JP4606781B2 - Hydrodynamic bearing - Google Patents

Description

  The present invention relates to a dynamic pressure bearing.

  The hydrodynamic bearing has features such as high rotational accuracy, high speed rotation, low cost, and low noise. In recent years, these features have been utilized to make spindle motors for disk devices such as HDDs, CD-ROMs, DVD-ROMs, Or, it is widely used as a bearing for small motors such as polygon scanner motors of laser beam printers (LBP), DLP video projectors, and other axial fans.

  In this dynamic pressure bearing, a shaft member is inserted into the inner periphery of the bearing sleeve, and fluid pressure is generated by the dynamic pressure action of the dynamic pressure groove in the radial bearing gap between the inner periphery of the bearing sleeve and the outer periphery of the shaft member. The shaft member is non-contact supported by this pressure.

In this dynamic pressure bearing, the dynamic pressure groove is formed on the inner periphery of the bearing sleeve or the outer periphery of the shaft member. Particularly when the dynamic pressure groove is formed on the inner periphery of the bearing sleeve, the dynamic pressure groove having a complicated shape is formed. It is generally difficult to form accurately and efficiently. Conventionally, a method of rolling a dynamic pressure groove by inserting a special jig into the inner periphery of a soft metal bearing sleeve has been mainly used, and an example thereof is disclosed in Japanese Patent Laid-Open No. 2000-312943 (Patent Document 1). Are listed.
JP 2000-312943 A

  By the way, in the conventional dynamic pressure bearing, the rotation direction of the shaft member is limited to one direction (forward rotation), but if this can be used in the reverse rotation direction, it is beneficial for further expansion of the application of the dynamic pressure bearing. It is. Further, when the rotation direction is limited to one direction, when the bearing sleeve is incorporated into the bearing device, it is necessary to incorporate the bearing sleeve in a direction that matches the rotation direction. Conventionally, an identification mark is attached to the surface of the bearing sleeve so that the orientation of the bearing sleeve can be identified, but it is still inevitable that the assembling work is complicated.

  On the other hand, in order to be able to be used even in reverse rotation, it is necessary to newly form a dynamic pressure groove inclined in the opposite direction separately from the dynamic pressure groove for forward rotation. Conventionally, since the dynamic pressure grooves are formed by rolling, it is difficult to form the dynamic pressure grooves for forward and reverse rotation that have a more complicated shape, and it is difficult to meet the above requirements. Even if the dynamic pressure groove for forward and reverse rotation can be formed, if the bearing sleeve is made of a solid metal material, negative pressure is generated from the reverse rotation dynamic pressure groove during forward rotation. This may cause the occurrence of whirl and oil leakage.

  Accordingly, an object of the present invention is to provide a dynamic pressure bearing that can be used in both forward and reverse rotational directions.

To achieve the above object, the present invention provides a bearing sleeve having a dynamic pressure groove region in which a plurality of dynamic pressure grooves are arranged in the circumferential direction on an inner periphery, and a shaft member inserted in the inner periphery of the bearing sleeve. Dynamic pressure for non-contact support of the shaft member in the radial direction by the dynamic pressure action of the fluid generated in the radial bearing gap between the outer periphery of the shaft member and the inner periphery of the bearing sleeve during relative rotation of the shaft member and the bearing sleeve In the bearing, the bearing sleeve is made of sintered metal, and is formed on the inner circumference of the bearing sleeve in the axial direction so as to be separated in the axial direction without interposing a dynamic pressure groove region therebetween. The dynamic pressure groove region A11 and the first reverse rotation dynamic pressure groove region A21 on the other side in the axial direction are provided, and the inner peripheral surface of the bearing sleeve having these dynamic pressure groove regions is a molded surface. The first normal rotation dynamic pressure groove region A11 and the first reverse rotation dynamic pressure groove region A21 and includes a dynamic pressure grooves that are inclined relative to the axial direction, which between a dynamic pressure grooves inclined in the opposite direction to another position in the axial direction, the first dynamic pressure groove area of the positive rotation in each of the the A11 first hydrodynamic groove area A21 of the reverse rotation, and characterized in that the dynamic pressure grooves of the closest portion to the opposing hydrodynamic groove region, both tilted in the same direction To do.

  If the bearing sleeve is made of sintered metal, the dynamic pressure groove region is provided with a groove shape having a corresponding concavo-convex shape on the inner periphery of the bearing sleeve, and applying a compression force to the bearing sleeve to It can be formed by pressing the peripheral surface against the groove mold. In this case, the inner peripheral surface of the bearing sleeve undergoes plastic deformation, and the groove-shaped irregularities are transferred to the inner peripheral surface of the bearing sleeve, so that a dynamic pressure groove region molded on the inner peripheral surface is formed. With this mold forming, it is possible to accurately and efficiently form the inner circumferential surface of the bearing sleeve having a complicated shape having dynamic pressure groove regions for forward rotation and reverse rotation, in both forward and reverse rotation directions. A usable dynamic pressure bearing can be provided. Also, when negative pressure is generated in the reverse rotation dynamic pressure groove during forward rotation, oil oozes out from the bearing sleeve through the surface opening into the radial bearing gap, reducing or canceling the negative pressure. Can do. At this time, it is desirable to set the surface area ratio of the inner peripheral surface of the bearing sleeve, particularly the dynamic pressure groove region for both forward and reverse rotations, in the range of 2 to 20%. This is because if it is less than 2%, the effect of reducing the negative pressure becomes insufficient, and if it exceeds 20%, sufficient dynamic pressure action cannot be obtained.

The bearing sleeve further includes a second reverse rotation dynamic pressure groove region A22 on the one axial side of the first normal rotation dynamic pressure groove region A11, and the first reverse rotation dynamic pressure groove region A11. It is assumed that a second dynamic pressure groove region A12 for positive rotation is provided on the other axial side of the pressure groove region A21. In this case, if the inter-region pitch between the two normal rotation dynamic pressure groove regions A11, A12 and the two reverse rotation dynamic pressure groove regions A21, A22 are made the same, the reverse rotation is the same as during normal rotation. The moment stiffness can be made uniform.
Further, the first normal rotation dynamic pressure groove region A11 and the second reverse rotation dynamic pressure groove region A22 are partially overlapped in the axial direction, and the first reverse rotation dynamic pressure The groove region A21 and the second dynamic pressure groove region A12 for positive rotation may partially overlap in the axial direction.

  As described above, according to the present invention, a hydrodynamic bearing that can be used in both forward and reverse rotational directions can be obtained at low cost. As a result, the application of the hydrodynamic bearing can be expanded, and even when the rotational direction is limited to one direction, the directionality when the bearing sleeve is incorporated does not become a problem, and the assembling workability is improved.

  Hereinafter, embodiments of the present invention will be described.

  As shown in FIG. 2, the hydrodynamic bearing 1 according to the present invention includes a shaft member 2 and a cylindrical bearing sleeve 3 in which the shaft member 2 is inserted on the inner periphery as main components.

The shaft member 2 is formed of a metal material such as stainless steel, and the outer peripheral surface 2a facing the inner periphery of the bearing sleeve 3 is formed into a smooth cylindrical surface. The bearing sleeve 3 is formed of a sintered metal, such as copper or iron, or an oil-containing sintered metal obtained by impregnating a lubricating metal (or lubricating grease) with a sintered metal mainly composed of both. On the inner peripheral surface of the bearing sleeve, as shown in FIG. 1, there are a plurality of circumferential dynamic pressure groove regions A11, A12, A21, A22 having a plurality of dynamic pressure grooves 4 in the axial direction (four in the illustrated example). Place).

Each of the dynamic pressure groove regions A11, A12, A21, A22 is formed by arranging a plurality of dynamic pressure grooves 4 inclined with respect to the axial direction over the entire circumference in the circumferential direction. FIG. A so-called herringbone-shaped dynamic pressure groove region in which the dynamic pressure grooves 4 are arranged on both sides of the direction center line with the inclination direction reversed is illustrated. However, this arrangement is merely an example, and dynamic pressure groove regions having other shapes can be formed.

In FIG. 1, an annular smooth portion 5 is provided between the dynamic pressure grooves 4 adjacent in the axial direction and is partitioned by the smooth portion 5 so that the dynamic pressure grooves 4 adjacent in the axial direction are discontinuous. Examples of the dynamic pressure groove regions A11, A12, A21, and A22 are shown. In this discontinuous type, the back portion 6 and the smooth portion 5 between the dynamic pressure grooves 4 adjacent in the circumferential direction are at the same level. In addition, the continuous dynamic pressure groove regions A11, A12, A21, and A22 (see FIG. 7) in which the smoothing portion 5 is eliminated and the dynamic pressure grooves 4 adjacent in the axial direction are made continuous can be used.

In the present invention, as the dynamic pressure groove areas A11, A12, A21, A22 , two types of areas A11, A12 for normal rotation and areas A21, A22 for reverse rotation are provided, and this point is a dynamic pressure for normal rotation. This is different from the conventional product (see FIG. 12) having only the groove regions A11 and A12 . The dynamic pressure groove area A11, A12 for forward rotation and the dynamic pressure groove area A21, A22 for reverse rotation are the same as the size of the dynamic pressure groove 4 except that the direction of inclination of the dynamic pressure groove 4 is reversed. The shape, depth, and number are the same.

In this dynamic pressure bearing, when one of the shaft member 2 and the bearing sleeve 3 (for example, the bearing sleeve 3) is fixed and the other (for example, the shaft member 2) is rotated in the forward direction, the dynamic pressure action of the dynamic pressure groove 4 causes In the radial bearing gap between the first positive rotation dynamic pressure groove region A11 and the second positive rotation dynamic pressure groove region A12 and the outer peripheral surface 2a of the shaft member 2 opposed thereto, lubrication of oil or the like is performed. A fluid pressure is generated, and the shaft member 2 and the bearing sleeve 3 are held in non-contact by this pressure. Similarly, when rotating in the reverse direction, the first reverse rotation dynamic pressure groove region A21 and the second reverse rotation dynamic pressure groove region A22 and the outer peripheral surface 2a of the shaft member 2 opposed thereto are also shown. A pressure of the lubricating fluid is generated in the radial bearing gap therebetween, and the shaft member 2 and the bearing sleeve 3 are held in a non-contact state by this pressure. Therefore, it is possible to support rotation in both forward and reverse directions with one dynamic pressure bearing 1.

In particular, as shown in the figure, when the axial positions of the dynamic pressure groove areas A11, A12 for forward rotation and the dynamic pressure groove areas A21, 22 for reverse rotation are shifted and formed independently, Since mutual interference between the dynamic pressure groove regions A11, A12, A21, and A22 for rotation and reverse rotation can be suppressed, high rotation accuracy can be obtained.

Further, as in the illustrated example, the positive rotation dynamic pressure groove regions A11 and A12 and the reverse rotation dynamic pressure groove regions A21 and A22 are alternately arranged in the axial direction, and two forward rotation dynamic pressure groove regions A11, If the inter-region pitch P1 of A12 and the inter-region pitch P2 of the reverse rotation dynamic pressure groove regions A21 and A22 are made equal, the moment rigidity of the bearing can be made equal in both the forward and reverse rotational directions, and the forward and reverse rotational directions. The bearing performance can be standardized. Of course, depending on the application, moment rigidity may not be required so much in one rotation direction (for example, the reverse rotation direction). In that case, as shown in FIG. 3, two reverse rotation dynamic pressure groove regions A21 and A22 are provided. By adopting a shape that is sandwiched between the positive rotation dynamic pressure groove regions A11 and A12 from both sides in the axial direction , the inter-region pitch P2 of the reverse rotation dynamic pressure groove regions A21 and A22 is set to the positive rotation dynamic pressure groove regions A11 and A12 . It may be smaller than the inter-pitch P1.

  If the hydrodynamic bearing 1 can be used in both forward and reverse rotational directions in this way, the orientation of the bearing sleeve 3 does not matter even if the rotational direction of the shaft member is limited to any one direction. In addition to improving the performance, an identification mark attached to the bearing sleeve 3 can be made unnecessary.

The dynamic pressure groove regions A11, A12, A21, A22 on the inner periphery of the bearing sleeve 3 can be formed by molding. FIG. 4 shows an example of this mold forming process. In this process, as shown in the drawing, a core rod 11 having a groove die 11a having a shape corresponding to the inner peripheral surface shape of the bearing sleeve 3 is inserted into the inner periphery of a cylindrical sintered metal material 3 ′. In this state, the bearing sleeve 3 is pushed into the die 13 by restraining both end surfaces in the axial direction with the punches 12a and 12b. In the die 12, a pressing force is applied to the sintered metal material 3 ′ from the punches 12 a and 12 b and the die 12, and the inner peripheral surface is pressed against the groove die 11 a of the core rod 11. As a result, the inner peripheral surface of the sintered metal material 3 ′ undergoes plastic deformation, and the uneven shape of the groove mold 11a is transferred, and the dynamic pressure groove areas A11, A12, A21, A22 are molded. At this time, the dynamic pressure grooves 4, the back portion 6, and the smooth portion 5 of the dynamic pressure groove regions A11, A12, A21, and A22 are simultaneously formed by the unevenness of the groove mold 11a.

When the sintered metal material 3 ′ is taken out from the die 13 after the forming is finished, the inner peripheral surface thereof is enlarged by the spring back of the material 3 ′, so the groove 11a and the dynamic pressure groove regions A11, A12, A21, The sintered metal material 3 ′ can be removed smoothly without causing interference with A22 . The bearing sleeve 3 is obtained by impregnating the demolded sintered metal material 3 ′ with lubricating oil by means such as vacuum impregnation.

  FIG. 5 shows a configuration example of a fluid dynamic bearing device using the fluid dynamic bearing 1 described above. In addition to the dynamic pressure bearing 1, the dynamic pressure bearing device has a structure including a bottomed cylindrical housing 15 having a bottom portion 15a integrally or separately. A shaft member 2 that serves as a shaft of the motor 16 is inserted into the inner periphery of the housing 3, and the gap (including the radial bearing clearance) between the outer peripheral surface 2 a of the shaft member 2 and the inner peripheral surface of the bearing sleeve 3 is used as a lubricating fluid. Is filled with oil. In this configuration, when the motor 16 is driven forward / reversely, forward / reverse rotation of the shaft member 2 is supported in a non-contact manner in the radial direction.

  Hereinafter, other embodiments of the present invention will be described with reference to FIGS.

FIG. 6 shows the dynamic pressure for positive rotation by continuing the back portion 6 of the adjacent dynamic pressure groove regions A11, A22 and A12, A21 in the dynamic pressure groove regions A11, A12, A21, A22 shown in FIG. The groove regions A11, A12 and the reverse rotation dynamic pressure groove regions A21, A22 are partially overlapped in the axial direction. In this case, since the occupied space in the axial direction of the dynamic pressure groove regions A11, A12, A21, A22 is reduced by the overlap, the inter-region pitches P1, P2 of the same type of dynamic pressure groove regions are compared with the embodiment of FIG. The moment rigidity of the bearing can be further improved.

FIG. 7 shows the configuration shown in FIG. 6, in which the smoothing portions 5 of the adjacent forward and reverse dynamic pressure groove regions A11, A22 and A12, A21 are eliminated, and the dynamic pressure grooves 4 and the back portions 6 on both sides in the axial direction are opposed. It shows a so-called continuous type dynamic pressure groove shape continuous with the side. The back portion 6 continuous between the dynamic pressure groove regions A11 and A22 and between A12 and A21 may be discontinuous as in FIG.

FIG. 8 is a partial area formed by dividing the dynamic pressure groove areas A11 and A12 for positive rotation into the circumferential direction equal pitch in the configuration shown in FIG. It is formed in a plurality of (preferably three or more) regions separated in the circumferential direction. The reverse rotation dynamic pressure groove regions A21 and A22 are also arranged in the same manner, but their circumferential phases are shifted from the forward rotation dynamic pressure groove regions A11 and A12 . The back portion 6 is made to be continuous with the back portion 6 of the opposite dynamic pressure groove region at both ends in the circumferential direction of the dynamic pressure groove regions A11, A12 for forward rotation and the dynamic pressure groove regions A21, A22 for reverse rotation. Yes.

The embodiment shown in FIGS. 1 and 6 to 8 described above is such that the axial pressure positions of the dynamic pressure groove areas A11, A12 for forward rotation and the dynamic pressure groove areas A21, A22 for reverse rotation are different. On the other hand, in the embodiment shown in FIGS. 9 to 11, the axial positions of adjacent dynamic pressure groove regions (A11 and A22, and A21 and A12) are made the same, and both dynamic pressure groove regions (A11 and A22) are used. , And A21 and A12) are completely overlapped in the axial direction. In this case, since the axial pitch P between the two dynamic pressure groove regions separated in the axial direction is further increased, the moment rigidity of the bearing can be further increased.

  Of these, FIG. 9 shows an example in which the dynamic pressure grooves 4 for forward rotation and the dynamic pressure grooves 4 for reverse rotation are alternately arranged in the circumferential direction, and FIG. 10 shows a dynamic pressure groove region A1 for positive rotation. This is an example in which the dynamic pressure groove region A2 for reverse rotation is formed on the inner peripheral surface of the bearing sleeve 3 with the circumferential phase shifted as in FIG.

FIG. 11 shows the configuration of FIG. 10, in which one of the normal rotation dynamic pressure groove regions A11, A12 and the reverse rotation dynamic pressure groove regions A21, A22 (for example, the reverse rotation dynamic pressure groove regions A21, A22 ). This is an example in which the number of the dynamic pressure grooves 4 is smaller than that of the other dynamic pressure grooves 4. In this case, the dynamic pressure action in the reverse rotation dynamic pressure groove areas A21 and A22 having a small number of dynamic pressure grooves is reduced , and the dynamic pressure action in the dynamic pressure groove areas A11 and A12 having a large number of dynamic pressure grooves is increased. In the forward rotation, a large amount of pressure can be generated by the radial bearing gap, which is particularly suitable for an application that requires more torque during forward rotation than during reverse rotation.

1 is a cross-sectional view of a bearing sleeve according to a first embodiment of the present invention. It is sectional drawing of the dynamic pressure bearing using the bearing sleeve shown in FIG. It is sectional drawing which shows the other form of the dynamic pressure groove area | region formed in the bearing sleeve inner periphery. It is sectional drawing which shows the formation process of a dynamic pressure groove area | region. It is sectional drawing of the dynamic pressure bearing apparatus which uses the dynamic pressure bearing shown in FIG. It is sectional drawing which shows 2nd embodiment of this invention. It is sectional drawing which shows 3rd embodiment of this invention. It is sectional drawing which shows 4th embodiment of this invention. It is sectional drawing which shows 5th embodiment of this invention. It is sectional drawing which shows the 6th embodiment of this invention. It is sectional drawing which shows 7th embodiment of this invention. It is sectional drawing which shows the form of the conventional dynamic pressure groove area | region.

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing 2 Shaft member 2a Outer peripheral surface 3 Bearing sleeve 4 Dynamic pressure groove 5 Smooth part 6 Back part 11 Core rod 11a Groove type 12a, 12b Punch 13 Dies 15 Housing 15a Bottom part 16 Motor
A11, A12 dynamic pressure groove area (For forward rotation)
A21, A22 dynamic pressure groove area (for reverse rotation)

Claims (5)

A bearing sleeve having a dynamic pressure groove region in which a plurality of dynamic pressure grooves are arranged in a circumferential direction on an inner periphery, and a shaft member inserted in the inner periphery of the bearing sleeve, and when the shaft member and the bearing sleeve are relatively rotated In the hydrodynamic bearing that supports the shaft member in the radial direction by the hydrodynamic action of the fluid generated in the radial bearing gap between the outer periphery of the shaft member and the inner periphery of the bearing sleeve,
The bearing sleeve is made of sintered metal, and is formed on the inner periphery of the bearing sleeve by separating it in the axial direction without interposing a dynamic pressure groove region therebetween. A groove region A11 and a first dynamic pressure groove region A21 for reverse rotation on the other side in the axial direction, and an inner peripheral surface of a bearing sleeve having these dynamic pressure groove regions is a molded surface, The first dynamic pressure groove region A11 for forward rotation and the first dynamic pressure groove region A21 for reverse rotation are each inclined with respect to the axial direction, and the dynamic pressure is inclined in the opposite direction. a groove provided in a different position in the axial direction, in each dynamic pressure generating groove area A21 of the first and hydrodynamic groove area A11 of the forward rotation for first reverse rotation, the counterpart of the dynamic groove region A hydrodynamic bearing characterized in that all of the hydrodynamic grooves of the closest approach are inclined in the same direction .   The first normal rotation dynamic pressure groove region A11 has a second reverse rotation dynamic pressure groove region A22 on one axial side, and the first reverse rotation dynamic pressure groove region A21 The hydrodynamic bearing according to claim 1, further comprising a second hydrodynamic groove region for positive rotation A12 on the other axial side.   The first normal rotation dynamic pressure groove region A11 and the second reverse rotation dynamic pressure groove region A22 partially overlap in the axial direction, and the first reverse rotation dynamic pressure groove region A22 The hydrodynamic bearing device according to claim 2, wherein A21 and the second hydrodynamic groove region A12 for positive rotation partially overlap in the axial direction.   4. The hydrodynamic bearing according to claim 2 or 3, wherein the pitch between the two positive rotation dynamic pressure groove regions A11, A12 is the same as the pitch between the two reverse rotation dynamic pressure groove regions A21, A22.   The hydrodynamic bearing device according to any one of claims 1 to 4, wherein a surface opening ratio of an inner peripheral surface of the bearing sleeve is 2 to 20%.

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