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

Abstract

To provide a dynamic pressure bearing that can improve load capacity without enlarging an axial dimension and impairing versatility, and to provide a fluid dynamic pressure bearing device and a motor.SOLUTION: A dynamic pressure bearing includes: a bearing inner diameter surface opposite to an outer diameter surface of a shaft member; and a dynamic pressure generation part in the bearing inner diameter surface. The dynamic pressure generation part has a plurality of dynamic pressure grooves arranged in a herringbone pattern, and the dynamic pressure grooves include first and second groups of dynamic pressure grooves. An annular ridge part extending in the circumferential direction is provided between the first and second groups of dynamic pressure grooves. A recess for generating dynamic pressure is formed in a partial area of the annular ridge part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a hydrodynamic bearing, a hydrodynamic bearing device, and a motor.

Background Art

[0002] A hydrodynamic bearing device non - contact - supports a shaft member so as to be relatively rotatable by the pressure generated in a fluid film (for example, an oil film) in a radial bearing gap between the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing member. Due to its high rotational accuracy and quietness, a hydrodynamic bearing device is preferably used for small motors such as a spindle motor of an information device (for example, a magnetic disk drive device such as an HDD, an optical disk drive device such as a CD - ROM, CD - R / RW, DVD - ROM / RAM, Blu - ray disk, a magneto - optical disk drive device such as an MD, MO), a polygon scanner motor of a laser beam printer (LBP), a color wheel of a projector, or a fan motor such as a cooling fan of an electric device.

[0003] Portable information devices (so - called mobile devices) such as notebook personal computers and tablet - type terminals have strong requirements for thinning. In recent years, for information devices to support 5G (fifth - generation mobile communication system), the functionality has been enhanced, and the heat generation amount from the circuit has increased. Therefore, the requirements for cooling performance have also increased, and the impeller attached to the rotating shaft tends to become larger. For this reason, the load applied to the hydrodynamic bearing device that supports the rotating shaft of the fan motor becomes larger. Here, 5G (fifth - generation mobile communication system) is the "fifth - generation mobile communication system", and its main features are "high - speed large - capacity", "multiple simultaneous connections", and "ultra - low latency".

[0004] As a hydrodynamic bearing corresponding to a thin - type fan motor, conventionally, the one described in Patent Document 1 is known. The hydrodynamic bearing described in this Patent Document 1 attempts to increase the bearing rigidity against moment loads and suppress the run - around of the shaft without expanding the axial dimension. In this case, two rows of hydrodynamic generation portions with different groove (hydrodynamic groove) specifications are arranged in the axial direction.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the case of a motor using a hydrodynamic bearing, depending on the position of the center of gravity of the rotor to be configured, etc., it is necessary to change the groove specifications, which results in inferior versatility and high costs. Further, in this case, since the upper and lower groove specifications are different, when there are motors with the same motor specifications but different rotation directions, it is not possible to handle them even when turned upside down.

[0007] Therefore, in view of the above problems, the present invention provides a hydrodynamic bearing, a hydrodynamic bearing device, and a motor capable of improving the load capacity without increasing the axial dimension and without sacrificing versatility.

Means for Solving the Problems

[0008] The hydrodynamic bearing of the present invention is a hydrodynamic bearing having a bearing inner diameter surface facing the outer diameter surface of a shaft member, and provided with a hydrodynamic generation portion on the bearing inner diameter surface, wherein the hydrodynamic generation portion has a plurality of hydrodynamic grooves arranged in a herringbone shape, the hydrodynamic grooves are provided with first and second hydrodynamic groove groups spaced apart along the axial direction, and inclined inclined hill portions are formed between the hydrodynamic grooves of the first and second hydrodynamic groove groups, respectively, and an annular hill portion extending in the circumferential direction and connected to each inclined hill portion is provided between the first hydrodynamic groove group and the second hydrodynamic groove group, and a concave portion for generating hydrodynamic pressure is formed in a part of the annular hill portion.

[0009] According to the hydrodynamic bearing of the present invention, a stepped portion is formed between the inclined grooves (hydrodynamic grooves) and the annular mound portion in each hydrodynamic groove group, and pressure (hydrodynamic pressure) is generated by this step, and due to the concave portion of the annular mound portion, pressure (hydrodynamic pressure) is generated on the downstream side in the rotation direction in the concave portion. That is, a concave portion for generating pressure by the wedge effect is provided in the annular mound portion, and the load capacity is improved.

[0010] The concave portion for generating the hydrodynamic pressure is provided at the confluence of the annular mound portion and the inclined mound portion, the circumferential width of the concave portion is made smaller than the circumferential width of the confluence portion, and the number of hydrodynamic grooves in the first and second hydrodynamic groove groups is made the same. At the same time, the confluence of the inclined mound portion and the annular mound portion in the first hydrodynamic group coincides with the confluence of the inclined mound portion and the annular mound portion in the second hydrodynamic group, and it is preferable that the concave portion is provided at all the confluence portions.

[0011] Since the concave portion is provided at all the confluence portions of the annular mound portion and the inclined mound portion, the load capacity can be further increased. Furthermore, by making the circumferential width of the concave portion smaller than the circumferential width of the confluence portion, the concave portion can be set larger within the dimension not in contact with the contours of the annular mound portion and the inclined mound portion, and the load capacity can be further increased.

[0012] A pair of hydrodynamic generation portions having an upside-down shape spaced apart in the axial direction may be formed on the inner diameter surface of the bearing. By configuring in this way, it is possible to cope with motors having the same motor specifications and differing only in the rotation direction by turning them upside down.

[0013] 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 action of the lubricating fluid in the radial bearing gap formed between the inner circumferential surface of the hydrodynamic bearing and the outer circumferential surface of the shaft member.

[0014] According to the hydrodynamic bearing device of the present invention, since a hydrodynamic bearing capable of improving the load capacity is used, even if the axial dimension of the bearing is reduced to be thin, it is possible to support the load applied to the bearing.

[0015] The motor according to the present invention includes the fluid dynamic pressure bearing device, a rotor that rotates integrally with the shaft member or the dynamic pressure bearing, and a drive unit that rotationally drives the rotor, and the rotor has an impeller portion.

[0016] Even if the size of the impeller is increased, the load applied to the bearing can be sufficiently supported, and the cooling performance can be improved.

Advantages of the Invention

[0017] In the present invention, since the load capacity is improved, the function of the bearing can be sufficiently exhibited even if miniaturization is achieved. That is, a bearing that improves the load capacity can be provided without expanding the axial dimension. Moreover, in the motor using this dynamic pressure bearing, it is not necessary to change the groove specifications depending on the center of gravity position of the rotor constituting the motor, etc., and there is no risk of impairing the versatility as a bearing.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 shows a hydrodynamic bearing according to this embodiment, FIG. 2 shows an enlarged schematic view of a main part of the hydrodynamic bearing, FIG. 3 shows a fluid dynamic bearing device using the hydrodynamic bearing according to the present invention, and FIG. 4 shows a fan motor for cooling using this fluid dynamic bearing device. This fan motor is incorporated into, for example, information devices, particularly mobile devices such as mobile phones and tablet terminals.

[0020] This fan motor includes a fluid dynamic bearing device 1 according to an embodiment of the present invention, a rotor 3 attached to a shaft member 2 of the fluid dynamic bearing device 1, an impeller (blade) 4 attached to the outer diameter end of the rotor 3, a stator coil 6a and a rotor magnet 6b opposed through a radial gap, and a casing 5 that houses them. The stator coil 6a is attached to the outer periphery of the hydrodynamic bearing device 1, and the rotor magnet 6b is attached to the inner periphery of the rotor 3. By energizing the stator coil 6a, the rotor 3, the impeller 4, and the shaft member 2 rotate integrally, thereby generating an air flow in the axial direction or the outer diameter direction.

[0021] As shown in FIG. 3, the fluid dynamic bearing device 1 includes a shaft member 2, a housing 7, a bearing sleeve 8 as a hydrodynamic bearing according to the present invention, a seal member 9, and a thrust bearing 10. In the following, in the axial direction (the vertical direction in FIG. 2), the opening side of the housing 7 is referred to as the upper side, and the bottom 7b side of the housing 7 is referred to as the lower side.

[0022] The shaft member 2 is formed in a cylindrical shape from a metal material such as stainless steel. The shaft member 2 has an outer peripheral surface 2a in a cylindrical surface shape and a spherical convex portion 2b provided at the lower end.

[0023] The housing 7 has a substantially cylindrical side portion 7a and a bottom portion 7b that closes the opening below the side portion 7a. In the illustrated example, the side portion 7a and the bottom portion 7b are integrally injection-molded of resin. The casing 5 and the stator coil 6a are fixed to the outer peripheral surface 7a2 of the side portion 7a. A bearing sleeve 8 is fixed to the inner peripheral surface 7a1 of the side portion 7a. On the outer diameter end of the upper end surface 7b1 of the bottom portion 7b, a shoulder surface 7b2 located above the inner diameter portion is provided, and the lower end surface 8c of the bearing sleeve 8 abuts against this shoulder surface 7b2. A circumferential notch 7b4 is formed in the outer peripheral surface 7a2 of the side portion 7a, and the stator coil 6a is fitted into this circumferential notch 7b4. A resin thrust receiver 10 is arranged at the center of the upper end surface 7b1 of the bottom portion 7b. Instead of (or in addition to) providing the radial groove 7b3 on the shoulder surface 7b2 of the housing 7, a radial groove may be formed on the lower end surface 8c of the bearing sleeve 8.

[0024] The bearing sleeve 8 has a cylindrical shape and is fixed to the inner peripheral surface 7a1 of the side portion 7a of the housing 7 by appropriate means such as gap adhesion, press-fitting, press-fitting adhesion (press-fitting with an adhesive in between), etc. In this embodiment, the bearing sleeve 8 can be made of a sintered metal processed by pressing, a melted material such as brass or stainless steel processed by cutting, or further a resin processed by injection molding.

[0025] On the inner peripheral surface 8a of the bearing sleeve 8 that serves as a radial bearing surface, a pair of hydrodynamic generation portions 20 (20A, 20B) are provided at intervals in the axial direction. Each of the hydrodynamic generation portions 20A, 20B has a plurality of hydrodynamic grooves 11a, 11b arranged in a helical bone shape. The hydrodynamic grooves 11a, 11a on the axially outer side of the hydrodynamic generation portions 20A, 20B form the first hydrodynamic groove groups 11A, 11A, and the hydrodynamic grooves 11b, 11b on the axially inner side of the hydrodynamic generation portion 20 form the second hydrodynamic groove groups 11B, 11B. Note that the pair of hydrodynamic generation portions 20A, 20B have an upside-down shape.

[0026] Further, in each of the dynamic pressure generating portions 20A and 20B, the dynamic pressure grooves 11a, 11a on the outer side in the axial direction and the dynamic pressure grooves 11b, 11b on the inner side in the axial direction have different inclination directions. In the illustrated example, the dynamic pressure grooves 11a, 11a on the outer side in the axial direction incline from the outer side in the axial direction to the inner side in the axial direction along the rotation direction of the shaft member 2, and the dynamic pressure grooves 11b, 11b on the inner side in the axial direction incline from the inner side in the axial direction to the outer side in the axial direction along the rotation direction of the shaft member 2. The bottom surfaces of the dynamic pressure grooves 11a and 11b are provided on the same cylindrical surface. The bottom surface of the dynamic pressure groove 11b on the inner side in the axial direction is continuous with the cylindrical surface 13 provided between the axial directions of the two dynamic pressure generating portions 20 (20A, 20B).

[0027] Inclined mound portions 11c and 11d are respectively provided between the dynamic pressure grooves 11a and 11b. Also, in each of the dynamic pressure generating portions 20 (20A, 20B), annular mound portions 11e, 11e are provided between the first dynamic pressure groove group 11A and the second dynamic pressure groove group 11B. The inclined mound portions 11c, 11d and the annular mound portions 11e, 11e are indicated by cross-hatching. The annular mound portions 11e, 11e and the inclined mound portions 11c, 11d rise from the bottom surfaces of the dynamic pressure grooves 11a, 11b toward the inner diameter side. The inner diameter surfaces of the annular mound portions 11e, 11e and the inclined mound portions 11c, 11d are provided on the same cylindrical surface. The annular mound portions 11e, 11e and all the inclined mound portions 11c, 11d are continuously provided respectively.

[0028] Incidentally, when the axial lengths (width dimensions) of the first dynamic pressure groove group 11A and the second dynamic pressure groove group 11B are A and B, respectively, and the axial length (width dimension) of the annular mound portions 11e, 11e is C, A = B > C. Also, in each of the first dynamic pressure generating portion 20A and the second dynamic pressure generating portion 20B, the inclination angle θa (see FIG. 2) of the dynamic pressure grooves 11a, 11a of the first dynamic pressure groove group 11A, 11A with respect to the circumferential direction is made equal to the inclination angle θb (see FIG. 2) of the dynamic pressure grooves 11b, 11b of the second dynamic pressure groove group 11B, 11B with respect to the circumferential direction.

[0029] The annular ridge portion 11e is provided with recesses 11e1 respectively. In this case, the recesses 11e1 are formed at the confluence U of the inclined ridge portions 11c and 11d and the annular ridge portion 11e. In the illustrated example, the recesses 11e1 are configured in a rectangular shape, and as the depth dimension, it is the same as the height dimension of the annular ridge portion 11e That is, the bottom surface of the recess 11e1 coincides with the cylindrical surface 13. Also, the width dimension (axial length) of the recess 11e1 is made approximately the same as the width dimension (axial length) of the annular ridge portion 11e. In this case, as the circumferential length of the recess 11e1, it is a dimension that does not expose from the confluence U. That is, when the circumferential length of the confluence U is L and the circumferential length of the recess 11e1 is L1, L > L1. Also, when the axial length of the confluence U is H and the axial bearing direction length of the recess 11e1 is H1, H ≥ H1.

[0030] Incidentally, the bearing sleeve 8 is specifically formed of a sintered metal, for example, a sintered metal containing 35 wt.% or more of copper, particularly, a sintered metal containing 35 wt.% or more of each of copper and iron. The bearing sleeve 8 is manufactured by the following method. First, raw material powder is compression molded to form a green compact (green compacting process). The raw material powder includes either or both of a copper-based powder (copper powder or copper alloy powder) and an iron-based powder (iron powder or iron alloy powder) as the main component metal powder. The raw material powder may include a high-hardness powder such as stainless steel powder. The raw material powder of the present embodiment includes pure iron powder and pure copper powder as the main component metal powder. The raw material powder may include, in addition to the main component metal powder, a low-melting-point metal powder such as tin powder, a carbon powder such as graphite powder, or a lubricant for molding. By sintering this green compact at a predetermined sintering temperature, a sintered body is obtained (sintering process). By sizing this sintered body, dynamic pressure grooves 11, 11 are formed on the inner peripheral surface (sizing process). In the present embodiment, a hole closing treatment such as rotary sizing is performed on the inner peripheral surface of the sintered body. By impregnating the internal pores of this sintered body with lubricating oil, the bearing sleeve 8 is completed.

[0031] The bearing sleeve 8 has a density ratio of 80 to 95%. In the bearing sleeve 8, communication pores that communicate the inside and the surface are formed. Specifically, communication pores are formed to such an extent that the oil content rate is 4% or more. That is, the molding conditions of the bearing sleeve 8 (for example, the compression ratio in the powder compacting process and the sizing process, etc.) are set so that communication pores are formed to such an extent that the oil content rate is 4% or more. The bearing sleeve 8 is sized so that the surface opening ratio on the inner peripheral surface 8a (radial bearing surface) is equal to or less than the value of the porosity (= 100% - density ratio) of the bearing sleeve 8. Specifically, it is 10% or less, preferably 8% or less, more preferably 5% or less. Thus, by setting the opening ratio to 10% or less, the dynamic pressure leakage from the inner diameter surface 8a can be effectively prevented.

[0032] Note that an axial groove 8d1 is formed on the outer peripheral surface of the bearing sleeve 8. The number of the axial grooves 8d1 is arbitrary, and for example, they are formed at three equally spaced positions in the circumferential direction.

[0033] The seal member 9 is formed in a ring shape from resin or metal and is fixed to the upper end portion of the inner peripheral surface 7a1 of the side portion 7a of the housing 7. The seal member 9 is in contact with the upper end surface 8b of the bearing sleeve 8. The inner peripheral surface 9a of the seal member 9 faces the outer peripheral surface 2a of the shaft member 2 in the radial direction, and a seal space S is formed therebetween. When the shaft member 2 rotates, the seal space S prevents the lubricating oil inside the bearing from leaking to the outside. A radial groove 9b1 is formed on the lower end surface 9b of the seal member 9. Instead of (or in addition to) forming the radial groove 9b1 on the lower end surface 9b of the seal member 9, a radial groove may be formed on the upper end surface 8b of the bearing sleeve 8.

[0034] The above-described hydrodynamic bearing device 1 is assembled in the following procedure. First, the thrust receiver 10 is fixed to the upper end face 7b1 of the bottom 7b of the housing 7. Then, a bearing sleeve 8 impregnated with lubricating oil in internal pores in advance is inserted into the inner circumference of the side portion 7a of the housing 7, and with the lower end face 8c of the bearing sleeve 8 abutted against the shoulder face 7b2 of the bottom 7b, the outer peripheral surface 8d of the bearing sleeve 8 is fixed to the inner peripheral surface 7a1 of the side portion 7a. Thereafter, the seal member 9 is fixed to the upper end of the inner peripheral surface 7a1 of the side portion 7a of the housing 7. At this time, the seal member 9 is press-fitted into the side portion 7a of the housing 7, and the bearing sleeve 8 is clamped from both axial sides by the seal member 9 and the shoulder face 7b2 of the bottom 7b of the housing 7, whereby the bearing sleeve 8 can be axially restrained. Thereafter, lubricating oil is dripped into the inner circumference of the bearing sleeve 8, and by inserting the shaft member 2, the assembly of the hydrodynamic bearing device 1 is completed. At this time, the internal space of the housing 7 (including the internal hole of the bearing sleeve 8) sealed by the seal member 9 is filled with lubricating oil, and the oil level is maintained within the range of the seal space S.

[0035] In the hydrodynamic bearing device 1 having the above configuration, when the shaft member 2 rotates, a radial bearing clearance is formed between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a of the shaft member 2. Then, the hydrodynamic generating portions 20 (20A, 20B) formed on the inner peripheral surface 8a of the bearing sleeve 8 generate a hydrodynamic action on the lubricating oil in the radial bearing clearance. Specifically, the lubricating oil in the radial bearing clearance is collected along the hydrodynamic grooves 11a, 11b toward the axially central side of each hydrodynamic generating portion 20 (20A, 20B), and the fluid pressure in this portion is increased. Thereby, a radial bearing portion R (R1, R1) that non-contactly supports the shaft member 2 in the radial direction is configured. Further, a thrust bearing portion T that supports the shaft member 2 in the thrust direction is configured by the contact and sliding between the convex portion 2b at the lower end of the shaft member 2 and the thrust receiver 10.

[0036] In the hydrodynamic bearing of the present invention, a step portion is formed between the inclined grooves (hydrodynamic grooves) 11a and 11b and the annular mound portion 11e in each of the hydrodynamic groove groups 20A and 20B, and pressure (hydrodynamic pressure) is generated by this step, and due to the concave portion 11e1 of the annular mound portion 11e, pressure (hydrodynamic pressure) is generated on the downstream side in the rotational direction in the concave portion 11e1. For this reason, the pressure (hydrodynamic pressure) generated on the annular mound portion 11e becomes high, and the load capacity is improved. That is, since the load capacity is improved, even if miniaturization is achieved, the function of the bearing can be sufficiently exhibited. That is, a bearing that can improve the load capacity without expanding the axial dimension can be provided. Moreover, in a motor using this hydrodynamic bearing, it is not necessary to change the groove specifications depending on the position of the center of gravity of the rotor that constitutes it, and there is no risk of impairing the versatility as a bearing.

[0037] Further, by providing the concave portion 11e1 at the entire confluence portion U of the annular mound portion 11e and the inclined mound portions 11c and 11d, the load capacity can be further increased. Furthermore, by making the circumferential width of the concave portion 11e1 smaller than the circumferential width of the confluence portion U, the concave portion 11e1 can be set larger within a dimension that does not contact the contours of the annular mound portion 11e and the inclined mound portions 11c and 11d, and the load capacity can be further increased.

[0038] Moreover, according to the fluid dynamic pressure bearing device according to the present invention, since a hydrodynamic bearing capable of improving the load capacity is used, even if the axial dimension of the bearing is made small for thinning, it is possible to support the load applied to the bearing.

[0039] The motor according to the present invention can sufficiently support the load applied to the bearing even if the size of the impeller 4 is increased, and the cooling performance can be improved.

[0040] As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above embodiments. Various modifications are possible. In the above embodiment, the case where the sintered oil-impregnated bearing 8 is fixed and the shaft member 2 rotates has been shown. However, the present invention is not limited to this, and a configuration in which the shaft member 2 is fixed and the sintered oil-impregnated bearing 8 is rotated, or a configuration in which both the shaft member 2 and the sintered oil-impregnated bearing 8 are rotated can also be adopted.

[0041] The hydrodynamic bearing device incorporating the sintered oil-impregnated bearing 8 according to the present invention is not limited to the spindle motor used in the disk drive device of the HDD, but can also be widely used in other small motors such as spindle motors incorporated in other information devices, polygon scanner motors of laser beam printers, color wheels of projectors, or fan motors for cooling.

[0042] In the embodiment, a pair of hydrodynamic pressure generating portions 20A and 20B are provided, but one hydrodynamic pressure generating portion 20 may be provided. Further, the inclination angles θa and θb of the respective hydrodynamic grooves 11a and 11b are not limited to those of the embodiment, and the number, arrangement pitch, groove width, etc. of the respective hydrodynamic grooves 11a and 11b can also be arbitrarily set. Furthermore, the depth of the hydrodynamic groove can also be variously changed as required. In the embodiment, the depth of the hydrodynamic groove (inclined groove) and the depth of the recess 11e1 provided in the annular mound portion 11e are set to be the same, but they may be different. Note that by making the depths the same, productivity can be improved.

[0043] In the embodiment, when the axial lengths (width dimensions) of the first hydrodynamic groove group 11A and the second hydrodynamic groove group 11B are A and B, and the axial lengths (width dimensions) of the annular mound portions 11e and 11e are C, A = B > C is set. However, A = B < C, A = B = C, or A ≠ B may also be possible. Further, as the shape of the recess 11e1, in the embodiment, it is a rectangular shape, but it may be a square shape, a polygon shape with five or more sides, or the like.

[0044] Incidentally, the bearing sleeve 8 is a cylindrical body having a porous structure. For example, as in the embodiment, it is formed of a sintered metal, but it can also be formed of a porous body made of a non-metallic material such as resin or ceramic. Further, in addition to the porous body, it can also be formed of a structure having no internal pores or having pores of such a size that lubricating oil cannot enter or exit.

Example

[0045] Using the bearing (Product 1) with the bearing specifications shown in Table 1, the pressure distribution on the outer diameter surface of the shaft member and the force applied to the outer diameter surface of the shaft member were calculated by thermal fluid analysis software (STAR-CCM+ manufactured by SIEMENS). STAR-CCM+ is integrated CAE software for composite region problems. With the fluid analysis function based on the finite volume method as the axis, in addition to the physical functions related to fluids, it is also equipped with a structural analysis function based on the finite element method and a particle analysis by the DEM method. STAR-CCM+ realizes from shape creation by CAD to evaluation of calculation results in one package, and can easily automate the work process. It integrates work processes such as the workflow, calculation execution, and result evaluation required for simulation settings into one GUI and has the functions necessary for automation. STAR-CCM+ can comprehensively analyze various phenomena due to its rich physical models and functions. In addition to basic functions such as 2D / 3D, laminar / turbulent / non-viscous, compressible / incompressible, buoyancy, moving / rotating, and porous regions, it is also equipped with various turbulent models used in fluid analysis.

[0046] In this case, in order to shorten the analysis time, as shown in FIG. 5, the hydrodynamic generation part 20 was made into one row. Also, the bearing specifications of Product 1 are shown in Table 1. As the shaft (shaft member 2), one with an outer diameter (diameter) of 1.99 mm was used.

Table 1

[0047] The inner diameter (diameter) of the bearing was set to 2 mm, the width (axial length of the bearing along the shaft) was set to 1.80 mm, the groove depth was set to 10 μm, the hill-groove ratio was set to 1, the groove angles (θa, θb) were set to 20 deg, the inclined groove width (axial length A of the hydrodynamic groove groups 11A, 11B) was set to 0.7 mm, the annular hill width (axial length C of the annular hill portion 11e) was set to 0.4 mm, the radial clearance was set to 10 μm, and the eccentricity was set to 0. Here, the hill-groove ratio is H2 / H1, where H2 is the circumferential length of the hill portion and H1 is the circumferential length of the groove portion.

[0048] In this case, as shown in FIG. 5 of the product 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 product 1 was arranged at a position where it did not shift to the confluence portion U. Calculations were made for two comparative products 1 and 2 with different positions and sizes of the recess 11e1, and a conventional product without a recess. Here, for comparative product 1, the circumferential length of the hill portion was set to half of that of product 1, and for comparative product 2, the axial length of the hill portion was set to be about 0.1 mm smaller than that of product 1, and the hill portion was shifted by about 0.22 mm toward the rotation direction side. Note that the rotational speed of the shaft member 2 was set to 5500 rpm.

[0049] FIG. 6 shows product 1, (a) is a groove specification diagram, (b) is a pressure distribution diagram, FIG. 7 shows comparative product 1, (a) is a groove specification diagram, (b) is a pressure distribution diagram, FIG. 8 shows comparative product 2, (a) is a groove specification diagram, (b) is a pressure distribution diagram, FIG. 11 shows conventional product 1, (a) is a groove specification diagram, (b) is a pressure distribution diagram.

[0050] As can be seen from each pressure distribution diagram, in product 1, comparative product 1, and comparative product 2 provided with the recess 11e1, a pressure increase was observed on the downstream side in the rotation direction of the groove. That is, the pressure applied to the outer diameter surface of the shaft member was 0.0049 N in Example 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, Example 1 was the highest, being 1.3 times that of the conventional example.

Example

[0051] Next, using the implementation product 2 of the bearing specifications shown in Table 2, a function evaluation was carried out. As the shaft (shaft member 2), one with an outer diameter (diameter) of 1.99 mm was used.

Table 2

[0052] The inner diameter (diameter) of the bearing (bearing sleeve 8) was set to 2 mm, the width (axial length of the bearing shaft) was set to 2.35 mm, the groove depth was set to 3 μm, the hill-groove ratio was set to 1, the groove angles (θ1, θ2) were set to 20 deg, the inclined groove width (axial length of the dynamic pressure groove in the bearing shaft direction) was set to 0.25 mm, the annular hill portion width (axial length of the annular hill portion 11e in the bearing shaft direction) was set to 0.2 mm, and the radial clearance was set to 8 μm.

[0053] In this case, as the implementation product 2, three of No, 1 to No, 3 were manufactured, and as the conventional product 2, three of No, 1 to No, 3 were manufactured. For No, 1 to No, 3 of the implementation product 2, those shown in Fig. 10 were used respectively. The axial length (width dimension) of the recess 11e1 was set to 0.2 mm, the circumferential length of the recess 11e1 was set to 0.25 mm, the recess 11e1 was disposed at a position where it does not shift to the confluence part U, and the dimension from the axial outer edge of the annular hill portion 11e of one dynamic pressure generation part 20A to the other end face of the bearing (bearing sleeve 8) was set as L2 and was 1.9 mm, and the dimension from the axial outer edge of the annular hill portion of the other dynamic pressure generation part 20B to the other end face of the bearing was set as L3 and was 0.45 mm. In this case, No, 1 to No, 3 of the implementation product 2 were made the same in design.

[0054] Also, as No, 1 to No, 3 of the conventional product 2, as shown in Fig. 11, in the one shown in Fig. 10 , there are no recesses provided. In this case, No, 1 to No, 3 of the conventional product 2 were made the same in design as such.

[0055] The hydrodynamic bearing shown in FIG. 11 has a pair of hydrodynamic generating portions 120 (120A, 120B) provided axially spaced apart on the inner peripheral surface 108a of a bearing sleeve 108 that serves as a radial bearing surface. Each of the hydrodynamic generating portions 120A, 120B has a plurality of hydrodynamic grooves 111a, 111b arranged in a helical bone shape. The hydrodynamic grooves 111a, 111a on the axially outer side of the hydrodynamic generating portions 120A, 120B form a first group of hydrodynamic grooves 111A, 111A, and the hydrodynamic grooves 111b, 111b on the axially inner side of the hydrodynamic generating portions 120 form a second group of hydrodynamic grooves 111B, 111B. Note that the pair of hydrodynamic generating portions 120A, 120B have an upside-down shape.

[0056] Also, in each of the hydrodynamic generating portions 120A, 120B, the inclination directions of the hydrodynamic grooves 111a, 111a on the axially outer side and the hydrodynamic grooves 111b, 111b on the axially inner side are different. Inclined ridge portions 111c, 111d are provided between the hydrodynamic grooves 111a, 111b, respectively. The inclined ridge portions 11c, 11d and the annular ridge portions 11e, 11e are shown by cross-hatching.

[0057] The following Table 3 shows the functional evaluation results. In Table 3, with a load (compressive load) of 0.1 N applied to the shaft (shaft member 2), the shaft member 2 was rotated at a rotational speed of 100 to 1000 rpm for 60 seconds. The presence or absence of contact between the rotated shaft member 2 and the bearing (bearing sleeve 8) was measured. This measurement was performed by a publicly known and commonly used electrical contact method.

Table 3

[0058] For the conventional products (No. 1 to No. 3), there was contact between the shaft member and the bearing at 1000 rpm, and it can be seen that the number of contacts increased extremely when it reached 200 rpm or less. In contrast, for the implemented product 2 (No. 1 to No. 3), almost no contact was observed up to 200 rpm, and the contact at 100 rpm pm or less, and the number of contacts increased extremely. In contrast, for the implemented product 2 (No. 1 to No. 3), almost no contact was observed up to 200 rpm, and the contact at 100 rpm It can be seen that the number of touchbacks is also smaller than that in the comparative example. Note that the numerical values in Table 3 indicate the number of contacts, and the larger the value, the more contacts there are. Also, in Table 3, >500 indicates that the shaft member and the bearing have come into contact with each other 500 times or more within 60 seconds.

[0059] The presence or absence of contact between the shaft (shaft member 2) and the bearing (bearing sleeve 8) was measured while gradually increasing the load applied to the shaft (shaft member 2). In this case, those of the product 2 (No. 1 to No. 3) were used, and those of the conventional product 2 (No. 1 to No. 3) were used. With the rotational speed set at 1000 rpm the presence or absence of contact between the shaft (shaft member 2) and the bearing (bearing sleeve 8) was measured while gradually increasing the load applied to the shaft member, and the results are shown in Table 4. This measurement was also performed by a publicly known and commonly used electrical contact method. Note that in Table 4, "-" indicates that the measurement was not performed at this load. This is because the number of contacts exceeded 500 at the load immediately before this load, so the number of contacts at subsequent loads would exceed 500.

Table 4

[0060] As can be seen from Table 4, the load at which frequent contact between the shaft member and the bearing was observed was 1.27 N for the conventional product, whereas it was 1.57 N (1.2 times) for the product. Therefore, it was confirmed that the product 2 had a higher load capacity than the conventional product 2.

Explanation of Reference Numerals

[0061] 1 Hydrodynamic bearing device 2 Shaft member 3 Rotor 4 Impeller 5 Casing 8 Sintered oil-impregnated bearing (bearing sleeve) 8a Inner peripheral surface 11A, 11B Hydrodynamic groove groups 11a, 11b Hydrodynamic grooves 11c Inclined hill part 11e Annular hill part 11e1 Concave part 20(20A, 20B) Hydrodynamic generation part C Confluence part R1 Radial bearing part

Claims

1. A hydrodynamic bearing having a bearing inner diameter surface facing the outer diameter surface of a shaft member, and a hydrodynamic generation portion provided on the bearing inner diameter surface, wherein the hydrodynamic generation portion has a plurality of hydrodynamic grooves arranged in a herringbone shape, the hydrodynamic grooves are provided with first and second hydrodynamic groove groups, and inclined inclined hill portions are formed between the hydrodynamic grooves of the first and second hydrodynamic groove groups, respectively, and an annular hill portion extending in the circumferential direction and connected to each inclined hill portion is provided between the first hydrodynamic groove group and the second hydrodynamic groove group, and a concave portion for generating hydrodynamic pressure is formed in a part of the annular hill portion. The hydrodynamic bearing is characterized by this.

2. The circumferential width of the concave portion is made smaller than the circumferential width of the confluence portion, and the number of hydrodynamic grooves in the first and second hydrodynamic groove groups is made the same. The confluence portion between the inclined hill portion and the annular hill portion of the first hydrodynamic group and the confluence portion between the inclined hill portion and the annular hill portion of the second hydrodynamic group coincide, and the concave portion is provided in all the confluence portions. The hydrodynamic bearing according to claim 1, characterized by this.

3. The hydrodynamic bearing according to claim 1, characterized in that a pair of hydrodynamic generation portions having an upside-down shape spaced apart in the axial direction are formed on the bearing inner diameter surface.

4. A hydrodynamic bearing device comprising the hydrodynamic bearing according to 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 action of a lubricating fluid in a radial bearing gap formed between the inner circumferential surface of the hydrodynamic bearing and the outer circumferential surface of the shaft member.

5. A motor comprising the hydrodynamic bearing device according to claim 4, a rotor that rotates integrally with the shaft member or the hydrodynamic bearing, and a drive portion that rotationally drives the rotor, wherein the rotor has an inverter portion.

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