US20180367007A1 - Electric motor and heat sink apparatus using the same - Google Patents
Electric motor and heat sink apparatus using the same Download PDFInfo
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- US20180367007A1 US20180367007A1 US15/902,121 US201815902121A US2018367007A1 US 20180367007 A1 US20180367007 A1 US 20180367007A1 US 201815902121 A US201815902121 A US 201815902121A US 2018367007 A1 US2018367007 A1 US 2018367007A1
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- rotating shaft
- tapered
- electric motor
- tapered part
- sleeve
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- 230000002093 peripheral effect Effects 0.000 claims abstract description 25
- 230000007423 decrease Effects 0.000 claims abstract description 14
- 230000020169 heat generation Effects 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 4
- 239000003921 oil Substances 0.000 description 28
- 238000011156 evaluation Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000009423 ventilation Methods 0.000 description 2
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K5/00—Casings; Enclosures; Supports
- H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
- H02K5/16—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields
- H02K5/167—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using sliding-contact or spherical cap bearings
- H02K5/1675—Means for supporting bearings, e.g. insulating supports or means for fitting bearings in the bearing-shields using sliding-contact or spherical cap bearings radially supporting the rotary shaft at only one end of the rotor
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C17/00—Sliding-contact bearings for exclusively rotary movement
- F16C17/02—Sliding-contact bearings for exclusively rotary movement for radial load only
- F16C17/026—Sliding-contact bearings for exclusively rotary movement for radial load only with helical grooves in the bearing surface to generate hydrodynamic pressure, e.g. herringbone grooves
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C3/00—Shafts; Axles; Cranks; Eccentrics
- F16C3/02—Shafts; Axles
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
- F16C33/02—Parts of sliding-contact bearings
- F16C33/04—Brasses; Bushes; Linings
- F16C33/06—Sliding surface mainly made of metal
- F16C33/10—Construction relative to lubrication
- F16C33/1025—Construction relative to lubrication with liquid, e.g. oil, as lubricant
- F16C33/106—Details of distribution or circulation inside the bearings, e.g. details of the bearing surfaces to affect flow or pressure of the liquid
- F16C33/107—Grooves for generating pressure
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
- H02K7/003—Couplings; Details of shafts
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
- H02K7/14—Structural association with mechanical loads, e.g. with hand-held machine tools or fans
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C2380/00—Electrical apparatus
- F16C2380/26—Dynamo-electric machines or combinations therewith, e.g. electro-motors and generators
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K2213/00—Specific aspects, not otherwise provided for and not covered by codes H02K2201/00 - H02K2211/00
- H02K2213/03—Machines characterised by numerical values, ranges, mathematical expressions or similar information
Definitions
- the present invention relates to an electric motor and a heat sink apparatus using the same.
- a heat sink apparatus is mounted for the purpose of cooling.
- the heat sink apparatus generates air flow by rotating a fan with an electric motor so as to remove heat from a heat generation member.
- PTL 1 discloses an electric motor (spindle motor) intended to achieve downsizing, impact resistance, low noise, and low power consumption.
- heat sink apparatuses have been used in various technical fields including the field of medical equipment, and the life time of the heat sink apparatuses is desired to be increased.
- Embodiments of the present disclosure disclose an electric motor and a heat sink apparatus using the same which can achieve longer life time in comparison with a conventional art.
- An electric motor includes: a frame including a frame housing having a cylindrical shape whose one end is open; a sleeve fitted in the frame housing; a stator attached to an outer peripheral part of the frame housing; and a rotor including a rotating shaft rotatably and pivotally supported by the sleeve, and a magnet that is disposed opposite to the stator, one end of the rotating shaft being fixed.
- the rotating shaft has a columnar shape.
- a tapered part having a tapered shape whose diameter decreases toward a side of a front end of the rotating shaft is formed in a center portion of the rotating shaft, the front end being a free end.
- a length of the tapered part is greater than a diameter of the rotating shaft. Oil is provided to a gap between the rotating shaft and the sleeve.
- FIG. 1 is a sectional view of an electric motor in a heat sink apparatus according to Embodiment 1 of the present disclosure
- FIGS. 2A to 2E illustrate external shapes of a rotating shaft of the electric motor according to Embodiment 1 of the present disclosure
- FIG. 3 is a sectional view of an electric motor in a heat sink apparatus according to Embodiment 2 of the present disclosure
- FIG. 4 illustrates an external shape of a sleeve of the electric motor according to Embodiment 2 of the present disclosure
- FIG. 5 is a sectional view of an electric motor in a heat sink apparatus according to Embodiment 3 of the present disclosure
- FIGS. 6A to 6F illustrate external shapes of a rotating shaft of the electric motor according to Embodiment 3 of the present disclosure
- FIG. 7 shows evaluations for each of ratios between tapered parts in the rotating shaft of the electric motor according to Embodiment 3 of the present disclosure
- FIG. 8 is a sectional view of an electric motor in a heat sink apparatus according to Embodiment 4 of the present disclosure.
- FIGS. 9A to 9F illustrate external shapes of a sleeve of the electric motor according to Embodiment 4 of the present disclosure.
- FIG. 10 shows evaluations for each of ratios between tapered parts in the sleeve of the electric motor according to Embodiment 4 of the present disclosure.
- FIG. 1 is a sectional view of an electric motor in a heat sink apparatus of Embodiment 1.
- Cylindrical frame housing 1 a having an open end is mounted in frame 1 .
- Substrate 4 and stator 3 of the electric motor are attached to an outer peripheral part of frame housing 1 a .
- Stator 3 is composed of insulation part 14 formed of an insulating material such as a synthetic resin, iron core 15 that is a stack of a plurality of thin plates, and coil 16 wound around iron core 15 .
- a predetermined number of openings of a predetermined size through which air flow passes are provided toward a predetermined direction.
- the bottom part of frame 1 on the side on which frame housing 1 a is not provided includes a plane area where a heat generation member such as a semiconductor device can be attached.
- thrustor 5 formed of a resin is fixed on the bottom surface.
- fixation ring 7 that presses down sleeve 6 is inserted.
- the end portion of fixation ring 7 on the insertion side is tilted inward at, for example, approximately 10 degrees so that it can be readily press-fitted into frame housing 1 a.
- Fan 8 is composed of a blade (not illustrated) and rotor main body 10 of the electric motor.
- Rear end part 9 b of rotating shaft 9 is inserted and fixed at a center of rotor main body 10 .
- magnet 11 and magnet yoke 12 are fixed to rotor main body 10 by bonding or the like so as to face annular stator 3 .
- the rotor of the electric motor is composed of rotating shaft 9 , rotor main body 10 , magnet 11 and magnet yoke 12 .
- recessed oil pool 10 a for reducing intrusion of external foreign matters and dusts into the bearing is formed at a portion around rotating shaft 9 .
- rib 10 b is formed at the outer periphery of oil pool 10 a and on the inner side of fixation ring 7 .
- Rotating shaft 9 is rotatably and pivotally supported by sleeve 6 .
- a dynamic-pressure generation groove (not illustrated) for facilitating the rotation of rotating shaft 9 is formed by ball rolling or the like on the inner peripheral surface of sleeve 6 .
- Oil 13 is provided as lubricating oil to the dynamic-pressure generation groove, and thus a radial bearing with a bearing gap of 2 to 12 ⁇ m on each side from rotating shaft 9 is formed.
- the dynamic-pressure generation groove may be formed on the outer peripheral surface of first straight part 9 e and/or second straight part 9 f of rotating shaft 9 (see FIGS. 2A to 2E ).
- Front end part 9 a (the free end opposite to rear end part 9 b ) of rotating shaft 9 is finished in the form of a spherical surface, and forms a thrust bearing in contact with thrustor 5 .
- ventilation groove 1 b that extends from the opening to the bottom surface of frame housing 1 a is formed at the inner wall of frame housing 1 a .
- oil pool 6 a that is a circumferential groove is formed on the front end side (the side close to the bottom surface of frame housing 1 a ) of the outer peripheral surface of sleeve 6 .
- a copper alloy such as C3604 and BC6C is used as the material of sleeve 6 in consideration of the cutting performance and/or the rolling performance
- a stainless steel such as SUS420J2 is used as the material of rotating shaft 9 in consideration of the wear resistance and/or the handleability.
- fluorinated synthetic oil is used as oil 13 in view of ensuring high temperature heat resistance, and an additive is added thereto in order to slightly improve the extreme pressure performance.
- rotating shaft 9 of the present embodiment is described with reference to FIGS. 2A to 2E . It is to be noted that the examples of rotating shaft 9 illustrated in FIGS. 2A to 2E are different in their taper angles.
- Rotating shaft 9 has a straight columnar shape whose diameter is constant. Front end part 9 a of the free end of rotating shaft 9 is finished in the form of a spherical surface. Knurling for attaching to rotor main body 10 is provided on rear end part 9 b of rotating shaft 9 .
- tapered part 9 d having a tapered shape whose diameter decreases toward front end part 9 a side is formed at a center portion (a portion where no dynamic pressure is generated) of rotating shaft 9 .
- base part 9 c (a portion other than front end part 9 a and rear end part 9 b ) of rotating shaft 9 is sectioned into tapered part 9 d, first straight part 9 e on front end part 9 a side, and second straight part 9 f on rear end part 9 b side.
- constriction part 9 g is formed at the connecting portion between tapered part 9 d and first straight part 9 e.
- constriction part 9 h is formed at the connecting portion between rear end part 9 b and second straight part 9 f.
- Dynamic-pressure generation grooves may be formed on the outer peripheral surfaces of first straight part 9 e and second straight part 9 f.
- Rotating shaft 9 has a total length of 9 mm and an outer diameter of 1.2 mm, for example.
- first straight part 9 e has a length of 1.4 mm
- tapered part 9 d including constriction part 9 g has a length of 2.2 mm
- second straight part 9 f has a length of 2.9 mm, for example.
- tapered part 9 d is formed at a center portion of rotating shaft 9 of the electric motor.
- the present inventors conducted durability tests with rotating shaft 9 provided with tapered part 9 d illustrated in FIGS. 2A to 2E and a rotating shaft provided with a step in which a recessed groove (having a depth of approximately 0.1 mm) is formed in place of tapered part 9 d.
- the tests were conducted under the same condition.
- the lifetime of the apparatus using the rotating shaft provided with a step was approximately 1,200 hours
- the lifetime of the apparatus using rotating shaft 9 provided with tapered part 9 d was approximately 2,200 hours.
- the lifetime of the apparatus using the rotating shaft provided with a step was approximately 2,000 hours, whereas no defect was caused in the apparatus using rotating shaft 9 provided with tapered part 9 d even after the apparatus was operated for 8,000 hours or more.
- the desirable taper angle of tapered part 9 d is 1 to 3 degrees ( FIGS. 2A to 2C ).
- the sizes of the parts of rotating shaft 9 are not limited to the above-mentioned sizes.
- the range of the length of first straight part 9 e is 1 to 3 mm
- the range of the length of tapered part 9 d including constriction part 9 g is 0.5 to 4 mm
- the range of the length of second straight part 9 f is 1.5 to 5 mm.
- rear end part 9 b of rotating shaft 9 may not be provided with knurling, and constriction part 9 h may not be formed.
- second straight part 9 f may have a length of 5 mm or greater.
- Tapered part 9 d is provided in rotating shaft 9 in Embodiment 1.
- tapered part 6 d (see FIG. 4 ) is provided in sleeve 6 .
- FIG. 3 is a sectional view of an electric motor in a heat sink apparatus of Embodiment 2.
- the heat sink apparatus illustrated in FIG. 3 is different from the heat sink apparatus illustrated in FIG. 1 in shapes of sleeve 6 and rotating shaft 9 .
- rotating shaft 9 is not provided with tapered part 9 d and constriction part 9 g, and the entirety of base part 9 c is a straight part.
- Sleeve 6 has a cylindrical shape.
- Oil pool 6 a that is a circumferential groove is formed on the outer peripheral surface of sleeve 6 on the from end side, and a step part 6 b that is a circumferential groove is formed on the outer peripheral surface of sleeve 6 on the rear end side.
- tapered part 6 d having a tapered shape whose diameter increases toward the front end side is formed at a center portion (a portion where no dynamic pressure is generated) of the inner peripheral surface of sleeve 6 .
- the inner peripheral surface of sleeve 6 is sectioned into tapered part 6 d, first straight part 6 e on the front end side, and second straight part 6 f on the rear end side.
- a clearance part 6 g is formed at the connecting portion between tapered part 6 d and first straight part 6 e.
- Dynamic-pressure generation groove 6 c is formed on the outer peripheral surfaces of first straight part 6 e and second straight part 6 f.
- the sleeve 6 has a total length of 6.0 mm, an outer diameter of 4.0 mm, and an inner diameter of 1.2 mm, for example.
- first straight part 6 e has a length of 1.8 mm
- tapered part 6 d including clearance part 6 g has a length of 2.0 mm
- second straight part 6 f has a length of 2.2 mm, for example.
- tapered part 6 d is formed at a center portion of sleeve 6 of the electric motor.
- the desirable taper angle a of tapered part 6 d is 1 to 10 degrees.
- the sizes of the parts of sleeve 6 are not limited to the above-mentioned sizes.
- the range of the length of first straight part 6 e is 1 to 3 mm
- the range of the length of tapered part 6 d including clearance part 6 g is 0.5 to 4 mm
- the range of the length of second straight part 6 f is 1.5 to 5 mm.
- FIG. 5 is a sectional view of an electric motor in a heat sink apparatus of Embodiment 3.
- the heat sink apparatus illustrated in FIG. 5 is different from the heat sink apparatus illustrated in FIG. 1 in shape of rotating shaft 9 .
- neither tapered part 9 d or constriction part 9 g is formed at a center portion of rotating shaft 9 , and first tapered part 9 d 1 and second tapered part 9 d 2 are formed in place of tapered part 9 d and constriction part 9 g (see FIGS. 6A to 6 F).
- rotating shaft 9 of the present embodiment is described with reference to FIGS. 6A to 6F . It is to be noted that the examples of rotating shaft 9 illustrated in FIGS. 6A to 6F are different in their ratios between the length of first tapered part 9 d 1 and the length of second tapered part 9 d 2 .
- first tapered part 9 d 1 having a tapered shape whose diameter decreases toward front end part 9 a side
- second tapered part 9 d 2 having a tapered shape whose diameter increases toward front end part 9 a side are formed.
- base part 9 c (a portion other than front end part 9 a and rear end part 9 b ) of rotating shaft 9 is sectioned into first tapered part 9 d 1 , second tapered part 9 d 2 , first straight part 9 e on front end part 9 a side, and second straight part 9 f on rear end part 9 b side.
- third straight part 9 d 3 may be formed at the connecting portion between first tapered part 9 d 1 and second tapered part 9 d 2 .
- a region including first tapered part 9 d 1 , second tapered part 9 d 2 and third straight part 9 d 3 serves as an oil pool.
- Rotating shaft 9 has a total length of 9 mm, and an outer diameter of 1.2 mm, for example.
- first straight part 9 e has a length of 1.4 mm
- the tapered region has a length of 2.2 mm
- second straight part 9 f has a length of 2.8 mm, for example.
- the present inventors studied the capillary force in rotating shafts 9 illustrated in FIGS. 6A to 6F .
- the resulting evaluations are shown in FIG. 7 .
- first tapered part 9 d 1 is longer than second tapered part 9 d 2 , that is, in the case where the ratio of the length of first tapered part 9 d 1 (“B” in FIGS. 6A to 6F and FIG. 7 ) to the length of second tapered part 9 d 2 (“A” in FIGS. 6A to 6F and FIG. 7 ) is greater than 1 ( FIGS. 6C, 6D, 6E, and 6F ), the bubbles in the tapered region can be moved to front end part 9 a side, and oil 13 in the tapered region can be moved to rotor main body 10 side of rotating shaft 9 by a capillary force (the evaluation “good” or “fair” in FIG. 7 ). In addition, it was confirmed that the desirable taper angle of first tapered part 9 d 1 is 1 to 10 degrees.
- first tapered part 9 d 1 is shorter than second tapered part 9 d 2 , that is, in the case where the ratio of the length of first tapered part 9 d 1 to the length of second tapered part 9 d 2 is smaller than 1 ( FIG. 6A ), the bubbles in the tapered region are moved to rotor main body 10 side and consequently oil 13 in the tapered region cannot be moved to rotor main body 10 side (the evaluation “poor” in FIG. 7 ).
- first tapered part 9 d 1 is approximately equal to the length of second tapered part 9 d 2 ( FIG. 6B )
- the bubbles in the tapered region do not move and consequently oil 13 in the tapered region cannot be sufficiently moved to rotor main body 10 side (the evaluation “poor” in FIG. 7 ).
- first tapered part 9 d 1 whose diameter decreases toward front end part 9 a side and second tapered part 9 d 2 whose diameter increases toward front end part 9 a side are formed at a center portion of rotating shaft 9 of the electric motor such that first tapered part 9 d 1 is longer than second tapered part 9 d 2 .
- oil 13 can be intimately applied to a portion of rotating shaft 9 on rotor main body 10 side (second straight part 9 f ) by a capillary force, and it is thus possible to achieve longer life time in comparison with a conventional art.
- the sizes of the parts of rotating shaft 9 are not limited to the above-mentioned sizes.
- the range of the length of first straight part 9 e is 1.5 to 10 mm
- the range of the length of tapered region is 0.5 to 4 mm
- the range of the length of second straight part 9 f is 1 to 8 mm.
- connecting portion between first tapered part 9 d 1 and second tapered part 9 d 2 may have shapes other than that of third straight part 9 d 3 such as a tapered part and a constriction part.
- first straight part 9 e may have a length of 5 mm or greater.
- First tapered part 9 d 1 and second tapered part 9 d 2 are provided in rotating shaft 9 in Embodiment 3.
- first tapered part 6 d 1 and second tapered part 6 d 2 are provided in sleeve 6 .
- FIG. 8 is a sectional view of an electric motor in a heat sink apparatus of Embodiment 4.
- the heat sink apparatus illustrated in FIG. 8 is different from the heat sink apparatus illustrated in FIG. 5 in shapes of sleeve 6 and rotating shaft 9 .
- rotating shaft 9 is provided with no tapered region, and the entirety of base part 9 c is a straight part.
- FIGS. 9A to 9F the shapes and the dimension of sleeve 6 of the present embodiment are described with reference to FIGS. 9A to 9F . It is to be noted that the examples of sleeve 6 illustrated in FIGS. 9A to 9F are different in their ratios between the length of first tapered part 6 d 1 and the length of second tapered part 6 d 2 .
- Sleeve 6 has a cylindrical shape. Oil pool 6 a that is a circumferential groove is formed on the outer peripheral surface of sleeve 6 on the front end side, and step part 6 b that is a circumferential groove is formed on the outer peripheral surface of sleeve 6 on the rear end side.
- first tapered part 6 d 1 having a tapered shape whose diameter increases toward the front end side and second tapered part 6 d 2 having a tapered shape whose diameter decreases toward the front end side are formed at a center portion (a portion where no dynamic pressure is generated) of the inner peripheral surface of sleeve 6 .
- the inner peripheral surface of sleeve 6 is sectioned into first tapered part 6 d 1 , second tapered part 6 d 2 , first straight part 6 e on the front end side, and second straight part 6 f on the rear end side.
- third straight part 6 d 3 may be formed at the connecting portion between first tapered part 6 d 1 and second tapered part 6 d 2 .
- a region including first tapered part 6 d 1 , second tapered part 6 d 2 and third straight part 6 d 3 serves as an oil pool.
- Dynamic-pressure generation groove 6 c is formed on the outer peripheral surfaces of first straight part 6 e and second straight part 6 f.
- Sleeve 6 has a total length of 6.0 mm, an outer diameter of 4.0 mm, and an inner diameter of 1.2 mm, for example.
- first straight part 6 e has a length of 1.8 mm
- the tapered region has a length of 2.0 mm
- second straight part 6 f has a length of 2.2 mm, for example.
- the present inventors studied the capillary force in sleeves 6 illustrated in FIGS. 9A to 9F .
- the resulting evaluations are shown in FIG. 10 .
- first tapered part 6 d 1 is longer than second tapered part 6 d 2 , that is, in the case where the ratio of the length of first tapered part 6 d 1 (“B” in FIGS. 9A to 9F and FIG. 10 ) to the length of second tapered part 6 d 2 (“A” in FIGS. 9A to 9F and FIG. 10 ) is greater than 1 ( FIGS. 9C, 9D, 9E and 9F ), the bubbles in the tapered region can be moved to the front end side, and oil 13 in the tapered region can be moved to rotor main body 10 side of rotating shaft 9 by a capillary force (the evaluation “good” or “fair” in FIG. 10 ).
- the desirable taper angle of first tapered part 6 d 1 is 1 to 10 degrees.
- first tapered part 6 d 1 is shorter than second tapered part 6 d 2 , that is, in the case where the ratio of the length of first tapered part 6 d 1 to the length of second tapered part 6 d 2 is smaller than 1 ( FIG. 9A ), the bubbles in the tapered region move to rotor main body 10 side and consequently oil 13 in the tapered region cannot be moved to rotor main body 10 side (the evaluation “poor” in FIG. 10 ).
- first tapered part 6 d 1 whose diameter increases toward the front end side of rotating shaft 9 and second tapered part 6 d 2 whose diameter decreases toward the front end side of rotating shaft 9 are formed at a center portion of sleeve 6 of the electric motor, and first tapered part 6 d 1 is longer than second tapered part 6 d 2 is .
- oil 13 can be intimately applied to a portion of rotating shaft 9 on rotor main body 10 side (second straight part 9 f ), and it is thus possible to achieve longer life time in comparison with a conventional art.
- the sizes of the parts of sleeve 6 are not limited to the above-mentioned sizes.
- the range of the length of first straight part 6 e is 1.5 to 10 mm
- the range of the length of tapered region is 0.5 to 4 mm
- the range of the length of second straight part 6 f is 1 to 8 mm.
- first tapered part 6 d 1 and second tapered part 6 d 2 may have shapes other than that of third straight part 6 d 3 such as a tapered part and a constriction part.
- the present invention is not limited to this, and the electric motor may also be used for other apparatuses such as an exhaust fan.
- An electric motor includes: a frame including a frame housing having a cylindrical shape whose one end is open; a sleeve fitted in the frame housing; a stator attached to an outer peripheral part of the frame housing; and a rotor including a rotating shaft rotatably and pivotally supported by the sleeve, and a magnet that is disposed opposite to the stator, one end of the rotating shaft being fixed.
- the rotating shaft has a columnar shape.
- a tapered part having a tapered shape whose diameter decreases toward a side of a front end of the rotating shaft is formed in a center portion of the rotating shaft, the front end being a free end.
- a length of the tapered part is greater than a diameter of the rotating shaft. Oil is provided to a gap between the rotating shaft and the sleeve.
- the tapered part has a taper angle of 1 to 3 degrees.
- the tapered part is sandwiched between two straight parts, each of the two straight parts having a constant diameter.
- a second tapered part having a tapered shape whose diameter decreases toward a side of a fixed end of the rotating shaft is formed in the center portion of the rotating shaft, the second tapered part being formed to extend from a first straight part that is one of the two straight parts on the free end side.
- the tapered part is formed to extend from a second straight part that is another of the two straight parts on the fixed end side.
- a length of the tapered part is greater than a length of the second tapered part.
- a taper angle of the tapered part is smaller than a taper angle of the second tapered part.
- An electric motor includes: a frame including a frame housing having a cylindrical shape whose one end is open; a sleeve fitted in the frame housing; a stator attached to an outer peripheral part of the frame housing; and a rotor including a rotating shaft rotatably and pivotally supported by the sleeve, and a magnet that is disposed opposite to the stator, one end of the rotating shaft being fixed.
- the rotating shaft has a columnar shape.
- a step part provided with a plurality of steps whose diameters decrease toward a side of a front end of the rotating shaft is formed in a center portion of the rotating shaft, the front end being a free end.
- a length of the step part is greater than a diameter of the rotating shaft. Oil is provided to a gap between the rotating shaft and the sleeve.
- the step part is sandwiched between two straight parts, each of the two straight parts having a constant diameter.
- a dynamic-pressure generation groove that holds the oil is formed in at least one of an outer peripheral surface of the rotating shaft and an inner peripheral surface of the sleeve.
- a heat sink apparatus is a cooling fan motor including the electric motor above.
- a heat generation member is attachable to the frame of the electric motor.
- a second tapered part having a tapered shape whose diameter increases toward the free end side is formed in the center portion of the rotating shaft.
- a length of the tapered part is greater than a length of the second tapered part.
- a taper angle of the tapered part is 1 to 10 degrees.
- a sum of the length of the tapered part and the length of the second tapered part is greater than a diameter of the rotating shaft.
- a heat sink apparatus is a cooling fan motor including the electric motor above.
- a heat generation member is attachable to the frame of the electric motor.
- the present invention is suitable for an electric motor and a heat sink apparatus using the same.
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Abstract
Description
- Japanese Patent Applications No. 2017-118866 filed on Jun. 16, 2017, No. 2017-150661 filed on Aug. 3, 2017 and No. 2017-234241 filed on Dec. 6, 2017, including description, claims, drawings, and abstract the entire disclosure is incorporated herein by reference in its entirety.
- The present invention relates to an electric motor and a heat sink apparatus using the same.
- In an electronic apparatus, a heat sink apparatus is mounted for the purpose of cooling. The heat sink apparatus generates air flow by rotating a fan with an electric motor so as to remove heat from a heat generation member.
-
PTL 1 discloses an electric motor (spindle motor) intended to achieve downsizing, impact resistance, low noise, and low power consumption. -
PTL 1 - Japanese Patent Application Laid-Open No. H6-269142
- In recent years, heat sink apparatuses have been used in various technical fields including the field of medical equipment, and the life time of the heat sink apparatuses is desired to be increased.
- Embodiments of the present disclosure disclose an electric motor and a heat sink apparatus using the same which can achieve longer life time in comparison with a conventional art.
- An electric motor according to a mode of the present disclosure includes: a frame including a frame housing having a cylindrical shape whose one end is open; a sleeve fitted in the frame housing; a stator attached to an outer peripheral part of the frame housing; and a rotor including a rotating shaft rotatably and pivotally supported by the sleeve, and a magnet that is disposed opposite to the stator, one end of the rotating shaft being fixed. The rotating shaft has a columnar shape. A tapered part having a tapered shape whose diameter decreases toward a side of a front end of the rotating shaft is formed in a center portion of the rotating shaft, the front end being a free end. A length of the tapered part is greater than a diameter of the rotating shaft. Oil is provided to a gap between the rotating shaft and the sleeve.
- According to the present disclosure, it is possible to achieve longer life time in comparison with a conventional art.
-
FIG. 1 is a sectional view of an electric motor in a heat sink apparatus according toEmbodiment 1 of the present disclosure; -
FIGS. 2A to 2E illustrate external shapes of a rotating shaft of the electric motor according toEmbodiment 1 of the present disclosure; -
FIG. 3 is a sectional view of an electric motor in a heat sink apparatus according to Embodiment 2 of the present disclosure; -
FIG. 4 illustrates an external shape of a sleeve of the electric motor according to Embodiment 2 of the present disclosure; -
FIG. 5 is a sectional view of an electric motor in a heat sink apparatus according toEmbodiment 3 of the present disclosure; -
FIGS. 6A to 6F illustrate external shapes of a rotating shaft of the electric motor according toEmbodiment 3 of the present disclosure; -
FIG. 7 shows evaluations for each of ratios between tapered parts in the rotating shaft of the electric motor according toEmbodiment 3 of the present disclosure; -
FIG. 8 is a sectional view of an electric motor in a heat sink apparatus according toEmbodiment 4 of the present disclosure; -
FIGS. 9A to 9F illustrate external shapes of a sleeve of the electric motor according toEmbodiment 4 of the present disclosure; and -
FIG. 10 shows evaluations for each of ratios between tapered parts in the sleeve of the electric motor according toEmbodiment 4 of the present disclosure. - Embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be noted that details may be omitted in the descriptions as necessary. For example, details of well-known matters, overlapping descriptions between substantially identical configurations and the like may be omitted to avoid unnecessary redundancy in the descriptions, and to facilitate understanding of a person skilled in the art.
- The advantages and features provided by the embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention.
-
FIG. 1 is a sectional view of an electric motor in a heat sink apparatus ofEmbodiment 1.Cylindrical frame housing 1 a having an open end is mounted inframe 1.Substrate 4 andstator 3 of the electric motor are attached to an outer peripheral part offrame housing 1 a.Stator 3 is composed ofinsulation part 14 formed of an insulating material such as a synthetic resin,iron core 15 that is a stack of a plurality of thin plates, andcoil 16 wound aroundiron core 15. - In the side wall of
frame 1, a predetermined number of openings of a predetermined size through which air flow passes (not illustrated) are provided toward a predetermined direction. In addition, the bottom part offrame 1 on the side on whichframe housing 1 a is not provided includes a plane area where a heat generation member such as a semiconductor device can be attached. In addition,thrustor 5 formed of a resin is fixed on the bottom surface. - In
frame housing 1 a,sleeve 6 is fitted, andfixation ring 7 that presses downsleeve 6 is inserted. The end portion offixation ring 7 on the insertion side is tilted inward at, for example, approximately 10 degrees so that it can be readily press-fitted intoframe housing 1 a. -
Fan 8 is composed of a blade (not illustrated) and rotormain body 10 of the electric motor.Rear end part 9 b of rotatingshaft 9 is inserted and fixed at a center of rotormain body 10. In addition,magnet 11 andmagnet yoke 12 are fixed to rotormain body 10 by bonding or the like so as to faceannular stator 3. The rotor of the electric motor is composed of rotatingshaft 9, rotormain body 10,magnet 11 andmagnet yoke 12. - Further, in rotor
main body 10, recessedoil pool 10 a for reducing intrusion of external foreign matters and dusts into the bearing is formed at a portion around rotatingshaft 9. In addition, in rotormain body 10,rib 10 b is formed at the outer periphery ofoil pool 10 a and on the inner side offixation ring 7. - Rotating
shaft 9 is rotatably and pivotally supported bysleeve 6. A dynamic-pressure generation groove (not illustrated) for facilitating the rotation of rotatingshaft 9 is formed by ball rolling or the like on the inner peripheral surface ofsleeve 6.Oil 13 is provided as lubricating oil to the dynamic-pressure generation groove, and thus a radial bearing with a bearing gap of 2 to 12 μm on each side from rotatingshaft 9 is formed. - It is to be noted that the dynamic-pressure generation groove may be formed on the outer peripheral surface of first
straight part 9 e and/or secondstraight part 9 f of rotating shaft 9 (seeFIGS. 2A to 2E ). -
Front end part 9 a (the free end opposite torear end part 9 b) of rotatingshaft 9 is finished in the form of a spherical surface, and forms a thrust bearing in contact withthrustor 5. - Between frame housing 1 a and
sleeve 6,ventilation groove 1 b that extends from the opening to the bottom surface offrame housing 1 a is formed at the inner wall offrame housing 1 a. In addition,oil pool 6 a that is a circumferential groove is formed on the front end side (the side close to the bottom surface offrame housing 1 a) of the outer peripheral surface ofsleeve 6. - With the electric motor having the above-mentioned configuration, a surplus of
oil 13 in the bearing can be stored inoil pool 6 a on the outer periphery of the sleeve throughventilation groove 1 b, and it is thus possible to increase the acceptable variation and the supply amount of oil. - It is to be noted that a copper alloy such as C3604 and BC6C is used as the material of
sleeve 6 in consideration of the cutting performance and/or the rolling performance, and a stainless steel such as SUS420J2 is used as the material ofrotating shaft 9 in consideration of the wear resistance and/or the handleability. In addition, fluorinated synthetic oil is used asoil 13 in view of ensuring high temperature heat resistance, and an additive is added thereto in order to slightly improve the extreme pressure performance. - In the heat sink apparatus of the present embodiment, when the rotor of the electric motor is rotated, fan 8 (blade) is also rotated, and air is sucked along the axis direction of
rotating shaft 9 of the electric motor. The sucked air is exhausted from the opening provided in the side wall offrame 1. At this time, the air flow removes the heat offrame 1 transferred from the heat generation member. In this manner, the heat generation member is cooled. - Now the shape and the dimension of
rotating shaft 9 of the present embodiment are described with reference toFIGS. 2A to 2E . It is to be noted that the examples ofrotating shaft 9 illustrated inFIGS. 2A to 2E are different in their taper angles. -
Rotating shaft 9 has a straight columnar shape whose diameter is constant.Front end part 9 a of the free end ofrotating shaft 9 is finished in the form of a spherical surface. Knurling for attaching to rotormain body 10 is provided onrear end part 9 b ofrotating shaft 9. - In addition,
tapered part 9 d having a tapered shape whose diameter decreases towardfront end part 9 a side is formed at a center portion (a portion where no dynamic pressure is generated) ofrotating shaft 9. With this configuration,base part 9 c (a portion other thanfront end part 9 a andrear end part 9 b) ofrotating shaft 9 is sectioned into taperedpart 9 d, firststraight part 9 e onfront end part 9 a side, and secondstraight part 9 f onrear end part 9 b side. It is to be noted thatconstriction part 9 g is formed at the connecting portion betweentapered part 9 d and firststraight part 9 e. In addition,constriction part 9 h is formed at the connecting portion betweenrear end part 9 b and secondstraight part 9 f. - Dynamic-pressure generation grooves may be formed on the outer peripheral surfaces of first
straight part 9 e and secondstraight part 9 f. -
Rotating shaft 9 has a total length of 9 mm and an outer diameter of 1.2 mm, for example. In addition, firststraight part 9 e has a length of 1.4 mm,tapered part 9 d includingconstriction part 9 g has a length of 2.2 mm, and secondstraight part 9 f has a length of 2.9 mm, for example. - As described above, in the present embodiment,
tapered part 9 d is formed at a center portion ofrotating shaft 9 of the electric motor. With this configuration, by a capillary force,oil 13 can be intimately applied to a part (second straight part 90 ofrotating shaft 9 on rotormain body 10 side, and it is thus possible to achieve longer life time in comparison with a conventional art. - To prove the above-mentioned effects, the present inventors conducted durability tests with
rotating shaft 9 provided withtapered part 9 d illustrated inFIGS. 2A to 2E and a rotating shaft provided with a step in which a recessed groove (having a depth of approximately 0.1 mm) is formed in place oftapered part 9 d. - The tests were conducted under the same condition. In the condition where the outside air temperature was 120° C., the lifetime of the apparatus using the rotating shaft provided with a step was approximately 1,200 hours, whereas the lifetime of the apparatus using
rotating shaft 9 provided withtapered part 9 d was approximately 2,200 hours. In addition, in the condition where the outside air temperature was 100° C., the lifetime of the apparatus using the rotating shaft provided with a step was approximately 2,000 hours, whereas no defect was caused in the apparatus usingrotating shaft 9 provided withtapered part 9 d even after the apparatus was operated for 8,000 hours or more. - In addition, as a result of a study on the capillary force, it was confirmed that the desirable taper angle of
tapered part 9 d is 1 to 3 degrees (FIGS. 2A to 2C ). - In addition, it was confirmed that a similar effect is achieved also in the case where a step part provided with multi steps whose diameters decrease toward
front end part 9 a side is formed in place oftapered part 9 d at a center portion (a portion where no dynamic pressure is generated) ofrotating shaft 9. - It is to be noted that, in the present embodiment, the sizes of the parts of
rotating shaft 9 are not limited to the above-mentioned sizes. Inrotating shaft 9, the range of the length of firststraight part 9 e is 1 to 3 mm, the range of the length oftapered part 9 d includingconstriction part 9 g is 0.5 to 4 mm, and the range of the length of secondstraight part 9 f is 1.5 to 5 mm. - In addition,
rear end part 9 b ofrotating shaft 9 may not be provided with knurling, andconstriction part 9 h may not be formed. In this case, secondstraight part 9 f may have a length of 5 mm or greater. -
Tapered part 9 d is provided inrotating shaft 9 inEmbodiment 1. In Embodiment 2,tapered part 6 d (seeFIG. 4 ) is provided insleeve 6. -
FIG. 3 is a sectional view of an electric motor in a heat sink apparatus of Embodiment 2. The heat sink apparatus illustrated inFIG. 3 is different from the heat sink apparatus illustrated inFIG. 1 in shapes ofsleeve 6 androtating shaft 9. - In the present embodiment,
rotating shaft 9 is not provided withtapered part 9 d andconstriction part 9 g, and the entirety ofbase part 9 c is a straight part. - Now the shape and the dimension of
sleeve 6 of the present embodiment are described with reference toFIG. 4 .Sleeve 6 has a cylindrical shape.Oil pool 6 a that is a circumferential groove is formed on the outer peripheral surface ofsleeve 6 on the from end side, and astep part 6 b that is a circumferential groove is formed on the outer peripheral surface ofsleeve 6 on the rear end side. - In addition,
tapered part 6 d having a tapered shape whose diameter increases toward the front end side is formed at a center portion (a portion where no dynamic pressure is generated) of the inner peripheral surface ofsleeve 6. With this configuration, the inner peripheral surface ofsleeve 6 is sectioned into taperedpart 6 d, firststraight part 6 e on the front end side, and secondstraight part 6 f on the rear end side. It is to be noted that aclearance part 6 g is formed at the connecting portion betweentapered part 6 d and firststraight part 6 e. - Dynamic-
pressure generation groove 6 c is formed on the outer peripheral surfaces of firststraight part 6 e and secondstraight part 6 f. - The
sleeve 6 has a total length of 6.0 mm, an outer diameter of 4.0 mm, and an inner diameter of 1.2 mm, for example. In addition, firststraight part 6 e has a length of 1.8 mm,tapered part 6 d includingclearance part 6 g has a length of 2.0 mm, and secondstraight part 6 f has a length of 2.2 mm, for example. - As described above, in the present embodiment,
tapered part 6 d is formed at a center portion ofsleeve 6 of the electric motor. With this configuration,oil 13 can be intimately applied to a portion ofrotating shaft 9 on rotormain body 10 side by a capillary force, and it is thus possible to achieve longer life time in comparison with a conventional art. - In addition, as a result of a study on the capillary force, it was confirmed that the desirable taper angle a of
tapered part 6 d is 1 to 10 degrees. - In addition, it was confirmed that a similar effect is achieved also in the case where a step part provided with multi steps whose diameters increase toward the front end side is formed at a center portion (a portion where no dynamic pressure is generated) of
sleeve 6 in place oftapered part 6 d. - It is to be noted that, in the present embodiment, the sizes of the parts of
sleeve 6 are not limited to the above-mentioned sizes. Insleeve 6, the range of the length of firststraight part 6 e is 1 to 3 mm, the range of the length oftapered part 6 d includingclearance part 6 g is 0.5 to 4 mm, and the range of the length of secondstraight part 6 f is 1.5 to 5 mm. -
FIG. 5 is a sectional view of an electric motor in a heat sink apparatus ofEmbodiment 3. The heat sink apparatus illustrated inFIG. 5 is different from the heat sink apparatus illustrated inFIG. 1 in shape ofrotating shaft 9. - In the present embodiment, neither
tapered part 9 d orconstriction part 9 g is formed at a center portion ofrotating shaft 9, and firsttapered part 9d 1 and secondtapered part 9 d 2 are formed in place oftapered part 9 d andconstriction part 9 g (seeFIGS. 6A to 6F). - Now the shape and the dimension of
rotating shaft 9 of the present embodiment are described with reference toFIGS. 6A to 6F . It is to be noted that the examples ofrotating shaft 9 illustrated inFIGS. 6A to 6F are different in their ratios between the length of firsttapered part 9d 1 and the length of secondtapered part 9 d 2. - At a center portion (a portion where no dynamic pressure is generated) of
rotating shaft 9, firsttapered part 9d 1 having a tapered shape whose diameter decreases towardfront end part 9 a side and secondtapered part 9 d 2 having a tapered shape whose diameter increases towardfront end part 9 a side are formed. With this configuration,base part 9 c (a portion other thanfront end part 9 a andrear end part 9 b) ofrotating shaft 9 is sectioned into firsttapered part 9d 1, secondtapered part 9 d 2, firststraight part 9 e onfront end part 9 a side, and secondstraight part 9 f onrear end part 9 b side. It is to be noted that, in view of ease of working and the like, thirdstraight part 9d 3 may be formed at the connecting portion between firsttapered part 9d 1 and secondtapered part 9 d 2. - A region including first
tapered part 9d 1, secondtapered part 9 d 2 and thirdstraight part 9 d 3 (hereinafter referred to as “tapered region”) serves as an oil pool. -
Rotating shaft 9 has a total length of 9 mm, and an outer diameter of 1.2 mm, for example. In addition, firststraight part 9 e has a length of 1.4 mm, the tapered region has a length of 2.2 mm, and secondstraight part 9 f has a length of 2.8 mm, for example. - The present inventors studied the capillary force in rotating
shafts 9 illustrated inFIGS. 6A to 6F . The resulting evaluations are shown inFIG. 7 . - It was confirmed that in the case where first
tapered part 9d 1 is longer than secondtapered part 9 d 2, that is, in the case where the ratio of the length of firsttapered part 9 d 1 (“B” inFIGS. 6A to 6F andFIG. 7 ) to the length of secondtapered part 9 d 2 (“A” inFIGS. 6A to 6F andFIG. 7 ) is greater than 1 (FIGS. 6C, 6D, 6E, and 6F ), the bubbles in the tapered region can be moved tofront end part 9 a side, andoil 13 in the tapered region can be moved to rotormain body 10 side ofrotating shaft 9 by a capillary force (the evaluation “good” or “fair” inFIG. 7 ). In addition, it was confirmed that the desirable taper angle of firsttapered part 9d 1 is 1 to 10 degrees. - Also, it was confirmed that in the case where first
tapered part 9d 1 is shorter than secondtapered part 9 d 2, that is, in the case where the ratio of the length of firsttapered part 9d 1 to the length of secondtapered part 9 d 2 is smaller than 1 (FIG. 6A ), the bubbles in the tapered region are moved to rotormain body 10 side and consequentlyoil 13 in the tapered region cannot be moved to rotormain body 10 side (the evaluation “poor” inFIG. 7 ). - Also, it was confirmed that in the case where the length of first
tapered part 9d 1 is approximately equal to the length of secondtapered part 9 d 2 (FIG. 6B ), the bubbles in the tapered region do not move and consequentlyoil 13 in the tapered region cannot be sufficiently moved to rotormain body 10 side (the evaluation “poor” inFIG. 7 ). - As described above, in the present embodiment, first
tapered part 9d 1 whose diameter decreases towardfront end part 9 a side and secondtapered part 9 d 2 whose diameter increases towardfront end part 9 a side are formed at a center portion ofrotating shaft 9 of the electric motor such that firsttapered part 9d 1 is longer than secondtapered part 9 d 2. With this configuration,oil 13 can be intimately applied to a portion ofrotating shaft 9 on rotormain body 10 side (secondstraight part 9 f) by a capillary force, and it is thus possible to achieve longer life time in comparison with a conventional art. - It is to be noted that, in the present embodiment, the sizes of the parts of
rotating shaft 9 are not limited to the above-mentioned sizes. Inrotating shaft 9, the range of the length of firststraight part 9 e is 1.5 to 10 mm, the range of the length of tapered region is 0.5 to 4 mm, and the range of the length of secondstraight part 9 f is 1 to 8 mm. - In addition, the connecting portion between first
tapered part 9d 1 and secondtapered part 9 d 2 may have shapes other than that of thirdstraight part 9d 3 such as a tapered part and a constriction part. - In addition,
rear end part 9 b ofrotating shaft 9 may not be provided with knurling, andconstriction part 9 h may not be formed. In this case, firststraight part 9 e may have a length of 5 mm or greater. - First
tapered part 9d 1 and secondtapered part 9 d 2 are provided inrotating shaft 9 inEmbodiment 3. InEmbodiment 4, firsttapered part 6d 1 and secondtapered part 6 d 2 (seeFIGS. 9A to 9F ) are provided insleeve 6. -
FIG. 8 is a sectional view of an electric motor in a heat sink apparatus ofEmbodiment 4. The heat sink apparatus illustrated inFIG. 8 is different from the heat sink apparatus illustrated inFIG. 5 in shapes ofsleeve 6 androtating shaft 9. - In the present embodiment,
rotating shaft 9 is provided with no tapered region, and the entirety ofbase part 9 c is a straight part. - Now the shape and the dimension of
sleeve 6 of the present embodiment are described with reference toFIGS. 9A to 9F . It is to be noted that the examples ofsleeve 6 illustrated inFIGS. 9A to 9F are different in their ratios between the length of firsttapered part 6d 1 and the length of secondtapered part 6 d 2. -
Sleeve 6 has a cylindrical shape.Oil pool 6 a that is a circumferential groove is formed on the outer peripheral surface ofsleeve 6 on the front end side, and steppart 6 b that is a circumferential groove is formed on the outer peripheral surface ofsleeve 6 on the rear end side. - In addition, first
tapered part 6d 1 having a tapered shape whose diameter increases toward the front end side and secondtapered part 6 d 2 having a tapered shape whose diameter decreases toward the front end side are formed at a center portion (a portion where no dynamic pressure is generated) of the inner peripheral surface ofsleeve 6. With this configuration, the inner peripheral surface ofsleeve 6 is sectioned into firsttapered part 6d 1, secondtapered part 6 d 2, firststraight part 6 e on the front end side, and secondstraight part 6 f on the rear end side. It is to be noted that, in view of ease of working and the like, thirdstraight part 6d 3 may be formed at the connecting portion between firsttapered part 6d 1 and secondtapered part 6 d 2. - A region including first
tapered part 6d 1, secondtapered part 6 d 2 and thirdstraight part 6 d 3 (hereinafter referred to as “tapered region”) serves as an oil pool. - Dynamic-
pressure generation groove 6 c is formed on the outer peripheral surfaces of firststraight part 6 e and secondstraight part 6 f. -
Sleeve 6 has a total length of 6.0 mm, an outer diameter of 4.0 mm, and an inner diameter of 1.2 mm, for example. In addition, firststraight part 6 e has a length of 1.8 mm, the tapered region has a length of 2.0 mm, and secondstraight part 6 f has a length of 2.2 mm, for example. - The present inventors studied the capillary force in
sleeves 6 illustrated inFIGS. 9A to 9F . The resulting evaluations are shown inFIG. 10 . - It was confirmed that in the case where first
tapered part 6d 1 is longer than secondtapered part 6 d 2, that is, in the case where the ratio of the length of firsttapered part 6 d 1 (“B” inFIGS. 9A to 9F andFIG. 10 ) to the length of secondtapered part 6 d 2 (“A” inFIGS. 9A to 9F andFIG. 10 ) is greater than 1 (FIGS. 9C, 9D, 9E and 9F ), the bubbles in the tapered region can be moved to the front end side, andoil 13 in the tapered region can be moved to rotormain body 10 side ofrotating shaft 9 by a capillary force (the evaluation “good” or “fair” inFIG. 10 ). In addition, it was confirmed that the desirable taper angle of firsttapered part 6d 1 is 1 to 10 degrees. - In addition, it was confirmed that in the case where first
tapered part 6d 1 is shorter than secondtapered part 6 d 2, that is, in the case where the ratio of the length of firsttapered part 6d 1 to the length of secondtapered part 6 d 2 is smaller than 1 (FIG. 9A ), the bubbles in the tapered region move to rotormain body 10 side and consequentlyoil 13 in the tapered region cannot be moved to rotormain body 10 side (the evaluation “poor” inFIG. 10 ). - In addition, it was confirmed that in the case where the length of first
tapered part 6d 1 is approximately equal to the length of secondtapered part 6 d 2 (FIG. 9B ), the bubbles in the tapered region do not move and consequentlyoil 13 in the tapered region cannot be sufficiently moved to rotormain body 10 side (the evaluation “poor” inFIG. 10 ). - As described above, in the present embodiment, first
tapered part 6d 1 whose diameter increases toward the front end side ofrotating shaft 9 and secondtapered part 6 d 2 whose diameter decreases toward the front end side ofrotating shaft 9 are formed at a center portion ofsleeve 6 of the electric motor, and firsttapered part 6d 1 is longer than secondtapered part 6 d 2 is. With this configuration, by a capillary force,oil 13 can be intimately applied to a portion ofrotating shaft 9 on rotormain body 10 side (secondstraight part 9 f), and it is thus possible to achieve longer life time in comparison with a conventional art. - It is to be noted that, in the present embodiment, the sizes of the parts of
sleeve 6 are not limited to the above-mentioned sizes. Insleeve 6, the range of the length of firststraight part 6 e is 1.5 to 10 mm, the range of the length of tapered region is 0.5 to 4 mm, and the range of the length of secondstraight part 6 f is 1 to 8 mm. - In addition, the connecting portion between first
tapered part 6d 1 and secondtapered part 6 d 2 may have shapes other than that of thirdstraight part 6d 3 such as a tapered part and a constriction part. - The present invention is not limited to the drawings and the embodiments described above. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors in so far as they are within the scope of the appended claims or the equivalents thereof.
- While the electric motor is used for a heat sink apparatus in the embodiments, the present invention is not limited to this, and the electric motor may also be used for other apparatuses such as an exhaust fan.
- An electric motor according to a mode of the present disclosure includes: a frame including a frame housing having a cylindrical shape whose one end is open; a sleeve fitted in the frame housing; a stator attached to an outer peripheral part of the frame housing; and a rotor including a rotating shaft rotatably and pivotally supported by the sleeve, and a magnet that is disposed opposite to the stator, one end of the rotating shaft being fixed. The rotating shaft has a columnar shape. A tapered part having a tapered shape whose diameter decreases toward a side of a front end of the rotating shaft is formed in a center portion of the rotating shaft, the front end being a free end. A length of the tapered part is greater than a diameter of the rotating shaft. Oil is provided to a gap between the rotating shaft and the sleeve.
- In the electric motor above, the tapered part has a taper angle of 1 to 3 degrees.
- In the electric motor above, the tapered part is sandwiched between two straight parts, each of the two straight parts having a constant diameter.
- In the electric motor above, a second tapered part having a tapered shape whose diameter decreases toward a side of a fixed end of the rotating shaft is formed in the center portion of the rotating shaft, the second tapered part being formed to extend from a first straight part that is one of the two straight parts on the free end side. The tapered part is formed to extend from a second straight part that is another of the two straight parts on the fixed end side. A length of the tapered part is greater than a length of the second tapered part. A taper angle of the tapered part is smaller than a taper angle of the second tapered part.
- An electric motor according to a mode of the present disclosure includes: a frame including a frame housing having a cylindrical shape whose one end is open; a sleeve fitted in the frame housing; a stator attached to an outer peripheral part of the frame housing; and a rotor including a rotating shaft rotatably and pivotally supported by the sleeve, and a magnet that is disposed opposite to the stator, one end of the rotating shaft being fixed. The rotating shaft has a columnar shape. A step part provided with a plurality of steps whose diameters decrease toward a side of a front end of the rotating shaft is formed in a center portion of the rotating shaft, the front end being a free end. A length of the step part is greater than a diameter of the rotating shaft. Oil is provided to a gap between the rotating shaft and the sleeve.
- In the electric motor above, the step part is sandwiched between two straight parts, each of the two straight parts having a constant diameter.
- In the electric motor above, a dynamic-pressure generation groove that holds the oil is formed in at least one of an outer peripheral surface of the rotating shaft and an inner peripheral surface of the sleeve.
- A heat sink apparatus according to a mode of the present disclosure is a cooling fan motor including the electric motor above. A heat generation member is attachable to the frame of the electric motor.
- In the electric motor above, a second tapered part having a tapered shape whose diameter increases toward the free end side is formed in the center portion of the rotating shaft. A length of the tapered part is greater than a length of the second tapered part.
- In the electric motor above, a taper angle of the tapered part is 1 to 10 degrees.
- In the electric motor above, a sum of the length of the tapered part and the length of the second tapered part is greater than a diameter of the rotating shaft.
- A heat sink apparatus according to a mode of the present disclosure is a cooling fan motor including the electric motor above. A heat generation member is attachable to the frame of the electric motor.
- The present invention is suitable for an electric motor and a heat sink apparatus using the same.
- 1 Frame
- 1 a Frame housing
- 3 Stator
- 5 Thrustor
- 6 Sleeve
- 6 c Dynamic-pressure generation groove
- 6 d Tapered part
- 6
d 1 First tapered part - 6 d 2 Second tapered part
- 6
d 3 Third straight part - 6 e First straight part
- 6 f Second straight part
- 7 Fixation ring
- 8 Fan
- 9 Rotating shaft
- 9 a Front end part
- 9 b Rear end part
- 9 c Base part
- 9 d Tapered part
- 9
d 1 First tapered part - 9 d 2 Second tapered part
- 9
d 3 Third straight part - 9 e First straight part
- 9 f Second straight part
- 9 g Constriction part
- 10 Rotor main body
- 11 Magnet
- 12 Magnet yoke
- 13 Oil
Claims (8)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US16/158,927 US10250099B2 (en) | 2017-06-16 | 2018-10-12 | Electric motor and heat sink apparatus using the same |
Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2017118866A JP6283923B1 (en) | 2017-06-16 | 2017-06-16 | Electric motor and heat sink device using the same |
JP2017-118866 | 2017-06-16 | ||
JP2017-150661 | 2017-08-03 | ||
JP2017150661A JP6283924B1 (en) | 2017-08-03 | 2017-08-03 | Electric motor and heat sink device using the same |
JP2017-234241 | 2017-12-06 | ||
JP2017234241A JP6390990B1 (en) | 2017-12-06 | 2017-12-06 | Electric motor and heat sink device using the same |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US16/158,927 Continuation US10250099B2 (en) | 2017-06-16 | 2018-10-12 | Electric motor and heat sink apparatus using the same |
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Publication Number | Publication Date |
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US10158269B1 US10158269B1 (en) | 2018-12-18 |
US20180367007A1 true US20180367007A1 (en) | 2018-12-20 |
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US16/158,927 Active US10250099B2 (en) | 2017-06-16 | 2018-10-12 | Electric motor and heat sink apparatus using the same |
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JP6283923B1 (en) | 2017-06-16 | 2018-02-28 | パナソニックIpマネジメント株式会社 | Electric motor and heat sink device using the same |
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- 2018-10-12 US US16/158,927 patent/US10250099B2/en active Active
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Also Published As
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US20190052145A1 (en) | 2019-02-14 |
US10158269B1 (en) | 2018-12-18 |
US10250099B2 (en) | 2019-04-02 |
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