Abstract:
A particle filter for a fuel cell coolant is disclosed. The particle filter includes a filter housing having an upstream end for receiving the coolant and a downstream end for discharging the coolant. A filter element is provided in the filter housing. A pressure gauge is operably connected to the upstream end of the filter housing for measuring and indicating a pressure of the coolant corresponding to a degree of blockage of the filter element.

Description:
FIELD OF THE INVENTION 
   The present invention relates to fuel cell systems which utilize hydrogen to produce electricity for the powering of a vehicle or other electrical system. More particularly, the present invention relates to a particle filter for filtering particles from a fuel cell coolant to prevent or minimize the plugging of coolant flow channels in a fuel cell stack. 
   BACKGROUND OF THE INVENTION 
   In recent years, much research has been devoted to the development of fuel cells as a source of energy for vehicles. In a fuel cell vehicle, a fuel cell stack uses hydrogen gas to produce electricity which powers an electric motor that propels the vehicle. Fuel cell vehicles are environmentally-friendly since they emit only water and heat as by-products. 
   Fuel cells are provided with a cooling system to dissipate excessive heat from the fuel cell. A fuel cell cooling system typically includes a pump which circulates a liquid coolant through channels in the fuel cell. In a hydrogen fuel cell vehicle, coolant channels in a fuel cell stack are very small in size. When liquid coolant passes through the fuel cell vehicle cooling system, particles may be abstracted from the various plastic, metal and rubber components of the system into the coolant. The coolant carries these particles into the coolant channels of the fuel cell stack. Consequently, the particles have a tendency to block the coolant channels, thereby impeding coolant flow in the fuel cell and causing individual fuel cells in the fuel cell stack to excessively heat up and fail. 
   Accordingly, a device is needed to filter particles from coolant in a fuel cell and detect the quantity of particles removed from the coolant by the filter by measuring a rise in coolant pressure upstream of the filter. The quantity of particles removed from the filter would be directly correlated with the need to replace the filter in order to maintain optimum filter performance. 
   SUMMARY OF THE INVENTION 
   The present invention is generally directed to a particle filter for fuel cell coolant. The particle filter includes a filter housing within which is provided a filter element. As coolant flows through the filter housing, the filter element removes particles from the coolant prior to distribution of the coolant through a fuel cell. A pressure gauge includes a pressure sensor provided upstream of the filter housing to measure the pressure of coolant flowing into the filter housing. A pressure indicator is connected to the pressure sensor. The pressure indicator is calibrated and appropriately marked to indicate the degree to which the filter is clogged with particles according to the magnitude of the upstream filter pressure as measured by the pressure sensor. The pressure indicator includes a marking which indicates an upstream filter pressure that corresponds to a need for servicing the filter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a cross-sectional view, partially schematic, of an illustrative embodiment of a particle filter for a fuel cell coolant according to the present invention; and 
       FIG. 2  is a bottom view of a fuel cell vehicle, illustrating typical placement of the particle filter for a fuel cell coolant in the vehicle to facilitate ease in installation and removal. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention contemplates a fuel cell coolant particle filter which removes particles from a fuel cell coolant prior to distribution of the coolant through a fuel cell cooling system. While the fuel cell coolant particle filter is particularly well suited to filtering particles from coolant in a vehicle fuel cell cooling system, it will be recognized that the filter can be adapted to remove particles from a coolant in a fuel cell system which is used to power any type of electrical system. 
   Referring to  FIG. 1 , an illustrative embodiment of the fuel cell coolant vehicle filter, hereinafter “filter”, of the present invention is generally indicated by reference numeral  10 . The filter  10  includes a generally elongated, typically cylindrical filter housing  12  which may be metal or plastic, in non-exclusive particular. Preferably, the filter housing  12  is polyvinylidene fluoride (PVDF). The filter housing  12  has a housing interior  14 . A housing inlet  16  communicates with the housing interior  14  at one end of the filter housing  12 , and a housing outlet  18  communicates with the housing interior  14  at the opposite end of the filter housing  12 . 
   A filter element  20  is provided in the housing interior  14 , between the housing inlet  16  and housing outlet  18 , and separates the housing interior  14  into a pre-filtered region  22  and a filtered region  24 . The filter element  20  may have a generally conical or frustro-conical configuration, as shown, in which case the mouth  20   a  of the filter element  20  is typically located adjacent to the housing inlet  16  and the apex  20   b  of the filter element  20  is typically located adjacent to the housing outlet  18 . The filter element  20  may be metal, plastic or any other material which is compatible with a fuel cell coolant, which is typically a mixture of 40% by volume ethylene glycol and 60% by volume deionized water. Preferably, the filter element  20  is a 316 stainless steel mesh and is rated for filtering particles at or above the size of 40 microns. 
   A filter inlet conduit  26  is provided in fluid communication with the housing inlet  16  for distributing a flowing liquid fuel cell coolant  62  into the filter housing  12 , as will be hereinafter described. A filter outlet conduit  30  is provided in fluid communication with the housing outlet  18  for distributing the coolant  62  from the filter housing  12 . A reverse flow conduit  28  is provided in fluid communication with the filter inlet conduit  26  and extends in generally perpendicular relationship thereto. A coolant reservoir (not shown) may be provided in fluid communication with the reverse flow conduit  28  to receive reverse flowing coolant  62   a  flowing from the filter inlet conduit  26  into the reverse flow conduit  28 , as will be hereinafter further described. 
   Upon partial or complete blockage of the filter element  20  due to prolonged usage of the filter  10 , as will be hereinafter described, reverse flowing coolant  62   a  flows from the filter inlet conduit  26 , into the reverse flow conduit  28 . The pressure of the reverse flowing coolant  62   a  is directly proportional to the degree of blockage of the filter element  20 . A pressure gauge  32  is connected to the fuel cell coolant filter  10  to measure and indicate the pressure of reverse flowing coolant  62   a  in the reverse flow conduit  28  responsive to particle blockage of the filter element  20 , as will be hereinafter described. The pressure gauge  32  includes a pressure indicator  38  which is operably connected to the interior of the reverse flow conduit  28  to measure and indicate the pressure of reverse flowing coolant  62   a  in the reverse flow conduit  28 . The pressure indicator  38  may include various indicator regions such as, for example, a first indicator region  40   a  which corresponds to from 0% to 25% blockage of the filter element  20 ; a second indicator region  40   b  which corresponds to from 25% to 50% blockage of the filter element  20 ; a third indicator region  40   c  which corresponds to from 50% to 75% blockage of the filter element  20 ; and a fourth indicator region  40   d  which corresponds to 75% to 100% blockage of the filter element  20 . 
   The pressure indicator  38  may be a conventional pressure-sensing plate, membrane, diaphragm or coil, for example, which is capable of sensing the pressure of reverse flowing coolant  62   a  in the reverse flow conduit  28 . The various indicator regions  40   a - 40   d  may normally be a uniform background color such as white, for example, and change to a selected color upon activation depending on the pressure of the reverse coolant  62   a  in the reverse flow conduit  28 . For example, the first indicator region  40   a  may change from the uniform background color, such as white, to green when the filter element  20  is unblocked or the pressure of the reverse flowing coolant  62   a  corresponds to up to a 25% blockage of the filter element  20 . Accordingly, the first indicator region  40   a  is calibrated to change from the uniform background color to green when the pressure indicator  38  senses a pressure of the reverse flowing coolant  62   a  which results due to a 25% or less blockage of the filter element  20 . In similar fashion, the second indicator region  40   b  may be calibrated to change from the uniform background color to yellow when the pressure indicator  38  senses a pressure of the reverse flowing coolant  62   a  corresponding to a 25% to 50% blockage of the filter element  20 . The third indicator region  40   c  typically changes from the background color to orange when the coolant pressure corresponds to a 50% to 75% blockage of the filter element  20 , and the fourth indicator region  40   d  typically changes from the background color to red when the coolant pressure corresponds to a 75% to 100% blockage of the filter element  20 . 
   It will be understood that alternative pressure gauges known by those skilled in the art may be used to sense and indicate the pressure of the reverse flowing coolant  62   a  in the reverse flow conduit  28 . For example, the pressure indicator  38  may be provided with an indicator needle (not shown) which moves from left to right responsive to and in proportion to the magnitude of the pressure of the reverse flowing coolant  62   a  in the reverse flow conduit  28 . In that case, the indicator needle would indicate the first indicator region  40   a  when the filter element  20  is up to 25% blocked; the second indicator region  40   b  when the filter element  20  is 25% to 50% blocked; the third indicator region  40   c  when the filter element  20  is 50% to 75% blocked; and the fourth indicator region  40   d  when the filter element  20  is 75% to 100% blocked. 
     FIG. 2  illustrates a typical installation position of the fuel cell coolant filter  10  in a fuel cell vehicle  50 , a bottom view of which is shown. The fuel cell vehicle  50  includes a front end  52 , a rear end  54 , a pair of front wheels  56  and a pair of rear wheels  58 . Preferably, the filter  10  is mounted in a horizontal position between the front wheels  56  and rear wheels  58  and is accessible from the bottom  60  of the fuel cell vehicle  50 . An inlet  64   a  of the vehicle coolant system  64  (shown in phantom) is connected to the filter outlet conduit  30  of the filter  10 , and an outlet  64   b  of the vehicle coolant system  64  is connected to the filter inlet conduit  26  of the filter  10 . Accordingly, the filter  10  is easily accessible on the fuel cell vehicle  50  for servicing, repair or replacement, as needed. The pressure indicator  38  of the pressure gauge  32  is typically provided on the dashboard (not shown) of the fuel cell vehicle  50  or in some other location which is visible to the driver of the fuel cell vehicle  50 . 
   Referring again to  FIGS. 1 and 2 , in typical operation of the filter  10 , coolant  62  flows throughout the vehicle coolant system  64  ( FIG. 2 ) to cool the fuel cell (not shown) of the fuel cell vehicle  50 , typically in conventional fashion. The expended coolant  62  flows from the vehicle coolant system  64 , through the outlet  64   b  and into the filter inlet conduit  26  of the filter  10 , respectively. When the filter element  20  of the filter  10  is unblocked, the coolant  62  flows unimpeded from the filter inlet conduit  26 , through the housing inlet  16  and into the housing interior  14  of the filter housing  12 ; through the filter element  20 ; and into the filter outlet conduit  30  through the housing outlet  18 , respectively. 
   As the coolant  62  flows through the filter element  20 , particles (not shown) having a size of typically about 40 microns and larger are removed from the coolant  62  and become entrapped in the filter element  20 . Therefore, the coolant  62  which emerges from the filter  10  and is distributed back to the vehicle coolant system  64  through the inlet  64   a  is substantially devoid of particles which would otherwise tend to clog coolant channels in the fuel cell (not shown). From about 95 to 98 percent of contaminant particles are typically removed from the coolant  62  within the first passage of coolant  62  through the filter  10 . 
   When the filter element  20  is substantially unclogged by particles, the coolant  62  tends to flow unimpeded and uni-directionally from the filter inlet conduit  26  and into and through the filter housing  12 . Therefore, substantially none of the coolant flows from the filter housing  12  back into the filter inlet conduit  26  and reverse flow conduit  28  as reverse flowing coolant  62   a . Accordingly, the pressure gauge  32  measures a coolant pressure of “0” in the reverse flow conduit  28 . This coolant pressure is correlated with 0% clogging of the filter element  20 . The pressure indicator  38  indicates this unclogged condition of the filter element  20  by imparting the “activation” color (green, in this case) to the first indicator region  40   a , while the remaining indicator regions  40   b - 40   d  remain in the uniform background color. Accordingly, the pressure indicator  38  is interpreted as indicating either an unclogged condition or a clogged condition of the filter element  20  which ranges from 1% to 25%. 
   As the filter element  20  becomes progressively clogged by particles throughout prolonged use, some of the coolant begins to flow from the filter housing  12  and back into the filter inlet conduit  26  as reverse flowing coolant  62   a  as the forward-flowing coolant  62  impinges against the blocked regions of the filter element  20 . Some of this reverse flowing coolant  62   a  flows into the reverse flow conduit  28 . The pressure gauge  32  measures the pressure of the reverse flowing coolant  62   a  in the reverse flow conduit  28 , and the pressure indicator  38  indicates the measured pressure as a direct measure of the degree of blockage of the filter element  20 . 
   In the event that the pressure of the reverse flowing coolant  62   a  corresponds to a blockage of from 1% to 25% of the filter element  20 , the first indicator region  40   a  of the pressure indicator  38  displays the “activation” color (green in this case). In the event that the pressure of the reverse flowing coolant  62   a  in the reverse flow conduit  28  corresponds to a blockage of from 25% to 50% of the filter element  20 , the color of the second indicator region  40   b  changes from the background color to the “activation” color (yellow in this case). In the event that the pressure of the reverse flowing coolant  62   a  in the reverse flow conduit  28  corresponds to a blockage of from 50% to 75% of the filter element  20 , the color of the third indicator region  40   c  changes from the background color to the “activation” color (orange in this case). In the event that the pressure of the reverse flowing coolant  62   a  in the reverse flow conduit  28  corresponds to a blockage of from 75% to 100% of the filter element  20 , the color of the fourth indicator region  40   d  changes from the background color to the “activation” color (red in this case). At that point, activation of the fourth indicator region  40   d  indicates to a driver (not shown) of the fuel cell vehicle  50  that the fuel cell coolant filter  10  needs to be removed from the vehicle  50  and serviced or replaced. 
   The filter  10  is preferably constructed in such a manner that it can survive coolant pressures of up to 75 psi without leakage or loss of functionality. The construction of the filter  10  facilitates operation at temperatures of 85 degrees C. without loss of structural integrity. The filter  10  is capable of operation without service for a minimum of one year or 15,000 miles. Preferred operating ranges for the filter  10  include a humidity of between 0% and 100%, an elevation of between −150 meters and 4,570 meters above sea level and a maximum pressure drop of 0.9 psi at 4,500 pump rpm and flow of 25.5 gpm. 
   While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.