JP3597894B2 - Motor with hydrodynamic bearing means - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a motor. More specifically, the present invention relates to a motor including a hydrodynamic bearing.
[0002]
[Prior art]
Heretofore, those skilled in the art have known spindle motors using hydrodynamic bearings, for example, as shown in FIG. 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 The stator 5 is fixed outward in the direction. 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 above 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. Furthermore, a part of the sleeve member 10 holds the thrust plate 7 and extends therefrom below the thrust plate 7, and this sleeve part 11 is provided with a radial hydrodynamic bearing means 12 formed in the middle of the shaft 4. I support it. The sleeve member 10 supports the rotor magnet 13 at a position facing the stator 5 radially outward of the stator 5. Furthermore, the sleeve member 10 has a hub 14 radially outward, and 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. The oil is interposed between the member 10 and the radial dynamic pressure fluid bearing means.
[0003]
[Problems to be solved by the invention]
In such a spinned motor, since it rotates at an extremely high speed during operation, some air is mixed at the oil boundary surface between the thrust hydrodynamic bearing means and the radial hydrodynamic bearing means, thereby causing oil mist. (Particles of oil) may be generated and may enter the disk chamber. When the oil mist enters the disk chamber, the oil mist adheres to the surface of the disk member as a recording member, and the head for writing and / or reading information recorded on the disk member easily adheres to the disk surface, This causes so-called head stiction.
[0004]
An object of the present invention is to solve the above-described problems and to provide a motor including a hydrodynamic bearing means capable of preventing an oil mist from entering a disk chamber.
[0005]
[Means for Solving the Problems]
In the present invention, a shaft, a shaft holding member that holds the shaft as a bearing, and a thrust plate provided on the shaft, wherein a thrust hydrodynamic bearing means is provided between the thrust plate and the shaft holding member. In the motor having the hydrodynamic bearing means interposed and having the radial hydrodynamic bearing means interposed between the shaft and the shaft holding member, the motor is provided for guiding the outside of the seal portion of the hydrodynamic bearing means into the motor. A communication hole is provided.
[0006]
[Action]
In the motor of the present invention, a communication hole for guiding the outside of the seal portion of the hydrodynamic bearing means to the inside of the motor is provided. Therefore, when the shaft and the thrust plate are relatively rotated, there is a tendency that the air flow directed from the sealing portion outside the internal motor by the centrifugal force arising by the relative rotation occurs. When the air flow is generated, air outside the seal portion flows into the motor through the communication hole, and air containing oil mist outside the seal portion is guided into the motor and is prevented from entering the disk chamber. You.
[0007]
【Example】
FIG. 1 shows a main part of an embodiment of the motor of the present invention. In FIG. 1, the illustrated motor includes a shaft 24 whose lower end is fixedly held to a boss 22 of a fixed base member 20. At the upper end of the shaft 24, a thrust plate 26 projecting outward in the radial direction is integrally provided. The thrust plate 26 may be formed separately from the shaft 24 and attached to the shaft 24. A cover plate 28 is disposed radially outward of an upper end portion of the shaft 24 (specifically, a portion of the shaft 24 above a portion where the thrust plate 26 is provided) and above the thrust plate 26. Have been. The sleeve member 30 is attached to the cover plate 28. The cover plate 28 and the sleeve member 30 are fixed to each other to form a shaft holding member. A portion of the sleeve member 26 holds the peripheral side surface of the thrust plate 26 and extends therefrom below the thrust plate 26, and further supports a radial hydrodynamic bearing means 32 provided in the middle of the shaft 24. . The radial hydrodynamic bearing means 32 is composed of a pair of radial bearing grooves 34 (only one is shown in FIG. 2) formed at intervals in the axial direction of the shaft 24. The bearing groove 34 may be formed on the inner peripheral surface of the sleeve member 39 instead of the shaft 24.
[0008]
A stator 36 is fixedly held on the outer peripheral surface of the boss 22 of the base member 20 holding the shaft 24. A rotor magnet 38 is provided at a position facing the stator 36 radially outward of the stator 36. A hub member 40 is fixed to an upper end of the sleeve member 26, and a lower end of the hub member 40 extends downward outside the sleeve member 26. The rotor magnet 38 is mounted on the inner peripheral surface of the lower end portion of the hub member 40 via a yoke member 42. A plurality of magnetic disks (not shown) as recording disks are mounted on the outside of the hub member 40 at predetermined intervals in the vertical direction.
[0009]
In the embodiment, a thrust hydrodynamic bearing means 50 is provided between the thrust plate 26 and a shaft holding member (the cover plate 28 and the sleeve member 30) surrounding the upper surface, the side surface, and the lower surface of the thrust plate 26. A radial hydrodynamic bearing means 32 is provided between the shaft 24 and the sleeve member 26. More specifically, the thrust hydrodynamic bearing means 50 comprises thrust bearing grooves formed on the upper and lower surfaces of the thrust plate 26. The bearing groove of the thrust hydrodynamic bearing means 50 may be formed in the cover plate 28 and / or the sleeve member 30 instead of the thrust plate 26. In FIG. 3, the thrust bearing groove provided on the upper surface of the thrust plate 26 is omitted.
[0010]
As shown in FIG. 2, in the motor of the embodiment, a portion of the sleeve member 30 facing the corner of the thrust plate 26 and the shaft 24 is partly cut off in a triangular shape. An air chamber 52 is defined in the section. The air chamber 52 may be formed by cutting out a part of the thrust plate 28 in order to increase the volume.
[0011]
Referring to FIG. 2 together with FIG. 1, the radial dynamic pressure fluid bearing means 32 and the thrust dynamic pressure fluid bearing means 50 are further configured as follows. That is, a passage 56 communicating with the disk chamber 54 is defined between the radially inner portion of the cover plate 28 and the upper end of the shaft 24. On the lower surface of the radially inner portion of the cover plate 28, there is provided a taper portion 58 which is inclined upward at a predetermined angle (a °) radially inward therefrom. Thereby, a space 60 is formed between the lower surface portion of the cover plate 28 in the radial direction, the upper surface of the thrust plate 28, and the shaft 24. It is desirable that the angle a of the tapered portion 58 functioning as a so-called seal portion is 5 ° to 10 °.
[0012]
The lower portion of the sleeve member 30 facing the shaft 24 is provided with a tapered portion 62 inclined at a predetermined angle (b °) radially outward toward the lower side of the shaft 24 . Is the angle b of the tapered portion 62 functioning as a seal portion, for example, 5 °? Preferably, it is 10 °.
[0013]
As shown in FIGS. 1 and 2, the thrust hydrodynamic bearing means 50 and the radial hydrodynamic bearing means 32 are filled with oil. That is, oil is interposed on the upper surface, the peripheral side surface, and the lower surface of the thrust plate 28, and oil is interposed on a portion of the shaft 24 below the thrust plate 26. In the embodiment, the maximum distance between the tapered portions 58 and 62 is larger than the distance between the shaft 24 and the shaft holding member (the cover plate 28 and the sleeve member 30) so that oil does not leak from the tapered portions 58 and / or 62. This makes it difficult for oil to flow out of the tapered portions 58 and 62.
[0014]
In connection with the thrust plate 26, it is further configured as follows. Referring mainly to FIGS. 2 and 3, an annular space 64 is defined between the outer peripheral surface of thrust plate 26 and the inner peripheral surface of sleeve member 30 opposed thereto. The thrust plate 26 is circular, and the inner peripheral surface of the sleeve member 30 is also circular, so that the annular space 64 extends in the circumferential direction with substantially the same width, and has a width of 0.1 to 0.2 mm. It is preferred to be on the order of magnitude.
[0015]
An air chamber 66 is provided in a part of the annular space 64, in the embodiment, at a portion located at the right end in FIGS. 1 to 3. A substantially semicircular concave portion 68 is provided on the inner peripheral surface of the sleeve member 30, and an air chamber 68 is defined by the concave portion 68. With this configuration, as clearly shown in FIG. 3, in the air chamber 68, the gap between the outer peripheral surface of the thrust plate 26 and the inner peripheral surface of the sleeve member 30 is large, so that oil substantially exists except for the bottom thereof. Although there is no oil (air is present), oil exists in a region of the annular space 64 except the air chamber 68.
[0016]
The sleeve member 30 has a first communication hole communicating the air chamber 68 with the inside of the motor. In the embodiment, the sleeve member 30 is provided with a recess 70 extending toward the air chamber 66, and a pipe member 72 is press-fitted into the bottom of the recess 70. The inside of the pipe member 72 defines a first communication hole, one end of which opens into the air chamber 66, and the other end opens into the inside of the motor (the space in which the stator 36 and the rotor magnet 38 are housed) through the recess 70. ing. It is desirable that one end of the pipe member 72 protrudes considerably into the air chamber 66. This configuration effectively prevents oil in the annular space 64 from leaking into the motor through the first communication hole. You.
[0017]
Further, it is preferable to provide an oil adsorbing means 74 in the concave portion 70 of the sleeve member 30. The oil adsorbing means 74 can be composed of, for example, an oil absorbing filter, and is inserted into the recess 70. By providing the oil adsorbing means 74, oil mist that enters the motor through the pipe member 72 can be reliably removed.
[0018]
Further, a second communication hole 76 is provided in the thrust plate 26. One end of the second communication hole 76 opens on the outer peripheral surface of the thrust plate 26 and communicates with the air chamber 66. The other end of the second communication hole 76 branches in the vertical direction, one of which is opened on the upper surface of the thrust plate 26, and the other side of the space 60, specifically, the outside of the tapered portion 58 of the thrust hydrodynamic bearing means 50. (Outside the oil boundary surface of the tapered portion 58), and the other side is opened to the lower surface of the thrust plate 26 and communicates with the second air chamber 52. Therefore, the air chamber 52, the cavity 60, and the air chamber 66 communicate with each other through the second communication hole 76.
[0019]
Although the air chamber 52 is provided at the corner between the thrust plate 26 and the shaft 24 in the embodiment, the air chamber 52 can be omitted in the case of a small motor or the like. In this case, the second communication hole 76 only needs to communicate the air chamber 66 and the space 60.
[0020]
The operation and effect of the above-described motor are as follows.
When the sleeve member 30 rotates relative to the shaft 24, the air in the air chamber 66 flows into the motor through the pipe member 72 due to the action of the centrifugal force generated by the relative rotation, and the air chamber 66 becomes negative pressure. Tend to be. When this tendency occurs, the air in the air chamber 52 and the air space 56 flows into the air chamber 66 through the second communication hole 76, and is further guided into the motor through the pipe member 72. Therefore, the air in the air chamber 52 and the air in the space 60 (these airs contain oil mist from the oil boundary) do not flow out to the disk chamber 54 through the passage 56 and Collected inside the motor through the communication hole 76, thereby preventing an adverse effect due to oil mist outflow. Further, the air flowing into the motor from the air chamber 66 is guided through the oil adsorbing means 74, so that the oil mist contained in the air is adsorbed by the adsorbing means 74 and the interior of the motor substantially contains oil. No air is supplied, and no problem occurs if such air subsequently flows out between the base member 20 and the hub member 40 into the disk chamber 54.
[0021]
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.
[0022]
For example, in the illustrated embodiment, the air chamber 66 provided in the annular space 64 and the inside of the motor communicate with each other through the first communication hole. Instead, the second air chamber 52 and the inside of the motor communicate with each other. May be communicated via the first communication hole.
[0023]
Further, for example, in the illustrated embodiment, the second communication hole 76 is provided in the thrust plate 26, but instead, the second communication hole 76 that communicates the space 60 and the air chamber 66 is covered. The member 28 may be provided. Furthermore, in the illustrated embodiment, the present invention is applied to a fixed shaft type motor. However, the present invention can be similarly applied to a rotary shaft type motor.
[0024]
【The invention's effect】
In the motor of the present invention, a communication hole for guiding the outside of the seal portion of the hydrodynamic bearing means to the inside of the motor is provided. Therefore, when the shaft and the thrust plate rotate relative to each other, the relative rotation tends to generate an airflow from the outside of the seal portion toward the inside of the motor. When the air flow is generated, air outside the seal portion flows into the motor through the communication hole, and air containing oil mist outside the seal portion is guided into the motor. Therefore, the air containing the oil mist is prevented from entering the disk chamber, and the occurrence of head stiction or the like 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 sectional view showing a thrust plate of the motor of FIG. 1 and its vicinity;
FIG. 3 is a sectional view taken along line XX in FIG. 2;
FIG. 4 is a sectional view showing an example of a known motor.
[Explanation of symbols]
Reference Signs List 20 base member 24 shaft 26 thrust plate 28 cover member 30 sleeve member 32 radial dynamic pressure fluid bearing means 50 thrust dynamic pressure fluid bearing means 52 air chamber (second air chamber)
64 annular space 66 air chamber 68 recess 74 oil suction means 76 second communication hole

Claims (7)

A shaft, a shaft holding member that holds the shaft as a bearing, and a thrust plate provided on the shaft, wherein a thrust hydrodynamic bearing means is provided between the thrust plate and the shaft holding member. A motor having hydrodynamic bearing means interposed, and radial hydrodynamic bearing means interposed between the shaft and the shaft holding member;
A communication hole is provided for guiding the outside of the seal portion of the hydrodynamic bearing means to the inside of the motor, and air outside the seal portion is formed by centrifugal force generated by relative rotation of the shaft and the shaft holding member. A motor provided with hydrodynamic bearing means, which is fed into the motor through a communication hole. Between the outer peripheral surface of the thrust plate and the inner peripheral surface of the shaft holding member, an annular space having an air chamber in at least a part thereof is defined. The communication hole and a second communication hole communicating with the outside of the seal portion of the hydrodynamic bearing means are communicated with each other, and the air outside the seal means is caused to flow by the relative rotation of the shaft and the shaft holding member. 2. A motor provided with the hydrodynamic bearing means according to claim 1, wherein the motor is fed into the motor through the second communication hole, the air chamber, and the first communication hole. 3. A motor provided with hydrodynamic bearing means according to claim 2, wherein a concave portion is provided in a portion of the inner peripheral surface of the shaft holding member facing the thrust plate, and the concave portion defines the air chamber. The dynamic pressure fluid bearing means according to claim 2 or 3, wherein a pipe member that connects the inside of the motor and the air chamber is mounted on the shaft holding member, and the pipe member defines the first communication hole. Motor. The second communication hole is formed in the thrust plate. A motor provided with the hydrodynamic bearing means according to any one of Items 2 to 4. The thrust hydrodynamic bearing means is interposed between the upper and lower surfaces of the thrust plate and the shaft holding member, and a second air chamber is defined corresponding to the shaft and a corner of the thrust plate. 6. A motor provided with hydrodynamic bearing means according to claim 5, wherein one end of said second communication hole opens into said air chamber, and the other end opens outside said seal means and into said second air chamber. 7. A motor provided with a hydrodynamic bearing means according to claim 1, wherein said first communication hole is provided with mist suction means for sucking oil mist.

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