JP2013032835A - Fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the vibration of a fan associated with an increase of a wind volume caused by the high-speed rotation of the cooling fan.SOLUTION: The fan includes a motor and an impeller, the static part of the motor is composed of a stator 32 and a bearing 44, the bearing comprises a sleeve 47 being a metal sintered compact and a cylindrical bearing housing 48, and a rotating part has a rotor magnet, a shaft 41 inserted into the sleeve and a thrust plate 42 which expands to the radial direction from the lower end of the shaft. A radial dynamic-pressure bearing for generating the fluid dynamic pressure of lubricating oil flowing to the lower part in the axial direction is constituted in a radial gap between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, a thrust dynamic-pressure bearing for generating the fluid dynamic pressure of lubricating oil flowing to the inside in the radial direction is constituted in a thrust gap between the lower surface of the sleeve and the upper surface of the thrust plate, a circulation hole 445 extending in the axial direction is located between the sleeve and the bearing housing, and the width in the radial direction of the radial gap is ≥5 μm and ≤20 μm.

Description

  The present invention relates to a fan that generates a flow of air.

  Conventionally, a cooling fan for cooling electronic components is provided inside a housing of various electronic devices. A motor part of an axial fan disclosed in Japanese Patent Application Laid-Open No. 2009-213225 includes a base part, an armature, a substantially cylindrical bearing holding part, two ball bearings, and a rotor part. The bearing holding portion is fixed to the center of the base portion. Two ball bearings are fixed to the inner surface of the bearing holding portion, and an armature is fixed to the outer surface. The rotor portion is rotatably supported with respect to the bearing holding portion when the shaft is inserted into the ball bearing. An annular groove is provided in the base portion so as to surround the periphery of the bearing holding portion. A spiral coil spring is placed in the groove. The upper end of the coil spring is in axial contact with the insulator of the armature. Thereby, when a rotor part rotates, the vibration of an armature is absorbed by a coil spring, and the vibration of an axial fan can be reduced.

A spindle motor bearing device disclosed in Japanese Patent Laid-Open No. 2005-155912 includes a shaft, a thrust plate, a sleeve, and a bottomed cylindrical housing. The shaft is fitted into the sleeve. The housing houses the sleeve. The thrust plate is formed at the lower end of the shaft. A dynamic pressure generating groove is formed on the inner peripheral surface of the sleeve, and a radial dynamic pressure bearing is formed between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve. A thrust dynamic pressure generating groove is formed on the lower end surface of the sleeve and the bottom surface of the inner periphery of the housing. A thrust dynamic pressure bearing is formed between the lower end surface of the sleeve, the thrust plate, and the upper surface, and between the lower surface of the thrust plate and the bottom surface of the inner periphery of the housing.
JP 2009-213225 A JP 2005-155912 A

  By the way, in recent years, the amount of heat generated from electronic devices is increasing with the performance of electronic devices such as servers. For this reason, it is required to increase the air volume by rotating the cooling fan in the electronic device at a high speed. However, with the high speed rotation of the cooling fan, a large vibration is generated in the cooling fan, which affects other devices in the electronic device. For example, an error occurs in reading and writing of the disk drive device due to vibration of the cooling fan.

  One of the main objects of the present invention is to reduce fan vibration.

  A fan according to an exemplary first aspect of the present invention includes a motor and an impeller that has a plurality of blades and that rotates about the central axis by the motor to generate an air flow. Comprises a stationary part and a rotating part rotatably supported by the stationary part, the stationary part comprising a stator and a bearing part disposed inside the stator, wherein the bearing part is A sleeve that is a sintered metal body, and a bearing housing that covers an outer peripheral surface of the sleeve, the rotating portion being disposed on the radially outer side of the stator, and the upper portion being directly or 1 A shaft fixed to the impeller via at least one member and inserted into the sleeve; a thrust plate extending radially outward from the lower end of the shaft and facing the lower surface of the sleeve in the axial direction; A radial dynamic pressure bearing portion that generates a fluid dynamic pressure of the lubricating oil directed downward in the axial direction in a radial gap between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft is configured. A thrust dynamic pressure bearing portion configured to generate a fluid dynamic pressure of the lubricating oil radially inward in a thrust gap between a lower surface and the upper surface of the thrust plate; and the outer peripheral surface of the sleeve and the bearing housing Between them is a circulation hole extending in the axial direction from the upper surface of the sleeve to the lower surface, and the radial width of the radial gap is not less than 5 μm and not more than 20 μm.

  A fan according to an exemplary second aspect of the present invention includes a motor and an impeller that has a plurality of blades and that rotates about the central axis by the motor to generate an air flow. Comprises a stationary part and a rotating part rotatably supported by the stationary part, the stationary part comprising a stator and a bearing part located inside the stator, and the bearing part, A sleeve that is a sintered body of metal, and a bearing housing that covers an outer peripheral surface of the sleeve, wherein the rotating part is a rotor magnet that is positioned on the radially outer side of the stator, and the upper part is directly or more than one A shaft that is fixed to the impeller via the member and inserted into the sleeve, and a thrust plate that extends radially outward from the lower end of the shaft and faces the lower surface of the sleeve in the axial direction. A radial dynamic pressure bearing portion for generating fluid dynamic pressure of lubricating oil in a radial gap between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, and the lower surface of the sleeve and the upper surface of the thrust plate A thrust dynamic pressure bearing portion that generates fluid dynamic pressure of the lubricating oil is formed in a thrust gap between the sleeve and the outer peripheral surface of the sleeve and the bearing housing, from the upper surface of the sleeve to the lower surface A circulation hole extending in the axial direction is located, and when the rotating portion rotates, the lubricating oil passes through the radial gap, the gap on the upper surface of the sleeve, the circulation hole, and the thrust gap in order. Circulates into the gap.

  According to the present invention, fan vibration can be reduced.

FIG. 1 is a cross-sectional view of a fan according to an embodiment. FIG. 2 is a sectional view of the bearing mechanism. FIG. 3 is an enlarged sectional view showing a part of the bearing mechanism. FIG. 4 is a cross-sectional view of the bearing portion. FIG. 5 is a bottom view of the bearing portion. FIG. 6 is a plan view of the thrust cap. FIG. 7 is an enlarged sectional view showing a part of the bearing mechanism. FIG. 8 is a diagram illustrating a simulation result of vibration generated in the fan. FIG. 9 is a diagram illustrating a simulation result of vibration generated in the fan. FIG. 10 is a diagram illustrating a simulation result of vibration generated in the fan. FIG. 11 is a diagram illustrating a simulation result of vibration generated in the fan. FIG. 12 is a diagram illustrating a simulation result of vibration generated in the fan according to the comparative example. FIG. 13 is a diagram showing the relationship between the flow rate of the lubricating oil circulating when the motor is driven and the radial width of the radial gap.

  In the present specification, the upper side of FIG. 1 in the direction of the central axis of the motor is simply referred to as “upper side”, and the lower side is simply referred to as “lower side”. Note that the vertical direction does not indicate the positional relationship or direction when incorporated in an actual device. A direction parallel to the central axis is referred to as an “axial direction”, a radial direction centered on the central axis is simply referred to as “radial direction”, and a circumferential direction centered on the central axis is simply referred to as “circumferential direction”.

  FIG. 1 is a cross-sectional view of an axial fan 1 according to an embodiment of the present invention. Hereinafter, the axial fan 1 is simply referred to as “fan 1”. The fan 1 includes a motor 11, an impeller 12, a housing 13, a plurality of support ribs 14, and a base portion 15. The housing 13 surrounds the outer periphery of the impeller 12. The housing 13 is connected to the base portion 15 via the support rib 14. The plurality of support ribs 14 are arranged in the circumferential direction. The base portion 15 is a member connected to the support rib 14. The motor 11 is fixed on the base portion 15.

  The impeller 12 is made of resin, and includes a substantially covered cylindrical cup 121 and a plurality of wings 122. The cup 121 covers the outside of the motor 11. The cup 121 also serves as a part of the rotating part 2 of the motor 11 described later. The cup 121 has a top surface portion 123 and a side wall portion 124. The top surface portion 123 extends perpendicular to the central axis J1. The side wall portion 124 extends downward from the outer edge portion of the top surface portion 123. The plurality of blades 122 extend radially outward from the outer peripheral surface of the side wall portion 124 around the central axis J1. The cup 121 and the plurality of blades 122 are configured as a continuous member by resin injection molding.

  A hole 125 is provided on the top surface of the top surface 123. A weight 129 is disposed in the hole 125. The weight 129 is an adhesive containing a metal having a large specific gravity such as tungsten. The weight 129 is also arranged on the radially inner side of the lower end portion 124a of the side wall portion 124. By arranging the weights 129 at the upper and lower portions of the impeller 12, the imbalance between the impeller 12 and the rotating portion 2 of the motor 11 can be reduced. Thus, by performing the two-surface balance correction, it is possible to suppress the vibration of the fan 1 due to the deviation of the center of gravity of the impeller 12 and the motor 11 from the central axis J1. Hereinafter, the lower end portion 124a and the hole portion 125 of the side wall portion 124 where the weight 129 is disposed are referred to as “balance correction portions 124a and 125”.

  In the fan 1, the impeller 12 is rotated about the central axis J <b> 1 by the motor 11, whereby an air flow is generated from the upper side to the lower side.

  The motor 11 is an outer rotor type three-phase motor. The motor 11 has a rotating part 2, a stationary part 3, and a bearing mechanism 4. As will be described later, the bearing mechanism 4 can be regarded as being constituted by a part of the rotating part 2 and a part of the stationary part 3. The rotating unit 2 includes a substantially cylindrical metal yoke 21, a rotor magnet 22, and a cup 121. The yoke 21 is fixed inside the cup 121. The rotor magnet 22 is fixed to the inner peripheral surface of the yoke 21. The rotor magnet 22 is located on the radially outer side of the stator 32 described later. The rotating part 2 is supported via the bearing mechanism 4 so as to be rotatable with respect to the stationary part 3 around the central axis J1.

  The stationary part 3 includes a substantially cylindrical bearing holding part 31, a stator 32, and a circuit board 33. A lower portion of the bearing holding portion 31 is fixed to an inner peripheral surface that defines a central hole portion of the base portion 15. The stator 32 is fixed to the outer peripheral surface of the bearing holding portion 31 on the upper side of the base portion 15. The stator 32 includes a stator core 321 and a plurality of coils 322 formed on the stator core 321. Stator core 321 is formed of a laminated steel plate. A circuit board 33 is fixed to the lower part of the stator 32. By attaching a lead wire from the coil 322 to a pin (not shown) inserted into the circuit board 33, the stator 32 and the circuit board 33 are electrically connected. The lead wire of the coil 322 may be directly connected to the circuit board. When the motor 11 is driven, a rotational force is generated between the rotor magnet 22 and the stator 32.

  An annular magnetic member 331 is disposed on the upper surface of the circuit board 33. The magnetic member 331 is located below the rotor magnet 22. Further, when the motor 11 is stationary, the magnetic center position of the stator 32 is positioned below the magnetic center position of the rotor magnet 22 in the axial direction. In the fan 1, a magnetic attractive force that attracts the rotor magnet 22 downward is generated between the rotor magnet 22 and the stator 32 and between the rotor magnet 22 and the magnetic member 331. Thereby, when the fan 1 rotates, the force by which the impeller 12 floats with respect to the stationary part 3 can be reduced.

  FIG. 2 is an enlarged sectional view showing the vicinity of the bearing mechanism 4. The bearing mechanism 4 includes a shaft 41, an annular thrust plate 42, a bearing portion 44, a thrust cap 45 that is a cap member, and a lubricating oil 46. As shown in FIG. 1, the upper portion of the shaft 41 is indirectly fixed to the top surface portion 123 of the impeller 12 through a bushing 25 formed of metal. As shown in FIG. 2, the thrust plate 42 is fixed to the lower portion of the shaft 41. The thrust plate 42 extends radially outward from the lower end of the shaft 41. The thrust plate 42 is opposed to a lower surface 472 of a sleeve 47 (described later) of the bearing portion 44 in the axial direction. The upper surface of the thrust plate 42 has a substantially annular surface 422 that surrounds the shaft 41 and is perpendicular to the central axis J1. Hereinafter, the surface 422 is referred to as an “upper annular surface 422”. The lower surface of the thrust plate 42 has a substantially annular surface 423 that is perpendicular to the central axis J1. Hereinafter, this surface is referred to as a “lower annular surface 423”. The bearing portion 44 is disposed on the radially inner side of the stator 32. The shaft 41 and the thrust plate 42 are also a part of the rotating unit 2 shown in FIG. The bearing portion 44 and the thrust cap 45 are also part of the stationary portion 3.

  The bearing portion 44 shown in FIG. 2 includes a cylindrical sleeve 47 that is a metal sintered body, and a cylindrical bearing housing 48. The sleeve 47 is impregnated with a lubricating oil 46. The bearing housing 48 covers the outer peripheral surface 473 of the sleeve 47. The bearing housing 48 has a substantially annular annular upper portion 481 that extends radially inward on the upper side of the sleeve 47. The bearing housing 48 is fixed to the inner peripheral surface of the bearing holding portion 31. Below the annular upper portion 481, the inner peripheral surface 482 of the bearing housing 48 faces the outer peripheral surface 473 of the sleeve 47 in the radial direction.

  A plurality of grooves extending in the axial direction are formed on the outer peripheral surface 473 of the sleeve 47. The plurality of grooves extend from the upper surface 474 of the sleeve 47 to the lower surface 472. When the inner peripheral surface 482 of the bearing housing 48 contacts the outer peripheral surface 473 of the sleeve 47, the plurality of grooves become the plurality of circulation holes 445. That is, a plurality of circulation holes 445 are configured by the surfaces constituting the plurality of grooves and the inner peripheral surface 482 of the bearing housing 48. The plurality of circulation holes 445 are provided between the outer peripheral surface 473 of the sleeve 47 and the inner peripheral surface 482 of the bearing housing 48. Each circulation hole 445 extends in the axial direction from the upper surface 474 of the sleeve 47 to the lower surface 472. The plurality of circulation holes 445 are arranged at approximately equal intervals in the circumferential direction.

  The lower surface 472 of the sleeve 47 has a substantially annular shape centered on the central axis J1. The shaft 41 is inserted into the sleeve 47. In the present embodiment, the length of the sleeve 47 in the axial direction is about 13.0 mm. The inner and outer diameters of the sleeve 47 are about 3.0 mm and about 6.7 mm, respectively. The outer diameter of the thrust plate 42 is about 6.6 mm.

  The thrust cap 45 is disposed inside the lower end portion of the bearing housing 48. The outer peripheral surface of the thrust cap 45 is fixed to the lower end portion of the inner peripheral surface 482 of the bearing housing 48. The thrust cap 45 closes the lower portion of the bearing housing 48. In other words, the thrust cap 45 is the bottom of the bearing mechanism 4, that is, the bearing bottom. The thrust cap 45 faces the lower annular surface 423 of the thrust plate 42 in the axial direction.

  In the bearing mechanism 4, a radial gap 51 is formed between the inner peripheral surface 471 of the sleeve 47 and the outer peripheral surface 411 of the shaft 41. The upper annular surface 422 of the thrust plate 42 and the lower surface 472 of the sleeve 47 face each other in the axial direction. A gap 52 is formed between the upper annular surface 422 and the lower surface 472. Hereinafter, the gap 52 is referred to as a “first lower thrust gap 52”. The lower annular surface 423 of the thrust plate 42 and the upper surface 451 of the thrust cap 45 face each other in the axial direction. A gap 53 is formed between the lower annular surface 423 and the upper surface 451. Hereinafter, the gap 53 is referred to as a “second lower thrust gap 53”. The sum of the widths in the axial direction of the first lower thrust gap 52 and the second lower thrust gap 53 is not less than 10 μm and not more than 40 μm. A gap 54 is formed between the outer peripheral surface of the thrust plate 42 and the inner peripheral surface of the thrust cap 45. Hereinafter, the gap 54 is referred to as a “side gap 54”.

  FIG. 3 is an enlarged view showing the vicinity of the upper portion of the bearing portion 44. An inner peripheral surface 481a of the annular upper portion 481 of the bearing housing 48 is an inclined surface whose diameter gradually increases upward. In other words, the inner peripheral surface 481a is inclined radially inward toward the lower side. Hereinafter, the inner peripheral surface 481a is referred to as a “first inclined surface 481a”. On the upper part of the inner peripheral surface 471 of the sleeve 47, an inclined surface 471a whose diameter gradually increases upward is provided. In other words, the inclined surface 471a is inclined radially inward toward the lower side. Hereinafter, the inclined surface 471a is referred to as a “second inclined surface 471a”. The angle formed between the first inclined surface 481a and the central axis J1 is larger than the angle formed between the second inclined surface 471a and the central axis J1.

  Between the first inclined surface 481a and the outer peripheral surface 411 of the shaft 41, one seal gap 55 is formed in which the radial width gradually increases upward. The seal gap 55 has an annular shape centered on the central axis J1. Adjacent to the lower side of the seal gap 55, a gap 56 is formed between the outer peripheral surface 411 of the shaft 41 and the second inclined surface 471a. In the seal gap 55, a seal portion 55a that holds the lubricating oil 46 is formed by utilizing capillary action. Since the seal portion 55a is configured around the shaft 41, leakage of the lubricating oil 46 from the seal portion 55a is suppressed by centrifugal force. The seal gap 55 serves as an oil buffer that holds a large amount of the lubricating oil 46.

  As shown in FIG. 2, the motor 11 forms one bag structure 5 in which a seal gap 55, a radial gap 51, a first lower thrust gap 52, a side gap 54, and a second lower thrust gap 53 are connected to each other. The lubricating oil 46 is continuously present in the bag structure 5. In the bag structure 5, the interface of the lubricating oil 46 is formed only in the seal gap 55.

  As shown in FIG. 3, a radially extending gap 501 is formed between the lower surface of the bushing 25 fixed to the upper portion of the shaft 41 and the upper surface of the annular upper portion 481 of the bearing portion 44. A gap 502 extending in the axial direction is formed between the outer peripheral surface of the bushing 25 and the inner peripheral surface of the bearing holding portion 31. The seal portion 55a communicates with the external space through the gaps 501 and 502. The external space here refers to the space above the stator 32 in FIG. By providing the gaps 501 and 502, it is possible to suppress the movement of the air including the lubricating oil vaporized from the seal portion 55 a to the outside of the bearing mechanism 4. As a result, evaporation of the lubricating oil 46 in the bearing mechanism 4 can be suppressed.

  FIG. 4 is a longitudinal sectional view of the sleeve 47. In FIG. 4, the inner peripheral surface 471 of the sleeve 47 is also drawn. A herringbone-shaped first radial dynamic pressure groove row 711 and a second radial dynamic pressure groove row 712 are provided on the upper and lower portions of the inner peripheral surface 471 of the sleeve 47. The first radial dynamic pressure groove array 711 has a herringbone shape that is asymmetric in the vertical direction. In the upper part of the radial gap 51 shown in FIG. 2, the first radial dynamic pressure groove array 711 constitutes an upper radial dynamic pressure bearing portion 681 that generates fluid dynamic pressure of the lubricating oil 46 going downward in the axial direction. The second radial dynamic pressure groove array 712 has a herringbone shape that is symmetrical in the vertical direction. A lower radial dynamic pressure bearing portion 682 is configured by the second radial dynamic pressure groove array 712 below the radial gap 51. Hereinafter, the upper radial dynamic pressure bearing portion 681 and the lower radial dynamic pressure bearing portion 682 are collectively referred to as “radial dynamic pressure bearing portion 68”.

  The fluid dynamic pressure by the upper radial dynamic pressure bearing portion 681 positioned at the upper portion of the radial gap 51 is larger than the fluid dynamic pressure by the lower radial dynamic pressure bearing portion 682 positioned at the lower portion of the radial gap 51. For this reason, in the radial dynamic pressure bearing portion 68 as a whole, fluid dynamic pressure of the lubricating oil 46 is generated in the axially downward direction. In the axial direction, the radial dynamic pressure bearing portion 68 is located between the two balance correction portions 124a and 125 in FIG. In the radial direction, the upper radial dynamic pressure bearing portion 681 overlaps the center of gravity of the motor 11 and the impeller 12.

  FIG. 5 is a bottom view of the sleeve 47. The lower surface 472 of the sleeve 47 is provided with a herringbone-shaped first thrust dynamic pressure groove row 721. In the first lower thrust gap 52 shown in FIG. 2, a first lower thrust dynamic pressure bearing portion 691 that generates fluid dynamic pressure in the thrust direction (axial direction) with respect to the lubricating oil 46 by the first thrust dynamic pressure groove array 721 is provided. Composed. As shown in FIG. 5, in the first thrust dynamic pressure groove row 721, the width in the radial direction of the portion 721c radially outside the circumferential tip 721b of each first thrust dynamic pressure groove 721a is larger than that of the tip 721b. It is larger than the width in the radial direction of the portion 721d on the radially inner side. As a result, in the first lower thrust dynamic pressure bearing portion 691 shown in FIG. 2, fluid dynamic pressure of the lubricating oil 46 is generated inward in the radial direction. The first thrust dynamic pressure groove array 721 is not limited to the herringbone shape, and may be a spiral-in groove array. Also in this case, in the first lower thrust dynamic pressure bearing portion 691, fluid dynamic pressure of the lubricating oil 46 is generated inward in the radial direction.

  FIG. 6 is a plan view of the thrust cap 45. A herringbone-shaped second thrust dynamic pressure groove array 722 (see FIG. 6) is provided on the upper surface 451 of the thrust cap 45, that is, the upper surface of the bottom of the bag structure 5 of FIG. In the second lower thrust gap 53, the second lower thrust dynamic pressure bearing portion 692 that generates fluid dynamic pressure in the thrust direction (axial direction) with respect to the lubricating oil 46 is configured by the second thrust dynamic pressure groove array 722. The second thrust dynamic pressure groove array 722 is not limited to the herringbone shape, and may be a spiral-in groove array.

  When the motor 11 is driven, the shaft 41 is supported in the radial direction by the radial dynamic pressure bearing portion 68. The first lower thrust dynamic pressure bearing portion 691 and the second lower thrust dynamic pressure bearing portion 692 support the thrust plate 42 existing above the bottom of the bag structure 5 in the thrust direction. As a result, the rotating part 2 and the impeller 12 of FIG. 1 are supported so as to be rotatable with respect to the stationary part 3.

  When the motor 11 is driven, the lubricating oil 46 passes through the radial gap 51, the gap 446 between the lower surface of the annular upper portion 481 and the upper surface 474 of the sleeve 47, the circulation hole 445, and the first lower thrust gap 52 shown in FIG. Circulate. In other words, the gap 446 between the lower surface of the annular upper portion 481 and the upper surface 474 of the sleeve 47 is a gap on the upper surface 474 of the sleeve 47, and is hereinafter referred to as “over-sleeve gap 446”. In the present embodiment, a plurality of grooves extending in the radial direction from the inner peripheral surface 471 of the sleeve 47 to the outer peripheral surface 473 are formed on the upper surface 474 of the sleeve 47. The radially outer ends of the plurality of grooves are connected to the upper ends of the plurality of circulation holes 445. When the lower surface of the annular upper portion 481 contacts the upper surface 474 of the sleeve 47, the plurality of grooves become the sleeve upper gap 446.

  As shown in FIG. 4, a part of the first radial dynamic pressure groove array 711 exists below the second inclined surface 471a. When the shaft 41 shown in FIG. 3 is slightly tilted when the fan 1 is driven, it is between the portion that approaches the second inclined surface 471a of the outer peripheral surface 411 of the shaft 41 and the portion corresponding to the corresponding portion of the second inclined surface 471a. In the gap 56, fluid dynamic pressure is generated by the first radial dynamic pressure groove array 711. As a result, the shaft 41 is supported by the second inclined surface 471a. As described above, when the shaft 41 is inclined during the rotation of the rotating portion 2, the second inclined surface 471 a extends along the outer peripheral surface 411 of the shaft 41 in the gap 56 adjacent to the lower side of the seal gap 55. Strong contact with the upper portion of the bearing portion 44 is prevented.

  FIG. 7 is an enlarged sectional view showing the vicinity of the thrust plate 42. The upper surface of the thrust plate 42 has an inclined surface 422a located at the outer edge. The inclined surface 422a is adjacent to the radially outer side of the upper annular surface 422. The inclined surface 422a is inclined downwardly outward in the radial direction. The inclined surface 422a faces the outer edge portion of the lower surface 472 of the sleeve 47 in the axial direction. The lower surface of the thrust plate 42 has an inclined surface 423a located at the outer edge. The inclined surface 423a is adjacent to the radially outer side of the lower annular surface 423. The inclined surface 423a is inclined upward toward the radially outer side. By providing the inclined surface 422 a at the outer edge of the upper surface of the thrust plate 42, it is possible to prevent the thrust plate 42 from coming into strong contact with the lower surface 472 of the sleeve 47 when the shaft 41 is inclined during the rotation of the rotating unit 2. .

  FIG. 8 is a simulation result of vibration generated in the fan 1 when the radial gap 51 has a radial width of 3 μm. The horizontal axis indicates the frequency of vibration, and the vertical axis indicates the amplitude of each frequency component of vibration. 9 to 11 show simulation results of vibrations generated in the fan 1 when the radial gap 51 is 4 μm, 5 μm, and 6 μm. FIG. 12 is a simulation result of vibrations generated in a fan of a comparative example on which a motor having a ball bearing is mounted.

  As shown by a curve 90 in FIG. 12, in the vibration generated in the fan having a ball bearing, there are a plurality of peaks in the range of 750 Hz to 1250 Hz. In FIG. 12, reference numerals 901 to 904 are attached in order from the peak on the right side. On the other hand, in the bearing mechanism 4 with the radial gap widths of 3 μm and 4 μm, the peaks 911 to 914 corresponding thereto are lower than the peaks 901 to 904 in FIG. 12 as shown in FIGS. I understand. Furthermore, in the bearing mechanism 4 with the radial gap 51 having a width of 5 μm and 6 μm, as shown in FIGS. 10 and 11, peaks are present at positions corresponding to the two peaks 901 and 904 located on the right and left sides of FIG. It turns out that it does not exist. Further, it can be seen that the heights of the peaks 912 and 913 corresponding to the remaining two peaks 902 and 903 are half or less.

  As described above, the fan 1 uses the bearing mechanism 4 that is a fluid dynamic pressure bearing mechanism, and a ball bearing is conventionally used due to a so-called damper effect caused by the lubricating oil 46 between the shaft 41 and the bearing portion 44. The vibration can be reduced compared to the fans. As a result, the power consumption of the fan 1 can be suppressed. In particular, by setting the radial width of the radial gap 51 to 5 μm or more, vibration can be sufficiently reduced. The radial width of the radial gap 51 is 20 μm or less in order to generate a sufficient fluid dynamic pressure in the radial gap 51. Preferably, the radial width of the radial gap 51 is not less than 5 μm and not more than 10 μm.

  FIG. 13 is a diagram showing the relationship between the flow rate of the lubricating oil 46 circulated when the motor 11 is driven and the radial width of the radial gap 51. The horizontal axis in FIG. 13 indicates the radial width of the radial gap 51, and the vertical axis indicates the flow rate of the lubricating oil 46 flowing through the radial gap 51. In FIG. 13, the flow rate when the lubricating oil 46 flows upward in the radial gap 51 is positive, and the flow rate when the lubricating oil 46 flows downward is negative. As shown in FIG. 13, if the radial width of the radial gap 51 is larger than 5 μm (not including 5 μm), the lubricating oil 46 flows upward in the radial gap 51.

  If the radial width of the radial gap 51 is larger than 5 μm, the lubricating oil 46 flows upward in the radial gap 51, and the radial gap 51, the sleeve upper gap 446, the circulation hole 445, and the first lower thrust gap 52. Are circulated to the radial gap 51 in this order. When the bubbles are entrained in the lubricating oil 46 by the rotation of the shaft 41, the lubricating oil 46 circulates to discharge the bubbles in the lubricating oil 46 to the outside of the bearing mechanism 4 through the seal gap 55. it can. Therefore, more preferably, the radial width of the radial gap 51 is larger than 5 μm and not larger than 20 μm.

  In the seal gap 55 adjacent above the radial gap 51, the pressure of the lubricating oil 46 is equal to the atmospheric pressure. Accordingly, the pressure of the lubricating oil 46 at the upper end portion of the radial gap 51 is substantially equal to the atmospheric pressure. Since the lubricating oil 46 flows upward in the radial gap 51, the pressure of the lubricating oil 46 at the lower end portion of the radial gap 51 is higher than the pressure of the lubricating oil 46 at the upper end portion of the radial gap 51. For this reason, the pressure of the lubricating oil 46 at the lower end of the radial gap 51 becomes higher than the atmospheric pressure. In the fan 1, the lubricating oil 46 circulates through the radial gap 51, the sleeve upper gap 446, the circulation hole 445, and the first lower thrust gap 52 in this order, so that the lubricating oil 46 at the lower end of the radial gap 51 is reduced. It is possible to prevent the pressure from becoming negative.

  By the way, in the case of the bearing mechanism in which the seal part is provided at the upper part and the lower part of the bearing part, an advanced design is required to prevent leakage of the lubricating oil due to a pressure difference between the seal parts. On the other hand, since the bearing mechanism 4 of the motor 11 has a so-called full-fill structure in which the seal portion 55a is only one place, the leakage of the lubricating oil 46 can be easily prevented. Further, the position of the liquid level of the lubricating oil 46 in the seal portion 55a can be kept constant. The evaporation of the lubricating oil 46 can be suppressed as compared with the case where a plurality of seal portions are provided. In particular, since the seal portion 55a is provided inside the motor 11, the seal portion 55a is prevented from being exposed to the air flow when the fan 1 is driven. As a result, evaporation of the lubricating oil 46 can be further suppressed. It is also possible to prevent foreign matter from entering the seal portion 55a. In the bearing mechanism 4, since the seal portion 55 a is formed around the shaft 41, the lubricating oil is separated from the seal portion 55 a by centrifugal force as compared with the case where the seal portion is formed radially away from the shaft 41. 46 is prevented from leaking.

  When the sum of the axial widths of the first lower thrust gap 52 and the second lower thrust gap 53 is not less than 10 μm and not more than 40 μm, fluid dynamic pressure can be generated while ensuring a damper effect by the lubricating oil 46. . In the bearing mechanism 4, by increasing the radial gap 51, the pressure of the lubricating oil 46 at the lower end portion of the radial gap 51 decreases, but the radial gap 51 is increased and the first lower thrust gap 52 and the second lower thrust gap are increased. By increasing the sum of the widths in the axial direction of 53, the pressure drop of the lubricating oil 46 at the lower end of the radial gap 51 can be suppressed.

  Even if the radial gap 51 is widened, the shaft 41 can be sufficiently supported by providing the second inclined surface 471a in which a part of the first radial dynamic pressure groove row 711 exists on the inner peripheral surface 471 of the sleeve 47. Can do. As a result, even if the fan 1 rotates at a high speed or rotates at a high temperature, it is possible to prevent a decrease in bearing rigidity.

  Since the motor 11 is a three-phase motor, the motor 11 can be rotated at high speed. As a result, it is possible to easily shift the frequency band that affects other devices of the electronic device on which the fan 1 is mounted and the frequency of vibration generated in the motor 11.

  In the motor 11, by providing the magnetic member 331, a magnetic attractive force is generated downward with respect to the rotor magnet 22. Thereby, when the fan 1 is driven, the force that the impeller 12 is lifted with respect to the stationary portion 3 can be suppressed, and an increase in bearing loss in the first lower thrust dynamic pressure bearing portion 691 can be suppressed. Further, since the magnetic center of the stator 32 is positioned below the magnetic center of the rotor magnet 22, a magnetic attractive force is generated downward with respect to the rotor magnet 22. Thereby, the increase in the bearing loss in the first lower thrust dynamic pressure bearing portion 691 can be further suppressed.

  Since the radial dynamic pressure bearing portion 68 is positioned between the two balance correction portions 124a and 125 in the axial direction, the rotating portion 2 and the impeller 12 can be stably rotated, and vibration can be further reduced. Can do. Further, the axial length of the radial dynamic pressure bearing portion 68 can be shortened, and the sleeve 47 of the bearing portion 44 can be shortened. As a result, the bearing portion 44 can be manufactured with high accuracy. Preferably, the length of the sleeve 47 in the axial direction is not more than four times the outer diameter. Since the upper radial dynamic pressure bearing portion 681 overlaps the center of gravity of the motor 11 and the impeller 12 in the radial direction, the rotating portion 2 and the impeller 12 can be rotated more stably, and vibration can be further reduced. .

  While the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  In the above embodiment, the upper portion of the first radial dynamic pressure groove row 711 may be provided on the second inclined surface 471a of the sleeve 47 independently of other parts of the first radial dynamic pressure groove row 711. In the bearing portion 44, the dynamic pressure groove does not necessarily exist in the second inclined surface 471a. Even in this case, by providing the second inclined surface 471a, an area for supporting the shaft 41 can be secured, so that the bearing rigidity can be improved to some extent.

  The first and second radial dynamic pressure groove rows 711 and 712 may be provided on the outer peripheral surface 411 of the shaft 41. Thrust dynamic pressure groove rows 721 and 722 may be provided on the upper and lower surfaces of the thrust plate 42. In the gap 53 between the lower annular surface 423 of the thrust plate 42 and the upper surface 451 of the thrust cap 45, the lower radial dynamic pressure bearing portion 682 need not necessarily be configured. The circulation hole 445 may be formed by bringing the outer peripheral surface 473 of the sleeve 47 into contact with the inner peripheral surface 483 of the bearing housing 48 in which a plurality of grooves are formed. The sleeve upper gap 446 may be formed by bringing the upper surface 474 of the sleeve 47 into contact with the lower surface of the annular upper portion 481 in which a plurality of grooves are formed.

  In the above embodiment, by providing a portion having a reduced diameter on the outer peripheral surface 411 of the shaft 41 in the vicinity of the upper portion of the bearing portion 44, the seal portion 55a is configured between the portion and the inner peripheral surface 481a of the annular upper portion 481. May be. A cylindrical member other than the bearing housing 48 may be provided on the upper side of the sleeve 47 instead of the annular upper portion 481. In this case, a seal portion 55 a is formed between the inner peripheral surface of the cylindrical member and the outer peripheral surface 411 of the shaft 41. Further, an upper sleeve gap 446 is formed between the lower surface of the tubular member and the upper surface 474 of the sleeve 47. The upper part of the shaft 41 may be directly fixed to the impeller 12. The shaft 41 may be fixed to the impeller 12 via two or more members. As the seal portion, a Bisco seal that generates fluid dynamic pressure by a dynamic pressure groove provided in the seal gap may be used.

  A metal lump may be provided as a weight on the balance correcting portion 125 of the top surface portion 123 of the impeller 12. Moreover, a through-hole or a notch-shaped part may be provided as a balance correction part. The same applies to the balance correcting portion 124a of the side wall portion 124. A weight may be provided only on one of the top surface portion 123 and the lower end portion 124 a of the side wall portion 124. Moreover, the imbalance of the rotating part 2 may be eliminated by removing part of the top surface part 123 and the side wall part 124.

  In the above embodiment, the magnetic center of the stator 32 and the magnetic center of the rotor magnet 22 may coincide with each other in the axial direction when the motor 11 is stationary. Thereby, the vibration of the motor 11 can be further reduced.

  The motor 11 may be used as a motor for other fans such as a centrifugal fan. A fan using the motor 11 is most suitable for a device such as a server on which a hard disk is mounted. In the server, a fan is mounted at a position close to the hard disk. For this reason, hard disk read / write errors tend to occur when a fan with large vibration is installed. However, if a fan using the motor 11 is mounted on the server, hard disk read / write errors are unlikely to occur.

  The configurations in the above embodiment and each modification may be combined as appropriate as long as they do not contradict each other.

  The present invention can be used for a fan that generates an air flow.

DESCRIPTION OF SYMBOLS 1 Fan 2 Rotating part 3 Static part 11 Motor 12 Impeller 22 Rotor magnet 32 Stator 41 Shaft 42 Thrust plate 44 Bearing part 45 Thrust cap 46 Lubricating oil 47 Sleeve 48 Bearing housing 51 Radial gap 52 First lower thrust gap 53 Second lower thrust Clearance 55 Seal gap 68 Radial dynamic pressure bearing 122 122 Blade 411 (shaft) outer peripheral surface 422 Upper annular surface 422a Inclined surface 423 Lower annular surface 445 Circulation hole 446 Upper sleeve clearance 451 (Thrust cap) upper surface 471 (in sleeve) Peripheral surface 471a Second inclined surface 472 (Sleeve) lower surface 473 (Sleeve) outer surface 474 (Sleeve) upper surface 481 Annular upper portion 481a First inclined surface 681 Upper radial dynamic pressure bearing portion 682 Lower radial dynamic pressure shaft Part 691 first lower thrust dynamic pressure bearing portion 692 second lower thrust dynamic pressure bearing portion J1 central axis

Claims (10)

A motor,
An impeller having a plurality of blades and rotating around a central axis by the motor to generate an air flow;
With
The motor is
A stationary part;
A rotating part rotatably supported by the stationary part;
With
The stationary part is
A stator,
A bearing portion located inside the stator;
With
The bearing portion is
A sleeve which is a sintered body of metal;
A bearing housing covering the outer peripheral surface of the sleeve;
With
The rotating part is
A rotor magnet located radially outside the stator;
A shaft whose upper part is fixed to the impeller directly or via one or more members and inserted into the sleeve;
A thrust plate extending radially outward from the lower end of the shaft and facing the lower surface of the sleeve in the axial direction;
With
A radial dynamic pressure bearing portion configured to generate a fluid dynamic pressure of the lubricating oil that is directed downward in the axial direction is formed in a radial gap between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, and the lower surface of the sleeve and the A thrust dynamic pressure bearing portion configured to generate a fluid dynamic pressure of the lubricating oil directed radially inward in a thrust gap between the upper surface of the thrust plate and
A circulation hole extending in the axial direction from the upper surface of the sleeve to the lower surface is located between the outer peripheral surface of the sleeve and the bearing housing,
A fan in which a radial width of the radial gap is not less than 5 μm and not more than 20 μm.   The fan according to claim 1, wherein a radial width of the radial gap is larger than 5 μm.   3. The fan according to claim 1, wherein an outer edge portion of the upper surface of the thrust plate has an inclined surface that is inclined downward in a radially outward direction. The stationary portion further comprises a bearing bottom portion facing the lower surface of the thrust plate in the axial direction;
The other thrust dynamic pressure bearing portion that generates fluid dynamic pressure of the lubricating oil is configured in another thrust gap between the lower surface of the thrust plate and the upper surface of the bearing bottom portion. Fan according to any one.   The fan according to claim 4, wherein a sum of widths in the axial direction of the thrust gap and the other thrust gap is not less than 10 μm and not more than 40 μm. The bearing housing comprises an annular upper portion extending radially inward on the upper side of the sleeve;
6. The seal gap according to claim 1, wherein a seal gap is formed between the inner peripheral surface of the annular upper portion and the outer peripheral surface of the shaft so that the radial width gradually increases toward the upper side. fan. Adjacent to the lower side of the seal gap, the inner peripheral surface of the sleeve is provided with an inclined surface whose diameter gradually increases upward,
The fan according to claim 6, wherein the inclined surface follows the outer peripheral surface of the shaft when the shaft is inclined during rotation of the rotating portion.   The fan according to claim 7, wherein a part of the dynamic pressure groove of the radial dynamic pressure bearing portion is present on the inclined surface. The radial dynamic pressure bearing portion includes an upper radial dynamic pressure bearing portion located above the radial gap, and a lower radial dynamic pressure bearing portion located below the radial gap;
The fan according to any one of claims 1 to 8, wherein the upper radial dynamic pressure bearing portion overlaps a center of gravity of the motor and the impeller in a radial direction. A motor,
An impeller having a plurality of blades and rotating around a central axis by the motor to generate an air flow;
With
The motor is
A stationary part;
A rotating part rotatably supported by the stationary part;
With
The stationary part is
A stator,
A bearing portion located inside the stator;
With
The bearing portion is
A sleeve which is a sintered body of metal;
A bearing housing covering the outer peripheral surface of the sleeve;
With
The rotating part is
A rotor magnet located radially outside the stator;
A shaft whose upper part is fixed to the impeller directly or via one or more members and inserted into the sleeve;
A thrust plate extending radially outward from the lower end of the shaft and facing the lower surface of the sleeve in the axial direction;
With
A radial dynamic pressure bearing portion that generates fluid dynamic pressure of lubricating oil is formed in a radial gap between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, and the lower surface of the sleeve and the upper surface of the thrust plate A thrust dynamic pressure bearing portion that generates fluid dynamic pressure of the lubricating oil in the thrust gap between is configured,
A circulation hole extending in the axial direction from the upper surface of the sleeve to the lower surface is located between the outer peripheral surface of the sleeve and the bearing housing,
The fan in which the lubricating oil circulates to the radial gap through the radial gap, the gap on the upper surface of the sleeve, the circulation hole, and the thrust gap in this order when the rotating portion rotates.

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