By a News Reporter-Staff News Editor at China Weekly News -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventor Nishidate, Masahiro (Gunma-ken, JP), filed on November 6, 2017, was made available online on June 21, 2018.



No assignee for this patent application has been made.



News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to a bearing device having an oil-impregnated bearing made from a porous sintered metal material and a brushless motor provided with this bearing device.



"For example, Japanese Patent Laid-Open Publication No. 2007-252193 describes a bearing structure comprising: an oil-impregnated bearing; a rotary shaft that is supported by an oil-impregnated bearing and has a recess (annular groove) in the outer circumference; and a seal member covering the top face and the outer circumferential face of the oil-impregnated bearing. With this bearing structure, it is said that oil leakage can be prevented by the seal member, whereby the useful life of the oil-impregnated bearing can be extended.



"Furthermore, Japanese Patent Laid-Open Publication No. 2016-164436 describes a bearing structure comprising: a rotary shaft that has an annular groove on the outer circumferential face; an oil-impregnated bearing that supports the rotary shaft; a bearing holder that holds the outer circumferential face of the oil-impregnated bearing; and a seal member that is fixed at the upper end of the bearing holder. This seal member is made of a porous sintered metal material having a density lower than the density of the sintered metal material for the oil-impregnated bearing, and has a large-diameter inner circumferential face, which faces the annular groove of the rotary shaft, and a small-diameter inner circumferential face, which forms a seal gap with respect to the outer circumferential face of the rotary shaft, the seal member being disposed in contact with the top face of the oil-impregnated bearing. In this bearing structure, when the rotary shaft rotates, the oil exuded from the oil-impregnated bearing is transmitted upward on the rotary shaft, and when it reaches the annular groove, it is sprayed outward in the radial direction by the centrifugal force of the rotary shaft. Furthermore, the sprayed oil is received on the large-diameter inner circumferential face of the seal member and is absorbed by the seal member. Thereupon, due to a capillary phenomenon caused by the difference in density between the seal member and the oil-impregnated bearing, the oil that has been absorbed into the seal member moves to the oil-impregnated bearing, whereby it is said that the oil in the oil-impregnated bearing can be recirculated.



"However, with the bearing structure of Japanese Patent Laid-Open Publication No. 2007-252193, the recess in the rotary shaft is disposed outside the seal member, and therefore, when the motor is used in the horizontal state (a state in which the rotary shaft is horizontal), the oil from the oil-impregnated bearing which has been transmitted to the recess in the rotary shaft will disadvantageously leak to the outside of the bearing structure, which is a problem in so much as the useful life of the oil-impregnated bearing is reduced.



"On the other hand, with the bearing structure in Japanese Patent Laid-Open Publication No. 2016-164436, the annular groove in the rotary shaft is disposed inside the seal member, and therefore oil from the oil-impregnated bearing does not disadvantageously leak directly from the annular groove to the outside of the bearing structure.



"However, with the bearing structure in Japanese Patent Laid-Open Publication No. 2016-164436, oil that has sprayed radially outward from the annular groove in the rotary shaft strikes the large-diameter inner circumferential face of the seal member, and some of the oil that rebounds from the large-diameter inner circumferential face will readily be redeposited on the portion above the annular groove in the rotary shaft. Therefore, when the motor is used in the horizontal state, the oil from the oil-impregnated bearing that has been redeposited on the portion above the annular groove is likely to leak to the outside of the bearing structure, which is a problem in so much as the useful life of the oil-impregnated bearing is reduced.





"Furthermore, with the bearing structure in Japanese Patent Laid-Open Publication No. 2016-164436, the seal member is press-fitted on the bearing holder so as to contact the oil-impregnated bearing, and therefore, if the press-fitting force is too strong, the pores of the seal member tend to be crushed, such that the capillary phenomenon at the contact faces between the seal member and the oil-impregnated bearing cannot readily be utilized. Furthermore, if this press-fitting force is too small, the seal member and the oil-impregnated bearing will not come into sufficient contact, such that the capillary phenomenon cannot be obtained. For this reason, it is difficult to manage the press-fitting and there is a problem in that the quality tends to be unstable."



As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventor's summary information for this patent application: "In one or more embodiments of the present invention, a bearing device and a brushless motor comprising this bearing device are provided, in which press-fitting of the seal member can be managed easily and leakage of oil from the oil-impregnated bearing to the outside of the bearing structure can be effectively prevented in both the upright state and the horizontal state, allowing the life of the bearing device to be extended.



"Note that, in the aspects described below, the constituent elements employed can be used in the most freely chosen combinations possible. Furthermore, the aspects and technical features of the present invention are not limited to those described hereafter, and are to be understood based on the description in the entire specification and the drawings or the inventive ideas that can be grasped by the skilled artisan on the basis of these descriptions.



"A first aspect of the present invention relating to a bearing device comprises:



"a vertically elongated rotary shaft;



"an annular oil-impregnated bearing that rotatably supports the rotary shaft;



"a bearing holder having an opening at the upper end that holds the oil-impregnated bearing at the inside; and



"a washer member disposed on the top face of the oil-impregnated bearing;



"an annular seal member through which the rotary shaft is inserted, which is fixed at the upper end of the bearing holder so as to close the opening,



"wherein



"the outer surface of the seal member and the outer circumferential face of the rotary shaft that faces to the seal member in the radial direction are subjected to oil-repellent treatment;



"the washer member and the seal member are disposed in a mutually non-contacting state in the axial direction;



"the rotary shaft has an annular groove in the outer circumferential face, and an upper portion of the rotary shaft protrudes upward beyond the seal member;



"a minimum diameter part of the annular groove is disposed between the uppermost surface of the washer member and the lowermost surface of the seal member; and



"the upper end of the annular groove is disposed below the uppermost surface of the seal member in the axial direction.



"A second aspect of the present invention relating to a brushless motor is such that



"in a brushless motor having a bearing device in which a vertically elongated rotary shaft is rotatably supported by an annular oil-impregnated bearing,



"the bearing device comprises: a bearing holder having an opening at the upper end that holds the oil-impregnated bearing at the inside; a washer member disposed on the top face of the oil-impregnated bearing; and an annular seal member through which the rotary shaft is inserted, which is fixed at the upper end of the bearing holder so as to close the opening,



"wherein



"the outer surface of the seal member and the outer circumferential face of the rotary shaft that faces to the seal member in the radial direction are subjected to oil-repellent treatment;



"the washer member and the seal member are disposed in a mutually non-contacting state in the axial direction;



"the rotary shaft has an annular groove in the outer circumferential face, and an upper portion of the rotary shaft protrudes upward beyond the seal member;



"a minimum diameter part of the annular groove is disposed between the uppermost surface of the washer member and the lowermost surface of the seal member; and



"the upper end of the annular groove is disposed below the uppermost surface of the seal member in the axial direction"