Patent Publication Number: US-2005121374-A1

Title: Device for bleeding the separated water from a fuel filter

Description:
TECHNICAL FIELD  
      This invention concerns the bleeding of the separated water from a fuel filter on vehicles with an internal combustion engine, in particular with a diesel engine.  
      The invention relates to vehicles comprising: 
          a fuel filter having a filtering means for filtering the fuel entering the filter and for separating the water present therein, and a collection chamber for the separated water,     a fuel tank having a capacity adequate for the extent of vehicle travel,     means for transferring fuel from that region of the filter lying downstream of the filtering means to the engine feed means,     means for feeding fuel from the tank to the filter inlet at a greater rate than the maximum flow rate transferred from the filter to the feed means.        

     BACKGROUND ART  
      The current trend among motor vehicle manufacturers is to equip the vehicle with fuel filters (for diesel oil in particular) having an increasingly longer life and greater filtering efficiency.  
      Modern diesel oil filters, in particular if installed on vehicles with diesel engine direct injection feed means of common rail or injector with pump type must ensure high filtering efficiency, a long life and a high degree of separation of the water present in the fuel.  
      The increased performance of such engines has resulted in ever more complex, mechanically precise and hence costly fuel feed systems; the relative mechanical components are therefore protected against wear and against corrosion by a fuel filter, which in particular separates the water which could otherwise result in damaging oxidation of the mechanical parts with which it comes into contact, and collects it in a suitable collection chamber.  
      In vehicles of more recent design, the diesel oil filter is of the type with an immersion cartridge housed in a container (of plastic material), the lower portion of which defines the collection chamber for the separated water.  
      The fuels currently supplied to the distributor network contain nominally about 0.02% of water but it is often possible, because of water infiltration into storage tanks or of condensation of moist air within the vehicle tank, for a considerable water quantity to be accumulated within the vehicle tank itself.  
      Common rail systems are provided with a pump immersed in the tank and operating at a rate of approximately 160 I/h; consequently in about 30 minutes all the liquid present in the tank is recirculated at least once through the system, to hence pass through the filter.  
      One of the modern characteristics of filter cartridges is their high power of separating water from the diesel oil (of the order of 99%), there hence being the risk that the filter rapidly accumulates such a water quantity as to exceed the containing capacity of the appropriate collecting chamber present in the filter. Exceeding the accumulation capacity of this chamber means that the filter cartridge operates immersed in water, hence obstructing the pores and in the long term completely filling the filter with water which is drawn towards the user device (high pressure pump). If this should happen the pump and the diesel oil injectors almost immediately seize, with prohibitively disastrous and costly consequences in terms of their renewal.  
      To avoid these dangers it is known to use a sensor for sensing the water level in the filter collection chamber, which however always presupposes timely direct manual intervention on the filter by the driver, who in reality is not always able to carry out the operations involved in bleeding the water from the filter, and often prefers to await the first available opportunity or the next ordinary service check on the vehicle.  
      An object of this invention is to prevent an excessive and dangerous water quantity being able to accumulate in the water collection chamber of the filter, without any intervention by the driver other than after such a distance as to require usual more general servicing, as defined by the normal vehicle servicing specification, with the advantage that the driver can leave water removal to the usual service station during normal vehicle servicing.  
     DISCLOSURE OF THE INVENTION  
      This and other objects are attained by the device of the invention as characterised in the claims.  
    
    
      The invention is described in detail hereinafter with the aid of the accompanying figures which illustrate one embodiment thereof by way of non-limiting example.  
       FIG. 1  is a schematic overall view of the device of the invention, applied to a fuel filter and tank of a vehicle.  
       FIG. 2  is an enlarged detail of  FIG. 1 , relating to the fuel filter.  
       FIG. 3  is an enlarged detail of  FIG. 1 , relating to the second means for separating water from the fuel. 
    
    
       FIG. 1  shows a traditional circuit for feeding fuel from the tank to the engine of a vehicle.  
      This circuit comprises: 
          a tank  2  for the fuel fed to the vehicle,     a fuel filter  3  having a filtering means  31  for filtering the fuel entering the filter  3  and for separating the water present therein, and also having a separated water collection chamber positioned downstream of the filtering means  31 ,     means for transferring fuel from the that region  33  of the filter  3  lying downstream of the filtering means  31  to the engine feed means  5 , and     means for feeding fuel from the tank  2  to the inlet of the filter  3  at a greater rate than the maximum flow rate transferred from the filter  3  to the feed means  5 , and specifically comprising a low pressure (1-20 bar) pump  41  applied to the tank and a fuel conduit  42  which feeds fuel from the pump  41  to the inlet of the filter  3 .        

      In the embodiment shown in  FIG. 1 , the engine feed means  5  comprises a high pressure pump  51  connected at its inlet to a conduit  52 , the entry of which is applied to the downstream region  33  of the filter  3 , and the delivery  53  of which feeds an injection device  54  for the engine (of known type and illustrated only schematically in the figures). The illustrated type of feed means  54  operates by withdrawing at its inlet a fuel flow rate far in excess of that fed to the engine; consequently the pump  51  then discharges the residual part of the fuel to the tank  2  through a conduit  55 . However the invention is equally applicable to circuits in which the pump  51  does not comprise a return conduit  55  to the tank.  
      The illustrated filter  3  comprises an outer casing  34 , the central part of which houses the filtering means  31  of the vertical cylindrical toroidal cartridge type defining in its interior a closed chamber  31   a  coaxial with the casing  34 . This possesses an inlet  34   a  connected to the conduit  42  to feed the flow into the inner chamber  31   a.    
      Beyond the filtering means  31 , the casing defines an outer annular chamber  33  defining said region lying downstream of the filtering means. Below said chamber  33 , the casing  34  defines, under the filtering means  31 , said water collection chamber  32  which communicates freely and amply with the overlying annular chamber  33 .  
      The filtering means  31  is able to both filter the fuel from solid or semi-solid parts, and to aggregate the water particles present therein to cause them to enlarge and then fall into the chamber  32 .  
      At the top of the chamber  33  there is an outlet  33   b  to which the conduit  52  feeding the pump  51  is connected.  
      According to the invention, there are provided second means  10  for separating the water from the fuel, disposed in a position separated from and external to the fuel filter  3  and releasing the treated fuel to the tank  2 , and a second chamber  15  for collecting the water separated by the means  10 .  
      Said second collection chamber  15  is defined by a receptacle  16  incorporated into the interior of the fuel tank  2  and has a capacity many times greater than the first collection chamber  32 , to the extent of containing a water quantity at least equal to that separated from the fuel during a travel distance of such length as to require on termination a more general servicing of the vehicle at a service station.  
      In the embodiment shown in the figures, the second water separation means  10  comprise a downwardly inclined frusto-conical surface  11  along which the liquid is made to run, and which lies above the second collection chamber  15 . In addition, in the upper part of the receptacle  16   a  series of passages  12  is provided for fuel passage from the top of the chamber  15  to the inner chamber  29  of the tank  2 , they being provided with filtering means  12   a  for retaining water. The invention also comprises second means for transferring liquid from the base of the first collection chamber  32  to the water separation means  10  at the residual flow rate between that which enters the filter  3  and that transferred to the feed means  5 . This residual flow rate has a value greater than the possible rate at which the separated water can accumulate in the first collection chamber  32 .  
      Said second transfer means comprise a valve  20  positioned at the base of the first collection chamber  32 , to hinder the passage of liquid in such a manner as to reduce the flow rate passing through it to an extent compatible with the required fuel transfer from the filter  3  to the feed means  5 . To the exit of the valve  20  there is then connected a conduit  21 , the final end  21   b  of which feeds the liquid onto the highest portion of the frusto-conical surface  11 .  
      The device of the invention operates in the following manner. During vehicle operation, the pump  41  feeds a continuous flow of fuel from the tank to the inlet  34   a  of the filter  3 , to enter the internal chamber  31   a  and from there to pass through the filtering means  31  to the outer chamber  33 . In passing through the filtering means  31 , the fuel is filtered and in addition the water particles present therein aggregate to halt on the outer surface of the filtering means  31 . Moreover, as the water is of greater density than the fuel (diesel oil), said aggregated particles descend along the outer surface of the means  31  and into the underlying collection chamber  32 .  
      A part of the liquid reaching the filter  3  is transferred to the pump  51  of the feed means  5  via the conduit  52 , in such a quantity as to satisfy the requirements of the engine. This withdrawn part is the most purified part of the fuel.  
      The residual liquid part which reaches the filter  3  is withdrawn from the collection chamber  32  and transferred to the second separation means  10 . The rate of this withdrawal is programmed at a greater value than the maximum water quantity that can accumulate in the chamber  32 . Consequently the water in the chamber  32  can never exceed the maximum safety level for the chamber itself, hence avoiding any risk deriving from the fact that the filtering means  31  may work even partially immersed in the water.  
      The valve  20  serves to create an obstacle to liquid passage such that the liquid present in the filter  3  downstream of the filtering means  31  is distributed to the pump  51  and to the second separation means  10  at the scheduled flow rates.  
      In the embodiment shown in the figures, the valve  20  comprises a valving member  22  urged by a spring  24  to close a passage  23 . When the pressure in the chamber  32  exceeds the value of the spring  24 , the liquid passes through the passage  23 .  
      This valve is preferred when a relatively high flow rate (50-200 litres/hour) is transferred through the conduit  42 .  
      In other cases, for example for relatively low flow rates (2-5 litres/hour), a valve  20  of cheaper construction, such as a simple constriction for the fluid, can be provided.  
      The liquid leaving the chamber  32  comprises separated water present in the chamber plus a fuel part. These two parts are again separated by the second means  10 , when the flow is released onto the inclined surface  11  which, by slowing the flow down, causes the water molecules (already aggregated into droplets by the filtering means  31 ) to combine and precipitate onto the base of the collection chamber  15 . In this respect the water molecules are denser than the diesel oil molecules and consequently tend to precipitate towards the base of the chamber  15 .  
      While the water collects on the base of the chamber  15 , the fuel remains in the upper part of the said chamber and overflows towards the inner chamber  29  of the tank  2  through the passages  12 .  
      By suitably dimensioning the collection chamber  15 , on the basis of a statistical estimate of the probability of finding determined quantities of water in the diesel oil supplied to the distributor network, the vehicle user does not have to worry about monitoring the warning light on the instrument panel indicating water presence in the filter  3 . In this respect, the chamber  15  can be sized for such a volume as to enable container emptying to be carried out by the service station during routine servicing.  
      For greater safety, known alarm devices could obviously also be associated with the filter  3  to monitor the level of water which accumulates in the chamber  32 .  
      Numerous modifications of a practical and applicational nature can be made to the invention but without leaving the scope of the inventive idea as claimed below.