JP2641035B2 - Motor with hydrodynamic bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor. More specifically, the present invention relates to a motor including a hydrodynamic bearing.

[0002]

2. Description of the Related Art Conventionally, for example, as shown in FIG.
Spindle motors using hydrodynamic bearings are known to those skilled in the art. In a known spindle motor 1 using a hydrodynamic bearing as shown in FIG. 4, a lower end of a shaft 4 is fixed to a boss 3 of a fixed base member 2, and a radius of the boss 3 Stator 5 outside the direction
Is fixed. A small-diameter portion 6 is provided at the upper end of the shaft 4, and a thrust plate 7 is fitted and fixed to the small-diameter portion 6, and the upper surface of the thrust plate 7 is similarly fitted to the small-diameter portion 6. The bush 8 is held. A cover plate 9 is disposed radially outward of the bush 8 and on the upper surface of the thrust plate 7. A sleeve member 10 is provided radially outward of the cover plate 9, and the cover plate 9 and the sleeve member 10 are fixed to each other, and these constitute a shaft holding member.

[0003] Further, a part of the sleeve member 10 holds the thrust plate 7 and the thrust plate 7 therefrom.
Of the radial dynamic pressure fluid bearing means 12 formed in the middle of the shaft 4. Further, the sleeve member 10 is the stator 5
The rotor magnet 13 is supported at a position opposite to the stator 5 in the radial outward direction. Furthermore, the sleeve member 10 has a hub 14 radially outward,
The hub 14 holds a magnetic disk (not shown). Oil is interposed between the upper surface of the thrust plate 7 and the lower surface of the cover plate 9 and between the lower surface of the thrust plate 7 and the sleeve member 10 to constitute thrust hydrodynamic bearing means. Member 1
Oil is intervened between 0 and 0 to form radial dynamic pressure fluid bearing means.

[0004]

However, in such a spindle motor, since it rotates at an extremely high speed during operation, oil flows radially outward due to centrifugal force in the thrust hydrodynamic bearing means. The oil in the thrust hydrodynamic bearing means tends to be insufficient. If there is insufficient oil in the thrust hydrodynamic bearing means, the thrust plate and the sleeve member come into metallic contact, and there is a risk that seizure may occur in the bearing means. Also, in this type of motor, a reservoir for holding extra oil,
That is, there was no so-called oil reservoir. For this reason, it is necessary to strictly measure the amount of oil interposed in the bearing portion. If the amount of oil is larger than a predetermined value, there is a risk that excess oil leaks from the bearing portion to the outside. In addition, since it is impossible to retain excess oil in the bearing portion in advance in this way, if the bearing is used for a long time, the oil evaporates, but in such a case, the oil in the bearing portion decreases, The life of the bearing may be shortened.

An object of the present invention is to solve the above-mentioned problems and to provide a motor having a hydrodynamic bearing means capable of preventing seizure due to oil shortage at the time of high-speed rotation.

[0006]

In the motor of the present invention, an annular space is defined between the outer peripheral surface of the thrust plate and the inner peripheral surface of the shaft holding member, and excess oil is contained in a part of this annular space. is, the scan last plate is provided with a communication hole for communicating the annular space to the atmosphere, when the motor is not rotating, the oil in the annular space accumulates in its lower, the motor is rotating at high speed Sometimes, this oil is held on the inner peripheral surface of the shaft holding member, and the oil of the thrust hydrodynamic bearing means on the upper surface side of the thrust plate and the lower surface side of the thrust plate via the oil held on the inner peripheral surface. And the oil of the thrust hydrodynamic bearing means is in a continuous state.

[0007]

In the motor of the present invention, surplus oil is stored in a part of the annular space defined between the outer peripheral surface of the thrust plate and the inner peripheral surface of the shaft holding member. Therefore, a part of the annular space functions as a reservoir for excess oil, and the remaining part of the annular space functions as an air chamber. This air chamber is communicated with the atmosphere through the communication hole, and the air in the air chamber expands due to a temperature change. At times, this air is discharged to the atmosphere through the communication hole. Further, in the motor of the present invention, when the motor rotates at high speed, the oil of the thrust hydrodynamic fluid bearing means on the upper and lower surfaces of the thrust plate is continuous via the oil adhered to the inner peripheral surface of the shaft holding member by centrifugal force. Becomes Therefore, the centrifugal force acting on the oil held on the inner peripheral surface of the shaft holding member and the component force of the centrifugal force acting on the oil of the thrust dynamic pressure fluid bearing means are balanced, and the thrust dynamic pressure fluid bearing means has Oil is prevented from flowing radially outward due to centrifugal force, and shortage of oil in the thrust hydrodynamic bearing means is prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the essential parts of an embodiment of a motor according to the present invention. In FIG. 1, the illustrated motor includes a shaft 21 whose lower end is fixedly held to a boss (not shown) of a fixed base member. A thrust plate 23 is integrally provided at the upper end of the shaft 21.
A portion of the shaft 21 below the thrust plate 23,
That is, the outer diameter of the first portion 24 is relatively large, while the portion of the shaft 21 above the thrust plate 23, that is, the outer diameter of the second portion 22, is relatively small.
4 is about half of the outer diameter. The thrust plate 2 is located radially outwardly of the second portion 22 of the shaft 21.
A cover plate 25 is disposed above the unit 3. A sleeve member 26 is attached to the cover plate 25, as shown in FIG. Also in this example, the cover plate 25 and the sleeve member 26 are fixed to each other to form a shaft holding member. A part of the sleeve member 26 holds the outer peripheral surface of the thrust plate 23, extends from there to below the thrust plate 23, and further supports the radial dynamic pressure fluid bearing means 27 provided in the middle of the shaft 21. .

The radial hydrodynamic bearing means 27 is composed of a pair of radial bearing grooves 28 and 29 formed in the shaft 21 at intervals in the axial direction.
Alternatively, it may be formed on the inner peripheral surface of the sleeve member 26. A stator 52 is fixedly held on the boss 50 of the base member holding the shaft 21. As shown in FIG. 4, the sleeve member 26 supports a rotor magnet (not shown) at a position facing the stator 52 radially outward of the stator 52. Further, as shown in FIG. 4, the sleeve member 26 has a hub (not shown) radially outward thereof, and a magnetic disk (not shown) is held on the hub. Thus, the thrust plate 23 and the shaft holding members (the cover plate 25 and the sleeve member 2) surrounding the upper surface, the side surface, and the lower surface of the thrust plate 23.
6) and between the thrust dynamic pressure fluid bearing means 54a, 5
4b, and the shaft 21 and the sleeve member 26
Radial dynamic pressure fluid bearing means 27 is provided between and.

In the embodiment, the thrust dynamic pressure fluid bearing means 5
4a and 54b are composed of bearing grooves formed on the upper surface and the lower surface of the thrust plate 23. The bearing grooves of the thrust hydrodynamic bearing means 54a, 54b are replaced with cover plates 2 instead of the thrust plates 23.
5 and / or the sleeve member 26.

In connection with the radial hydrodynamic bearing means 27 and the thrust hydrodynamic bearing means 54a, 54b,
It is configured as follows. That is, between the radially inner portion of the cover plate 25 and the second portion 22 of the shaft 21, an atmosphere passage 31 communicating with the outside of the motor, that is, the atmosphere, is provided.
Is stipulated. The lower surface of the radially inner portion of the cover plate 25 is provided with a tapered portion 32 inclined upward at a predetermined angle (a °) radially inward from the lower surface. Following the tapered portion 32, a concave portion 56 is formed outside thereof.
Is provided, and the recess 56 is provided in the thrust plate 2
The first oil sump space 58 is defined in cooperation with the upper surface of the third oil reservoir 3. It is desirable that the volume of the oil storage space 58 be relatively large so as to sufficiently store excess oil. In the embodiment, a shoulder 60 having a slightly larger diameter is provided at the base of the small-diameter portion 22 of the shaft 21, and the distance between the shoulder 60 and the inner diameter end of the cover plate 25 is set small. Therefore, the taper seal means composed of the taper portion 32 is provided outside the thrust dynamic pressure fluid bearing means 54a provided on the upper surface side of the thrust plate 23, and the shoulder portion 60 is provided outside the taper seal means. And an aperture sealing means constituted by the cover plate 25 and an oil storage space 58 are arranged between the pair of sealing means. The angle a of the tapered portion 32 is preferably 5 to 15 °.

A lower portion of the sleeve member 26 facing the shaft 21 has a tapered portion 3 inclined radially outward at a predetermined angle (b °) toward the lower side of the shaft 21.
7 is provided. Further, the distance between the lower end of the sleeve member 26 and the upper end of the boss 50 is set to be small, and the narrowed portion functions as a diaphragm sealing means. Further, an annular concave portion 62 is provided on an inner peripheral portion of the boss portion 50, and an inner peripheral surface defining the concave portion 62 extends radially outward toward the lower side. The recess 62 is provided in the shaft 2
It is preferable to act as a second oil storage space for storing surplus oil in cooperation with 1 and make the volume relatively large. Note that the angle b of the tapered portion 37 is preferably 5 to 15 °.

As shown in FIG. 1, the thrust hydrodynamic bearing means 54a and 54b are connected to the radial hydrodynamic bearing means 27.
, Ie, the upper surface, the peripheral side surface, the lower surface, and the lower end portion of the shaft 21 are filled with oil (the peripheral side surface of the thrust plate 23 will be described later in detail). In order to prevent oil from leaking from these hydrodynamic bearing means 27 and 54a, 54b, in the embodiment, the maximum interval between the tapered portions 32 and 37 is
The distance is set to be larger than the distance between the shaft 21 and the shaft holding member. This makes it difficult for oil to flow out from the tapered portions 32 and 37.

In connection with the thrust plate 23,
It is configured as follows. Referring to FIG. 2 together with FIG.
The outer peripheral surface of the thrust plate 23 is circular, and the inner peripheral surface of the portion 26a of the sleeve member 26 that receives the thrust plate 23 is also circular, and an annular space 64 is defined between the thrust plate 23 and the portion 26a. . Referring to FIG. 2 as well, oil 66 is contained in a part of annular space 64. The amount of the oil 66 is desirably about half of the annular space 64.
When the amount of oil 6 increases, a communication hole, which will be described later, is closed by oil 66. On the other hand, when the amount of oil 66 decreases, the thrust dynamic fluid
The oil layer that connects between a and 54b is not formed.

The thrust plate 23 is further formed with a pair of communication holes 42 at substantially 180 degrees intervals in the circumferential direction. One end of the communication hole 42 is the thrust plate 2
3 is open to the outer circumferential surface, that is, the annular space 64, and the other end is open to the upper surface of the thrust plate 23. In the embodiment, as clearly shown in FIG. 1, one end opening of the communication hole 42 opens in the axial center of the thrust plate 23, and the other end opening opens in the tapered portion 32. Even if it is fed, the air and oil 66 remain in the tapered portion 32 and the first oil storage space 58 following the tapered portion 32.
The oil 66 is returned to the thrust hydrodynamic bearing means 54a, and the air is discharged to the outside of the motor through the atmosphere passage 31.

The thrust plate 23 is further provided with annular projections 68 and 70 projecting outward in the radial direction at both ends thereof. A pair of annular concave portions 72 and 74 are provided on the inner peripheral surface of the portion 26a of the sleeve member 26 at predetermined intervals corresponding to the annular protrusions 68 and 70. In order to obtain the function and effect described later, for example, the dimensions related to the thrust plate 23 and the like can be set as follows. Distance L1 between the upper surface of the thrust plate 23 and the cover plate 25: approximately 0.01 mm Distance L2 between the lower surface of the thrust plate 23 and the sleeve member 26: approximately 0.01 mm Thickness of the thrust plate 23 (length in the axial direction) L3 :
Approximately 1.4 mm Width W1 of the annular projections 68 and 70: about 0.2 mm Height H1 of the annular projections 68 and 70: about 0.1 mm Width W2 of the annular recesses 72 and 74: Approximately 0.22 mm of the annular recesses 72 and 74 Depth D1: About 0.1 mm Width W3 of the annular space 64: About 0.15 mm

Next, the operation and effect of the above-described motor will be described. When the motor is not rotating, the oil 66 is held in the state shown in FIG. That is, oil 6
6 are gathered at the lower part of the annular space 64 by their own weight, and the thrust hydrodynamic bearing means 5 on the lower surface side of the thrust plate 23
4b and the oil 66c contained in the annular space 64 are continuous.
The oil 66a of the thrust hydrodynamic bearing means 54a on the upper surface side of the thrust plate 23 is kept separated via an air chamber. Further, at least a part of the one end opening of the communication hole 42 located between the annular projections 68 and 70 is located above the oil 66 c in the annular space 64 and communicates with the air chamber of the annular space 64. Therefore, even if the air in the air chamber expands due to a change in temperature or the like, the expanded air will not pass through the communication hole 42, the first oil sump space 58 and the air passage 31.
Through the air to avoid the adverse effects of air expansion.

On the other hand, when the motor is rotating at high speed, the oil 66 is held in the state shown in FIG. That is, the centrifugal force is generated by the high-speed rotation of the sleeve member 26 so that the oil 66a of the thrust hydrodynamic bearing means 54a, 54b,
66b and the oil 66c in the annular space 64, the oil 66c in the annular space 64 is held in a state of being adhered to the inner peripheral surface of the sleeve member 26, and the thrust dynamic pressure fluid on the upper and lower surfaces of the thrust plate 23. Bearing means 54a, 5
The oils 66a and 66b of 4b tend to flow outward in the radial direction. Therefore, as shown in FIG. 3, the oil 66a, 66b of the thrust hydrodynamic bearing means 54a, 54b flows outward in the radial direction and flows to the layer of oil 66c held on the inner peripheral surface of the sleeve member 26. The oil 66a of the upper thrust hydrodynamic bearing means 54a and the oil 66b of the lower thrust hydrodynamic bearing means 54b are:
A continuous state is established via the oil 66c on the inner peripheral surface of the sleeve member 26. In this continuous state, as will be easily understood, the oil 66c held by the sleeve member 26 rotates at a high speed integrally with the oil 66c, so that a relatively large centrifugal force acts. On the other hand, the centrifugal force acting on the oil 66a, 66b of the thrust dynamic pressure bearing means 54a, 54b on the upper and lower surfaces is supported by the inner peripheral surface of the sleeve member 26, and acts on the oil 66c attached to the inner peripheral surface. Thrust force hydrodynamic bearing means 54
a. The flow of oil 66a, 66b of 54b outward in the radial direction is suppressed, and oil shortage during high-speed rotation is prevented. In particular, the annular projections 6 are provided at both ends of the thrust plate 23.
8 and 70, the annular projections 68 and 7 are provided.
The oil 66 whose leading end is held by the sleeve member 26
c to the thrust hydrodynamic bearing means 54a, 5
The continuous state of the oils 66a, 66b of 4b and the oil 66c held on the inner peripheral surface of the sleeve member 26 is maintained. Even during such high-speed rotation, the oil 66 sticks to the inner peripheral surface of the sleeve member 26, so that the one end opening of the communication hole 42 communicates with the air chamber of the annular space 64 as shown in FIG. Communication with is maintained.

The embodiment of the motor according to the present invention has been described above. However, the present invention is not limited to such an embodiment, and various changes and modifications can be made without departing from the scope of the present invention. .

For example, in the illustrated embodiment, two communication holes 42 are provided in the thrust plate 23, but the number of communication holes 42 is not limited to this, and one or three or more communication holes 42 may be provided.

In the illustrated embodiment, a pair of annular recesses 72 and 74 are provided on the inner peripheral surface of the sleeve member 26 so as to correspond to the annular protrusions 68 and 70 of the thrust plate 23. This is because it is more convenient to provide a certain interval for facilitating the injection, and to reduce the loss during rotation. When these need not be taken into account, the annular concave portions 72 and 74 are used. Can be omitted.

[0022]

In the motor of the present invention, the surplus oil 66 is contained in a part of the annular space 64 defined between the outer peripheral surface of the thrust plate 23 and the inner peripheral surface of the shaft holding member. Therefore, a part of the annular space 64 functions as a reservoir for the excess oil 66, and the remaining part of the annular space 64 functions as an air chamber. The air chamber is communicated with the atmosphere through the communication hole 42, and the air changes due to a temperature change. When the room air expands,
This air is discharged to the atmosphere through the communication hole 42. Further, in the motor of the present invention, the thrust dynamic pressure fluid bearing means 54a, 54b on the upper and lower surfaces of the thrust plate 23 via the oil 66c adhered to the inner peripheral surface of the shaft holding member by centrifugal force when the motor rotates at high speed. Oil 66a,
66b is in a continuous state. Therefore, the centrifugal force acting on the oil 66c held on the inner peripheral surface of the shaft holding member and the centrifugal force component acting on the oils 66a, 66b of the thrust hydrodynamic bearing means 54a, 54b are balanced,
Oil 66 of thrust dynamic pressure fluid bearing means 54a, 54b
The a and 66b are prevented from flowing outward in the radial direction by the centrifugal force, and the thrust dynamic pressure fluid bearing means 54a and 54b.
Oil shortage at b is prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a first embodiment of a motor according to the present invention.

FIG. 2 is an enlarged partial sectional view showing a thrust plate of the motor of FIG. 1 and its vicinity.

FIG. 3 is an enlarged partial sectional view corresponding to FIG. 2, showing a state of oil when the motor shown in the figure is rotated at a high speed.

FIG. 4 is a sectional view showing an example of a known motor.

[Explanation of symbols]

 Reference Signs List 21 shaft 23 thrust plate 25 cover plate 26 sleeve member 27 radial dynamic pressure fluid bearing means 32 and 37 taper portion 42 communication holes 54a, 54b thrust dynamic pressure fluid bearing means 64 annular space 66, 66a, 66b, 66c oil 68 and 70 annular Protrusions 72 and 74 annular recess

Claims (12)

(57) [Claims] A thrust plate provided on the shaft; a thrust plate provided between an upper surface and a lower surface of the thrust plate and the shaft holding member; In a motor in which hydrodynamic bearing means are interposed respectively and radial hydrodynamic bearing means are interposed between the shaft and the shaft holding member, the outer peripheral surface of the thrust plate and the inner peripheral surface of the shaft holding member A ring-shaped space is defined between them, excess oil is stored in a part of the ring-shaped space , and the thrust plate is provided with a communication hole for communicating the ring-shaped space with the atmosphere. When the motor is rotating at a high speed, the oil is retained on the inner peripheral surface of the shaft retaining member when the oil is retained in the lower portion of the annular space when it is not rotating. The oil of the thrust dynamic pressure fluid bearing means on the upper surface side of the thrust plate and the thrust dynamic pressure fluid bearing means on the lower surface side of the thrust plate through the oil held on the inner peripheral surface. A motor characterized by being in a continuous state with the oil. 2. An outer peripheral surface of the thrust plate includes a ring.
A ring-shaped projection protruding into the space is provided.
Motor as described. 3. The annular projection is provided at both ends of the thrust plate.
The shaft holding member is provided on the
Correspondingly, a pair of annular recesses are provided at a predetermined interval.
Motor according to claim 2, wherein that. 4. One end of the communication hole is connected to the thrust plate.
There is an opening between the annular protrusions of the
When it is not, the one end opening of the communication hole is located in the annular space.
The upper part of the oil communicates with the atmosphere and the motor rotates at high speed.
The one end opening is the inner peripheral surface of the shaft holding member.
The motor according to claim 3 , wherein a radially inner side of the oil held in the air communicates with the atmosphere . 5. A surplus of the annular space is provided in approximately half of the annular space.
The motor according to any one of claims 1 to 4, wherein oil is stored. 6. The thrust plate on the upper surface side of the thrust plate.
Thrust side sealing means on the outside of the strike hydrodynamic bearing hand stage
Motor according to any one of claims 1 to 5 is provided with. 7. The thrust side sealing means is disposed inside.
Taper seal means and the outer diaphragm
The taper seal means and the throttle seal.
A first oil sump space is defined between the
Motor according to claim 6, wherein that. 8. The outside of said radial hydrodynamic bearing means
Claim radial sealing means are provided 1 to 7
The motor according to any one of the above. 9. The radial side sealing means is disposed inside
Tapered seal means and an externally disposed throttle seal
The taper seal means and the throttle seal.
A second oil sump space is defined between the
The motor according to claim 8. 10. A shaft and a bearing holding mechanism for the shaft.
Shaft holding member and thrust provided on the shaft
And a top plate of the thrust plate and
Thrust dynamic pressure fluid shaft between the lower surface and the shaft holding member
Receiving means are respectively interposed between the shaft and the shaft holding portion.
Motor with radial hydrodynamic bearing means interposed
In Outer peripheral surface of the thrust plate and the shaft holding member
An annular space is defined between the outer peripheral surface and the peripheral surface.
Surplus oil is stored, The thrust plate communicates the annular space with the atmosphere.
There is a communication hole for One end of the communication hole is annular when the motor does not rotate.
The space above the oil in the space communicates with the atmosphere
However, when the motor rotates,
The space created on the outer peripheral surface of the thrust plate is
A motor that communicates. 11. The ring is provided at both ends of the thrust plate.
A pair of annular protrusions projecting into the space,
2. The one end of claim 1 is open between the pair of annular projections.
0 motor. 12. The thrust member is provided on the shaft holding member.
Provided on the plate Corresponding to the pair of annular protrusions,
Claim that a pair of annular recesses are provided at regular intervals
Item 12. The motor according to Item 11.