Abstract:
A High Voltage Interlock Loop (HVIL) system and Control Strategy is provided for an alternative fuel vehicle including an electric, a hybrid electric, or a fuel cell vehicle. Generally, the HVIL system having associated logic including an HVIL circuit is provided to allow the vehicle to operate in either a high voltage (HV) or power mode powered by a power source or a HVIL interrupt mode based on an operational state of the HVIL system. When HVIL circuit fails shorted high, low or open, a Diagnostic Trouble Code (DTC) is set and the Service Soon Lamp is illuminated to indicate to a service technician that additional safety precautions need to be taken when servicing the HV system. The HV contactors may or may not be activated providing HV to the vehicle when HV is not expected to be present at connectors and HV devices.

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to a high-voltage interlock and relates more specifically to a high-voltage interlock having a monitoring system. 
   BACKGROUND OF THE INVENTION 
   Modern vehicles often include many high-voltage electrical devices. High voltage devices may present challenges not present in conventional lower voltage systems. In the event of a vehicle accident or vehicle component failure, a short-circuited high voltage system may sustain heavy damage because of the relatively high voltage levels. Another concern is undesired contact with high voltage levels, either directly or indirectly, by a vehicle user or other persons. 
   Existing high voltage interlocks do provide a degree of safety for users anticipating contact with a high voltage electrical system, such as maintenance personnel, but may not provide protection in situations where a user inadvertently contacts a high voltage electrical system. 
   While existing devices suit their intended purposes, what is needed is a system that allows monitoring the High Voltage Interlock Loop (HVIL) with respect to wiring failures. This allows alerting the service personnel of a wiring failure system that needs additional precautions prior to servicing the high voltage system. 
   SUMMARY 
   A High Voltage Interlock Loop (HVIL) system and Control Strategy is provided for an alternative fuel vehicle such as an electric, a hybrid electric, or a fuel cell vehicle. Generally, the HVIL system having associated logic including an HVIL circuit is provided to allow the vehicle to operate in either a high voltage (HV) or power mode powered by a power source or a HVIL interrupt mode based on an operational state of the HVIL system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects, features and advantages of the present invention will become apparent from the following detailed description and the appended drawings in which: 
       FIG. 1  illustrates a HVIL monitor and control strategy in accordance with one embodiment of the invention. 
       FIG. 2  illustrates a table illustrating monitoring strategies in accordance with one embodiment of the invention. 
       FIG. 3  illustrates a HVIL control strategy in accordance with one embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates an exemplary fuel cell vehicle and includes the HVIL control system  10  and strategy in accordance with one embodiment of the present invention. 
   The present invention can be used, however, with any hybrid electric systems without deviating from the scope of the present invention, including vehicles powered by internal combustion engines, series hybrid electric vehicles (SHEV), parallel hybrid electric vehicles (PHEV), and electric vehicles that use a high voltage power source in combination with a vehicle battery.  FIG. 1  illustrates an electrical diagram of the HVIL control system in accordance with one embodiment of the invention. 
   Exemplary fuel cell vehicle  10  includes electrically operated or controlled components including fuel cell  154 , transmission  16 , and vehicle battery  220 . These components operate with a planetary gear set  24  in the transmission, a motor/generator  26 , an inverter  28  within the IPT  72 , that powers a differential axle  38  (at the output of the transmission) and the vehicle wheels  40 . The IPT  72  controls and monitors the torque output of engine  14  and motor/generator  26 . Fuel cell  154 , transmission  16 , and VSC  78  cooperate to form a system for the vehicle  10 , as is shown and discussed in further detail in  FIG. 1 . 
   Vehicle system controller  78  (VSC) controls all aspect of vehicle operation. VSC  78  monitors vehicle operation and controls vehicle  10 . VSC  78  generates and transmits signals to the vehicle components. The components operate as instructed by VSC  78 . VSC  78  may control each component independently and collectively to control vehicle operation. 
   In one embodiment of the invention, vehicle  10  includes HVIL monitor and control module microprocessor  86 . HVIL monitor and control module microprocessor  86  provides HVIL control logic through an inertia switch  192 , a plurality of HV accessory connectors  193 , and a HV contactors relay  194  to one or more HV contactors  182 ,  184 . 
   In the embodiment of the invention illustrated in  FIG. 1 , the HVIL control system  10  includes two HV contactors  182 ,  184 . In other embodiments of the invention, one or more HV contactors may be included. 
   In one embodiment of the invention, illustrated in  FIG. 1  the control module  86  and associated control logic may reside within the VSC  78 . 
   In one embodiment of the invention, the HVIL module  86  may be in operative communication with the VSC  78  but may reside in a separate location from the VSC  78 . 
   In an embodiment of the invention, VSC  78  includes an associated HVIL activation switch  80 , the HVIL activation switch  80  in signal communication with the VSC  78  and adapted to selectively couple or decouple a vehicle battery  220  from the VSC  78 . The high voltage interlock system logic is in electrical communication with a vehicle system controller (VSC) and may be integrally formed as a sub-module within the VSC. 
   Signals from a HVIL  212  source signal are input into the inertia switch  192 . The HVIL source  212  becomes the HVIL Out  214  continuing on to the power distribution box  206  and components associated therewith when an inertia switch  192  is closed or not triggered. The HVIL Out  214  is then input into the HV connectors  193  and becomes the HVIL sense signal  204  when monitoring for breaks in the HVIL source  212  and the HVIL sense signal  204 . The HVIL source  212  and HVIL sense signal  204  are the same signal when the inertia switch  192  is closed and when the HV connectors  193  are mated with the activated HV contactors relay  194 , and thus cooperate to form HVIL circuit  224  that provides vehicle battery  220  power to the HV contactors  182 ,  184 . VSC  78  can control operation of power sensed and distributed within the vehicle  10  based on the operation of the HVIL circuit. 
     FIG. 1  illustrates an exemplary fuel cell vehicle  10 . Fuel cell vehicles include components similar to those to be described below with respect to vehicles having internal combustion engines. 
   The fuel cell vehicle  10  illustrated in  FIG. 1  includes fuel cell  154  and a traction motor/generator  26 . Fuel cell  154  replaces a conventional engine, but it is similarly controlled by VSC  78 . The traction motor/generator  26 , powered by inverter  28  and gearing  24  is controlled by VSC  78 . Inverter  28  and motor/generator  26  operate on power provided from the high voltage bus  160 . High voltage bus  160  receives power from Fuel Cell  154 . DC/DC converter  162  receives power inputs from HV power bus  160 , and supplies 12V to the vehicle low voltage electrical system and recharges the 12V battery  220 . Fuel cell  154  further includes air conditioning compressor  68  and associated controller  70 , air module  66  and HV water pump  52 . 
     FIG. 1  illustrates a high voltage interlock control system  10  and strategy for use in a vehicle having a HVIL module  86  in accordance with one embodiment of the invention. 
   The HVIL control system  10  includes a VCS  78  in signal communication with a plurality of signal lines including a HVIL source line  212  output from the VCS  78  to an HVIL out line  214  when inertia switch  192  is closed and an inertia sense line  216  in further communication with an Energy Management Module (EMM)  23  when the inertia switch  192  is tripped, and a HVIL sense line  204  in further signal communication with a HV contactors controller relay  194 , power distribution box  206  (PDB), and using the CAN network protocol  218  is in further operative communication with an IPT interface  202 , a torque controller  222 , and other vehicle systems. 
   The VSC  78  provides a source for the HVIL circuit  224  and operates to control the HVIL system and monitor for nonconforming HVIL operating conditions. 
   In an embodiment of the invention, the HVIL circuit  224  is in further operative communication with an Energy Management Module  23  that monitors for high voltage battery readings, wherein for the HV power supply  154  to power the modules in signal communication with the PDB  206 , the HVIL sense line  204  input must be high and the inertia sense line  216  must be low. 
   In another embodiment of the invention, if the VSC  78  uses power from the vehicle battery  220 , the VSC  78  may not need to monitor the HVIL circuit  224  for HV battery readiness, and wherein the EMM  23  reads the inertia sense line  216  input. 
   The PDB  206  control communications between the VSC  78 , the IPT interface  202 , an auxiliary battery  220 , and a power supply  154  via a HV bus  160  in communication  218  with a plurality of modules including an air module  66 , an A/C compressor  68 , and a HV water pump  54 . 
   Operation of the HVIL  10  control system depends upon a HV contactors controller  194 , shown in  FIG. 1  as a relay operating as a switch, shown in  FIG. 1  as not activated, whereas the HV contactors  182 ,  184  are not triggered or opened, thereby suppressing power from the HV bus  160  to selected vehicle systems or components. As the HV contactors controller relay  194  is activated by the HVIL Sense  204  circuit, the HV contactors  182 ,  184  are closed in a normal vehicle operation mode, the HV power supply  154  then provides power to the selected vehicle components  54 ,  66 ,  68  as disclosed herein and as shown in  FIG. 1  when the HV contactors  182 ,  184  are triggered or closed. The HV contactors  182 ,  184  are normally open relays operating as single pole single throw switches as shown in  FIG. 1 . 
   The inertia switch  192  is provided in communication with the VCS  78  and the EMM  23 . The inertia switch  192  trips when an inertia event occurs, thereby forming a connection between the HVIL source line  212  and an inertia sense line  216 . The inertia switch  192  operates in an opposite switching state from the switching state of the HV controller  194 , when the inertia switch  192  trips, the inertia sense line  216  communicates a second digital input  164  into the EMM  23 , wherein the second digital input  164  has an associated second pull-down resistor  176  that is input into the EMM  23  and toggles between a high or a low/open state depending upon the operating mode of the HVIL circuit  224 , and in particular, the state of the inertia sense line  216 . 
   In the embodiment of the invention illustrated in  FIG. 1 , IPT  72  includes associated IPT microprocessor  202 , the IPT microprocessor  202  in signal communication with the VSC  78 . 
   A first digital input  160  has an associated pull-down resistor  170  input into the VSC  78  and EMM  23  and is connected to the HVIL sense line  204  that toggles between a high or a low/open state depending upon the operating mode of the HVIL circuit  224 , and in particular, the state of the HVIL inertia sense line  204 . 
   The HVIL circuit  224  powers the HV Contactors  182 ,  184  in accordance with commands received from the VSC  78 . 
   The HVIL circuit  224  includes the HVIL source line  212  that is enabled by the VSC  78  and that powers the HV contactors  182 ,  184  to close until an HV contactor open event occurs; an HVIL sense line  204  that is at the same potential as the HVIL source line  212  if the inertia sense switch  192  is not tripped, or closed if the HVIL sense circuit  204  is not broken; an inertia sense line  216  that is at the same potential as the HVIL source line  212  output from the VSC  78  if the inertia sense switch  192  is tripped or closed. The VSC  78  is in signal communication with a CAN system  218  for vehicle communications and provides a protocol check for the HVIL control system  10 . The HVIL circuit  224  includes the HVIL source line  212  as an output from the VSC  78  into a plurality of HVIL related modules including an air module  66 , an A/C compressor  68 , an associated A/C compressor controller  70 , and a HV water pump  52 ; and the HVIL sense line  204  as an output from the plurality of HVIL related modules into both the VSC  78  and an HV contactors controller relay  194 . 
   The HVIL out line  214  is at the same potential as the HVIL source line  212  if the inertia switch  192  is not tripped, however, the HVIL out line  214  is not monitored by the HVIL control system  10 . 
     FIG. 3  illustrates a flowchart of a HVIL control strategy and method  230  using the HVIL control system  10  to perform a plurality of options based upon a particular vehicle operation mode. 
   Initially, the HVIL source  212  is monitored by the VSC  78 , control module microprocessor  86  prior to activating the HVIL activation switch  80  ( 231 ), for a short to 12V ( 232 ). If the HVIL source  212  is low ( 233 ), then the HVIL Source is assumed not shorted high ( 234 ) and is ready for activation. If the HVIL source  212  is high ( 235 ), then the HVIL source  212  is assumed shorted and a DTC is set. The HVIL activation switch  80  is then activated ( 236 ) and the vehicle can be operated. 
   In an embodiment of the invention, the HVIL sense  204  is then monitored ( 237 ). If the HVIL sense line  204  input is low ( 239 ), then the HVIL source  212  and/or HVIL sense  204  is either open or shorted low, wherein a DTC is also set ( 240 ). If the HVIL sense line  204  input is high ( 238 ), the system is OK and no action is required ( 241 ). 
   In an embodiment of the invention, when the VSC  78  senses a low input from the HVIL sense line  204 , then one of four events has occurred, indicating an event selected from: an HVIL open circuit, a local open circuit, a tripped inertia switch, or a short to ground. 
   If an HVIL open circuit is detected, then the HV contactors  182 ,  184  are opened and thus, the HV bus  160  is suppressed from the fuel cell  154 . The VCS  78  confirms HV operational status from the CAN  218 . 
   If a local open circuit is detected, then the HV contactors  182 ,  184  could be open or closed and the potential of the HV bus  160  is high, exists. 
   The VCS  78  checks the HVIL circuit  224  operational status from the CAN  218 . Additionally, the status of other modules within the vehicle may be checked from the CAN including, but not limited to: HVIL sense line  204  and inertia sense line  216 . 
   In another embodiment of the invention, the EMM  23  reads inputs from the inertia switch  192 , and determines if the inertia switch  192  is tripped or closed. 
   In another embodiment of the invention, the VCS  78  determines if a short to ground in HVIL source line  212  of the HVIL circuit  224  exists when the vehicle is being driven. A fuse  48  associated with the HV contactors controller  194  may be blown if a short to ground exists and thus, the HV contactors  182 ,  184  will open, thereby decoupling the 12V battery  220  from the HVIL circuit  224 . 
   The HVIL sense signal  204  is a logic signal inputting either a high or a low input into the VCS  78  from the HVIL sense line  204  or indirectly from the HVIL circuit  224 , wherein the HVIL sense signal  204  provides control to the HV contactors relay  194  that provides power the HV contactors  182 ,  184 . The HV contacts  182 ,  184  will not be powered by the auxiliary battery  220  when the HVIL circuit  224  is broken. 
     FIG. 2  illustrates a logic table  300  indicating operating states of the vehicle and in particular the HVIL control system  10 . 
   A logic table shown in  FIG. 2  illustrates states of monitoring the HVIL Source  212  before and after the HVIL activation switch  80  is applied. This indicates whether the HVIL Source  212  is shorted to 12V. Upon activation of the HVIL activation switch  80 , the HVIL Sense  204  is monitored using the first digital input  160  associated with the HVIL sense line  204  input into the VSC  78 . The level of the HVIL Sense  204  with respect to the HVIL Source  212  indicates possible failure conditions to the HVIL circuit.