JP2009085355A - Oil retaining bearing mechanism and brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil retaining bearing in which a lubricant agent retaining amount of the oil retaining bearing is increased and besides high performance, long life and high reliability are ensured by preventing the lubricant agent from evaporating and leaking from the oil retaining bearing. <P>SOLUTION: An oil retaining bearing mechanism comprises a shaft and the oil retaining bearing. The oil retaining bearing 60 is equipped with an inside bearing 62 which is substantially hollow and substantially tubular and is made of a sintered material containing a lubricating agent and an outside bearing 64 which is substantially hollow and tubular and whose inner circumferential surface surrounds axially and externally an outer circumferential surface of the inside bearing 62 and further is made of the sintered material containing a lubricating agent. Between the outer circumferential surface of the inside bearing 62 and the inner circumferential surface of the outside bearing 64, a communicating groove 68 is formed which communicates with the outside and makes an axial upper space and an axial lower space communicate with each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oil-impregnated bearing mechanism that is inexpensive, high-performance, and long-life and has high reliability, and a brushless motor using the oil-impregnated bearing mechanism.

  As a bearing used for a motor for OA equipment, a motor for an optical disk drive, a fan motor for cooling an electronic equipment, etc., a bearing made of a porous material having a substantially hollow cylindrical shape and containing a lubricant therein (hereinafter referred to as an oil-impregnated bearing). Called). Oil-impregnated bearings have the advantage that the manufacturing cost can be kept low compared with rolling bearings such as ball bearings of the same volume.

  Conventionally, the following structures have been proposed as oil-impregnated bearings.

  FIG. 6 shows a conventional sintered oil-impregnated bearing disclosed in Patent Document 1. Referring to FIG. 6, the sintered oil-impregnated bearing includes a bearing portion 1a having a bearing hole 3a and an outer ring 2a fitted on the outer diameter surface of the bearing portion 1a. The outer ring 2a is set to have a higher porosity than the bearing portion 1a, and is used as an oil replenishing mechanism.

  In addition, in the configuration disclosed in Patent Document 2, in the oil-impregnated bearing including the inner portion and the outer portion having different opening ratios, a configuration in which a groove is provided on either the inner portion or the outer portion is disclosed.

Japanese Patent No. 3582869 JP 2006-292161 A

  In recent years, from the viewpoint of production cost, replacement of oil bearings with equipment bearings that have conventionally used ball bearings has been progressing. Along with this, fields where oil-impregnated bearings are applied have also expanded. Conventionally applied to equipment that has relatively low load and does not rise in temperature, such as an optical disk drive motor, but has recently been used in high-temperature environments such as projector cooling fan motors. Is increasing.

  By the way, the life of the oil-impregnated bearing and the amount of lubricant are closely related. That is, when the lubricant is insufficient, the lubrication is not performed normally and seizure may occur. Therefore, in order to realize a long life of the oil-impregnated bearing, it is necessary to increase the amount of lubricant retained in the oil-impregnated bearing. On the other hand, downsizing is required for equipment to which the oil-impregnated bearing described above is applied. Therefore, it is difficult to adopt a structure that increases the amount of lubricant retained by increasing the volume of the oil-impregnated bearing.

  Further, in order to realize a long life of the oil-impregnated bearing, it is necessary to prevent the lubricant retained in the oil-impregnated bearing from decreasing. Leakage and evaporation are the main factors that reduce the remaining amount of lubricant. The leakage of the lubricant is caused by the lubricant moving out of the oil-impregnated bearing due to heat, bubbles, centrifugal force, etc. generated during rotation. The evaporation of the lubricant occurs when the lubricant evaporates from a portion where the lubricant is exposed to the outside air, such as an end face of the oil-impregnated bearing.

  As described above, in order to realize a long life of the bearing, it is necessary to increase the amount of lubricant retained in the oil-impregnated bearing and to prevent the leakage and evaporation of the lubricant from the oil-impregnated bearing.

  The present invention solves such problems, increases the amount of lubricant retained in the oil-impregnated bearing, and prevents leakage and evaporation of the lubricant from the oil-impregnated bearing, resulting in high performance and long life. In addition, an oil-impregnated bearing mechanism having high reliability is provided.

  An oil-impregnated bearing mechanism according to the present invention includes a shaft, an inner bearing made of a porous material having a substantially hollow cylindrical shape and having an inner peripheral surface serving as a bearing surface for rotatably supporting the shaft, and containing a lubricant. An outer bearing made of a porous material having a hollow cylindrical shape and an inner peripheral surface radially surrounding an outer peripheral surface of the inner bearing and containing a lubricant, and an outer periphery of the inner bearing Between the surface and the inner peripheral surface of the outer bearing, there is at least one communication groove communicating with the outside and formed by a part of the outer peripheral surface of the inner bearing and a part of the inner peripheral surface of the outer bearing. The communication groove is formed to communicate a space on one end side in the axial direction of the inner bearing with a space on the other end side in the axial direction.

  According to the oil-impregnated bearing mechanism according to the present invention, the communication groove is formed between the outer peripheral surface of the inner bearing and the inner peripheral surface of the outer bearing, and the lubricant exuded from the inner bearing and the outer bearing can be retained. .

  In addition to the above configuration, the oil-impregnated bearing mechanism according to the present invention is characterized in that the radial thickness of the inner bearing is substantially uniform in the circumferential direction.

  According to the oil-impregnated bearing mechanism according to the present invention, when an external force is applied when the oil-impregnated bearing is processed and assembled, a force is uniformly applied to the entire inner bearing. Therefore, the inner bearing is less likely to be distorted during processing and assembly. As a result, a highly accurate oil-impregnated bearing mechanism can be provided.

  In addition to the above configuration, the oil-impregnated bearing mechanism according to the present invention is characterized in that the outer bearing has a higher porosity than the inner bearing.

  According to the oil-impregnated bearing mechanism according to the present invention, since the outer bearing has a higher porosity than the inner bearing, the amount of lubricant retained can be increased compared to the case where the bearing is configured by the inner bearing alone. it can. Therefore, wear and seizure due to insufficient lubricant are less likely to occur, and the bearing life can be extended.

  The oil-impregnated bearing mechanism according to the present invention is characterized in that, in addition to the above configuration, the inner bearing is made of a material that is more excellent in wear resistance than the outer bearing.

  According to the oil-impregnated bearing mechanism according to the present invention, the inner bearing constituting the bearing surface is made of a material having excellent wear resistance. Therefore, it is difficult for the oil-impregnated bearing to be worn, and the life of the oil-impregnated bearing mechanism can be increased.

  The oil-impregnated bearing mechanism according to the present invention is characterized in that, in addition to the above configuration, the porous material of the inner bearing is a sintered material.

  In the oil-impregnated bearing mechanism according to the present invention, in addition to the above-described configuration, the outer bearing has a porosity in a surface layer on one end surface in the axial direction and a porosity in a surface layer on the other end surface in the axial direction. It is characterized by being less than the porosity located in the surface layer of the peripheral surface.

  According to the oil-impregnated bearing mechanism according to the present invention, the end face of the outer bearing of the oil-impregnated bearing is crushed. Therefore, it is difficult for the lubricant inside the outer bearing to flow out from the outer bearing end face.

  In the oil-impregnated bearing mechanism according to the present invention, in addition to the above configuration, the communication groove has a recess formed by a part of the inner peripheral surface of the outer bearing being recessed radially outward. It is formed by facing through a gap.

  According to the oil-impregnated bearing mechanism according to the present invention, the recess is formed at a position relatively far from the shaft. Therefore, the influence of the pressure difference generated by the presence or absence of the communication groove can be relatively suppressed. Further, the communication groove can be configured to have a relatively wide width.

  In addition to the above configuration, the oil-impregnated bearing mechanism according to the present invention is characterized in that a plurality of the communication grooves are provided at equal intervals in the circumferential direction.

  According to the oil-impregnated bearing mechanism according to the present invention, when the inner bearing is press-fitted into the outer bearing, a force is evenly applied to the inner bearing. Therefore, when producing the oil-impregnated bearing, the inner bearing is not distorted, and a highly accurate oil-impregnated bearing mechanism can be provided.

  In the oil-impregnated bearing mechanism according to the present invention, in addition to the above configuration, the concave portion of the outer bearing has a curved shape that is recessed radially outward, and the radial direction from the outer peripheral surface of the inner bearing to the outermost radial position of the concave portion. The length of is about 0.4 mm or more.

  According to the oil-impregnated bearing mechanism according to the present invention, the volume of the communication groove is ensured, and the lubricant is hardly pushed out of the communication groove by bubbles.

  In the oil-impregnated bearing mechanism according to the present invention, in addition to the above configuration, a first inclined surface is formed on the radially inner side of the end surface on the one end side in the axial direction of the outer bearing, and the diameter of the end surface on the other end side in the axial direction of the outer bearing. A second inclined surface is formed on the inner side in the direction, and the first inclined surface is formed between an end surface on one end side in the axial direction of the outer bearing and the outer peripheral surface of the inner bearing, and the second inclined surface is It is formed between the end surface on the other end side in the axial direction of the outer bearing and the outer peripheral surface of the inner bearing, and the communication groove is provided radially inward from the other end surface on the one end side in the axial direction of the outer bearing and the end surface on the other end side. It is characterized by being able to.

  According to the oil-impregnated bearing mechanism according to the present invention, it is difficult for the lubricant retained in the communication groove to flow directly to the end face. Therefore, an oil-impregnated bearing mechanism having a long life can be provided. Further, since the inclined surface and the communication groove can be formed at a time, processing becomes easy.

  In the oil-impregnated bearing mechanism according to the present invention, in addition to the above configuration, a washer is fitted to the shaft, and the end surface on the one end side in the axial direction of the outer bearing is on one end side in the axial direction relative to the end surface on the one end side in the axial direction of the inner bearing. The washer has an outer diameter larger than an inner diameter of the inner bearing and smaller than an inner diameter of the outer bearing, and at least a part of the washer is axially more axial than the end surface on the one end side in the axial direction of the outer bearing. Located on the other end side and on one end side in the axial direction from the end surface on the one end side in the axial direction of the inner bearing, at least a part of the outer peripheral surface of the washer is radially with the inner peripheral surface of the outer bearing or the first inclined surface It is characterized by facing.

  According to the oil-impregnated bearing mechanism according to the present invention, the lubricant transmitted through the shaft by the centrifugal force that acts when the shaft rotates is spun off radially outward from the washer, and a flow of lubricant that is absorbed by the outer bearing is formed. Therefore, the lubricant of the oil-impregnated bearing is prevented from leaking out of the bearing portion, and the life of the oil-impregnated bearing mechanism can be extended.

  A brushless motor according to the present invention is connected to an oil-impregnated bearing mechanism, a rotor connected to the shaft and including a permanent magnet, a housing that fits and holds an outer peripheral surface of the outer bearing in a holding portion, and the housing. And a stator that is opposed to the permanent magnet through a gap and generates a rotating magnetic field.

  According to the brushless motor according to the present invention, it is possible to provide a brushless motor that has a long life and is relatively inexpensive.

  In addition to the above-described configuration, the brushless motor according to the present invention includes a part of the outer peripheral surface of the outer bearing that is recessed inward in the radial direction, a space on one axial end side of the outer bearing, and a shaft of the outer bearing. A communication portion that forms a space communicating with the space on the other end side in the direction is formed.

  According to the brushless motor of the present invention, the outer bearing is communicated in the axial direction by the communicating portion. When a pressure difference is generated in the outer bearing during rotation of the shaft, the lubricant can flow through the communicating portion, and the pressure difference in the oil-impregnated bearing can be eliminated. Further, when the lubricant thermally expands due to heat generated when the shaft rotates, the lubricant is held in the communication portion, and leakage of the lubricant is prevented.

  In addition to the above-described configuration, the brushless motor according to the present invention is characterized in that a circumferential position of the recess and a circumferential position of the communication portion are different from each other.

  According to the brushless motor according to the present invention, pressure is generated inside the inner bearing by the rotation of the shaft. The generated pressure oozes the lubricant from the inner bearing and the outer bearing. At this time, the lubricant exuded by the pressure is held in the concave portion and the communication portion. Even if the lubricant oozes out due to the pressure, the lubricant is held in the recess and the communication portion, so that it is difficult for the lubricant to leak out of the oil-impregnated bearing.

  In the brushless motor according to the present invention, in addition to the above configuration, the holding portion is formed by burring, and the axial end of the holding portion of the housing extends from the holding portion to the axial end of the outer bearing. A protruding portion that protrudes inward in the radial direction is formed so as to cover a part thereof.

  According to the brushless motor according to the present invention, the outer bearing end face is covered by the protruding portion, so that the lubricant outflow from the outer bearing outer peripheral face and the end face can be suppressed.

  In addition to the above-described configuration, the brushless motor according to the present invention includes an extension portion that extends radially outward from the other axial end side of the holding portion, and the rotor has a substantially bottomed cylindrical shape. A rotor holder to which the permanent magnet is fixed on an outer peripheral surface thereof, the rotor holder opening toward the oil-impregnated bearing, and an opening-side end surface thereof facing the extension portion through a gap. And

  According to the brushless motor according to the present invention, the extending portion and the rotor holder cover the oil-impregnated bearing, and the outflow of the lubricant can be suppressed.

  In the brushless motor according to the present invention, in addition to the above configuration, the housing is formed by press working, and the holding portion of the housing is positioned on one end side in the axial direction from the end surface on the other end side in the axial direction of the outer bearing, A curved portion that curves radially outward from the holding portion is formed on the other axial end side of the holding portion of the housing.

  According to the brushless motor of the present invention, a portion where the outer peripheral surface or the second inclined surface of the outer bearing and the curved surface are opposed to each other in the radial direction has a tapered shape in which the gap becomes narrower toward one end side in the axial direction. . With this structure, the lubricant that has oozed out of the outer bearing is held by capillary action at the tapered portion.

  In the brushless motor according to the present invention, in addition to the above configuration, the housing has a substantially hollow cylindrical shape, holds the stator on an inner peripheral surface on the other end side in the axial direction from the holding portion, and the permanent magnet includes the stator The housing is connected to a cap member at the other axial end side of the stator, the oil-impregnated bearing is further fixed to the cap member, and the oil-impregnated bearing is fixed to the cap member. The shaft is inserted radially inward of the bearing.

  According to the present invention, the amount of lubricant retained in the oil-impregnated bearing is increased, and the leakage and evaporation of the lubricant from the oil-impregnated bearing are prevented, thereby achieving high performance and long life and high reliability. An oil-impregnated bearing mechanism can be provided.

  Embodiments of the present invention will be described with reference to the drawings. In addition, the Example shown below is only a specific example of this invention, and this invention is not limited to the following embodiment.

<Motor>
FIG. 1 is a cross-sectional view of a brushless motor using an oil-impregnated bearing mechanism according to the present invention cut in the axial direction along a plane including a rotation center axis.

  Referring to FIG. 1, a brushless motor 1 has a fixed portion 3 having a stator 50 that changes a magnetic field, and a rotor magnet (permanent magnet) 26 that generates a rotating magnetic field, and rotates around a rotation center shaft 21. The rotating part 2 to perform, and the oil-impregnated bearings 60 and 80 which support relative rotation of the fixed part 3 and the rotating part 2 are provided.

  In the present embodiment, the axial direction refers to a direction along the rotation center axis 21. The radial direction refers to a direction orthogonal to the rotation center axis 21. Further, in the description of the present embodiment, for the sake of convenience, one end side in the axial direction is described as the lower side in the axial direction and the other end side in the axial direction is described as the upper side in the axial direction. In addition, the up-down direction in a present Example does not necessarily correspond with the gravity direction. In FIG. 1, the lower side in the axial direction refers to the lower side in the figure. In FIG. 1, the upper side in the axial direction refers to the upper side in the figure.

  First, the rotating unit 2 will be described. The shaft 20 rotates around the rotation center axis 21. The shaft 20 is inserted into a hole provided in the bottom of the rotor holder 22 having a substantially bottomed cylindrical shape. The rotor holder 22 is fixed coaxially with the shaft 20 while being opened to one axial end (the lower side in the drawing). A rotor magnet 26 is attached to the outer peripheral surface of the cylindrical portion 23 of the rotor holder 22. The rotor magnet 26 is a permanent magnet such as a neodymium magnet, for example. A fastening auxiliary member 24 that reinforces fastening of the rotor holder 22 and the shaft 20 is provided on the inner peripheral surface of the cylindrical portion 23 of the rotor holder 22.

  The shaft 20 protrudes downward in the axial direction from the fixed portion 3 on the lower side in the axial direction. For example, an impeller, a gear, a pulley, and the like are attached to the protruding portion to form a power transmission unit 28, and the driving force of the brushless motor 1 is output.

  The shaft 20 is fitted with a first washer 76 and a second washer 78 positioned axially below the first washer 76. The first washer 76 and the second washer 78 are arranged so as to sandwich an inner bearing 62 of the oil-impregnated bearing 60 described later. When an axial force is applied to the shaft 20, the end face of the inner bearing 62 of the oil-impregnated bearing 60 supports the first washer 76 or the second washer 78 and restricts the axial movement of the shaft 20. A third washer 96 and a fourth washer 98 are disposed on the shaft 20 so as to sandwich the inner bearing 82 of the oil-impregnated bearing 80.

  Next, the fixing part 3 will be described. The housing 30 is formed in a substantially bottomed cylindrical shape, and is disposed substantially concentrically with the rotation center shaft 21. The housing 30 includes a hollow cylindrical portion 32 having a hollow cylindrical shape, an extending portion 34 extending radially inward from an axially lower end portion of the hollow cylindrical portion 32, and a radially inner end of the extending portion 34. A bending portion 36 that curves downward in the axial direction, a holding portion 38 that extends downward from the bending portion 36 in the axial direction, and a bent portion radially inward from the lower axial end of the holding portion 38. And a projecting portion 40 projecting. The hollow cylindrical portion 32, the extending portion 34, the bending portion 36, the holding portion 38, and the protruding portion 40 are all made of the same member. The housing 30 is formed by pressing from a metal plate such as a galvanized steel plate.

  A stator 50 that generates a rotating magnetic field is fixed to the inner peripheral side of the hollow cylindrical portion 32 of the housing 30. The stator 50 includes a substantially annular core back 511 and a plurality of teeth 512 protruding radially inward from the core back 511, and a stator core 51 formed by laminating a plurality of thin silicon steel plates, A coil is formed by winding a wire around each tooth 512. When electricity flows through the coil 53, a magnetic field is generated. The stator 50 and the rotor magnet 26 are opposed to each other in the radial direction through a minute gap.

  A substantially disc-shaped circuit board 52 having an insertion portion 56 through which the shaft 20 is inserted is provided on the upper side in the axial direction of the rotor holder 22 of the hollow cylindrical portion 32 of the housing 30. The circuit board 52 is provided with wiring patterns and lands, and an electronic component 54 is mounted thereon, and an electric circuit constituted by these controls the rotation of the brushless motor 1.

  A coil 53 is connected to the power feeding land of the circuit board 52. The circuit board 52 is provided with a connector 58 extending upward in the axial direction. The connector 58 is connected to an external power source (not shown) and supplies power to the brushless motor 1. Further, the inner diameter of the insertion portion 56 of the circuit board 52 is provided larger than the outer diameter of the shaft 20, and the shaft 20 is inserted through a gap.

  The extending portion 34 of the housing 30 is provided substantially perpendicular to the rotation center shaft 21. The extension part 34 of the housing 30 faces the opening side end part of the rotor holder 22 via a minute gap.

  A substantially cylindrical oil-impregnated bearing 60 provided concentrically with the rotation center shaft 21 is press-fitted and fixed to the holding portion 38 of the housing 30. The oil-impregnated bearing 60 is made of a porous material such as a sintered material, for example. The oil-impregnated bearing 60 will be described later.

  The holding part 38 of the housing 30 is formed by burring. The housing 30 is formed with a protruding portion 40 that is bent radially inward from the lower side in the axial direction of the holding portion 38 and protrudes in an annular shape. The protrusion 40 covers the end face of the oil-impregnated bearing 60 and holds the lubricant that has oozed out in the vicinity of the end face of the oil-impregnated bearing 60. Further, the protrusion 40 prevents the lubricant from flowing out downward in the axial direction from the protrusion 40.

  The holding portion 38 and the extending portion 34 of the housing 30 are provided via a bending portion 36 that curves outward in the radial direction from the holding portion 38 toward the upper side in the axial direction.

  A part of the outer peripheral surface of the oil-impregnated bearing 60 faces the curved portion 36 in the radial direction. Accordingly, a tapered space is formed in which the gap becomes narrower toward the lower side in the axial direction at the portion where the outer peripheral surface of the oil-impregnated bearing 60 and the curved portion 36 face each other in the radial direction. As a result, the lubricant that has oozed out on the outer peripheral surface on the upper side in the axial direction of the oil-impregnated bearing 60 is held in a capillary phenomenon that works by the outer peripheral surface of the oil-impregnated bearing 60 and the curved portion 36 of the housing 30.

  A substantially disk-shaped cap member 42 is fixed to the housing 30 by caulking on the upper side in the axial direction of the housing 30. A bearing holding portion 44 extending in a cylindrical shape toward the upper side in the axial direction is provided at the center portion of the cap member 42 by burring. An oil-impregnated bearing 80 is press-fitted into the inner peripheral surface of the bearing holding portion 44 and fixed.

  Thereby, the rotor holder 22 and the rotor magnet 26 are surrounded by the housing 30 and the cap member 42.

  The shaft 20 is rotatably supported by an oil-impregnated bearing 60 provided in the holding portion 38 of the housing 30 and an oil-impregnated bearing 80 provided in the bearing holding portion 44 of the cap member 42.

<Oil-impregnated bearing>
Next, the oil-impregnated bearings 60 and 80 will be described in detail.

  FIG. 2 is a plan view of the oil-impregnated bearing 60 on the power transmission unit 28 side (the lower side in the axial direction) of the brushless motor 1 in FIG. 1 according to the present embodiment. FIG. 3 is a cross-sectional view of the oil-impregnated bearing 60 illustrated in FIG. 2 according to the present embodiment, taken along line A-O-A ′. In FIG. 3, the lower side in the figure is the lower side in the axial direction.

  2 and 3, the oil-impregnated bearing 60 includes a substantially hollow cylindrical inner bearing 62 and an outer bearing 64 that fits with the outer peripheral surface of the inner bearing 62 on the inner peripheral surface thereof. The inner bearing 62 and the outer bearing 64 are made of a porous material such as a sintered material. Here, the porous material means a material having a large number of pores inside and on the surface thereof. The sintered material is a relatively brittle material formed by heating powder into a mold, and the corners of the oil-impregnated bearing 60 are chamfered from the viewpoint of preventing chipping.

  The inner bearing 62 and the outer bearing 64 are impregnated with a lubricant such as oil. The lubricant in this embodiment is oil. The oil content in the inner bearing 62 is preferably in the range of 18 vol% or more, and more preferably in the range of 23 vol% or more. Further, the oil content of the outer bearing 64 is preferably 40 vol% or more. In the present embodiment, the oil content of the inner bearing 62 is 23 vol%, and the oil content of the outer bearing 64 is 40 vol%.

  The radial thickness of the inner bearing 62 is provided substantially uniformly in the circumferential direction. In addition, the distance between the inner peripheral surface of the inner bearing 62 and the rotation center shaft 21 is substantially uniform in the circumferential direction, and the distance between the outer peripheral surface of the inner bearing 62 and the rotation center shaft 21 is equal to the circumference. It is substantially uniform in the direction. As a result, the force applied to the inner bearing 62 during processing and assembly is difficult to concentrate on a specific part. Therefore, a specific part of the inner bearing 62 is not distorted, and a hole inside the specific part is not biased and crushed, so that the oil-impregnated bearing 60 with high accuracy can be provided.

  A concave portion 66 that is recessed outward in the radial direction is formed on the inner peripheral surface of the outer bearing 64. The recess 66 is continuously formed over substantially the entire axial direction of the outer bearing 64. A cross-sectional shape obtained by cutting the recess 66 in a radial direction on a plane perpendicular to the rotation center axis is a curved surface shape. The recesses 66 are formed at six locations equally in the circumferential direction.

  The recess 66 and the outer peripheral surface of the inner bearing 62 are opposed to each other through a gap, and form a communication groove 68 that connects the space on the lower side in the axial direction of the inner bearing 62 and the space on the upper side in the axial direction of the inner bearing 62. Since the recesses 66 are provided at six locations, six communication grooves 68 are formed. The length in the radial direction between the most radially outer position in the recess 66 and the outer peripheral surface of the inner bearing 62 is 0.7 mm.

  The outer peripheral surface of the outer bearing 64 is provided with a communication portion 70 that is recessed radially inward over substantially the entire axial direction. In the present embodiment, four communication portions 70 are provided at equal intervals in the circumferential direction. The communication portion 70 is provided at a position that does not overlap the communication groove 68 in the circumferential direction with respect to the rotation center shaft 21.

  The end face of the outer bearing 64 is subjected to crushing processing. The crushing process is a process of reducing the porosity of the surface layer by reducing the size of the holes or reducing the number of holes on a certain surface. As a result, the porosity of the surface layer on the lower end surface in the axial direction and the upper end surface in the axial direction of the outer bearing 64 is smaller than the porosity of the surface layer on the inner peripheral surface of the outer bearing 64. With this configuration, it is difficult for the lubricant to ooze out from the end face of the outer bearing 64, and leakage and evaporation of the lubricant impregnated in the outer bearing 64 can be effectively prevented. Further, like the outer bearing 64, the end face of the inner bearing 62 is also subjected to crushing processing, and the leakage and evaporation of the lubricant can be more effectively prevented.

  A chamfering process is performed between the lower end surface in the axial direction of the outer bearing 64 and the inner peripheral surface of the outer bearing 64 to form a first inclined surface 72. Further, a chamfering process is performed between the axial upper end surface of the outer bearing 64 and the inner peripheral surface of the outer bearing 64 to form a second inclined surface 74. The radial lengths of the first inclined surface 72 and the second inclined surface 74 are substantially the same as the length of the outermost surface of the inner bearing 62 and the radially outer position of the recess 66.

  An outer inclined surface 75 is formed between the lower end surface in the axial direction of the outer bearing 64, the outer peripheral surface of the outer bearing 64, and the upper end surface in the axial direction of the outer bearing 64 and the outer peripheral surface of the outer bearing 64. Yes. The radial width of the outer inclined surface 75 is substantially the same as the depth of the communication portion 70.

  With the above-described configuration, only the portion that has been subjected to crushing processing, that is, the portion with fewer voids appearing on the surface of the oil-impregnated bearing 60, is directly exposed to the outside air on the lower end surface in the axial direction and the upper end surface in the axial direction of the outer bearing 64. ing. Therefore, leakage of the lubricant and evaporation can be effectively prevented.

  The axial length of the outer bearing 64 is longer than the axial length of the inner bearing 62. This is for preventing leakage of the lubricant. Details of the mechanism for preventing lubricant leakage will be described later.

  The lower end surface in the axial direction of the outer bearing 64 is located on the lower side in the axial direction as compared with the lower end surface in the axial direction of the inner bearing 62. Further, the upper end surface in the axial direction of the outer bearing 64 is positioned on the upper side in the axial direction as compared with the upper end surface in the axial direction of the inner bearing 62.

  The distance between the lower end surface in the axial direction of the outer bearing 64 and the lower end surface in the axial direction of the inner bearing 62, and the distance between the upper end surface in the axial direction of the outer bearing 64 and the upper end surface in the axial direction of the inner bearing 62 The distance between the axially lower end surface of the outer bearing 64 and the axially lower end surface of the inner bearing 62 is shorter. According to this configuration, the distance between the bearing surface of the inner bearing 62 on the lower side in the axial direction and the bearing surface of the inner bearing 82 on the upper side in the axial direction can be increased. As a result, there is an advantage that the shaft 20 hardly falls down and the rotation is stabilized. Further, the longer the outer bearing 64 is in the axial direction, the more the volume of the outer bearing 64 is increased and the amount of lubricant retained is increased. Further, in the motor structure as in this embodiment, there is an advantage that the holding amount of the lubricant can be increased without extending the outer shape of the brushless motor 1 by extending the outer bearing 64 inside the rotor holder 22.

  Hereinafter, a state when the oil-impregnated bearing 60 is mounted on the brushless motor 1 will be described.

  FIG. 4 is an enlarged cross-sectional view when the oil-impregnated bearing 60 according to the present embodiment is mounted on the brushless motor 1. In FIG. 4, the lower side in the figure is the power transmission unit 28 side (the lower side in the axial direction). An arrow C shown in the figure indicates the rotation of the shaft 20.

  Referring to FIG. 4, shaft 20 rotates in the direction of arrow C by the magnetic action of stator 50 and rotor magnet 26. When the shaft 20 rotates, the lubricant exudes from the inner peripheral surface of the inner bearing 62. The lubricant that has oozed out between the shaft 20 and the inner peripheral surface of the inner bearing 62 lubricates between the shaft 20 and the inner peripheral surface of the inner bearing 62, and the shaft 20 is rotationally supported.

  Here, as described above, the first washer 76 and the second washer 78 are fitted to the shaft 20 so as to restrict the movement of the shaft 20 in the axial direction, but the first washer 76 and the second washer 78 are fitted. The outer diameter of the inner bearing 62 is larger than the inner diameter of the inner bearing 62 and smaller than the inner diameter of the outer bearing 64. The first washer 76 is positioned on the lower side in the axial direction than the end surface on the upper side in the axial direction of the outer bearing 64. In other words, the first washer 76 is positioned so as to enter a recess that is recessed toward the lower side in the axial direction formed by the inner peripheral surface of the outer bearing 64 and the end surface on the upper side in the axial direction of the inner bearing 62. Yes. Further, the second washer 78 is located on the upper side in the axial direction from the lower end surface in the axial direction of the outer bearing 64. In other words, the second washer 78 is positioned so as to enter a hollow that is recessed toward the upper side in the axial direction formed by the inner peripheral surface of the outer bearing 64 and the lower end surface of the inner bearing 62 in the axial direction. Yes.

  When the shaft 20 rotates, the lubricant may move from the bearing portion along the shaft 20 to the lower side in the axial direction and the upper side in the axial direction. This is because the lubricant that oozes out from the oil-impregnated bearing 60 is pulled in the axial direction by the centrifugal force acting on the outer peripheral surface of the shaft 20. As described above, the first washer 76 and the second washer 78 are fitted to the shaft 20, and the lubricant that has moved in the axial direction has a surface facing the oil-impregnated bearing 60 of the first washer 76 and the second washer 78. Communicate. Since the surfaces of the first washer 76 and the second washer 78 facing the oil-impregnated bearing 60 have a diameter larger than that of the shaft 20, a strong centrifugal force acts on the lubricant. The lubricant reaching the radially outer ends of the first washer 76 and the second washer 78 is shaken off radially outward from the first washer 76 and the second washer 78 by centrifugal force.

  As described above, the outer bearing 64 is provided on the outer side in the radial direction of the surface of the first washer 76 and the second washer 78 that faces the oil-impregnated bearing 60, and is shaken off from the first washer 76 and the second washer 78. The lubricant adheres to the outer bearing 64. The lubricant adhering to the outer bearing 64 is absorbed into the outer bearing 64. In this way, a flow of the lubricant that is absorbed by the outer bearing 64 through the shaft 20 from the portion where the lubricant lubricates is formed. Therefore, in the oil-impregnated bearing 60 in this embodiment, the lubricant is prevented from leaking out of the bearing portion, and the life of the oil-impregnated bearing 60 can be extended.

  Referring again to FIG. 2, when the shaft 20 rotates about the rotation center shaft 21, the shaft 20 is caused by the flow of lubricant interposed between the outer peripheral surface of the shaft 20 and the inner peripheral surface of the inner bearing 62. Rotation supported. As a reaction for rotating and supporting the shaft 20, a pressure is applied to the inner peripheral surface of the inner bearing 62 to push the lubricant radially outward.

  When pressure as a reaction for rotating and supporting the shaft 20 is applied to the inner peripheral surface of the inner bearing 62, a part of the lubricant present in the inner bearing 62 and the outer bearing 64 is part of the inner bearing 62 and the outer bearing 64. Cannot saturate inside and ooze out to the surfaces of the inner bearing 62 and the outer bearing 64. According to the configuration of the present embodiment, the lubricant oozes out into the communication groove 68 located between the inner bearing 62 and the outer bearing 64. The lubricant that has oozed out is held in the communication groove 68. Further, a part of the lubricant oozes out and is retained in the communication part 70. The lubricant that has oozed out is held in the communication groove 68 and in the communication portion 70 and absorbed into the oil-impregnated bearing 60. Thereby, the leakage of the lubricant due to the pressure applied to the oil-impregnated bearing 60 during rotation can be prevented.

  In particular, when there is a communication groove 68 or a communication portion 70 on the radially outer side of the portion to which pressure is applied as a reaction for rotating and supporting the shaft 20 on the inner peripheral surface of the inner bearing 62, the lubricant is connected to the communication groove 68. Or it oozes out into the space of the communication part 70. As a result, the communication groove 68 and the communication portion 70 buffer the pressure as a reaction for rotating and supporting the shaft 20. Therefore, this pressure is hardly transmitted to the portion located radially outward of the communication groove 68 and the communication portion 70. On the other hand, a portion where neither the communication groove 68 nor the communication portion 70 exists in the radially outward portion of the portion to which pressure is applied as a reaction to support the shaft 20 on the inner peripheral surface of the inner bearing 62 is supported. This pressure is transmitted to the outer peripheral surface. As a result, a force for pushing out the lubricant in the oil-impregnated bearing 60 from the outer peripheral surface of the outer bearing 64 is generated. At this time, the lubricant may ooze out from the outer peripheral surface of the outer bearing 64. Then, the lubricant may leak out of the oil-impregnated bearing 60 through the holding portion 38 of the housing 30.

  In the oil-impregnated bearing 60 of the present embodiment, the concave portion 66 (communication groove 68) and the communication portion 70 are arranged so that their circumferential positions are different from each other. Thereby, compared with the case where the concave portion 66 (communication groove 68) and the communication portion 70 overlap each other in the circumferential direction, the portion of the outer peripheral surface of the outer bearing 64 where the pressure as a reaction is transmitted is supported. The area can be reduced. Therefore, the oil-impregnated bearing 60 of this embodiment has a structure that prevents the lubricant from oozing out to the outer peripheral surface of the outer bearing 64 to the maximum extent.

  In addition, when a load is always applied to the power transmission unit 28 from the same direction, the recess 66 (communication groove 68) and the communication unit 70 are made to correspond to the direction in which the load is applied so that the circumferential positions match. It is also possible to arrange.

  The oil-impregnated bearing 60 is often used near a heat source such as a stator. Further, as the shaft 20 rotates, frictional heat is generated in the portion where the lubrication is performed. Due to these factors, the oil-impregnated bearing 60 may be exposed to heat. Here, a large number of holes that are impregnated with the lubricant are formed inside the oil-impregnated bearing 60, but all the holes of the oil-impregnated bearing 60 may not be filled with the lubricant. For example, when the oil-impregnated bearing 60 is impregnated with the lubricant, the lubricant does not reach some holes, and the amount of the lubricant retained decreases as a result of the oil-impregnated bearing 60 being used for a long time. In the case where air bubbles are entrained in the lubricant when the shaft 20 rotates, air may exist inside the oil-impregnated bearing 60. Here, air has a high coefficient of thermal expansion and a low density compared to the lubricant. When air is present inside the oil-impregnated bearing 60 and the oil-impregnated bearing 60 is exposed to heat, the air may become a bubble to move the lubricant out of the oil-impregnated bearing 60.

  According to the configuration of the present embodiment, since the radial length between the inner peripheral surface of the communication groove 68 and the radially outermost portion of the recess 66 is 0.7 mm, the generated bubbles are Extrusion of the lubricant can be suppressed, and the lubricant is discharged from the communication groove 68 to the outside air.

  In the present embodiment, the radial length from the outer peripheral surface of the inner bearing 62 to the radially outermost portion of the recess 66 is 0.7 mm, but it may be 0.4 mm or more. When the radially outermost length in the radial direction of the inner peripheral surface of the inner bearing 62 and the recess 66 is 0.4 mm or more, only the generated bubbles can be discharged to the outside air without pushing out the lubricant. As a result, the lubricant retained in the communication groove 68 is not pushed out together with the bubbles, and the leakage of the lubricant can be prevented.

  By the way, when the shaft 20 rotates, the amount of lubricant retained may be unbalanced between the axially lower side and the axially upper side of the oil-impregnated bearing 60. The oil-impregnated bearing 60 in this embodiment is provided with a communication groove 68 on the inner peripheral side of the outer bearing 64 and a communication portion 70 on the outer peripheral surface of the outer bearing 64. Lubricant may ooze out into the communication groove 68 and the communication portion 70 due to pressure or thermal expansion as a reaction for rotating and supporting the shaft 20. At this time, the lubricant travels along the communication groove 68 and the communication portion 70 and moves to the side where the amount of lubricant retained is small.

  When the brushless motor 1 is stopped and the rotation of the shaft 20 is stopped, the lubricant located in the vicinity of the surfaces of the inner bearing 62 and the outer bearing 64 is caused by the capillarity or the like of the oil-impregnated bearing 62 and the outer bearing 64. Move inside.

  FIG. 5 is a plan view of the oil-impregnated bearing 80 on the upper side in the axial direction in FIG. 1.

  Referring to FIG. 5, the basic configuration of oil-impregnated bearing 60 on the power transmission unit 28 side and oil-impregnated bearing 80 on the side opposite to power transmission unit 28 is the same. The difference in configuration between the two is the thickness of the oil-impregnated bearing in the radial direction and the length of the oil-impregnated bearing in the axial direction. That is, since the load applied to the oil-impregnated bearing 80 is less than that of the oil-impregnated bearing 60 on the power transmission unit 28 side, the amount of the lubricant that oozes out is small. Further, expansion due to heat generated by the rotation of the shaft 20 hardly occurs, and the possibility that the lubricant leaks is relatively low. Therefore, the amount of lubricant retained in the oil-impregnated bearing 80 on the right side of the figure can be reduced to some extent as compared with the oil-impregnated bearing 60 on the power transmission unit 28 side.

  As mentioned above, although the Example of this invention was described, this invention is not necessarily restricted to this, A various change is possible in the range which does not impair the meaning of this invention.

  For example, in the present embodiment, the oil-impregnated bearing 60 is used in the so-called inner rotor type brushless motor 1 in which the rotor magnet 26 is disposed inside the stator 50, but is not limited thereto. You may use for the outer rotor type | mold with which a rotor magnet is arrange | positioned on the outer side of a stator, and the axial gap type brushless motor with which a stator and a rotor magnet are provided facing in an axial direction.

  In the present embodiment, the two oil-impregnated bearings 60 and 80 are used for the brushless motor 1, but the present invention is not limited to this. One oil-impregnated bearing may be provided, or three or more oil-impregnated bearings may be provided.

  Further, in this embodiment, two oil-impregnated bearings 60 are used for the brushless motor 1, and both of them are oil-impregnated bearings 60 and 80 according to the present invention. However, the present invention is not limited to this. For example, one of the bearings may be a ball bearing.

  In this embodiment, the recesses 66 are provided at six locations, but the present invention is not limited to this.

  In the present embodiment, the cross-sectional shape obtained by cutting the shape of the recess 66 along a plane orthogonal to the rotation center axis is a curved surface shape. However, the present invention is not limited to this. For example, various changes such as a V shape are possible.

  Further, in this embodiment, the recess 66 is provided with substantially the same width as the first inclined surface 72 and the second inclined surface 74, but the present invention is not limited to this. In the range where the radially outermost length of the inner peripheral surface of the inner bearing 62 and the concave portion 66 is maintained at 0.4 mm or more, the concave portion 66 is more than the first inclined surface 72 and the second inclined surface 74. The width may be narrow.

  Further, in this embodiment, the first washer 76 and the second washer 78 are sandwiched between the oil-impregnated bearing 60 on the lower side in the axial direction, and the third washer 96 and the fourth washer 98 are disposed on the oil-impregnated bearing 80 on the upper side in the axial direction. However, the present invention is not limited to this. For example, the number of washers may be one, two, three, or five or more.

  Further, in the present embodiment, the communication portion 70 is provided with substantially the same width as the outer inclined surface 75, but the present invention is not limited to this. It is only necessary that the communication portion 70 is radially outward from the outer inclined surface 75.

It is sectional drawing which cut | disconnected the brushless motor using the oil-impregnated bearing mechanism in this invention to the axial direction by the plane containing a rotation center axis | shaft. It is a top view of the oil-impregnated bearing by the side of the power transmission part of the brushless motor in this invention. FIG. 3 is a cross-sectional view of the oil-impregnated bearing illustrated in FIG. 2 according to the present invention, cut along line A-O-A ′ in FIG. 2. In the oil-impregnated bearing according to the present invention, it is a schematic diagram showing the flow of the lubricant when the brushless motor is driven. It is a top view of the oil-impregnated bearing of the axial direction other end side of the brushless motor in this invention. It is sectional drawing which shows the conventional oil-impregnated bearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Rotating part 3 Fixed part 6 Oil-impregnated bearing mechanism 20 Shaft 21 Rotation center shaft 22 Rotor holder 23 Cylindrical part 24 Fastening auxiliary member 26 Rotor magnet (permanent magnet)
28 Power transmission part 30 Housing 32 Hollow cylindrical part 34 Extension part 36 Curved part 38 Holding part 40 Projection part 42 Cap member 44 Bearing holding part 50 Stator 52 Circuit board 54 Electronic component 56 Insertion part 58 Connector 60 Oil-impregnated bearing (power transmission part side)
62 Inner bearing 64 Outer bearing 66 Recess 68 Communication groove 70 Communication portion 72 First inclined surface 74 Second inclined surface 75 Outer inclined surface 76 First washer 78 Second washer 80 Oil-impregnated bearing 82 Inner bearing 84 Outer bearing 86 Recessed portion 87 Communication groove 88 Communication part 96 Third washer 98 Fourth washer C Shaft rotation direction

Claims (18)

An oil-impregnated bearing mechanism,
A shaft,
An inner bearing made of a porous material having a substantially hollow cylindrical shape and having an inner peripheral surface serving as a bearing surface for rotatably supporting the shaft, and containing a lubricant, and a substantially hollow cylindrical shape whose inner peripheral surface is the inner surface An outer bearing made of a porous material that radially surrounds the outer peripheral surface of the bearing and that contains a lubricant, and an oil-impregnated bearing that includes:
Between the outer peripheral surface of the inner bearing and the inner peripheral surface of the outer bearing, at least one communicating with the outside and formed by a part of the outer peripheral surface of the inner bearing and a part of the inner peripheral surface of the outer bearing. The above communication groove is formed,
The communication groove is an oil-impregnated bearing mechanism that communicates a space on one end side in the axial direction of the inner bearing with a space on the other end side in the axial direction.   2. The oil-impregnated bearing mechanism according to claim 1, wherein the radial thickness of the inner bearing is substantially uniform in the circumferential direction.   The oil-impregnated bearing mechanism according to claim 1 or 2, wherein the outer bearing has a higher porosity than the inner bearing.   The oil-impregnated bearing mechanism according to any one of claims 1 to 3, wherein the inner bearing is made of a material having higher wear resistance than the outer bearing.   The oil-impregnated bearing mechanism according to any one of claims 1 to 4, wherein the porous material of the inner bearing is a sintered material. The outer bearing is
The porosity in the surface layer at the end surface on the one end side in the axial direction and the porosity in the surface layer at the end surface on the other end side in the axial direction are less than the porosity located in the surface layer on the inner peripheral surface. An oil-impregnated bearing mechanism according to any one of claims 1 to 5.   The communication groove is formed such that a recess formed by a part of the inner peripheral surface of the outer bearing being recessed radially outward is opposed to the outer peripheral surface of the inner bearing via a gap. The oil-impregnated bearing mechanism according to any one of claims 1 to 6, characterized in that: The oil-impregnated bearing mechanism according to claim 7, wherein a plurality of the communication grooves are provided at equal intervals in the circumferential direction.   The concave portion of the outer bearing has a curved shape recessed outward in the radial direction, and the radial length from the outer peripheral surface of the inner bearing to the most radially outer position in the concave portion is approximately 0.4 mm or more. The oil-impregnated bearing mechanism according to claim 7 or 8, wherein the oil-impregnated bearing mechanism is characterized. A first inclined surface is formed on the radially inner side of the end surface on the one axial side of the outer bearing,
A second inclined surface is formed on the radially inner side of the end surface on the other end side in the axial direction of the outer bearing,
The first inclined surface is formed between an end surface on one end side in the axial direction of the outer bearing and an outer peripheral surface of the inner bearing,
The second inclined surface is formed between an end surface on the other axial end side of the outer bearing and an outer peripheral surface of the inner bearing,
The oil-impregnated bearing mechanism according to any one of claims 1 to 9, wherein the communication groove is provided radially inward from the other end surface in the axial direction of the outer bearing and the end surface in the other end side. An oil-impregnated bearing mechanism according to any one of claims 1 to 10,
A washer is fitted to the shaft,
The end surface on the one end side in the axial direction of the outer bearing is located closer to the one end side in the axial direction than the end surface on the one end side in the axial direction of the inner bearing,
An outer diameter of the washer is larger than an inner diameter of the inner bearing and smaller than an inner diameter of the outer bearing;
At least a part of the washer is positioned on the other end side in the axial direction from the end surface on the one end side in the axial direction of the outer bearing and at one end side in the axial direction from the end surface on the one end side in the axial direction of the inner bearing, and at least on the outer peripheral surface of the washer An oil-impregnated bearing mechanism characterized in that a part thereof is opposed to the inner peripheral surface of the outer bearing or the first inclined surface in the radial direction. An oil-impregnated bearing mechanism according to any one of claims 1 to 11,
A rotor coupled to the shaft and comprising a permanent magnet;
A housing that fits and holds the outer peripheral surface of the outer bearing in a holding portion;
A brushless motor comprising: a stator coupled to the housing and facing the permanent magnet through a gap to generate a rotating magnetic field. The brushless motor according to claim 12,
A part of the outer peripheral surface of the outer bearing is recessed radially inward to form a space that communicates the space on one axial end side of the outer bearing with the space on the other axial end side of the outer bearing. A brushless motor characterized in that a communicating portion is formed. The brushless motor according to claim 13,
The brushless motor characterized in that a circumferential position of the recess and a circumferential position of the communication portion are different from each other. The brushless motor according to any one of claims 12 to 14,
The holding part is formed by burring processing,
A protruding portion that protrudes radially inward from the holding portion so as to cover a part of the end surface on the one axial end side of the outer bearing is formed on one axial end side of the holding portion of the housing. Brushless motor. The brushless motor according to any one of claims 12 to 15,
The housing includes an extending portion extending radially outward from the other axial end of the holding portion,
The rotor has a substantially bottomed cylindrical shape, and includes a rotor holder to which the permanent magnet is fixed on an outer peripheral surface thereof.
The rotor holder is opened toward the oil-impregnated bearing, and the opening side end face thereof is opposed to the extending portion through a gap. The brushless motor according to any one of claims 12 to 15,
The housing is molded by pressing,
The holding portion of the housing is positioned on one end side in the axial direction from the end surface on the other end side in the axial direction of the outer bearing,
A brushless motor, wherein a curved portion that curves radially outward from the holding portion is formed on the other axial end side of the holding portion of the housing. A brushless motor according to any one of claims 12 to 17,
The housing has a substantially hollow cylindrical shape, holds the stator on the inner peripheral surface on the other axial end side from the holding portion,
The permanent magnet is opposed to the stator via a gap inward in the radial direction of the stator,
The housing is connected to a cap member on the other axial end side from the stator,
The oil-impregnated bearing is further fixed to the cap member,
The brushless motor, wherein the shaft is inserted radially inward of the oil-impregnated bearing.

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