Dynamic pressure bearing, fluid dynamic pressure bearing device, and motor

Abstract

The dynamic pressure generating portion has a plurality of dynamic pressure grooves arranged in a herringbone shape, and the dynamic pressure grooves are provided with a first dynamic pressure groove group and a second dynamic pressure groove group. An inclined hill portion in an inclined shape is formed between the dynamic pressure grooves of the first dynamic pressure groove group and the second dynamic pressure groove group. An annular hill portion that is connected to each of the inclined hill portions and extends in the circumferential direction is provided between the first dynamic pressure groove group and the second dynamic pressure groove group. A recess for generating dynamic pressure is formed in a portion of the annular hill portion.

Description

Technical Field

[0001] This invention relates to hydrodynamic bearings, hydrodynamic bearing devices, and motors. Background Technology

[0002] A hydrodynamic bearing assembly provides non-contact support for a shaft member, allowing it to rotate freely relative to the shaft member through pressure generated by a fluid film (e.g., an oil film) in the radial bearing clearance between the outer circumferential surface of the shaft member and the inner circumferential surface of the bearing member. Due to its high-speed rotational accuracy and quiet operation, hydrodynamic bearing assemblies are suitable for use in small motors such as spindle motors in information equipment (e.g., disk drives such as HDDs, CD-ROMs, CD-R / RWs, DVD-ROMs / RAMs, Blu-ray discs, MDs, MOs), polygon scanner motors in laser beam printers (LBPs), color wheels in projectors, or cooling fans in electrical equipment.

[0003] Portable information devices such as laptops and tablets (so-called mobile devices) have a strong demand for thinness. Furthermore, in recent years, the advancement of high-functionality in information devices designed to support 5G (5th-Generation) has increased heat generation from circuitry, thus increasing the requirements for cooling performance. Consequently, there is a trend towards larger impellers mounted on the rotating shaft. This, in turn, increases the load on the hydrodynamic bearing assembly supporting the rotating shaft of the fan motor. Here, 5G (5th-Generation) refers to the "fifth-generation mobile communication system," whose main characteristics include "high speed and high capacity," "simultaneous connection of multiple devices," and "ultra-low latency."

[0004] As a hydrodynamic bearing for thin-film fan motors, the hydrodynamic bearing described in Patent Document 1 is a prior art example. The hydrodynamic bearing described in Patent Document 1 improves bearing rigidity against torque loads and suppresses shaft oscillation without increasing the axial dimension. In this case, two rows of hydrodynamic generating parts with different groove (hydrodynamic groove) specifications are arranged axially.

[0005] Prior art literature

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2022-54860 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, regarding the hydrodynamic bearing described in Patent Document 1, motors using hydrodynamic bearings suffer from the following issues: the slot specifications need to be changed depending on the position of the rotor's center of gravity, resulting in poor versatility and high cost. Furthermore, in this case, the upper and lower slot specifications are different, so even if the motors have the same specifications but different rotation directions, they cannot be accommodated by simply flipping them upside down.

[0010] Therefore, in view of the above-mentioned problems, the present invention provides a hydrodynamic bearing, a hydrodynamic bearing device, and a motor that can increase the load capacity without increasing the axial dimension and without compromising versatility.

[0011] Methods for solving problems

[0012] This invention relates to a hydrodynamic bearing having an inner diameter surface facing the outer diameter surface of a shaft member, and a hydrodynamic pressure generating portion thereon. The hydrodynamic pressure generating portion has a plurality of hydrodynamic pressure grooves arranged in a herringbone shape. The hydrodynamic pressure grooves are provided with a first hydrodynamic pressure groove group and a second hydrodynamic pressure groove group separated along the axial direction. Inclined mounds are formed between the hydrodynamic pressure grooves of the first hydrodynamic pressure groove group and the second hydrodynamic pressure groove group. An annular mound is provided between the first hydrodynamic pressure groove group and the second hydrodynamic pressure groove group, which is connected to each inclined mound and extends circumferentially. A recess for generating hydrodynamic pressure is formed in a portion of the annular mound.

[0013] According to the hydrodynamic bearing of the present invention, a stepped portion is formed between the inclined groove (hydrodynamic groove) and the annular mound in each hydrodynamic groove group, and pressure (hydrodynamic pressure) is generated at the step. Pressure (hydrodynamic pressure) is also generated downstream of the recess in the rotational direction of the recess through the recess of the annular mound. That is, by providing a recess in the annular mound for generating pressure through a wedge effect, the load capacity is increased.

[0014] Preferably, the recess for generating the dynamic pressure is provided at the junction of the annular mound and the inclined mound, and the circumferential width of the recess is smaller than the circumferential width of the junction. The number of dynamic pressure grooves in the first dynamic pressure groove group and the second dynamic pressure groove group is set to be the same. The junction of the inclined mound and the annular mound of the first dynamic pressure group and the junction of the inclined mound and the annular mound of the second dynamic pressure group are the same, and the recess is provided in all the junctions.

[0015] By providing recesses at all the junctions of the annular mound and the inclined mound, the load capacity can be further increased. Furthermore, by making the circumferential width of the recesses smaller than the circumferential width of the junctions, the recesses can be set to be larger within a dimension that does not connect with the outlines of the annular mounds and the inclined mounds, thereby further increasing the load capacity.

[0016] Alternatively, a pair of hydrodynamic generating parts with an axially separated, up-and-down flipping shape can be formed on the inner diameter surface of the bearing. With this configuration, motors of the same specifications but different rotation directions can be accommodated by flipping up and down.

[0017] The hydrodynamic bearing device according to the present invention includes the hydrodynamic bearing, a shaft member inserted into the inner circumference of the hydrodynamic bearing, and a radial bearing portion that supports the relative rotation of the shaft member by the hydrodynamic pressure of a lubricating fluid in a radial bearing clearance formed between the inner circumferential surface of the hydrodynamic bearing and the outer circumferential surface of the shaft member.

[0018] According to the hydrodynamic bearing device of the present invention, a hydrodynamic bearing capable of increasing load capacity is used, so that even if the axial dimension of the bearing is to be reduced to a thinner profile, the load supporting the bearing can be applied.

[0019] The motor according to the present invention includes the hydrodynamic bearing device, a rotor that rotates integrally with the shaft member or the hydrodynamic bearing, and a drive unit that drives the rotor to rotate, the rotor having an impeller portion.

[0020] Even with an increased impeller size, the load applied to the bearing can still be adequately supported, thus improving cooling performance.

[0021] Invention Effects

[0022] In this invention, the load capacity is increased, thus allowing the bearing to function fully even when miniaturization is desired. In other words, a bearing with increased load capacity can be provided without increasing the axial dimension. Furthermore, in motors using this hydrodynamic bearing, there is no need to change the slot specifications based on the rotor's center of gravity, etc., and there is no concern about compromising versatility as a bearing. Attached Figure Description

[0023] Figure 1 This is a cross-sectional view of the hydrodynamic bearing involved in this invention.

[0024] Figure 2 yes Figure 1 A simplified enlarged view of the main parts.

[0025] Figure 3 This is a cross-sectional view of a hydrodynamic bearing device using the hydrodynamic bearing involved in this invention.

[0026] Figure 4 It has Figure 3 A cross-sectional view of the motor of the hydrodynamic bearing assembly shown.

[0027] Figure 5 This is a simplified diagram of the dynamic pressure groove.

[0028] Figure 6AThe embodiment 1 is shown, and it is a tank specification diagram.

[0029] Figure 6B The embodiment 1 is shown, and it is a pressure distribution diagram.

[0030] Figure 7A The diagram shows comparison item 1 and the tank specifications.

[0031] Figure 7B The diagram shows comparison sample 1 and its pressure distribution.

[0032] Figure 8A The diagram shows comparison item 2 and the tank specifications.

[0033] Figure 8B The diagram shows comparison sample 2 and a pressure distribution map.

[0034] Figure 9A This shows the previous product 1, and is a tank specification diagram.

[0035] Figure 9B The diagram shows the pressure distribution of the previous product 1.

[0036] Figure 10 This is a cross-sectional view of the hydrodynamic bearing used in embodiment 2.

[0037] Figure 11 This is a cross-sectional view of the hydrodynamic bearing previously used in Product 2. Detailed Implementation

[0038] The following is based on Figures 1-4 The embodiments of the present invention will be described below. Figure 1 This embodiment illustrates the hydrodynamic bearing. Figure 2 This shows a simplified enlarged view of the main components of the hydrodynamic bearing. Figure 3 A hydrodynamic bearing device using the hydrodynamic bearing according to the present invention is shown. Figure 4 A cooling fan motor using this hydrodynamic bearing device is shown. This fan motor is, for example, assembled in information equipment, especially in mobile devices such as mobile phones and tablet terminals.

[0039] The fan motor includes a hydrodynamic bearing assembly 1 according to one embodiment of the present invention, a rotor 3 mounted to a shaft member 2 of the hydrodynamic bearing assembly 1, an impeller (blade) 4 mounted to the outer diameter end of the rotor 3, a stator coil 6a and a rotor magnet 6b facing each other with a radial gap, and a housing 5 housing them. The stator coil 6a is mounted on the outer periphery of the hydrodynamic bearing assembly 1, and the rotor magnet 6b is mounted on the inner periphery of the rotor 3. By energizing the stator coil 6a, the rotor 3, impeller 4, and shaft member 2 rotate as a unit, thereby generating airflow in the axial or outer radial direction.

[0040] Hydrodynamic bearing device 1 Figure 3 As shown, it includes a shaft member 2, a housing 7, a bearing sleeve 8 (which is the hydrodynamic bearing according to the present invention), a sealing member 9, and a thrust bearing member 10. It should be noted that, hereinafter, in the axial direction ( Figure 2 In the vertical direction, the opening side of the outer casing 7 is called the upper side, and the bottom 7b side of the outer casing 7 is called the lower side.

[0041] The shaft member 2 is formed into a cylindrical shape from a metal material such as stainless steel. The shaft member 2 has a cylindrical outer peripheral surface 2a and a spherical protrusion 2b provided at the lower end.

[0042] The outer casing 7 has a generally cylindrical side portion 7a and a bottom portion 7b that closes the opening below the side portion 7a. In the example shown, the side portion 7a and the bottom portion 7b are integrally injection molded from resin. The outer casing 5 and the stator coil 6a are fixed to the outer peripheral surface 7a2 of the side portion 7a. The bearing sleeve 8 is fixed to the inner peripheral surface 7a1 of the side portion 7a. A shoulder surface 7b2 is provided at the outer diameter end of the upper end face 7b1 of the bottom portion 7b, which is located above the inner diameter portion, and the lower end face 8c of the bearing sleeve 8 abuts against the shoulder surface 7b2. A circumferential notch 7b4 is formed on the outer peripheral surface 7a2 of the side portion 7a, and the stator coil 6a is fitted into the circumferential notch 7b4. A resin thrust bearing member 10 is disposed at the center of the upper end face 7b1 of the bottom portion 7b. It should be noted that, instead of providing a radial groove 7b3 on the shoulder surface 7b2 of the housing 7, a radial groove may also be formed on the lower end face 8c of the bearing sleeve 8.

[0043] The bearing sleeve 8 is cylindrical and is fixed to the inner circumferential surface 7a1 of the side portion 7a of the housing 7 by appropriate methods such as gap bonding, pressing, and press-fit bonding (press-fitting with adhesive). In this embodiment, the bearing sleeve 8 can be made of sintered metal obtained by stamping, molten materials such as brass or stainless steel obtained by machining, or resin obtained by injection molding.

[0044] A pair of dynamic pressure generating units 20 (20A, 20B) are axially separated and disposed on the inner circumferential surface 8a of the bearing sleeve 8, which serves as the radial bearing surface. Each dynamic pressure generating unit 20A, 20B has a plurality of dynamic pressure grooves 11a, 11b arranged in a herringbone shape. The dynamic pressure grooves 11a, 11a on the outer axial sides of the dynamic pressure generating units 20A, 20B form a first dynamic pressure groove group 11A, 11A, and the dynamic pressure grooves 11b, 11b on the inner axial sides of the dynamic pressure generating units 20 form a second dynamic pressure groove group 11B, 11B. It should be noted that the pair of dynamic pressure generating units 20A, 20B are configured to be flipped upside down.

[0045] Furthermore, in each dynamic pressure generating unit 20A, 20B, the axially outer dynamic pressure grooves 11a, 11a and the axially inner dynamic pressure grooves 11b, 11b have different inclination directions. In the example shown, the axially outer dynamic pressure grooves 11a, 11a are inclined from the axially outer side to the axially inner side along the rotation direction of the shaft member 2, while the axially inner dynamic pressure grooves 11b, 11b are inclined from the axially inner side to the axially outer side along the rotation direction of the shaft member 2. The bottom surfaces of the dynamic pressure grooves 11a, 11b are provided on the same cylindrical surface. The bottom surface of the axially inner dynamic pressure groove 11b is continuous with the cylindrical surface 13 provided between the two dynamic pressure generating units 20 (20A, 20B) in the axial direction.

[0046] Inclined mounds 11c and 11d are respectively provided between dynamic pressure grooves 11a and 11b. Additionally, in each dynamic pressure generating unit 20 (20A, 20B), annular mounds 11e and 11e are provided between the first dynamic pressure groove group 11A and the second dynamic pressure groove group 11B. The inclined mounds 11c and 11d and the annular mounds 11e and 11e are shown in cross-sectional lines. The annular mounds 11e and 11e and the inclined mounds 11c and 11d rise from the bottom surface of the dynamic pressure grooves 11a and 11b towards the inner diameter side. The inner diameter surfaces of the annular mounds 11e and 11e and the inclined mounds 11c and 11d are provided on the same cylindrical surface. The annular mounds 11e and 11e are continuously provided with all the inclined mounds 11c and 11d.

[0047] Furthermore, when the axial lengths (width dimensions) of the first dynamic pressure groove group 11A and the second dynamic pressure groove group 11B are set to A and B, respectively, and the axial lengths (width dimensions) of the annular mounds 11e and 11e are set to C, A=B>C. Additionally, in each of the first dynamic pressure generating sections 20A and the second dynamic pressure generating section 20B, the inclination angle θa of the first dynamic pressure groove groups 11A and 11A relative to the circumferential dynamic pressure grooves 11a and 11a (refer to...) Figure 2 The inclination angle θb of the second dynamic pressure groove group 11B, 11B relative to the dynamic pressure grooves 11b, 11b in the circumferential direction (refer to) Figure 2 )equal.

[0048] Each of the annular mounds 11e has a recess 11e1. In this case, the recess 11e1 is formed at the junction U of the inclined mounds 11c and 11d and the annular mound 11e. The recess 11e1 is rectangular in shape in the illustration, and its depth dimension is set to be the same as the height dimension of the annular mound 11e. That is, the bottom surface of the recess 11e1 coincides with the cylindrical surface 13. In addition, the width dimension (axial length) of the recess 11e1 is set to be the same as the width dimension (axial length) of the annular mound 11e. In this case, the circumferential length of the recess 11e1 is set to be the dimension that does not protrude from the junction U. That is, when the circumferential length of the junction U is set to L and the circumferential length of the recess 11e1 is set to L1, L > L1. In addition, when the axial length of the junction U is set to H and the bearing axial length of the recess 11e1 is set to H1, H ≥ H1.

[0049] Furthermore, the bearing sleeve 8 is specifically formed of sintered metal, for example, sintered metal containing 35 wt.% or more of copper, and particularly sintered metal containing 35 wt.% or more of both copper and iron. The bearing sleeve 8 is manufactured by the following method. First, raw material powder is compressed and formed into a pressed powder body (powder pressing process). The raw material powder includes either or both of copper-based powder (copper powder or copper alloy powder) and iron-based powder (iron powder or iron alloy powder) as the main component metal powder. The raw material powder may also include high-hardness powders such as stainless steel powder. In this embodiment, the raw material powder includes pure iron powder and pure copper powder as the main component metal powder. In addition to the main component metal powder, the raw material powder may also include low-melting-point metal powders such as tin powder, carbon powders such as graphite powder, or forming lubricants. The pressed powder body is sintered at a specified sintering temperature to obtain a sintered body (sintering process). The sintered body is then subjected to fine pressing to form dynamic pressure grooves 11, 11 on the inner circumferential surface (fine pressing process). In this embodiment, the inner circumferential surface of the sintered body is subjected to sealing treatment such as rotary precision pressing. The bearing sleeve 8 is completed by immersing lubricating oil in the internal pores of the sintered body.

[0050] The density ratio of the bearing sleeve 8 is 80-95%. The bearing sleeve 8 has connecting pores that communicate between the interior and the surface; specifically, it has connecting pores with an oil content of 4% or more. That is, the forming conditions of the bearing sleeve 8 (e.g., compression ratio in the powder pressing process and the precision pressing process) are set to form connecting pores with an oil content of 4% or more. The surface opening ratio of the inner circumferential surface 8a (radial bearing surface) of the bearing sleeve 8 obtained by precision pressing is less than or equal to the porosity (=100% - density ratio) of the bearing sleeve 8, specifically less than 10%, preferably less than 8%, and more preferably less than 5%. By setting the opening ratio to less than 10%, dynamic pressure leakage from the inner diameter surface 8a can be effectively prevented.

[0051] It should be noted that an axial groove 8d1 is formed on the outer circumferential surface of the bearing sleeve 8. The number of axial grooves 8d1 is arbitrary, for example, they are formed at three equally spaced locations in the circumferential direction.

[0052] The sealing member 9 is formed into a ring shape from resin or metal and is fixed to the upper end of the inner circumferential surface 7a1 of the side portion 7a of the housing 7. The sealing member 9 abuts against the upper end face 8b of the bearing sleeve 8. The inner circumferential surface 9a of the sealing member 9 and the outer circumferential surface 2a of the shaft member 2 are opposed in the radial direction, forming a sealing space S between them. When the shaft member 2 rotates, the sealing space S prevents the lubricating oil inside the bearing from leaking to the outside. A radial groove 9b1 is formed on the lower end face 9b of the sealing member 9. It should be noted that, instead of forming a radial groove 9b1 on the lower end face 9b of the sealing member 9, a radial groove may also be formed on the upper end face 8b of the bearing sleeve 8 (or in addition).

[0053] The aforementioned hydrodynamic bearing assembly 1 is assembled through the following steps: First, the thrust bearing member 10 is fixed to the upper end face 7b1 of the bottom 7b of the housing 7. Then, a bearing sleeve 8, pre-lubricated with lubricating oil in its internal pores, is inserted into the inner circumference of the side portion 7a of the housing 7. With the lower end face 8c of the bearing sleeve 8 abutting against the shoulder face 7b2 of the bottom 7b, the outer circumferential surface 8d of the bearing sleeve 8 is fixed to the inner circumferential surface 7a1 of the side portion 7a. Next, the sealing member 9 is fixed to the upper end of the inner circumferential surface 7a1 of the side portion 7a of the housing 7. At this time, the sealing member 9 is pressed into the side portion 7a of the housing 7, and the bearing sleeve 8 is clamped from both axial sides by the sealing member 9 and the shoulder face 7b2 of the bottom 7b of the housing 7, thereby constraining the bearing sleeve 8 axially. Afterward, lubricating oil is dripped onto the inner circumference of the bearing sleeve 8, and the shaft member 2 is inserted, thereby completing the assembly of the hydrodynamic bearing assembly 1. At this time, the internal space of the outer shell 7 sealed by the sealing member 9 (including the internal cavity of the bearing sleeve 8) is filled with lubricating oil, and the oil level is maintained within the range of the sealed space S.

[0054] In the hydrodynamic bearing device 1 with the above-described structure, when the shaft member 2 rotates, a radial bearing clearance is formed between the inner circumferential surface 8a of the bearing sleeve 8 and the outer circumferential surface 2a of the shaft member 2. Furthermore, the hydrodynamic pressure generating portions 20 (20A, 20B) formed on the inner circumferential surface 8a of the bearing sleeve 8 generate hydrodynamic pressure on the lubricating oil in the radial bearing clearance. Specifically, the lubricating oil in the radial bearing clearance collects along the hydrodynamic grooves 11a, 11b at the axial central side of each hydrodynamic pressure generating portion 20 (20A, 20B), increasing the fluid pressure in this portion. This constitutes a radial bearing portion R (R1, R1) that provides non-contact support to the shaft member 2 in the radial direction. Additionally, the protrusion 2b at the lower end of the shaft member 2 contacts and slides against the thrust bearing member 10, thereby constituting a thrust bearing portion T that supports the shaft member 2 in the thrust direction.

[0055] In the hydrodynamic bearing of the present invention, a stepped portion is formed between the inclined grooves (hydrodynamic grooves) 11a and 11b in each hydrodynamic groove group 20A, 20B and the annular mound 11e. Pressure (hydrodynamic pressure) is generated at this step. In addition, pressure (hydrodynamic pressure) is generated downstream of the recess 11e1 in the rotational direction of the annular mound 11e. Therefore, the pressure (hydrodynamic pressure) generated on the annular mound 11e is increased, and the load capacity is improved. That is, the load capacity is increased, so the function of the bearing can be fully utilized even if miniaturization is sought. In other words, a bearing that increases the load capacity can be provided without increasing the axial dimension. Moreover, in motors using this hydrodynamic bearing, it is not necessary to change the groove specifications according to the center of gravity position of the rotor, etc., and there is no concern about compromising the versatility of the bearing.

[0056] Furthermore, by providing a recess 11e1 at the full confluence of the annular mound 11e and the inclined mounds 11c and 11d in the U, the load capacity can be further increased. Moreover, by making the circumferential width of the recess 11e1 smaller than the circumferential width of the confluence U, the recess 11e1 can be set to be larger within a dimension that does not connect with the contours of the annular mound 11e and the inclined mounds 11c and 11d, thereby further increasing the load capacity.

[0057] Furthermore, according to the hydrodynamic bearing device of the present invention, a hydrodynamic bearing capable of increasing load capacity is used, so that even if the axial dimension of the bearing is reduced to a thinner profile, the load applied to the bearing can still be supported.

[0058] The motor involved in this invention can fully support the load applied to the bearing even if the size of the impeller 4 is increased, thereby improving the cooling performance.

[0059] The embodiments of the present invention have been described above, but the present invention is not limited to the described embodiments and various modifications can be made. The described embodiments show a case where the sintered oil-impregnated bearing 8 is fixed and the shaft member 2 rotates, but it is not limited to this. It is also possible to adopt a structure in which the shaft member 2 is fixed and the sintered oil-impregnated bearing 8 rotates, or a structure in which both the shaft member 2 and the sintered oil-impregnated bearing 8 rotate.

[0060] The hydrodynamic bearing device assembled with the sintered oil-impregnated bearing 8 of the present invention is not limited to the spindle motor used in the disk drive device of HDD, but can also be widely used in other small motors such as spindle motors assembled in other information devices, polygon scanner motors of laser beam printers, color wheels of projectors, or cooling fan motors.

[0061] In this embodiment, a pair of dynamic pressure generating units 20A and 20B are provided, but a single dynamic pressure generating unit 20 may also be provided. Furthermore, the inclination angles θa and θb of each dynamic pressure groove 11a and 11b are not limited to the angles in this embodiment; the number, spacing, and width of each dynamic pressure groove 11a and 11b can be arbitrarily set, and the depth of the dynamic pressure groove can also be varied as needed. In this embodiment, the depth of the dynamic pressure groove (inclined groove) is set to be the same as the depth of the recess 11e1 provided in the annular mound 11e, but they can also be set differently. It should be noted that by setting the depth to be the same, productivity can be improved.

[0062] In this embodiment, when the axial lengths (width dimensions) of the first dynamic pressure groove group 11A and the second dynamic pressure groove group 11B are set to A and B, and the axial lengths (width dimensions) of the annular mounds 11e and 11e are set to C, A=B>C. However, A=B<C, A=B=C, or A≠B are also possible. Furthermore, the shape of the recess 11e1 is rectangular in this embodiment, but it can also be square, or a polygonal shape with pentagonal or larger features, etc.

[0063] Furthermore, the bearing sleeve 8 is a cylindrical body with a porous structure, which may be formed from sintered metal as in the embodiment, but it can also be formed from a porous body made of non-metallic materials such as resin or ceramic. In addition to porous bodies, it can also be formed from a structure that does not have internal pores or has pores of a size that prevents lubricating oil from entering or leaving.

[0064] Example 1

[0065] Using a bearing (Example 1) with the specifications shown in Table 1, the pressure distribution on the outer diameter surface of the shaft component and the force applied to the outer diameter surface of the shaft component were calculated using the thermal fluid analysis software (STAR-CCM+ manufactured by SIEMENS). STAR-CCM+ is a comprehensive CAE software for complex region problems. Centered on fluid analysis functions based on the finite volume method, it also includes structural analysis functions based on the finite element method and particle analysis based on the DEM method, in addition to fluid-related physical functions. STAR-CCM+ utilizes a single package to realize everything from CAD-based shape creation to evaluation of calculation results, and can easily automate the workflow. The simulation setup workflow, calculation execution, and result evaluation are integrated into a single GUI, and the necessary automation functions are complete. STAR-CCM+ can analyze a wide variety of phenomena through rich physical models and functions. In addition to basic functions such as 2D / 3D, laminar / turbulent / inviscid, compressible / incompressible, buoyancy, movement / rotation, and porous regions, it also includes various turbulence models used in fluid analysis.

[0066] In this case, in order to shorten the analysis time, such as Figure 5 The dynamic pressure generating unit 20 is arranged in one row as shown. Furthermore, the bearing specifications of embodiment 1 are shown in Table 1. A shaft with an outer diameter (diameter) of 1.99 mm was used as the shaft (shaft member 2).

[0067]

[0068] The bearing's inner diameter is set to 2 mm, its width (axial length) to 1.80 mm, its groove depth to 10 μm, its hump-to-groove ratio to 1, its groove angles (θa, θb) to 20 degrees, its inclined groove width (axial length A of the dynamic pressure groove groups 11A and 11B) to 0.7 mm, its annular hump width (axial length C of the annular hump 11e) to 0.4 mm, its radial clearance to 10 μm, and its eccentricity to 0. Here, when the circumferential length of the hump is set to H2 and the circumferential length of the groove to H1, the hump-to-groove ratio is H2 / H1.

[0069] In this case, such as product 1 Figure 5 As shown, the following product was designated as Embodiment 1: the axial length (width dimension) H of the recess 11e1 was set to 0.4 mm, the circumferential length L1 of the recess 11e1 was set to 0.32 mm, and the recess 11e1 was positioned without offset from the confluence portion U. Calculations were performed on two comparative products 1 and 2, which differed in the position and size of the recess 11e1, as well as a conventional product without a recess. In comparative product 1, the circumferential length of the mound was set to half that of Embodiment 1. In comparative product 2, the axial length of the mound was set to be approximately 0.1 mm smaller than that of Embodiment 1, and the mound was offset approximately 0.22 mm in the direction of rotation. It should be noted that the rotational speed of the shaft member 2 was set to 5500 rpm.

[0070] Figures 6A-6B Example 1 is shown. Figure 6A This is the tank specification diagram. Figure 6B It is a pressure distribution diagram. Figures 7A-7B Comparative sample 1 is shown. Figure 7A This is the tank specification diagram. Figure 7B It is a pressure distribution diagram. Figures 8A-8B Comparison sample 2 is shown. Figure 8A This is the tank specification diagram. Figure 8B It is a pressure distribution diagram. Figures 9A-9B Showing previous product 1, Figure 9A This is the tank specification diagram. Figure 9B This is a pressure distribution diagram.

[0071] As can be seen from the pressure distribution diagrams, in Embodiment 1, Comparative Example 1, and Comparative Example 2, which are provided with the recess 11e1, an increase in pressure was observed on the downstream side of the groove in the direction of rotation. That is, regarding the pressure applied to the outer diameter surface of the shaft member, it is 0.0049 N in Embodiment 1, 0.0042 N in Comparative Example 1, 0.0042 N in Comparative Example 2, and 0.0039 N in Conventional Example 1. In this case, Embodiment 1 has the highest pressure, which is 1.3 times that of the Conventional Example.

[0072] Example 2

[0073] Next, a functional evaluation was conducted using embodiment 2 with the bearing specifications shown in Table 2. A shaft with an outer diameter (diameter) of 1.99 mm was used as the shaft (shaft member 2).

[0074]

[0075] Set the inner diameter (diameter) of the bearing (bearing sleeve 8) to 2mm, the width (axial length of the bearing) to 2.35mm, the groove depth to 3μm, the hill-to-groove ratio to 1, the groove angles (θ1, θ2) to 20deg, the width of the inclined groove (axial length of the bearing in the dynamic pressure groove) to 0.25mm, the width of the annular hill (axial length of the bearing in the annular hill 11e) to 0.2mm, and the radial clearance to 8μm.

[0076] In this case, as Embodiment 2, three embodiments, No. 1 to No. 3, are produced; and as Prior Artifact 2, three Prior Artifacts, No. 1 to No. 3, are produced. Embodiments 2, No. 1 to No. 3, respectively used... Figure 10 The dynamic pressure bearing is as shown. The axial length (width dimension) of the recess 11e1 is set to 0.2 mm, the circumferential length of the recess 11e1 is set to 0.25 mm, the recess 11e1 is positioned without offset from the confluence portion U, the dimension from the outer axial edge of the annular mound 11e of one dynamic pressure generating portion 20A to the other end face of the bearing (bearing sleeve 8) is set to L2 and is 1.9 mm, and the dimension from the outer axial edge of the annular mound of the other dynamic pressure generating portion 20B to the other end face of the bearing is set to L3 and is 0.45 mm. In this case, Embodiments 2 No.1 to No.3 are identical in design.

[0077] In addition, as for the previous No.1~No.3 of product 2, such as Figure 11 As shown, for in Figure 10 The hydrodynamic bearing shown does not have a recess. In this case, the design of conventional products No.1 to No.3 of product 2 is the same.

[0078] Should Figure 11The illustrated hydrodynamic bearing has a pair of hydrodynamic generating portions 120 (120A, 120B) axially separated on the inner circumferential surface 108a of the bearing sleeve 108, which serves as the radial bearing surface. Each hydrodynamic generating portion 120A, 120B has multiple hydrodynamic grooves 111a, 111b arranged in a herringbone shape. The hydrodynamic grooves 111a, 111a on the outer axial sides of the hydrodynamic generating portions 120A, 120B form a first hydrodynamic groove group 111A, 111A, and the hydrodynamic grooves 111b, 111b on the inner axial sides of the hydrodynamic generating portions 120 form a second hydrodynamic groove group 111B, 111B. It should be noted that the pair of hydrodynamic generating portions 120A, 120B are designed to be flipped vertically.

[0079] Furthermore, in each dynamic pressure generating section 120A, 120B, the axially outer dynamic pressure grooves 111a, 111a and the axially inner dynamic pressure grooves 111b, 111b have different inclination directions. Inclined mounds 111c, 111d are respectively provided between the dynamic pressure grooves 111a, 111b. The inclined mounds 11c, 11d and the annular mounds 11e, 11e are shown with cross-sectional lines.

[0080] The functional evaluation results are shown in Table 3 below. In Table 3, the shaft (shaft member 2) was rotated at a speed of 100~1000 rpm for 60 seconds under a load of 0.1N (compressive load) applied to it. The presence or absence of contact between the rotating shaft member 2 and the bearing (bearing sleeve 8) was determined. This determination was performed using a known and commonly used electrical contact method.

[0081]

[0082] For the previous products (No. 1 to No. 3), it was found that contact between the shaft component and the bearing occurred from 1000 rpm, and the number of contacts increased sharply below 200 rpm. In contrast, for the prototype 2 (No. 1 to No. 3), almost no contact was observed up to 200 rpm, and the number of contacts at 100 rpm was also less than that of the comparative examples. It should be noted that the values ​​in Table 3 represent the number of contacts, with the larger value indicating a higher number of contacts. In addition, in Table 3, ">500" indicates that the shaft component contacted the bearing more than 500 times in 60 seconds.

[0083] The presence or absence of contact between the shaft (shaft member 2) and the bearing (bearing sleeve 8) was measured as the load applied to the shaft (shaft member 2) was gradually increased. In this case, both the hydrodynamic bearings of Embodiment 2 (No. 1 to No. 3) and the hydrodynamic bearings of Conventional Component 2 (No. 1 to No. 3) were used. The presence or absence of contact between the shaft (shaft member 2) and the bearing (bearing sleeve 8) was measured as the rotational speed was set to 1000 rpm and the load applied to the shaft member was gradually increased, and the results are shown in Table 4. The measurement was also performed using the known and commonly used electrical contact method. It should be noted that in Table 4, "-" indicates that no measurement was performed under that load. This is because the number of contacts exceeded 500 under the load preceding this load, and therefore the number of contacts exceeded 500 under subsequent loads.

[0084]

[0085] As shown in Table 4, the load at which frequent contact between the shaft component and the bearing is observed is 1.27 N in the conventional product, while it is 1.57 N (1.2 times) in the prototype. Therefore, it can be confirmed that the hydrodynamic bearing of prototype 2 has a higher load capacity compared to the conventional product 2.

[0086] Industrial availability

[0087] Hydrodynamic bearing devices assembled with sintered oil-impregnated bearings can also be widely used in information equipment such as spindle motors, polygon scanner motors for laser beam printers, color wheels for projectors, or cooling fan motors and other small motors.

[0088] Explanation of reference numerals in the attached figures

[0089] 1. Hydrodynamic bearing assembly

[0090] 2-axis components

[0091] 3 rotors

[0092] 4 Impeller

[0093] 5. Outer shell

[0094] 8. Sintered oil-impregnated bearings (bearing sleeves)

[0095] 8a Inner circumferential surface

[0096] 11A and 11B dynamic pressure tank groups

[0097] 11a, 11b dynamic pressure grooves

[0098] 11c Sloping hill

[0099] 11e Ring-shaped mounds

[0100] 11e1 concavity

[0101] 20 (20A, 20B) Dynamic pressure generating unit

[0102] C Convergence

[0103] R1 Radial bearing section.

Claims

1. A hydrodynamic bearing having an inner diameter surface facing the outer diameter surface of a shaft member, and having a hydrodynamic pressure generating portion on the inner diameter surface, characterized in that... The dynamic pressure generating part has a plurality of dynamic pressure grooves arranged in a herringbone shape. The dynamic pressure grooves are provided with a first dynamic pressure groove group and a second dynamic pressure groove group. Inclined mounds are formed between the dynamic pressure grooves of the first dynamic pressure groove group and the second dynamic pressure groove group. An annular mound is provided between the first dynamic pressure groove group and the second dynamic pressure groove group, which is connected to each inclined mound and extends circumferentially. A recess for generating dynamic pressure is formed in a part of the annular mound.

2. The hydrodynamic bearing according to claim 1, characterized in that, The circumferential width of the recess is smaller than the circumferential width of the confluence. The number of dynamic pressure grooves in the first dynamic pressure groove group and the second dynamic pressure groove group are set to be the same. The confluence of the inclined mound and the annular mound of the first dynamic pressure group and the confluence of the inclined mound and the annular mound of the second dynamic pressure group are the same, and the recess is provided in all confluences.

3. The hydrodynamic bearing according to claim 1, characterized in that, A pair of dynamic pressure generating parts with an up-and-down flipping shape that are separated in the axial direction are formed on the inner diameter surface of the bearing.

4. A hydrodynamic bearing device, characterized in that, The hydrodynamic bearing device comprises a hydrodynamic bearing as described in any one of claims 1 to 3, a shaft member inserted into the inner circumference of the hydrodynamic bearing, and a radial bearing portion that supports the relative rotation of the shaft member by the hydrodynamic force of a lubricating fluid in a radial bearing clearance formed between the inner circumferential surface of the hydrodynamic bearing and the outer circumferential surface of the shaft member.

5. A motor, characterized in that, The motor comprises the hydrodynamic bearing device as described in claim 4, a rotor that rotates integrally with the shaft member or the hydrodynamic bearing, and a drive unit that drives the rotor to rotate, the rotor having an impeller portion.

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