Abstract:
A gaseous fuel management system for an automotive vehicle includes at least one gas sensor for detecting the presence of gaseous fuel outside of the confines of the vehicle&#39;s fuel storage tank, fuel lines, and prime mover. In the event that fugitive gas is detected and the concentration exceeds a predetermined threshold, the fuel supply to the vehicle&#39;s prime mover will be shut off and, if so equipped, the vehicle may then be operated in a battery power mode for the convenience of the driver.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/490,307 filed Jul. 25, 2003 and U.S. Provisional Application No. 60/549,617 filed Mar. 3, 2004. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system for distributing and otherwise handling gaseous fuel provided to the prime mover of an automotive vehicle. 
     2. Disclosure Information 
     Vehicle designers are accelerating a trend toward the use of gaseous fuel in the ever increasing quest for improved fuel economy and lower emissions. Although offering several advantages, gaseous fuel presents an unique set of challenges to designers, including the sometimes difficult handling of fugitive emissions of gaseous fuel. For example unwanted releases of hydrogen are not readily detectable by smell or sight, and as a result, is desirable to use electronic detection means for monitoring fugitive hydrogen and to build into a vehicle a system providing appropriate measures to mitigate the effects of unwanted discharges of hydrogen or other gaseous fuels such as natural gas or liquefied petroleum gas. 
     U.S. Pat. No. 6,290,594, which is assigned to the assignee of the present invention, discloses a system for measuring fugitive hydrogen within a fuel cell equipped vehicle having fans for reducing the concentration of free hydrogen gas within the interior spaces of the vehicle. The &#39;594 patent does not, however, cut off the fuel supply from the gaseous fuel storage tank in the event that fugitive hydrogen is detected, nor does the system of the &#39;594 patent provide a loss of strategy mode allowing the driver of a hybrid vehicle equipped with both an internal combustion engine powered by hydrogen or another gaseous fuel, as well as a traction motor/generator, to operate with vehicle with the motor/generator for a limited period of time in the event that a concentration of fugitive hydrogen or other gaseous fuel detected within any one of various spaces within a vehicle warrants deactivation of the vehicle&#39;s prime mover. 
     SUMMARY OF THE INVENTION 
     A gaseous fuel management system for an automotive vehicle having a passenger cabin and a prime mover has a fuel system including a gaseous fuel storage tank and a fuel line for conveying gaseous fuel from the storage tank to the prime mover. The fuel line has at least one electronically controlled valve for controlling the flow of gaseous fuel in the fuel line. A fuel management controller operatively connected with the electronically controlled valve closes the valve in the event that a gas sensor which is installed within the vehicle detects the present of fugitive gaseous fuel outside of the confines of at least one of the gaseous fuel storage tank, or the fuel line, or the prime mover. According to the present invention, the prime mover may include an internal combustion engine, a fuel cell, an internal combustion engine coupled with a traction motor/generator, or other fuel-consuming prime movers known to those skilled in the art and suggested by this disclosure. 
     A fuel management system according to the present invention preferably further includes at least one atmospheric circulator operated by a fuel management controller in response to a gas detection signal from a gas sensor. The atmospheric circulator may include either a blower or a fan or other device for moving atmospheric air through a space in the vehicle so as to remove fugitive fuel gas from the space being ventilated. The passenger compartment of the vehicle may be ventilated by operatively connecting at least one window in the passenger cabin or passenger compartment to the fuel management controller such that the window, which may be a side window, or sunroof, or other movable closure panels, may be opened in the response to a gas detection signal from the gas sensor. In this respect, the term ‘glazing panel’ means either a vision unit, such as a window, or a translucent or opaque movable panel which may be used for ventilating the passenger compartment of a vehicle. 
     In the event that a prime mover according to the present invention includes an internal combustion engine, the fuel management controller will place and maintain one or more electronically controlled fuel valves in a closed position in the event that an appropriate gas detection signal is present from the gas sensor. Other actions may be taken in the event that a higher level gas detection signal is present. For example, the fuel management controller may prevent recharging in the traction battery, if the vehicle so equipped, or prevent refueling of the vehicle. Further, as noted above, in the event that the gas detection signal is present, the fuel management controller may close an electronically controlled fuel tank valve so as to disable the vehicle&#39;s engine, while at the same time permitting the vehicle to continue operating with a traction motor/generator. 
     According to a preferred embodiment of the present invention, it is contemplated that a plurality of gas detection sensors may be employed with a vehicle. Sensors may be positioned inside an enclosure within which the fuel storage tank is mounted, as well as within an engine compartment or prime mover compartment. Additional sensors may be located within the passenger cabin and also within an enclosure within which the traction battery is located. In a further preferred embodiment, at least one ventilation duct will be situated such that the first end of the duct is connected to an enclosure within which the fuel storage tank is mounted, with a second end of the duct being connected to an air extractor mounted to an external surface of an automobile, whereby any fugitive gaseous fuel entering the fuel tank enclosure from the fuel storage tank will be extracted from the enclosure by air flowing past the surface of the body when the vehicle is moving. This is a so-called passive type of device, as is the use of ventilation apertures formed in an upper portion of the prime mover compartment such that air will be allowed to flow through the prime mover compartment while removing fugitive fuel gas emissions. 
     According to another aspect of the present invention, a method of operating a gaseous fuel automotive vehicle having both a prime mover fueled by gaseous fuel, and a traction motor/generator, includes the steps of providing a passive ventilation system to mitigate any significant buildup of fugitive fuel gas within various spaces within the vehicle, and monitoring at least one interior space of the vehicle so as to determine the presence of fugitive fuel gas within the space, by means of at least one electronic sensor. The method also includes the provision of at least one atmospheric circulator, such as a fan or blower, for supplying ambient air to at least one space within the vehicle, while disabling operation of the prime mover and allowing operation of the traction motor/generator, so as to purge the interior space which the circulator services while allowing the driver limited operation using the traction motor and traction battery. 
     Additional steps according to the present inventive method include opening movable glazing in the passenger compartment of the vehicle, and closing a fuel supply valve located between a gaseous fuel tank and the prime mover. In the event that either the electronic gas sensor system becomes inoperative, or if a predetermined fugitive fuel gas concentration threshold is exceeded, the prime mover will be disabled by cutting off its fuel supply, while allowing operation of the traction motor/generator, and while simultaneously operating at least one atmospheric circulator so as to purge an interior space of the vehicle. 
     It is an advantage of the present invention that fugitive fuel gas emissions may be handled in a manner which maintains the fuel economy of the vehicle while at the same time, enhancing the vehicle&#39;s reliability. 
     It is an advantage of the present invention that the present gaseous fuel management system may be employed with hydrogen, or natural gas, or liquefied petroleum gas, and may be used in vehicles having as a prime mover either a fuel cell, or an engine-motor/generator combination, or solely an engine, or yet other types of fuel-consuming prime mover. 
     Other advantages, as well as objects and features of the present invention, will become apparent to the reader of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a vehicle having a fuel management system according to the present invention. 
         FIG. 2  is a perspective view of a chassis of the vehicle of  FIG. 1 , showing various components associated with the present system and method. 
         FIG. 3  is a plan view of the vehicle of  FIGS. 1 and 2 . 
         FIG. 4  is a system block diagram showing various components of a gaseous fuel management system according to the present invention. 
         FIG. 5  is a flow chart showing a portion of operation of a gaseous fuel management system according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIG. 1 , vehicle  10  has several movable glazing units such as side window  52  and moon roof  46 . Vehicle  10  also has a series of vents  44  formed in the trailing edge of engine compartment hood  42 . Finally, vehicle  10  has NACA scoop  56  formed on the driver&#39;s (left) side quarter panel and an accompanying NACA scoop formed on the passenger side (right) quarter panel. When vehicle  10  is in motion, air is drawn from the interior of vehicle  10  by the aerodynamic action of the NACA scoops. This feature provides a portion of a passive ventilation system, as does the ventilation provided by vents  44 . As shown in  FIG. 2 , the chassis of vehicle  10  has fuel tank  12 , which is a compressed and/or liquefied gas fuel tank suitable for any one of natural gas, hydrogen, liquefied petroleum gas, or other compressed and/or liquefied fuel gases. As used herein, the term ‘gaseous fuel’ means either a fuel which is stored either in a single phase as a compressed gas or as a two-phase compressed gas and liquid. 
     Traction battery  14  is mounted adjacent gaseous fuel storage tank  12 , and gas or liquid from the fuel tank  12  and electrical energy from traction battery  14  move to the front of vehicle  10  where prime mover  20  is situated. 
     Prime mover  20  may have an engine,  26 , with or without a traction motor/generator,  34 , coupled to a transmission  30 , as is shown in  FIG. 3 . Alternatively, prime mover  20  may include a fuel cell and an associated traction motor/generator, or an internal combustion engine without an associated traction motor/generator. 
     Gaseous fuels are generally buoyant in air, and the use of venting via moon roof  46  and engine compartment vents  44  will take advantage of this natural buoyancy. These are passive ventilation devices, as are the use of NACA scoops to pull air through fuel tank enclosure vent ducts  88  ( FIG. 3 ). Ducts  88  have an inboard connection with fuel tank enclosure  18  and an outboard connection with one of the previously described NACA ducts. Gas sensor  22   b , which is located within fuel tank enclosure  18 , detects the presence of gaseous fuel, in this case hydrogen, outside the confines of storage tank  12 . As fully described below, fuel tank enclosure vent fans  84  are used to ventilate tank enclosure  18  in the event that an undesirable level of gaseous fuel is detected by means of sensor  22   b . Those skilled in the art will appreciate in view of this disclosure that gas sensing and active and passive ventilation devices may be used as described herein, with appropriate adjustments for the lack of buoyancy. 
     Battery  14  is located within battery enclosure  32 , which is ventilated by means of battery compartment fans  80  which, as is the case with fuel tank enclosure vent fans  88 , will be activated in the event that a concentration of fugitive fuel gas exceeding a threshold value is detected by means of sensor  22   c . Climate control fan  66  is mounted within passenger compartment  68  and is energized in the event that sensor  22   a  senses fugitive gas within the passenger compartment. Similarly, radiator fan  64 , which services engine cooling radiator  62  is turned on in the event that sensor  22   d  senses fugitive gaseous fuel within engine compartment  40 . 
     Fuse and relay box  72 , which contain high voltage relays for operating traction motor/generator  34 , is equipped with ventilation fan  74  which will be turned on as described below. 
     As shown in  FIG. 4 , vehicle  10  further includes driver information display  36  which is operated by fuel management control  24 . Driver display  36  includes a two-color lamp visible from both inside and outside vehicle  10 . If the lamp is green, this means that no fault has been detected within the fuel handling system. If the lamp is red, this means that either fugitive gas has been detected at a concentration above a threshold concentration, or that one or more of sensors  22  is out of specification. Driver information display  36  further includes an audible warning device which is activated if a higher level of fugitive gas is detected. 
     As shown in  FIG. 4 , fuel management controller  24  operates movable glazing  46  and  52 , as well as air circulators  28 , which include various air circulators for tank enclosure  18 , battery enclosure  32 , passenger compartment HVAC fan  66 , and engine compartment cooling fan/radiator cooling fan  64 . Fuel management controller  24  receives signals from gas sensors  22   a - 22   d  and is operatively connected with vehicle system controller  38 , which has supervisory functional control over engine  26  and traction motor/generator  34 . Fuel management controller  24  also operates the fuel valves  58   a - 58   c.    
     As shown in  FIG. 5 , a method according with the present invention starts at block  100 . At block  102 , fuel management controller  24  operates gas sensors  22   a - d  to sample interior spaces within vehicle  10 . The inventors of the present invention have determined that silicon micromachined gas sensors produced by Makel Engineering of Chico, Calif., and having the model designation 02HDS021 are useful for practicing this invention. 
     At block  104 , the measured concentrations of fugitive fuel gas, if any, are matched with a lower concentration threshold, CG 1 . In the event that the fugitive gas concentration is less than CG 1 , the routine continues sampling at block  102 . If however, the concentration exceeds CG 1  at block  104 , the routine moves to block  106  wherein a lower level mitigation routine is run. 
     The lower level mitigation routine at block  106  includes opening movable glazing such as moon roof  46  or side windows  52 , discontinuing high voltage charging of traction battery  14 , and alerting the driver that fugitive fuel has been detected. Also, fuel tank enclosure fans  84  and battery enclosure fans  80  will be turned on. If a leak is detected in the passenger cabin, climate control fan  66  will be operated. If fugitive fuel gas is detected in the engine compartment, engine cooling fan  64  will be operated, and climate control fan  66  will be disabled. Also, vehicle refueling will be prevented. 
     After the lower level mitigation routine has began at block  106 , the routine moves to block  108  wherein the measured gas concentration from sensors  22   a - d  is compared with a upper threshold CG 2 . If the gas concentration is not greater than CG 2 , the lower level mitigation routine will continue, until the concentration of gas drops below threshold CG 1 . If at block  108 , the gas concentration exceeds CG 2 , the routine moves to block  110  wherein the prime mover  20  will be disabled by cutting off fuel by means of fuel cut-off valves  58   a, b  and  c . This will serve to mitigate any fuel system integrity problem existing in fuel line  16  which conveys either gas or liquid between fuel tank  12  and prime mover  20 , as well as any fuel handling problem located within the prime mover. 
     Having disabled the prime mover at block  110 , fuel management controller  24  moves to block  112 , where a higher level mitigation routine is run. This high level routine includes such steps as making certain that fuel tank solenoid valves  58   a, b  and  c  are closed under all conditions, and also includes maintaining the operation of vent fans  80  and  84 . Once fuel solenoid valves  58   a - c  are closed, they cannot be reopened until a manual reset is accomplished by the vehicle&#39;s operator. 
     As noted at block  110 , when prime mover  28  is disabled, engine  26  will not receive any fuel, and as a result, a limited operating strategy or limp-home mode will be started with traction motor/generator  34 , which will allow the vehicle to be driven with only electrodrive capability for a limited period of time, as a convenience for the driver. At block  114 , the routine of  FIG. 5  continues with the running of the higher level mitigation routine until the concentration of fugitive gas is below CG 2 . If the measured concentration of fuel gas is below CG 2  at block  112 , the routine moves to block  104  and continues with a comparison of the measured gas concentration with CG1 1 . The method of  FIG. 5  preferably runs whenever vehicle  10  has fuel on board. 
     Although the present invention has been described in connection with particular embodiments thereof, it is to be understood that various modifications, alterations, and adaptations may be made by those skilled in the art without departing from the spirit and scope of the invention set forth in the following claims.