Patent Publication Number: US-2016245339-A1

Title: Roller bearing cage, assembly and production method therefor, and roller bearing

Description:
TECHNICAL FIELD 
     One aspect of the present invention relates to a cage suitably applied to a roller bearing used for supporting a main shaft or the like of a wind power generation device, an assembly method therefor, and a roller bearing. 
     Another aspect of the present invention relates to a cage suitably applied to a tapered roller bearing used for supporting a main shaft or the like of a wind power generation device, a production method therefor, and a tapered roller bearing. 
     Still another aspect of the present invention relates to a split cage for a roller bearing, and relates to, for example, a split cage used for a large roller bearing rotatably supporting a main shaft of a wind power generation device. 
     BACKGROUND ART 
     As a roller bearing used for supporting a main shaft of a wind power generation device, for example, a tapered roller bearing is used, and a pin-type cage is used as its cage in some cases (see, for example, Patent Document 1). The pin-type cage includes a pair of retaining rings disposed on both sides along an axial direction of a tapered roller, and a plurality of pins disposed at intervals along a circumferential direction and each having both ends connected to the pair of retaining rings. Each of the pins is inserted into a through hole formed on a center axis line of a corresponding tapered roller, so that a plurality of tapered rollers can be retained at intervals along the circumferential direction. 
     Besides, a roller bearing used for supporting a main shaft of a wind power generation device has a diameter as large as about 1 to 2 meters, and is thus very large and has a large weight. Therefore, a synthetic resin cage that can be reduced in weight has been recently used instead of a pin-type cage. A synthetic resin cage is, however, more difficult to integrally mold as the size is larger, and therefore, a split type cage that is dividedly molded with respect to each section along the circumferential direction is generally used (see, for example, Patent Document 2). 
     Alternatively, in a wind power generation device of a horizontal axis propeller type, a roller bearing is used for rotatably supporting a main shaft on which a blade is attached. 
     In recent years, in accordance with increase of the size of a wind power generation device, the diameter of a main shaft becomes larger than several meters in some cases, and a roller bearing is also increased in size for supporting such a large main shaft. 
     As a cage used for a large roller bearing, a synthetic resin cage is used in some cases. A synthetic resin cage is advantageous, to a metal cage assembled by welding, in that the weight is small and accuracy is easily ensured. It is, however, difficult to integrally mold, by injection molding, a synthetic resin cage having a large diameter. 
     Therefore, a split cage divided into a plurality of sections along the circumferential direction is used. Such a split cage includes a plurality of cage segments arranged in a ring shape along the circumferential direction. 
     A typical example of this type of cage segment includes one disclosed in Patent Document 3. The cage segment disclosed in Patent Document 3 is illustrated in  FIG. 24 . 
     Referring to  FIG. 24 , the cage segment  100  of Patent Document 3 is in an arc shape coaxial with an inner ring and outer ring not shown. The cage segment  100  includes first and second rim portions  210  and  220  opposing each other at a prescribed distance to be paired with each other, and a plurality of pillar portions  400  that are laid between the paired first and second rim portions  210  and  220  and together form, along the circumferential direction, pockets  300  therebetween for holding rolling elements not shown. 
     RELATED ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: JP-A-2008-256168 
     Patent Document 2: JP-A-2012-77882 
     Patent Document 3: JP-A-2007-255626 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     If the above-described pin-type cage is applied to a large tapered roller bearing, its retaining ring is also very large, and hence, it is difficult not only to produce it but also to handle it for storage, transportation and the like. 
     On the other hand, in applying a synthetic resin split cage, it is not very difficult to produce it and handle it, but there is a slight difficulty in assemblability of a roller bearing such as a tapered roller. For assembling the roller bearing, taper rollers are to be inserted into pockets of the cage while providing the cage on an outer circumferential side of an inner ring, and when the cage is divided, it easily comes off from the outer circumferential side of the inner ring, and at the same time, the tapered rollers easily come off from the inner ring. 
     Besides, in the case of the cage segment  100  of Patent Literature 3 illustrated in  FIG. 24 , a plurality of cage segments  100  are not mutually connected in assembling a roller bearing, and therefore, there arises a problem in which the roller bearing is difficult to assemble because the cage segments  100  easily fall off to scatter. 
     In consideration of the above-described actual situations, an object of one aspect of the present invention is to provide a roller bearing cage whose components are easily produced and handled and whose structure can be simplified as much as possible, an assembly method therefor, and a roller bearing. 
     An object of another aspect of the present invention is to provide a tapered roller bearing cage whose components are easily produced and handled, and which can be easily mounted on a tapered roller bearing, a production method therefor, and a tapered roller bearing. 
     An object of still another aspect of the present invention is to provide a split cage for a roller bearing whose segments are difficult to scatter in assembling the roller bearing, and with which the roller bearing can be easily assembled. 
     Means for Solving the Problem 
     A first aspect of the present invention includes a roller bearing cage having a ring shape for retaining an interval along a circumferential direction between a plurality of rolling elements in a roller bearing, the roller bearing cage including: a plurality of bar-shaped members which are arranged along the circumferential direction and which restrain movement of the rolling elements along the circumferential direction; a plurality of connecting members, each of which connects end portions along a lengthwise direction of the bar-shaped members adjacent to each other along the circumferential direction; and a fixing structure which fixes the bar-shaped member and the connecting member so as to be relatively unrotatably around an axis line along the lengthwise direction of the bar-shaped member. 
     Since the roller bearing cage according to the first aspect of the present invention includes the plural bar-shaped members, the plural connecting members and the fixing structure, even if it is applied to a large roller bearing, respective components can be made small and simple, and it can be easily produced and handled. Besides, since the cage of the first aspect of the present invention is formed in a ring shape by connecting the plural bar-shaped members with the plural connecting members, when it is mounted on a bearing ring of a roller bearing, it is difficult to be detached from the bearing ring, and hence, an operation of assembling the roller bearing can be easily performed. Besides, since the bar-shaped members and the connecting members are fixed by the fixing structure, the cage can be fixed in a prescribed ring-shaped form, the respective connecting members can be prevented from individually swinging, and vibration of the cage otherwise caused by rotation of the bearing ring of the roller bearing can be suppressed. 
     A second aspect of the present invention includes a roller bearing cage having a ring shape for retaining an interval along a circumferential direction between tapered rollers corresponding to a plurality of rolling elements used in a tapered roller bearing as a roller bearing, the roller bearing cage including: a plurality of bar-shaped members which are arranged along the circumferential direction and which restrain movement of the rolling elements along the circumferential direction; and a plurality of connecting members, each of which connects end portions along a lengthwise direction of the bar-shaped members adjacent to each other along the circumferential direction, wherein the plurality of bar-shaped members are disposed such that axial centers along the lengthwise direction of the plurality of bar-shaped members cross one another at one point on an axial center of the roller bearing, and wherein the connecting members are bent in an arc shape with a radius of curvature about the one point. 
     Since the roller bearing cage according to the second aspect of the present invention includes the plural bar-shaped members and the plural connecting members, even if it is applied to a large tapered roller bearing, respective components can be made small and simple, and it can be easily produced and handled. Besides, since the cage of the second aspect of the present invention is formed in a ring shape by connecting the plural bar-shaped members with the plural connecting members, when it is mounted on a bearing ring of a tapered roller bearing, it is difficult to be detached from the bearing ring, and hence, an operation of assembling the tapered roller bearing can be easily performed. Besides, each connecting member of the cage is bent in an arc shape having, as the center of curvature, one point on the axial center of the tapered roller bearing where the axial centers along the lengthwise direction of the bar-shaped members cross one another, and therefore, the bar-shaped members can be attached perpendicularly to the connecting members, and the attaching operation can be easily performed. 
     A third aspect of the present invention includes the roller bearing cage according to the second aspect, wherein the connecting member has a hole, formed in a direction perpendicular to the connecting member, for inserting and attaching the bar-shaped member. 
     With this configuration, the hole for attaching the bar-shaped member can be easily formed in the connecting member. 
     A fourth aspect of the present invention includes the roller bearing cage according to the second or third aspect, further including: a fixing structure which fixes the bar-shaped member and the connecting member so as to be relatively unrotatably around an axis line along the lengthwise direction of the bar-shaped member. 
     In this case, when the bar-shaped members and the connecting members are fixed by the fixing means, the cage can be fixed in a prescribed ring-shaped form, the connecting members can be prevented from individually swinging, and vibration of the cage otherwise caused by rotation of the bearing ring of the tapered roller bearing can be suppressed. 
     A fifth aspect of the present invention includes the roller bearing cage according to the first or fourth aspect, wherein the fixing structure includes: a male screw portion formed in an end portion of the bar-shaped member; and a female screw member to be screwed on the male screw portion inserted into the hole formed in the connecting member. 
     In this case, when the female screw portion is screwed on the male screw member, the bar-shaped member and the connecting member can be fixed. 
     A sixth aspect of the present invention includes the roller bearing cage according to the first, fourth or fifth aspect, wherein the fixing structure includes: an end portion of the bar-shaped member; and a hole formed in the connecting member to which the end portion of the bar-shaped member is press-fitted. 
     In this case, the bar-shaped members can be fixed on the connecting members without using an additional component. 
     A seventh aspect of the present invention includes the roller bearing cage according to any one of the first to sixth aspects, wherein a space surrounded by the bar-shaped members adjacent to each other along the circumferential direction and the connecting member connecting the bar-shaped members is formed as a pocket for holding the rolling element. 
     An eighth aspect of the present invention includes the roller bearing cage according to any one of the first to sixth aspects, wherein the bar-shaped member is inserted into a hole formed on a center axis line of the rolling element. 
     In either of the seventh and eighth aspects, an interval along the circumferential direction between the plural rolling elements can be suitably retained. 
     A ninth aspect of the present invention includes a production method for the roller bearing cage according to any one of the second to eighth aspects, the production method including: forming, in the connecting member formed in a plate shape, a hole for inserting and attaching the bar-shaped member in a direction perpendicular to the connecting member; and bending the connecting member after forming the hole. 
     When this production method is employed, the hole for inserting and attaching the bar-shaped member is formed in the direction perpendicular to the connecting member in a plate shape before bending, and hence, the hole can be easily formed. 
     A tenth aspect of the present invention includes an assembly method for the roller bearing cage according to the first, fourth, fifth, sixth, seventh or eighth aspect, the assembly method including: connecting the plurality of bar-shaped members and the plurality of connecting members so as to form a ring shape in a state in which at least one end portion of the bar-shaped member and the connecting member are placed so as to be relatively rotatably around the axis line, and disposing the connected bar-shaped members and the connecting members along a bearing ring of the roller bearing; and fixing, by the fixing structure, the bar-shaped members and the connecting members disposed along the bearing ring so as to be relatively unrotatably around the axis line. 
     When this assembly method is employed, at the stage where the bar-shaped members and the connecting members are connected and disposed along the bearing ring of the roller bearing, the bar-shaped members and the connecting members are in a relatively rotatable state, and hence, the bar-shaped members and the connecting members connected to one another can be comparatively freely moved, and therefore, an operation of connecting the bar-shaped members and the connecting members and an operation of disposing them along the bearing ring can be easily performed. Then, after disposing the bar-shaped members and the connecting members along the bearing ring, the bar-shaped members and the connecting members are fixed relatively unrotatably, and hence, the vibration of the cage otherwise caused by the rotation of the bearing ring can be suppressed. 
     An eleventh aspect of the present invention includes a roller bearing including: an inner ring; an outer ring disposed on an outside along a radial direction of the inner ring; a plurality of rolling elements arranged along a circumferential direction between the inner ring and the outer ring; and the cage according to any one of the first to eighth aspects, which retains an interval along the circumferential direction between the plurality of rolling elements. 
     A twelfth aspect of the present invention includes a split cage for a roller bearing, including: a plurality of first segments made of a synthetic resin and a plurality of second segments made of a synthetic resin, the first segments and the second segments being arranged in a ring shape along a circumferential direction, wherein each of the plurality of first segments includes: a rim portion positioned on a first side along an axial direction; a pair of pillar portions which protrude from the rim portion toward a second side along the axial direction opposite to the first side along the axial direction, and which are respectively disposed between rolling elements of the roller bearing; and a pair of engaging portions provided on the second side along the axial direction of the pair of pillar portions, wherein each of the plurality of second segments includes: a first engaged portion to be engaged with the engaging portion provided on the pillar portion disposed on a first side along the circumferential direction of the first segment; and a second engaged portion to be engaged with the engaging portion provided on the pillar portion disposed on a second side along the circumferential direction opposite to the first side along the circumferential direction of another one of the first segments adjacent, on the first side along the circumferential direction, to the first segment, and wherein the pair of engaging portions are engaged with the pair of engaged portions, whereby the plurality of first segments are connected in a ring shape by the plurality of second segments. 
     In this configuration, the split cage includes the first segments and the second segments, and in assembling the roller bearing, the first segments adjacent to each other along the circumferential direction are connected by the second segment, and therefore, the first segments and the second segments are difficult to scatter, and the roller bearing can be easily assembled. 
     A thirteenth aspect of the present invention includes the split cage for a roller bearing according to the twelfth aspect of the present invention, wherein each of the plurality of first segments includes a contact portion to be brought into contact with another one of the first segments adjacent along the circumferential direction. 
     A fourteenth aspect of the present invention includes the split cage for a roller bearing according to the twelfth or thirteenth aspect, wherein each of the plurality of second segments includes a contact portion to be brought into contact with another one of the second segments adjacent along the circumferential direction. 
     A fifteenth aspect of the present invention includes the split cage for a roller bearing according to any one of the twelfth to fourteenth aspects, wherein a surface of the pillar portion to be in contact with a roller used as the rolling element has a bent surface recessed along the circumferential direction for restraining the roller from moving along a radial direction. 
     In this configuration, the roller can be restrained from moving along the radial direction. 
     A sixteenth aspect of the present invention includes the split cage for a roller bearing according to any one of the twelfth to fifteenth aspects, wherein the engaged portion has a recess through which the engaging portion is capable of being inserted from the radial direction and from which the inserted engaging portion is incapable of being pulled out along the axial direction, wherein each of the plurality of second segments has a groove, which is opened on a surface on the first side along the axial direction of the second segment and crosses the engaged portions, and wherein the split cage for a roller bearing further includes a stopper which is inserted in the groove and which prevents the engaging portion engaged with the engaged portion from coming off in the radial direction. 
     In this configuration, the engaging portion engaged with the engaged portion can be prevented from coming off in the radial direction. 
     A seventeenth aspect of the present invention includes the split cage for a roller bearing according to any one of the twelfth to sixteenth aspects, wherein each of the engaged portions has a recess through which the engaging portion is capable of being inserted from outside along the radial direction and from which the inserted engaging portion is incapable of being pulled out in the axial direction, and wherein the split cage for a roller bearing further includes a projection which is formed in an outer side along the radial direction of each of the plurality of second segments which prevents the engaging portion engaged with the engaged portion from coming off outward in the radial direction. 
     In this configuration, the engaging portion engaged with the engaged portion can be prevented from coming off outward in the radial direction. 
     Advantages of the Invention 
     According to one aspect of the present invention, a roller bearing cage can be easily produced and handled and its structure can be simplified as much as possible. 
     According to another aspect of the present invention, components of a tapered roller bearing cage can be easily produced and handled, and the cage can be easily mounted on a tapered roller bearing. 
     According to still another aspect of the present invention, a split cage for a roller bearing whose first segments and second segments are difficult to scatter in assembling the roller bearing, and with which the roller bearing can be easily assembled can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical cross-sectional view of a part of a roller bearing according to a first embodiment of the present invention. 
         FIG. 2  is a lateral cross-sectional view of the roller bearing. 
         FIG. 3  is an explanatory diagram illustrating the relationship between a rolling element and a cage of the roller bearing. 
         FIGS. 4( a ) to 4( c )  are diagrams of components of the cage. 
         FIGS. 5( a ) and 5( b )  are diagrams illustrating the components during the production (assembly) of the cage. 
         FIG. 6  is a vertical cross-sectional view of a part of a roller bearing according to a second embodiment of the present invention. 
         FIG. 7  is a front view of a part of the roller bearing. 
         FIG. 8  is an explanatory diagram illustrating the relationship between a rolling element and a cage of the roller bearing. 
         FIGS. 9( a ) and 9( b )  are vertical cross-sectional view of a roller bearing according to a third embodiment of the present invention. 
         FIG. 10  is a cross-sectional view of a principal part of a roller bearing according to a fourth embodiment of the present invention. 
         FIG. 11  is a schematic front view thereof. 
         FIG. 12  is a plan view illustrating a part of a split cage for the roller bearing of  FIG. 11 . 
         FIG. 13  is an exploded perspective view of  FIG. 12 . 
         FIG. 14  is a plan view illustrating a part of a split cage for a roller bearing according to a fifth embodiment of the present invention. 
         FIG. 15  is an exploded perspective view of  FIG. 14 . 
         FIG. 16  is a cross-sectional view of a part for a roller bearing according to a sixth embodiment of the present invention. 
         FIG. 17  is a plan view illustrating a part of a split cage for a roller bearing according to a seventh embodiment of the present invention. 
         FIG. 18  is an exploded perspective view of  FIG. 17 . 
         FIG. 19  is a perspective view illustrating a part of a split cage for a roller bearing according to an eighth embodiment of the present invention. 
         FIG. 20  is a perspective view of a state where a stopper of  FIG. 19  is removed. 
         FIG. 21  is a perspective view of a second segment of  FIG. 20 . 
         FIG. 22  is a perspective view illustrating a part of a split cage for a roller bearing according to a ninth embodiment of the present invention. 
         FIG. 23  is a perspective view of a second segment of  FIG. 22 . 
         FIG. 24  is a perspective view of a cage segment according to the background art of the present invention. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 1  is a vertical cross-sectional view of a part of a roller bearing according to a first embodiment of the present invention,  FIG. 2  is a lateral cross-sectional view of a part of the roller bearing, and  FIG. 3  is an explanatory diagram illustrating the relationship between a rolling element and a cage of the roller bearing. It is noted that a tapered roller bearing will be described in the present embodiment as an example of the roller bearing. In the tapered roller bearing, a tapered roller is used as a rolling element. 
     The roller bearing  10  of the present embodiment is used, for example, for supporting a main shaft of a wind power generation device, and includes a ring-shaped inner ring  11 , a ring-shaped outer ring  12  disposed on the outside along a radial direction of the inner ring  11 , a plurality of rolling elements (tapered rollers)  13  disposed along a circumferential direction between the inner ring  11  and the outer ring  12 , and a cage  14  for retaining a circumferential distance between the plural rolling elements  13 . 
     The inner ring  11  includes an inner ring raceway  11   a  formed in a conical shape, and a small flange  11   b  and a large flange  11   c  formed on both sides along an axial direction of the inner ring raceway  11   a  and protruding outward along the radial direction. The outer ring  12  includes an outer ring raceway  12   a  formed in a conical shape. Each rolling element  13  is a tapered roller formed in a shape of a frustum cone (a frustum of a cone), and is capable of moving by rolling on the inner ring raceway  11   a  and the outer ring raceway  12   a . The rolling element  13  is restrained in movement along the axial direction by the small flange  11   b  and the large flange  11   c . Besides, as illustrated in  FIG. 3 , the respective rolling elements  13  are disposed so that their center axis lines X 1  can cross one another at one point on an axial center of the roller bearing  10 . 
     The cage  14  includes a plurality of pins (bar-shaped members)  18  arranged along the circumferential direction, a plurality of connecting links (connecting members)  21  and  22  each connecting the pins  18  adjacent to each other in the circumferential direction, and nuts  25  fixing the pins  18  and the connecting links  22  to each other, and is formed in a ring shape as a whole. Besides, a space surrounded by the pins  18  adjacent to each other in the circumferential direction and the connecting links  21  and  22  connecting these pins  18  is formed as a pocket for holding each rolling element  13 . 
     Each pin  18  includes a trunk  19  formed in an elongated rod shape, and attaching portions  23  and  24  provided in both end portions along a lengthwise direction of the trunk  19 . The trunk  19  is formed in a cylindrical shape, and is provided between the rolling elements  13  adjacent to each other in the circumferential direction so as to restrain the movement of the rolling elements  13  along the circumferential direction. The attaching portions  23  and  24  are provided as portions to be attached to the first and second connecting links  21  and  22 . Besides, the respective pins  19  are disposed so that their center lines (axis lines) X 2  can cross one another at one point on the axial center of the roller bearing  10 . 
     The respective pins  18  are disposed, as illustrated in  FIG. 1 , on the outside, along the radial direction of the roller bearing  10 , of the center axis lines X 1  of the rolling elements  13  disposed between the inner ring  11  and the outer ring  12 . Besides, as illustrated in  FIG. 2 , a distance L between the trunks  19  of the pins  18  adjacent to each other in the circumferential direction is substantially the same as or slightly smaller than a diameter D of the rolling element  13  disposed therebetween, and is a size capable of forming a small gap from the rolling element  13 . 
     As illustrated in  FIG. 3 , the connecting links  21  and  22  include first connecting links  21  connecting first end portions along a lengthwise direction of the pins  18  to each other, and second connecting links  22  connecting second end portions along the lengthwise direction of the pins  18  to each other. The first connecting links  21  and the second connecting links  22  are alternately disposed along the circumferential direction. Accordingly, the first connecting link  21  is attached to the first end portion of each pin  18 , and the second connecting link  22  is attached to the second end portion thereof. 
     Each of the first connecting links  21  and the second connecting links  22  is made of a substantially elliptical plate material, and the end portions (attaching portions)  23  and  24  of the pin  18  are respectively attached to its end portions along the lengthwise direction. Besides, each of the first and second connecting links  21  and  22  is, as illustrated in  FIG. 3 , formed to be bent in an arc shape. The center of curvature of each of the first and second connecting links  21  and  22  is set to the one point on the axial center of the roller bearing  10  where the center lines X 2  of the respective pins  18  cross one another. Accordingly, the pins  18  and the first and second connecting links  21  and  22  are connected to be mutually perpendicular. 
       FIGS. 4( a ) to 4( c )  are diagrams of components of the cage. It is noted that the first and second connecting links  21  and  22  are illustrated, in  FIGS. 4( a ) to 4( c ) , in a state before being bent. 
       FIG. 4( c )  illustrates the pin  18  and the nut  25 , the first attaching portion  23  of the pin  18  is formed in a cylindrical shape having substantially the same diameter as the trunk  19 . The second attaching portion  24  is formed in a cylindrical shape having a smaller diameter than the trunk  19 , and a male screw portion  24   a  to be screwed into the nut  25  is formed on the outer circumferential surface thereof. A step portion  20  is formed on a boundary between the attaching portion  24  and the trunk  19 , and the step portion  20  is used for positioning and fixing the second connecting link  22 . 
       FIG. 4( a )  illustrates a front view and a cross-sectional view of the first connecting link  21 , and  FIG. 4( b )  illustrates a front view and a cross-sectional view of the second connecting link  22 . In both end portions along the lengthwise direction of each of the first connecting link  21  and the second connecting link  22 , circular attaching holes  21   a  or  22   a  are formed. 
     Each of the attaching holes (first attaching holes)  21   a  of the first connecting link  21  has an inner diameter slightly smaller than the outer diameter of the first attaching portion  23  of the pin  18 . Besides, as illustrated in  FIG. 1 , the attaching portion  23  of the pin  18  is press-fitted to the attaching hole  21   a  in a tight fit state, and thus, the pin  18  is fixed on the first connecting link  21 . Furthermore, a part of the attaching portion  23  of the pin  18  protruding beyond the attaching hole  21   a  is caulked (with a caulked part illustrated with a sign K), so as to prevent the attaching portion from coming off from the attaching hole  21   a.    
     Besides, as illustrated in  FIG. 4( b ) , the attaching hole (second attaching hole)  22   a  of the second connecting link  22  has an inner diameter rather larger than the outer diameter of the second attaching portion  24  of the pin  18 . Besides, as illustrated in  FIG. 1 , the attaching portion  24  of the pin  18  is inserted into the attaching hole  22   a  in such a manner that the male screw portion  24   a  at its tip protrudes beyond the attaching hole  22   a . The male screw portion  24   a  protruding beyond the attaching hole  22   a  is screwed into the nut  25 , and the pin  18  is fixed on the second connecting link  22  because the second connecting link  22  is sandwiched between the nut  25  and the step portion  20  of the pin  18 . Incidentally, the configuration in which the attaching portion  23  of the pin  18  is fixed by press-fitting to the attaching hole  21   a  of the first connecting link  21  and the configuration in which the attaching portion  24  is fixed in the attaching hole  22   a  of the second connecting link  22  with the nut  25  described above both correspond to a fixing structure for fixing the pin  18  onto the first and second connecting links  21  and  22 . 
     Next, a production (assembly) method for the cage  14  will be described. 
     As illustrated in  FIG. 4( a ) , the first connecting link  21  has the attaching holes  21   a  formed in a plate state before being bent in an arc shape. At this point, the attaching holes  21   a  are formed to penetrate in a direction perpendicular to the first connecting link  21  (for example, in a direction perpendicular to a center line L 1  along a thickness direction of the first connecting link  21 ). Similarly, the second connecting link  22  also has the attaching holes  22   a  formed in a plate state before being bent in an arc shape as illustrated in  FIG. 4( b ) . The attaching holes  22   a  are formed to penetrate in a direction perpendicular to the second connecting link  22  (for example, in a direction perpendicular to a center line L 2  along a thickness direction of the second connecting link  22 ). 
       FIGS. 5( a ) and 5( b )  are diagrams illustrating the components during the production (assembly) of the cage. 
     The attaching portion  23  of the pin  18  is press-fitted to the attaching hole  21   a  of the first connecting link  21  before being bent, and caulked (as illustrated on the left side of  FIG. 5( a ) ). Thereafter, the first connecting link  21  is bent so that the center line X 2  of the pin  18  can be directed toward a prescribed direction (as illustrated on the right side of  FIG. 5( a ) ). Then, a large number of preliminary assemblies (sub-assemblies) SA each of which includes the first connecting link  21  and the pin  18  in this state are produced. 
     On the other hand, as illustrated in  FIG. 5( b ) , the second connecting link  22  is bent after forming the attaching holes  22   a , and is used as one component. 
     Then, for assembling the cage  14  to be mounted on the outer circumferential side of the inner ring  11 , the second attaching portion  24  of the pin  18  of each preliminary assembly SA is inserted into the attaching hole  22   a  of a corresponding one of the second connecting links  22  and the nut  25  is loosely screwed on the male screw portion  24   a  of the second attaching portion  24 , so that all the preliminary assemblies SA can be successively connected to the second connecting links  22  in a temporarily connected state, and thus, the cage  14  is formed in a state where it is disconnected in one portion along the circumferential direction (in a belt-like state). Then, while the rolling elements  13  are mounted on the inner ring raceway  11   a , the cage  14  in a temporarily connected state is wound around on the outer circumferential side of the inner ring raceway  11   a , and thereafter, the cage  14  is connected into a ring shape. 
     In the cage  14  in a temporarily connected state, the pin  18  and the second connecting link  22  are relatively rotatable around the center line X 2  of the pin  18 , and hence, the cage  14  can be freely bent, so that an operation of winding it around the outer circumference of the inner ring raceway  11   a  can be easily performed. Then, after the cage  14  is wound around the outer circumference of the inner ring raceway  11   a  and connected into a ring shape, all the nuts  25  are rigidly fastened. Thus, the pin  18  and the second connecting link  22  are fixed in a relatively unrotatably state, and the whole cage  14  is fixed in a prescribed ring form. Since the cage  14  is thus fixed in a ring form, the respective connecting links  22  can be prevented from individually swinging in the radial direction when the inner ring  11  or the outer ring  12  of the roller bearing  10  is rotated, and thus, vibration of the cage  14  can be suppressed. 
     In the present embodiment, since the first and second connecting links  21  and  22  are bent in an arc shape, even if the attaching holes  21   a  and  22   a  are formed perpendicularly to the lengthwise direction of the first and second connecting links  21  and  22 , the respective pins  18  can be disposed to have their center lines X 2  crossing one another at one point on the axial center of the roller bearing  10 . In other words, if the first and second connecting links  21  and  22  are in a plate shape, in order to dispose the respective pins  18  to have their center lines X 2  crossing one another at one point on the axial center of the roller bearing  10 , it is necessary to attach the pins  18  to the first and second connecting links  21  and  22  in an inclined state, which makes it difficult to form the attaching holes  21   a  and  22   a  in the first and second connecting links  21  and  22 . In the present embodiment, however, the attaching holes  21   a  and  22   a  can be formed perpendicularly to the lengthwise direction of the first and second connecting links  21  and  22 , and therefore, the attaching holes  21   a  and  22   a  can be easily formed. 
     The respective pins  18  are disposed on the outside, along the radial direction of the roller bearing  10 , of the center axis lines X 1  of the rolling elements  13 , and the distance L between the pins  18  adjacent to each other in the circumferential direction is set to be substantially the same as or smaller than the diameter D of the rolling element  13  disposed therebetween, and therefore, in assembling the roller bearing  10 , the rolling elements  13  can be retained in a state where they are fit in the inner ring  11  even without attaching the outer ring  12 . 
     Besides, in the present embodiment, the cage  14  can be formed to have a different outer diameter by controlling the numbers of the pins  18  and the connecting links  21  and  22 . Therefore, the pins  18  and the connecting links  21  and  22  can be shared among roller bearings  10  using the same rolling elements  13  but having different outer diameters. Accordingly, the production cost can be reduced. 
     Furthermore, the cage  14  of the present embodiment is very simply constructed from the pins  18 , the connecting links  21  and  22 , and the nuts  25 , and therefore can be easily and inexpensively produced. 
     Second Embodiment 
       FIG. 6  is a vertical cross-sectional view of a part of a roller bearing according to a second embodiment of the present invention,  FIG. 7  is a front view of a part of the roller bearing, and  FIG. 8  is an explanatory diagram illustrating the relationship between a rolling element and a cage of the roller bearing. 
     In the present embodiment, instead of disposing the pin  18  between the rolling elements  13  adjacent to each other along the circumferential direction, the pin  18  is inserted into a through hole  13 a formed on the center axis line X 1  of the rolling element  13 , so as to restrain the movement of the rolling element  13  in the circumferential direction. The rolling element  13  is rotatable around the pin  18 . Besides, in the present embodiment, the center axis line X 1  of the rolling element  13  accords with the center line X 2  of the pin  18 . 
     The first and second connecting links  21  and  22  of the cage  14  are bent in an arc shape as in the first embodiment. Besides, the attaching portion  23  disposed in one end portion of the pin  18  is fixed on the first connecting link  21  by press-fitting, and the attaching portion  24  disposed in the other end portion of the pin  18  is fixed on the second connecting link  22  with the nut  25 . 
     In the present embodiment, in order to mount the cage  14  on the outer circumferential side of the inner ring  11 , when the preliminary assemblies SA and the second connecting links  22  are connected in a temporarily connected state as illustrated in  FIGS. 5( a ) and 5( b ) , the rolling elements  13  are also attached to the pins  18 , the rolling elements  13  are mounted on the inner ring raceway  11   a together with the cage  14  in a temporarily connected state, and then the cage  14  is connected in a ring shape. 
     Third Embodiment 
       FIGS. 9( a ) and 9( b )  are vertical cross-sectional view of a part of a roller bearing according to a third embodiment of the present invention. 
     In the present embodiment, the roller bearing  10  is a cylindrical roller bearing. Pins  18  are disposed between cylindrical rollers  13  adjacent to one another along a circumferential direction. A first connecting link  21  and a second connecting link  21 ,  22  of a cage  14  are in the same shape excluding the sizes of attaching holes  21   a  and  22   a , and are both in a plate shape not bent in an arc shape. Accordingly, in producing the cage  14 , a step of bending the first and second connecting links  21  and  22  is omitted. 
     Besides, in an example illustrated in  FIG. 9( a ) , flanges  11   b  and  11   c  are formed in an inner ring  11 , and the pin  18  is disposed on the outside along the radial direction of a center axis line X of the rolling element  13 , and in an example illustrated in  FIG. 9( b ) , flanges  12   b  and  12   c  are formed in an outer ring  12 , and the pin  18  is disposed on the inner side along the radial direction of the center axis line X of the rolling element  13 . 
     Also in the present embodiment, advantageous effects similar to those of the first embodiment described above can be attained. 
     The present invention is not limited to the first to third embodiments described above, but can be appropriately changed within the scope of the present invention set forth in the appended claims. 
     For example, in the first to third embodiments described above, the pin  18  of the cage  14  is fixed, at one end portion thereof, on the first connecting link  21  by press-fitting, and fixed, at the other end portion, on the second connecting link  22  with the nut  25 , but both the end portions may be fixed with the nut  25 , or both the end portions may be fixed by press-fitting. Alternatively, female screws may be formed in the attaching holes  21   a  and  22   a  of one or both of the connecting links  21  and  22 , with male screws corresponding to the female screws formed in the attaching portions  23  and  24  of the pin  18 , so that the pin  18  can be fixed on the connecting links  21  and  22  by screwing the male screws into the female screws. Alternatively, the attaching holes  21   a  and  22   a  of one or both of the connecting links  21  and  22  may be formed in a polygonal shape like a rectangular shape, and the attaching holes  21   a  and  22   a  of the attaching portions  23  and  24  may be formed in a shape of a polygonal prism corresponding to the polygonal shape of the attaching holes  21   a  and  22   a.    
     Besides, although the pin  18  is prevented from coming off from the attaching hole  21   a  by caulking one end thereof in the first to third embodiments described above, it can be prevented from coming off by bonding the pin  18  onto the first connecting link  21  by welding or the like. Alternatively, the pin  18  may be fixed by welding or the like without press-fitting one end thereof to the attaching hole  21   a.    
     Besides, after screwing the nut  25  on the male screw portion  24   a  of the pin  18 , the nut  25  may be bonded onto the second connecting link  22  by welding or the like for preventing the nut  25  from loosening. 
     Although the processing for bending the second connecting link  22  in an arc shape is performed after attaching the pin  18  on the first connecting link  21  in the first embodiment described above, the processing may be performed before attaching the pin  18 . 
     Although the pin  18  of the cage  14  is disposed between the cylindrical rollers  13  adjacent to each other along the circumferential direction in the third embodiment described above, the pin  18  may be inserted through the center of the cylindrical roller in the same manner as in the second embodiment described above. 
     In the first to third embodiments described above, the first and second connecting links  21  and  22  are disposed alternately along the circumferential direction, and as a result, a plurality of first connecting links  21  are provided at intervals along the circumferential direction on the side of the first end portions of the pins  18 , and a plurality of second connecting links  22  are provided at intervals along the circumferential direction on the side of the second end portions of the pins  18 . Instead, on the sides of the first end portions and the second end portions of the pins  18 , the first connecting links  21  and the second connecting links  22  may be respectively provided continuously along the circumferential direction. Besides, the trunk  19  of the pin  18  is not limited to the cylindrical shape, but may be formed in a conical shape, a prims shape, a pyramid shape or the like. 
     Fourth Embodiment 
       FIG. 10  is a cross-sectional view of a principal part of a roller bearing  101  using a split cage for a roller bearing according to a forth embodiment of the present invention. 
     Referring to  FIG. 10 , the roller bearing  101  is a large roller bearing for supporting a main shaft of a wind power generation device. The roller bearing  101  includes an inner ring  102 , an outer ring  103 , a plurality of rollers  104 , and a split cage  105  for retaining these rollers  104 . 
     The inner ring  102  and the outer ring  103  are members both formed in a ring shape by using a steel for a bearing such as a bearing steel or a carburized steel. On an outer circumference of the inner ring  102 , an inner ring raceway  121  where the rollers  104  move by rolling is formed along a circumferential direction. On the other hand, the outer ring  103  is coaxial with the inner ring  102 , and on an inner circumference thereof, an outer ring raceway  131  where the rollers  104  move by rolling is formed along the circumferential direction to oppose the inner ring raceway  121 . 
     The plural rollers  104  are disposed between the inner ring  102  and the outer ring  103 . These rollers  104  are capable of moving by rolling on the inner ring raceway  121  and the outer ring raceway  131 , and thus, the inner ring  102  and the outer ring  103  is relatively rotatable. 
     The split cage  105  retains the rollers  104  between the inner and outer rings  102  and  103 . The split cage  105  is formed by using, for example, a synthetic resin, such as a polyether ketone (PEEK) resin reinforced by carbon fiber. The split cage  105  may be formed by using a polyamide resin. 
       FIG. 11  is a front view schematically illustrating the roller bearing  101 ,  FIG. 12  is a plan view illustrating a part of the split cage  105  for the roller bearing of  FIG. 11 , and  FIG. 13  is an exploded perspective view of  FIG. 12 . In these drawings, the split cage  105  is provided with pockets  109  for holding the rollers  104  arranged in a ring shape along the circumferential direction, and the split cage  105  includes a plurality of first segments  107  and second segments  108  made of a synthetic resin. The first segments  107  and the second segments  108  are respectively provided in a plural number arranged in a ring shape along the circumferential direction. 
     A prescribed distance is provided between the first segments  107  adjacent to each other in the circumferential direction, and this distance between the adjacent first segments  107  is used as a pocket  109  for holding the roller  104 , and a pocket  109  is also provided inside each first segment  107 . 
     Each first segment  107  is disposed to extend from a first side to a second side along an axial direction of the split cage  105 , and includes a rim portion  122 , a pair of first and second pillar portions  123  and  124 , and a pair of engaging portions  125  and  126 . The rim portion  122  is positioned on the first side along the axial direction, and is formed in a plate shape having planes facing both the sides along the axial direction. The first pillar portion  123  is positioned on a first side along the circumferential direction of the first segment  107 , the second pillar portion  124  is positioned on a second side along the circumferential direction of the first segment  107 , and the pillar portions  123  and  124  extend from end portions along the circumferential direction of the rim portion  122  toward the second side along the axial direction. Each of the pillar portions  123  and  124  is formed in a plate shape having planes facing both the sides along the circumferential direction, and oppose each other along the circumferential direction. A distance between the pillar portions  123  and  124  is set to be the same as the distance between the first segments  107  adjacent to each other along the circumferential direction, and the distance between the pillar portions  123  and  124  is used as the pocket  109  for holding the roller  104 . In other words, the pillar portions  123  and  124  are disposed between the rollers  104  of the roller bearing  101 . The first and second engaging portions  125  and  126  are provided to protrude inward respectively from end portions on the second side along the axial direction of the first and second pillar portions  123  and  124 , and protrude to come close to each other. Incidentally, in the present application, the engaging portions  125  and  126  may include the end portions on the second side along the axial direction of the pillar portions  123  and  124  in some cases. 
     The second segments  108  are provided on the second side along the axial direction of the split cage  105  for connecting the first segments  107  adjacent to each other along the circumferential direction. Each of the second segments  108  is formed in a block shape, having planes facing both sides along the axial direction, the circumferential direction and a radial direction. An appropriate circumferential gap S 1  is formed between the second segments  108  adjacent to each other along the circumferential direction, and the gap S 1  is set to be smaller than a sum of two gaps S 3  along the circumferential direction between the pillar portions  123  and  124  of the first segment and the roller  104 . An end surface disposed on each side along the circumferential direction of the second segment  108  is formed as a contact portion  108   a  capable of coming into contact with the second segment  108  adjacent along the circumferential direction. Incidentally, instead of providing the gap S 1 , the second segments  108  adjacent to each other along the circumferential direction may be precedently in contact with each other in some cases. In end portions along the circumferential direction of each second segment  108 , a pair of first and second engaged portions  127  and  128  opened toward the first side along the axial direction are formed to penetrate along the radial direction. The first engaged portion  127  is disposed in the end portion on the second side along the circumferential direction of the second segment  108 , the second engaged portion  128  is disposed in the end portion on the first side along the circumferential direction of the second segment  108 , and these engaged portions  127  and  128  are engaged by inserting the engaging portions  125  and  126  therethrough from the radial direction, so that the engaging portions  125  and  126  cannot come off from the engaged portions  127  and  128  toward the first side along the axial direction. Specifically, each of the engaged portions  127  and  128  is in an L-shape in a plan view, and includes an axial portion  127   a  or  128   a  and a circumferential portion  127   b  or  128   b . The axial portion  127   a  or  128   a  is formed in a part of the second segment  108  extending from a surface positioned on the first side along the axial direction to a middle portion along the axial direction, so as to be engaged with an end portion on the second side along the axial direction of the pillar portion  123  or  124  of the first segment  107 . The peripheral portion  127   b  or  128   b  is formed in a part extending from the bottom of the axial portions  127   a  or  128   a  outward along the circumferential direction of the second segment  108 , so as to be engaged with the engaging portion  125  or  126  of the first segment  107 . 
     In the exemplified structure described above, for assembling the roller bearing  101 , the end portion on the second side along the axial direction of the first pillar portion  123  and the first engaging portion  125  provided in this end portion of the first segment  107  are engaged with the first engaged portion  127  of the second segment  108 . Besides, the end portion on the second side along the axial direction of the second pillar portion  124  and the second engaging portion  126  provided in this end portion of another first segment  107  adjacent to the former first segment  107  on the first side along the circumferential direction are engaged with the second engaged portion  128  of the second segment  108 . This process is repeated along the circumferential direction, and thus, the first segments  107  adjacent to each other along the circumferential direction are connected by using the second segments  108 , so as to construct the split cage  105 . Besides, in addition, the rollers  104  are respectively mounted into the pockets  109  provided inside the first segments  107  and between the first segments  107  adjacent to each other along the circumferential direction. In this manner, the roller bearing  101  can be assembled. During the assembly, the roller bearing  101  is assembled while alternately connecting the first segments  107  and the second segments  108  forming the split cage  105  as described above, and therefore, the first segments  107  and the second segments  108  are prevented from falling off to scatter during the assembly, and hence the roller bearing  101  can be easily assembled. 
     Furthermore, in power generation by a wind power generation device, when the inner ring  102  of the roller bearing  101  is rotated against the outer ring  103 , the rollers  104  move by rolling on the inner ring  102  and the outer ring  103 , and the split cage  105  retaining the rollers  104  is rotated in the same direction as the inner ring  102 . At this point, large radial load may be applied between the outer ring  103  and the inner ring  102  in, for example, a given circumferential portion in some cases. In such a case, lead and lag of the rollers  104  is increased toward the portion where the radial load is applied, and therefore, the rollers  104  come into contact with the split cage  105 . As a result, tensile load or compressive load is applied to the split cage  105  along the circumferential direction. In such a case, the second segments  108  adjacent to each other along the circumferential direction come close to each other, and their contact portions  108   a  come into contact with each other, and thus, the rigidity and the strength of the split cage  105  is improved. 
     Fifth Embodiment 
       FIGS. 14 and 15  illustrate a fifth embodiment of the present invention, in which the first and second engaging portions  125  and  126  are respectively formed to protrude outward, to be away from each other, from the end portions on the second side along the axial direction of the first and second pillar portions  123  and  124 . The engaged portions  127  and  128  of the second segment  108  are formed correspondingly, and the circumferential portions  127   b  and  128   b  of the engaged portions  127  and  128  are respectively formed in portions extending from bottoms of the axial portions  127   a  and  128   a  inward along the circumferential direction of the second segment  108 . 
     Sixth Embodiment 
       FIG. 16  illustrates a sixth embodiment of the present invention, in which a surface of each pillar portion  123  or  124  of the first segment  107  to be in contact with the roller  104  is formed as a bent surface  116  concaved along the circumferential direction, and thus, the movement of the roller  104  along the radial direction is restrained. 
     When this structure is employed, the roller  104  is fit between the bent surfaces  116  of the pillar portions  123  and  124  disposed on both sides along the circumferential direction of the roller  104  in the first segment  107 , and hence, the movement along the radial direction of the roller  104  can be restrained. 
     Seventh Embodiment 
       FIGS. 17 and 18  illustrate a seventh embodiment of the present invention, in which both end portions along the circumferential direction of the rim portion  122  of the first segment  107  are formed to protrude respectively beyond the pillar portions  123  and  124  in the circumferential direction, and an appropriate circumferential gap S 2  is formed between the rim portions  122  of the first segments  107  adjacent to each other in the circumferential direction. This gap S 2  is set to be smaller than a sum of two gaps S 3  along the circumferential direction between the pillar portions  123  and  124  of the first segment and the roller  104 . The gap S 2  is generally set to be the same as the gap  51  between the second segments  108  adjacent to each other along the circumferential direction, but may not be the same in some cases. Each end surface along the circumferential direction of the rim portion  122  is formed as a contact portion  122   a  to be in contact with each end surface along the circumferential direction of the rim portion  122  of the first segment adjacent along the circumferential direction. Incidentally, in some cases, the rim portions  122  of the first segments  107  adjacent to each other in the circumferential direction may be brought into contact with each other without providing the gap S 2 . 
     In this example, in power generation by a wind power generation device, if lead and lag of the rollers  104  occurs, not only the second segments  108  adjacent to each other along the circumferential direction but also the first segments  107  adjacent to each other along the circumferential direction come close to each other, and their rim portions  122  are in contact with each other, and thus, the rigidity and the strength of the split cage  105  are improved. 
     Besides, in some cases, when the roller  104  moves by rolling, a part of the roller  104  may collide with a corner formed by a portion where the rim portion  122  is connected to the pillar portion  123  or  124 . As a result, stress is concentrated on the corner to deform the pillar portion  123  or  124  or the rim portion  122 . If the gaps S 1  and S 2  are provided, however, the adjacent second segments  108  forming the gap S 1  or the adjacent rim portions  122  forming the gap S 2  can be brought close to or into contact with each other as compared with before the stress concentration. As a result, the stress can be released. 
     Eighth Embodiment 
       FIGS. 19 to 21  illustrate an eighth embodiment of the present invention, in which the engaged portions  127  and  128  of the second segment  108  are formed as recesses opened merely toward the first side along the axial direction and outward along the radial direction. Owing to the recesses, the engaging portions  125  and  126  can be inserted from the radial direction, and the inserted engaging portions  125  and  126  cannot be pulled out in the axial direction. A groove  118  opened toward the first side along the axial direction is formed on an outer side along the radial direction of the second segment  108 . The groove  118  is formed, in the second segment  108 , in a circumferential portion crossing over the engaged portions  127  and  128 , and cross the engaged portions  127  and  128  to communicate with them, and end portions along the circumferential direction of the groove  118  extend outward along the circumferential direction beyond the axial portions  127   a  and  128   a  of the engaged portions  127  and  128 . The groove  118  is positioned on the outside, along the radial direction, of the end portions on the second side along the axial direction of the pillar portions  123  and  124  of the first segment  107  engaged with the engaged portions  127  and  128 , and of the engaging portions  125  and  126 . A stopper  119  of a leaf spring or the like is inserted and attached to the groove  118 , and thus, the engaging portions  125  and  126  and the like are prevented from coming off from the engaged portions  127  and  128  outward in the radial direction. Incidentally, the engaged portions  127  and  128  of the second segment  108  may be formed as recesses opened merely toward the first side along the axial direction and inward along the radial direction, and the groove  118  may be formed not on the outer side along the radial direction but on an inner side along the radial direction of the second segment  108 , and thus, the engaging portions  125  and  126  and the like may be prevented from coming off from the engaged portions  127  and  128  inward in the radial direction. 
     In this example, when the stopper  119  is inserted into the groove  118  of the second segment  108  after engaging the engaging portions  125  and  126  and the like of the first segment  107  with the engaged portions  127  and  128  of the second segment  108 , the engaging portions  125  and  126  and the like can be prevented from coming off from the engaged portions  127  and  128  outward in the radial direction. 
     Ninth Embodiment 
       FIGS. 22 and 23  illustrate a ninth embodiment of the present invention, in which the engaged portions  127  and  128  of the second segment  108  are formed as recesses opened merely toward the first side along the axial direction and outward along the radial direction in the same manner as described above. Owing to the recesses, the engaging portions  125  and  126  can be inserted from the radial direction, and the inserted engaging portions  125  and  126  cannot be pulled out in the axial direction. On an inner surface on the outer side along the circumferential direction of the axial portion  127   a  or  128   a  of each engaged portion  127  or  128 , a projection  120  is integrally formed. The projection  120  is formed on an outside side along the radial direction in the inner surface, and closes about a half area (or an area larger or smaller than the half) of an opening on the outer side along the radial direction of the axial portion  127   a  or  128   a . Besides, the projection  120  is positioned on the outer side along the radial direction of the end portions of the pillar portions  123  and  124  engaged with the engaged portions  127  and  128 , and thus, the end portions of the pillar portions  123  and  124  and the engaging portions  125  and  126  are prevented from coming off from the engaged portions  127  and  128  outward in the radial direction. The projection  120  is in a substantially triangle shape when seen from the axial direction, and has, on its surface on the outer side along the radial direction, an inclined surface  120 a inclined inward along the radial direction toward the inside of the second segment  108  (the side of the opposing projection  120 ) along the circumferential direction. 
     In this example, when the end portions on the second side along the axial direction of the pillar portions  123  and  124  and the engaging portions  125  and  126  of the first segment  107  are to be engaged with the engaged portions  127  and  128 , with the end portion of each of the pillar portions  123  and  124  brought into contact with the inclined surface  120 a of the projection  120 , the projection  120  is pushed inward along the radial direction. Thus, a peripheral portion of the projection  120  of the second segment  108  is elastically deformed to make the projection  120  recede outward along the radial direction, and thus, the end portion of each of the pillar portions  123  and  124  and each of the engaging portions  125  and  126  is allowed to engage with the engaged portion  127  or  128 . After the engagement, the projection  120  and its peripheral portion of the second segment  108  are restored to the original positions due to elastic restoring force, and thus, the engaging portions  125  and  126  and the like are prevented from coming off from the engaged portions  127  and  128  outward along the radial direction. 
     It is noted that the present invention is not limited to the fourth to ninth embodiments described above. For example, each engaged portion may be formed in a dovetail groove shape, with each engaging portion formed in a corresponding shape. 
     Besides, in the fourth to ninth embodiments described above, the present invention is described by assuming the application to a split cage for a roller bearing. The present invention is, however, not limited to this configuration. The present invention may be applied to, for example, a split cage for a rolling bearing such as a ball bearing or a tapered roller bearing. 
     Furthermore, in the fourth to ninth embodiments described above, the present invention is described by assuming the application to a cage for a roller bearing for a main shaft for wind power generation having a large outer diameter, but instead of the application to the wind power generation, the present invention may be applied to a cage for another roller bearing such as a roller bearing for a slewing ring shaft. 
     In addition, it goes without saying that the design can be variously changed or modified within the scope of the appended claims. 
     In other words, the embodiments disclosed herein are merely exemplary, and the present invention is not limited to the above-described embodiments. The scope of the present invention is defined by the appended claims in consideration of the present disclosure, and includes all modifications made within the scope of the appended claims and their equivalents. 
     This application is based upon the prior Japanese patent applications (Japanese Patent Application No. 2013-212535, Japanese Patent Application No. 2013-212549 and Japanese Patent Application No. 2013-212531) filed on Oct. 10, 2014, the entire contents of which are incorporated herein by reference. 
     DESCRIPTION OF REFERENCE SIGNS 
       10 : roller bearing,  11 : inner ring (bearing ring),  12 : outer ring (bearing ring),  13 : rolling element,  14 : cage,  18 : pin (bar-shaped member),  21 : first connecting link (connecting member),  22 : second connecting link (connecting member),  24   a : male screw portion,  25 : nut (female screw member),  101 : roller bearing,  102 : inner ring,  103 : outer ring,  104 : roller,  105 : split cage,  107 : first segment,  108 : second segment,  108   a : contact portion,  109 : pocket,  116 : bent surface,  119 : stopper,  120 : projection,  122 : rim portion,  122   a : contact portion,  123 : first pillar portion,  124 : second pillar portion,  125 : first engaging portion,  126 : second engaging portion,  127 : first engaged portion,  128 : second engaged portion