JPH08232965A - Sealing device of bearing - Google Patents

Abstract

PURPOSE: To improve external force resistance holding performance of a sealing device of a bearing and to favourably hold bearing CONSTITUTION: A state of filling oil from a bearing part 31 to clearance changing parts 32 is made by providing the clearance changing parts 32 to satisfy a specified condition at two points on both ends of the bearing part 31 on a radial bearing part, respective content quantity of the both clearance changing parts 32 at the two points is set as 100% or more, clearances on both clearance changing part outer ends 32b are set twice or more of clearances on both clearance changing part inner ends 32a. Consequently, it is constituted to constantly hold oil at the bearing part even dispersion of oil filling quantity and inside capacity, change of the content quantity caused by floating and heating of a thrust bearing due to rotation, etc., and change of oil capacity due to evaporation and inside entrained air take place.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing in which a rotary member is rotatably supported by a fixed member with oil as a lubricant interposed therebetween, and the oil present in the bearing does not leak outside. The present invention relates to a bearing sealing device.

[0002]

2. Description of the Related Art In recent years, general sliding bearings, dynamic pressure bearings, etc.
Various types of bearings using oil as a lubricant have been proposed. As an example of a product using such a bearing, there is a shaft fixed type HDD (hard disk drive) motor shown in FIG. The motor shown in FIG. 8 represents an application example of the present invention, but since the basic structure is the same, it will be described with reference to this drawing. That is, a hub 4 is rotatably mounted on a fixed shaft 2 fixed to a frame 1 via a radial bearing 3, and an oil as a lubricant for rotation is provided between the fixed shaft 2 and the radial bearing 3. Is being supplied. This oil adheres to the bearing portion of the radial bearing 3 and is retained in the bearing portion by a capillary phenomenon.

[0003]

Various rotary devices using oil as a lubricant for bearings such as a rotating shaft of a motor always have a problem of countermeasures against oil leakage. In particular, in the case of bearings used for HDD motors, laser beam printer motors (LBP motors), etc., which require a clean environment, oil leakage is a serious problem. However, there have been proposed conventional bearing devices in which oil is simply attached to the gaps of the bearings, or those in which a special sealing mechanism is provided as a measure against oil leakage. According to the technology, for example, in 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, while when the amount of oil is too large, oil leakage occurs. However, there has been no bearing seal device that has a sufficient countermeasure against oil leakage. Also, in the conventional technology, gravity, vibration, shock, centrifugal force, dynamic pressure, atmospheric pressure,
There is also a problem that the bearing sealing device is not sufficiently considered with respect to external forces such as temperature and other pressures, resulting in poor reliability.

The present invention is different from the above-mentioned prior art bearing seal device: 1) The bearing has a space capable of absorbing even if the amount of injected oil changes or moves a little, Moreover, the structure is such that the oil in the space is stably held. 2) Even if an external force (gravity, vibration shock, centrifugal force, dynamic pressure, atmospheric pressure, temperature, other pressure) is applied, it is easy. The structure that oil does not splash outside and can withstand external force. 3) The structure that oil does not move easily. 4) The oil surface on the outlet side outside the bearing is stable and difficult to leak. 5) We proposed a bearing seal device that takes into account the above conditions that oil is not easily mixed with air, and 1) ensures that oil is always retained in the bearing to ensure the required bearing characteristics. To be satisfied, 2 ) An object of the present invention is to propose a bearing seal device having an effect that oil does not leak to the outside.

[0005]

In order to achieve the above object, the present invention includes the contents for satisfying the above conditions in the conventional basic structure, in which a rotating member is rotated with respect to a fixed member. A bearing seal having a radial bearing having a radial bearing that can be freely supported, is filled with oil between the fixed member and the rotating member, and has a gap change portion formed on both axial ends of the radial bearing portion. In the device, the gap change portion has: 1) a minimum gap in the gap change portion at an inner end of the gap change portion on the radial bearing portion side, and an outer end of the gap change portion on the opposite side of the radial bearing portion. 2) A gap from the inner end of the gap changing portion to the outer end of the gap changing portion when the angle of the gap changing portion viewed from the bearing portion side is a gap inclination angle. The inclination angle is 0 ° or more, 3) the clearance change outer end, the gap is 0.8mm or less with respect to the counter face to the gap changing portion, and a gap angle of inclination 45 °
The positions are as follows: 4) The inner capacities of the two gap change parts are set to 100% or more with respect to the inner capacities of the radial bearing parts, respectively, and the radii at the outer ends of the gap change parts are set. The directional gap has means for setting the directional gap at least twice as large as the radial gap at the inner ends of both gap changing portions.

Therefore, according to the present invention, the inner volume of the gap changing portion is set larger than the inner volume of the radial bearing portion and the inner volume of the bearing between the inner ends of the gap changing portion.
Even if there is a variation in the oil injection amount, a variation in the internal capacity, a change in the internal volume due to levitation or heat generation of the thrust bearing due to rotation, etc., or a change in the oil volume due to evaporation or internal mixed air, the bearing section is always The oil is retained and does not leak out.

Further, since the gap ratio between the inner end and the outer end of the gap change portion is set large, even if air is mixed in 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,
Oil becomes stable at any position.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Prior to the description of specific examples of the present invention, first, the basic idea of the invention necessary for understanding the present invention, which has been arrived at as a result of repeated research by the present inventor, will be disclosed. To do.

From the viewpoint of retaining oil in the bearing, when considering a structure having outlets in two directions, such as a general radial bearing, first, oil is the capillary suction pressure at the two outlet positions. Will be held in balance and the surface position will be determined. This state is a state in which two pressure balances are balanced, and if some pressure is applied from one side, the oil moves to a position where the pressure is balanced. For example, when the capillary suction pressures are A and B, the oil moves from the position of A = B to the position of A = B + external pressure, and the movement of the oil stops in a balanced state.

Hereinafter, the bearing seal device of the present invention will be described as an HDD.
An embodiment applied to a spindle motor for (hard disk drive) will be described in detail with reference to the drawings.

The HDD spindle motor shown in FIG.
As described above, on the fixed shaft 2 fixed to the frame 1,
A hub 4 is rotatably mounted via a radial bearing 3. Oil serving as a rotary lubricant is supplied between the fixed shaft 2 and the radial bearing 3.

That is, as shown in FIG. 1, oil 10 is continuously filled in the gap between the outer peripheral surface of the fixed shaft 2 and the inner peripheral surface of the radial shaft 3, and the oil is Air is arranged on the outside of both axial ends of 10.

At this time, the clearance between the outer peripheral surface of the fixed shaft 2 and the inner peripheral surface of the radial bearing 3 is equal to the radial bearing portion 31.
And two gap changing portions 32, 32 provided at both ends in the axial direction of the bearing portion 31 and satisfying a condition described later, and two places formed between the bearing portion 31 and the gap changing portions 32, 32. The inner space portions 33, 33 serving as oil reservoirs, and the two outer space portions 34, 34 formed on the outer side in the axial direction of the gap changing portions 32, 32.

As described above, two gap changing portions 32, 32 are provided at the upper and lower ends of the bearing portion 31 in the drawing,
The bearing oil 10 is continuously filled from the inside of the bearing portion 31 to both gap changing portions 32, 32, and the liquid surface (oil surface) 10 a of the oil 10 is arranged in the gap changing portion 32.
The inner space portion 33 may be omitted.

Here, the gap changing portions 32, 32 are formed as follows. That is, each gap change portion 32,
In 32, the innermost end in the axial direction on the side of the radial bearing portion 31 is the gap changing portion inner end 32a, the outermost end in the axial direction is the gap changing portion outer end 32b, and the outside of the gap changing portion 32 is the outer space portion 3
I will call it 4. Further, an angle α formed by the gap formed in the gap changing portion 32 at a predetermined axial position viewed from the bearing portion 31 side (back side) is defined as a gap inclination angle, and when the gap is parallel to the axial surface of the fixed shaft 2, When α = 0 °, the angle α that spreads outward is plus, and the angle α that spreads toward the radial bearing portion 31 side is minus, the gap changing portion 3
In the gap in 2, the inner end 32a of the gap changing portion is the narrowest,
The outer end 32b of the gap change portion is the widest, and the inner end 32 of the gap change portion is
The gap inclination angle α from a to the gap change portion outer end 32b is set to 0 ° or more. The gap inclination angle α of 0 ° indicates that there may be a region parallel to the fixed axis 2 in a part of the gap changing portion 32.

When there is a gap having a negative gap inclination angle α between itself and the bearing portion, the gap changing portion inner end 32a is the axially outermost end of the gap where the gap inclination angle α becomes negative for the first time. It will be applicable. Furthermore, the gap at the outer end 32b of the gap changing portion must be 0.8 mm or less,
The portion exceeding 0.8 mm corresponds to the outer space portion 34, and the gap inclination angle α at the point where the gap is 0.8 mm is 45 °.
In the above case, the maximum gap portion that satisfies the conditions of 0.8 mm or less and 45 ° or less is set as the gap change portion outer end 32b.

In the embodiment of the present invention, the internal capacity of each of the gap changing portions 32, 32 (between the fixed shaft 2 from the inner end 32a of the gap changing portion to the outer end 32b of the gap changing portion). The formed capacity) is 100% or more with respect to the inner capacity of the entire radial bearing portion 3 inside the gap change portion inner ends 32a, 32a (capacity formed between the radial bearing 3 and the fixed shaft 2). That is, when the total inner capacities of both gap changing portions 32, 32 are set to 200% or more of the inner capacity of the entire radial bearing portion 3, the outer ends of the gap changing portions 32, 32 are set. The gap size at 32b and 32b is the same as the gap change part 3
The gap size at the inner ends 32a, 32a of 2, 32 is set to twice or more, respectively.

Further, the oil is filled from the radial bearing portion 31 to the gap changing portions 32 and 32 at both ends, and the gap between the gap changing portions 32 and 32 and the fixed shaft 2 is 0.8 mm or less. Set the gap inclination angle α between the ends 32b and 32b to 4
The outer end 3 of the gap changing portion 32 is set at 5 ° or less.
Since the gap size in 2b, 32 is set to be twice or more the gap size in the inner ends 32a, 32, it becomes difficult for air to enter the oil 10 and the bearing sealing device is stable and does not leak easily. There is. That is, the inner end 3 of the gap change portion
The gap ratio between 2a and the outer end 32b becomes large, and the gap inclination angle α
Therefore, even if air is mixed in the oil surface portion 10a located in the gap changing portion 32, the air does not move to the bearing portion, and the pressure difference due to the gap ratio is provided. The air naturally moves to the outside and the mixed state is eliminated.

As already explained, the radial bearing 3
Since the inner capacity of the gap changing portions 32, 32 is larger than the inner capacity of the hub, even if there is a variation in the oil injection amount or the inner capacity of the radial bearing 3 at the time of manufacture, Even if there is a change in the internal capacity of the radial bearing 3 caused by the rotation of No. 4 above the thrust bearing surface or due to heat generation during rotation, a change in the amount of the oil 10 due to evaporation or air mixed in the inside will occur. Even
The radial bearing 3 always holds the oil 10 and does not leak to the outside.

Further, in the embodiment of the present invention, when the internal volume of the clearance changing portion 32 is A, the amount of oil injected into the radial bearing 3 is 0. The amount is set to a position between 1A and 0.9A.

That is, basically, if the oil surface 10a is located in the gap changing portion 32, the oil surface 10a is stably held and no problem occurs. However, the amount of oil, the internal capacity, etc. may change depending on time and environment. In order to eliminate oil shortage and oil leakage, the amount of oil (position of the oil surface 17a) is filled in the gap changing portion 32 within the above range, so that the performance can be sufficiently maintained in the environment normally used. can do.

Further, in the embodiment of the present invention, as shown in FIG. 9, the contact angle θ 1 between the fixed shaft 2 as a fixing member and the oil 10 in both gap changing portions 32 and the gap changing portion as a rotating member. It is desirable to set both the contact angle θ1 between 32 itself and the oil 17 to 15 ° or more. still,
FIG. 9 shows the gap changing portion 32 on the upper side of FIG. 1 among the gap changing portions 32, 32. The fact that the oil surface 10a is located in the gap changing portion 32 means that the oil 10
Since the fixed shaft 2 and the gap changing portion 32 are in contact with each other with a certain contact angle θ1, the contact angle θ1 is set to 15 ° or more.

Next, as a result of various studies by the inventor of the present invention, in order to prevent the oil 10 from leaking to the outside, it is necessary to prevent the wet expansion (raising phenomenon), and the seal. I also learned that it is necessary to divide the oil before and after the section, so I will explain the details below.

As described above, in order to prevent the wetting and expanding (raising phenomenon), it is necessary to make a state in which the oil does not cause the wetting and expanding phenomenon even if the environment and conditions change to some extent.
For that purpose, it is necessary to always satisfy the condition of (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 (Equation of Young's equation). Here, γSL: interfacial tension (surface tension) of the solid-liquid interface γS: surface tension of the solid γL: surface tension of the liquid θ1: contact angle between the solid and the liquid, and 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 when the solid surface is replaced by the solid-liquid interface, the energy is reduced by 1) (γS> γSL) or increased by 2). (ΓS <γSL) or 3) It does not change (γS = γSL), and 1) when the energy decreases, in the leaked state, that is, when the solid-liquid interface is stable, 2 In the case of 3)), there is no leakage, that is, a state where the solid surface remains stable.

ΓL fills the difference between γS and γSL.
cos θ1, which 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 if the contact angle θ 1 = 0 ° between the solid and the liquid, the balance is lost and the liquid spreads on the surface of the solid endlessly. This is the phenomenon that the oil as a liquid rises up on the shaft surface as a solid, which is basically the same as the phenomenon where the oil spreads more and more when dropped on water.

When considering the problem of oil rising up the shaft surface, it becomes (γS> γL + γS
The problem is whether or not the condition is L). Since this formula is an energy formula, the surface of a solid (eg shaft) is more than the surface of the solid only (γ S).
Solid liquid interface (γSL) and liquid surface (γL) on solid surface
Making a new means that the energy drops and becomes stable. Therefore, in such a case, it means that the so-called solid surface is eliminated, a solid-liquid interface and a liquid surface are newly formed, and the rising and diffusing leak diffusion does not stop.

In addition, external force (gravity, vibration shock,
Regarding what happens when a centrifugal force, magnetic force, or other pressure is applied, these external forces only act in the direction of changing the curvature of the liquid surface in the form of pressure, changing the relationship of the equilibrium points. I have 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 forceless under the above-mentioned rising phenomenon.

As long as the condition (γ S> γ L + γ SL) is satisfied, the rising (leakage diffusion) phenomenon does not stop. Therefore, in order to stop the rising phenomenon (γ
It is necessary to change to the condition of S <γL + γSL). Specifically, it is necessary to lower the surface tension of the solid surface. If the condition (γ S <γ L + γ SL) is satisfied, the external force also works through the surface tension of the liquid. Generally, a metal surface has a very large surface tension. Normally, several layers of film are naturally formed and the surface tension is considerably reduced, but since the surface tension is still large, such a (γS
> ΓL + γSL) condition may occur, and a rising phenomenon will occur.

Therefore, as a measure for preventing the rising phenomenon, the condition of (γS <γL + γSL) is satisfied. The actual contact angle between the solid surface and the liquid is maximized. Make good use of external force. Specifically, in response to each of the above, 1) prevent the metal surface from directly appearing on the solid surface, and protect the surface with a material having a surface tension as low as possible, such as an oil repellent, and (γS < γL + γSL). 2) The surface roughness of the solid surface is reduced to increase the substantial contact angle between the solid surface and the liquid as much as possible. Make as few gaps, grooves, scratches, and unevenness as possible on the solid surface. This is because the larger the surface area, the smaller the actual contact angle. 3) Make arrangements so that external force acts in the direction to return the rising phenomenon.

As described above, the larger the contact angle θ 1 between the solid and the liquid, the less likely it is to leak (the holding force is strong). For that purpose, it is necessary to set the contact angle θ1 between the fixed shaft 2 and the oil 10 in the gap changing portions 32, 32 and the contact angle θ1 between the gap changing portion 32 itself and the oil 10 to be 15 ° 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.

Therefore, if the inner wall surfaces of the gap changing portions 32, 32 are made of a plastic material having a low surface tension,
A plastic material having a low surface tension hardly causes oil wetting and diffusion, is also effective for retaining oil due to a capillary phenomenon, has stable properties, and has good workability, so that a practical product can be manufactured. This plastic material has a gap changing portion 32,
It can be formed on the inner wall surface of 32 using a means such as coating or painting. Further, oil repellent treatment or Teflon coating may be applied to the inner wall surfaces of the gap changing portions 32, 32.

Further, if the difference between the contact angle θ1 of the oil with respect to the fixed shaft 2 and the contact angle θ1 of the oil with respect to the gap changing part 32 itself in both gap changing portions 32, 32 is small, it becomes difficult to leak. It is better to set to.

Further, the gap changing portions 32, 32 are formed so as to open in the axial direction from the bearing portion 31 side toward the outer space 34 side at an angle of 45 ° or less, and the gap changing portions 32, 3 are further formed.
The angle of inclination of the gap on the outer side of 2 also extends below 45 °. By doing so, even if the oil level rises above the originally designed position of the gap changing portions 32, 32, a stable state can be obtained between the solid surface of the gap changing portions 32, 32 and the oil 10. It is possible to prevent the oil 10 from leaking.

Further, in the present 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 32, 32 is set to 0.25 μm or less. If there are irregularities on the inner wall surfaces of the gap change parts 32, 32,
The unevenness causes the same state as the capillary phenomenon. Capillary phenomenon is a phenomenon that occurs when the ratio of the surface of the oil that contacts the solid is large relative to the volume of the oil, and is the same even if there are irregularities or grooves on the surface instead of gaps. For this reason,
When the contact angle θ 1 <90 ° between the solid and the liquid, if there are irregularities or grooves on the surface, the contact angle changes to a substantially smaller contact angle, and it becomes easier to wet. Therefore, by suppressing the surface roughness Ra of the inner peripheral walls of the gap changing portions 32, 32 to be small, the substantial contact angle between the solid and the liquid can be increased and the leakage can be prevented easily. Thus, the surface roughness Ra is 0.2
The setting of 5 μm or less is also applied to the fixed shaft 2 side as necessary.

Actually, the contact angle of oil varies depending on the state of the solid surface, and the once-wetted surface is more easily wetted than the unwetted surface, and the oil contact angle is smaller. For example, when a water drop moves on an inclined and dirty glass surface, the contact angle of the water drop on the tip side of the glass is large, and the contact angle after the water drop is small. In addition, a surface that has been once wet easily gets wet, and water droplets drop through the same place. This is due to the difference in shape and the surface tension of the solid surface in the micro portion. 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. Therefore, when viewed macroscopically, the contact angles will be different and balanced. And if the surface tension is uneven, even if the entire oil is withdrawn,
The oil surrounded by the concave surface and dirt is not able to move and is left behind, and when it is expanded again, the state of a large contact angle cannot be taken in macro view, and it is connected to the oil left before that. As a result, the contact angle becomes small, and it becomes easy to pass through, and passes through a once wet place many times.

With such a solid surface state,
If the oil is once wet or touches the oil when oil is injected for some reason, the contact angle is small and the holding force is small at that portion, so that the oil can easily pass through. Therefore, at the two outlets of the bearing, that is, from the gap changing portions 32, 32 to the outside, the unevenness (surface roughness) is as small as possible,
It is necessary to minimize dirt (uneven surface tension).

Further, it is said that the contact angle between a macroscopic (solid) solid and a liquid when the solid surface has irregularities or uneven surface tension is as follows.

If there is unevenness, it is smooth (flat)
When the ratio of the surface area of the actual surface to the surface is r, the macro (apparent) contact angle θW (called the Wenzel contact angle) is cos θW = rcos θ1 (θ1: micro (truth) contact angle) Micro Even if the contact angle of θ1 = 60 ° (cos θ = 0.5) is considerably large, if the concavities and convexities r = 2 or more, the contact angle of the macro becomes θW = 0 °, which is a rising phenomenon (wet expansion). It will not stop. From this also, in order to prevent leakage, it is preferable to keep the surface roughness from the gap changing portion to the outside as small as possible, and preferably to make it a mirror surface state.

On the other hand, when the surface tension is uneven, it is considered that the surface is a composite surface having different surface tensions. Therefore, the macro (apparent) contact angle θC (called the Cassie contact angle) is cos θC = A1 cos θ1 + A2 cos θ2. However, A1 and A2 are ratios of areas occupied by different surface tensions, and θ1 and θ2 are micro (truth) contact angles with different surface tensions. Even in this case, in order to prevent leakage, it is preferable to suppress the surface roughness from both gap changing portions to the outside as small as possible, and desirably to make it a mirror surface state.

Next, the outer ends 32 of the gap changing portions 32, 32
When the position within 1/2 of the axial length of the gap changing portions 32, 32 from b, 32b is set as the reference position, the inner wall surface extending from the reference position to the outside is the bearing portion 3 from the reference position.
Contact angle θ that is at least 15 ° larger than the inner wall surface on the 1st side
It is also effective to use a material having 1 or a treated surface. That is, one method is to increase the contact angle between the solid and the liquid in order to make it difficult to leak, but if the total contact angle cannot be increased due to some constraint,
It is also effective to increase the contact angle of only the most necessary part for holding.

Furthermore, the contact angle .theta.1 at the large diameter side of the gap changing portions 32, 32, that is, at the outer ends 32b, 32b.
However, it is also effective to set to be larger than the contact angle at the small diameter side, that is, at the inner ends 32a, 32a.

That is, when the rotary member rotates, centrifugal force also acts on the oil in the bearing, so that the gap changing portions 32, 32
The oil pressure is higher on the surface on the large diameter side in the radial direction than on the surface on the small diameter side. Therefore, when the contact angle is the same on both the large diameter side and the small diameter side, the contact point position between the large diameter solid and the oil surface is outside the contact point position between the small diameter solid and the oil surface. As a result, the condition becomes easy to leak and air is easily mixed. On the other hand, when the contact angle on the large diameter side is increased, the contact point position between the solid on the large diameter side and the oil surface and the contact point position on the small diameter side due to the equilibrium balance and pressure difference at the contact point Is smaller, which is advantageous for oil leakage and air mixing.

On the other hand, in the present invention, the inclination angle as viewed from the bearing portion 31 side with respect to the radial center of the gap changing portion 32 on the large diameter surface side may be set within the range of 10 ° to −20 °. In other words, the centrifugal force on the oil generated by rotation is always large on the side with the larger diameter.By using such a shape, the pressure due to the centrifugal force does not work in the direction of oil leakage, and a more stable state is maintained. You can

Further, in the present invention, the outer end of the dynamic pressure generating groove of the radial bearing 3 is replaced by the inner end 3 of the gap changing portions 32, 32.
It may be formed by extending to 2a and 32a. In this way, the dynamic pressure generating groove is formed on the inner ends 32a, 3 of the gap changing portions 32, 32.
If it is configured to extend to 2a, the clearance inclination angle α from the bearing portion 31 will always be in a state of α ≧ 0 °, and it will be difficult for air to mix in when oil is injected, and even if mixed, the direction of pushing out to the outside The force is applied, and it is possible to maintain a state in which it is easy to retain oil at all times.

Further, in the embodiment of the present invention, the gap inclination angle α in the gap changing portion 32 is formed so that the gap inclination angle α is substantially constant and is formed on the inner wall surface having a linear cross section. Since the shape is the easiest to process, and the clearance inclination angle α is α> 0 ° at any position, the force that oil is inward and the force that air is outward are always stable, which is preferable.

On the other hand, in another embodiment of the present invention, FIG.
As shown in the main part of the bearing portion, a gap 321 is provided in the gap changing portion 32 in the radial direction. By providing the gap 321 in the radial direction in this manner, the internal volume for holding oil can be increased, and in particular the gap 32
The oil 10 in the gap 321 is reliably held by keeping the axial width of 1 smaller than the width between the outer end 32b of the gap change portion and the fixed shaft 2. Further, since the gap 321 formed in the radial direction does not take a large dimension in the axial direction, the overall axial dimension is suppressed and the impact resistance is advantageous.

If the gap 321 satisfies the conditions of the gap changing portion 32 already described, as shown in FIGS. 3 and 4, a groove-like gap 322 is provided in the radial direction in the axial direction, or Alternatively, it can be formed as a hole.

At this time, the above-mentioned gap may be a radial gap 322 satisfying the gap changing portion condition as shown in FIGS. 3 and 4, or may be a hole (not shown). It is also possible to form it. These cases are similar to the above cases, but in the case of holes in particular, the ratio of the solid surface to the capacity increases and the pressure generated by the capillary phenomenon doubles, so the radius of the hole is different from the gap when facing each other. Correspond.

Further, in the present invention, 2/3 or more in the axial section of the gap changing portion 32 may be set to a parallel gap (gap inclination angle α = 0 °) within a gap size of 0.4 mm. With such a shape, the gap changing portion 3
A large space 2 can be secured, more variations and changes in the oil 10 can be absorbed, and the gap between the parallel gaps can be kept small, so that a leak-resistant state is secured.

Further, as shown by the broken line in FIG. 5, an oil circulation hole 323 for communicating the insides of the gap change portion inner ends 32a, 32a is provided, or two radial bearings 3 are provided as usual. In this case, as shown by the chain double-dashed line in the figure, an air discharge means including a hole 324 for letting out the internal air between the radial bearings 3 is provided in the fixed shaft 2,
Alternatively, a gap may be provided in the radial bearing 3 and the radial bearing 3
You may connect between. When air is present inside the bearing, the air may expand or become high in pressure due to changes in atmospheric pressure and temperature. In this case, the oil pressure may push out the oil interposed in the bearing portion. On the other hand, if the bearings are connected to each other by the air discharging means composed of holes or gaps, the expanded air escapes through the air discharging means to eliminate the pressure difference, and the pressure for pushing out the oil is not applied.

Further, in the present invention, although not shown, a groove or a ridge extending in the axial direction may be provided from the gap changing portion 32 to the outside thereof. According to this structure, when air is mixed in the oil 10 for some reason, the oil 10 and the air can be smoothly replaced with each other, and the air can be pushed out more reliably. This is because if there are grooves or ridges, the oil 10 moves toward the narrower gap and the air moves toward the wider gap due to the surface tension, and the oil and air are separated. Furthermore, if this groove or ridge is formed to the outside in the axial direction, the oil
You can move individually without being hit by air,
Oil and air can be replaced more smoothly.

Further, in the embodiment shown in FIG. 6, in the two radial bearings 3 arranged in the upper and lower directions, the radial change is made inward from the inclination angle of the gap changing portion 42 located on the outer side formed in each radial bearing 3. The inclination angle of the gap changing portion 52 located is set to be large and the oil contact angle is set to 4
It is configured to be 5 ° or less. The smaller the contact angle at which the maximum holding pressure is generated, the larger the pressure can be generated. At a contact angle of 45 °, the contact angle is about 70%. Therefore, it is necessary to suppress the contact angle to this extent. Further, in the embodiment of FIG. 6, the average gap inclination angle in the gap changing portions 42 and 52 is 1
It is configured to be 0 ° or more. To prevent oil movement due to changes in the gap due to external force or relative movement,
A gap inclination angle of about 10 ° or more is required on average.

When air is present between the two bearings 3 as in the embodiment of FIG. 6, the average gap inclination angle in the gap changing portion 52 located inside the bearing portion 31 is
The gap changing portion 42 positioned outside the radial bearing portion 31
It is preferable to set the average gap inclination angle at 2 times or more. With this configuration, the capacity of the outer clearance change section 42 can be made larger than the capacity of the inner clearance change section 53, and the amount of oil that can be oiled can be substantially increased. Although the oil easily overflows from the gap changing portion 52 on the inner side and leaks out, there is no problem because it serves to return the oil to the inner side of the bearing.

Further, in the embodiment shown in FIG. 7,
A magnetic fluid is used as oil, a magnet 62 is arranged between two bearings 3 made of a magnetic material, and a magnetic circuit is formed with the fixed shaft 2 made of a magnetic material. In the above magnetic circuit, since the bearing 3 and the fixed shaft 2 are made of a magnetic material, the magnetic flux density is strong at the inner end 32a of the gap changing portion 32 and the outer end 3 of the gap changing portion 32.
2b is set weakly, and the gap changing portion 3
The magnetic field has a constant magnetic flux density gradient in almost one direction in at least a half or more of 2.

By making such magnetic conditions,
The magnetic fluid as oil is in a state in which it is more unlikely to leak due to the inward pressure due to the magnetic force. Also, by keeping the magnetic flux density gradient as constant as possible, even if the position of the magnetic fluid changes to a certain extent, a magnetic force above a certain level will be 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-mentioned embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that there is. For example, the present invention is not limited to the above-mentioned fixed shaft type device, but can be similarly applied to a rotary type device, and can be applied to all types of devices using bearings other than motors. However, the same can be applied.

[0059]

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

[Brief description of drawings]

FIG. 1 is a semi-transverse sectional view showing a bearing device according to an embodiment of the present invention.

FIG. 2 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. 3 is an enlarged plan view showing a main part of a bearing device according to another embodiment of the present invention.

4 is a semi-transverse cross-sectional explanatory view showing an enlarged main part of the bearing device shown in FIG.

FIG. 5 is a half cross-sectional explanatory view showing a bearing device according to another embodiment of the present invention.

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

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

FIG. 8 is a semi-transverse sectional view showing the entire structure of the HDD motor to which the present invention is applied.

FIG. 9 is a half transverse cross-sectional explanatory view showing an enlarged main part of the bearing device according to the embodiment of the present invention.

[Explanation of symbols]

 31 Radial bearing part 32 Gap change part α Gap inclination angle

Claims (14)

[Claims] 1. A radial bearing having a radial bearing portion for rotatably supporting a rotary member with respect to a fixed member is provided, and oil is filled between the fixed member and the rotary member and an axial direction of the radial bearing portion is provided. A seal device for a bearing having gap change portions formed on both end sides, wherein the gap change portion has: 1) a minimum gap in the gap change portion at an inner end of the gap change portion on the radial bearing portion side, and the radial change portion. There is a maximum gap in the gap change portion at the outer end of the gap change portion on the side opposite to the bearing portion, and 2) when the angle of the gap change portion as viewed from the bearing portion side is the gap inclination angle, the gap change The gap inclination angle from the inner end of the portion to the outer end of the gap changing portion is 0 ° or more, and 3) the outer end of the gap changing portion has a gap of 0.8 mm or less with respect to the facing surface of the gap changing portion, and the gap inclination angle. Is 45 °
The positions are as follows: 4) The inner capacities of the two gap change parts are set to 100% or more with respect to the inner capacities of the radial bearing parts, respectively, and the radii at the outer ends of the gap change parts are set. The bearing seal device is characterized in that the directional gaps are each set to twice or more than the radial gaps at the inner ends of the gap change portions. 2. The bearing seal device according to claim 1, wherein when the static amount of the stationary state is A, and the internal volume of the gap change portion is A, the amount of oil is 0.1 A to 0.
A bearing seal device, wherein the amount is set to a position between 9A. 3. The bearing sealing device according to claim 1, wherein the contact angle of the oil with the rotating member or the fixed member in the gap changing portion is set to 15 ° or more. 4. The bearing seal device according to claim 3, wherein a difference between a contact angle between the rotating member and the oil and a contact angle between the fixed member and the oil in the gap changing portion is set to 15 ° or less. A bearing seal device characterized by the above. 5. The bearing sealing device according to claim 3, wherein the inner wall surface of the gap change portion is formed of a plastic material having a low surface tension. 6. The bearing seal device according to claim 3, wherein the surface roughness Ra on the inner wall surface of the gap change portion is 0.25 μm.
A bearing seal device characterized by being set to m or less. 7. The bearing sealing device according to claim 1, wherein the outer end of the dynamic pressure generating groove formed in the bearing portion is formed up to the inner end of the gap changing portion. 8. The bearing seal device according to claim 1, wherein 2/3 or more of the gap changing portion in the axial direction section is set to a parallel gap within a gap size of 0.4 mm. Sealing device. 9. The bearing seal device according to claim 1, wherein the gap change portion is formed to open at an angle of 45 ° or less from the inner end of the gap change portion toward the outer end of the gap change portion. Bearing seal device. 10. The bearing seal device according to claim 9, wherein the gap inclination angle in the gap change portion is formed to be substantially constant.
A bearing seal device having a straight inner surface with a cross section. 11. The bearing seal device according to claim 9, wherein the average gap inclination angle in the gap change portion is set to 10 ° or more. 12. The bearing seal device according to claim 1, wherein an oil circulation hole is provided to allow the inner end of the gap slope portion and the radial bearing portion to communicate with each other. 13. The bearing seal device according to claim 1, wherein a groove extending in the axial direction is provided from the gap change portion to the outside thereof. 14. The bearing seal device according to claim 1, wherein the gap change portion is filled with magnetic fluid, and the magnetic fluid is set to be strong at the gap change portion inner end and weak at the gap change portion outer end. A bearing sealing device is characterized in that a magnetic circuit is formed so that a magnetic field having a constant magnetic flux density gradient in one direction is formed in at least half of the gap changing portion.