JP2937835B2 - Bearing sealing 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 bearing for rotatably supporting a rotating body on a fixed member through oil.
The present invention relates to a bearing seal device for preventing oil interposed in a bearing portion from leaking outside.

[0002]

2. Description of the Related Art In recent years, general plain bearings, dynamic pressure bearings, etc.
Various bearings using oil as a lubricant for a bearing have been proposed. As an example of a product using such a bearing, there is a fixed shaft type HDD (hard disk drive) motor shown in FIG. In this motor, frame 1
A hub 4 is rotatably mounted via a radial bearing 3 on a fixed shaft 2 fixed to the shaft. Oil is supplied between the fixed shaft 2 and the radial bearing 3 as a rotary lubricant. This oil is attached to the bearing portion and is held by capillary action.

[0003]

As described above, various types of rotating equipment using oil as a lubricant for bearings, such as a rotating shaft of a motor, have a problem of always taking measures against oil leakage. In particular, in the case of a bearing used for a hard disk drive motor (HDD motor) or a laser beam printer motor (LBP motor) that requires a clean environment,
Oil leaks are a serious problem. However, in conventional bearing devices, there have been proposed ones in which oil is simply attached to a gap between bearings, or those in which a special seal mechanism is provided as a measure against oil leakage.
In these conventional techniques, for example, in the case of a dynamic pressure bearing, when the amount of oil as a lubricant is small, there arises a problem that a lubricating function such as dynamic pressure cannot be sufficiently obtained. On the other hand, when the amount of oil is too large, There is a problem that oil leakage occurs, and a sufficient bearing seal device for preventing oil leakage has not been achieved. In addition, the conventional technology does not provide a bearing sealing device that fully considers external forces such as gravity, vibration, impact, centrifugal force, dynamic pressure, atmospheric pressure, temperature, and other pressures. There was also the problem of being scarce.

The present invention is different from the above-mentioned prior art bearing seal device in that: 1) the bearing has a space capable of absorbing a slight change or movement of the amount of injected oil; , The oil in the space must be stably retained. 2) Even if it receives an external force (gravity, vibration shock, centrifugal force, dynamic pressure, atmospheric pressure, temperature, other pressures), the structure is such that the oil does not easily jump out and can withstand the external force. ) The structure is such that oil is difficult to move. 4) The oil surface on the outlet side outside the bearing is stable and hard to leak. 5) The structure is such that oil is hardly mixed with air. The present invention proposes a sealing device for a bearing in consideration of the following conditions: 1) the bearing portion always holds oil and satisfies required bearing characteristics; and 2) the oil does not leak outside. An object of the present invention is to propose a sealing device for a bearing.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a basic structure having a two-end exit structure in which only two gap changing portions of a bearing portion are provided at both ends. A bearing portion including a radial bearing portion and a thrust bearing portion for rotatably supporting a rotating body with respect to a fixed member is provided, and a gap is provided at two locations outside the bearing portion. A change portion is provided, and oil is filled from one side to the other side of the gap change portion. The gap change portion includes: 1) an inner end of the gap change portion on the bearing portion side; It has a minimum gap and a maximum gap at the outer end of the gap change portion opposite to the bearing portion. 2) When the angle seen from the bearing portion side is the gap inclination angle, the gap from the inner end of the gap change portion To the outer edge of the transition 3) The gap inclination angle is 0 ° or more; 3) The gap change portion outer end is a position where the gap with respect to the opposing surface of the gap change portion is 0.8 mm or less and the gap inclination angle is 45 ° or less; The internal capacity of the gap changing portion is set to 10% or more with respect to the internal capacity between the two gap changing portions and 100% or more with respect to the internal capacity of the radial bearing portion. Means is provided in which the gap interval at the outer end of the change portion is set to be twice or more as large as the gap interval at the inner end of the gap change portion.

Accordingly, the present invention employs an overall both-end structure in which the gap between the bearings is filled with oil so that the gap change portion is only two at both ends. Since the internal capacity of the gap change part is larger than the internal capacity of the radial bearing part, the internal capacity caused by the variation of the oil injection amount, the internal capacity, the floating of the thrust bearing due to rotation, etc. Even if there is a change in the oil capacity due to changes in evaporation, internal mixing air, or the like, the oil is always held in the bearing portion and does not leak out.

Further, since the gap ratio between the inner end and the outer end of the gap changing portion is set to be large, even if air is mixed in on the oil surface portion, it does not move to the bearing portion.
Further, the air naturally moves outward due to the pressure difference due to the gap ratio, and the mixed state is eliminated. Also, from the gap ratio,
The oil is easily stabilized at any position.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the specific embodiments of the present invention, first, the present inventor has disclosed the basic concept of the invention which has been reached as a result of repeated research and which is necessary for understanding the present invention. I do.

From the viewpoint of retaining oil in a bearing, when looking at a structure having outlets in two directions, such as a general radial bearing, first, the oil reduces the capillary suction pressure at the two outlet positions. The position is determined by the balance. This state is a state in which two pressure balances are balanced, and if any pressure is applied from one side, the oil moves to a position where the pressure can be balanced.
For example, if the capillary suction pressure is A and B, the oil moves from the position of A = B to the position of A = B + external pressure,
The balance will be lost.

Hereinafter, an embodiment in which the present invention is applied to an HDD spindle motor will be described in detail with reference to the drawings.

First, a fixed-shaft HDD spindle motor according to an embodiment of the present invention shown in FIG. 1 includes a stator set 12 as a fixing member mounted on a frame 11 side, and , A rotor set 13 as a rotating member assembled in a stacked manner from the upper side in the figure
It is composed of The stator core 121 constituting the stator set 12 is fitted around the outer periphery of a substantially cylindrical core holder 122 positioned and installed on the frame 11, and wound around a salient pole of the stator core 121. The wire 123 is wound.

At the center of the core holder 122, a fixed shaft 124, which is the center of rotation of the motor, is vertically set up toward the upper side in the figure. Hub 131 that constitutes 13
Are rotatably supported via a pair of radial slide bearings 132,132. The hub 131 has a substantially cylindrical body 131a on which the magnetic disk is mounted on the outer periphery, and has a mounting portion 131b at the lower end edge of the body 131a as shown in FIG. The drive magnet 1, which is the rotor magnet of the motor, is attached to the mounting portion 131 b via the back yoke 133.
34 is mounted in an annular shape. Drive magnet 13
Numeral 4 is disposed so as to annularly face the outer peripheral end surface of the stator core 121.

On the other hand, the above-mentioned double radial sliding bearing 13
The intermediate portion 135 between the radial sliding bearings 132 and 132 may be configured as a single component, or may be configured with an annular spacer (bearing collar) interposed therebetween.
They are formed so that they are separated from each other by a certain distance in the axial direction. At this time, the inner peripheral surface of each radial sliding bearing 132 and the outer peripheral surface of the fixed shaft 124 constitute a sliding surface, and a predetermined bearing oil is provided in the substantially cylindrical bearing portion 16 including the sliding surfaces. 17 are continuously filled.

A thrust plate 125 constituting a thrust bearing is attached to an upper end portion of the fixed shaft 124 in the figure, and an annular concave portion 131c for receiving the thrust plate 125 is formed on the hub 131 side. I have. The bearing oil 17 is also continuously filled in the annular recess 131c from the bearing portion 16, and the thrust plate 125 is rotatably accommodated in the annular recess 131c, and supports the rotating body including the hub 131 in the axial direction. Is configured to be performed.

The annular projecting portion 126 of the core holder 122 extends in the axial direction (upward in the figure) by a predetermined amount, and the inner and outer peripheral wall surfaces of the axial projecting portion of the annular projecting portion 126, The outer peripheral wall surfaces of the radial sliding bearing 132 and the intermediate portion 135 on the lower side of the drawing and the inner peripheral wall surface of the hub 131 define a narrow passage 25 having a substantially U-shaped cross section. In contrast, the structure makes it difficult for oil to scatter outside. The narrow passage 25 is formed of a bent passage that communicates with the external space of the motor.

In the embodiment of the present invention, as shown schematically in FIGS. 2 and 10, the gap changing portions 1 are provided at the upper and lower ends of the cylindrical bearing 16 described above.
5 and 15 are provided in two places. The liquid level 17a of the oil 17 as the lubricant of the bearing filled in the substantially cylindrical bearing space (including the thrust bearing portion, the radial bearing portion, and the space therebetween) is located in the gap changing portion 15. Is set.

Here, the gap changing portion 15 is formed as follows. That is, in each of the gap changing portions 15, 15, the innermost end in the axial direction on the bearing portion 16 side is defined as a gap changing portion inner end 15 a, and the bearing changing portion 15 a is moved from the gap changing portion inner end 15 a to the bearing portion 16.
The side, that is, the inner side, is the bearing portion, the outermost end in the axial direction of the gap change portions 15 and 15 is the outer end 15b of the gap change portion, and the outer end 1 of the gap change portion.
The outside in the axial direction of 5b will be referred to as the outside of the gap changing portions 15, 15. Also, the angle α formed by the gap at that position viewed from the inside (the bearing portion 16 side) is defined as the gap inclination angle, α = 0 ° when the gap is parallel to the opposing surface, and the angle α spreading outward is plus, When the angle α that spreads inward is minus, the gaps in the gap change portions 15 and 15 are the narrowest at the gap change portion inner end 15a and the gap change portion outer end 15b.
The gap inclination angle α from the gap changing portion inner end 15a to the gap changing portion outer end 15b is set to 0 ° or more. A gap inclination angle α of 0 ° indicates that there may be an area parallel to the fixed axis 124 in a part of the gap changing portions 15, 15.

The gap changing portion inner end 15a is
In the case where there is a gap in which the gap angle α is negative, the axially outermost end of the gap in which the gap angle α is negative for the first time corresponds. Further, the gap at the gap changing portion outer end 15b needs to be 0.8 mm or less, and a portion exceeding 0.8 mm corresponds to the outside of the gap changing portions 15 and 15, and the gap is 0.8 mm. When the gap inclination angle α of the point is 45 ° or more, 0.8 mm or less and 4
The maximum gap portion satisfying the condition of 5 ° or less is defined as a gap change portion outer end 15b.

In the present invention, the inner capacities of the two gap changing portions 15 (15) (the inner ends 15a, 15
1 to the fixed shaft 1 from the outer ends 15b, 15b
24) is the inner end 1 of both gap changing portions.
The inner capacity of the bearing portion 16 between the pair of radial bearing portions 13a is set to 10% or more of the inner capacity of the bearing portion 16 between the pair of radial bearing portions 13a and 15a.
2, 132 (the radial bearing 132 and the fixed shaft 1)
24 is set to 100% or more with respect to the capacity formed between the gap changing portion 24 and the outer ends 15b, 1
The gap size at 5b is equal to the gap changing portion inner ends 15a, 15a.
It is set to be twice or more the gap size in 5a.

As described above, in the embodiment of the present invention, the oil 17 is continuously filled from the bearing portion 16 to the gap changing portions 15 at both ends, and the gap of the gap changing portion 15 is 0.8 mm or less. The gap inclination angle α of the gap changing portion outer ends 15b, 15b is set to 45 ° or less, and the gap size at the gap changing portion outer ends 15b, 15b is at least twice the gap size at the gap changing portion inner ends 15a, 15a. , Air is less likely to be mixed into the oil 17, and the bearing seal device is stable and hard to leak. That is, the inner ends 15a, 15a and the outer ends 15b,
Since the gap ratio of the gap 15b is increased and the gap inclination angle α is provided, even if air is mixed in the oil surface portion 17a located at the gap changing portions 15, 15, the air is applied to the bearing portion. Air does not move to the outside, and the air naturally moves outward due to the pressure difference due to the gap ratio, and the mixed state is eliminated.

Further, as described above, since the internal capacity of the gap changing portion 15 is larger than the internal capacity of the bearing section 16 and the internal capacity of the radial bearing section 132, the oil injection amount and the Even if there is a variation in the internal capacity of the part 16, or even if there is a change in the internal capacity of the bearing part 16 due to floating or heat generation due to rotation of the rotating body, etc. Even if the amount of the oil 17 changes, the oil 17 is always held in the bearing portion and does not leak out.

On the other hand, in the embodiment of the present invention, the amount of oil to be injected into the bearing portion 16 is, when the internal capacity of the gap change portion 15 is A, from the gap change portion inner ends 15a, 15a when the stationary state is stable. The amount is set to a position between 0.1 A and 0.9 A.

That is, basically, if the oil surface 17a is located in the gap changing portion 15, the oil surface 17a is stably held and does not cause any problem. In order to prevent oil shortage and oil leakage, the oil amount (the position of the oil surface 17a) is filled in the gap changing portion 15 within the above range, so that the performance can be sufficiently maintained in a normally used environment. can do.

Further, in the embodiment of the present invention, as shown in FIG. 10, the contact angle .theta.1 between the thrust plate 125 as a fixing member and the oil 17 in the gap changing portions 15, 15 and the gap change as the rotating member. It is desirable to set the contact angle θ1 between the portion 15 itself and the oil 17 to 15 ° or more. FIG. 10 shows the gap changing section 15 on the upper side of FIG. 2 among the gap changing sections 15 and 15. The fact that the oil surface 17a is located in the gap changing section 15 means that the oil 17 comes into contact with the thrust plate 125 and the gap changing section 15 itself at a certain contact angle θ1, so that the contact angle θ1 becomes 15 ° or more. Set it.

Next, as a result of various researches by the present inventor, in order to prevent oil from leaking to the outside, it is necessary to prevent wet expansion (up phenomenon). Before and after the above, it was also learned that it was necessary to separate the oil, and the details will be described below.

As described above, in order to prevent the wetting expansion (the rising phenomenon), it is necessary to create a state in which the oil does not cause the wetting expansion phenomenon even with a slight change in environment and conditions.
For that purpose, it is necessary to always satisfy the condition (γS <γL + γSL).

That is, when the contact angle between a solid surface and a liquid is considered, the condition for keeping the solid surface and the liquid in equilibrium is γS−γSL = γL cos θ1 (Young's equation). Here, γSL: interfacial tension at the solid-liquid interface (surface tension) γS: surface tension of the solid γL: surface tension of the liquid θ1: contact angle between the solid and liquid, and the equilibrium is determined by the balance of the above three surface tensions.

The point is the value of (γS−γSL) in the above Young's equation, and the energy is reduced 1) (γS> γSL) or 2) increased by replacing the solid surface with the solid-liquid interface (2). γS <γSL) or 3) unchanged (γS = γSL), and 1) when the energy is reduced, the leaked state, that is, the state where the solid-liquid interface is made more stable, 2) The case of 3) is a state in which no leakage occurs, that is, a state where the solid surface remains stable.

The difference between γS and γSL is filled in by γL.
cos θ1 and is balanced by the contact angle θ1 between the solid and the liquid. That is, as (γS−γSL) increases, θ1 decreases, and when (γS> γL + γSL),
Even when the contact angle θ1 between the solid and the liquid becomes 0 °, the balance is not maintained, and the liquid spreads endlessly on the surface of the solid. The phenomenon in which oil as liquid rises on the surface of the shaft as a solid is basically the same as the phenomenon in which oil spreads rapidly when oil is dropped on water.

Considering the problem that oil goes up on the shaft surface, it is (γS> γL + γS
L) is a problem. Since this equation is an energy equation as it is, the surface (γS) of the solid (eg, shaft) is only the surface of the solid (γS).
This means that energy is more stable when a solid-liquid interface (γSL) and a liquid surface (γL) are newly formed on the surface of a solid than when the surface is solid. Therefore, in such a case, it is meant that the so-called solid surface is eliminated, a solid-liquid interface and a liquid surface are newly formed, and the upwardly leaking diffusion does not stop.

In addition, external force (gravity, vibration and impact,
Centrifugal, magnetic, and other pressures), these external forces only act in the direction of changing the curvature of the liquid surface in the form of pressure, changing the equilibrium point relationship. There is no power. Therefore, these forces try to move the position of the equilibrium point by the force of the surface tension of the liquid, but are useless under the above-mentioned rising phenomenon.

As long as the condition (γS> γL + γSL) is satisfied, the rising (leakage diffusion) phenomenon does not stop. To stop the rising phenomenon, (γ
It is necessary to change the condition to S <γL + γSL). Specifically, it is necessary to lower the surface tension of the solid surface. Under the condition (γS <γL + γSL), the external force also acts through the surface tension of the liquid. Generally, a metal surface has a very large surface tension (energy). Normally, several layers of film are formed spontaneously and the surface tension is considerably reduced, but still the surface tension is large,
In some cases, such a condition (γS> γL + γSL) is satisfied, and a rising phenomenon occurs.

Therefore, as a countermeasure for preventing the rising phenomenon, the condition (γS <γL + γSL) is set. Increase the substantial contact angle between the solid surface and the liquid as much as possible. Make good use of external forces. Specifically, corresponding to the above, 1) protect the surface with a material having a surface tension as low as possible, for example, an oil repellent, so that the metal surface does not directly come out of the solid surface; (γL + γSL). 2) Reduce the surface roughness of the solid surface and increase the substantial contact angle between the solid surface and the liquid as much as possible. Avoid gaps, grooves, scratches, irregularities, etc. on the solid surface as much as possible. This is because the larger the surface area, the smaller the actual contact angle becomes. 3) Take measures to apply external force in the direction to pull back the rising phenomenon.

As described above, the larger the contact angle θ1 between the solid and the liquid, the more difficult it is to leak (the stronger the holding power). For this purpose, the contact angle θ1 between the thrust plate 125 or the fixed shaft 124 and the oil 17 and the contact angle θ1 between the gap change unit 15 itself and the oil 17 in both the gap changing parts 15 and 15 are 1
It is necessary to set it to 5 ° or more. Specifically, these conditions can be satisfied by disposing a material having a relatively low surface tension, such as a plastic material, on the surface that comes into contact with the liquid.

For this reason, if the inner wall surfaces of the gap change portions 15, 15 are made of a plastic material having a low surface tension,
A plastic material having a low surface tension is less likely to cause the diffusion of the oil by wetting and is effective in retaining the oil by capillary action, and has stable properties and good workability, so that a practical product can be produced. This plastic material is used for the gap changing portion 15,
15 can be formed on the inner wall surface by using means such as coating or painting. Further, oil repellent treatment or Teflon coating may be applied to the inner wall surfaces of the gap change portions 15, 15.

Further, the oil contact angle θ1 with respect to the thrust plate 125 or the fixed shaft 124 in the gap changing portions 15 and 15 and the oil contact angle θ with the gap changing portion 15 itself.
If the difference from 1 is small, it will be difficult to leak.
It is better to set below.

In this embodiment, in order to reduce the surface roughness of the solid surface, the surface roughness Ra of the inner wall surfaces of the gap changing portions 15 is set to 0.25 μm or less. If there are irregularities on the inner wall surfaces of the gap changing portions 15, 15, the irregularities cause the same state as the capillary phenomenon. Capillary phenomenon is a phenomenon that occurs when the ratio of the surface of the oil surface in contact with the solid to the volume of the oil is large, and the same is true even if there are irregularities or grooves on the surface instead of gaps. For this reason, when the contact angle between the solid and the liquid is θ1 <90 °, if there are irregularities or grooves on the surface, the contact angle changes to a substantially smaller contact angle, which makes it easier to wet. Therefore, by suppressing the surface roughness Ra of the inner peripheral walls of the gap changing portions 15 and 15 to a small value, the substantial contact angle between the solid and the liquid can be increased and leakage can be prevented. Thus, the surface roughness Ra is set to 0.25 μm.
The setting of m or less is applied to the thrust plate 125 side and the fixed shaft 124 side as necessary.

In practice, the contact angle of the oil varies depending on the state of the solid surface, and the once wetted surface is more easily wetted than the non-wetted surface, and the oil contact angle becomes smaller. For example, when a water droplet moves on an inclined and dirty glass surface, the contact angle of the water droplet on the tip side of the glass is large, and the contact angle after the water droplet has moved becomes small. Also, once wetted surface is easy to get wet and water drops fall through the same place. This is due to the difference in the shape and surface tension of the solid surface of the micro part. That is, if the surface has irregularities, even if the contact angle is the same, the curvature greatly changes due to the combination with the inclination of the solid surface, so that, when viewed macroscopically, the balance can be achieved with the contact angle being different. And if the surface tension is uneven, even if the whole oil withdraws and goes,
The oil surrounded by the concave surface or dirt cannot move and is left behind. When the oil is expanded again, it cannot be in a state where the contact angle is large in a macro view, and is connected to the oil remaining before. As a result, the contact angle becomes small, so that it is easy to pass through and once passes through a wet place many times.

With such a solid surface state,
Once, for some reason, the oil is wetted or spilled during oil injection, that part has a small contact angle and a small holding force, making it easy for oil to pass through. For this reason, at the two outlets of the bearing, that is, from the gap changing portions 15 and 15 to the outside, the unevenness (surface roughness) is made as small as possible.
It is necessary to minimize dirt (uneven surface tension).

It is said that the contact angle between the macro (apparent) solid and the liquid when the solid surface has irregularities and uneven surface tension is as follows.

If there are irregularities, smooth (flat)
Assuming that the ratio of the surface area of the actual surface to the surface is r, the macro (apparent) contact angle θW (referred to as the Wenzel contact angle) is: cos θW = rcos θ1 (θ1: micro (true) contact angle) micro The contact angle of the macro becomes .theta.W = 0.degree. If the contact angle of the macro is as large as .theta.1 = 60.degree. (Cos .theta. = 0.5) and r = 2 or more. It will not stop. For this reason, in order to prevent leakage, the surface roughness from the gap changing portion 15 to the outside should be kept as small as possible, and it is preferable to make the mirror surface state.

On the other hand, if the surface tension is uneven, the macro (apparent) contact angle θC (referred to as the Cassie contact angle) is considered to be a composite surface having different surface tensions: cos θC = A1 cos θ1 + A2 cos θ2. Here, A1 and A2 are ratios of areas occupied by different surface tensions, and θ1 and θ2 are micro (true) contact angles of different surface tensions. Even in this case, in order to prevent leakage, the surface roughness from the gap change portions to the outside should be kept as small as possible, and desirably, it should be a mirror surface state.

Next, when a position within 1/2 of the axial length of the gap change portions 15, 15 from the outer ends of the gap change portions 15, 15 is set as a reference position, the position from the reference position to the outside is determined. It is also effective that the inner wall surface is formed of a material or a treated surface having a contact angle θ1 at least 15 ° or more larger than the inner wall surface on the bearing portion 16 side from the reference position. In other words, one way is to increase the contact angle between the solid and liquid to make it difficult to leak, but if the overall contact angle cannot be increased due to some restrictions, only the most necessary parts for holding Is effective even if the contact angle is increased.

Further, the contact angle θ1 at the large diameter side of the gap changing portions 15, 15 ie at the outer ends 15b, 15b.
However, it is also effective to set such that the contact angle is larger than the contact angle at the small diameter side, that is, at the inner ends 15a.

That is, when the rotating member rotates, the centrifugal force acts on the oil in the bearing, so that the gap changing portions 15 and 15 are changed.
The oil pressure on the surface on the large diameter side in the radial direction is higher than that on the surface on the small diameter side. Therefore, when the contact angle is the same on both the large-diameter and small-diameter surfaces, the contact point between the large-diameter solid and the oil surface is more outward than the contact point between the small-diameter solid and the oil surface. This is a condition that easily leaks and easily mixes air. On the other hand, when the contact angle on the large diameter side is increased, the position of the contact point between the solid on the large diameter side and the oil surface and the contact point between the solid on the small diameter side and the oil surface are determined from the equilibrium balance of the contact points and the pressure difference Is small, which is advantageous for oil leakage and air mixing.

The opening directions of the gap changing portions 15, 15 are as follows.
In FIG. 2, the upper gap changing portion 15 opens in a direction toward the center, the lower gap changing portion 15 opens in a direction parallel to the center of rotation, and the opening is set so as not to face outward in the radial direction. Have been. In other words, the centrifugal force to the oil generated by rotation always increases on the side with the larger diameter, so by adopting such a shape, the pressure due to the centrifugal force does not work in the oil leakage direction, and a more stable state can be maintained. it can.

The thrust bearing device according to the present invention comprises:
It is configured to obtain a dynamic pressure in a direction to cancel the centrifugal force. That is, both the centrifugal force and the dynamic pressure are pressures generated when rotation starts, and a stable state can be obtained by a configuration that cancels each other.

Further, in the present invention, the outer end of the dynamic pressure generating groove of the outer radial bearing 132 (the upper end in the case of the upper outlet, the lower end in the case of the lower outlet in the figure) is the inner end 15a of the gap changing portion. Formed. With such a shape, the gap inclination angle α from the bearing portion 16 side is always α
≧ 0 °, so that it becomes difficult for air to be mixed in during oil injection or the like, and even if mixed, a force is applied in the direction of pushing out to the outside, so that a state in which oil is easily held at all times is maintained.

On the other hand, in the embodiment shown in FIG. 3, a gap 151 which satisfies the gap changing portion condition is provided in the radial direction. Thus, the gap 1 in the radial direction
By providing 51, the internal capacity for holding oil can be increased, and in particular, by keeping the axial width of the gap 151 smaller than the width between the gap changing portion outer end 15b and the fixed shaft 124, The oil 17 of 151 is reliably held. In addition, since the radial gap 151 does not have a large dimension in the axial direction, the overall axial dimension is suppressed, and the impact holding force is advantageous. The above gap 15
As long as 1 satisfies the condition of the gap changing portion 15 already described, as shown in FIGS. 4 and 5, a groove-shaped gap 152 is provided in the radial direction in the axial direction or formed as a hole. It is also possible. In addition, a gap that satisfies the gap changing portion condition in the axial direction may be provided for the thrust bearing.

Further, in the embodiment of the present invention, it is preferable that the gap inclination angle α in the gap changing portion 15 is formed substantially constant and the cross section is formed on the inner wall surface having a straight line shape. In addition, since the gap inclination angle α is α> 0 ° at any position, the oil is always applied to the inside and the air is applied to the outside.

Further, in the present invention, at least two-thirds of the gap changing portion 15 in the axial section may be set as a parallel gap (gap inclination angle α = 0 °) within a gap dimension of 0.4 mm. With such a shape, the gap changing portion 1
As a result, more space and space can be obtained, and the variation and change of the oil 17 can be absorbed more, and the gap between the parallel gaps can be suppressed to be small, so that a leak-resistant state is secured.

Further, in each of the embodiments shown in FIGS. 6 and 7, an oil circulation hole 153 for connecting both end portions of the bearing portion 16 may be provided in the fixed shaft 124. The oil circulation hole 153 is formed at the inner end 15 of the gap changing portion.
a and the outer end of the outer bearing are formed so as to communicate between the bearings. That is, since the dynamic pressure generated inside the bearing is very large, if the dynamic pressure becomes unbalanced, an oil leakage pressure may be generated. On the other hand, by connecting the bearing portion 16 and the outside of the bearing portion 16 with the circulation hole 153, the pressure difference due to the dynamic pressure is eliminated, which is effective in preventing leakage. Further, with this configuration, the holding pressure in the gap changing portion 15 can be effectively used.

Further, in the present invention, although not shown, a groove or a ridge extending in the axial direction from the gap changing portion 15 to the outside thereof may be provided. With this configuration, when air is mixed into the oil 17 for some reason, a state where the exchange of the oil 17 and the air can be performed smoothly is created, and the air can be more reliably pushed out. This is because, if there is a groove or a ridge, the oil 17 moves to the narrower gap and the air moves to the wider gap due to surface tension, and the oil and the air are separated. Further, if this groove or ridge is formed to the outside in the axial direction, the oil or oil is formed along this groove or ridge.
Each can be moved in a separated state without air collision,
Oil and air can be exchanged more smoothly.

On the other hand, in each embodiment of the present invention,
The gap change portions 15, 15 are formed as gaps that open at an angle of 45 ° or less from the bearing portion 16 side to the opening side, and the gap inclination angle outside the gap change portions 15, 15 is also 45 ° or less. Extend. In this way, even if the liquid level (oil surface) 17a of the oil 17 rises from the position of the gap change portions 15, 15 where the oil 17 was originally planned, the gap change portion 1
A stable state is obtained between the solid surfaces 5 and 15 and the oil, so that oil leakage can be prevented.

In the present invention, the average gap inclination angle in the gap changing section 15 is preferably set to 10 ° or more. That is, in order to prevent the movement of oil due to a change in the gap due to external force or relative movement, a gap inclination angle of about 10 ° or more on average is required.

Further, in each embodiment of the present invention,
The ratio of air to oil in the bearing 16 is 2%
It is desirable to set the following. When air is mixed in, the volume is inversely proportional to the pressure and proportional to the absolute temperature because the air is a gas. For this reason, unless the ratio of the air to be mixed is kept below a certain level, oil may leak or run short due to changes in air pressure and temperature. When this ratio is suppressed to 2% or less by a vacuum injection method or the like, the oil capacity including the mixed air increases by 2% or less even when the pressure is reduced to 0.5 atm, and is 0.4 when the oil volume is increased by 60 ° C.
% Or less, and these changes can be sufficiently absorbed from the capacity ratio between the bearing portion 16 and the gap changing portion 15.

Further, in the embodiment shown in FIG. 8, a magnetic fluid 17 'is used as oil, and a magnet 154 which is magnetized in the radial direction is arranged in the gap changing portion 15, and is fixed. A magnetic circuit is formed with the shaft 124. The magnetic circuit has a high magnetic flux density at the gap changing portion inner end 15a side because of a small distance from the fixed shaft 124, while the magnetic circuit has a fixed shaft 12 at the gap changing portion outer end 15b side.
The gap between the gap change portion 15 and the gap change portion 4 is set to be weak.

By setting such magnetic conditions and configuring the gap changing portion 15 as described above,
The magnetic fluid 17 'receives a pressure directed toward the inside not only by the action of the gap changing portion 15 but also by the magnetic force, so that the magnetic fluid 17' is less likely to leak. By keeping the gradient of the magnetic flux density constant, even if the surface position 17'a of the magnetic fluid 17 'slightly changes, a magnetic force of a certain level or more is surely applied.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say, there is. For example, the present invention is not limited to the shaft-fixed type device as described above, and can be similarly applied to any type of device using a bearing other than a motor.

[0060]

As described above, according to the seal device for a bearing according to the present invention, it is possible to always hold sufficient oil in the bearing portion, and to stably hold oil to prevent external leakage of oil. It can be prevented well, can withstand external force well, and can improve the reliability of the device.

[Brief description of the drawings]

FIG. 1 is a half-cross-sectional view showing the entire structure of an HDD motor to which the present invention is applied.

FIG. 2 is a principle semi-cross sectional explanatory view showing a bearing device in the HDD motor shown in FIG. 1;

FIG. 3 is a half-cross-sectional explanatory view showing an enlarged main part of a bearing device according to another embodiment of the present invention.

FIG. 4 is an enlarged plan view illustrating a main part of a bearing device according to another embodiment of the present invention.

FIG. 5 is an explanatory view of a half transverse section of the bearing device shown in FIG. 4;

FIG. 6 is a half cross-sectional explanatory view showing a bearing device according to still another embodiment of the present invention.

FIG. 7 is a half-cross-sectional explanatory view showing an enlarged main part of a bearing device according to still another embodiment of the present invention.

FIG. 8 is a half-cross-sectional explanatory view showing an enlarged main part of a bearing device according to still another embodiment of the present invention.

FIG. 9 is a cross-sectional view showing the structure of a conventional bearing device.

FIG. 10 is an enlarged explanatory view of a main part of the seal device for a bearing of the present invention shown in FIG. 2;

[Explanation of symbols]

 15 Gap changing part 16 Bearing part α Gap inclination angle

Claims (14)

(57) [Claims] 1. A bearing portion comprising a radial bearing and a thrust bearing for rotatably supporting a rotating body with respect to a fixed member is provided, and a gap changing portion is provided at two positions outside the bearing portion.
A seal device for a bearing filled with oil from one side to the other side of the gap change portion, wherein the gap change portion includes: 1) a minimum gap in the gap change portion at an inner end of the gap change portion on the bearing portion side. And at the outer end of the gap change portion on the opposite side to the bearing portion, a maximum gap in the gap change portion is provided. 2) When the angle of the gap change portion viewed from the bearing portion side is a gap inclination angle A gap inclination angle from the inner end of the gap change portion to the outer end of the gap change portion is 0 ° or more; 3) a gap between the outer end of the gap change portion and the opposing surface of the gap change portion is 0.8 mm or less; , Clearance angle 45 °
4) The content of the two gap change portions is 10% or more of the content between the two gap change portions and the content of the radial bearing portion is 100% or more. And a gap interval at an outer end of the gap changing portion is set to be at least twice as large as a gap interval at an inner end of the gap changing portion. 2. The sealing device for a bearing according to claim 1, wherein the oil amount at the time of stable stationary state is 0.1 A to 0.
A sealing device for a bearing, wherein the amount is set to a value between 9A and 9A. 3. The bearing sealing device according to claim 1, wherein an oil contact angle with the rotating member or the fixed member at the gap changing portion is set to 15 ° or more. 4. The bearing seal device according to claim 3, wherein a difference in oil contact angle between the rotating member and the fixed member in the gap changing portion is set to 15 ° or less. Sealing device. 5. The bearing sealing device according to claim 3, wherein the inner wall surface of the gap change portion is formed of a low surface tension plastic material. 6. The sealing device for a bearing according to claim 3, wherein the surface roughness Ra on the inner wall surface of the gap changing portion is 0.25 μm.
m. The bearing sealing device is set to m or less. 7. The bearing seal device according to claim 1, wherein the dynamic pressure generating groove formed in the bearing portion is configured to obtain a dynamic pressure in a direction to cancel a centrifugal force acting on the oil. Characteristic bearing sealing device. 8. The bearing sealing device according to claim 1, wherein an outer end of the dynamic pressure generating groove formed in the bearing portion is formed up to an inner end of the gap changing portion. 9. The bearing seal device according to claim 1, wherein at least two thirds of the gap change portion in the axial section is set to a parallel gap having a gap size of 0.4 mm or less. Sealing device. 10. The seal device for a bearing according to claim 1, further comprising an oil circulation hole provided outside of the bearing portion and communicating with the gap change portion. . 11. The sealing device for a bearing according to claim 1, wherein the gap changing portion is formed so as to open at an angle of 45 ° or less from an inner end of the gap changing portion to an outer end of the gap changing portion. And bearing sealing device. 12. The sealing device for a bearing according to claim 11, wherein a gap inclination angle in the gap changing portion is formed substantially constant,
A sealing device for a bearing, wherein a cross section is formed on a linear inner wall surface. 13. The bearing seal device according to claim 11, wherein an average gap inclination angle in the gap change portion is set to 10 ° or more. 14. The sealing device for a bearing according to claim 1, wherein the gap changing portion is filled with a magnetic fluid, and the magnetic fluid is set strong at an inner end of the gap changing portion and weakly at an outer end of the gap changing portion. A bearing sealing device, wherein a magnetic circuit set to have a magnetic field having a substantially constant magnetic flux density gradient in one direction is formed in at least a half or more section of the gap change portion.