Title of Invention	CRANKSHAFT SUPPORTING STRUCTURE OF ENGINE, 2- CYCLE, ENGINE AND 4- CYCLE ENGINE
Abstract	A crankshaft supporting structure comprises a con-rod converting linear reciprocating motion to rotary motion, a crankshaft outputting the rotary motion, and a roller bearing supporting the crankshaft, fitted in an engagement hole provided at the large end part of the con-rod, and used as an outer diameter surface guide. The roller bearing comprises a plurality of rollers, and a welded retainer manufactured such that a plate material is cut to a predetermined length, and bent into a cylindrical shape, and its ends are welded. The entire surface of the outer diameter surface 17 of the annular part and the column part 14 of the welded retainer 11 is ground into the shape of a circular arc. When the outer diameter surface 17 of the welded retainer 11 and the inner diameter surface 29 of the engagement hole come in contact with each other, aggressiveness to the engagement hole is alleviated and the abrasion of the engagement hole is reduced.

Title of Invention

CRANKSHAFT SUPPORTING STRUCTURE OF ENGINE, 2- CYCLE, ENGINE AND 4- CYCLE ENGINE

Abstract

A crankshaft supporting structure comprises a con-rod converting linear reciprocating motion to rotary motion, a crankshaft outputting the rotary motion, and a roller bearing supporting the crankshaft, fitted in an engagement hole provided at the large end part of the con-rod, and used as an outer diameter surface guide. The roller bearing comprises a plurality of rollers, and a welded retainer manufactured such that a plate material is cut to a predetermined length, and bent into a cylindrical shape, and its ends are welded. The entire surface of the outer diameter surface 17 of the annular part and the column part 14 of the welded retainer 11 is ground into the shape of a circular arc. When the outer diameter surface 17 of the welded retainer 11 and the inner diameter surface 29 of the engagement hole come in contact with each other, aggressiveness to the engagement hole is alleviated and the abrasion of the engagement hole is reduced.

Full Text	FORM 2 THE PATENT ACT 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10, and rule 13) 1.TITLE OF INVENTION CRANKSHAFT SUPPORTING STRUCTURE OF ENGINE, 2-CYCLE ENGINE AND 4- CYCLE ENGINE 2.APPLICANT(S) a) Name b) Nationality c) Address NTN CORPORATION JAPANESE Company 3-17 KYOMACHIBORI 1-CHOME, NISHI-KU, OSAKA-SHI OSAKA 550-0003 JAPAN 3.PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed : - ENGLISH TRANSLATION VARIFICATIQN CERTIFICATE u/r. 20(3)(b) I, Mr. HIRAL CHANDRAKANT JOSHI, an authorized agent for the applicant, NTN CORPORATION do hereby verify that the content of English translated complete specification filed in pursuance of claiming Japanese Priority No. 2005 - 249717 Dated 30/08/2005 thereof is correct and complete. HIRAL CHANDRAKANT JOSHI AGENT FOR NTN CORPORATION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crankshaft supporting structure of an engine, 2-cycle engine and 4-cycle engine. 2. Description of the Background Art A roller bearing supporting a rotation shaft comprises a plurality of rollers, and a retainer retaining the plurality of rollers. The retainer includes a retainer formed of a resin, a pressed retainer, a machined retainer, a welded retainer, and the like depending on its material and manufacturing method, which are used according to usage or characteristics. Here, one manufacturing method of the above welded retainer will be briefly described hereinafter. First, a band steel plate that is the material of the retainer is pressed into a V-shaped form in section by a roller pressing process. Then, it is punched out to form a pocket having a size in which the roller can be held. Then, it is cut to the circumferential length of the retainer, and the cut steel plate is bent into a cylindrical shape and the end faces of the bent steel plate are connected by welding and the like. Then, the outer diameter surface thereof is ground and heat treated, whereby the welded retainer is completed. As can be seen from the above manufacturing steps, the welded retainer can be manufactured at low cost. However, since the plate-shaped material is bent into the cylindrical shape, it is difficult to make the roundness of the outer diameter surface preferable because it partially has a flat surface and the like, so that it is not suitable for a retainer used as an outer diameter guide. In addition, the roundness is a degree of deviation of a circular part from a geometric circle and the roundness of the retainer is measured at an annular part connecting the column parts between the pockets. Here, the retainer used as the outer diameter guide includes a retainer of a roller bearing used at the small end part or the large end part of a connecting rod (con-rod) in a 2-cycle engine that is a utility engine of a two-wheeled motor vehicle. Fig. 11 is a longitudinal sectional view showing the 2-cycle engine in which roller bearings are used at the small end part and large end part of the con-rod. Referring to Fig. 11, the 2-cycle engine comprises a crankshaft 83 outputting rotary motion, a piston 85 moving in a linear line back and forth by combustion of mixed gas, and a con-rod 84 connecting the crankshaft 83 to the piston 85 and converting the liner reciprocating motion to the rotary motion. The crankshaft 83 rotates around a rotation center shaft 90 and balanced in rotation by a balance weight 91. The con-rod 84 comprises a large end part 93 at the lower part of a linear rod and a small end part 94 at the upper part thereof. The crankshaft 83 is rotatably supported at the large end part 93 of the con-rod 84 through a roller bearing 86 mounted in an -2- engagement hole, and a piston pin 92 connecting the piston 85 to the con-rod 84 is rotatably supported by a roller bearing 86 mounted in an engagement hole. The mixed gas of gasoline and lubricant oil is sent from an inlet 87 to a crank chamber 82 and then led to a combustion chamber 89 arranged at the upper part of a cylinder 81 according to the vertical motion of the piston 85. The exhaust gas is discharged from an exhaust hole 88. As the roller bearings mounted in the engagement holes provided at the small end part and the large end part of the con-rod to support the piston pin and the crankshaft, a needle roller bearing that can receive high load in spite of its small projected area and highly rigid is used. Here, the needle roller bearing comprises a plurality of needle rollers and a retainer retaining the plurality of rollers. The retainer comprises pockets for holding the needle rollers and the interval of the needle rollers is retained at a column part positioned between the pockets. Here, the needle roller bearings at the small end part and the large end part of the con-rod are used as outer diameter guides in which the outer diameter surfaces of the retainers are aggressively in contact with the inner diameter surfaces of the engagement holes provided at the small end part and the large end part in order to reduce the load applied to the needle roller bearing due to the rotating motion and revolving motion of the needle rollers. As the retainer used as the outer diameter guide, a machined retainer whose roundness of an outer diameter surface is preferable is used. The machined retainer used as the outer diameter surface guide is disclosed in Japanese Unexamined Patent Publication No. 2000-240662, for example. The machined retainer used as the outer diameter surface guide is manufactured by grinding a cylindrical pipe material. Since the machined retainer manufactured by the grinding step is expensive, its manufacturing cost becomes high. Thus, it is considered that a welded retainer that can be manufactured at low cost is used as the retainer as the outer diameter guide. However, according to the retainer used as the outer diameter guide, the outer diameter surface of the retainer is in contact with the inner diameter surface of the housing and the like. Therefore, when the roundness of the retainer is not preferable or when there is a flat surface in the outer diameter surface of the retainer, a certain part is not in contact with the inner diameter surface of the housing, so that a contact area is reduced. As a result, a surface pressure from the welded retainer to the housing is increased, and aggressiveness to the housing is increased, so that the housing is considerably worn. Here, a description will be made of the outer diameter configuration of the welded retainer manufactured by the above conventional manufacturing method. Fig. 12 is a sectional view showing a part of the welded retainer 101 containing annular parts -3- 102a and 102b manufactured by the conventional manufacturing method, which is cut in the direction along the shaft. Referring to Fig. 12, the welded retainer 101 comprises the pair of annular parts 102a and 102b, a plurality of column parts 103 connecting the pair of annular parts 102a and 102b so that pockets to hold the rollers (not shown) are provided between them. A click-shaped preventing part 106 for preventing the roller from escaping toward the outer diameter side is formed at an end 104 of the column part 103 on the side close to the annular part 102a or 102b and close to an outer diameter surface 105. In addition, Fig. 13 is a view taken from the direction of X in Fig. 12, m which the outer diameter surface 105 of the welded retainer 101 is seen from the outer side of the diameter direction. Referring to Fig. 13, a flat surface 107 exists at the center of the preventing part 106 for preventing the roller from escaping toward the outer diameter side on the side of the outer diameter surface 105. This is for the following reason. In the conventional manufacturing method, after the cut steel plate is bent into the cylindrical shape, the outer diameter surface 105 at the end 104 of the column part 103 which is not continued in the circumferential direction is flat without forming the circular arc of the cylindrical shape. Although the outer diameter surface 105 of the welded retainer 101 is ground at a subsequent grinding step, this step is performed with the purpose of rounding a corner 108 of the end 104 of the column part 103 to prevent an oil film from being cut due to the corner 108 on the side of the outer diameter surface 105. Therefore, although the corner 108 is rounded at the grinding step, the flat surface part 107 positioned at the center of the preventing part 106 for preventing the roller from escaping toward the outer diameter side is not ground into the circular arc shape, so that the flat surface part 107 is still flat after the grinding step. In addition, Fig. 14 is a sectional view showing the column part 103 comprising the end 104 taken along Y-Y in Fig. 12, which is cut in the diameter direction. Referring to Fig. 14, when the welded retainer 101 is the outer diameter guide type, since the flat surface part 107 exists, it is not in contact with the inner diameter surface 109 of the housing (not shown) shown by a dashed line in Fig. 14. In this case, since the contact area between the inner diameter surface of the housing and the outer diameter surface 105 of the welded retainer 101 is small, the surface pressure from the welded retainer 101 to the housing is increased. As a result, aggressiveness of the welded retainer 101 to the housing becomes high and the housing is considerably worn. When the roller bearing uses this welded retainer as the retainer used as the outer diameter guide in the large end part of the con-rod, the engagement hole provided at the large end part of the con-rod is considerably worn, so that the life of the crankshaft supporting structure and the like is shortened. -4- SUMMARY OF THE INVENTION It is an object of the present invention to provide a crankshaft supporting structure of an engine, a 2-cycle engine and 4-cycle engine having a long life span. A crankshaft supporting structure according to the present invention comprises a con-rod converting linear reciprocating motion to rotary motion, a crankshaft outputting the rotary motion, and a roller bearing supporting the crankshaft, fitted in an engagement hole provided at the large end part of the con-rod, and used as an outer diameter surface guide. The roller bearing comprises a plurality of rollers, and a welded retainer manufactured such that a plate material is cut to a predetermined length, and bent into a cylindrical shape and its ends are welded. The welded retainer comprises a pair of annular parts, and column parts connecting the pair of annular parts so that pockets for housing the rollers are formed. Here, the entire surface of the outer diameter surface of the annular part and the column part is ground into the shape of a circular arc. According to the above constitution, the surface other than the circular arc shape such as a flat surface is not contained in the outer diameter surface of the annular part and the column part, in the welded retainer provided in the roller bearing contained in the crankshaft supporting structure. Therefore, when used as the outer diameter guide, the entire of the annular part and the column part of the welded retainer is in contact with the outer diameter surface of the engagement hole provided at the large end part of the con-rod, so that the contact area can be increased. As a result, the surface pressure from the welded retainer to the engagement hole can be reduced and the aggressiveness of the welded retainer to the engagement hole is alleviated, so that the abrasion of the engagement hole can be reduced. In addition, since the welded retainer is light in weight, the aggressiveness to the engagement hole due to centrifugal force generated by the rotary motion can be alleviated. In addition, a crankshaft supporting structure according to the present invention comprises a con-rod converting linear reciprocating motion to rotary motion, a crankshaft outputting the rotary motion, and a roller bearing supporting the crankshaft, fitted in an engagement hole provided at the large end of the con-rod, and used as an outer diameter surface guide. The roller bearing comprises a plurality of rollers, and a welded retainer manufactured such that a plate material is cut to a predetermined length, and bent into a cylindrical shape, and its ends are welded. In addition, the welded retainer comprises a pair of annular parts, and column parts connecting the pair of annular parts so that pockets for housing the rollers are formed. Here, the roundness of the outer diameter surface of the welded retainer is not more than 80μm. When the welded retainer provided in the roller bearing in the crankshaft supporting structure has the roundness of 80μm or less as the outer diameter guide, -5- the aggressiveness of the welded retainer to the engagement hole can be alleviated and the abrasion of the engagement hole can be reduced. Preferably, the roundness of the outer diameter of the welded retainer is not less than 20μm. Although the roundness is improved by grinding the outer diameter surface, when it is defined as described above, the roundness is not unnecessarily improved, so that manufacturing cost can be lowered. More preferably, a corner slope portion is provided at the corner of the column part on the side of the outer diameter surface. Thus, during the rotation of the welded retainer, the oil film is prevented being cut at the corner of the column part on the side of the outer diameter surface, so that lubricity can be improved and the aggressiveness toward the engagement hole can be alleviated. Further preferably, a plating process is performed for the welded retainer. Thus, the surface of the welded retainer is protected and the lubricity can be improved and the aggressiveness toward the engagement hole can be alleviated. Further preferably, carburized quenching and tempering processes are performed for the welded retainer. Thus, the hardness of the welded retainer can be enhanced. According to another aspect of the present invention, a 2-cycle engine has any crankshaft supporting structure described above. According to still another aspect of the present invention, a 4-cycle engine has any crankshaft supporting structure described above. Thus, the 2-cycle engine and 4-cycle engine can alleviate the aggressiveness toward the inner diameter surface of the engagement hole provided at the large end part of the con-rod and reduce the abrasion of the engagement hole. According to the present invention, the aggressiveness of the welded retainer toward the engagement hole can be alleviated and the abrasion of the engagement hole can be reduced. As a result, the crankshaft supporting structure, the 2-cycle engine and the 4-cycle engine can elongate their life span. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view showing a part of a welded retainer 11 containing an end 16 of a column part 14, which is cut in the diameter direction; Fig. 2 is a sectional view showing an essential part of a 2-cycle engine according to one embodiment of the present invention; Fig. 3 is a sectional view showing a part of the welded retainer 11 containing the column part 14, which is cut in the axial direction; Fig. 4 is a flowchart showing manufacturing steps of the welded retainer 11; -6- Fig. 5 is a schematic view showing representative steps in the steps shown in Fig. 4; Fig. 6 is a configuration curve of an outer diameter surface 105 of a column part 103 in a welded retainer 101 manufactured by a conventional grinding step shown in Fig. 14; Fig. 7 is a configuration curve of an outer diameter surface of the column part 14 in the welded retainer 11 shown in Fig. 1; Fig. 8A is a sectional view showing a part of a welded retainer according to another embodiment in which a column part is linear. Fig. 8B is a sectional view showing a part of a welded retainer according to another embodiment in which a column part is V-shaped and an end is bent in the direction perpendicular to the shaft; Fig. 8C is a sectional view showing a part of a welded retainer according to another embodiment in which a column part is V-shaped and an end is bent in the direction along the shaft; Fig. 9 is a schematic view showing a savant testing machine 41 for performing comparative evaluation of an abrasion amount; Fig. 10 is a graph showing a relation between the roundness of the outer diameter surface of the welded retainer and the abrasion amount of the housing; Fig. 11 is a longitudinal sectional view showing a 2-cycle engine using needle roller bearings at the large end part and small end part of a con-rod; Fig. 12 is a sectional view showing a part of the conventional welded retainer 101 containing annular parts 102a and 102b, which is cut in the direction along the shaft; Fig. 13 is a view showing a part of the conventional welded retainer 101 taken from the direction of an arrow X in Fig. 12; and Fig. 14 is a sectional view showing the conventional welded retainer 101 containing an end 106 in Y-Y section in Fig. 12, which is cut in the diameter direction. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings hereinafter. Fig. 2 is a sectional view showing an essential part of a 2-cycle engine according to one embodiment of the present invention. Referring to Fig. 2, a 2-cycle engine 51 comprises a piston (not shown) moving in a straight line back and forth by combustion of mixed gas, a crankshaft 52 outputting rotary motion, and a con-rod 53 connecting the piston and the crankshaft 52 to convert the linear back-and-forth movement to the rotary motion. The piston is connected to the small end -7- part of the con-rod 53 by a piston pin 54 through a roller bearing 55. In addition, the crankshaft 52 is connected to the large end part of the con-rod 53 through a roller bearing 56. The roller bearing 55 to support the piston pin 54 is fitted in an engagement hole provided at the small end part of the con-rod 53, whereby a piston pin supporting structure is formed. Similarly, the roller bearing 56 to support the crankshaft 52 is fitted in an engagement hole provided at the large end part of the con-rod 53, whereby a crankshaft supporting structure is formed. The roller bearing 56 comprises a plurality of rollers and a welded retainer for retaining the rollers. The welded retainer is used as an outer diameter guide in which the inner diameter surface of the engagement hole provided in the large diameter part of the con-rod 53 and the outer diameter surface of the welded retainer are in contact with each other. In addition, the roller bearing 55 fitted in the engagement hole provided in the small diameter part of the con-rod 53 has the same constitution. Fig. 3 is a sectional view showing a part of the welded retainer 11 provided in the roller bearing 56 contained in the crankshaft supporting structure according to one embodiment of the present invention. Referring to Fig. 3, the welded retainer 11 comprises a pair of annular parts 13a and 13b, a plurality of column parts 14 connecting the pair of annular parts so that pockets to hold the roller 12 are provided between them. The column part 14 has a V-shaped configuration in section in which its center part 15 is bent toward the inner side of the diameter direction. The side of an inner diameter surface 18 of the center part 15 of the column part 14 is narrow in width in the circumferential direction, whereby a preventing part for preventing the roller from escaping toward the inner diameter side is formed. In addition, an end 16 of the column part comprises a click as a preventing part for preventing the roller from escaping toward the outer diameter side, on the side of an outer diameter surface 17. A manufacturing method of the welded retainer 11 will be described hereinafter. Fig 4 is a flowchart showing manufacturing steps for manufacturing the welded retainer 11. In addition, Fig. 5 is a schematic view showing representative steps in the steps shown in Fig. 4. The manufacturing method of the welded retainer 11 will be described with reference to Figs. 3,4 and 5. First, a V-shaped form pressing step for pressing a steel plate of the material of the welded retainer 11 in its band steel state (Fig. 5(a)) is performed so that its sectional configuration may become V shape (Fig. 4A, Fig. 5(b)). Here, the V shape means that when the welded retainer 11 is bent into a cylindrical shape, the center of the band steel and the end of the band steel are different in level in the diameter direction. The V-shaped form pressing step is performed by sandwiching the steel plate between a molding roller press comprising an upper mold whose center is projected and a lower mold whose center is recessed and pressing it. -8- Then, a pocket punching-out step for forming pockets to hold the rollers is performed for the bent band steel after the V-shaped form pressing step (Fig. 4(B), Fig. 5(c)). The pocket punching-out step is performed by pressing a blade edge to the band steel along a pocket configuration with a punch having a punching blade and punching it out. Then, a click forming step for forming the click for preventing the roller from escaping toward the outer diameter side (Fig. 4(C)) is performed. The click forming step is performed by fixing the end 16 of the column part 14 on the side of the outer diameter surface 17 and pressing the end by a press from the side of the inner diameter surface 18, so that the width dimension of the end 16 on the side of the outer diameter surface 17 is enlarged in the circumferential direction. Then, a cutting step for cutting the band steel to be the circumferential length of the welded retainer 11 as a predetermined length is performed (Fig. 4(D)), and a bending step for bending the cut steel plate into the cylindrical shape is performed (Fig. 4(E), Fig. 5(d)). Then, a welding step for connecting both end surfaces of the bent steel plate is performed (Fig. 4(F)). Then, a first grinding step for grinding the outer diameter surface 17 of the cylindrical welded retainer 11 is performed (Fig. 4(G)). Here, in the cylindrically bent steel plate, a smooth cylindrical surface is formed along the outer diameter surface 17 at the annular parts 13a and 13b continuously provided in the circumferential direction, but the outer diameter surface 17 at the end 16 of the column part 14 that is not continuously provided in the circumferential direction is flat without forming the circular arc that constitutes the cylinder. The first grinding step is performed for rounding an outer corner positioned at the end of the column part 14 in the width direction. Then, carburized quenching and tempering treatments are performed as a heat treatment step (Fig. 4(H)). By this heat treatment step, the hardness of the welded retainer is improved. Here, the heat treatment step is not limited to the carburized quenching and tempering treatments, and another heat treatment step such as a carbonitriding treatment or a liquid quenching treatment may be performed according to usage. Then, a second grinding step for grinding the outer diameter surface 17 of the welded retainer 11 again is performed (Fig. 4(1)). By the second grinding step, the whole surface of the outer diameter surface 17 of the annular parts 13a and 13b and the column part 14 of the welded retainer 11 is ground to be a circular arc. In addition, by this step, the roundness of the outer diameter surface 17 becomes 80μm or less. More specifically, by this step, a flat part positioned in the center of the outer diameter surface 17 at the end 16 of the column part 14 is ground to be eliminated. Then, a surface sloping process for the corner of the outer diameter surface at the end 16 of the column part 14 is performed (Fig. 4(J)). The surface sloping process is a -9- process for grinding the corner larger than a normal chamfer. Thus, the oil film of lubricant oil is prevented from being cut during rotation. This step is performed by a tumbling process. Then, after a cleaning step, the surface of the welded retainer 11 is plated (Fig. 4(K)). The plating process may be a copper plating process or copper and silver plating process. By this plating process, the surface of the welded retainer is protected and a lubricating property is improved, so that aggressiveness to the housing can be alleviated. Thus, the welded retainer 11 is manufactured (Fig. 5(e)). In addition, when the plurality of rollers are incorporated in the pockets of the above welded retainer 11, the roller bearing is completed. In addition, when the roller bearing manufactured as described above is fitted in the engagement hole provided at the large diameter part of the con-rod, the crankshaft supporting structure is completed, and the 2-cycle engine is manufactured using such crank shaft supporting structure. A description will be made of a case where the roller bearing comprising the welded retainer 11 manufactured by the above method is incorporated in the inner diameter surface of the engagement hole provided at the large end part of the con-rod hereinafter. Fig. 1 is a sectional view showing a part of the section of the end 16 of the column part 14 containing a preventing part 19 for preventing the roller from escaping toward its outer diameter side, which is cut in the diameter direction. Referring to Fig. 1, a corner 20 of the end 16 of the column part 14 has been rounded by the first grinding step and a corner slope portion has been provided. A center part 21 on the outer diameter surface 17 at the end 16 of the column part 14 is not flat but has been ground into the circular arc by the second grinding step. In addition, the roundness of the outer diameter surface 17 is not more than 80μm through the first and second grinding steps. Here, Fig. 6 shows the outer diameter outline of the outer diameter surface 105 when the end 104 of the column part 103 of the conventional welded retainer 101 shown in Fig. 14 is cut in the diameter direction, and Fig. 7 shows the outer diameter outline of the outer diameter surface 17 when the end 16 of the column part 14 of the welded retainer 11 shown in Fig. 1 is cut in the diameter direction. In Fig. 6 and 7, the vertical side of one square is 0.2mm and the lateral side of one square is 0.2mm. In addition, in Figs. 6 and 7, when the welded retainer is bent into the cylindrical shape, the ideal curve of the outer diameter surface in an ideal circular arc is shown by a curve 22. Referring to Figs. 6 and 7, according to an outer diameter outline 23 of the conventional welded retainer 101, there is almost no difference between a center part 24 and an end 25 in the diameter direction and it is flat. In addition, a dimensional difference between the end 25 and the ideal configuration curve 22 in the diameter direction is big. -10- Meanwhile, according to the outer diameter outline 26 of the welded retainer 11 shown in Fig. 1, its dimension in the diameter direction is gradually increased from an end 28 to a center 27, so that it forms a circular arc. In addition, the outer diameter outline 26 overlaps with the ideal configuration curve 22 at not only the center 27 and the end 28 but also almost other parts, which form an ideal circular arc. Referring to Fig. 1 again, when the welded retainer 11 having the outer diameter surface 17 that is not flat but forms the ideal circular arc is used as an outer diameter guide, an inner diameter surface 29 of an engagement hole (not shown) indicated by a dashed line in Fig. 1 and the whole surface of the outer diameter surface 17 of the welded retainer 11 are in contact with each other. Therefore, the contact area thereof can be large and the surface pressure from the welded retainer 11 to the inner surface of the engagement hole can be reduced. As a result, aggressiveness to the engagement hole can be alleviated and the abrasion of the engagement hole can be reduced. The crankshaft supporting structure and the 2-cycle engine comprising the con-rod containing the engagement hole in which the abrasion is reduced can implement a long life. In addition, the above embodiment can be applied to a case where the 2-cycle engine is replaced with a 4-cycle engine. As described above, the crankshaft supporting structure, the 2-cycle engine and the 4-cycle engine can elongate their life span. In addition, although the sectional configuration of the welded retainer is V shape in the above embodiment, the present invention is not limited to this. For example, a welded retainer may have another sectional configuration. Each of Figs. 8A, 8B and 8C is a sectional view showing a part of a welded retainer according to another embodiment of the present invention. Referring to Fig. 8A, the center of a column part 32 may not be bent in a welded retainer 31 and the sectional configuration of the column part 32 may be linear. Referring to Fig. 8B, a welded retainer 33 may be an M-type retainer in which the center of a column part 34 is bent to the inner side of the diameter direction into a V shape and an end 35 is bent toward the inner side of the diameter direction so as to be perpendicular to the shaft. Furthermore, referring to Fig. 8C, a welded retainer 36 may be such that the center of a column part 37 is bent toward the inner side of the diameter direction into a V shape and an end 38 is bent toward the inner side of the diameter direction so as to be along the shaft. Here, a test for comparatively evaluating an abrasion amount was performed for the welded retainer having the configuration shown in Fig. 8B. Fig. 9 is a schematic view showing a savant testing machine for comparatively evaluating the abrasion amount. Referring to Fig. 9, a savant testing machine 41 comprises a retainer mounting part 42 in which the welded retainer is mounted, and a loading part 43 for applying constant load. The loading part 43 applies predetermined load to the retainer mounting part 42 by a spring 44, and its loading amount is measured by a load cell 45. The retainer mounting part 42 is filled with lubricant oil and it is kept at -11- a constant temperature by a cartridge heater 46. A housing is provided in the retainer mounting part 42 and when the retainer as a test piece is mounted on a retainer mounting hole 47, the inner diameter surface of the housing and the outer diameter surface of the retainer are in contact with each other. The mounted retainer is fixed by a retaining pin 48, and after the housing and the retainer slide for a predetermined time while they are in contact with each other, the abrasion amount of the housing is measured. In addition, the test condition is as follows. The result of the test is shown n Fig. 10. Test piece size : inner diameter Ø 26mm x outer diameter Ø 33mm x width 13.8mm Plating process : performed The number of tests : 4 times Fig. 10 is a graph showing a relation between the roundness of the outer diameter surface of the welded retainer and the abrasion amount of the housing in which a lateral axis shows the roundness of the outer diameter surface of the retainer, and a vertical axis shows the abrasion amount of the housing. Referring to Fig. 10, when the roundness of the outer diameter surface is not less than l00μm, the housing is worn at least 3μm, and some is worn up to 4μm. Meanwhile, when the roundness of the outer diameter surface is not more than 80μm, the abrasion amount of the housing is reduced and it is up to about half of the above. In addition, as long as it is not more than 80μm, even when it is 20μm, the abrasion amount of the housing is about the same. Here, in order to reduce the roundness of the outer diameter surface of the welded retainer to 20μm or less, it is necessary to increase the number of grinding steps and increase the ground amount. In this case, as the number of steps is increased and the ground amount is increased, the manufacturing cost is increased and the hardness of the welded retainer is reduced, so that it is preferable that the roundness is not less than 20μm. In addition, although the grinding steps are performed two times in the above embodiment, the present invention is not limited to this. For example, at one grinding step, the corner of a column part on the outer diameter side may be rounded and the outer diameter surface of the annular part and the column part of a welded retainer may be ground so that the roundness of the outer diameter surface may become 80μm or less. Furthermore, the grinding steps may be performed three times or more to grind the outer diameter surface of the annular part and the column part of a welded retainer to be a circular arc so that the roundness of the outer diameter surface may be 80μm or less. In addition, although the roller bearing incorporated in the crankshaft supporting structure comprises the plurality of rollers and the welded retainer in the above embodiment, the present invention is not limited to this. For example, the roller bearing may comprise a shell type outer ring. In this case, since the welded retainer is used as the outer diameter guide, the outer diameter surface of the welded retainer is in contact with the inner diameter surface of the shell type outer ring and -12- the inner diameter surface of the shell type outer ring is attacked. However, when the welded retainer has the above constitution, since the aggressiveness to the inner diameter surface of the shell type outer ring can be alleviated, the shell type outer ring is not likely to be worn, that is, the crankshaft supporting structure and the like can elongate its life span. In addition, although the preventing part for preventing the roller from escaping toward the inner diameter side is formed by performing the V-shaped form molding step and the preventing part for preventing the roller from escaping toward the outer diameter side is formed by forming the click in the above embodiment, the present invention is not limited to this. The preventing part for preventing the roller from escaping toward the inner and outer diameter sides may be formed by another method. Although the embodiments of the present invention have been described with reference to the drawings in the above, the present invention is not limited to the above-illustrated embodiments. Various kinds of modifications and variations may be added to the illustrated embodiments within the same or equal scope of the present invention. Since the crankshaft supporting structure, the 2-cycle engine, and the 4-cycle engine according to the present invention can reduce the abrasion of the inner diameter surface of the engagement hole provided at the large end part of the con-rod, they can be effectively used as the crankshaft supporting structure having a long life and the 2-cycle engine and 4-cycle engine having the above crankshaft supporting structure. -13- WE CLAIM : 1. A crankshaft supporting structure of an engine, comprising: a con-rod converting linear reciprocating motion to rotary motion; a crankshaft outputting the rotary motion; and a roller bearing supporting said crankshaft, fitted in an engagement hole provided at the large end part of said con-rod, and used as an outer diameter surface guide, wherein said roller bearing comprises a plurality of rollers, and a welded retainer manufactured such that a plate material is cut to a predetermined length, and bent into a cylindrical shape, and its ends are welded, said welded retainer comprises a pair of annular parts, and column parts connecting the pair of annular parts so that pockets for housing said rollers are formed, and the entire surface of the outer diameter surface of said annular part and said column part is ground into the shape of a circular arc. 2. A crankshaft supporting structure of an engine, comprising: a con-rod converting linear reciprocating motion to rotary motion; a crankshaft outputting the rotary motion; and a roller bearing supporting said crankshaft, fitted in an engagement hole provided at the large end part of said con-rod, and used as an outer diameter surface guide, wherein said roller bearing comprises a plurality of rollers, and a welded retainer manufactured such that a plate material is cut to a predetermined length, and bent into a cylindrical shape, and its ends are welded, said welded retainer comprises a pair of annular parts, and column parts connecting the pair of annular parts so that pockets for housing said rollers are formed, and the roundness of the outer diameter surface of said welded retainer is not more than 80μm. 3. The crankshaft supporting structure according to claim 2, wherein the roundness of the outer diameter of said welded retainer is not less than 20μm. 4. The crankshaft supporting structure according to claim 1, wherein a corner slope portion is provided at the corner of said column part on the side of the outer diameter surface. 5. The crankshaft supporting structure according to claim 1, wherein a plating process is performed for said welded retainer. 6. The crankshaft supporting structure according to claim 1, wherein carburized quenching and tempering processes are performed for said welded retainer. -14- 7. A 2-cycle engine having the crankshaft supporting structure according to claim 1. 8. A 4-cycle engine having the crankshaft supporting structure according to claim 1. Dated this 23rd day of August, 2006 HIR AL CHANDRAKANT JOSHI AGENT FOR BAYER HEALTHCARE LLC -15- ABSTRACT A crankshaft supporting structure comprises a con-rod converting linear reciprocating motion to rotary motion, a crankshaft outputting the rotary motion, and a roller bearing supporting the crankshaft, fitted in an engagement hole provided at the large end part of the con-rod, and used as an outer diameter surface guide. The roller bearing comprises a plurality of rollers, and a welded retainer manufactured such that a plate material is cut to a predetermined length, and bent into a cylindrical shape, and its ends are welded. The entire surface of the outer diameter surface 17 of the annular part and the column part 14 of the welded retainer 11 is ground into the shape of a circular arc. When the outer diameter surface 17 of the welded retainer 11 and the inner diameter surface 29 of the engagement hole come in contact with each other, aggressiveness to the engagement hole is alleviated and the abrasion of the engagement hole is reduced. To, The Controller of Patents The Patent Office Mumbai. -16-

Full Text

FORM 2
THE PATENT ACT 1970 (39 of 1970)

&

The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10, and rule 13)
1.TITLE OF INVENTION
CRANKSHAFT SUPPORTING STRUCTURE OF ENGINE, 2-CYCLE ENGINE AND 4-
CYCLE ENGINE

2.APPLICANT(S)
a) Name
b) Nationality
c) Address

NTN CORPORATION
JAPANESE Company
3-17 KYOMACHIBORI 1-CHOME,
NISHI-KU, OSAKA-SHI
OSAKA 550-0003
JAPAN

3.PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed : -

ENGLISH TRANSLATION VARIFICATIQN
CERTIFICATE u/r. 20(3)(b)
I, Mr. HIRAL CHANDRAKANT JOSHI, an authorized agent for the applicant, NTN CORPORATION do hereby verify that the content of English translated complete specification filed in pursuance of claiming Japanese Priority No. 2005 - 249717 Dated 30/08/2005 thereof is correct and complete.

HIRAL CHANDRAKANT JOSHI AGENT FOR
NTN CORPORATION

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a crankshaft supporting structure of an engine, 2-cycle engine and 4-cycle engine.
2. Description of the Background Art
A roller bearing supporting a rotation shaft comprises a plurality of rollers, and a retainer retaining the plurality of rollers. The retainer includes a retainer formed of a resin, a pressed retainer, a machined retainer, a welded retainer, and the like depending on its material and manufacturing method, which are used according to usage or characteristics.
Here, one manufacturing method of the above welded retainer will be briefly described hereinafter. First, a band steel plate that is the material of the retainer is pressed into a V-shaped form in section by a roller pressing process. Then, it is punched out to form a pocket having a size in which the roller can be held. Then, it is cut to the circumferential length of the retainer, and the cut steel plate is bent into a cylindrical shape and the end faces of the bent steel plate are connected by welding and the like. Then, the outer diameter surface thereof is ground and heat treated, whereby the welded retainer is completed.
As can be seen from the above manufacturing steps, the welded retainer can be manufactured at low cost. However, since the plate-shaped material is bent into the cylindrical shape, it is difficult to make the roundness of the outer diameter surface preferable because it partially has a flat surface and the like, so that it is not suitable for a retainer used as an outer diameter guide. In addition, the roundness is a degree of deviation of a circular part from a geometric circle and the roundness of the retainer is measured at an annular part connecting the column parts between the pockets.
Here, the retainer used as the outer diameter guide includes a retainer of a roller bearing used at the small end part or the large end part of a connecting rod (con-rod) in a 2-cycle engine that is a utility engine of a two-wheeled motor vehicle.
Fig. 11 is a longitudinal sectional view showing the 2-cycle engine in which roller bearings are used at the small end part and large end part of the con-rod. Referring to Fig. 11, the 2-cycle engine comprises a crankshaft 83 outputting rotary motion, a piston 85 moving in a linear line back and forth by combustion of mixed gas, and a con-rod 84 connecting the crankshaft 83 to the piston 85 and converting the liner reciprocating motion to the rotary motion. The crankshaft 83 rotates around a rotation center shaft 90 and balanced in rotation by a balance weight 91.
The con-rod 84 comprises a large end part 93 at the lower part of a linear rod and a small end part 94 at the upper part thereof. The crankshaft 83 is rotatably supported at the large end part 93 of the con-rod 84 through a roller bearing 86 mounted in an
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engagement hole, and a piston pin 92 connecting the piston 85 to the con-rod 84 is rotatably supported by a roller bearing 86 mounted in an engagement hole.
The mixed gas of gasoline and lubricant oil is sent from an inlet 87 to a crank chamber 82 and then led to a combustion chamber 89 arranged at the upper part of a cylinder 81 according to the vertical motion of the piston 85. The exhaust gas is discharged from an exhaust hole 88.
As the roller bearings mounted in the engagement holes provided at the small end part and the large end part of the con-rod to support the piston pin and the crankshaft, a needle roller bearing that can receive high load in spite of its small projected area and highly rigid is used. Here, the needle roller bearing comprises a plurality of needle rollers and a retainer retaining the plurality of rollers. The retainer comprises pockets for holding the needle rollers and the interval of the needle rollers is retained at a column part positioned between the pockets. Here, the needle roller bearings at the small end part and the large end part of the con-rod are used as outer diameter guides in which the outer diameter surfaces of the retainers are aggressively in contact with the inner diameter surfaces of the engagement holes provided at the small end part and the large end part in order to reduce the load applied to the needle roller bearing due to the rotating motion and revolving motion of the needle rollers.
As the retainer used as the outer diameter guide, a machined retainer whose roundness of an outer diameter surface is preferable is used. The machined retainer used as the outer diameter surface guide is disclosed in Japanese Unexamined Patent Publication No. 2000-240662, for example.
The machined retainer used as the outer diameter surface guide is manufactured by grinding a cylindrical pipe material. Since the machined retainer manufactured by the grinding step is expensive, its manufacturing cost becomes high.
Thus, it is considered that a welded retainer that can be manufactured at low cost is used as the retainer as the outer diameter guide.
However, according to the retainer used as the outer diameter guide, the outer diameter surface of the retainer is in contact with the inner diameter surface of the housing and the like. Therefore, when the roundness of the retainer is not preferable or when there is a flat surface in the outer diameter surface of the retainer, a certain part is not in contact with the inner diameter surface of the housing, so that a contact area is reduced. As a result, a surface pressure from the welded retainer to the housing is increased, and aggressiveness to the housing is increased, so that the housing is considerably worn.
Here, a description will be made of the outer diameter configuration of the welded retainer manufactured by the above conventional manufacturing method. Fig. 12 is a sectional view showing a part of the welded retainer 101 containing annular parts
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102a and 102b manufactured by the conventional manufacturing method, which is cut in the direction along the shaft. Referring to Fig. 12, the welded retainer 101 comprises the pair of annular parts 102a and 102b, a plurality of column parts 103 connecting the pair of annular parts 102a and 102b so that pockets to hold the rollers (not shown) are provided between them. A click-shaped preventing part 106 for preventing the roller from escaping toward the outer diameter side is formed at an end 104 of the column part 103 on the side close to the annular part 102a or 102b and close to an outer diameter surface 105.
In addition, Fig. 13 is a view taken from the direction of X in Fig. 12, m which the outer diameter surface 105 of the welded retainer 101 is seen from the outer side of the diameter direction. Referring to Fig. 13, a flat surface 107 exists at the center of the preventing part 106 for preventing the roller from escaping toward the outer diameter side on the side of the outer diameter surface 105. This is for the following reason.
In the conventional manufacturing method, after the cut steel plate is bent into the cylindrical shape, the outer diameter surface 105 at the end 104 of the column part 103 which is not continued in the circumferential direction is flat without forming the circular arc of the cylindrical shape.
Although the outer diameter surface 105 of the welded retainer 101 is ground at a subsequent grinding step, this step is performed with the purpose of rounding a corner 108 of the end 104 of the column part 103 to prevent an oil film from being cut due to the corner 108 on the side of the outer diameter surface 105. Therefore, although the corner 108 is rounded at the grinding step, the flat surface part 107 positioned at the center of the preventing part 106 for preventing the roller from escaping toward the outer diameter side is not ground into the circular arc shape, so that the flat surface part 107 is still flat after the grinding step.
In addition, Fig. 14 is a sectional view showing the column part 103 comprising the end 104 taken along Y-Y in Fig. 12, which is cut in the diameter direction. Referring to Fig. 14, when the welded retainer 101 is the outer diameter guide type, since the flat surface part 107 exists, it is not in contact with the inner diameter surface 109 of the housing (not shown) shown by a dashed line in Fig. 14. In this case, since the contact area between the inner diameter surface of the housing and the outer diameter surface 105 of the welded retainer 101 is small, the surface pressure from the welded retainer 101 to the housing is increased. As a result, aggressiveness of the welded retainer 101 to the housing becomes high and the housing is considerably worn.
When the roller bearing uses this welded retainer as the retainer used as the outer diameter guide in the large end part of the con-rod, the engagement hole provided at the large end part of the con-rod is considerably worn, so that the life of the crankshaft supporting structure and the like is shortened.
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SUMMARY OF THE INVENTION
It is an object of the present invention to provide a crankshaft supporting structure of an engine, a 2-cycle engine and 4-cycle engine having a long life span.
A crankshaft supporting structure according to the present invention comprises a con-rod converting linear reciprocating motion to rotary motion, a crankshaft outputting the rotary motion, and a roller bearing supporting the crankshaft, fitted in an engagement hole provided at the large end part of the con-rod, and used as an outer diameter surface guide. The roller bearing comprises a plurality of rollers, and a welded retainer manufactured such that a plate material is cut to a predetermined length, and bent into a cylindrical shape and its ends are welded. The welded retainer comprises a pair of annular parts, and column parts connecting the pair of annular parts so that pockets for housing the rollers are formed. Here, the entire surface of the outer diameter surface of the annular part and the column part is ground into the shape of a circular arc.
According to the above constitution, the surface other than the circular arc shape such as a flat surface is not contained in the outer diameter surface of the annular part and the column part, in the welded retainer provided in the roller bearing contained in the crankshaft supporting structure. Therefore, when used as the outer diameter guide, the entire of the annular part and the column part of the welded retainer is in contact with the outer diameter surface of the engagement hole provided at the large end part of the con-rod, so that the contact area can be increased. As a result, the surface pressure from the welded retainer to the engagement hole can be reduced and the aggressiveness of the welded retainer to the engagement hole is alleviated, so that the abrasion of the engagement hole can be reduced. In addition, since the welded retainer is light in weight, the aggressiveness to the engagement hole due to centrifugal force generated by the rotary motion can be alleviated.
In addition, a crankshaft supporting structure according to the present invention comprises a con-rod converting linear reciprocating motion to rotary motion, a crankshaft outputting the rotary motion, and a roller bearing supporting the crankshaft, fitted in an engagement hole provided at the large end of the con-rod, and used as an outer diameter surface guide. The roller bearing comprises a plurality of rollers, and a welded retainer manufactured such that a plate material is cut to a predetermined length, and bent into a cylindrical shape, and its ends are welded. In addition, the welded retainer comprises a pair of annular parts, and column parts connecting the pair of annular parts so that pockets for housing the rollers are formed. Here, the roundness of the outer diameter surface of the welded retainer is not more than 80μm.
When the welded retainer provided in the roller bearing in the crankshaft supporting structure has the roundness of 80μm or less as the outer diameter guide,
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the aggressiveness of the welded retainer to the engagement hole can be alleviated and the abrasion of the engagement hole can be reduced.
Preferably, the roundness of the outer diameter of the welded retainer is not less than 20μm. Although the roundness is improved by grinding the outer diameter surface, when it is defined as described above, the roundness is not unnecessarily improved, so that manufacturing cost can be lowered.
More preferably, a corner slope portion is provided at the corner of the column part on the side of the outer diameter surface. Thus, during the rotation of the welded retainer, the oil film is prevented being cut at the corner of the column part on the side of the outer diameter surface, so that lubricity can be improved and the aggressiveness toward the engagement hole can be alleviated.
Further preferably, a plating process is performed for the welded retainer. Thus, the surface of the welded retainer is protected and the lubricity can be improved and the aggressiveness toward the engagement hole can be alleviated.
Further preferably, carburized quenching and tempering processes are performed for the welded retainer. Thus, the hardness of the welded retainer can be enhanced.
According to another aspect of the present invention, a 2-cycle engine has any crankshaft supporting structure described above. According to still another aspect of the present invention, a 4-cycle engine has any crankshaft supporting structure described above. Thus, the 2-cycle engine and 4-cycle engine can alleviate the aggressiveness toward the inner diameter surface of the engagement hole provided at the large end part of the con-rod and reduce the abrasion of the engagement hole.
According to the present invention, the aggressiveness of the welded retainer toward the engagement hole can be alleviated and the abrasion of the engagement hole can be reduced.
As a result, the crankshaft supporting structure, the 2-cycle engine and the 4-cycle engine can elongate their life span.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a sectional view showing a part of a welded retainer 11 containing an end 16 of a column part 14, which is cut in the diameter direction;
Fig. 2 is a sectional view showing an essential part of a 2-cycle engine according to one embodiment of the present invention;
Fig. 3 is a sectional view showing a part of the welded retainer 11 containing the column part 14, which is cut in the axial direction;
Fig. 4 is a flowchart showing manufacturing steps of the welded retainer 11;
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Fig. 5 is a schematic view showing representative steps in the steps shown in Fig. 4; Fig. 6 is a configuration curve of an outer diameter surface 105 of a column part 103 in a welded retainer 101 manufactured by a conventional grinding step shown in Fig. 14;
Fig. 7 is a configuration curve of an outer diameter surface of the column part 14 in the welded retainer 11 shown in Fig. 1;
Fig. 8A is a sectional view showing a part of a welded retainer according to another embodiment in which a column part is linear.
Fig. 8B is a sectional view showing a part of a welded retainer according to another embodiment in which a column part is V-shaped and an end is bent in the direction perpendicular to the shaft;
Fig. 8C is a sectional view showing a part of a welded retainer according to another embodiment in which a column part is V-shaped and an end is bent in the direction along the shaft;
Fig. 9 is a schematic view showing a savant testing machine 41 for performing comparative evaluation of an abrasion amount;
Fig. 10 is a graph showing a relation between the roundness of the outer diameter surface of the welded retainer and the abrasion amount of the housing;
Fig. 11 is a longitudinal sectional view showing a 2-cycle engine using needle roller bearings at the large end part and small end part of a con-rod;
Fig. 12 is a sectional view showing a part of the conventional welded retainer 101 containing annular parts 102a and 102b, which is cut in the direction along the shaft;
Fig. 13 is a view showing a part of the conventional welded retainer 101 taken from the direction of an arrow X in Fig. 12; and
Fig. 14 is a sectional view showing the conventional welded retainer 101 containing an end 106 in Y-Y section in Fig. 12, which is cut in the diameter direction.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be described with reference to the drawings hereinafter. Fig. 2 is a sectional view showing an essential part of a 2-cycle engine according to one embodiment of the present invention. Referring to Fig. 2, a 2-cycle engine 51 comprises a piston (not shown) moving in a straight line back and forth by combustion of mixed gas, a crankshaft 52 outputting rotary motion, and a con-rod 53 connecting the piston and the crankshaft 52 to convert the linear back-and-forth movement to the rotary motion. The piston is connected to the small end
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part of the con-rod 53 by a piston pin 54 through a roller bearing 55. In addition, the crankshaft 52 is connected to the large end part of the con-rod 53 through a roller bearing 56.
The roller bearing 55 to support the piston pin 54 is fitted in an engagement hole provided at the small end part of the con-rod 53, whereby a piston pin supporting structure is formed. Similarly, the roller bearing 56 to support the crankshaft 52 is fitted in an engagement hole provided at the large end part of the con-rod 53, whereby a crankshaft supporting structure is formed. The roller bearing 56 comprises a plurality of rollers and a welded retainer for retaining the rollers. The welded retainer is used as an outer diameter guide in which the inner diameter surface of the engagement hole provided in the large diameter part of the con-rod 53 and the outer diameter surface of the welded retainer are in contact with each other. In addition, the roller bearing 55 fitted in the engagement hole provided in the small diameter part of the con-rod 53 has the same constitution.
Fig. 3 is a sectional view showing a part of the welded retainer 11 provided in the roller bearing 56 contained in the crankshaft supporting structure according to one embodiment of the present invention. Referring to Fig. 3, the welded retainer 11 comprises a pair of annular parts 13a and 13b, a plurality of column parts 14 connecting the pair of annular parts so that pockets to hold the roller 12 are provided between them.
The column part 14 has a V-shaped configuration in section in which its center part 15 is bent toward the inner side of the diameter direction. The side of an inner diameter surface 18 of the center part 15 of the column part 14 is narrow in width in the circumferential direction, whereby a preventing part for preventing the roller from escaping toward the inner diameter side is formed. In addition, an end 16 of the column part comprises a click as a preventing part for preventing the roller from escaping toward the outer diameter side, on the side of an outer diameter surface 17.
A manufacturing method of the welded retainer 11 will be described hereinafter. Fig 4 is a flowchart showing manufacturing steps for manufacturing the welded retainer 11. In addition, Fig. 5 is a schematic view showing representative steps in the steps shown in Fig. 4. The manufacturing method of the welded retainer 11 will be described with reference to Figs. 3,4 and 5.
First, a V-shaped form pressing step for pressing a steel plate of the material of the welded retainer 11 in its band steel state (Fig. 5(a)) is performed so that its sectional configuration may become V shape (Fig. 4A, Fig. 5(b)). Here, the V shape means that when the welded retainer 11 is bent into a cylindrical shape, the center of the band steel and the end of the band steel are different in level in the diameter direction. The V-shaped form pressing step is performed by sandwiching the steel plate between a molding roller press comprising an upper mold whose center is projected and a lower mold whose center is recessed and pressing it.
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Then, a pocket punching-out step for forming pockets to hold the rollers is performed for the bent band steel after the V-shaped form pressing step (Fig. 4(B), Fig. 5(c)). The pocket punching-out step is performed by pressing a blade edge to the band steel along a pocket configuration with a punch having a punching blade and punching it out.
Then, a click forming step for forming the click for preventing the roller from escaping toward the outer diameter side (Fig. 4(C)) is performed. The click forming step is performed by fixing the end 16 of the column part 14 on the side of the outer diameter surface 17 and pressing the end by a press from the side of the inner diameter surface 18, so that the width dimension of the end 16 on the side of the outer diameter surface 17 is enlarged in the circumferential direction.
Then, a cutting step for cutting the band steel to be the circumferential length of the welded retainer 11 as a predetermined length is performed (Fig. 4(D)), and a bending step for bending the cut steel plate into the cylindrical shape is performed (Fig. 4(E), Fig. 5(d)). Then, a welding step for connecting both end surfaces of the bent steel plate is performed (Fig. 4(F)).
Then, a first grinding step for grinding the outer diameter surface 17 of the cylindrical welded retainer 11 is performed (Fig. 4(G)). Here, in the cylindrically bent steel plate, a smooth cylindrical surface is formed along the outer diameter surface 17 at the annular parts 13a and 13b continuously provided in the circumferential direction, but the outer diameter surface 17 at the end 16 of the column part 14 that is not continuously provided in the circumferential direction is flat without forming the circular arc that constitutes the cylinder. The first grinding step is performed for rounding an outer corner positioned at the end of the column part 14 in the width direction.
Then, carburized quenching and tempering treatments are performed as a heat treatment step (Fig. 4(H)). By this heat treatment step, the hardness of the welded retainer is improved. Here, the heat treatment step is not limited to the carburized quenching and tempering treatments, and another heat treatment step such as a carbonitriding treatment or a liquid quenching treatment may be performed according to usage.
Then, a second grinding step for grinding the outer diameter surface 17 of the welded retainer 11 again is performed (Fig. 4(1)). By the second grinding step, the whole surface of the outer diameter surface 17 of the annular parts 13a and 13b and the column part 14 of the welded retainer 11 is ground to be a circular arc. In addition, by this step, the roundness of the outer diameter surface 17 becomes 80μm or less. More specifically, by this step, a flat part positioned in the center of the outer diameter surface 17 at the end 16 of the column part 14 is ground to be eliminated.
Then, a surface sloping process for the corner of the outer diameter surface at the end 16 of the column part 14 is performed (Fig. 4(J)). The surface sloping process is a
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process for grinding the corner larger than a normal chamfer. Thus, the oil film of lubricant oil is prevented from being cut during rotation. This step is performed by a tumbling process.
Then, after a cleaning step, the surface of the welded retainer 11 is plated (Fig. 4(K)). The plating process may be a copper plating process or copper and silver plating process. By this plating process, the surface of the welded retainer is protected and a lubricating property is improved, so that aggressiveness to the housing can be alleviated.
Thus, the welded retainer 11 is manufactured (Fig. 5(e)). In addition, when the plurality of rollers are incorporated in the pockets of the above welded retainer 11, the roller bearing is completed. In addition, when the roller bearing manufactured as described above is fitted in the engagement hole provided at the large diameter part of the con-rod, the crankshaft supporting structure is completed, and the 2-cycle engine is manufactured using such crank shaft supporting structure.
A description will be made of a case where the roller bearing comprising the welded retainer 11 manufactured by the above method is incorporated in the inner diameter surface of the engagement hole provided at the large end part of the con-rod hereinafter. Fig. 1 is a sectional view showing a part of the section of the end 16 of the column part 14 containing a preventing part 19 for preventing the roller from escaping toward its outer diameter side, which is cut in the diameter direction. Referring to Fig. 1, a corner 20 of the end 16 of the column part 14 has been rounded by the first grinding step and a corner slope portion has been provided. A center part 21 on the outer diameter surface 17 at the end 16 of the column part 14 is not flat but has been ground into the circular arc by the second grinding step. In addition, the roundness of the outer diameter surface 17 is not more than 80μm through the first and second grinding steps.
Here, Fig. 6 shows the outer diameter outline of the outer diameter surface 105 when the end 104 of the column part 103 of the conventional welded retainer 101 shown in Fig. 14 is cut in the diameter direction, and Fig. 7 shows the outer diameter outline of the outer diameter surface 17 when the end 16 of the column part 14 of the welded retainer 11 shown in Fig. 1 is cut in the diameter direction. In Fig. 6 and 7, the vertical side of one square is 0.2mm and the lateral side of one square is 0.2mm. In addition, in Figs. 6 and 7, when the welded retainer is bent into the cylindrical shape, the ideal curve of the outer diameter surface in an ideal circular arc is shown by a curve 22.
Referring to Figs. 6 and 7, according to an outer diameter outline 23 of the conventional welded retainer 101, there is almost no difference between a center part 24 and an end 25 in the diameter direction and it is flat. In addition, a dimensional difference between the end 25 and the ideal configuration curve 22 in the diameter direction is big.
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Meanwhile, according to the outer diameter outline 26 of the welded retainer 11 shown in Fig. 1, its dimension in the diameter direction is gradually increased from an end 28 to a center 27, so that it forms a circular arc. In addition, the outer diameter outline 26 overlaps with the ideal configuration curve 22 at not only the center 27 and the end 28 but also almost other parts, which form an ideal circular arc.
Referring to Fig. 1 again, when the welded retainer 11 having the outer diameter surface 17 that is not flat but forms the ideal circular arc is used as an outer diameter guide, an inner diameter surface 29 of an engagement hole (not shown) indicated by a dashed line in Fig. 1 and the whole surface of the outer diameter surface 17 of the welded retainer 11 are in contact with each other. Therefore, the contact area thereof can be large and the surface pressure from the welded retainer 11 to the inner surface of the engagement hole can be reduced. As a result, aggressiveness to the engagement hole can be alleviated and the abrasion of the engagement hole can be reduced. The crankshaft supporting structure and the 2-cycle engine comprising the con-rod containing the engagement hole in which the abrasion is reduced can implement a long life.
In addition, the above embodiment can be applied to a case where the 2-cycle engine is replaced with a 4-cycle engine.
As described above, the crankshaft supporting structure, the 2-cycle engine and the 4-cycle engine can elongate their life span.
In addition, although the sectional configuration of the welded retainer is V shape in the above embodiment, the present invention is not limited to this. For example, a welded retainer may have another sectional configuration. Each of Figs. 8A, 8B and 8C is a sectional view showing a part of a welded retainer according to another embodiment of the present invention. Referring to Fig. 8A, the center of a column part 32 may not be bent in a welded retainer 31 and the sectional configuration of the column part 32 may be linear. Referring to Fig. 8B, a welded retainer 33 may be an M-type retainer in which the center of a column part 34 is bent to the inner side of the diameter direction into a V shape and an end 35 is bent toward the inner side of the diameter direction so as to be perpendicular to the shaft. Furthermore, referring to Fig. 8C, a welded retainer 36 may be such that the center of a column part 37 is bent toward the inner side of the diameter direction into a V shape and an end 38 is bent toward the inner side of the diameter direction so as to be along the shaft.
Here, a test for comparatively evaluating an abrasion amount was performed for the welded retainer having the configuration shown in Fig. 8B. Fig. 9 is a schematic view showing a savant testing machine for comparatively evaluating the abrasion amount. Referring to Fig. 9, a savant testing machine 41 comprises a retainer mounting part 42 in which the welded retainer is mounted, and a loading part 43 for applying constant load. The loading part 43 applies predetermined load to the retainer mounting part 42 by a spring 44, and its loading amount is measured by a load cell 45. The retainer mounting part 42 is filled with lubricant oil and it is kept at
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a constant temperature by a cartridge heater 46. A housing is provided in the retainer mounting part 42 and when the retainer as a test piece is mounted on a retainer mounting hole 47, the inner diameter surface of the housing and the outer diameter surface of the retainer are in contact with each other. The mounted retainer is fixed by a retaining pin 48, and after the housing and the retainer slide for a predetermined time while they are in contact with each other, the abrasion amount of the housing is measured.
In addition, the test condition is as follows. The result of the test is shown n Fig. 10.
Test piece size : inner diameter Ø 26mm x outer diameter Ø 33mm x width 13.8mm Plating process : performed The number of tests : 4 times
Fig. 10 is a graph showing a relation between the roundness of the outer diameter surface of the welded retainer and the abrasion amount of the housing in which a lateral axis shows the roundness of the outer diameter surface of the retainer, and a vertical axis shows the abrasion amount of the housing. Referring to Fig. 10, when the roundness of the outer diameter surface is not less than l00μm, the housing is worn at least 3μm, and some is worn up to 4μm. Meanwhile, when the roundness of the outer diameter surface is not more than 80μm, the abrasion amount of the housing is reduced and it is up to about half of the above.
In addition, as long as it is not more than 80μm, even when it is 20μm, the abrasion amount of the housing is about the same. Here, in order to reduce the roundness of the outer diameter surface of the welded retainer to 20μm or less, it is necessary to increase the number of grinding steps and increase the ground amount. In this case, as the number of steps is increased and the ground amount is increased, the manufacturing cost is increased and the hardness of the welded retainer is reduced, so that it is preferable that the roundness is not less than 20μm.
In addition, although the grinding steps are performed two times in the above embodiment, the present invention is not limited to this. For example, at one grinding step, the corner of a column part on the outer diameter side may be rounded and the outer diameter surface of the annular part and the column part of a welded retainer may be ground so that the roundness of the outer diameter surface may become 80μm or less. Furthermore, the grinding steps may be performed three times or more to grind the outer diameter surface of the annular part and the column part of a welded retainer to be a circular arc so that the roundness of the outer diameter surface may be 80μm or less.
In addition, although the roller bearing incorporated in the crankshaft supporting structure comprises the plurality of rollers and the welded retainer in the above embodiment, the present invention is not limited to this. For example, the roller bearing may comprise a shell type outer ring. In this case, since the welded retainer is used as the outer diameter guide, the outer diameter surface of the welded retainer is in contact with the inner diameter surface of the shell type outer ring and
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the inner diameter surface of the shell type outer ring is attacked. However, when the welded retainer has the above constitution, since the aggressiveness to the inner diameter surface of the shell type outer ring can be alleviated, the shell type outer ring is not likely to be worn, that is, the crankshaft supporting structure and the like can elongate its life span.
In addition, although the preventing part for preventing the roller from escaping toward the inner diameter side is formed by performing the V-shaped form molding step and the preventing part for preventing the roller from escaping toward the outer diameter side is formed by forming the click in the above embodiment, the present invention is not limited to this. The preventing part for preventing the roller from escaping toward the inner and outer diameter sides may be formed by another method.
Although the embodiments of the present invention have been described with reference to the drawings in the above, the present invention is not limited to the above-illustrated embodiments. Various kinds of modifications and variations may be added to the illustrated embodiments within the same or equal scope of the present invention.
Since the crankshaft supporting structure, the 2-cycle engine, and the 4-cycle engine according to the present invention can reduce the abrasion of the inner diameter surface of the engagement hole provided at the large end part of the con-rod, they can be effectively used as the crankshaft supporting structure having a long life and the 2-cycle engine and 4-cycle engine having the above crankshaft supporting structure.
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WE CLAIM :
1. A crankshaft supporting structure of an engine, comprising:
a con-rod converting linear reciprocating motion to rotary motion;
a crankshaft outputting the rotary motion; and
a roller bearing supporting said crankshaft, fitted in an engagement hole
provided at the large end part of said con-rod, and used as an outer diameter
surface guide, wherein
said roller bearing comprises a plurality of rollers, and a welded retainer
manufactured such that a plate material is cut to a predetermined length, and
bent into a cylindrical shape, and its ends are welded,
said welded retainer comprises a pair of annular parts, and column parts
connecting the pair of annular parts so that pockets for housing said rollers
are formed, and
the entire surface of the outer diameter surface of said annular part and said
column part is ground into the shape of a circular arc.
2. A crankshaft supporting structure of an engine, comprising:
a con-rod converting linear reciprocating motion to rotary motion;
a crankshaft outputting the rotary motion; and
a roller bearing supporting said crankshaft, fitted in an engagement hole
provided at the large end part of said con-rod, and used as an outer diameter
surface guide, wherein
said roller bearing comprises a plurality of rollers, and a welded retainer
manufactured such that a plate material is cut to a predetermined length, and
bent into a cylindrical shape, and its ends are welded,
said welded retainer comprises a pair of annular parts, and column parts
connecting the pair of annular parts so that pockets for housing said rollers
are formed, and
the roundness of the outer diameter surface of said welded retainer is not
more than 80μm.
3. The crankshaft supporting structure according to claim 2, wherein the roundness of the outer diameter of said welded retainer is not less than 20μm.
4. The crankshaft supporting structure according to claim 1, wherein a corner slope portion is provided at the corner of said column part on the side of the outer diameter surface.
5. The crankshaft supporting structure according to claim 1, wherein a plating process is performed for said welded retainer.
6. The crankshaft supporting structure according to claim 1, wherein carburized quenching and tempering processes are performed for said welded retainer.
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7. A 2-cycle engine having the crankshaft supporting structure according to claim 1.
8. A 4-cycle engine having the crankshaft supporting structure according to claim 1.
Dated this 23rd day of August, 2006

HIR AL CHANDRAKANT JOSHI
AGENT FOR
BAYER HEALTHCARE LLC
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ABSTRACT
A crankshaft supporting structure comprises a con-rod converting linear reciprocating motion to rotary motion, a crankshaft outputting the rotary motion, and a roller bearing supporting the crankshaft, fitted in an engagement hole provided at the large end part of the con-rod, and used as an outer diameter surface guide. The roller bearing comprises a plurality of rollers, and a welded retainer manufactured such that a plate material is cut to a predetermined length, and bent into a cylindrical shape, and its ends are welded. The entire surface of the outer diameter surface 17 of the annular part and the column part 14 of the welded retainer 11 is ground into the shape of a circular arc. When the outer diameter surface 17 of the welded retainer 11 and the inner diameter surface 29 of the engagement hole come in contact with each other, aggressiveness to the engagement hole is alleviated and the abrasion of the engagement hole is reduced.
To,
The Controller of Patents
The Patent Office
Mumbai.
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Documents:

1329-MUM-2006-ABSTRACT(2-3-2009).pdf

1329-MUM-2006-ABSTRACT(24-8-2006).pdf

1329-mum-2006-abstract(granted)-(26-6-2009).pdf

1329-mum-2006-abstract-1.jpg

1329-mum-2006-abstract.doc

1329-mum-2006-abstract.pdf

1329-MUM-2006-CLAIMS(2-3-2009).pdf

1329-MUM-2006-CLAIMS(24-8-2006).pdf

1329-mum-2006-claims(granted)-(26-6-2009).pdf

1329-mum-2006-claims.doc

1329-mum-2006-claims.pdf

1329-mum-2006-correspondance-received.pdf

1329-MUM-2006-CORRESPONDENCE(2-3-2009).pdf

1329-MUM-2006-CORRESPONDENCE(4-12-2006).pdf

1329-MUM-2006-CORRESPONDENCE(IPO)-(15-7-2009).pdf

1329-mum-2006-description (complete).pdf

1329-MUM-2006-DESCRIPTION(COMPLETE)-(2-3-2009).pdf

1329-MUM-2006-DESCRIPTION(COMPLETE)-(24-8-2006).pdf

1329-mum-2006-description(granted)-(26-6-2009).pdf

1329-MUM-2006-DRAWING(2-3-2009).pdf

1329-MUM-2006-DRAWING(24-8-2006).pdf

1329-mum-2006-drawing(granted)-(26-6-2009).pdf

1329-mum-2006-drawings.pdf

1329-MUM-2006-FORM 1(16-11-2006).pdf

1329-MUM-2006-FORM 1(24-8-2006).pdf

1329-MUM-2006-FORM 18(24-8-2006).pdf

1329-mum-2006-form 2(2-3-2009).pdf

1329-MUM-2006-FORM 2(COMPLETE)-(24-8-2006).pdf

1329-mum-2006-form 2(granted)-(26-6-2009).pdf

1329-MUM-2006-FORM 2(TITLE PAGE)-(2-3-2009).pdf

1329-MUM-2006-FORM 2(TITLE PAGE)-(24-8-2006).pdf

1329-mum-2006-form 2(title page)-(granted)-(26-6-2009).pdf

1329-MUM-2006-FORM 3(2-3-2009).pdf

1329-MUM-2006-FORM 3(24-8-2006).pdf

1329-MUM-2006-FORM 5(2-3-2009).pdf

1329-MUM-2006-FORM 5(24-8-2006).pdf

1329-mum-2006-form-1.pdf

1329-mum-2006-form-2.doc

1329-mum-2006-form-2.pdf

1329-mum-2006-form-3.pdf

1329-mum-2006-form-5.pdf

1329-MUM-2006-GENERAL POWER OF ATTORNEY(4-12-2006).pdf

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Patent Number

235148

Indian Patent Application Number

1329/MUM/2006

PG Journal Number

28/2009

Publication Date

10-Jul-2009

Grant Date

26-Jun-2009

Date of Filing

24-Aug-2006

Name of Patentee

NTN CORPORATION

Applicant Address

3-17 KYOMACHIBORI 1-CHOME, NISHI-KU,OSAKA-SHI, OSAKA 550-0003,

Inventors:

#	Inventor's Name	Inventor's Address
1	TAKASHI YASUNISHI	c/o NTN CORPORATION 1578.HIGASHIKAIZUKA,IWATA.SHI SHIZUOKA 438-8510 JAPAN
2	MAKOTO NISHIKAWA	c/o NTN CORPORATION 1578.HIGASHIKAIZUKA,IWATA.SHI SHIZUOKA 438-8510 JAPAN

PCT International Classification Number

F16C33/46

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2005-249717	2005-08-30	Japan