Abstract:
A stampable thrust washer for a torque converter including an inner circumference, an outer circumference, and a plurality of cutouts disposed in the thrust washer, wherein the cutouts are in fluid communication with the inner and outer circumferences when said thrust washer is engaged between two rotationally engaged components.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/069,893, filed Mar. 18, 2008, which application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention generally relates to thrust washers, more specifically to thrust washers for torque converters, and even more specifically to thrust washers for torque converters which can be manufactured by a stamping process. 
       BACKGROUND OF THE INVENTION 
       [0003]      FIG. 1A  is a cross-sectional view of prior art torque converter  10 . It should be appreciated that only the top half of the torque converter is shown in  FIG. 1A , since the bottom half is substantially a mirror image of the top half. Likewise, only an upper portion of thrust washer  20  is shown. Torque converter  10  is a typical torque converter including pump  12 , turbine  14 , and stator  16 . Torque converter  10  includes prior art thrust washer  20  engaged between turbine hub  30  and piston  40 . The thrust washer is essentially a thin, flat disk with the center removed. Thrust washers are necessary in many torque converters to prevent wear at the point of contact between two components which move relative to each other. Thrust washers are similar to bearings, except thrust washers use fluid lubrication instead of balls or rollers to allow for a smooth rotational motion of two components in contact. 
         [0004]    Specifically, during operation of torque converter  10 , thrust is generated on turbine hub  30 , causing the hub to contact piston  40 . To prevent excessive wear between hub  30  and piston  40 , a thrust washer, for example, thrust washer  20 , is disposed between the hub and the piston. 
         [0005]    The following refers to  FIGS. 1B , and  1 C which show a front and perspective view, respectively, of prior art thrust washer  20 . In order to properly operate, fluid circuits must be provided in the torque converter for cooling fluids, such as oil. An adequate flow of fluid is necessary to change and maintain fluid pressures in the torque converter, particularly for adequate clutch capacity and clutch controllability. Furthermore, thrust bearings must be able to provide a sufficient layer of lubrication to reduce the wear and friction between moving parts. Since the thrust washer blocks some of the necessary fluid circuits, provision must be made to allow fluid to pass between the inner and outer circumferences  22  and  24 , respectively, of washer  20 . Traditionally, to accomplish this fluid communication between the inner and outer circumferences, it is known to provide grooves  26  in face  28  of washer  20 . For purposes of the description herein, the terms inner and outer circumferences may refer the entire surface defined by the inner or outer circumferences, in addition to just the edges. 
         [0006]    Thrust washers are commonly made out of polymers, or plastics, since it is easy to mold grooves into a plastic thrust washer. Unfortunately, plastic thrust washers are quite expensive to produce. Therefore, steel thrust washers are sometimes used, since steel washers are cheaper than their plastic counterparts. However, grooves can not be simply stamped into the steel washers, because this would create protrusions on the face of the washer opposite face from each groove. Such protrusions are not acceptable, because they would detract from the performance of the washers. Therefore, each groove must be machined into the face of steel thrust washers, greatly increasing the cost and time required to make each thrust washer. 
         [0007]    Thus, there is a long-felt need for thrust washers which provide the same fluid flow communication as prior art washers, but which can be more cheaply manufactured. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The present invention broadly comprises a thrust washer for a torque converter including an inner circumference, an outer circumference, and a plurality of cutouts disposed in the thrust washer, wherein the cutouts are operatively arranged to enable fluid communication between the inner and outer circumferences. 
         [0009]    In one embodiment each of the cutouts in the plurality extend radially from the inner circumference towards the outer circumference, and each of the cutouts comes substantially close to, but does not connect to the outer circumference. In another embodiment each of the cutouts in the plurality extend radially from the outer circumference towards the inner circumference, and each of the cutouts comes substantially close to, but does not connect to the inner circumference. In yet another embodiment each radially disposed cutout in the plurality is located between the inner and outer circumferences, but does not connect to either the outer circumference or the inner circumference. 
         [0010]    In yet another embodiment, the plurality of cutouts is arranged in at least one oppositely disposed pair of cutouts. In another embodiment the thrust washer is manufactured by a stamping process. In yet another embodiment the cutouts are equally spaced from each other about the thrust washer. 
         [0011]    Alternatively described, in one embodiment, the present invention thrust washer includes an annular portion and a plurality of openings in the annular portion. In a further embodiment, the thrust washer includes an inner circumference, wherein at least one opening in the plurality of openings is in communication with the inner circumference. In yet another embodiment, the thrust washer includes an outer circumference, wherein at least one opening in the plurality of openings is in communication with the outer circumference. In yet another embodiment, at least one opening in the plurality of openings is enclosed by the annular portion. 
         [0012]    It is a general object of the present invention to provide a thrust washer for a torque converter which includes cutouts for enabling sufficient fluid flow to maintain necessary fluid circuits in the torque converter. 
         [0013]    It is another object of the present invention to provide a thrust washer with the above capability which can be manufactured from steel in a stamping or coining process. 
         [0014]    These and other objects and advantages of the present invention will be readily appreciable from the following description of preferred embodiments of the invention and from the accompanying drawings and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which: 
           [0016]      FIG. 1A  is a cross-sectional view of a top half of a prior art torque converter; 
           [0017]      FIG. 1B  is a front view of a prior art thrust washer; 
           [0018]      FIG. 1C  is a perspective view of the prior art washer shown in  FIG. 1B ; 
           [0019]      FIG. 2A  is a front view of a present invention thrust washer; 
           [0020]      FIG. 2B  is a perspective view of the thrust washer shown in  FIG. 2A ; 
           [0021]      FIG. 3A  is a front view of a present invention thrust washer; 
           [0022]      FIG. 3B  is an enlarged cross-sectional view of a piston and hub in a torque converter, and the portion of the thrust washer generally along line  3 B- 3 B in  FIG. 3A ; 
           [0023]      FIG. 4A  is a front view of the thrust washer of  FIG. 3A  rotated 90 degrees; 
           [0024]      FIG. 4B  is an enlarged cross-sectional view of a piston and hub in a torque converter, and the portion thrust washer generally along line  4 B- 4 B in  FIG. 4A ; 
           [0025]      FIG. 5A  is a front view of a second embodiment for the current invention thrust washer; 
           [0026]      FIG. 5B  is an enlarged cross-sectional view of a piston and hub in a torque converter, and the portion of the thrust washer generally along line  5 B- 5 B in  FIG. 5A ; 
           [0027]      FIG. 6A  is a perspective view of a cylindrical coordinate system demonstrating spatial terminology used in the present application; and, 
           [0028]      FIG. 6B  is a perspective view of an object in the cylindrical coordinate system of  FIG. 6A  demonstrating spatial terminology used in the present application. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the invention. While the present invention is described with respect to what is presently considered to be the preferred aspects, it is to be understood that the invention as claimed is not limited to the disclosed aspects. 
         [0030]    Furthermore, it should be understood that this invention is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It should also be understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims. 
         [0031]    Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices, and materials are now described. 
         [0032]      FIG. 6A  is a perspective view of cylindrical coordinate system  80  demonstrating spatial terminology used in the present application. The present invention is at least partially described within the context of a cylindrical coordinate system. System  80  has a longitudinal axis  81 , used as the reference for the directional and spatial terms that follow. The adjectives “axial,” “radial,” and “circumferential” are with respect to an orientation parallel to axis  81 , radius  82  (which is orthogonal to axis  81 ), and circumference  83 , respectively. The adjectives “axial,” “radial” and “circumferential” also are regarding orientation parallel to respective planes. To clarify the disposition of the various planes, objects  84 ,  85 , and  86  are used. Surface  87  of object  84  forms an axial plane. That is, axis  81  forms a line along the surface. Surface  88  of object  85  forms a radial plane. That is, radius  82  forms a line along the surface. Surface  89  of object  86  forms a circumferential plane. That is, circumference  83  forms a line along the surface. As a further example, axial movement or disposition is parallel to axis  81 , radial movement or disposition is parallel to radius  82 , and circumferential movement or disposition is parallel to circumference  83 . Rotation is with respect to axis  81 . 
         [0033]    The adverbs “axially,” “radially,” and “circumferentially” are with respect to an orientation parallel to axis  81 , radius  82 , or circumference  83 , respectively. The adverbs “axially,” “radially,” and “circumferentially” also are regarding orientation parallel to respective planes. 
         [0034]      FIG. 6B  is a perspective view of object  90  in cylindrical coordinate system  80  of  FIG. 6A  demonstrating spatial terminology used in the present application. Cylindrical object  90  is representative of a cylindrical object in a cylindrical coordinate system and is not intended to limit the present invention in any manner. Object  90  includes axial surface  91 , radial surface  92 , and circumferential surface  93 . Surface  91  is part of an axial plane, surface  92  is part of a radial plane, and surface  93  is part of a circumferential plane. 
         [0035]      FIG. 2A  is a front view of present invention thrust washer  100 .  FIG. 2B  is a perspective view of thrust washer  100  shown in  FIG. 2A . 
         [0036]    The following should be viewed in light of  FIGS. 2A and 2B . Thrust washer  100  includes inner circumference  102  and outer circumference  104 . Thrust washer  100  is arranged to provide fluid communication between the inner and outer circumferences. By this we mean that fluid is allowed to flow through the washer so that fluid can travel between an area generally radially beyond the outer circumference and an area proximate to the inner circumference. Alternatively stated, the washer does not block necessary fluid circuits in the torque converter, for example, fluid circuits necessary to operate a converter by-pass clutch (not shown). In addition to enabling the necessary fluid circuits, the cutouts also enable the fluid to flow between the thrust washer and components with which the thrust washer is in contact, for example, piston  110 , to create a hydrodynamic layer, which is essential to the functionality of the thrust washer and the components. 
         [0037]    To provide fluid communication, thrust washer  100  includes cutouts  106  and  108 . In a preferred embodiment, cutouts  106  originate at outer circumference  104  and extend radially inward towards inner circumference  102 , but do not fully extend to circumference  102 . Alternately stated, the cutouts open to outer circumference  104  and extend part way to the inner circumference. There is a small portion of material between each cutout  106  and the inner circumference. Likewise, cutouts  108  originate at inner circumference  102  and extend radially outward towards outer circumference  104 , but do not fully extend to circumference  104 . Alternately stated, the cutouts open to the inner circumference and extend part way to the outer circumference. There is a small portion of material between each cutout  108  and the outer circumference. 
         [0038]      FIG. 3B  is an enlarged cross-sectional view of a piston and hub in a torque converter, and the portion of the thrust washer generally along line  3 B- 3 B in  FIG. 3A .  FIG. 3B  shows thrust washer  100  installed between hub  112  and piston  110  in a torque converter (only partially shown). It should be appreciated that hub  112  and piston  110  are similar to hub  30  and piston  40  in torque converter  10 . Gap  114  in chamber  116  is formed between the thrust washer and one or more components proximate axial side  118  of the thrust washer, for example, rivet  120 . Cutout  108 A is in fluid communication with chamber  116  and chamber  122  on radial side  124  of the thrust washer. That is, the cutout provides fluid communication between the chambers as shown by flow path  126 . For example, fluid exchange between the chambers through the thrust washer can enable operation of the by-pass clutch noted above and the fluid exchange can provide lubricating fluid for side  124  and the piston. It should be clear that chamber  116  is generally radially beyond outer circumference  104 , and that chamber  122  is generally proximate to inner circumference  102 . Therefore, cutout  108 A in the shown embodiment provides fluid communication between the outer and inner circumferences. 
         [0039]    It should be understood that the direction of flow shown in  FIG. 3B  can be reversed, that is, fluid can flow from chamber  122  to chamber  116  through the cutouts. 
         [0040]      FIG. 4A  is a front view of thrust washer  100  shown in  FIG. 3A , rotated 90 degrees. 
         [0041]      FIG. 4B  is an enlarged cross-sectional view of the portion of the torque converter shown in  FIG. 3B  showing thrust washer  100  shown in  FIG. 4A  and piston  110  and hub  112 , the portion of the thrust washer generally along line  4 B- 4 B in  FIG. 4A . The following should be viewed in light of  FIGS. 4A and 4B . Chamber  116  is in fluid communication with cutout  106 A partly through the opening of the cutout at the outer circumference and partly through the opening in radial side  118 . Gap  128 , between the cutout and chamber  122 , is formed between the washer and the piston. Thus, cutout  106 A is in fluid communication with chamber  120  and chamber  122 . That is, the cutout provides fluid communication between the chambers as shown by flow path  130 . For example, fluid exchange between the chambers through the thrust washer can enable operation of the by-pass clutch noted above and the fluid exchange can provide lubricating fluid for side  124  and the piston. Therefore, cutout  106 A in the shown embodiment provides fluid communication between the outer and inner circumferences. 
         [0042]    It should be understood that the direction of flow shown in  FIG. 4B  can be reversed, that is, fluid can flow from chamber  122  to chamber  116  through the cutouts. 
         [0043]      FIG. 5A  is a front view of present invention thrust washer  200 . 
         [0044]      FIG. 5B  is an enlarged cross-sectional view of a portion of a torque converter showing thrust washer  200  shown in  FIG. 5A  and a piston and hub, the portion of the thrust washer generally along line  5 B- 5 B in  FIG. 5A . The following should be viewed in light of  FIGS. 5A and 5B . Thrust washer  200  includes inner circumference  202  and outer circumference  204 . Thrust washer  200  is arranged to provide fluid communication between the inner and outer circumferences. By this we mean that fluid is allowed to flow through the washer so that fluid can travel between an area generally radially beyond the outer circumference and an area proximate to the inner circumference. Alternatively stated, the washer does not block necessary fluid circuits in the torque converter, for example, fluid circuits necessary to operate a converter by-pass clutch (not shown). In addition to enabling the necessary fluid circuits, the cutouts also enable the fluid to flow between the thrust washer and components with which the thrust washer is in contact, for example, piston  210  to create a hydrodynamic layer, which is essential to the functionality of the thrust washer and the components. 
         [0045]    To provide fluid communication, thrust washer  200  includes cutouts  206 . In a preferred embodiment, cutouts  206  are fully enclosed by the washer. That is, the cutouts do not open to either the inner of the outer circumference. There is a portion of material between each cutout  206  and the inner and outer circumferences. 
         [0046]      FIG. 5B  shows thrust washer  200  installed between hub  212  and piston  210  in a torque converter (only partially shown). Gap  214  in chamber  216  is formed between the thrust washer and one or more components proximate axial side  218  of the thrust washer, for example, rivet  220 . Cutout  206 A is in fluid communication with chamber  216  on radial side  218  of the thrust washer. Gap  228  in chamber  222  is formed between the thrust washer and one or more components proximate axial side  224  of the thrust washer, for example, the piston. Cutout  206 A is in fluid communication with chamber  222 . Therefore, the cutout provides fluid communication between the chambers as shown by flow path  226 . For example, fluid exchange between the chambers through the thrust washer can enable operation of the by-pass clutch noted above and the fluid exchange can provide lubricating fluid for side  224  and the piston. 
         [0047]    It should be understood that the direction of flow shown in  FIG. 5B  can be reversed, that is, fluid can flow from chamber  222  to chamber  216  through the cutouts. 
         [0048]    It should be appreciated that in the shown embodiments of  FIGS. 2A-4B , there are two cutouts  106  arranged in an oppositely disposed pair, and two cutouts  108 , which are also arranged in an oppositely disposed pair, with the pair of cutouts  108  evenly spaced between the pair of cutouts  106 . By oppositely disposed we mean that they are 180 degrees apart. In another embodiment, however, there may be more or less cutouts than in the shown embodiment. 
         [0049]    The following refers again to the second embodiment of the current invention thrust washer shown in  FIGS. 5A and 5B . In a preferred second embodiment, thrust washer  200  includes four cutouts  206  instead of cutouts  106  and  108 . As shown in  FIG. 5B , the flow of fluid is able to pass by the washer and communicate between the inner and outer circumferences. Thrust washer  200  may be preferable over thrust washer  100  since the cutouts do not connect to either the inner or outer circumferences, and therefore, thrust washer  200  has more material, and therefore should be more durable. However, in some embodiments, thrust washer  100  may be preferable because the extra material present in thrust washer  200  may slightly restrict the flow of fluid past the washer. Regardless, both embodiments of current invention washer share the advantage of being able to be manufactured by a low cost stamping process. 
         [0050]    Similar to the first embodiment of thrust washer, it should appreciated that thrust washer  200  may have more or less than the four cutouts, shown in the preferred embodiments. Furthermore, the cutouts may be shaped and sized differently, as long as the cutouts can provide sufficient fluid flow communication between the outer and inner circumferences. In either embodiment, the cutouts may be coined, or stamped, such that the edges are chamfered. A chamfered edge around the cutout may enhance the ability of the fluid to flow into and out of the cutouts to provide for between fluid flow communication. It also should be understood that any combination of cutouts opening to the inner circumference, opening to the outer circumference, or fully enclosed are possible in a present invention thrust washer. 
         [0051]    Advantageously, the current invention washer can be fabricated from steel by a relatively simple stamping operation. Unlike grooves  26  in prior art washer  20 , the cutouts in the current invention washer are cut through the entire thickness of the washer, and therefore do not need to be machined. Thus, the current invention washers enable substantial savings in costs and manufacturing time with respect to the prior art washers, which must be machined steel or expensive polymers. 
         [0052]    Lastly, it should be appreciated that the current invention thrust washer can be used in any torque converter known in the art that includes a piston and hub, or two similarly situated components, which are in rotational contact. 
         [0053]    Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, which modifications are intended to be within the spirit and scope of the invention as claimed. It also is understood that the foregoing description is illustrative of the present invention and should not be considered as limiting. Therefore, other embodiments of the present invention are possible without departing from the spirit and scope of the present invention.