Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
  • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
  • F02M61/165—Filtering elements specially adapted in fuel inlets to injector
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/11—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
  • B01D29/31—Self-supporting filtering elements
  • B01D29/35—Self-supporting filtering elements arranged for outward flow filtration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/44—Edge filtering elements, i.e. using contiguous impervious surfaces
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D35/00—Filtering devices having features not specifically covered by groups B01D24/00 - B01D33/00, or for applications not specifically covered by groups B01D24/00 - B01D33/00; Auxiliary devices for filtration; Filter housing constructions
  • B01D35/02—Filters adapted for location in special places, e.g. pipe-lines, pumps, stop-cocks

Definitions

• the present invention relates to filters for a common rail fuel system and more particularly, filters that are utilized in high pressure inlets to fuel injectors.
• Common rail fuel systems are well known for high pressure fuel injection in internal combustion engines. Pressures in common rail systems can range from 250 bar to 2200 bar (3,600 to 32,000 psi). Individual injectors are connected to the common rail by high pressure conduits. Common rail fuel systems utilize electronic controls to control the timing of the beginning of injection and the completion of injection. The timing of the injection cycle may be adjusted electronically. Maintaining close tolerances of the injector components in a high pressure environment is important because it maintains the accuracy of fuel injection events. Debris in the fuel flow can not only obstruct the nozzle and cause unacceptable injector performance, but over time, wear at the close tolerances of the injector components.
• Filters are typically disposed upstream of the injectors to ensure that fuel delivered to the injector nozzles during an injection event is free of debris, insofar as possible.
• Debris in the fuel can be residue from manufacturing or machining in any upstream component such as a pump, a conduit, a valve, or the like. Debris can also include service debris accompanying the fuel itself and not previously filtered.
• Edge filters are normally provided in the coupling between the injector and the fuel conduit or in an extension of the injector as the last component before fuel enters the injector. Edge filters not only block particles of predetermined size, but they also act as particle shredders in that they reduce the size of debris particles in the fuel to an acceptable size less likely to interfere with injection. An acceptable particle size for heavy duty applications in a high pressure system may be as large as 120 microns. Determination of an acceptable size is normally driven by the performance requirements of the injector.
• a typical edge filter of the prior art can be seen in Figs. 1 and 2.
• the edge filter 10 has an inlet end 12 and an outlet end 14.
• One or more inlet channels or flutes 16 extend longitudinally from the inlet end 12 and terminate before they reach the outlet end 14.
• one or more outlet channels or flutes 18 adjacent to the inlet channels extend longitudinally from the outlet end 14 and terminate before they reach the inlet end 12.
• the inlet and outlet channels 16, 18 are separated from each other by ridges 20.
• the diameter of the edge filter 10 at the ridges 20 is less than the diameter of the conduit 21 in which it is disposed so that there an annular gap 23 between the ridges and the conduit.
• a typical gap will measure on the order of 20-50 microns, but the actual size is determined by performance requirements.
• the edge filter 10 is typically made of low carbon steel. Fuel enters the inlet channels 16 and flows over the ridges 20 into the outlet channels 18 (see arrows).
• a filter is commonly known as a sack filter, most often used in the pressure regulator of a common rail.
• a sack filter is cylindrically shaped, with one end open, the other end closed, and plurality of laser-drilled bores in the cylindrical wall. Fuel enters from the closed end, passes through the bores and exits through the open end, and the bores filter particles carried by the fuel. There remains a need to improve the performance of high pressure fuel filters in common rail systems.
• An edge filter for fitting in a high pressure conduit of a fuel injection system comprising a fuel injector includes a filter section formed of inlet channels and outlet channels separated by ridges.
• the ridges have a predetermined diameter less than the conduit diameter, and the difference between the predetermined diameter and the conduit diameter defines an annular gap.
• annular grooves are disposed in at least one of the ridges. Preferably, the annular grooves are disposed in all of the ridges.
• the filter section will typically have three ridges.
• the annular grooves are preferably disposed within a density range of 12-26 grooves per mm and are within a range of 22-35 microns wide.
• the annular grooves are preferably within a range of 36-50 microns deep.
• the annular gap is preferably equal to or less than 22 microns.
• the width of each groove is equal to or greater than the annular gap. In any event, the annular gap and/or grooves are sized so that the highest operational flow rate of fuel through the edge filter will result in a pressure gradient of less than about 300 bar.
• the filter section has a predetermined diameter less than the conduit diameter, and the difference between the predetermined diameter and the conduit diameter defines an annular gap.
• the annular gap is less than 10 times the average diameter of the holes.
• the holes are preferably within a density range of 10-21 holes per mm 2 and each hole has a diameter of approximately 50 microns.
• the gap is sized so that the highest operational flow rate of fuel through the edge filter will result in a pressure gradient of less than about 300 bar or, preferably, 150 bar.
• Fig. 1 is a perspective view of an edge filter of the prior art.
• Fig. 2 is a cross sectional view of a portion of the edge filter of Fig. 1 disposed in a high pressure fuel conduit.
• Fig. 3 is a view, partly in cross section, of an edge filter according to the invention disposed in a high pressure fuel conduit.
• Fig. 4 is an enlarged view of the area marked IV in Fig. 3
• Fig, 5 is a view, partly in cross section, of a sack filter disposed in a high pressure fuel conduit according to the invention.
• Fig. 6 is an enlarged view of the area marked VI in Fig. 5.
• Fig. 7 is a perspective view, partly in cross section, of a high pressure fuel conduit with a second embodiment of a sack filter, according to the invention.
• Fig. 8 is an end view of the installed sack filter of Fig. 7.
• Fig. 9 is a cross sectional view of the sack filter of Fig.8 taken along line 9-9.
• a first embodiment of the invention is illustrated in an edge filter 100 adapted to be mounted in a high pressure conduit 102.
• the edge filter 100 has an inlet end 104, a filter section 106, and an outlet end 108.
• the filter section 106 extends between the inlet end 104 and the outlet end 108.
• a plurality of inlet channels 110 (equidistant from each other) extend longitudinally from the inlet end 104 and terminate before they reach the outlet end 108.
• three inlet channels 110 extend through the inlet end 104.
• a plurality of outlet channels 112 interspersed between the inlet channels 1 10 extend longitudinally from the outlet end 108 and terminate before they reach the inlet end 104.
• the outlet channels 112 extend through the outlet end 108.
• the inlet and outlet channels 1 10, 1 12 are separated from each other by ridges 114 which are in the filter section 106.
• the diameter D of the edge filter 100 at the inlet and outlet ends 104, 108 is the same as (or nominally larger than) the inside diameter of the high pressure conduit 102.
• the edge filter 100 can be press fit into the conduit 102 and held in place by friction of the outer surfaces of the inlet and outlet ends 104, 108 bearing against the inside surface of the conduit 102.
• the inlet and outlet ends 104, 108 serve as securing sections to hold the edge filter 100 in place within the high pressure conduit 102.
• the diameter d of filter section 106, i.e., the edge filter 100 at the ridges 1 14, is less than the diameter D, so that there is an annular gap 116 between the ridges 1 14 and the inside surface of the conduit 102.
• annular gap 116 Between the inlet and outlet ends 104, 108 is a plurality of annular grooves 118 on the ridges 114. With the additional area between adjacent inlet and outlet channels 110, 112 afforded by the grooves 118, the annular gap 116 can be smaller than known in the prior art without further restricting flow.
• the annular gap 116 is sized to provide a secondary filtration in addition to the ridges 114 so that preferably, particles equal to or greater than about 120 microns in any dimension will be effectively shredded or deformed so as to prevent interference with an injection event at the fuel injector.
• An acceptable pressure drop is typically less than about 300 bar at the highest operational flow rate, which can be maintained with a smaller annular gap, according to the invention.
• the annular gap 116 can be less than 20 microns in the invention.
• the distance between adjacent grooves 118 may be on the order of 80 microns.
• the width Ai of each groove 118 will be in a range of 22-35 microns, and the depth 122 of each groove 118 will be in a range of 36-50 microns.
• the density of the grooves 118 on the ridges 114 is preferably in a range of 12-26 grooves per mm.
• the width of each groove 118 is preferably greater than or equal to the annular gap 1 16.
• the edge filter 100 is typically made of low carbon steel.
• fuel at high pressure enters the inlet channels 110, flows over the ridges 114 and through the grooves 118 into the outlet channels 112.
• Debris particles, and especially high aspect ratio debris particles that are carried in the fuel are presented with sharp edges at the ridges 114, both at the top of the ridges 114 and at the sides and bottom of the grooves 118. They are also presented with smaller openings in both the annular gap 116 and grooves 118 through which to pass. Consequently, there is a higher probability of such particles being shredded or reduced to an acceptable size by the edge filter 100. Moreover, this improved performance is achieved with no more flow restriction than exists in the prior art.
• a second embodiment of the invention is illustrated in a sack filter 200 mounted in a high pressure conduit 202.
• the sack filter 200 is formed from a cylinder having an inlet section 204, a filter section 206, and an end section 208.
• the inlet section 204 has a diameter D larger than the diameter d of the filter section 206.
• the filter section 206 comprises a plurality of holes 210 extending through the wall, preferably laser drilled in a range of approximately 10-21 holes /mm 2 . Each hole has a diameter of about 50 microns.
• the material is preferably stainless steel.
• the end section 208 is closed by crimping to create a blind sack 211, preferably closed in that it has no holes to provide an exit.
• the blind sack 211 is that volume of the sack filter more than about lmm beyond the last hole 210 downstream from the inlet section 204.
• the diameter D of the inlet section 204 is the same as (or nominally larger than) the inside diameter of the high pressure conduit 202.
• the sack filter 200 can be press fit into the conduit 202 and held in place by friction of the outer surface of the inlet section 204 bearing against the inside surface of the conduit 202.
• the inlet section 204 serves as a securing section to hold the sack filter 200 in place within the high pressure conduit 202. Since the diameter d of the filter section 206 is less than the diameter D, there is an annular gap 212 between the filter section 206 and the inside surface of the conduit 202.
• the annular gap 212 is set to be less than 10 times the diameter of a single hole 210, but not so much less that the pressure drop across the filter is unacceptable.
• An acceptable pressure drop is about 150 bar at the highest operational flow rate.
• An acceptable target flow rate is 600 liters/hr. at 100 bar. It will be understood that these values are exemplary only, and that actual values can be higher or lower depending upon performance requirements.
• the end section 302 is closed to create a blind sack 304 in that it has no holes to provide an exit.
• the blind sack 304 is that volume of the sack filter more than about lmm beyond the last hole 210 downstream from the inlet section 204.
• the blind sack 304 functions identically to the blind sack 211 illustrated in Figs. 6 and 7. It has been found advisable to ensure that the sack filter 302 remains centered within the high pressure conduit 202. If so, then the annular gap 212 will maintain its dimension relative to the holes 210 around the entire filter section 206. To maintain this centering, a plurality of lobes 306, preferably three, is formed in outer wall of the end section 302. Each lobe 306 has a peripheral surface 308 that has a radius centered on the longitudinal axis 310 of the sack filter 300 substantially identical to the radius of the high pressure conduit 202.
• the tolerances are such that the lobes 306 will just touch the inside surface of the high pressure conduit 202, but not so tightly as to make it difficult to insert the sack filter into the conduit. It will be understood that the inlet section preferably retains the sack filter 300 within the conduit 202 by friction. The lobes 306 need only maintain the sack filter centered within the conduit.
• each lobe 306 will be sized so that the gaps 312 between them will define a cross sectional area equal to or greater than the cross sectional area of the annular gap 212.
• the lobes 306 must be sized so as to not obstruct or limit the flow of fuel.
• the sack filter 300 can be formed by deep drawing the material, and then crimping the end section 302 to form the lobes 306.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fuel-Injection Apparatus (AREA)

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• 2004
  • 2004-10-28 EP EP04796633A patent/EP1812708A1/de not_active Withdrawn
  • 2004-10-28 WO PCT/US2004/035790 patent/WO2006049598A1/en not_active Ceased

Non-Patent Citations (1)

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