JP3458048B2 - Hydrodynamic bearing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device suitable for rotationally supporting a rotating body of a motor such as a spindle motor for driving a recording disk which requires high speed and high accuracy.

[0002]

2. Description of the Related Art As a hydrodynamic bearing device having a structure in which a rotary shaft body having a thrust plate portion protruding from a shaft portion is rotatably supported by a fixed sleeve body through a lubricant, US Pat. There are 516,212. This structure will be described below with reference to FIG.

FIG. 2 is a sectional view of a spindle motor for a recording medium (for example, hard disk) driving device, and a circular fitting hole 10a of a base 10 of the recording medium driving device.
The lower outer peripheral portion of the fixed sleeve body 12 is fitted and fixed to.

The fixed sleeve body 12 is coaxially provided with a small-diameter cylindrical sleeve portion 12c above a large-diameter cylindrical base portion 12a via an intermediate portion 12b having an intermediate diameter. The inner peripheral surface of the base portion 12a is formed with a large inner diameter portion that is larger in diameter than the inner diameter of the intermediate portion 12b and that is gradually expanded downward in two steps.
2d and the disk-shaped thrust cover 12e are fitted and fixed in order from below, and the intermediate portion 12b of the fixed sleeve body 12 is fixed.
An annular thrust groove portion 12f having an inward opening in the radial direction is formed in a portion corresponding to. An atmosphere opening hole 12g is provided at the center of the thrust cover 12e.

The rotary shaft body 14 rotatably supported by the sleeve body 12 includes a cylindrical shaft portion 14a and the shaft portion 1
4a has an annular plate-shaped thrust plate portion 14b that projects radially outwardly, and most of the shaft portion 14a including the intermediate portion is sleeve-fitted to the sleeve portion 12c. 14b is housed in the thrust groove portion 12f in an internally fitted state, and the shaft end portion 14c protruding downward from the thrust plate portion 14b is inserted and arranged in the inner peripheral portion of the thrust receiver 12d.

A gap between the inner peripheral surface of the sleeve portion 12c and the outer peripheral surface of the shaft portion 14a, a gap between the thrust groove portion 12f and the thrust plate portion 14b, and an inner peripheral surface of the shaft end portion 14c and the thrust receiver 12d. A lubricant 16 such as oil is continuously filled in the gaps between and. The upper portion of the shaft portion 14a and the shaft end portion 14c corresponding to the upper end opening of the sleeve portion 12 are tapered surfaces 14a1 and 14c1 whose outer peripheral surfaces are reduced in diameter toward the axially outward direction, and are opposed to each other. The gap between the fixed sleeve body 12 and the inner peripheral surface of the fixed sleeve body 12 forms a taper seal portion that expands in diameter toward the outside, and both end interfaces of the lubricant 16 are located in both taper seal portions, so that the surface tension is increased. The lubricant 16 is prevented from flowing out.

An annular groove 14d is formed at a central position of a portion of the shaft portion 14a which is fitted into the sleeve portion 12c. The outer peripheral surfaces of the upper and lower portions of the annular groove 14d of the shaft portion 14a and the corresponding sleeve portion 12c. A radial dynamic pressure generating groove such as a herringbone-shaped groove is formed on one or both of the inner peripheral surfaces of the above, and a pair of upper and lower radial bearing portions are configured. A thrust dynamic pressure generating groove such as a herringbone-shaped groove is formed on one or both of the upper and lower surfaces of the thrust plate portion 14b and the inner surface of the corresponding thrust groove portion 12f to form a pair of thrust bearing portions.

The shaft portion 14a has a first communicating passage 18a which communicates between the inner peripheral portions of the pair of thrust bearing portions, and a second communicating passage 18a which communicates between the upper thrust bearing portion and the pair of radial bearing portions.
A communication passage 18b and a third communication passage 18c that communicates between the radial bearings and the upper end portion of the upper radial bearing portion are formed. These communication passages 18a to 18c are formed in a linear shape and are arranged at the shortest position passing through the shaft center of the shaft portion 14a. This is a device for minimizing the amount of the lubricant 16 to be filled.

A stator 20 is externally fitted and fixed to the outer peripheral portion of the sleeve portion 12c of the fixed sleeve body 12, and a cup-shaped rotor hub 22 is coaxially fixed to the upper end portion of the shaft portion 14a of the rotary shaft body 14. , The cylindrical portion 22 of the rotor hub 22
The annular rotor magnet 24 fixed to the inner peripheral surface of a and the stator 20 face each other in the radial direction with a slight gap therebetween. The disk-shaped recording medium is fixed to the rotor hub 22 with its center hole fitted in the cylindrical portion 22a and placed on the collar-shaped disc mounting portion 22b at the lower end of the cylindrical portion 22a, and the recording medium is integrated with the rotor hub 22. And rotate.

[0010]

In the hydrodynamic bearing device as described above, the communication passages 18 provided in the rotary shaft body 14 are provided.
Since a pair of thrust bearing portions and a pair of radial bearing portions are directly or indirectly communicated with each other by a, 18b, and 18c, a pressure difference does not occur in the low pressure region of each bearing portion, It is possible to expect stable shaft support by dynamic pressure without causing pressure imbalance, but there are the following problems to be solved.

That is, in the hydrodynamic bearing device shown in FIG. 2, the lubricant 16 is sealed by a so-called taper seal, but it is necessary to secure the taper portions in the axial direction above and below the bearing portion. In particular, as described in the above-mentioned US patent, when the taper angle is set to 2 degrees, the axial length of the taper portion becomes very long in order to secure a necessary gap in the interface region of the lubricant 16, so that the bearing The shaft length of the entire device becomes large, resulting in a problem that the motor height becomes large, and there is a drawback that it is difficult to make the device thinner and smaller.

Further, in the recording medium driving device as shown in FIG. 2, the substrate 10 constitutes a part of a partition wall of a clean chamber formed inside the device, and the rotor hub 22 is housed in the clean chamber. On the other hand, the atmosphere opening hole 12g of the thrust cover 12e is opened outside the clean chamber. Therefore, one (upper) of the upper and lower taper seal portions of the hydrodynamic bearing device is opened to the clean chamber, and the other (lower) of the upper and lower taper seal portions is opened to the outside of the clean chamber. Since the clean room is generally isolated from the external environment, when a temperature difference or an atmospheric pressure difference occurs between the clean room and the clean room, the pressure balance between the upper and lower taper seal portions is lost, and the lubricant 16 leaks. There is a risk. Some of them have a ventilation hole with a filter that communicates between the inside and outside of the clean room, but when the pressure difference suddenly changes, the same phenomenon as described above may occur.

The present invention has been made in view of the above problems of the prior art. The object of the present invention is to reduce the axial dimension, and to reduce the temperature difference between the inside and outside of the clean room. An object of the present invention is to obtain a hydrodynamic bearing device in which the lubricant does not flow out due to a pressure difference or the like.

[0014]

In order to achieve the above-mentioned object, a hydrodynamic bearing device of the present invention has a shaft portion and a thrust plate portion that extends radially outward from the shaft portion. The rotating shaft body is formed of a fixed sleeve body having a sleeve portion sleeve-fitted to the shaft portion and an annular thrust groove portion having a radial inward opening that accommodates the thrust plate portion in an internally fitted state, Through the lubricant filled in the gap between the rotating shaft body and the fixed sleeve body, a pair of radial bearings mainly in which the shaft portion and the sleeve portion face each other and a pair of both sides of the thrust plate portion in which the thrust groove portion and the thrust plate portion face each other. The hydrodynamic bearing device is rotatably supported by the thrust bearing portion of the fixed sleeve body, wherein the thrust plate portion is positioned at one end of the shaft portion without the shaft portion protruding from the thrust plate portion. Seal the plate side for moisture The radial bearing and the thrust bearing are continuously filled with the agent, and the rotary shaft body has a radial bearing on the inner peripheral portion of each of the thrust bearings, between the radial bearings, and on the opening end side of the sleeve. It is characterized in that a communication passage communicating with the interface with the outside air of the part is formed.

In this hydrodynamic bearing device, the shaft portion of the rotary shaft body does not protrude from the thrust plate portion, the sleeve portion of the fixed sleeve body is sleeve-fitted to the shaft portion, and the thrust plate portion has the thrust groove portion. Since it is sealed and housed inside, the seal part of the lubricant filled between the rotating shaft body and the fixed sleeve body only needs to be the open end of the sleeve part, and the axial length required for sealing is smaller than in the conventional case. In addition, since the lubricant has only one interface, the sealing performance is not impaired by the pressure difference between the inside and outside of the space where this type of bearing device is used, and stable sealing performance can be secured. I can.

Further, according to the present invention, in the above-described hydrodynamic bearing device, the communication passage includes a first communication passage that communicates between inner peripheral portions of the thrust bearing portion and a thrust bearing portion on the other end side. From a second communication passage that communicates between the peripheral portion and both radial bearing portions, and a third communication passage that communicates between both radial bearing portions and the vicinity of the interface between the radial bearing portion on the open end side of the sleeve portion and the outside air. Is supposed to be. In this case, it is desirable that the second and third communication passages among the first to third communication passages be formed in a straight line shape that passes through the axis of the shaft portion.

According to the present invention, the pair of thrust bearing portions and the pair of radial bearing portions are communicated with each other through the first communication passage, the second communication passage and the third communication passage, and the low pressure regions of the respective bearing portions are communicated with each other. There is no pressure difference and no pressure imbalance between the bearings, and stable shaft support by dynamic pressure can be expected. In particular, since the second and third communication passages are formed in a straight line passing through the shaft center of the shaft portion, this communication passage secures the shortest distance, and the filling amount of the lubricant can be minimized.

Further, according to the present invention, in the above-mentioned hydrodynamic bearing device, the shaft body corresponding to the vicinity of the open end of the sleeve portion is formed with a taper surface having a diameter reduced toward the other end side, and the rotary shaft body and the fixed sleeve are provided. The feature is that the interface of the lubricant filled in the gap with the body exposed to the outside air is positioned on the tapered surface.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIG. 1 is a sectional view of a recording medium driving spindle motor, similar to FIG.
The same reference numerals as those shown in FIG. 2 indicate the same or corresponding ones.

The base 30 of the recording medium driving device is made thinner than the conventional one, and the lower outer peripheral portion of the fixed sleeve body 32 is fitted and fixed in the circular fitting hole 30a of the base 30. . The fixed sleeve body 32 includes a small-diameter cylindrical sleeve portion 12b above a large-diameter cylindrical base portion 32a.
Are provided coaxially, the axial length is smaller than that of the conventional one, and a part of the base portion 32a has a circular fitting hole 3
0a is fitted. A large inner diameter portion that is sufficiently larger than the inner diameter of the sleeve portion 32b is formed on the inner peripheral surface of the base portion 32a. Is fitted and fixed, and the lower side of the fixed sleeve body 32 is hermetically sealed.
An annular thrust groove portion 32d having a radially inward opening is formed at a position corresponding to 2a.

The rotating shaft member 34, which is rotatably supported by the sleeve member 32, includes a cylindrical shaft member 34a and a shaft member 3a.
4a has an annular plate-shaped thrust plate portion 34b that projects outward in the radial direction, and most of the shaft portion 34a above the thrust plate portion 34b is sleeve-fitted to the sleeve portion 32b. The plate portion 34b is housed in the thrust groove portion 32d in an internally fitted state.

These gaps are provided between the inner peripheral surface of the sleeve portion 32b and the outer peripheral surface of the shaft portion 34a, and between the inner peripheral surface of the thrust groove portion 32d and the outer peripheral surface of the thrust plate portion 34b. A lubricant 36 such as oil is continuously filled. A shaft portion 34 corresponding to the upper end opening of the sleeve portion 32b
A taper surface 34a1 is formed on the upper portion of a, the outer peripheral surface of which is reduced in diameter in the axially outward (upward) direction, and the gap between the inner peripheral surface of the opposing sleeve portion 32b is outward. A taper seal portion that expands in diameter as it goes is formed, and the interface of the lubricant 36 is located at this taper seal portion, so that the lubricant 36 is prevented from flowing out due to surface tension.

An annular groove 34d is formed at a central position of a portion of the shaft portion 34a which is fitted into the sleeve portion 32b, and outer peripheral surfaces of upper and lower portions of the annular groove 34d of the shaft portion 34a and the corresponding sleeve portion 32b. A radial dynamic pressure generating groove such as a herringbone-shaped groove is formed on one or both of the inner peripheral surfaces of the above, and a pair of upper and lower radial bearing portions are configured. A thrust dynamic pressure generating groove such as a herringbone-shaped groove is formed on one or both of the upper and lower surfaces of the thrust plate portion 34b and the corresponding inner surface of the thrust groove portion 32d to form a pair of thrust bearing portions.

The shaft portion 34a has a first communication passage 38a which communicates between the inner peripheral portions of the pair of thrust bearing portions, and a second communication passage which communicates between the upper thrust bearing portion and the pair of radial bearing portions.
A communication passage 38b and a third communication passage 38c that communicates between the both radial bearings and the upper end portion of the upper radial bearing portion are formed. The first communication passage 38a is formed in the axial direction, the lower end thereof is opened to the inner peripheral portion of the lower thrust bearing portion, and the upper end thereof is opened to the joint portion of the shaft portion 34a and the thrust plate portion 34b. Further, the second and third communication passages 38b, 38c are formed in a linear shape, and are arranged at the shortest position passing through the shaft center of the shaft portion 34a to minimize the filling amount of the lubricant 36.

In the spindle motor adopting the hydrodynamic bearing device having the above-mentioned structure, the stator 20 fitted and fixed to the outer circumference of the sleeve portion 32b and the rotor magnet 24 of the cup-shaped rotor hub 22 fixed to the shaft portion 34a are provided. When the rotor hub 22 rotates due to the magnetic interaction of the rotating shaft body 34 with respect to the fixed sleeve body 32, the rotating body including the rotating shaft body 34 and the rotor hub 22 is dynamically moved by the radial bearing portions. The thrust member is supported, and the rotating body is supported by the thrust in the thrust direction by dynamic pressure.

In the thrust bearing portion and the radial bearing portion, the first, second and third communication passages 38 are provided between the respective low pressure portions.
Since they are communicated by a, 38b, and 38c, there is no pressure difference between the bearing portions, and stable shaft support is realized.

Although specific examples of the present invention have been described above, the present invention is not limited to the above specific examples, and various changes and modifications can be made without departing from the gist of the present invention.

[0028]

Since the hydrodynamic bearing device of the present invention is constructed as described above, it has the following effects. In the hydrodynamic bearing device according to claim 1, a thrust plate in which a rotary shaft member that is rotatably supported by a fixed sleeve member projects radially outward without protruding from the shaft portion and the shaft end. And the thrust plate portion side of the fixed sleeve body is hermetically sealed, the axial length of the entire bearing device can be made significantly smaller than before, and this is used. The motor can be made smaller and thinner. In addition, since the interface of the lubricant filled in the gap between the fixed sleeve body and the rotating shaft body is improved in one place, even if there is a pressure difference between the inside and the outside in the space in which the motor or the like is accommodated, the conventional lubrication The agent does not leak, stable bearing performance can be exhibited, and long life can be expected.

In the hydrodynamic bearing device according to the second aspect of the invention, since the communication passage formed in the rotary shaft body is constituted by the first to third communication passages that sequentially communicate between the bearing portions, the shaft portion is formed. Compared with the case where a communication structure that penetrates the entire structure is used, the structure becomes simpler. Particularly, as described in claim 3, if the second and third communication passages are formed in a straight line shape that passes through the shaft center of the shaft portion, It is possible to form a communication path that connects the bearing portions with the shortest distance, which facilitates formation of the communication passage and has an advantage that the filling amount of the lubricant can be suppressed to a minimum.

In the hydrodynamic bearing device according to the fourth aspect, the filling lubricating fluid can be sealed by a taper seal having a taper surface, and the taper surface is contracted outward in the axial direction. Since the shaft is formed, the lubricant can be applied to the inside of the bearing by the rotation of the shaft, and good sealing performance can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a spindle motor for driving a hard disk to which a hydrodynamic bearing device of the present invention is applied.

FIG. 2 is a sectional view of a spindle motor showing a conventional example.

[Explanation of symbols]

32 Fixed sleeve body 32b Sleeve part 32d thrust groove 34 rotating shaft 34a Shaft 34b Thrust plate part 36 Lubricant 38a First communication passage 38b Second communication passage 38c Third communication passage

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Claims (4)

(57) [Claims] 1. A rotary shaft body having a shaft portion and a thrust plate portion protruding outward in the radial direction from the shaft portion, wherein a sleeve portion sleeve-fitted to the shaft portion and the thrust plate portion are provided inside. For a fixed sleeve body having an annular thrust groove portion having a radially inward opening accommodated in a fitted state, via a lubricant filled in a gap between the rotary shaft body and the fixed sleeve body,
A hydrodynamic bearing device that is rotatably supported mainly in a pair of radial bearings where the shaft portion and the sleeve portion face each other and a pair of thrust bearing portions on both sides of the thrust plate portion where the thrust groove portion and the thrust plate portion face each other. The thrust plate portion is located at one end of the shaft portion without the shaft portion protruding from the thrust plate portion, and the thrust plate portion side of the fixed sleeve body is sealed so that the lubricant is the radial bearing. Part and the thrust bearing part are continuously filled, and the rotary shaft body has inner peripheral parts of the thrust bearing parts, between the radial bearing parts, and an open end of the sleeve part. A fluid dynamic bearing device, characterized in that a communication passage is formed which communicates with the vicinity of the interface of the radial bearing portion on the side with the outside air. 2. The first communication passage, which communicates between the inner peripheral portions of the thrust bearing portion, the inner peripheral portion of the thrust bearing portion on the other end side, and the radial bearing portions. 2. A second communication passage that communicates with each other, and a third communication passage that communicates between the both radial bearing portions and a vicinity of an interface between the radial bearing portion on the open end side of the sleeve portion and the outside air. Hydrodynamic bearing device. 3. The method according to claim 2, wherein among the first, second and third communication passages, at least the second and third communication passages are formed in a straight line passing through the axis of the shaft portion. Hydrodynamic bearing device. 4. The shaft body corresponding to the vicinity of the open end of the sleeve portion is formed with a taper surface whose diameter decreases toward the other end side.
The hydrodynamic bearing device according to claim 1, wherein an interface of a lubricant filled in a gap between the rotary shaft body and the fixed sleeve body, which is exposed to the outside air, is located on the tapered surface.