limiting exposure of personnel to relatively high electrical voltages from the electrical power sources. The system includes a serial communication bus and power cables routed through the motor vehicle. At least a first connector is provided through which the serial communication bus and a power cable are routed allowing temporary severing of the serial communication bus and the power cable. The power cable includes a circuit interrupter which isolates the connector from the electrical power source in response to certain conditions on the serial communication bus, including, but not limited to, the cessation of data traffic on the serial communication bus.

Description:
BACKGROUND 
     1. Technical Field 
     The technical field relates generally to interlocks for isolating electrical power sources and more particularly to their application to power cables and cable connectors on motor vehicles. 
     2. Description of the Problem 
     Hybrid-electric and electric vehicles provide storage of electrical power in batteries or on capacitors. Such batteries and capacitors have terminal to terminal voltage differentials which are greater by more than an order of magnitude than chassis batteries used on most contemporary trucks and cars. Cables connected to the batteries can exhibit these relatively high potentials on terminal plugs at points of connection to the vehicle electrical system. 
     In applications where personnel are potentially exposed to high voltages, interlock circuits have been used to isolate the high voltage source when connectors are opened and could potentially expose terminals which could carry high voltages. U.S. Pat. No. 5,949,806 (Ness et al.) teaches one such High Voltage Interlock Circuit. In addition, connectors used in high voltage application have been modified to support addition of an interlock circuit which is interrupted if the connector sections are not securely fastened. For motor vehicles such connectors are commonly provided in four and five wire versions. In a four wire cable, two wires are used for the high voltage circuit and two wires are used for the voltage interlock circuit. In a five wire connector, three wires are used for high voltage and two for the interlock circuit. Both types of connectors provide shielding. 
     SUMMARY 
     The system provides for controlling the connection of electrical power sources to electrical loads installed on a motor vehicle through interlocks and limiting exposure of personnel to relatively high electrical voltages thereby. The system includes a high voltage distribution system including power cables routed through the motor vehicle and at least a first serial communication bus routed for some part of its length physically proximate to the power cables. Interlock activation functions may be carried out using the serial communication bus in place of a dedicated interlock circuit. At least a first connector is provided through which the serial communication bus and a power cable are routed allowing temporary severing of the serial communication bus and the power cable. A power cable interrupter is located in the power cable to allow electrical isolation of the proximate side of the connector from an electrical power source. A signal interpreter is coupled to the serial communication bus. The signal interpreter is responsive to changes in communication traffic or bus impedance indicating opening of the connector. Responsive to the status of the traffic or bus impedance, the signal interpreter controls the state of the power cable interrupter. In addition, a specific instruction for generating command signals for controlling the state of the power cable interrupter may be applied to the serial communication bus or to a another serial communication bus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a high level schematic of a control system for a hybrid-electric vehicle. 
         FIG. 2  is a more detailed schematic of an interlock circuit for power cabling on a hybrid-electric vehicle. 
         FIG. 3  is a circuit schematic of a mixed source interlock circuit for power cabling on a hybrid-electric vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description example, sizes/models/values/ranges may be given with respect to specific embodiments but are not to be considered generally limiting. 
     Referring now to the figures and in particular to  FIG. 1 , a high level schematic of a control system  10  which provides control over a drive train and a high voltage power distribution system  12  of a hybrid electric vehicle is illustrated. The control system  10  includes several serial communication buses  18 ,  64 ,  68 ,  74  which provide data links among an assortment of controllers and vehicle switches, including a logic/electrical system controller  24 , a type of a body computer, which operates as a system supervisor. The serial communication bus  74  is shared by and runs between high voltage components of the control system  10  and thus is available for use in circuit integrity monitoring of the high voltage power distribution system  12 . 
     Logic controller  24  is linked by a Society of Automotive Engineers (SAE) J1939 serial communication bus  18  to a variety of local controllers including an anti-lock brake system (ABS) controller  50 , an engine controller  46  and a hybrid controller  48 . Hybrid controller  48  is also connected to a serial communication bus  74  (HEV CAN), portions of which are located in close physical proximity to the high voltage power distribution system  12 . Hybrid controller  48  and engine controller  46  can also communicate over a fourth communication bus  68  (an SAE J1587 bus). A diagnostic connector  44  is connected to serial communication bus  18  and to communication bus  68 . Communications bus  64  allows logic controller  24  to interrogate switch states of in-cab switch packs  56 . The controllers connected to serial communication bus  74  include a traction motor controller  38 , a battery monitor  40 , an auxiliary power (APG) controller  30 , a clutch/transmission controller  42  and the hybrid controller  48 . 
     The high voltage power distribution system  12  includes a traction battery  34 , a high voltage direct current power bus  82 , a circuit interrupter  76 , a hybrid inverter  36 , a three phase power bus  84 , a three phase circuit interrupter  78  and a traction motor  32 . Connectors, as described below, may be used in combination with either the high voltage direct current power bus  82  or the three phase power bus  84  and serial communication bus  74 . The high voltage power distribution system  12  is accessible for inspection, maintenance and potentially removal of components, including the traction batteries  34 . 
     Depending upon the operational mode of the vehicle power flow may occur in either direction through hybrid inverter  36 , from traction motor  32  to traction battery  34  or from traction battery  34  to traction motor  32 . In other words, traction battery  34  may be a load or a source of power. Similarly, traction motor  32  may be a load when driven during acceleration, or a source of power when backdriven during regenerative braking of the vehicle. The hybrid inverter  36  can appear to a source or a load from the perspective of either the traction motor  32  or the traction battery  34 . 
     Because traction batteries  34  and traction motor  32  can change roles as to which is a source and which a load, depending upon the operational mode of the vehicle,  FIG. 2  refers to generic electrical “sources  66 ” and “loads  70 ”. Removal of generic electrical sources  66  and generic electrical loads  70  is eased by providing electrical connection to the components represented by use of plug connectors  14 A and  14 B in the power conductors. Plug connectors  14 A and  14 B may be opened and closed by hand. The potential exposure of personnel to voltages of 300 volts or greater which may be sourced from traction battery  34  are limited by interrupting the power cables between the electrical source  66  and the connector  14 A before the connectors  14 A and B are fully separated. 
     Either high voltage DC power bus  82  or three phase power bus  84  may be interrupted to isolate connectors  14 A, B from an electrical power source  66 .  FIG. 2  illustrates provision of an interlock relay  16  to control the open and closed states of a DC circuit interrupter  76  located in the high voltage direct current power bus  82 . Circuit interrupter is located between the ungrounded terminal of the generic electrical source  66  (typically corresponding to traction battery  34 ) and the generic electrical load  70  (here corresponding to hybrid inverter  36 ). The interlock relay  16  can also be used to control the open and closed states of a three phase circuit interrupter  78  located in the three phase power bus  84  connecting the three phase AC terminals of the hybrid inverter  36  to the traction motor  32 . Circuit interrupter  76  or three phase circuit interrupter  78  may be realized in various ways, for example as power MOSFETs, open collector NPN transistors, vacuum triodes, solenoid activated relays, etc. 
     Interlock relay  16  operates in response to a signal generated in response to an absence of data traffic on serial communication bus  74 , or, possibly, to absence of detection of a bus terminating impedance upon application of impedance detection signal. Data traffic on serial communication bus  74  ceases, and one of the bus terminating impedances would be cut off, upon separation of connectors  14 A and  14 B through which serial communication bus  74  is connected. A signal interpreter is provided for generation of the signal to be applied to the interlock relay  16 . The signal interpreter may take a number of different forms. For example, the signal interpreter may be a serial communication bus traffic detector  20 . The signal interpreter may add a bus node, including a CAN communication interface, for receiving instructions over a second serial communication bus. In this case a microprocessor is added and programmed to decode commands which control operation of the interlock relay  16  and thereby the state of the circuit interrupter  76  or three phase circuit interrupter  78 . Such a response is software based and thus could operate in response to the status of various sensors around a vehicle, such as opening of an access panel in the area of the electrical power source or detection of an accident (e.g. air bag deployment). 
     Serial Communication bus traffic detector  20  is implemented as hardware. A pair of sense wires  80  are provided for connection to each wire in serial communication bus  74 . If serial communication bus  74  is active, that is carrying data traffic, it will undergo regular voltage transitions. For a J1939 CAN serial communication bus the voltage transitions are typically between negative 50 millivolts and positive 2.5 volts. 
     Serial communication bus traffic detector  20  is responsive to voltage differentials associated with data traffic appearing between the wires of serial communication bus  74  for generating a signal which, applied to interlock relay  16 , results in generation of a signal by the interlock relay which keeps circuit interrupter  76  closed. A lack of data traffic on the serial communication bus  74  results in a change in state of the signal from interlock relay  16  opening the circuit interrupter  76 . Absence of data must persist past a minimum time threshold for a no traffic status to be indicated. 
     Serial communication bus  74  is routed in close proximity to high voltage cables of the high voltage power distribution system  12  and is routed through the interlock circuit conductors of a conventional four wire connectors  14 A and  14 B displacing a conventional interlock circuit, or a five wire connector if used for the three phase power bus  84 . 
     In addition to monitoring for interruption of the serial communication bus  74 , the circuit interrupters  76 ,  78  may be opened in response to a command to do so over another serial communication bus, for example serial communication bus  18 .  FIG. 3  illustrates addition of monitoring for logical control signal to data traffic monitoring. Serial communication bus  74  is connected, as before, by a pair of sense wires  80  to serial communication bus traffic detector  20 , which provides a signal to an input terminal of an AND gate  90 . To detect and decode a logical control signal a CAN interface  86  is coupled to a second serial communication bus  18 , which carries auxiliary signals directing opening or closing of the interlock relay  16  for transmission over the serial communication bus  74 . A microprocessor  88  is connected to the CAN interface  86  which identifies control signals intended for the node and operates on the signals to generate a two state signal for application to a second input terminal of AND gate  90 . Thus there must both be traffic on the serial communication bus  74  and the current control value received over serial communication bus  18  must indicate that the circuit interrupters  76  or  78  are to remain closed for the circuit interrupters to remain closed. The command signal to command connection of the high voltage bus is broadcast to the microprocessor  88  on a regular interval, and if the command signal ceases to be received, then the microprocessor  88  issues a decoded command to the AND gate  90  and subsequent logic gate output amplifier  92  to interrupt the high voltage bus by interlock relay  16 . The output of the AND gate  90  may be routed through the logic gate output amplifier amplifier  92  before application to the interlock relay  16 .