CN220850360U - Dynamic pressure bearing, dynamic pressure bearing device, and motor - Google Patents

Dynamic pressure bearing, dynamic pressure bearing device, and motor Download PDF

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Publication number
CN220850360U
CN220850360U CN202322504096.2U CN202322504096U CN220850360U CN 220850360 U CN220850360 U CN 220850360U CN 202322504096 U CN202322504096 U CN 202322504096U CN 220850360 U CN220850360 U CN 220850360U
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China
Prior art keywords
dynamic pressure
sintered body
bearing
pressure bearing
groove
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CN202322504096.2U
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Chinese (zh)
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小松原慎治
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NTN Corp
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NTN Corp
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • 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
    • 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
    • F16C17/04—Sliding-contact bearings for exclusively rotary movement for axial load only
    • F16C17/08—Sliding-contact bearings for exclusively rotary movement for axial load only for supporting the end face of a shaft or other member, e.g. footstep bearings
    • 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
    • F16C17/10—Sliding-contact bearings for exclusively rotary movement for both radial and axial load
    • 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
    • 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
    • F16C33/12—Structural composition; Use of special materials or surface treatments, e.g. for rust-proofing
    • 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
    • F16C33/14—Special methods of manufacture; Running-in
    • 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
    • H02K7/08—Structural association with bearings

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Power Engineering (AREA)
  • Sliding-Contact Bearings (AREA)
  • Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)

Abstract

The utility model provides a dynamic pressure bearing, a dynamic pressure bearing device and a motor. The dynamic pressure bearing (bearing sleeve (8)) has a sintered body in which dynamic pressure generating portions (A1, A2) are molded in an inner peripheral surface mold. The dynamic pressure generating units (A1, A2) are provided with: a plurality of dynamic pressure grooves (G1) extending in a direction inclined with respect to the circumferential direction; and a plurality of inclined hills (G3) provided between the circumferential directions of the plurality of dynamic pressure grooves (G1). The circumferential width h [ mm ] of each inclined mound (G3) and the depth Hf [ mu ] m of the dynamic pressure groove (G1) adjacent to the circumferential side of the mound (G3) satisfy 0.1 < h/Hf < 0.65, and the variation of the depth Hf of the plurality of dynamic pressure grooves (G1) is 1 [ mu ] m or less.

Description

Dynamic pressure bearing, dynamic pressure bearing device, and motor
Technical Field
The present utility model relates to a dynamic pressure bearing.
Background
The dynamic pressure bearing is a cylindrical bearing member having dynamic pressure grooves formed in an inner peripheral surface thereof. When the dynamic pressure bearing and the shaft member inserted into the inner periphery thereof relatively rotate, the pressure of the fluid film generated in the radial bearing gap between the outer peripheral surface of the shaft member and the inner peripheral surface of the dynamic pressure bearing is increased by the dynamic pressure grooves, and the shaft member is supported so as to be rotatable in a non-contact manner by the pressure (dynamic pressure action). The fluid dynamic bearing device having the dynamic bearing and the shaft member as described above is suitable for use as a rotary shaft support for a spindle motor of a disk drive device for HDD, a polygon scanner motor for laser beam printer, a fan motor for cooling electronic equipment, and the like, because of its excellent rotation accuracy and quietness.
As a method of forming dynamic pressure grooves in the inner peripheral surface of a dynamic pressure bearing, so-called dynamic pressure groove coining is known in which dynamic pressure grooves are molded in the inner peripheral surface of a cylindrical sintered body. In the dynamic pressure groove coining, while the coining pin is inserted into the inner periphery of the sintered body, the sintered body is pressed into the inner periphery of the die by the upper punch and the lower punch while the sintered body is pressed in the axial direction, whereby the inner periphery of the sintered body is pressed against a molding die formed on the outer periphery of the coining pin. Thus, the shape of the molding die is transferred to the inner peripheral surface of the sintered body to form dynamic pressure grooves (for example, refer to patent document 1).
Patent document 1: japanese patent No. 3782900
In a dynamic pressure bearing, the dimensional accuracy of dynamic pressure grooves, in particular, the variation in the depth of a plurality of dynamic pressure grooves becomes a problem. Fig. 14 and 15 are diagrams showing the shape (outline) of the dynamic pressure grooves of the dynamic pressure bearing formed under the same condition. The maximum diameter difference between each dynamic pressure groove and the hills adjacent to the circumferential side thereof is defined as the depths (hereinafter also referred to as "groove depths") Hf1 to Hf6 of each dynamic pressure groove. As shown in fig. 14, there are dynamic pressure grooves having small variations in groove depths Hf1 to Hf6 (dynamic pressure grooves having a difference between the maximum groove depth and the minimum groove depth of about 0.3 μm), and as shown in fig. 15, there are dynamic pressure grooves having large variations in groove depths Hf1 to Hf6 (dynamic pressure grooves having a difference between the maximum groove depth and the minimum groove depth of about 1.5 μm). When the variation in groove depth is large, the variation in dynamic pressure generated in the circumferential direction becomes large, and therefore the bearing rigidity decreases. In particular, when the dynamic pressure bearing is incorporated in motors used in various orientations (for example, cooling fan motors for flat terminals), if the bearing rigidity is low, there is a possibility that the dynamic pressure bearing contacts the shaft and abnormal noise may occur.
Disclosure of utility model
Accordingly, an object of the present utility model is to stably provide a dynamic pressure bearing having high bearing rigidity.
In the mold molding of the dynamic pressure generating grooves, as shown in fig. 7, 9 and 10, the inner peripheral surface of the sintered body 28 is pressed against the molding die 35 formed on the outer peripheral surface of the mandrel bar 31, whereby the material (raw material) of the sintered body 28 is introduced into the concave portion 35a of the molding die 35. At this time, if the ratio h '/Hf' of the circumferential width h '[ mm ] to the depth Hf' [ μm ] of the concave portion 35a is too small, that is, if the circumferential width h 'of the concave portion 35a is too small or the depth Hf' of the concave portion 35a is too deep, the material of the sintered body 28 is difficult to enter the concave portion 35a. Therefore, it is difficult to fill the entire region of the concave portion 35a with the material of the sintered body 28, and the molding accuracy of the hills and, further, the molding accuracy of the dynamic pressure grooves is lowered.
Therefore, in the present utility model, the ratio (flatness) h '/Hf' of the circumferential width h '[ mm ] to the depth Hf' [ μm ] of the concave portion of the molding die is made larger than 0.1. Thus, the material of the sintered body easily enters the corners of the concave portions, and therefore, it is possible to stably provide a product in which the height of the plurality of hills, that is, the variation in the depth of the plurality of dynamic pressure grooves is 1 μm or less. In this case, since the hills formed between the dynamic pressure grooves of the sintered body are transferred with the shape of the concave portion of the plug, the ratio (flatness) h/Hf of the circumferential width h [ mm ] to the height (depth of the dynamic pressure groove adjacent to the circumferential side of the concave portion) Hf [ μm ] of each hills is greater than 0.1.
On the other hand, if the circumferential width h' of the concave portion of the molding die is too large, the volume of the sintered body entering the concave portion becomes large, and therefore a large molding pressure is required to reduce the diameter of the sintered body, resulting in an increase in the size and cost of the molding apparatus. In addition, if the depth Hf' of the concave portion of the molding die is too shallow, the dynamic pressure groove becomes shallow, and therefore there is a possibility that the dynamic pressure is insufficient. Therefore, the ratio h '/Hf' of the circumferential width h '[ mm ] and depth Hf' [ mu ] m ] of the concave portion of the molding die, that is, the ratio h/Hf of the circumferential width h [ mm ] and height Hf [ mu ] m of the hills of the sintered body is preferably smaller than a prescribed value, specifically preferably smaller than 0.65.
As described above, the present utility model is a dynamic pressure bearing having a sintered body in which a dynamic pressure generating portion is molded in an inner peripheral surface mold, the dynamic pressure generating portion comprising: a plurality of dynamic pressure grooves extending in a direction inclined with respect to the circumferential direction; and a plurality of inclined hills provided between the circumferential directions of the plurality of dynamic pressure grooves, a ratio h/Hf of a circumferential width h [ mm ] of each inclined hills to a depth Hf [ mu ] m of the dynamic pressure groove adjacent to a circumferential side of the inclined hills satisfying 0.1 < h/Hf < 0.65, a variation of the depth Hf of the plurality of dynamic pressure grooves being 1 [ mu ] m or less.
If the density of the sintered body is low, it is difficult to apply a pressing force to the inner peripheral surface of the sintered body when the sintered body is pressed from the outer diameter side to mold the dynamic pressure grooves, and therefore it is difficult to mold the dynamic pressure grooves with high accuracy. Therefore, the density of the sintered body is preferably set to be high, and specifically, the density ratio of the sintered body (density of the sintered body/density in the case where no pores are assumed in the sintered body) is preferably set to 80% or more. On the other hand, if the density of the sintered body is too high, pores formed in the sintered body are too small, and the circularity of the lubricating fluid through the pores in the sintered body is impaired, so that the density ratio of the sintered body is preferably 95% or less.
If the density ratio of each part of the sintered body varies greatly, the variation in the rebound amount when the sintered body is taken out from the die increases. In this case, when the mandrel bar is inserted from the inner Zhou Bachu of the sintered body, the portion of the sintered body having a small spring back interferes with the forming die of the mandrel bar, and the portion comes off from the mound, and the variation in height of the mound of the sintered body, that is, the variation in groove depth, increases. Therefore, the variation in density ratio in the axial direction and the radial direction of the sintered body is preferably 3% or less, and the rebound quantity of the sintered body is preferably made uniform.
When the mandrel bar is pulled out from the inner periphery of the sintered body, the corner of the outer diameter end of the mandrel bar forming die interferes with the mound formed on the inner periphery of the sintered body, and the mound of the sintered body may be separated. In order to avoid this, it is preferable to round the corner of the outer diameter end of the mandrel bar forming die in advance. On the other hand, the dynamic pressure groove is desirably formed in a completely rectangular shape in cross-section, and the dynamic pressure is lower as the dynamic pressure groove deviates from the rectangular shape. Therefore, if the corners of the outer diameter end of the molding die are rounded as described above, the corners of the groove bottom of the dynamic pressure groove molded by the molding die are rounded and deviate from the rectangular shape, and therefore, the reduction of dynamic pressure is unavoidable.
Therefore, it is preferable that the corner on the side (axial direction side) interfering with the dynamic pressure grooves when pulled out from the inner periphery of the sintered body is rounded from the corner on the opposite side (axial direction other side) of the corner on the outer diameter end of the forming die of the plug. In this case, in the axial cross section of the sintered body, the corner portion on one side in the axial direction of the groove bottom of the dynamic pressure groove is rounded from the corner portion on the other side in the axial direction. This can ensure dynamic pressure generated by the dynamic pressure grooves and avoid interference between the forming die of the mandrel bar and the hills of the sintered body.
As described above, according to the present utility model, a dynamic pressure bearing having a small variation in groove depth and a high bearing rigidity can be stably provided.
Drawings
Fig. 1 is a cross-sectional view of a fan motor.
Fig. 2 is an axial sectional view of the fluid dynamic bearing device assembled to the fan motor of fig. 1.
Fig. 3 is an axial sectional view of a bearing sleeve (dynamic bearing) of the fluid dynamic bearing device of fig. 2.
Fig. 4 is an axially vertical cross-sectional view of the bearing sleeve at line X-X of fig. 3.
Fig. 5 is an axial sectional view of the coining die and the sintered body, showing a state before the sintered body is inserted into the inner periphery of the die.
Fig. 6 is a side view of the mandrel of the coining die of fig. 5 from the outer periphery.
Fig. 7 is a cross-sectional view in the axial vertical direction of the sintered body and the mandrel bar of fig. 5.
Fig. 8 is an axial sectional view of the coining die and the sintered body, showing a state in which the sintered body is inserted into the inner periphery of the die.
Fig. 9 is an axial vertical sectional view of the sintered body and the mandrel bar of fig. 8.
Fig. 10 is a cross-sectional view in the axial vertical direction of the sintered body and the mandrel taken out from the inner periphery of the die.
Fig. 11 is an axial cross-sectional view showing an example of a sintered body and a mandrel bar taken out from the inner periphery of a die.
Fig. 12 is a side view showing a process of rounding the corner of the mandrel bar forming die.
Fig. 13 is an axial cross-sectional view showing another example of the sintered body and the mandrel bar taken out from the inner periphery of the die.
Fig. 14 is a diagram showing the shape (outline) of dynamic pressure grooves of a dynamic pressure bearing.
Fig. 15 is a diagram showing the shape (outline) of dynamic pressure grooves of a dynamic pressure bearing.
Description of the reference numerals
1: A fluid dynamic bearing device; 2: a shaft member; 3: a rotor; 4: a blade; 5: a motor base; 6a: a stator; 6b: a magnet; 7: a housing; 8: bearing sleeve (dynamic pressure bearing); 9: a sealing member; 10: a thrust plate; 28: a sintered body; 30: coining a die; 31: a core rod; 32: an upper punch; 33: a lower punch; 34: stamping die; 35: a forming die; 35a: an inclined concave portion; 35b: an annular concave portion; 35c: a mound; 50: grinding the material; 55: a spraying device;
a1, A2: a dynamic pressure generating section; g1: dynamic pressure grooves; and G2: a ring-shaped mound; and G3: a sloped mound; r: a radial bearing portion; s: sealing the space; t: a thrust bearing portion.
Detailed Description
Hereinafter, embodiments of the present utility model will be described with reference to the drawings.
Fig. 1 conceptually illustrates one example of a fan motor. The fan motor shown in the figure is incorporated in portable information devices such as notebook personal computers and tablet terminals, and generates an air flow for cooling a heat source such as a CPU. The fan motor includes a fluid dynamic bearing device 1, a motor base 5 constituting a stationary side of the motor, a rotor 3 fixed to a shaft member 2 of the fluid dynamic bearing device 1, blades 4 attached to the rotor 3, and a stator 6a and a magnet 6b disposed to face each other with a radial gap therebetween. The stator 6a is attached to the housing 7 of the hydrodynamic bearing device 1, and the magnet 6b is attached to the rotor 3. The exciting force is generated by energizing the coil of the stator 6a, and the magnet 6b and the rotor 3 are integrally rotated. With the rotation of the rotor 3, an air flow is generated in the axial direction or the radial direction in accordance with the form of the blades 4 attached to the rotor 3.
As shown in fig. 2, the fluid dynamic bearing device 1 includes a shaft member 2, a housing 7, a bearing sleeve 8 as a dynamic bearing according to an embodiment of the present utility model, and a seal member 9. The internal space of the housing 7 is filled with lubricating oil. In the following, for convenience of explanation, the side (upper side in fig. 2) of the shaft member 2 protruding from the housing 7 in the axial direction is referred to as "upper side", and the opposite side (lower side in fig. 2) is referred to as "lower side", but the posture of the hydrodynamic bearing device 1 in use is not intended to be limited.
The shaft member 2 is made of a metal material such as stainless steel. At least a region of the outer circumferential surface 2a of the shaft member 2 facing the inner circumferential surface of the bearing sleeve 8 in the radial direction is a cylindrical surface provided with no irregularities such as dynamic pressure grooves. A convex spherical surface 2b is provided at the lower end of the shaft member 2. A rotor 3 is fixed to the upper end of the shaft member 2.
The housing 7 has a cylindrical portion 7a and a bottom portion 7b closing a lower end opening portion of the cylindrical portion 7 a. In the illustrated example, the cylindrical portion 7a and the bottom portion 7b are integrally formed of a resin or a metal material. The shoulder surface 7b2 is provided at the outer diameter side end of the upper end surface (inner bottom surface 7b 1) of the bottom 7b, and is disposed above the center portion. A stator 6a and a motor base 5 are fixed to an outer peripheral surface 7a2 of the cylindrical portion 7 a.
In the illustrated example, a thrust plate 10 is provided on the inner bottom surface 7b1 of the housing 7. The thrust plate 10 is formed in a disc shape from a material having better slidability than the material forming the housing 7. The convex spherical surface 2b at the lower end of the shaft member 2 is supported in contact with the upper end surface of the thrust plate 10. In this case, the convex spherical surface 2b of the shaft member 2 is supported in contact with the inner bottom surface 7b1 of the housing 7.
The seal member 9 is formed in a ring shape from a resin or a metal material, and is fixed to an upper end portion of the inner peripheral surface 7a1 of the tube portion 7a of the housing 7. The lower end surface 9b of the seal member 9 abuts against the upper end surface 8b of the bearing sleeve 8. The inner peripheral surface 9a of the seal member 9 forms an annular seal space S with the outer peripheral surface 2a of the shaft member 2 facing each other.
The fluid dynamic bearing device 1 is of a so-called partial-filling type in which lubricating oil and air are mixed in the housing 7, but is not limited to this, and may be of a so-called full-filling type in which the entire internal space of the housing 7 is filled with lubricating oil. In the case of the full-packing, the oil surface of the lubricating oil is always maintained within the axial range of the sealed space S.
The bearing sleeve 8 is formed of a cylindrical sintered body obtained by sintering a compression molded body of a metal powder, and is formed of, for example, a copper-based sintered body containing copper as a main component, an iron-based sintered body containing iron as a main component, or a copper-iron-based sintered body containing copper and iron as main components. The bearing sleeve 8 is fixed to the inner periphery of the housing 7 in an oil-containing state in which lubricating oil is impregnated into the inner pores of the sintered body. In the illustrated example, the bearing sleeve 8 is fixed to the inner periphery of the cylindrical portion 7a of the housing 7 in a state in which the lower end surface 8c is in contact with the shoulder surface 7b2 of the bottom portion 7b of the housing 7. The bearing sleeve 8 is fixed to the inner peripheral surface 7a1 of the cylindrical portion 7a by press fitting, bonding, press fitting bonding (both press fitting and bonding), or the like. After the bearing sleeve 8 is fitted in the inner periphery of the housing 7, the bearing sleeve 8 can be fixed to the inner periphery of the housing 7 by sandwiching the bearing sleeve between the seal member 9 and the shoulder surface 7b2 of the housing 7 from both sides in the axial direction.
A dynamic pressure generating portion is formed on an inner peripheral surface 8a of the bearing sleeve 8. In the present embodiment, as shown in fig. 3, dynamic pressure generating portions A1, A2 are provided at two positions in the axial direction of the inner peripheral surface 8a of the sintered body. Each of the dynamic pressure generating portions A1 and A2 is provided with a plurality of dynamic pressure grooves G1 extending in a direction inclined with respect to the circumferential direction and arranged in a circumferential direction, and a plurality of humps (cross-hatched areas) provided between the circumferential directions of the plurality of dynamic pressure grooves G1 and bulging toward the inner diameter side than the groove bottoms of the dynamic pressure grooves G1. In the illustrated example, each of the dynamic pressure generating portions A1 and A2 is provided with dynamic pressure grooves G1 arranged in a herringbone shape, annular mounds G2, and a plurality of inclined mounds G3 extending from the annular mounds G2 to both sides in the axial direction and provided between the circumferential directions of the plurality of dynamic pressure grooves G1. The inner diameter surfaces of the annular mound G2 and the inclined mound G3 are disposed on the same cylindrical surface. The groove bottoms of the dynamic pressure grooves G1 are arranged on the same cylindrical surface. The inner peripheral surface 8a of the bearing sleeve 8 is a molding surface formed by pressing a mold over the entire area including the bottom surface of the dynamic pressure groove G1, the annular dome G2, and the inner diameter surface of the inclined dome G3.
An axial groove 8d1 is formed in the outer peripheral surface 8d of the bearing sleeve 8. A radial groove 8b1 and an annular groove 8b2 are formed in the upper end surface 8b of the bearing sleeve 8. A radial groove 8c1 is formed in the lower end surface 8c of the bearing sleeve 8. The annular groove 8b2 is provided to identify the vertical direction (i.e., the rotational direction) when the bearing sleeve 8 is assembled to the housing 7. The axial groove 8d1 and the radial grooves 8b1, 8c1 form a communication path (see fig. 2) for communicating the space facing the bottom 7b of the housing 7 with the atmosphere in the hydrodynamic bearing device 1. If not particularly required, any one or all of the radial grooves 8b1, 8c1, the annular groove 8b2, and the axial groove 8d1 may be omitted.
Fig. 4 is a view in which an axial vertical sectional view (an X-X sectional view in fig. 3) of the dynamic pressure groove G1 in the axial center of the bearing sleeve 8 is developed so that the circumferential direction is linear, and the radial direction (vertical direction in the drawing) is exaggerated. The ratio (flatness) h/Hf of the circumferential width h [ mm ] of each inclined dome G3 formed on the inner peripheral surface 8a of the bearing sleeve 8 to the depth Hf [ mu ] m of the dynamic pressure groove G1 adjacent to the circumferential side of the inclined dome G3 satisfies 0.1 < h/Hf < 0.65. The depth Hf of the dynamic pressure groove G1 is a difference between the minimum diameter of the top surface (inner diameter surface) of each inclined dome G3 and the maximum diameter of the bottom surface of the dynamic pressure groove G1 adjacent to one side (left side in fig. 4) of the inclined dome G3 in the circumferential direction. On the other hand, the circumferential width h of the inclined dome G3 is the circumferential dimension of the least square line L of the dynamic pressure grooves G1 and the inclined dome G3 (the line L drawn so that the total area S1 on the outer diameter side of the line L of all dynamic pressure grooves G1 in the circumferential direction is equal to the total area S2 on the inner diameter side of the line L of all inclined domes G3 in the circumferential direction in the cross section in the axial vertical direction shown in fig. 4). The depth of all the dynamic pressure grooves G1 formed in the inner peripheral surface 8a of the bearing sleeve 8 is substantially uniform, and specifically, the variation in the depth Hf of each dynamic pressure groove G1 is 1 μm or less. That is, the difference between the depth Hf (MAX) of the deepest dynamic pressure groove G1 and the depth Hf (MIN) of the shallowest dynamic pressure groove G1 among the plurality of dynamic pressure grooves G1 is 1 μm or less.
The density ratio of the bearing sleeve 8 is 80% -95%. The density ratio of the bearing sleeve 8 is a value measured in a dry state in which oil is not impregnated into the pores in the sintered body. The density ratio of the sintered body forming the bearing sleeve 8 varies by 3% or less in the axial direction and the radial direction. Specifically, the difference between the density ratios of the portions that trisect the sintered body in the axial direction and the density ratio of the portions that trisect the sintered body in the radial direction are each 3% or less.
In the fluid dynamic bearing device 1 having the above-described configuration, when the shaft member 2 rotates, a radial bearing gap is formed between the outer peripheral surface 2a of the shaft member 2 and the inner peripheral surface 8a of the bearing sleeve 8. Further, the dynamic pressure generating portions A1 and A2 (dynamic pressure grooves G1) formed on the inner circumferential surface 8a of the bearing sleeve 8 can increase the pressure of the oil film generated in the radial bearing gap, and the radial bearing portion R (see fig. 2) radially supporting the shaft member 2 can be formed by the pressure (dynamic pressure action). The convex spherical surface 2b at the lower end of the shaft member 2 is in sliding contact with the upper end surface of the thrust plate 10 mounted on the bottom 7b of the housing 7, thereby forming a thrust bearing portion T that supports (contacts and supports) the shaft member 2 in the thrust direction.
Hereinafter, a method of manufacturing the bearing sleeve 8 will be described.
The bearing sleeve 8 is manufactured by sequentially performing a compression molding process, a sintering process, and a coining process.
In the compression molding step, a raw material powder mainly composed of a metal powder is compression molded to form a cylindrical powder compact having substantially the same shape as the bearing sleeve 8 of fig. 3. The inner peripheral surface of the compact is cylindrical without irregularities. An axial groove 8d1, a radial groove 8b1, and a radial groove 8c1 are formed in the outer peripheral surface, the upper end surface, and the lower end surface of the compact, respectively. As the raw material powder, a mixed powder is used which is obtained by adding and mixing various fillers such as a molding aid and a solid lubricant to a metal powder { for example, one or more of a copper-based powder (copper powder or copper-based alloy powder), an iron-based powder (iron powder or iron-based alloy powder), and a copper-iron-based alloy powder } as a main raw material.
In the sintering step, the green compact is heated at a predetermined sintering temperature to obtain a sintered body in which adjacent particles of the metal powder are bonded to each other via the sintering neck. The density ratio of the sintered body thus formed is 80% to 95%. The density ratio of the sintered body 28 in the axial direction and the radial direction varies by 3% or less. In other words, the compression ratio in the compression molding step, the sintering temperature and time in the sintering step, and the like are set so that the density ratio of the sintered body satisfies the above conditions.
In the coining step, a dynamic pressure groove is formed in the inner peripheral surface 28a of the sintered body 28 by a coining die 30 shown in fig. 5. The coining die 30 has a core rod 31, an upper punch 32, a lower punch 33, and a die 34. A forming die 35 is formed on the outer peripheral surface of the mandrel bar 31. As shown in fig. 6, the molding die 35 has a mound 35c, an annular recess 35b, and an inclined recess 35a. In the illustrated example, concave portions 35a and 35b (scattered point regions) are formed in the cylindrical outer peripheral surface of the mandrel bar 31, and regions remaining between the circumferential directions of the inclined concave portions 35a are referred to as hills 35c. The hills 35c, the annular concave portions 35b, and the inclined concave portions 35a are each formed by inverting the concave-convex shapes of the dynamic pressure grooves G1, the annular hills G2, and the inclined hills G3 shown in fig. 3. The ratio (flatness) h '/Hf' of the circumferential width h '[ mm ] to the depth Hf' [ μm ] of each inclined concave portion 35a satisfies 0.1 < h '/Hf' < 0.65 (see fig. 7). The depth Hf' of each inclined concave portion 35a is the maximum difference between the bottom surface (outer diameter surface) of each inclined concave portion 35a and the outer diameter surface of the mound 35c adjacent to the circumferential side of the inclined concave portion 35a.
First, a mandrel bar 31 is inserted into the inner periphery of the sintered body 28, and the axial width of the sintered body 28 is restrained by upper and lower punches 32, 33. At this time, since the inner diameter of the sintered body 28 is slightly larger than the outer diameter of the plug 31, a small radial gap is formed between the inner peripheral surface of the sintered body 28 and the outer peripheral surface of the plug 31 (see fig. 7).
Next, as shown in fig. 8, the sintered body 28 is pressed into the inner periphery of the die 34 while maintaining the relative positions of the sintered body 28, the mandrel bar 31, and the upper and lower punches 32, 33 in the axial direction in the state shown in fig. 5. Thus, the sintered body 28 is compressed from the axial sides and the outer Zhou Yapai, and the inner peripheral surface 28a of the sintered body 28 is pressed against the forming die 35 (see fig. 9) formed on the outer peripheral surface of the mandrel bar 31. As a result, the shape of the molding die 35 is transferred to the inner peripheral surface 28a of the sintered body 28 to mold the dynamic pressure grooves G1 and the hills G2, G3.
When the inner peripheral surface 28a of the sintered body 28 is pressed against the molding die 35 in this way, the flatness h '/Hf' of the inclined concave portion 35a is greater than 0.1, and thus the material (raw material) of the sintered body 28 easily enters the inclined concave portion 35a. This can fill the material of the sintered body 28 up to the corners of the inclined concave portions 35a, and thus the height of the inclined hillock G3 formed by the inclined concave portions 35a, that is, the accuracy of the depth Hf of the dynamic pressure groove G1 adjacent to the inclined hillock G3 can be improved. Therefore, as described above, the depth of the dynamic pressure grooves G1 formed in the inner peripheral surface of the sintered body 28 by the mold can be made substantially uniform, and specifically, the variation in the depth Hf of all dynamic pressure grooves G1 can be suppressed to 1 μm or less.
Thereafter, the sintered body 28, the mandrel bar 31, and the upper and lower punches 32 and 33 are raised, and the sintered body 28 and the mandrel bar 31 are taken out from the inner periphery of the die 34. At this time, the inner peripheral surface 28a of the sintered body 28 expands in diameter due to rebound, and is peeled off from the forming die 35 on the outer peripheral surface of the mandrel bar 31 (see fig. 10). Thereafter, the plug 31 is pulled out from the inner periphery of the sintered body 28 (i.e., the bearing sleeve 8) in which the dynamic pressure grooves G1, the annular hump G2, and the inclined hump G3 are formed on the inner peripheral surface.
In the present embodiment, since the density ratio of the sintered body 28 is set to be high (80% to 95%) and the density ratio is substantially uniform in the axial direction and the radial direction as described above, the variation in the rebound quantity of the sintered body 28 can be suppressed, and the entire inner peripheral surface 28a of the sintered body 28 can be uniformly expanded in diameter. Thus, since the hills G2 and G3 molded on the inner peripheral surface 28a of the sintered body 28 and the molding die 35 provided on the outer peripheral surface of the plug 31 do not interfere with each other easily, the hills G2 and G3 can be prevented from falling off, and the variation in the depth Hf of all the dynamic pressure grooves G1 can be suppressed to 1 μm or less more reliably.
The present utility model is not limited to the above-described embodiments. Hereinafter, other embodiments of the present utility model will be described, but the description of the same points as those of the above embodiments will be omitted.
For example, as shown in fig. 11, when the corners e1 and e2 of the outer diameter end of the mound 35c of the forming die 35 formed on the outer peripheral surface of the mandrel bar 31 are sharp (are pin corners), when the mandrel bar 31 is pulled from the inner circumferential axial side (arrow direction in the drawing) of the sintered body 28 (bearing sleeve 8) on which the dynamic pressure grooves G1 are formed, there is a possibility that the corner e1 on the axial side of the mound 35c interferes with the mounds G2 and G3 of the inner peripheral surface of the sintered body 28, and the mounds G2 and G3 come off.
Therefore, the corner of the outer diameter end of the forming die 35 of the mandrel bar 31 may be rounded. Specifically, as shown in fig. 12, by blowing the abrasive 50 to the workpiece (in this case, the mandrel bar 31) by the blasting device 55, the surface of the workpiece is polished by friction with the abrasive 50, and the corners of the outer diameter ends of the hills 35c of the molding die 35 are rounded. In particular, in the illustrated example, the core rod 31 is set at a predetermined inclination angle with respect to the projection direction of the abrasive 50. That is, when the projection direction of the abrasive 50 is the X direction and the direction perpendicular to the X direction is the Y direction, the axial center of the mandrel bar 31 is inclined at a predetermined angle α with respect to the Y direction. In the illustrated example, the axial center of the mandrel bar 31 is inclined with respect to the Y direction perpendicular to the projection direction X of the abrasive 50 so that an end portion on one axial side (opposite axial end side, right side in the drawing) of the forming die 35 of the mandrel bar 31 is closer to the injection device 55 than an end portion on the other axial side (axial end side, left side in the drawing). As described above, by blowing the abrasive 50 from the inclined direction toward the forming die 35 of the mandrel bar 31, as shown in fig. 13, the corner e1 of one axial side (downstream side in the drawing direction of the mandrel bar 31, right side in the drawing) of each mound 35c is rounded to the corner e2 of the other axial side (upstream side in the drawing direction of the mandrel bar 31, left side in the drawing) of each mound 35 c. The corner f1 on one side in the axial direction of the groove bottom of the dynamic pressure groove G1 molded by the molding die 35 is rounded to the corner f2 on the other side in the axial direction. Whether or not the corner f1 of the dynamic pressure groove G1 is smoother than the corner f2 can be determined by analyzing and reading the curvatures of the corners f1 and f2 in a state of being vertically and horizontally doubled by acquiring a groove shape map (see fig. 13) of the dynamic pressure bearing (bearing sleeve 8) in the axial direction by a shape measuring machine.
As described above, by rounding the corner e1 on the axial side of each mound 35c, the mounds G2, G3 can be prevented from falling off due to interference between the corner e1 and the mounds G2, G3 when the mandrel bar 31 is pulled from the inner circumferential axial side (arrow direction in fig. 13) of the sintered body 28. Further, by not rounding the corner e2 on the other side in the axial direction, the shape of the hills G2, G3, and thus the shape of the dynamic pressure groove G1 can be made nearly rectangular, so that the dynamic pressure of the dynamic pressure groove G1 can be ensured.
The process of rounding the corners of the molding die 35 may be performed by a manual operation, in addition to the above-described spraying device.
The shape of the dynamic pressure groove G1 formed on the inner peripheral surface of the dynamic pressure bearing (bearing sleeve 8) is not limited to the above-described shape. For example, the annular hump G2 may be omitted, and the dynamic pressure groove G1 inclined to one side with respect to the circumferential direction and the dynamic pressure groove G1 inclined to the other side may be continued, and the inclined hump G3 inclined to one side with respect to the circumferential direction and the inclined hump G3 inclined to the other side may be continued. The dynamic pressure generating portions A1 and A2 may be separated in the axial direction and a cylindrical surface may be provided therebetween.
Further, a dynamic pressure generating portion (for example, a spiral dynamic pressure groove and a mound) may be formed on one end surface in the axial direction of the dynamic pressure bearing. In this case, the flange portion is provided on the shaft member, and the pressure of the fluid film generated in the thrust bearing gap between the one end surface in the axial direction of the dynamic pressure bearing and the end surface of the flange portion of the shaft member is increased by the dynamic pressure generating portion provided on the end surface of the dynamic pressure bearing, and the shaft member is supported in a noncontact manner in the thrust direction by the pressure.
In the above embodiment, the dynamic pressure bearing is shown as the fixed side and the shaft member is shown as the rotating side, but the present invention is not limited to this, and the shaft member may be set as the fixed side and the dynamic pressure bearing may be set as the rotating side.
The dynamic pressure bearing of the present utility model is not limited to the sintered oil-impregnated bearing having lubricating oil impregnated therein as described above, and may be used in a dry state without impregnating lubricating oil. The fluid dynamic bearing device 1 having the dynamic bearing of the present utility model is not limited to a fan motor, and can be applied to a spindle motor of a disk drive device for HDD and a polygon scanner motor of a laser beam printer.

Claims (5)

1. A dynamic pressure bearing comprising a sintered body having a dynamic pressure generating portion molded in an inner peripheral surface mold, characterized in that,
The dynamic pressure generating portion includes:
A plurality of dynamic pressure grooves extending in a direction inclined with respect to the circumferential direction; and
A plurality of inclined hills provided between the circumferential directions of the plurality of dynamic pressure grooves,
The ratio h/Hf of the circumferential width h [ mm ] of each inclined dome to the depth Hf [ mu ] m of the dynamic pressure groove adjacent to the circumferential side of the inclined dome satisfies 0.1 < h/Hf < 0.65,
The variation in depth Hf of the plurality of dynamic pressure grooves is 1 μm or less.
2. The dynamic pressure bearing as claimed in claim 1, wherein,
The density ratio of the sintered body is 80-95%,
The density ratio of the sintered body in the axial direction and the radial direction varies by 3% or less.
3. Dynamic pressure bearing as claimed in claim 1 or 2, characterized in that,
In the axial cross section of the sintered body, a corner of one side in the axial direction of the groove bottom of the dynamic pressure groove is rounded than a corner of the other side in the axial direction.
4. A dynamic pressure bearing device is characterized in that,
The dynamic pressure bearing device comprises:
The dynamic pressure bearing as claimed in claim 1 or 2; and
And a shaft member inserted into an inner periphery of the dynamic pressure bearing.
5. A motor is characterized in that,
The motor has the dynamic pressure bearing device, stator and magnet as claimed in claim 4.
CN202322504096.2U 2022-09-16 2023-09-14 Dynamic pressure bearing, dynamic pressure bearing device, and motor Active CN220850360U (en)

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JPH05177545A (en) * 1991-12-28 1993-07-20 Konica Corp Blasting device, dynamic pressure type air bearing, and polygon mirror unit
JP4414574B2 (en) * 2000-08-22 2010-02-10 日立粉末冶金株式会社 Manufacturing method of sintered bearing with dynamic pressure groove
JP2007170577A (en) * 2005-12-22 2007-07-05 Sony Corp Method for manufacturing member for dynamic pressure bearing
JP6199675B2 (en) * 2013-09-24 2017-09-20 Ntn株式会社 Sintered metal bearing and fluid dynamic pressure bearing device provided with the bearing
JP6466105B2 (en) * 2014-09-01 2019-02-06 Ntn株式会社 Fluid dynamic bearing device and bearing member and shaft member used therefor
JP6961332B2 (en) * 2016-09-09 2021-11-05 Ntn株式会社 Dynamic pressure bearings and their manufacturing methods

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