Abstract:
The sliding strut bearing has two rigid body positioned in a plastic housing and a synthetic resin sliding bearing positioned between the two rigid bodies. The rigid bodies are metal and provide structural rigidity allowing a spring seat to be incorporated into the plastic housing and an overall reduction in the height of the bearing.

Description:
[0001]    This application claims the priority of U.S. 61/088,633 filed Aug. 13, 2008, which is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present Invention relates to synthetic resin made sliding bearings and, more particularly, to synthetic resin sliding bearings which are suitable for use in strut-type suspensions (MacPhearson-type). 
       BACKGROUND OF THE INVENTION 
       [0003]    MacPhearson-style strut assemblies are well known in the automotive industry. Such assemblies typically comprise a strut which extends upward from the steering knuckle of the wheel and terminates in a top mount which is attached to the chaise of the vehicle. The strut has a rod with a hydraulic cylinder and a spring for absorbing movement of the wheel. The joint between the top mount and the strut contains a strut bearing. A metal spring seat is attached below the bearing and around the rod to terminate and support one end of the spring. A jounce bumper to prevent coil-on-coil compression of spring is mounted also below the bearing and around the rod at the top mount. The strut bearing typically comprises roller bodies or, a synthetic resin sliding bearing. 
         [0004]    A typical MacPherson strut assembly is illustrated in  FIG. 1 . Rod  10  terminates at top mount  11 . Between rod  10  and top mount  11  is strut bearing  12  with roller bodies. Spring  13  is housed in spring seat  14  which is conventionally a metal frame. Between spring  13  and spring seat  14 , is rubber isolator  15 , dust boot  16  extends downward from rubber isolator  15  and jounce bumper  17  is mounted on rod  10  in jounce bumper support cup  18 . 
         [0005]    There is a need to reduce the overall height of the strut bearing. One way to reduce the height of strut bearing  12 , is to use a strut bearing with synthetic resin sliding bearing, see, for example, U.S. Pat. Nos. 4,969,752, 5,476,326, and 6,918,701. One of the drawbacks of these synthetic resins sliding bearing is that, a metal spring seat is needed between the bearing and the spring. 
       OBJECTS OF THE INVENTION 
       [0006]    It is an object of the present Invention to reduce the overall height of the strut bearing. It is also the object of the Invention to control the torque of the bearing. 
         [0007]    These and other objects of the present Invention will be more readily understood by reference to the following description. 
       SUMMARY OF THE INVENTION 
       [0008]    The present Invention obtains the objectives by a synthetic resin sliding bearing position between rigid bodies which are then positioned in a plastic housing to form the strut bearing. 
         [0009]    This arrangement of the strut bearing allows for a decrease in the overall height of the bearing due to the elimination of the roller elements and the metal spring seat. It also allows the spring to be seated directly against the lower end of plastic housing. Torque selection is provided by the bearing of the present Invention because of the use of the rigid bodies inside the housing of the bearing. Furthermore, because of the placement of the synthetic resin sliding bearing between the two rigid bodies, the outside plastic housings can be made of a wide variety of different materials thereby eliminating the need for the upper and lower housing to be made specifically of a synthetic resin sliding material. Specifically, the housing can be made of thermoplastic materials with or without glass stiffening materials. 
         [0010]    Broadly, the sliding strut bearing of the present Invention can be defined as follows: 
         [0011]    a plastic housing which has a through hole for accommodating a rod of a strut, the housing having an inner wall which defines the through hole and encircles the rod; 
         [0012]    a flanged, cylindrical annulus in the housing, the annulus having a cylindrical hollow axially aligned with the through hole and a thrust hollow extending radially outward from the cylindrical hollow, the thrust hollow in a flanged portion of the annulus, the cylindrical hollow having an inside and outside inner wall which are axially aligned with the through hole, the thrust hollow having a top inner wall that extends radially outward from the inside inner wall and a bottom inner wall that extends radially outward from the outside inner wall; 
         [0013]    an inner rigid body abutting the inside and top inner wall; 
         [0014]    an outer rigid body abutting the outside and bottom inner wall; and 
         [0015]    a synthetic resin sliding bearing body positioned between the inner and outer rigid body. 
         [0016]    Preferably, the housing comprises: 
         [0017]    an upper plastic housing having an inner plastic sleeve for encircling the rod and an upper plastic ledge affixed to and extending radially outward from the inner plastic sleeve; 
         [0018]    a lower plastic housing mating, from below with the upper plastic housing and having an outer plastic sleeve spaced apart and encircling the inner plastic sleeve and a lower plastic ledge affixed to and extending from the outer plastic sleeve, the lower plastic ledge spaced apart from the upper plastic ledge; 
         [0019]    a bottom seal formed between a bottom axial edge of the inner plastic sleeve and a bottom axial edge of the outer plastic sleeve; 
         [0020]    a top seal formed between an outer radial edge of the upper plastic ledge and an outer radial edge of the lower plastic ledge; 
         [0021]    the cylindrical hollow is formed between the inner plastic sleeve and the outer plastic sleeve; 
         [0022]    the thrust hollow is formed between the upper plastic ledge and the lower plastic ledge. 
         [0023]    Preferably, the inner rigid body is an inner sleeve in the cylindrical hollow, abutting the inside inner wall and axially aligned with the through hole and an upper thrust washer in the thrust hollow abutting the top inner wall, and axially aligned with the through hole. The washer and the sleeve can be separate or can be joined to form a unitary body having an L-cross sectional appearance. 
         [0024]    Preferably, the outer rigid body is an outer sleeve in the cylindrical hollow, abutting the outside inner wall and axially aligned with the through hole and a lower thrust washer in the thrust hollow abutting the bottom inner wall and axially aligned with the through hole. The sleeve and thrust washer can be separate from one another or can be joined to form a unitary body having an L-shaped cross section. 
         [0025]    Preferably, the inner and the outer rigid body are made of a hard plastic, ceramic or metal. Suitable metals include steel, aluminum or brass. 
         [0000]    Suitable steel includes hardened and non-hardened carbon or stainless steel.
 
Suitable aluminum includes pure aluminum or alloys of aluminum that include copper, zinc or magnesium.
 
Suitable brass includes alloys of copper and zinc in different proportions.
 
Suitable ceramics include cement or a combination of metal and ceramic.
 
         [0026]    Preferably, the synthetic resin sliding bearing body comprises a synthetic resin sliding sleeve positioned between the inner and outer sleeves and a synthetic resin sliding thrust washer positioned between the upper and lower thrust washers. The sliding sleeve can be separate from the sliding thrust washer or the two can be joined to form a solitary unit. The synthetic resin which is used for forming the sliding bearing is suitably self lubricating. Suitable materials for the sliding bearing include polyacetal resins, polyamide resins, polyester resins, such as, polybutyl terephthalate (PBT) and polyolefin resins, such as, polyethylene and polypropylene. More preferably, the resin is a fluoropolymer, such as, polytetrafluoroethylene (PTFE). The sliding bearing is suitably affixed to one of the rigid body by any conventional means to include adhesives, such as, ethylenetetrafluoroethylene (ETFE). This makes a composite material. One well known composite material that can be used for the bearing of the present Invention is sold under the trademark NORGLIDE® which is available from Saint-Gobain Performance Plastics Corp. of Wayne, N.J., U.S.A. A method to make such a composite material is taught in U.S. Publication No. US2007/0212198. 
         [0027]    Suitably, the housing and more specifically, the lower plastic housing has a spring seat on an outer wall. 
         [0028]    More preferably, the housing and more specifically the lower plastic housing has a jounce bumper support cup which is affixed to and extends axially downward from the bottom of the axial edge of the housing. 
         [0029]    These and other aspects of the present Invention may be more readily understood by reference to one or more of the following drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]      FIG. 1  illustrates a conventional MacPherson strut assembly; 
           [0031]      FIG. 2  illustrates the strut of the present Invention with separate thrust washers and separate sleeves; 
           [0032]      FIG. 3  illustrates the present Invention with unitary rigid bodies and unitary sliding bearing; 
           [0033]      FIG. 4  illustrates the present Invention with a unitary outer rigid body, unitary sliding bearing and separate inner rigid bodies; 
           [0034]      FIG. 5  illustrates the present Invention with a unitary inner rigid body, separate outer rigid bodies and a unitary sliding bearing; 
           [0035]      FIG. 6  illustrates the present Invention with unitary outer rigid body, a single thrust inner washer and a unitary sliding bearing; 
           [0036]      FIG. 7  illustrates the present Invention with lower plastic housing acting as a spring seat; 
           [0037]      FIG. 8  illustrates the present Invention with lower plastic housing acting as both a spring seat and jounce bumper support cup; and 
           [0038]      FIG. 9  illustrates the present Invention with the upper housing having jounce bumper support cup and the lower housing having a spring seat. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]    As shown in  FIG. 2 , sliding strut bearing  19  has plastic housing  20  with through hole  10 ′. Plastic housing  20  has upper plastic housing  21 , lower plastic housing  22 . Upper plastic housing being superimposed on lower plastic housing  22  so as to mate the two housings together. Upper plastic housing  21  has inner plastic sleeve  23  for encircling rod  10  and upper plastic ledge  24  which extends radially outward from sleeve  23 . 
         [0040]    Lower plastic housing  22  has outer plastic sleeve  25  and lower plastic ledge  26  which extends radially outward from the top of outer plastic sleeve  25 . A bottom seal  27  is formed at the bottom axial edge of inner plastic sleeve  23  and outer plastic sleeve  25 . Top seal  28  is formed at the outer radial edges of upper plastic ledge  24  and lower plastic ledge  26 . 
         [0041]    Between housing  21  and housing  22  is a flanged, cylindrical annulus  29 . Flanged, cylindrical annulus  29  is made up of thrust hollow  30  and cylindrical hollow  31 . 
         [0042]    Thrust hollow  30  houses upper thrust washer  32 , lower thrust washer  33  and synthetic resin sliding thrust washer  34 . 
         [0043]    Cylindrical hollow  31  houses inner sleeve  35 , outer sleeve  36  and synthetic resin sleeve  37 . As can be seen in  FIG. 2 , the sleeves  35 ,  36  are separate from the thrust washers  32 ,  33 . 
         [0044]    Inner rigid body is made up of upper thrust washer  32  and inner sleeve  35 . 
         [0045]    Outer rigid body is made up of lower thrust washer  33  and outer sleeve  36 . 
         [0046]    Turning to  FIG. 3 , it can be seen that the thrust washer  32  and sleeve  31  are combined into a unitary body inner flanged sleeve  38  and thrust washer  33  and metal sleeve  36  form a unitary body, outer flanged sleeve  39 . Also, it can be seen that sliding sleeve and the sliding thrust washer are combined to a single resin flanged sleeve  40 . 
         [0047]      FIGS. 4 and 5  illustrate combinations of the flanged sleeves, thrust washer and sleeve combinations. 
         [0048]      FIG. 6  illustrates the embodiment where the inner rigid body has only a thrust washer and no inner sleeve. 
         [0049]    Turning to  FIG. 7 , lower plastic housing  41  has spring seat  42  for spring  13 . 
         [0050]      FIG. 8  illustrates lower plastic housing  41  with spring seat  42  and an integrated jounce bumper support cup  43 . 
         [0051]      FIG. 9  illustrates lower plastic housing  44  with spring seat  45  for spring  13  and upper housing  46  with integrated jounce bumper support cup  47 . 
         [0052]    The plastic housings can be made of thermoplastic materials such as PA 66, POM, PBT with or without stiffening agents such as glass fibers. 
         [0053]    The seals for locking two ends of the housings together can be any conventional locking mechanism but should run 360° so as to lock the two housings together. 
         [0054]    The metal washers and sleeves can be hardened or soft. Hardening the metal sleeves and washers will improve the wear resistance and lower the coefficient of friction and are, thus, preferred. It should be recognized that the metal washers and sleeves can be unitary in circular dimension or can be split on the diagonal. They can be made in any conventional manner, such as, drawing or welding. 
         [0055]    Suitably, the thickness of the rigid sleeves are 0.5 to 1.50 mm. 
         [0056]    Suitably, the thickness of the rigid washers are 0.5 to 1.50 mm. 
         [0057]    Suitably, the thickness of the sliding bearing is 0.20 to 1.00 mm. 
         [0058]    As illustrated in the drawings, the metal sleeves and metal washers can be form fitted into the plastic housings so as to prevent the parts from slipping. Furthermore, gaps within the housings or annulus can be greased to aid in sealing and aiding in the bearing. In addition, it can be seen that greasing will assist in anti corrosion of the metal. 
       REFERENCE CHARACTERS 
       [0000]    
       
           10 . rod 
           10 ′. through hole 
           11 . top mount 
           12 . strut bearing 
           13 . spring coil 
           14 . spring seat 
           15 . rubber isolator 
           16 . dust Boot 
           17 . jounce bumper 
           18 . jounce bumper support cup 
           19 . sliding strut bearing 
           20 . plastic housing 
           21 . upper plastic housing 
           22 . lower plastic housing 
           23 . inner plastic sleeve 
           24 . upper plastic ledge 
           25 . outer plastic sleeve 
           26 . lower plastic ledge 
           27 . bottom seal 
           28 . top seal 
           29 . flanged, cylindrical annulus 
           30 . thrust hollow 
           31 . cylindrical hollow 
           32 . upper thrust washer 
           33 . lower thrust washer 
           34 . synthetic resin sliding thrust washer 
           35 . inner sleeve 
           36 . outer sleeve 
           37 . synthetic resin sliding sleeve 
           38 . inner flanged sleeve 
           39 . outer metal flanged sleeve 
           40 . resin flanged sleeve 
           41 . lower plastic housing 
           42 . spring seat 
           43 . integrated jounce bumper support cup 
           44 . lower plastic housing 
           45 . spring seat 
           46 . upper plastic housing 
           47 . jounce bumper support cup