Abstract:
Provided is a low height lightweight thrust slide bearing: which is capable of preventing the deformation of the ring-shaped metal plate and of reducing the generation of noise that occurs with the relative rotation of a piston rod even when a large force is applied on the metal plate via the piston rod; which is capable of preventing the intrusion of foreign matters such as dust from outside onto the sliding surfaces; and for which the number of constituent parts has been reduced. The thrust slide bearing ( 1 ) is provided with a synthetic resin bearing body ( 2 ) having a ring-shaped upper surface ( 5 ) that functions as a sliding surface, a ring-shaped metal plate ( 4 ) that is supported on the ring-shaped upper surface ( 5 ) to be freely rotatable relative to the bearing body ( 2 ) in the circumferential direction (R) around the shaft center (O), and a ring-shaped cover ( 3 ) disposed so as to cover the ring-shaped upper surface ( 5 ) and the ring-shaped metal plate ( 4 ). The ring-shaped metal plate ( 4 ) is provided with an inner disc section ( 44 ) that is formed as a unit with an outer disc section ( 43 ) and is disposed in the through hole ( 25 ) of the ring-shaped cover ( 3 ). The inner disc section ( 44 ) also functions as a reinforcing part (rib) of the outer disc section ( 44 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a thrust slide bearing, and particularly to a thrust slide bearing that is suitable for being incorporated as a slide bearing for a strut-type suspension (McPherson type) in a four-wheeled vehicle, and to a combination mechanism of the thrust slide bearing and a piston rod. 
       BACKGROUND ART 
       [0002]    Generally, a strut-type suspension used for front wheels of a four-wheeled vehicle has structure wherein a strut assembly and a coil spring are combined, the strut assembly comprises an external cylinder that is integral with a main shaft, and a hydraulic shock absorber that is accommodated in the external cylinder. As such strut-type suspensions, there is a type in which a piston rod of the strut assembly rotates when the strut assembly rotates together with the coil spring in steering operation, and a type in which a piston rod does not rotate. In both types, sometimes a thrust slide bearing of synthetic resin, instead of a rolling bearing, is used between an installation mechanism for installing a strut assembly in a vehicle body and an upper spring washer member for a coil spring, so that the strut assembly rotates smoothly. 
         [0003]    The installation mechanism for installing the strut assembly in the vehicle body uses an installation plate for supporting one end of the piston rod of the hydraulic shock absorber. However, in this type of installation mechanism, complex structure of the installation mechanism in addition to the need for the installation plate for supporting one end of the piston rod causes high cost. 
         [0004]    To cope with the problems, Patent Literature 1 proposes a thrust slide bearing in an installation mechanism for installing a strut assembly in a vehicle body, wherein the thrust slide bearing, instead of an installation plate, supports one end of a piston rod, to simplify the structure of the installation mechanism and to reduce cost. Further Patent Literature 1 proposes a combination mechanism of the thrust slide bearing and a piston rod. 
         [0005]    The thrust slide bearing described in Patent Literature 1 comprises: a ring-shaped first bearing body of synthetic resin, which has a ring-shaped upper surface and a ring-shaped engaging outer periphery; a ring-shaped second bearing body of synthetic resin, which is superimposed over the first bearing body so as to be relatively rotatable about the axis of the first bearing body, and has a ring-shaped lower surface being opposed to the ring-shaped upper surface of the first bearing body; a thrust slide bearing means, which is positioned between the ring-shaped upper surface of the first bearing body and the ring-shaped lower surface of the second bearing body and has at least one of a lower surface in slidable contact with the ring-shaped upper surface of the first bearing body, and an upper surface in slidable contact with the ring-shaped lower surface of the second bearing body; a ring-shaped top cover, which has a ring-shaped engaging inner periphery surface that engages with the ring-shaped engaging outer periphery surface of the first bearing body; and a ring-shaped metal plate, which is positioned between a ring-shaped upper surface of the second bearing body and a lower surface of the ring-shaped top cover such that a lower surface of the metal plate is in contact with the ring-shaped upper surface of the second bearing body and an upper surface of the metal plate is in contact with the lower surface of the ring-shaped top cover. In this thrust slide bearing, the ring-shaped metal plate has a ring-shaped inner periphery surface of a smaller diameter than the inner diameters of the ring-shaped inner periphery surfaces of both bearing bodies and the ring-shaped top cover, and this structure solves the above problems effectively. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent Literature 1: Japanese Unexamined Patent Application Laid-Open No. 2008-202703 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0007]    In the thrust slide bearing described in Patent Literature 1, the flat ring-shaped metal plate is fixed by a nut to a threaded portion of a piston rod. Thus, when large force is applied to the ring-shaped metal plate via the piston rod, there is a possibility that the ring-shaped metal plate is deformed, and relative rotation of the piston rod makes abnormal noise. 
         [0008]    Further, the thrust slide bearing described in Patent Literature 1 has many component parts, and this causes increase of weight. Further, the height of the slide bearing becomes higher, and thus also the height of the installation mechanism for supporting one end of the piston rod becomes higher, thus requiring a wider installation space. 
         [0009]    The present invention has been made considering the above problems. An object of the invention is to provide a low and light thrust slide bearing and a combination mechanism of the thrust slide bearing and a piston rod, wherein the thrust slide bearing can prevent deformation of a ring-shaped metal plate to reduce generation of abnormal noise, even if large force is applied to the ring-shaped metal plate via a piston rod, prevent intrusion of foreign substances from outside into sliding surfaces, and reduce the number of component parts. 
       Solution to Problem 
       [0010]    To solve the above problems, the present invention provides a thrust slide bearing, comprising: 
         [0011]    a bearing body, which is formed by resin, and has a ring-shaped upper surface functioning as a sliding surface (thrust slide bearing surface); 
         [0012]    a ring-shaped metal plate which is supported on the ring-shaped upper surface rotatably relative to the bearing body; and 
         [0013]    a ring-shaped cover which is placed to cover the ring-shaped upper surface and the ring-shaped metal plate, wherein, 
         [0014]    the bearing body comprises: 
         [0015]    a cylindrical portion which has an cylindrical inner periphery surface defining a through-hole; 
         [0016]    a ring-shaped flange portion which integrally extends outward in a radial direction from a cylindrical outer periphery surface of the cylindrical portion, to form the ring-shaped upper surface; 
         [0017]    a ring-shaped protruding portion which integrally protrudes outward in a radial direction from a lower end side of a cylindrical outer periphery surface of the ring-shaped flange portion; 
         [0018]    a cylindrical protruding portion which is integrally formed in a cylindrical shape with an upper surface of the ring-shaped protruding portion, and has a cylindrical inner periphery surface that defines a ring-shaped upward-open recessed portion that is opened upward, with a cylindrical outer periphery surface of the ring-shaped flange portion and an upper surface of the ring-shaped protruding portion; 
         [0019]    a ring-shaped engaging protruding portion which integrally protrudes inward in the radial direction from an upper end side of the cylindrical outer periphery surface of the cylindrical protruding portion, and is connected to an upper surface of the cylindrical protruding portion; and 
         [0020]    a ring-shaped convex portion which integrally protrudes outward in the radial direction from an outer circumferential edge of the ring-shaped protruding portion, 
         [0021]    the ring-shaped cover comprises: 
         [0022]    a ring-shaped disk portion which has an inner periphery surface defining a through-hole concentric with the through-hole of the bearing body and a lower surface connected to a lower edge of the inner periphery; 
         [0023]    an inner cylindrical drooping portion which is integrally formed to have a cylindrical shape with an outer periphery surface of the disk portion; 
         [0024]    a ring-shaped engaging protruding portion which protrudes outward in a radial direction from a lower end side of a cylindrical outer periphery surface of the inner cylindrical drooping portion, and engages with the engaging protruding portion of the bearing body; 
         [0025]    a ring-shaped convex portion which protrudes outward in the radial direction from an upper end side of the cylindrical outer periphery surface of the inner cylindrical drooping portion; and 
         [0026]    an outer cylindrical drooping portion which is integrally formed to have a cylindrical shape with a lower surface of the ring-shaped convex portion, extends below a lower end of the inner cylindrical drooping portion, and defines a ring-shaped downward-open recessed portion that is downward opened, with the cylindrical outer periphery surface of the inner cylindrical drooping portion and the lower surface of the ring-shaped convex portion, 
         [0027]    the ring-shaped metal plate comprises: 
         [0028]    a ring-shaped outer disk portion which comes in contact with the lower surface of the disk portion of the ring-shaped cover; and 
         [0029]    an inner disk portion which is integrally formed with the outer disk portion on an inner side of the outer disk portion in a radial direction, and is positioned in the through-hole defined by the inner periphery surface of the disk portion of the ring-shaped cover, 
         [0030]    the inner disk portion of the ring-shaped metal plate comprises: 
         [0031]    a cylindrical inner surface which defines a through-hole concentric with the through-hole of the bearing body, and has a smaller diameter than a diameter of the inner periphery surface of the cylindrical portion of the bearing body, 
         [0032]    the ring-shaped upper surface of the bearing body comprises: 
         [0033]    a ring-shaped deep groove which is formed in an inner circumferential side of the ring-shaped upper surface; and 
         [0034]    at least two recessed portions which are arranged along a circumferential direction to surround the ring-shaped deep groove, and have a depth shallower than a depth of the ring-shaped deep groove, and 
         [0035]    the ring-shaped deep groove and the at least two recessed portions are filled with a lubricant oil agent. 
         [0036]    According to the thrust slide bearing of the present invention, the ring-shaped metal plate has the inner disk portion, which is formed integrally with the outer disk portion, to be positioned in the through-hole defined by the inner periphery surface of the disk portion of the ring-shaped cover. Accordingly, the inner disk portion serves a function similar to a reinforcing portion (rib) for the outer disk portion, and as a result, deformation of the ring-shaped metal plate can be prevented even if large force is applied to the ring-shaped metal plate via a piston rod. Thereby, generation of abnormal noise due to deformation of the ring-shaped metal plate can be suppressed as far as possible, in relative rotation of the piston rod. 
         [0037]    Further, in the thrust slide bearing of the present invention, the ring-shaped deep groove which is formed in the inner circumferential side of the ring-shaped upper surface, and the at least two recessed portions which are arranged along the circumferential direction to surround the ring-shaped deep groove and have the depth shallower than the depth of the ring-shaped deep groove, are provided on the ring-shaped upper surface functioning as the sliding surface of the bearing body. These ring-shaped deep groove and the recessed portions are filled with the lubricant oil agent. As a result, the ring-shaped metal plate is directly supported on the ring shaped upper surface rotatably relative to the bearing body in the circumferential direction about the axis of the bearing body. Accordingly, the height of the thrust slide bearing itself can be lowered, the installation space of the thrust slide bearing can be reduced, and the number of the component parts can be reduced, to realize weight reduction and cost reduction of the thrust slide bearing as a whole. 
         [0038]    Further, in the thrust slide bearing of the present invention, a first intrusion prevention means for preventing intrusion of foreign substances such as grit and dust from the outer periphery surface side of the thrust slide bearing onto the ring-shaped upper surface functioning as the sliding surface of the bearing body is formed by the outer periphery surface of the cylindrical protruding portion of the bearing body, the outer cylindrical drooping port on of the ring-shaped cover which surrounds the outer periphery surface, and the ring-shaped convex portion which integrally protrudes outward in the radial direction from the outer circumferential edge of the ring-shaped protruding portion of the bearing body so as to close the ring-shaped gap formed in the radial direction between the outer periphery surface and the outer cylindrical drooping portion. Further, a second intrusion prevention means for preventing intrusion of foreign substances such as grit and dust from the outer periphery surface side of the thrust slide bearing onto the ring-shaped upper surface functioning as the sliding surface of the bearing body is formed by the upward-open recessed portion of the ring-shaped protruding portion of the bearing body and the outer cylindrical drooping portion which is inserted into the upward-open recessed portion so that the engaging protruding portion of the ring-shaped cover is elastically fitted to the engaging protruding portion of the bearing body. Therefore, intrusion of foreign substances such as grit and dust onto the sliding surface of the thrust slide bearing can be prevented as far as possible, and rotation of the ring-shaped metal plate about the axis of the bearing body relative to the bearing body can be performed smoothly. 
         [0039]    In the thrust slide bearing of the present invention, it is favorable that the bearing body is formed of thermoplastic resin such as polyacetal resin, polyamide resin, polyester resin, or the like. Further, in a favorable example, the ring-shaped cover is formed of thermoplastic resin such as polyacetal resin, polyamide resin, polyester resin, or the like. Instead of this, however, the ring-shaped cover may be formed of reinforced thermoplastic synthetic resin, which is thermoplastic synthetic resin reinforced by inorganic reinforcing material such as glass fiber, glass power, glass beads, carbon fiber, and the like or organic reinforcing material such as aramid resin fiber. Further, in a favorable example, the ring-shaped metal plate is formed of steel plate of steel, stainless steel, or the like. Instead of this, however, the ring-shaped metal plate may be formed of non-ferrous metal such as copper alloy, titanium alloy, or the like. Favorably, such ring-shaped metal plate is formed by press forming of automotive workable hot-rolled high tensile steel sheet (SPFH: JISG3134) (hereinafter, shortly referred to as hot-rolled high tensile steel sheet (SPFH)). 
         [0040]    Further, in the thrust slide bearing of the present invention, the at least two recessed portions provided in the ring-shaped upper surface of the bearing body may be an inner ring-shaped shallow groove and an outer ring-shaped shallow groove, which are arranged in two lines, namely, an inner line and an outer line, along the circumferential direction so as to surround doubly the ring-shaped deep groove that is formed in the inner circumferential side of the ring-shaped upper surface. Here, the inner and outer ring-shaped shallow grooves have the depth shallower than that of the ring-shaped deep groove. Or, the at least two recessed portions may be a plurality of inner recessed portions and a plurality of outer recessed portions, which are arranged in two lines, namely, an inner line and an outer line, along the circumferential direction so as to surround the ring-shaped deep groove formed in the inner circumferential side of the ring-shaped upper surface. These recessed portions have the depth shallower than that of the ring-shaped deep groove. Here, the inner recessed portions and the outer recessed portions may be arranged to have phase difference in the circumferential direction from each other. 
         [0041]    Here, the area ratio of the opening spaces of the opening spaces of the inner ring-shaped shallow groove and the outer ring-shaped shallow groove, which are formed in the ring-shaped upper surface and arranged in the two lines, namely, the inner line and the outer line, or the opening spaces of the plurality of inner recessed portions and the plurality of outer recessed portions, which are arranged in the two lines, namely, the inner line and the outer line, to the ring-shaped upper surface of the bearing body is 20-50%, and favorably 30-40%. 
         [0042]    In detail, to make the lubricant oil agent exert its low frictional properties successfully in the inner ring-shaped shallow groove and the outer ring-shaped shallow groove or the plurality of inner recessed portions and the plurality of outer recessed portions, which are filled with the lubricant agent such as grease, it is favorable that the area ratio of the opening spaces of the inner ring-shaped shallow groove and the outer ring-shaped shallow groove or the plurality of inner recessed portions and the plurality of outer recessed portions to the ring-shaped upper surface of the bearing body is at least 20%. If, however, the area ratio exceeds 50%, it result in deterioration of strength of the thrust slide bearing surface, and plastic deformation such as creep is likely to occur. 
         [0043]    Further, in the thrust slide bearing of the present invention, electrodeposition coating may be applied to the ring-shaped lower surface of the outer disk portion of the ring-shaped metal plate. Further, in the ring-shaped metal plate, it is favorable that at least one of the upper surface or the lower surface of the inner disk portion is coated with malleable soft metal such as zinc, copper, tin, or the like. 
         [0044]    In the thrust slide bearing of the present invention, at least one of the lubricant oil agent and the electrodeposition coating is positioned between the ring-shaped lower surface of the outer disk portion of the ring-shaped metal plate and the ring-shaped upper surface of the bearing body, and accordingly the ring-shaped upper surface of the bearing body is rotatable relative to the ring-shaped lower surface of the outer disk portion of the ring-shaped metal plate about the axis of the bearing body via at least one of the lubricant oil agent and the electrodeposition coating. As a result, in the thrust slide bearing, the ring-shaped metal plate can smoothly rotate relative to the bearing body in the circumferential direction about the axis of the bearing body. 
         [0045]    Further, in the thrust slide bearing of the present invention, the ring-shaped metal plate may have an inclined connecting portion that lies between the outer disk portion and the inner disk portion and extends obliquely upward from the inner periphery surface side of the outer disk portion, so as to be connected to the inner disk portion. 
         [0046]    Further, in a favorable example of the thrust slide bearing of the present invention, the ring-shaped cover has a convex spheroidal outer periphery surface extending from the upper surface of the ring-shaped disk portion through the outer periphery surface of the ring-shaped convex portion to the outer periphery surface of the outer cylindrical drooping portion. Further, the outer periphery surface of the outer disk portion of the ring-shaped metal plate in contact with the lower surface of the disk portion of the ring-shaped cover is slidably in contact with the inner periphery surface of the inner cylindrical drooping portion that is connected to the lower surface of the disk portion of the ring-shaped cover. 
         [0047]    Further, the present invention provides a combination mechanism of a thrust slide bearing and a piston rod, for example, for use in a strut-type suspension in a four-wheeled vehicle, wherein, 
         [0048]    the combination mechanism comprises: the thrust slide bearing of one of the above-described modes; and a piston rod of a shock absorber, 
         [0049]    the piston rod comprises: 
         [0050]    a large-diameter portion which is positioned in the through-hole defined by the inner periphery surface of the cylindrical portion of the bearing body; 
         [0051]    a small-diameter portion which is formed integrally with the large-diameter portion so as to have a smaller diameter than a diameter of the large-diameter portion, and is positioned in the through-hole defined by the cylindrical inner surface of the inner disk portion of the ring-shaped metal plate; and 
         [0052]    a threaded portion which is threaded in the small-diameter portion, and 
         [0053]    the ring-shaped metal plate is held between a ring-shaped step surface, which is formed between the large-diameter portion and the small-diameter portion of the piston rod, and a seating surface of a nut screwed onto the threaded portion. 
         [0054]    Here, at least in the inner disk portion of the ring-shaped metal plate, it is favorable that at least of the upper surface and the lower surface held between the ring-shaped step surface of the piston rod and the seating surface of the nut is coated with malleable soft metal such as zinc, copper, tin, and the like. Thereby, at least one set of surfaces, i.e. either a set of the ring-shaped step surface and the lower surface of the inner disk portion, or a set of the seating surface of the nut and the upper surface of the inner disk portion comes in almost whole surface contact with each other, and local contact can be avoided. Accordingly, stress from the piston rod under load in the axial direction can be distributed. Asa result, it is possible to prevent generation of damage such as cracking in the inner disk portion. 
       Advantageous Effects of Invention 
       [0055]    The present invention can provide a light-weight thrust slide bearing and a combination mechanism of the thrust slide bearing and a piston rod, wherein: even if large force is applied to the ring-shaped metal plate via the piston rod, deformation of the ring-shaped metal plate can be prevented; and generation of abnormal noise can be reduced in relative rotation of the piston rod; and in addition, intrusion of foreign substances such as grit and dust onto the ring-shaped upper surface functioning as the sliding surface of the bearing body can be prevented as far as possible; the number of the component parts can be reduced; and the height of the thrust slide bearing and the combination mechanism can be reduced. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0056]      FIGS. 1(A) ,  1 (B), and  1 (C) are a perspective view, a top view, and a bottom view of a thrust slide bearing  1  according to one embodiment of the present invention, and  FIG. 1(D)  is an A-A cross-section view of the thrust slide bearing  1  shown in  FIG. 1(B) ; 
           [0057]      FIG. 2(A)  is a top view of a bearing body  2 ,  FIG. 2(B)  is a B-B cross-section view of the bearing body  2  shown in  FIG. 2(A) ,  FIG. 2(C)  is a bottom view of the bearing body  2 , and  FIG. 2(D)  is an enlarged view of the part C of  FIG. 2(B) ; 
           [0058]      FIG. 3(A)  is a top view of a ring-shaped cover  3 ,  FIG. 3(B)  is a D-D cross-section view of the ring-shaped cover  3  shown in  FIG. 3(A) ,  FIG. 3(C)  is a bottom view of the ring-shaped cover  3 , and  FIG. 3(D)  is an enlarged view of the part E of  FIG. 3(B) ; 
           [0059]      FIG. 4(A)  is a top view showing a ring-shaped metal plate  4 ,  FIG. 4(B)  is an F-F cross-section view of the ring-shaped metal plate  4  shown in  FIG. 4(A) , and  FIG. 4(C)  is an enlarged view of the part G of  FIG. 4(B) ; 
           [0060]      FIG. 5  is a cross-section view for explaining an example where the thrust slide bearing  1  of one embodiment of the present invention is used in a strut-type suspension; and 
           [0061]      FIG. 6(A)  is a top view of a bearing body  2 A as a variant of the bearing body  2 ,  FIG. 6(B)  is an enlarged view of the part H of the bearing body  2 A shown in  FIG. 6(A) , and  FIGS. 6(C) and 6(D)  are an I-I cross-section view and an J-J cross-section view of the bearing body  2 A shown in  FIG. 6(A) . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0062]    In the following, an embodiment of the present invention will be described referring to the drawings. The present invention is not limited to the embodiment described below, and can be changed variously within the scope of the invention. 
         [0063]      FIGS. 1(A) ,  1 (B), and  1 (C) are a perspective view, a top view, and a bottom view showing a thrust slide bearing  1  of an embodiment of the present invention, and  FIG. 1(D)  is an A-A cross-section of the thrust slide bearing  1  shown in  FIG. 1(B) . 
         [0064]    As shown in the figures, the thrust slide bearing  1  of the present embodiment comprises: a bearing body  2  of synthetic resin which has a ring-shaped upper surface  5  functioning as a sliding surface (thrust slide bearing surface); a ring-shaped metal plate  4  which is placed on the ring-shaped upper surface  5  of the bearing body  2 ; and a ring-shaped cover  3  which is placed to cover the ring-shaped upper surface  5  of the bearing body  2  and the ring-shaped metal plate  4 . The ring-shaped metal plate  4  is supported rotatably relative to the bearing body  2  in the circumferential direction R about the axis O of the bearing body  2 . 
         [0065]    The bearing body  2  is made of thermoplastic synthetic resin such as polyacetal resin, polyamide resin, polybutylene terephthalate resin, and the like. 
         [0066]      FIG. 2(A)  is a top view of the bearing body  2 ,  FIG. 2(B)  is a B-B cross-section view of the bearing body  2  shown in  FIG. 2(A) ,  FIG. 2(C)  is a bottom view of the bearing body  2 , and  FIG. 2(D)  is an enlarged view of the part C of  FIG. 2(B) . 
         [0067]    As shown in the figures, the bearing body  2  comprises: a cylindrical portion  8  which has a cylindrical inner periphery surface  7  defining a through-hole  6 ; a ring-shaped flange portion  10  which integrally extends outward in the radial direction from a cylindrical outer periphery surface  9  of the cylindrical portion  8 , and forms a ring-shaped upper surface  5  in combination with the cylindrical portion  8 ; a ring-shaped protruding portion  12  which integrally protrudes outward in the radial direction from the lower end side of a cylindrical outer periphery surface  11  of the ring-shaped flange portion  10 ; a cylindrical protruding portion  17  which is integrally formed in a cylindrical shape with a ring-shaped upper surface  13  of the ring-shaped protruding portion  12 , and defines a ring-shaped upward-open recessed portion  16  opened upward in combination with the cylindrical outer periphery surface  11  of the ring-shaped flange portion  10  and the upper surface  13  of the ring-shaped protruding portion  12 ; a ring-shaped engaging protruding portion  18  which integrally protrudes inward in the radial direction from the upper end side of the cylindrical inner periphery surface  14  of the cylindrical protruding portion  17 , and is connected to the ring-shaped upper surface  15  of the cylindrical protruding portion  17 ; and a ring-shaped convex portion  19  which integrally protrudes outward in the radial direction from the outer circumferential edge of the ring-shaped protruding portion  12 . 
         [0068]    The cylindrical portion  8  of the bearing body  2  has a ring-shaped lower surface  20  as well as the inner periphery surface  7  and the outer periphery surface  9 . In a ring-shaped lower surface  21  of the ring-shaped flange portion  10  positioned above this lower surface  20  and in an lower surface  22  (which is flush with the lower surface  21 ) of the ring-shaped protruding portion  12 , there are formed a plurality of recessed portions  23  arranged in the circumferential direction R separately from one another and a plurality of recessed portions  24  that are adjacent to the recessed portions  23  in the radial direction and deeper than the recessed portions  23 . 
         [0069]    The ring-shaped upper surface  5  of the bearing body  2  has a ring-shaped deep groove  60  which is formed in the inner circumferential side of the ring-shaped upper surface  5 , and a plurality of recessed portions which surround multiply the ring-shaped deep groove  60 . In the present embodiment, as the plurality of recessed portions that surround multiply the ring-shaped deep groove  60 , there are formed an inner ring-shaped shallow groove  61  and an outer ring-shaped shallow groove  62  which have the same depth shallower than that of the ring-shaped deep groove  60  and are arranged in two lines, namely, an inner line and an outer line, along the circumferential direction R to surround the ring-shaped deep groove  60  doubly. The ring-shaped deep groove  60 , the inner ring-shaped shallow groove  61 , and the outer ring-shaped shallow groove  62  are filled with a lubricant oil agent G such as grease. 
         [0070]    The ring-shaped cover  3  is formed of: thermoplastic synthetic resin such as polyacetal resin, polyamide resin, polybutylene terephthalate resin, and the like; or reinforced thermoplastic synthetic resin, namely, the above-mentioned thermoplastic synthetic resin which is reinforced by inorganic filler such as glass fiber, glass powder, glass beads, carbon fiber, and the like, or by organic filler such as aramid resin fiber. 
         [0071]      FIG. 3(A)  is a top view of the ring-shaped cover  3 ,  FIG. 3(B)  is a D-D cross-section view of the ring-shaped cover  3  shown in  FIG. 3(A) ,  FIG. 3(C)  is a bottom view of the ring-shaped cover  3 , and  FIG. 3(D)  is an enlarged view of the part E of  FIG. 3(B) . 
         [0072]    As shown in the figures, the ring-shaped cover  3  has: an inner periphery surface  26  which defines a through-hole  25  concentric with the through-hole  6  of the bearing body  2 ; a truncated conical surface  50  which is connected to the lower edge of the inner periphery  26 ; a ring-shaped disk portion  28  which has a lower surface  27  connected to a lower edge of the truncated conical surface  50 ; an inner cylindrical drooping portion  32  which is integrally formed to have a cylindrical shape with the outer circumferential edge of the disk portion  28 ; a ring-shaped engaging protruding portion  31  which protrudes outward in the radial direction from the lower end side of the cylindrical outer periphery surface  30  of the inner cylindrical drooping portion  32 , and engage s with the engaging protruding portion  18  of the bearing body  2 ; a ring-shaped convex portion  33  which protrudes outward in the radial direction from the upper end side of the cylindrical outer periphery surface  30  of the inner cylindrical drooping portion  32 ; and an outer cylindrical drooping portion  39  which is integrally formed to have a cylindrical shape with the lower surface  34  of the ring-shaped convex portion  33 , extends below the lower end  38  of the inner cylindrical drooping portion  32 , and defines a ring-shaped downward-open recessed portion  36  opened downward in combination with the cylindrical outer periphery  30  of the inner cylindrical drooping portion  32  and the lower surface  34  of the ring-shaped convex portion  33 . 
         [0073]    Further, the ring-shaped cover  3  has an upper surface  40  that spreads from the upper surface of the ring-shaped disk portion  28  through the outer periphery surface of the ring-shaped convex portion  33  and the outer periphery surface of the outer cylindrical drooping portion  39 . 
         [0074]    The ring-shaped metal plate  4  is formed of a steel plate of steel or stainless steel and the like, or non-ferrous metal such as copper alloy, titanium alloy, and the like. Favorably, the ring-shaped metal plate  4  is formed by press forming of hot-rolled high tensile steel sheet (SPFH). 
         [0075]      FIG. 4(A)  is a top view of the ring-shaped metal plate  4 ,  FIG. 4(B)  is an F-F cross-section view of the ring-shaped metal plate  4  shown in  FIG. 4(A) , and  FIG. 4(C)  is an enlarged view of the part G of  FIG. 4(B) . 
         [0076]    As shown in the figures, the ring-shaped metal plate  4  comprises: a ring-shaped outer disk portion  43  which comes in contact with the lower surface  27  of the disk portion  28  of the ring-shaped cover  3 ; and an inner disk portion  44  which is integrally formed with the outer disk portion  43  on the inner side in the radial direction, so as to be positioned in the through-hole  25  defined by the inner periphery surface  26  of the disk portion  28  of the ring-shaped cover  3 . Further, in addition to the outer disk portion  43  and the inner disk portion  44 , the ring-shaped metal plate  4  has an inclined connecting portion  45  which lies between the outer disk portion  43  and the inner disk portion  44  and extends obliquely upward from the inner periphery surface side of the outer disk portion  43 , so as to be connected to the inner disk portion  44 . 
         [0077]    As shown in  FIG. 1(D) , in the axial direction O, the outer disk portion  43  of the ring-shaped metal plate  4  is disposed between the cylindrical portion  8  and the ring-shaped flange portion  10  of the bearing body  2  and the disk portion  28  of the ring-shaped cover  3 . Further, the outer disk portion  43  comprises: a ring-shaped upper surface  46 ; a ring-shaped lower surface  47  which is opposed to the ring-shaped upper surface  5  functioning as the sliding surface of the bearing body  2 ; and a cylindrical outer periphery  49  which is opposed to the inner periphery  48  of the inner cylindrical drooping portion  32  of the ring-shaped cover  3 . 
         [0078]    The inclined connecting portion  45  of the ring-shaped metal plate  4  comprises: an inclined outer periphery surface  51  which is opposed to the truncated conical surface  50  of the ring-shaped cover  3  in the radial direction; and an inclined inner periphery surface  52  which extends approximately parallel to the inclined outer periphery surface  51 . 
         [0079]    The inner disk portion  44  of the ring-shaped metal plate  4  comprises: a ring-shaped upper surface  53  which is connected to the upper edge of the inclined outer periphery surface  51  and exposed upward from the through-hole  25  defined by the inner periphery surface  26  of the disk portion  28  of the ring-shaped cover  3 ; a ring-shaped lower surface  54  which extends almost in parallel with the upper surface  53 ; and a cylindrical inner surface  56  which defines a through-hole  55  that is concentric with the through-hole  6  of the bearing body  2  and the through-hole  25  of the ring-shaped cover  3 , and has a smaller diameter than that of the inner periphery surface  7  of the cylindrical portion  8  of the bearing body  2 . 
         [0080]    As described above, it is favorable that the ring-shaped metal plate  4  is formed by press forming of hot-rolled high tensile steel sheet (SPFH). In that case, as described below referring to  FIG. 5 , it is favorable that at least one (sandwiched surface) of the ring-shaped upper surface  53  and the ring-shaped lower surface  54  of the inner disk portion  44  held between a ring-shaped step surface  76  and a seating surface (lower surface)  78  of a nut  77  is coated with malleable soft metal such as zinc, copper, tin, and the like. The ring-shaped step surface  76  is formed between a large-diameter portion  73  and a small-diameter portion  74  of the piston rod  63 . By applying such metal plating, at least one set of surfaces, namely, either a set of the ring-shaped step surface  76  and the lower surface  54  of the inner disk portion  44  or a set of the seating surface  78  of the nut  77  and the upper surface  53  of the inner disk portion  44  comes in almost whole surface contact with each other, and local contact can be avoided. Accordingly, stress from the piston rod  63  under load in the axial direction can be distributed. As a result, it is possible to prevent generation of damage such as cracking in the inner disk portion  44  and the outer disk portion  43  formed integrally with the inner disk portion  44 . 
         [0081]    As described above, in the thrust slide bearing  1  of the above configuration, the ring-shaped upper surface  5  of the bearing body  2  comprises: the ring-shaped deep groove  60  formed in the inner circumferential side of the ring-shaped upper surface  5 ; and the inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62  which are arranged in two lines, namely, the inner line and the outer line, along the circumferential direction R so as to surround the ring-shaped deep groove  60  doubly, and have the same depth shallower than that of the ring-shaped deep groove  60 . The ring-shaped deep groove  60 , the inner ring-shaped shallow groove  61 , and the outer ring-shaped shallow groove  62  are filled with the lubricant oil agent G such as grease. The lubricant oil agent G with which the ring-shaped deep groove  60 , the inner ring-shaped shallow groove  61 , and the outer ring-shaped shallow groove  62  are filled, is spread on the ring-shaped upper surface  5  so as to intervene between the ring-shaped upper surface  5  and the ring-shaped lower surface  47  of the ring-shaped metal plate  4  opposed to the ring-shaped upper surface  5 . By this, the ring-shaped upper surface  5  of the bearing body  2  comes in smooth contact with the ring-shaped lower surface  47  of the ring-shaped metal plate  4  rotatably in the circumferential direction R about the axis O relative to the ring-shaped lower surface  47 . Thus the ring-shaped upper surface  5  functions as the sliding surface (thrust slide bearing surface). 
         [0082]    Here, the area ratio of the opening spaces of the inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62 , to the ring-shaped upper surface  5  of the bearing body  2  is 20-50% and favorably 30-40%. The inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62  are formed in the ring-shaped upper surface  5  of the bearing body  2  and arranged in two lines, namely, the inner line and the outer line. In detail, to make the lubricant oil agent G exert its low frictional properties successfully in the inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62  filled with the lubricant oil agent G such as grease, it is favorable that the area ratio of the inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62  to the ring-shaped upper surface  5  of the bearing body  2  is at least 20%. If, however, the area ratio exceeds 50%, it results in deterioration of strength of the thrust slide bearing surface, and plastic deformation such as creep is likely to occur. The example shown in  FIG. 2(A)  is formed to have the ratio 30%. 
         [0083]    In the thrust slide bearing  1  of the above configuration, the inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62  are formed in the ring-shaped upper surface  5  of the bearing body  2  which functions as the sliding surface (thrust slide bearing surface). And therefore, the contact area between the ring-shaped upper surface  5  of the bearing body  2  and the ring-shaped lower surface  47  of the outer disk portion  43  of the ring-shaped metal plate  4  is reduced in relative rotation between the ring-shaped upper surface  5  of the bearing body  2  and the counterpart member, namely, the ring-shaped lower surface  47  of the outer disk portion  43  of the ring-shaped metal plate  4  in the circumferential direction R about the axis O. So, the contact pressure (load per unit of area) applied on the ring-shaped upper surface  5  of the bearing body  2  can be raised. This, coupled with the reduced friction due to spreading of the lubricant oil agent G (with which the inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62  are filled) on the ring-shaped upper surface  5 , can realize further reduction of friction. 
         [0084]    According to the thrust slide bearing  1  of the present embodiment, the engaging protruding portion  31  of the ring-shaped cover  3  is elastically fitted (snap-fit) to the engaging protruding portion  18  of the bearing body  2  owing to the flexibility of the synthetic resin. By this, the bearing body  2  and the ring-shaped cover  3  are connected with each other by being superposed via the ring-shaped metal plate  4 . In rotation of the bearing body  2  relative to the ring-shaped metal plate  4  in the circumferential direction R about the axis O, there arises sliding in the circumferential direction R between the ring-shaped upper surface  5  of the bearing body  2  and the ring-shaped lower surface  47  of the ring-shaped outer disk portion  43  of the ring-shaped metal plate  4 , the ring-shaped lower surface  47  opposed to the ring-shaped upper surface  5  via the lubricant G. Thus, relative rotation in the circumferential direction R between the bearing body  2  and the ring-shaped metal plate  4  can be realized under lower friction torque. 
         [0085]    Further, in the thrust slide bearing  1  of the present embodiment, a first intrusion prevention means for preventing intrusion of foreign substances such as grit and dust from the outer periphery surface side of the thrust slide bearing  1  onto the ring-shaped upper surface  5  of the bearing body  2  is formed by the outer periphery surface  171  of the cylindrical protruding portion  17  of the bearing body  2 , the outer cylindrical drooping portion  39  of the ring-shaped cover  3  which surrounds the outer periphery surface  171 , and the ring-shaped convex portion  19  which integrally protrudes outward in the radial direction from the outer circumferential edge of the ring-shaped protruding portion  12  of the bearing body  2  so as to close the ring-shaped gap formed in the radial direction between the outer periphery surface  171  and the outer cylindrical drooping portion  39 . Further, a second intrusion prevention means for preventing intrusion of foreign substances such as grit and dust from the outer periphery surface side of the thrust slide bearing  1  onto the ring-shaped upper surface  5  of the bearing body  2  is formed by the upward-open recessed portion  16  of the ring-shaped protruding portion  12  of the bearing body  2  and the outer cylindrical drooping portion  39  which is inserted into the upward-open recessed portion  16  so that the engaging protruding portion  31  of the ring-shaped cover  3  is elastically fitted to the engaging protruding portion  18  of the bearing body  2 . Therefore, intrusion of foreign substances such as grit and dust onto the ring-shaped upper surface  5  functioning as the sliding surface of the bearing body  2  can be prevented as far as possible, and rotation of the ring-shaped metal plate  4  about the axis O relative to the bearing body  2  can be performed smoothly. 
         [0086]    Next, a combination mechanism of the thrust slide bearing  1  of the present embodiment and a piston rod will be described. 
         [0087]      FIG. 5  is a cross-section view for explaining an example where the thrust slide bearing  1  of one embodiment of the present invention is used in a strut-type suspension. 
         [0088]    As shown in the figure, the thrust slide bearing  1  of the present embodiment is mounted in a strut-type suspension  65  of a vehicle, such as a four-wheeled vehicle. The strut-type suspension  65  comprise a hydraulic shock absorber (not shown) having a piston rod  63 , and a coil spring  64  placed to surround the shock absorber. The strut-type suspension  65  mounted with the thrust slide bearing  1  is attached in a vehicle body (not shown) via an installation mechanism  66 . 
         [0089]    The strut-type suspension  65  comprises: the hydraulic shock absorber; the coil spring  64 ; and further, an upper spring seat member  67  for receiving one end of the coil spring  64 ; and a bump stopper  68  placed to surround the piston rod  63 . 
         [0090]    The installation mechanism  66  comprises: an elastic member  70  such as rubber in which a core metal  69  is embedded; and a spacer member  71 , which is placed between the upper spring seat member  67  of the strut-type suspension  65  and the lower surface  21  of the ring-shaped flange portion  10  of the bearing body  2  and the lower surface  22  of the cylindrical protruding portion  17  of the bearing body  2 . 
         [0091]    The thrust slide bearing  1  is placed between the elastic member  70  of the installation mechanism  66  and the upper spring seat member  67  of the strut-type suspension  65  via the spacer member  71 . Further, the thrust slide bearing  1  is positioned by the upper spring seat member  67  with respect to the orthogonal direction to the axis O, namely, the radial direction, when the lower end portion of the cylindrical portion  8  of the bearing body  2  is inserted into a through-hole  72  formed in the center of the upper spring seat member  67 . 
         [0092]    The inner periphery  711  of the spacer member  71  is in contact with the outer periphery  9  of the cylindrical portion  8  of the bearing body  2 . 
         [0093]    The elastic member  70  surrounding the thrust slide bearing  1  is positioned to be in contact with a convex spheroidal outer periphery surface  42  of the ring-shaped cover  3  at the inner periphery surface  701  of the elastic member  70 . 
         [0094]    The piston rod  63  comprises: the large-diameter portion  73  positioned to pass through the through-hole  6  of the bearing body  2 ; the small-diameter portion  74  which is integrally formed with the large-diameter portion  73  and is positioned to pass through the through-hole  55  of the ring-shaped metal plate  4 ; and a threaded portion  75  threaded in the small-diameter portion  74 . 
         [0095]    At the outer periphery surface  79  of the large-diameter portion  73  of the piston rod  63 , the large-diameter portion  73  is in contact with the inner periphery surface  7  of the cylindrical portion  8  defining the through-hole  6  of the bearing body  2  of the thrust slide bearing  1 , rotatably in the circumferential direction R. 
         [0096]    Onto the threaded portion  75  of the piston rod  63 , the nut  77  is screwed. The nut  77  is in contact with the ring-shaped inner periphery surface  80  of the elastic member  70  at the outer periphery surface of the nut  77 , so that the nut  77  screwed onto the threaded portion  75  is fixed to the piston rod  63 , not to rotate in the circumferential direction R relative to the elastic member  70 . 
         [0097]    At the inner disk portion  44 , the ring-shaped metal plate  4  is held between the ring-shaped step surface  76  which is formed between the large-diameter portion  73  and the small-diameter portion  74  of the piston rod  63 , and the seating surface  78  of the nut  77  screwed onto the threaded portion  75 . 
         [0098]    The ring-shaped cover  3  is held by the elastic member  70 , not to rotate in the circumferential direction R relative to the piston rod  63 , via the ring-shaped metal plate  4  held at the inner disk portion  44  between the ring-shaped step surface  76  of the piston rod  63  and the seating surface  78  of the nut  77 . 
         [0099]    In the above-described combination mechanism of the thrust slide bearing  1  and the piston rod  63 , when the coil spring  64  rotates in the circumferential direction R about the axis O by steering operation, the bearing body  2  rotates in the circumferential direction R relative to the ring-shaped metal plate  4 , similarly to the coil spring  64 . This rotation of the bearing body  2  is done smoothly because the lubricant oil agent G such as grease, with which the ring-shaped deep groove  60 , the inner ring-shaped shallow groove  61 , and the outer ring-shaped shallow groove  62  of the bearing body  2  are filled, is spread on the ring-shaped upper surface  5  functioning as the sliding surface, and the ring-shaped upper surface  5  and the ring-shaped lower surface  47 , which is opposed to the ring-shaped upper surface  5 , of the outer disk portion  43  of the ring-shaped metal plate  4 , are slidably in contact with each other in the circumferential direction in the state that the lubricant oil agent G interposes. Accordingly, also the steering operation is performed without resistance. 
         [0100]    In the thrust slide bearing  1  of the present embodiment, the ring-shaped metal plate  4  is supported rotatably in the circumferential direction R relative to the bearing body  2  by the ring-shaped upper surface  5  functioning as the sliding surface of the bearing body  2  and the lubricant oil agent G spread on the ring-shaped upper surface  5 . Therefore, the thrust slide bearing  1  can be made up by three parts, namely, the bearing body  2 , the ring-shaped metal plate  4 , and the ring-shaped cover  3 . As a result, the height of the thrust slide bearing  1  itself can be lowered, and the installation space of the thrust slide bearing  1  can be reduced, and the number of the component parts can be reduced, realizing reduction in weight and cost of the thrust slide bearing  1  as a whole. Further, since the ring-shaped metal plate  4  supports one end of the piston rod  63 , it is possible to omit an installation member for supporting the one end of the piston rod  63  in the installation mechanism  66  for installing the strut-type suspension  65  in the vehicle body. Accordingly, the installation mechanism  66  can be simplified, to realize cost reduction. 
         [0101]    Further, according to the thrust slide bearing  1  of the present embodiment, the ring-shaped metal plate  4  is integrally formed with the outer disk portion  43  via the inclined connecting portion  45 , and has the inner disk portion  44  that is positioned in the through-hole  25  defined by the inner periphery surface  26  of the disk portion  28  of the ring-shaped cover  3 . This inner disk portion  44  serves the same work to a reinforcing portion (rib) for the outer disk portion  43 , and as a result, deformation of the ring-shaped metal plate  4  can be prevented even if large force is applied to the ring-shaped metal plate  4  via the piston rod  63 . Thus, generation of abnormal noise due to deformation of the ring-shaped metal plate  4  can be suppressed as far as possible, in relative rotation of the piston rod  63 . 
         [0102]    In the thrust slide bearing  1  of the present embodiment, it is favorable that at least one of the upper surface  53  and the lower surface  54  of the inner disk portion of the ring-shaped metal plate  4  held between the ring-shaped step surface  76  formed between the large-diameter portion  73  and the small-diameter portion  74  of the piston rod  63  is coated with malleable soft metal such as zinc, copper, tin, or the like. By such coating, at least one set of surface, namely, either a set of the ring-shaped step surface  76  and the lower surface  54  of the inner disk portion  44  or a set of the seating surface  78  of the nut  77  and the upper surface  53  of the inner disk portion  44  comes in almost whole surface contact with each other, and local contact can be avoided. Accordingly, stress from the piston rod  63  under load in the axial direction can be distributed. As a result, it is possible to prevent generation of damage such as cracking in the inner disk portion  44 . 
         [0103]    Further, in the thrust slide bearing  1  of the present embodiment, electrodeposition coating may be applied to the ring-shaped lower surface  47  of the outer disk portion  43  of the ring-shaped metal plate  4 . Favorably, such electrodeposition coating is performed as cationic electrodeposition coating of plastic paint such as epoxy resin, amino-alkyd resin, acrylic resin, or the like. 
         [0104]    The inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62  are formed in the ring-shaped upper surface  5  of the bearing body  2  functioning as the sliding surface, and the electrodeposition coating is applied to the ring-shaped lower surface  47 , which faces the ring-shaped upper surface  5  of the bearing body  2 , of the outer disk portion  43  of the ring-shaped metal plate  4 . Thus, it is possible to reduce the contact area between the ring-shaped upper surface  5  of the bearing body  2  and the ring-shaped lower surface  47  of the outer disk portion  43  of the counterpart member, namely, the ring-shaped metal plate  4  at relative rotation of the ring-shaped metal plate  4  and the bearing body  2  in the circumferential direction R about the axis O, and to raise the contact pressure (load per unit of area) applied on the ring-shaped upper surface  5  of the bearing body  2 . This can realize further reduction of friction, in addition to the reduction of friction owing to the friction reduction between resins, namely, the electrodeposition coatings applied on the ring-shaped upper surface  5  of the bearing body  2  of synthetic resin and on the ring-shaped lower surface  47  of the outer disk portion  43  of the ring-shaped metal plate  4  and reduction of friction owing to spreading of the lubricant oil agent G, with which the inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62  are filled, over the ring-shaped upper surface  5 . 
         [0105]    Further, in the thrust slide bearing  1  of the above embodiment, the inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62  are formed in the ring-shaped upper surface  5  functioning as the sliding surface of the bearing body  2 . The inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62  have the same depth shallower than that of the ring-shaped deep groove  60  and are arranged in two lines of the inner line and the outer line along the circumferential direction R to surround doubly the ring-shaped deep groove  60 . The inner ring-shaped shallow groove  61 , the outer ring-shaped shallow groove  62 , and the ring-shaped deep groove  60  are filled with the lubricant oil agent G such as grease. However, the present invention is not limited to this. It is sufficient that at least two recessed portions having the depth shallower than that of the ring-shaped deep groove  60  are formed in lines along the circumferential direction R in the ring-shaped upper surface  5  of the bearing body  2 , so as to surround the ring-shaped deep groove  60 , and these recessed portions and the ring-shaped deep groove  60  are filled with the lubricant oil agent R. For example, three or more shallow grooves may be formed to surround the ring-shaped deep groove  60  in the ring-shaped upper surface  5  functioning as the sliding surface of the bearing body  2 . Or, the pattern of the recessed portions surrounding the ring-shaped deep groove  60  does not need to be a continuous ring shape along the circumferential direction of the ring-shaped upper surface  5 . As shown in the following, these recessed portions can be discontinuous recessed portion arranged along the circumferential direction of the ring-shaped upper surface  5 . 
         [0106]      FIG. 6(A)  is a top view of a bearing body  2 A as a variant of the bearing body  2 ,  FIG. 6(B)  is an enlarged view of the part H of the bearing body  2 A shown in  FIG. 6(A) , and  FIGS. 6(C) and 6(D)  are an I-I cross-section view and an J-J cross-section view of the bearing body  2 A shown in  FIG. 6(A) . In  FIG. 6 , components having the same functions as in the bearing body  2  shown in  FIG. 2  are attached with the same signs. 
         [0107]    As shown in  FIG. 6 , the bearing body  2 A is different from the bearing body  2  shown in  FIG. 2  in that a plurality of inner recessed portions  81  and a plurality of outer recessed portions  82  having the same depth shallower than that of the ring-shaped deep groove  60  are formed instead of the inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62 . In detail, the plurality of inner recessed portions  81  and the plurality of outer recessed portions  82  are formed, so as to be arranged in two lines, namely, an inner line and an outer line, along the circumferential direction R to surround doubly the ring-shaped deep groove  60 . These inner recessed portions  81  and outer recessed portions  82  are filled with a lubricant oil agent G such as grease similarly to the inner ring-shaped shallow groove  61  and the outer ring-shaped shallow groove  62 . 
         [0108]    Here, the inner recessed portions  81  and the outer recessed portions  82  are arranged so as to have phase difference of a prescribed angle θ1 (θ1=6° in the present example) in the circumferential direction R from each other. 
         [0109]    Each of the plurality of inner recessed portions  81  positioned in the inner line comprises: an inner arc-like wall surface  81   a  which extends in an arc shape in the circumferential direction R whose center is the axis O; an outer arc-like wall surface  81   b  which is positioned on the outer side in the radial direction relative to the inner arc-like wall surface  81   a  and extends in an arc shape in the circumferential direction R whose center is the axis O; a pair of semicircular wall surfaces  81   c  which are each connected to the inner arc-like wall surface  81   a  and the outer arc-like wall surface  81   b  and are opposde each other in the circumferential direction R; and a bottom surface  81   d  which is connected to the inner arc-like wall surface  81   a , the outer arc-like wall surface  81   b , and the pair of semicircular wall surfaces  81   c.    
         [0110]    Each of the plurality of outer recessed portions  82  positioned in the outer line comprises: an inner arc-like wall surface  82   a  which extends in an arc shape in the circumferential direction R whose center is the axis O; an outer arc-like wall surface  82   b  which is positioned on the outer side relative to the inner arc-like wall surface  82   a  and extends in an arc shape in the circumferential direction R whose center is the axis O; a pair of semicircular wall surfaces  82   c  which are each connected to the inner arc-like wall surface  82   a  and the outer arc-like wall surface  82   b  and are opposed each other in the circumferential direction R; and a bottom surface  82   d  which is connected to the inner arc-like wall surface  82   a , the outer arc-like wall surface  82   b , and the pair of semicircular wall surfaces  82   c.    
         [0111]    Here, the area ratio of the opening spaces of the plurality of inner recessed portions  81  and the plurality of outer recessed portions  82  to the ring-shaped upper surface  5  of the bearing body  2 A is 20-50%, and favorably 30-40%. The plurality of inner recessed portions  81  and the plurality of outer recessed portions  82  are formed in the ring-shaped upper surface  5  of the bearing body  2 A and arranged in two lines, namely, the inner line and the outer line. In detail, to show satisfactorily the low friction property of the lubricant oil agent G such as grease in the plurality of inner recessed portions  81  and the plurality of outer recessed portions  82  which are filled with and hold the lubricant oil agent G, it is favorable that the ratio of the area of the plurality of inner recessed portions  81  and the plurality of outer recessed portions  82  to the area of the ring-shaped upper surface  5  of the bearing body  2 A is at least 20%. However, when the ratio exceeds 50%, it incurs deterioration of strength of the thrust slide bearing surface, and plastic deformation such as creep is likely to occur. In the example shown in  FIG. 6(A) , the recessed portions are formed so that the ratio becomes about 30%. 
         [0112]    In the thrust slide bearing  1  using the bearing body  2 A of the above configuration, the plurality of inner recessed portions  81  and the plurality of outer recessed portions  82  are formed in the ring-shaped upper surface  5  functioning as the sliding surface of the bearing body  2 A. Accordingly the contact area between the ring-shaped upper surface  5  of the bearing body  2 A and the counterpart member (the ring-shaped lower surface  47  of the outer disk portion  43  of the ring-shaped metal plate  4 ) can be reduced. Thus, the contact pressure (load per unit of area) applied on the ring-shaped upper surface  5  of the bearing body  2  is raised. This can realize further reduction of friction, in addition to the reduction of friction owing to the interposition of the lubricant oil agent G with which the inner recessed portions  81  and the outer recessed portions  82  are filled, between the ring-shaped upper surface  5  of the bearing body  2 A and the ring-shaped lower surface  47  of the outer disk portion  43  of the ring-shaped metal plate  4 . Further, in the case where cationic electrodeposition coating is formed on the ring-shaped lower surface  47  of the outer disk portion  43  of the ring-shaped metal plate  4  as the counterpart member, further reduction of friction can be realized by adding reduction of friction owing to friction reduction between resins, namely, between the ring-shaped upper surface  5  of the bearing body  2 A made of synthetic resin and the cationic electrodeposition coating. 
         [0113]    Also in the case where the bearing body  2 A is used, the ring-shaped metal plate  4  has the inner disk portion  44  that is integrally formed with the outer disk portion  43  and is positioned in the through-hole  25  defined by the inner periphery  26  of the ring-shaped cover  3 . Accordingly the inner disk portion  44  serves the same work to a reinforcing portion (rib) for the outer disk portion  43 . As a result, deformation of the ring-shaped metal plate  4  can be prevented even if large force is applied to the ring-shaped metal plate  4  via the piston rod  63 , and thus generation of abnormal noise due to deformation of the ring-shaped metal plate  4  in relative rotation of the piston rod  63  can be suppressed as far as possible. 
         [0114]    Further, the ring-shaped upper surface  5  of the bearing body  2 A which functions as the sliding surface, comprises: the ring-shaped deep groove  60  formed in the innermost side of the ring-shaped upper surface  5 ; and the plurality of inner recessed portions  81  and the plurality of outer recessed portions  82 , which are formed to be arranged to surround doubly the ring-shaped deep groove  60  and have the same depth shallower than that of the ring-shaped deep groove. These portions and groove, namely, the plurality of inner recessed portions  81 , the plurality of outer recessed portions  82 , and the ring-shaped deep groove  60 , are filled with the lubricant oil agent G. Thus, the height of the thrust slide bearing  1  itself can be reduced, the installation space of the thrust slide bearing  1  can be reduced, and the number of the components parts can be reduced, to realize weight reduction and cost reduction of the thrust slide bearing  1  as a whole. 
         [0115]    Further, a first intrusion prevention means for preventing intrusion of foreign substances such as grit and dust from the outer periphery surface side of the thrust slide bearing  1  onto the ring-shaped upper surface  5  of the bearing body  2 A is formed by the outer periphery surface  171  of the cylindrical protruding portion  17  of the bearing body  2 A, the outer cylindrical drooping portion  39  of the ring-shaped cover  3  which surrounds the outer periphery surface  171 , and the ring-shaped convex portion  19  which integrally protrudes outward in the radial direction from the outer circumferential edge of the ring-shaped protruding portion  12  of the bearing body  2 A so as to close the ring-shaped gap formed in the radial direction between the outer periphery  171  and the outer cylindrical drooping portion  39 . Further, a second intrusion prevention means for preventing intrusion of foreign substances such as grit and dust from the outer periphery surface side of the thrust slide bearing  1  onto the ring-shaped upper surface  5  of the bearing body  2 A is formed by the upward-open recessed portion  16  of the ring-shaped protruding portion  12  of the bearing body  2 A and the outer cylindrical drooping portion  39  which is inserted into the upward-open recessed portion so that the engaging protruding portion  31  of the ring-shaped cover  3  is elastically fitted to the engaging protruding portion  18  of the bearing body  2 A. Therefore, intrusion of foreign substances such as grit and dust onto the ring-shaped upper surface  5  functioning as the sliding surface of the bearing body  2 A as far as possible, and rotation of the ring-shaped metal plate  4  about the axis O relative to the bearing body  2 A can be performed smoothly. 
       INDUSTRIAL APPLICABILITY 
       [0116]    The thrust slide bearing of the present invention can be widely applied to slide bearings for various mechanisms including a strut-type suspension. 
       REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               1 : thrust slide bearing;  2 ,  2 A: bearing body;  3 : ring-shaped cover;  4 : ring-shaped metal plate;  5 : ring-shaped upper surface;  6 : through-hole;  7 : inner periphery surface;  8 : cylindrical portion;  9 : outer periphery surface;  10 : ring-shaped flange portion;  12 : ring-shaped protruding portion;  13 : upper surface;  15 : upper surface;  16 : upward-open recessed portion;  17 : cylindrical protruding portion;  18 : engaging protruding portion;  19 : ring-shaped convex portion;  25 : through-hole;  26 : inner periphery surface;  27 : lower surface;  28 : disk portion;  31 : engaging protruding portion;  32 : inner cylindrical drooping portion;  33 : ring-shaped convex portion;  34 : lower surface;  36 : downward-open recessed portion;  39 : outer cylindrical drooping portion;  43 : outer disk portion;  44 : inner disk portion;  46 : upper surface;  47 : ring-shaped lower surface;  60 : ring-shaped deep groove;  61 : inner ring-shaped shallow groove;  62 : outer ring-shaped shallow groove; and G: lubricant oil agent.