Patent Publication Number: US-2005133451-A1

Title: A full-flow microfiltration device and method for filtering fluids

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of U.S. Provisional Application No. 60/532,077, entitled “BYPASS FILTER AND METHOD OF FILTERING” and filed on Dec. 23, 2003. 
    
    
     TECHNICAL FIELD  
      The present invention relates generally to filter devices, and more particularly to a full-flow microfiltration device and method for filtering fluid in a hydraulic system.  
     BACKGROUND  
      It is well known that solid-particle contamination can damage automotive transmission systems. Two common types of contamination include Type I contamination and to a greater extent Type II contamination.  
      Type I contamination usually comprises substantially large particles having diameters larger than about 150 microns. These particles can include remnants from the manufacturing processes utilized for building the transmission systems. This contamination can rapidly damage the systems and lead to early-life repairs.  
      Also, the more abundant Type II contamination usually includes particles having diameters less than about 60 microns. These particles can be debris generated from component wear, as well as particles ground up from larger Type I particles. This contamination can cause erratic valve performance, poor cooling, inefficient lubrication, and accelerated degradation of automatic transmission fluid (ATF), all of which promote mid-life transmission failures.  
      The Type II particles, which have diameters roughly within the 40 to 60 micron range, usually are removed from the ATF by coarse full-flow filters. These coarse filters typically have substantially low flow resistance.  
      Additionally, the Type II particles, which have diameters less than about 40 microns, can be removed from the ATF by microfiltration devices. It is understood that this fiber material is sufficiently fine for filtering the small Type II particles from the ATF. For this reason, the microfiltration device typically has high flow resistance and only allows about ten percent of the ATF to pass therethrough. In that regard, the microfiltration device typically is integrated within the transmission system in a parallel configuration with respect to a main flow of the ATF. In this way, the transmission system typically requires additional tubing for providing the parallel attachment of the microfiltration device.  
      Furthermore, the microfiltration devices each typically include a rigid housing and a filter cartridge that is clamped between the opposing ends of the housing. The filter cartridge usually is made of a fine, substantially deformable fiber material. Examples of this fiber material can include paper-like materials, felt-like materials, and glass-fiber materials.  
      Additionally, the fiber material&#39;s high resistance to flow creates a high pressure differential from an inlet surface to an outlet surface of the fiber material. This pressure differential typically is sufficiently high for compressing the deformable fiber material in a transverse direction thereby increasing the filter cartridge&#39;s axial length. On the other hand, when the flow is halted, the fiber material can decompress and expand transversely so as to shorten the filter cartridge&#39;s axial length. These slight changes in the filter cartridge&#39;s length can create a transient gap between the opposing end faces of the filter cartridge and the rigid housing. This gap can allow ATF to circumvent the filter cartridge and pass through the microfiltration device without being cleaned. Such a result clearly is undesirable.  
      It would therefore be desirable to provide a full-flow microfiltration device that does not require additional tubing and can more efficiently filter fluid despite changes in length of the filter cartridge when flow through the microfiltration device is commenced, halted, or otherwise changed.  
     SUMMARY OF THE INVENTION  
      The present invention provides a full-flow microfiltration device and method for filtering fluid in a hydraulic system. The device includes a housing and a filter medium sealingly coupled to and contained within the housing. The housing and the filter medium define a central chamber and a concentric chamber. The central chamber directly communicates with an entry port and an exit port formed within the housing for directing a first main flow through the filter device. The concentric chamber directly communicates with an inlet port and an outlet port formed within the housing for directing a second main flow through the filter device. A portion of the second main flow is drawn from the concentric chamber through the filter medium into the central chamber and into the first main flow.  
      One advantage of the present invention is that a microfiltration device is provided that can be integrated within full-flow lines so as to dispense with the need for a parallel configuration, as well as the additional tubings, couplings, labor, time, and costs associated therewith.  
      Another advantage of the present invention is that a microfiltration device for a hydraulic system is provided that decreases the number of components of the hydraulic system and increases the available space within an engine compartment.  
      Yet another advantage of the present invention is that a microfiltration device for a hydraulic system is provided that can decrease leakage around a filter medium and improve fluid purity.  
      Still another advantage of the present invention is that a microfiltration device for a hydraulic system is provided that can provide a substantial pressure differential across a filter medium for drawing an increased amount of fluid through the filter medium.  
      Yet another advantage of the present invention is that a microfiltration device for an automatic transmission hydraulic system is provided that can improve general transmission durability, shift timing, and shift feel.  
      Still another advantage of the present invention is that a microfiltration device for an automatic transmission hydraulic system is provided that can remove contaminants from the lubricant so as to decrease clutch and band deterioration, as well as wear on bearings.  
      Yet another advantage of the present invention is that a microfiltration device for an automatic transmission hydraulic system is provided that can substantially decrease the amount of copper and iron debris in the automatic transmission fluid (ATF) thereby improving lubrication and cooling, and generally increasing the life of the ATF.  
      Other advantages of the present invention will become apparent upon considering the following detailed description and appended claims, and upon reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of the examples of the invention:  
       FIG. 1  is a schematic diagram of an automatic transmission hydraulic system having a full-flow microfiltration device, according to one advantageous embodiment of the claimed invention.  
       FIG. 2A  is a cross-sectional view of the full-flow microfiltration device shown in  FIG. 1 , illustrating the full-flow microfiltration device having a central chamber with a first main flow passing therethrough and a concentric chamber with a second main flow passing therethrough - a portion of the second main flow being drawn through the filter medium into the first main flow.  
       FIG. 2B  is a cross-sectional view of the full-flow microfiltration device shown in  FIG. 2A , illustrating the housing remaining sealingly coupled to the filter medium as the filter medium decompresses when the hydraulic system is halted or otherwise provides a substantially lesser flow of fluid through the full-flow microfiltration device.  
       FIG. 3  is a logic flow diagram of a method for operating the hydraulic system shown in  FIG. 1 , according to one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      In the following figures, the same reference numerals are used to identify the same components in the various views.  
      The present invention is particularly suited for a full-flow microfiltration device (“filter device”) integrated within an automatic transmission hydraulic system (“hydraulic system”). However, the filtration device can be integrated within various other hydraulic systems as desired. Also, the device can instead be utilized for coarse filtration or in a parallel configuration as desired. In this regard, it will be understood that the embodiments described herein employ features where the context permits. In other words, various other embodiments without the described features are contemplated.  
      Referring to  FIG. 1 , there is shown a schematic diagram of a hydraulic system  10  having a full-flow filter device  12  integrated therein, according to one advantageous embodiment of the claimed invention.  
      This hydraulic system  10  includes an automatic transmission system  14  and utilizes automatic transmission fluid (ATF) for cooling and lubricating the automatic transmission system  14 . However, it will be appreciated that the hydraulic system  10  can instead include other suitable mechanical systems, which require fluid for lubrication, cooling, various other purposes; or any combination thereof.  
      The automatic transmission system  14  is coupled to a conventional radiator  16  for cooling the ATF. However, it is contemplated that the hydraulic system  10  can instead include various other suitable heat exchangers as desired. Also, the automatic transmission system  14  and the radiator  16  are further operatively coupled to a pump mechanism  18  for forcing the ATF through the hydraulic system  10 .  
      The pump mechanism  18  forces the ATF through a full-flow coarse filtration device  20 , which includes a coarse filter medium. The coarse filter medium is utilized for removing solid particle contaminants having diameters greater than about 40 microns. In this way, smaller-sized particle contaminants, which have diameters up to about 40 microns, can pass through the coarse filtration device  20  and remain in the ATF. For that reason, it will be understood that the coarse filter medium has a low flow resistance.  
      In accordance with the claimed invention, the hydraulic system  10  further includes the full-flow microfiltration device  12  (“filter device”) coupled between the radiator  16  and the automatic transmission system  14 . As detailed below, it will be appreciated that this filter device  12  provides microfiltration of a full flow of the ATF. In this regard, the filter device  12  is in a serial inline connection with the main supply line  21  and the main discharge line  23  between the radiator  16  and the automatic transmission system  14 . In other words, the filter device  12  is not integrated in a parallel configuration with respect to a full flow of the ATF. This feature is beneficial because additional tubing and couplings, as well as installation time and costs associated therewith, are not required to integrate the filter device  12  into the hydraulic system  10 . Also, this feature provides the hydraulic system with a compact construction and increases available space within an engine compartment.  
      Referring now to  FIGS. 2A and 2B , there are shown cross-sectional views of the filter device  12  shown in  FIG. 1 , according to one advantageous embodiment of the claimed invention.  
       FIGS. 2A and 2B  generally illustrate the filter device  12  having a housing  22  and a filter medium  24  that is sealingly coupled to and contained within the housing  22 . The housing  22  and the filter medium  24  define a central chamber  26  and a concentric chamber  28 .  
      Specifically, the filter medium  24  has a perforated central core portion  30  with a high-efficiency cellulose fiber material  32  mounted thereon. The perforated central core portion  30  of the filter medium  24  defines the central chamber  26  of the filter device  12 . In addition, the housing  22  and the outer periphery of the fiber material  32  define the concentric chamber  28 . In this way, it will be appreciated that the filter medium  24  is disposed within the concentric chamber  28 . It is contemplated that the filter medium  24  can instead have various other suitable constructions as desired.  
      The fiber material  32  has a substantially fine structure for removing small contaminants from the ATF. This fiber material can include paper-like material, felt-like material, glass-fiber material, electrostatic material, various other suitable materials, or any combination thereof as desired. This fiber material removes substantially small solid particles, e.g. those with diameters as low as about 5 microns. For that reason, the filter medium  24  also is highly resistant to flow therethrough. In that regard, the pressure differential across the filter medium  24  can be substantially high when the ATF passes through the filter medium  24 . As detailed below, this high pressure differential can compress the filter medium  24  transversely inward thereby causing the filter medium to lengthen axially.  
      In this embodiment, the housing  22  has an entry port  34  and an exit port  36  formed therein. The entry port  34 , the central chamber  26 , and the exit port  36  are integrated within a main supply line  21  extending generally from the radiator  16  to the automatic transmission system  14 . Specifically, the entry port  34  receives a first main flow  23  of ATF, which is cooled by the radiator  16 . Thereafter, the first main flow  23  is directed through the central chamber  26  and through the exit port  36  to the automatic transmission system  14 .  
      Moreover, in this embodiment, the housing  22  further includes an inlet port  38  and an outlet port  40 . The inlet port  38 , the concentric chamber  28 , and the outlet port  40  are integrated within a main discharge line  25  extending generally from the automatic transmission system  14  to the radiator  16 . In particular, the inlet port  38  receives a second main flow  27  of ATF, which is discharged from the automatic transmission system  14 . The inlet port  38  is configured for directing the second main flow  27  into the concentric chamber  28  and indirectly onto the filter medium  24 . In the example shown in  FIGS. 2A and 2B , the inlet port  38  is configured for at least initially directing the discharged ATF  27  in an axial direction, which is parallel to the filter medium  24 . For that reason, the second main flow  27  is not directly impinged upon the filter medium  24 . Instead, the discharged ATF  27  fills the concentric chamber  28 , surrounds the filter medium  24 , and is substantially evenly distributed over the fiber material  32 . Thereafter, the outlet port  40  directs a substantial portion of the second main flow  27  to the radiator  16 . A pressure differential between the concentric chamber  28  and the central chamber  26  causes a portion  29  of the second main flow  27  to be drawn from the concentric chamber  28 , through the filter medium  24 , and into the central chamber  26  and the main supply line  21 .  
      In one embodiment, the perforated central core portion  30  of the filter medium  24  includes a venturi tube  56  for drawing a portion  29  of the second main flow  27  from the concentric chamber  28  through the filter medium  24  into the central chamber  26  and the first main flow. As is known in the art, the venturi tube  56  operates based on the Bernoulli principle. Specifically, the venturi tube  56  is a short pipe with a constricted passage that increases the velocity and lowers the pressure of a fluid passing through it. In this way, the venturi tube  56  creates a substantial pressure differential between the central chamber  26  and the concentric chamber  28 . This pressure differential can be utilized for drawing a greater portion  29  of the second main flow  27  from the concentric chamber  28  through the filter medium  24  into the central chamber  26 . However, it will be appreciated that the filter device  12  can lack the venturi tube  56  and have other sufficient construction for creating a suitable pressure differential for drawing discharged ATF through the filter medium  24 .  
      The filter medium  24  has opposing end faces  42 ,  42 ′ that are sealingly coupled to opposing end portions  44 ,  44 ′ of the housing  22 . For that reason, this construction prevents the discharged ATF from circumventing the filter medium  24  by flowing from the concentric chamber  28  into the central chamber  26  via a gap between the housing  22  and the end faces  42 ,  42 ′ of the filter medium  24 . In this way, the filter device  12  requires the discharged ATF to flow through the fiber material  32  of the filter medium. This feature is advantageous because the filter device  12  can remove a greater amount of contaminants from the ATF despite changes in the size of the filter medium  24 .  
      Referring to both  FIGS. 2A and 2B , the end portions  44 ,  44 ′ of the housing  22  each include three annular ribs  46  extending therefrom for pressing into and sealingly engaging the respective end faces  42 ,  42 ′ of the filter medium  24 . This feature is beneficial for further preventing discharged ATF from circumventing the filter medium  24 . However, it is contemplated that more or less than three annular ribs can be utilized as desired.  
      As best shown in  FIG. 2A , in this embodiment, the opposing end portions  44 ,  44 ′ of the housing  22  are comprised of a resilient material for deforming and remaining sealingly coupled to opposing end faces  42 ,  42 ′ of the filter medium  24 . In this way, the housing  22  remains sealingly coupled to the filter medium  24  when the filter medium  24  changes in axial length. This resilient material preferably is sheet metal. However, it will be appreciated that the housing  22  can instead be comprised of a variety of other suitable materials as desired.  
      Specifically,  FIG. 2A  illustrates a substantially high pressure gradient across the filter medium  24  for forcing a small portion of the ATF to flow through the fine filter medium  24 . This pressure gradient can be sufficiently high for compressing the deformable filter medium  24  against its perforated central core portion  30  inwardly toward its axis. This inward compression can also cause the fiber material  32  to lengthen in a longitudinal direction. The resilient end portions  44 ,  44 ′ of the housing  22  likewise deform outwardly and remain sealingly coupled to the respective end faces  42 ,  42 ′ of the filter medium  24 . The pressure gradient is produced by the pump mechanism  18  as it forces the ATF through the hydraulic system  10 .  
      Moreover,  FIG. 2B  shows a substantially lower pressure gradient across the filter medium  24 . One skilled in the art will understand that this low pressure gradient or lack thereof can occur when the pump mechanism  18  is turned off, e.g. when the engine of a vehicle is turned off. This lower pressure gradient allows the filter medium  24  to decompress transversely outward from the axis of the filter medium  24 . This outward expansion can cause the filter medium  24  to shorten in its longitudinal direction away from the end portions  44 ,  44 ′ of the housing  22 . However, these resilient end portions  44 ,  44 ′ likewise deform inwardly and remain sealingly coupled to the respective end faces  42 ,  42 ′ of the filter medium  24 .  
      The opposing end portions  44 ,  44 ′ also each have mating portions  48 ,  48 ′ for attaching together. One or both of these mating portions  48 ,  48 ′ have a flange  50  for overlapping the other mating portion  48 ,  48 ′. This flange  50  has internal threading (not shown) formed thereon for engaging external threading (not shown) formed on the other end portion  44 ′. However, it will be appreciated that various other suitable fasteners can be utilized for securing the end portions  44 ,  44 ′ to each other.  
      Each end portion  44 ,  44 ′ of the housing  22  has a self-locating groove  52  formed therein for receiving a self-locating protrusion  54  that extends from the center core portion  30  of the filter medium  24 . The self-locating groove  52  preferably receives the entire length of the self-locating protrusion  54  for allowing the end faces  42 ,  42 ′ of the filter medium  24  to sealingly engage the end portions  44 ,  44 ′ of the housing  22 . This construction positions the filter medium  24  in the concentric chamber  28  for immersing the entire periphery of the filter medium  24  in the discharged ATF. However, it is understood that the self-locating groove  25  can instead receive other suitable lengths of the self-locating protrusion  54  as desired. In addition, it is contemplated that the self-locating groove  52  and the self-locating protrusion  54  can be utilized for locating the filter medium  24  in other suitable positions as desired.  
      In this embodiment, the concentric chamber  28  extends across an axial length of the housing  22 . Also, the housing  22  includes a bulged-out portion  58  as taken from an axial view. This bulged out portion  58  defines an enlarged portion of the concentric chamber  28  and contains the discharged ATF. However, it is contemplated that the concentric chamber  28  can have various other suitable constructions as desired.  
      Referring now to  FIG. 3 , there is shown a logic flow diagram of a method for operating the hydraulic system  10  shown in  FIG. 1 . The method begins in step  100  and immediately proceeds to step  102 .  
      In step  102 , the ATF is pumped through the closed-loop hydraulic system  10  and specifically through the filter medium  24  of the filter device  12 . This step is initiated by activating the pump mechanism  18  of the hydraulic system  10 . In so doing, a first main flow  23  of the ATF is directed from the entry port  34  of the filter device  12  through the central chamber  26  to the exit port  36 . This first main flow  23  originates from the radiator  16  and therefore includes cooled ATF. In addition, a second main flow  27  of the ATF flows from the inlet port  38  of the filter device  12  through the concentric chamber  28  to the outlet port  40 . This second main flow  27  of ATF comes from the automatic transmission system  14  and can therefore include solid particle contaminants from system component wear and various other debris. As shown in  FIG. 2A , the ATF in the first and second main flows  23 ,  27  are separated by the filter medium.  
      The ATF in the first main flow  23  has a substantially lower pressure than the ATF in the second main flow  27 . In this regard, a portion  29  of the discharged ATF in the second main flow  27  is drawn from the concentric chamber  28  through the filter medium  24  into the central chamber  26 . In one embodiment, the central chamber  26  of the filter medium  24  has a venturi tube  56  disposed therein for substantially decreasing the pressure of the ATF in the first flow  23 . For that reason, the pressure differential can substantially increase from the concentric chamber  28  to the central chamber  26 . This substantial pressure differential is beneficial because a greater portion  29  of the discharged ATF  27  can be drawn from the concentric chamber  28  through the filter medium  24  and be cleaned.  
      In addition, it will also be appreciated that the substantial pressure differential across the filter medium  24  can compress the deformable filter medium  24 . Specifically, the filter medium  24  can be compressed transversely inward toward the central chamber  26 . As a result, the filter medium  24  can simultaneously lengthen in a longitudinal direction. The sequence then proceeds to step  104 .  
      In step  104 , the resilient housing  22  deforms to accommodate for the change in size of the filter medium  24  and maintain a sealing engagement between the filter medium  24  and the housing  22 . Specifically, the housing  22  has two end portions  44 ,  44 ′ which are comprised of resilient material, e.g. sheet metal. Also, both of these end portions  44 ,  44 ′ are sealingly coupled to the filter medium  24 . As shown in  FIG. 2A , the resilient end portions  44 ,  44 ′ deform outward when the filter medium  24  lengthens in a longitudinal direction. Also, the resilient end portions  44 ,  44 ′ deform inward when the filter medium shortens in the longitudinal direction. In this way, the resilient end portions of the housing  22  remain sealingly coupled to the filter medium  24  despite changes in the size of the filter medium.  
      While particular embodiments of the invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. Accordingly, it is intended that the invention be limited only in terms of the appended claims.