JPH08186952A - Motor - Google Patents

Abstract

PURPOSE: To obtain a small-sized high-speed motor having high reliability and capable of maintaining high-precision bearing support without leakage or exhaustion of fluid lubricating oil. CONSTITUTION: This is a motor equipped with a housing 1, a shaft member 2 fixed to the housing 1, a rotor 3 supported for relative rotation relative to the shaft member 2, and dynamic pressure bearings A, B, C and D by fluid lubricating oil located between the shaft member 2 and the rotor 3. A tapered gap portion is provided for preventing the leakage of the fluid lubricating oil at the outer side of respective bearings C and B of the motor, and also a ring- shaped gap portion 75 is formed between a sleeve 4 and thrust cover 5 thereby retaining the fluid lubricating oil. By the balance between atmospheric pressure and the surface tension at the tapered gap portion, the fluid lubricating oil of the gap portion 75 is supplied or stored to the bearing portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor which uses a hydrodynamic bearing for a bearing portion using a fluid lubricant.

[0002]

2. Description of the Related Art For example, a precision motor such as a spindle motor incorporated in a recording disk driving device such as an optical disk or a magnetic disk supports a rotating member with high accuracy due to the nature of a driving load, and minimizes shake and rattling. Accurate rotation support is required. In order to meet such demands, the conventional ball bearing has been replaced in the bearing portion by a dynamic pressure bearing means using a fluid lubricant, and various configurations accompanying it have been proposed. In particular, the motor used for the above-mentioned application is required to have as little axial (thrust) play as possible in the axial direction of the rotor. Therefore, in addition to the radial dynamic pressure bearing, a thrust dynamic pressure bearing is used in combination.

For example, in Japanese Patent Publication No. 63-43606,
A thrust dynamic bearing configuration is shown. The dynamic pressure generating groove 1 is formed on both end faces of the thrust bearing collar (thrust plate) 10.
3, 13 ′ are provided, and the housing 11 is configured so as to sandwich the thrust plate 10. A lubricating oil 12 is filled between the thrust plate 10 and the housing 11.

[0004]

However, in such a structure, there is a drawback that the lubricating oil is pushed out and leaks due to the rotation / stop operation around the bearing, the change in the ambient temperature and the like. Further, in recent years, various OA devices and the like in which a motor is incorporated are being downsized and rotated at a high speed, so that the amount of fluid lubricant such as lubricating oil retained on both end faces of the thrust plate is reduced. While,
The centrifugal force generated by the high-speed rotation of the rotor makes it easier for the fluid lubricant in the thrust plate to flow out. The leakage of the fluid lubricant makes it impossible to maintain stable and highly accurate bearing support in the dynamic pressure bearing portion, which causes a significant reduction in bearing life.

The present invention has been made in view of the above-mentioned problems existing in the prior art, and the problem is that it is possible to realize downsizing and high speed rotation, and An object of the present invention is to provide a highly reliable motor capable of maintaining highly accurate bearing support without leakage or depletion.

[0006]

To achieve the above object, a motor according to the present invention includes a housing, a rotor rotatably supported relative to the housing, and an interposition between the housing and the rotor. A dynamic pressure bearing means using a fluid lubricant that has been formed; a taper shape in which a radial gap between the housing and the rotor increases on the outside of the motor, which is continuous with the dynamic pressure bearing means. A fluid lubricant in the tapered gap is held in equilibrium with the atmospheric pressure outside the motor, and the housing or the rotor is provided with an annular gap in which the fluid lubricant communicates. The gap portion is provided with a ventilation hole for communicating with the atmosphere, and the excess fluid lubricant that cannot be held by the dynamic pressure bearing means is retained and retained in the annular gap portion, and When fluid lubricant is insufficient interposed bearing means is a fluid lubricant of the annular gap is supplied to the dynamic pressure bearing means.

In the above motor, it is desirable that the tapered gap portion has its opening radially inward. In addition, it is preferable that the cross-sectional shape of the connection portion between the ventilation hole and the annular gap is set to be larger than the radial cross-sectional shape of the annular gap. Further, it is preferable that the vent hole is provided in the motor so as to be positioned inward of the annular gap portion in the radial direction.

[0008]

According to the motor of the present invention, the tapered gap portion for holding the fluid lubricant is provided on the outer side of the motor which is continuous with the dynamic pressure bearing means. The fluid lubricant held in the tapered gap communicates with the fluid lubricant interposed in the dynamic pressure bearing means. Therefore, even if the fluid lubricant in the dynamic pressure bearing means inside the motor leaks to the outside of the motor due to the temperature rise of the motor or shock from the outside, the fluid retained in the tapered gap The lubricant acts against the fluid lubricant that is about to leak under the influence of surface tension due to atmospheric pressure. Therefore, these contradictory acting forces are balanced at a predetermined portion of the tapered gap, and the fluid lubricant is retained. That is, the tapered gap portion serves as a sealing means for preventing the fluid lubricant inside the motor from leaking to the outside of the motor. The fluid lubricant retained in the tapered gap portion is retained in any continuous equilibrium portion because the gap portion is tapered, that is, the gap increases with the outside of the motor, and leakage occurs at the equilibrium position. Receive an action force against.

On the other hand, an annular gap is provided in the housing or the rotor, and the annular gap communicates with the fluid lubricant interposed in the dynamic pressure bearing means, and the excess fluid that cannot be held by the dynamic pressure bearing means. The lubricant is retained and retained.
Therefore, when the fluid lubricant intervening in the dynamic pressure bearing means is insufficient, the fluid lubricant in the annular gap is supplied to the dynamic pressure bearing means, so that the fluid lubricant in the bearing portion is prevented from being depleted. Therefore, stable and reliable dynamic pressure bearing support is provided.

Since the vent hole communicating with the atmosphere is provided in the annular gap, there is no difference in atmospheric pressure between the inside of the annular gap and the outside of the motor. Therefore, the fluid lubricant is pushed out of the motor due to a change in the motor temperature or the like regardless of the amount of the fluid lubricant retained and retained in the annular gap or even when bubbles are present in the fluid lubricant. There is no. Further, the fluid lubricant retained in the annular gap is continuous with the fluid lubricant of the dynamic pressure bearing means and the tapered gap which communicate with the annular gap, so that the surface tension in the tapered gap is maintained in equilibrium. Has been done. Thereby, the flow of the fluid lubricant between the dynamic pressure bearing means and the annular gap portion is further promoted, and the smooth supply and storage of the fluid lubricant can be realized.

Further, since the opening of the tapered gap portion is provided inward in the radial direction, the tapered gap portion is formed even if the centrifugal force accompanying the rotation of the rotor is received (radially outward). Since the inner peripheral wall (on the side) is held so as to surround the fluid lubricant, leakage of the fluid lubricant from the tapered gap is further prevented.

Next, the cross-sectional shape of the connecting portion between the ventilation hole and the annular gap is set to be larger than the radial cross-sectional shape of the annular gap, so that the fluid lubricant is subjected to surface tension. As a result, leakage from the ventilation holes is prevented. Further, by positioning the vent hole radially inward of the annular gap, the fluid lubricant can be prevented from leaking from the vent hole even when subjected to the centrifugal force caused by the rotational driving of the rotor.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a motor according to the present invention will be described with reference to the accompanying drawings. To do. FIG. 1 is an overall cross-sectional view of a motor for rotating a recording disk, for example. 2 is an enlarged sectional view showing the upper portion of FIG. 1 and the peripheral portion of the thrust plate 5, and FIG. 3 is an enlarged sectional view showing the lower peripheral portion of the sleeve 4 of FIG. In these drawings, the same numbers are given to the same members and parts.

In FIG. 1, the housing 1 is made of an aluminum alloy, and a boss portion 16 is formed at the center of the housing 1 so as to bulge upward (inside the motor). The boss portion 16 is provided with the hole portion 15 at the center thereof,
The lower end of the shaft 2 is fitted and fixed. The shaft 2 is mounted substantially perpendicular to the mounting surface of the housing 1. The shaft 2 is made of, for example, an iron-based alloy, and a disk-shaped thrust plate 5 is integrally provided on the upper end side. The thrust plate 5 is provided with respect to the longitudinal (axial) direction of the shaft 2.
The upper and lower ends 33, which are formed substantially at right angles,
The surfaces 34 are formed so as to be substantially parallel to each other.

The rotor 3 rotatably supported on the shaft 2 is
It has a substantially cylindrical sleeve 4 and a hub 10 fixed to the outer peripheral side of the sleeve 4. The hub 10 is formed of, for example, an aluminum alloy, and a recording disk (not shown) as a rotational load is externally fitted and mounted on the outer peripheral portion 49 of the hub 10. The flange 41 of the hub 10 is for receiving the recording disk, the hole 20 is a screw hole for attaching a clamp member, and the hole 21 is a stick hole for preventing rotation when fixing the recording disk.

The sleeve 4 is composed of a cylindrical peripheral wall 24 occupying most of the entire length of the sleeve 4, and an enlarged diameter portion 25 integrally provided on the upper portion thereof, which are formed coaxially with the shaft 2. . The sleeve 4 is made of a copper alloy material such as lead bronze. Expanded portion 25 of sleeve 4
Has a step portion 27 formed on the inner peripheral side. Sleeve 4
The thrust cover 6 is mounted on the upper portion of the step portion 27 of the. The thrust cover 6 has a ring shape, the outer peripheral portion of which is fitted on the inner peripheral side of the upper portion of the sleeve 4, and the upper end portion 3
2 is crimped and tightly fixed to the sleeve 4. The inner peripheral portion 57 of the thrust cover 6 is the outer peripheral portion 19 of the shaft 2.
And is facing with a slight gap. The sleeve 4, the hub 10, and the thrust cover 6 fixed to the sleeve 4 are rotatably supported on the shaft 2.

The boss portion 16 of the housing 1 is provided with a step portion 17 on the upper outer periphery thereof, and the stator 7 is fixed to the step portion 17. In the stator 7, the stator coil 11 is wound around a stator core 12 having predetermined magnetic pole teeth. The coil lead wire 13 drawn out from the stator coil 11 is connected to the flexible circuit board 14 attached on the housing 1, and a connection wire not shown is led out of the motor via an insulating bush 23. A rotor magnet 8 is mounted via a magnetic yoke 9 on the hub 10 side (the inner peripheral portion 18 of the hub 10) that faces the stator 7 in the radial direction. Therefore, when a predetermined electric signal is applied to the coil lead wire 13, electromagnetic interaction between the rotor magnet 8 and the stator 7 causes the rotor 3 (hub 1
0) is driven to rotate.

Rotational support of the rotor 3 with respect to the shaft 2 is achieved by a dynamic pressure bearing via a fluid lubricant made of lubricating oil. In the substantially central portion of the outer peripheral portion 19 of the shaft 2,
There is provided a reduced diameter portion 35 formed by slightly reducing the outer diameter of the outer peripheral portion 19. Outer peripheral portions 47 and 48 having outer peripheral surfaces formed with a predetermined outer diameter dimension are provided on both sides in the vertical direction. The outer peripheral portions 47 and 48 are
The radial dynamic pressure bearing portions A and B are constituted by these and the sleeve 4 which is fitted in the radial direction and faces each other. In order to configure the radial dynamic pressure bearing portions A and B, a herringbone-shaped dynamic pressure generating groove formed at predetermined intervals in the circumferential direction is formed at the corresponding portion of the inner peripheral portion 31 of the sleeve 4, although not shown. It is provided all around. The dynamic pressure generating groove may be provided on the outer peripheral portions 47, 48 side of the shaft 2 facing the sleeve 4 side.

The lower end portion 52 of the thrust cover 6, the upper end portion 33 of the thrust plate 5 that axially opposes the lower end portion 52, and the lower end portion 34 of the thrust plate 5 that faces the sleeve 4 in the same direction (the peripheral wall). The upper end portion 44 (of 24) constitutes thrust dynamic pressure bearing portions C and D.
Since the thrust dynamic pressure bearing portions C and D are configured, the upper and lower end portions 33 and 34 of the thrust plate 5 have a herringbone or spiral dynamic pressure formed at predetermined intervals in the circumferential direction although not shown. Generation grooves are provided all around. The dynamic pressure generating grooves may be provided on the lower end portion 52 side of the thrust cover 6 and the upper end portion 44 side of the sleeve 4 which face each other.

The motor of this embodiment will be further described in detail with reference to FIGS. 2 and 3. FIG. 2 mainly shows a portion of the thrust plate 5, and FIG. 2A is a plan view of the motor of FIG. 1 on the side of the thrust cover 6, that is, FIG. 5 is an enlarged cross-sectional view of the peripheral portion of FIG. In FIGS. 2A and 2B, the thrust dynamic pressure bearing portions C and D are provided with a fluid lubricant interposed therebetween. An annular gap 60 defined by the thrust cover 6 (lower end portion 52) and the sleeve 4 (inner peripheral portion 61 of the step portion 27, upper end portion 44 of the peripheral wall 24) is provided on the outer peripheral end side of the thrust plate 5. ing. The annular gap 60 is filled with a fluid lubricant that communicates with the thrust dynamic pressure bearing portions C and D.

An annular gap portion 75 having an arc-shaped cross section is provided at a joint portion 77 to which the lower end portion 52 of the thrust cover 6 and the upper end portion 71 (of the step portion 27) of the sleeve 4 are fixed. There is. The annular gap portion 75 is formed by cutting out the lower end portion 52 of the thrust cover 6 over the entire circumference. The annular gap portion 75 is filled with a fluid lubricant, and the annular gap 6 is passed through a joint portion 77 forming a relatively narrow gap.
It communicates with 0. It is desirable that the joint portion 77 is a minute gap through which the fluid lubricant easily communicates, but the air (air bubbles) contained in the fluid lubricant does not pass through. Annular gap 7
The fluid lubricant retained in 5 is thrust dynamic pressure bearing portion C,
The fluid lubricant held in D and the fluid lubricant in the annular gap 60 communicating with the fluid lubricant are communicated with each other, and excess fluid lubricant that cannot be held in these portions is held in the annular gap 75. It Therefore, when a situation occurs where the fluid lubricant to be retained in these portions runs short, the annular gap portion 75
The fluid lubricant held in the
0 and the thrust dynamic pressure bearing portions C and D. Although the annular gap 60 has a larger gap width than the joint portion 77 in FIG. 2B, a narrow gap width can be used as in the joint portion 77. Further, as shown in FIG. 2A, the fluid lubricant retained in the annular gap portion 75 may be contained in the annular gap portion 75 in an amount of 20 to 80%. Tension and taper gap 78
It suffices that the surface tension acting on is balanced.

The thrust cover 6 having the annular gap 75 is provided with a vent hole 74 for venting to the outside of the motor. The vent hole 74 is formed at one location in the circumferential direction on the thrust cover 6 and also penetrates in the axial direction. The vent hole 74 is arranged so as to communicate with the annular gap 75 and is positioned closer to the shaft 2 than the annular gap 75, that is, on the inner peripheral side (radially inward). And vent 74
The cross-sectional shape of the connecting portion 76 between the annular gap portion 75 and the annular gap portion 75 is set to be larger than the sectional shape of the annular gap portion 75.

A seal member such as an O-ring is fitted into the lower end of the thrust cover 6 on the outer peripheral side in a gap with the sleeve 4, whereby the fluid lubricant is prevented from leaking from the joint 77 to the upper portion of the thrust cover. Absent.

Above the thrust dynamic pressure bearing portion C (outside the motor) where the shaft 2 and the thrust cover 6 face each other,
A tapered gap 78 is provided. The tapered gap 78 and the inner peripheral portion 57 of the thrust cover 6 and the shaft 2
The outer peripheral portion 19 of the thrust dynamic pressure bearing portion C communicates with and holds the gap between the outer peripheral portion 19 and the outer peripheral portion 19 of the motor. . The peripheral surface of the thrust cover inner peripheral portion 57 forming the tapered gap portion 78 is formed substantially parallel to the axial direction, while the outer peripheral portion 19 is reduced in diameter on the shaft 2 side in accordance with the axial end (upper in the figure). A tapered groove 79 is formed so that

Since the fluid lubricant held in the tapered gap 78 faces the atmospheric pressure outside the motor, it is subjected to surface tension. Therefore, according to the motor of the present embodiment based on the above configuration, in the unlikely event that the temperature of the motor rises (for example, the internal temperature rises due to the heat generation of the stator 7) or the impact from the outside causes the fluid inside the motor Even if the lubricant leaks to the outside of the motor, the fluid lubricant held in the tapered gap 78 acts against the leaking fluid lubricant under the influence of the surface tension due to the atmospheric pressure. Therefore, these contradictory acting forces are balanced at a predetermined portion of the tapered gap portion 78, and the fluid lubricant is retained. That is, the tapered gap 78 serves as a sealing means for preventing the fluid lubricant inside the motor from leaking out of the motor. The fluid lubricant held in the tapered gap portion 78 is held in a continuous arbitrary equilibrium portion at the equilibrium position because the gap portion has a taper shape, that is, the gap increases with the outside of the motor. It receives a great deal of force against the leakage of fluid lubricant. This prevents the fluid lubricant from leaking out of the motor.

The annular gap portion 75 formed by the thrust cover 6 and the sleeve 4 communicates with the fluid lubricant interposed in the dynamic pressure bearing means C, D, etc., and is an excess fluid lubrication that cannot be held by these. The agent is retained and retained. Therefore, when the fluid lubricant intervening in the dynamic pressure bearing means C, D, etc. runs short, the fluid lubricant in the annular gap portion 75 becomes less than the dynamic pressure bearing means C, D.
Since it is supplied to D etc., the depletion of the fluid lubricant in the bearing portion can be prevented in advance, and stable and highly reliable dynamic pressure bearing support can be achieved.

Since the annular gap portion 75 is provided with the vent hole 74 communicating with the atmosphere, the annular gap portion 76 is provided.
There is no pressure difference between the inside and the outside of the motor. Therefore, regardless of the amount of the fluid lubricant retained in the annular gap 75, or even if air bubbles are present in the fluid lubricant, the fluid lubricant is pushed out of the motor due to changes in the motor temperature or the like. Never. Further, the fluid lubricant held in the annular gap portion 75 is the dynamic pressure bearing means C, which communicates with the fluid lubricant.
D, etc., are continuous with the fluid lubricant in the tapered gap 78, respectively, and thus are in equilibrium with the surface tension in the tapered gap 78. Thereby, the flow of the fluid lubricant between the dynamic pressure bearing means C, D and the like and the annular gap portion 75 is further promoted, and the smooth supply and storage of the fluid lubricant can be realized. Therefore, in the annular gap portion 75, in addition to eliminating the pressure difference between the motor internal pressure and the external air pressure by the vent hole 74, the fluid lubricant in the annular gap portion 75 is the fluid lubricant in the tapered gap portion 78 communicating with this. With the assumption that the equilibrium state is maintained, the fluid lubricant can be supplied and stored better. The gap size or shape of the annular gap portion 75 is preferably set so that the fluid lubricant is balancedly held in the tapered gap portion 78.

The action of supplying / storing the fluid lubricant to / from the annular gap portion 75 is smoother in the state where the surface tension of the annular gap portion 75 and the tapered gap portion 78 are balanced as described above. Therefore, in this embodiment, the fluid surface width of the fluid lubricant in the tapered gap portion 78 is, for example, 0.
2 mm, the gap width of the annular gap 60 is set to 0.1 mm, and the inner diameter of the cross section of the annular gap portion 75 is set to 0.4 mm. That is, it is desirable that the width of the annular gap 60 is set to be the smallest and the sectional width of the annular gap 75 is set to be the largest. Further, as shown in the drawing, since the opening of the tapered gap portion 78 is provided inward in the radial direction, the tapered gap portion 78 can be opened even if the centrifugal force accompanying the rotation of the rotor 3 is received. Inner peripheral portion 5 of thrust cover 6 (on the radially outer side) to be formed
Since 7 is held so as to surround the fluid lubricant, leakage of the fluid lubricant from the tapered gap 78 is further prevented.

Further, since the cross-sectional shape of the connecting portion 76 between the vent hole 74 and the annular gap portion 75 is set to be larger than the radial cross-sectional shape of the annular gap portion 75, the fluid lubricant acts on the surface tension. In response to this, leakage from the vent hole 74 is prevented. And further, the vent holes 74
Is positioned on the inner peripheral side (shaft 2 side) of the annular gap 75, so that the fluid lubricant is further prevented from leaking from the vent hole 74 against the rotational centrifugal force of the rotor 3.

A through hole 90 provided in the vicinity of the shaft 2 side of the thrust plate 5 serves to ventilate between the thrust dynamic pressure bearing portions C and D, so that the pressure difference between the fluid lubricant communicating with the radial dynamic pressure bearings A and B is increased. It is provided to solve the problem.

As described above, in the embodiment of the motor shown in FIGS. 1 and 2, the annular gap 75 is formed by being cut out on the thrust cover 6 side, but conversely, FIG.
As shown in FIG. 3, it may be formed by cutting out on the sleeve 4 side (upper end portion 71) (FIG. 3 (a)), or by forming a notch in both sides to form an annular gap portion 75 (FIG. 3).
(B)) may be performed. In the illustrated example, the cross-sectional shape of the annular gap 75 is an arcuate shape or a circular shape, but various shapes such as a square shape and other polygonal shapes can be adopted depending on one of the thrust cover 6 side and the sleeve 4 side or a combination of both. it can.

Although the vent hole 74 is provided at one location on the thrust cover in the illustrated example, it may be provided at two locations or more in a 180-degree rotational symmetry. At this time, it is desirable that the rotors 3 are arranged in a rotationally symmetrical manner on the thrust cover in consideration of the rotational dynamic balance of the rotor 3.

The annular gap portion 75 and the thrust dynamic pressure bearing portion C,
In the illustrated example, the joint portion 77 communicating with D is formed with a clearance (axial direction) over the entire circumference between the thrust cover 6 and the sleeve 4, but in addition to this, as shown in FIG. The communication passage 80 may be provided. In this case, the communication passage 80 may be formed in the notch shape on the thrust cover 6 side or the sleeve 4 side, or the communication passage 80 may be formed by a combination of both.

FIG. 5 is an enlarged sectional view showing the vicinity of the lower part of the motor of FIG. In FIG. 5, a tapered gap portion 82 is formed between the outer peripheral portion 19 of the shaft 2 and the inner peripheral portion 31 of the sleeve 4 on the motor outer side (lower side in the figure). The tapered gap portion 82 is formed such that the inner peripheral portion 31 of the sleeve 4 is formed substantially parallel to the axial direction and the diameter is sequentially reduced on the shaft 2 side. The fluid lubricant that communicates with the radial dynamic pressure bearing portion B is held in the gap portion 82. Therefore, also in this case, the fluid lubricant is prevented from leaking to the outside of the motor (in this case, the lower side in the drawing), as in the tapered gap 78 formed on the upper side of the motor. Further, since the opening of the tapered gap portion 82 is formed facing the shaft 2 side, that is, the inner side in the axial direction, it is needless to say that leakage can be further prevented.

Next, FIG. 6 is a sectional view showing a motor of another embodiment according to the present invention, showing the left half of the motor. In this embodiment, the rotor 103 is formed integrally with the shaft 102 and is rotatably supported by a cylindrical portion (sleeve) 104 formed in the housing 101. In the motor shown in FIG. 1, the shaft 2 is fixed to the housing 1, whereas in FIG. 6, the shaft 102 and the rotor 103 rotate relative to the housing 101. In FIG. 6, radial dynamic pressure bearing portions filled with a fluid lubricant are provided in portions A and B where the inner peripheral portion of the sleeve 104 and the outer peripheral portion of the shaft 102 face each other in the radial direction.

Between the thrust plate 105 fixed to the lower end of the shaft 102 and the thrust cover 106, C,
Further, a thrust dynamic pressure bearing portion filled with a fluid lubricant is provided between the thrust plate 105 and the lower end portion of the sleeve 104 by D. A stator 107 is mounted on the outer peripheral side of the sleeve 104, and a rotor magnet 108 is mounted on the inner peripheral portion of the rotor 103 that faces the sleeve 107 in the radial direction.
Is installed.

According to this embodiment, the thrust cover 106
An annular gap portion 112 is provided in a joint portion 111 joined to the lower end 110 of the step portion of the housing 101. A vent 113 is provided near the annular gap 111. On the other hand, on the outer side of the motor on the radial dynamic pressure bearing portion A side (upper side in the drawing), the gap between the outer peripheral portion 119 of the shaft 102 and the inner peripheral portion 131 of the sleeve 104 becomes larger as the motor goes outward. Are formed. The tapered gap 114 has a radial dynamic pressure bearing portion A.
A fluid lubricant in communication therewith is retained.

The fluid lubricant held in the tapered gap 114 is kept in equilibrium with the fluid lubricant inside the sleeve, and basically functions like the motor of FIG. That is, it has a sealing function of preventing the fluid lubricant from leaking out of the motor. And like the motor in FIG.
The fluid lubricant in the annular gap 112 functions to supply and store according to the amount of the fluid lubricant retained in the dynamic pressure bearing portion. Further, the air hole 113 eliminates a pressure difference between the dynamic pressure bearing portion and the outside of the motor. Further, the cross-sectional shape of the connecting portion 120 between the annular gap portion 112 and the ventilation hole 113 is larger than the cross-sectional shape of the annular gap portion 112. These configurations have the same effects as the motor shown in FIG. Needless to say, the various configurations used in the motor of FIG. 1 and combinations thereof can be applied to the motor of this embodiment. Although the embodiment of the motor of the present invention has been described above, the design can be freely changed without departing from the gist of the present invention.

[0039]

Since the motor of the present invention has the above-mentioned structure, it has the following effects. That is, according to the motor of the first aspect of the present invention, the annular gap portion 75 or 112 is provided on the rotor 3 side which is the rotating member or the housing 101 side which is the fixed member, and the annular gap portion is movable. The surplus fluid lubricant, which communicates with the fluid lubricant interposed in the pressure bearing portions A to C and cannot be retained by these dynamic pressure bearings, is retained. Therefore, when the fluid lubricant intervening in the dynamic pressure bearing means is insufficient, the annular gap (75, 112)
Fluid lubricant is supplied to these hydrodynamic bearing means,
It is possible to prevent exhaustion of the fluid lubricant in the bearing portion. Further, the air holes 74 and 113 eliminate the pressure difference inside the motor, and the tapered gaps 78 and 8 are formed.
2, 114 and the like can prevent the fluid lubricant from leaking out of the motor.

Further, according to the motor of the second aspect of the present invention, since the tapered gaps 78, 82, 114 and the like are provided with their openings directed in the radial direction, leakage of the fluid lubricant is prevented. More prevented. Furthermore, according to the motor of the third aspect, the ventilation holes 74, 113 and the annular gap portion 75,
The cross-sectional shape of the connecting portions 76 and 120 with the 112 is
Since it is set to be larger than the radial cross-sectional shape of the annular gap portions 75 and 112, the fluid lubricant is prevented from leaking from the ventilation holes 74 and 113 under the action of surface tension. Still further, according to the motor of the fourth aspect, the ventilation holes 74 and 113 are positioned inward of the annular gap portions 75 and 112 in the radial direction.
The fluid lubricant is prevented from leaking from the vent holes 74 and 113 even when subjected to the action of centrifugal force due to the rotational drive of the.

As described above, according to the motor of the present invention, leakage and depletion of the fluid lubricant interposed in the dynamic pressure bearing portion can be prevented, and highly accurate bearing support can be realized. It is possible to obtain a motor that can be downsized and can be rotated at high speed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an entire motor according to an embodiment of the present invention.

2 is an enlarged view of a main part of the electric motor of FIG. 1, (a) is a plan view, and (b) is a sectional view.

FIG. 3 is a partial cross-sectional view of a motor showing another embodiment.

FIG. 4 is a partial plan view of a motor showing still another embodiment.

5 is an enlarged view of a main part of the motor shown in FIG.

FIG. 6 is a sectional view of a motor according to another embodiment of the present invention.

[Explanation of symbols]

 1 Housing 2 Shaft 3 Rotor 4 Sleeve 5 Thrust Plate 6 Thrust Cover 7 Stator 8 Rotor Magnet 10 Hub A, B Radial Dynamic Pressure Bearing C, D Thrust Dynamic Pressure Bearing

Claims (4)

[Claims] 1. A motor comprising a housing, a rotor rotatably supported with respect to the housing, and a hydrodynamic bearing means formed by a fluid lubricant interposed between the housing and the rotor, wherein: On the outer side of the motor that is continuous with the pressure bearing means, there is a tapered gap portion in which the radial gap between the housing and the rotor increases with the outside of the motor, and the fluid lubricant in the tapered gap portion is external to the motor. Is equilibrated with the atmospheric pressure of the housing, the housing or the rotor is provided with an annular gap portion communicating with a fluid lubricant, and the annular gap portion is provided with a vent hole for communicating with the atmosphere. Excess fluid lubricant that cannot be retained by the means is retained and retained in the annular gap portion, and when the fluid lubricant intervening in the dynamic pressure bearing means is insufficient, Part of the fluid lubricant is supplied to the dynamic pressure bearing means,
A motor characterized by the following. 2. The motor according to claim 1, wherein an opening of the tapered gap portion is provided radially inward. 3. The cross-sectional shape of the connecting portion between the vent hole and the annular gap portion is set to be larger than the radial cross-sectional shape of the annular gap portion.
Motor described. 4. The motor according to claim 3, wherein the vent hole is positioned radially inward of the annular gap portion.