JPH08210364A - Sealing device of bearing - Google Patents

Abstract

PURPOSE: To keep a constantly sufficient amount of oil at a bearing part, and to excellently prevent the leakage of the oil to the outside by providing a clearance changing part on the outer side in the axial direction of a radial bearing part. CONSTITUTION: A clearance changing part 50 to prevent the leakage of oil 15 and the achieve the sealing is provided on the outer side in the axial direction of a radial bearing part 24 arranged on the outer side in the axial direction. The level 15a of the oil 15 as the lubricant of a bearing filled in a bag-shaped bearing space which is approximately bag-shaped bag part 40 is set to be within the clearance changing part 50. The sealing device of the bearing of this structure employs the single bag structure where an approximately cylindrical part to be formed by a radial bearing is provided with a bag part 40 covered by a thrust side plate 25, and the bottom part (on the thrust side plate 25 side) can be regarded as a wall to withstand the generated pressure of 1 atm., and the oil 15 is not moved even when the external force is applied from the upper part to the thrust bearing side.

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 relative to a fixed member by interposing an oil as a lubricant between the fixed member and the oil interposed in the bearing portion to the outside. The present invention relates to a bearing seal device for preventing leakage.

[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. In this motor, a hub 4 is rotatably attached to a fixed shaft 2 fixed to a frame 1 via a radial bearing 3, and a lubricant for rotation is provided between the fixed shaft 2 and the radial bearing 3. Oil is being supplied. This oil adheres to the bearing portion of the radial bearing 3 and is held 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. In 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, The problem of oil leakage has occurred, and a bearing seal device that does not sufficiently prevent oil leakage has not been achieved. In addition, the conventional technology does not provide a bearing seal device that sufficiently considers external forces such as gravity, vibration, shock, centrifugal force, dynamic pressure, atmospheric pressure, temperature, and other pressures, and therefore has high reliability. There was also the problem of being scarce.

The present invention is different from the above-described bearing seal device of the prior art in that 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) External force (gravity, vibration, shock, centrifugal force, dynamic pressure, atmospheric pressure,
Even if it is subjected to temperature and other pressures), oil does not easily escape to the outside, it has a structure that can withstand external force, 3) it has a structure that makes it difficult for oil to move, 4) outside the bearing The oil surface on the outlet side is stable and difficult to leak. 5) A structure that prevents oil from mixing with air is proposed. A bearing seal device that takes into account the above conditions is proposed. 1) Bearing It is an object of the present invention to propose a bearing seal device which has the effects that oil is always retained in the portion and the required bearing characteristics are satisfied, and 2) oil does not leak to the outside.

[0005]

In order to achieve the above object, the present invention has a basic structure of a single bag having a bearing space having an outlet in only one direction, and further includes contents for satisfying the above conditions. A shaft formed on one side of the rotating member and the fixed member is inserted into a substantially cylindrical bag portion formed on the other side, and a pair of radial bearing portions provided in the bag portion. The rotating member and the fixed member are rotatably supported relative to each other, a gap changing portion is provided on the axially outer side of the radial bearing portion, and oil is filled from inside the bag portion to the gap changing portion. The gap changing portion has: 1) a minimum gap in the gap changing portion at an inner end of the gap changing portion on the radial bearing portion side, and a change in the gap at an outer end of the gap changing portion on the opposite side of the radial bearing portion. To the department 2) When the angle of the gap changing portion with respect to the axis viewed from the bag portion side is the gap inclination angle, the gap inclination angle from the inner end of the gap changing 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 m with the shaft.
m or less and the gap inclination angle is 45 ° or less, 4) The content of the gap changing portion is 5% or more of the content of the bag portion, and the content of the radial bearing portion is 5% or more. On the other hand, there is provided means for setting the radial gap at the outer end of the gap changing portion to be 100% or more and at least twice the radial gap at the inner end of the gap changing portion.

Therefore, in the present invention, 1) the gap of the gap changing portion is 0.8 mm or less, and the gap inclination angle of the outer end of the gap changing portion is 45 ° or less. 2) It becomes difficult to leak. 2) By making the inner volume of the gap change section larger than the inner volume of the bag section and the radial bearing section, there are variations in the oil injection amount and content volume, and thrust bearing Even if there is a change in the internal volume due to levitation or heat generation, or a change in the oil volume due to evaporation or air mixed in internally, the oil is always retained in the bearing and does not leak to the outside. Since the gap ratio between the inner and outer ends of the gap change part is large, even if air is mixed in on the oil surface, it will not move to the bearing part and the pressure due to the gap ratio From the difference Air is moved to the outside,
The mixed state is eliminated. Further, the gap ratio makes it easy to stabilize the oil at any position.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Prior to the description of specific embodiments 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 Disclose.

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. In this state, the two pressure balances are balanced, and when some pressure is applied from one side, the oil moves to a position where the pressure is balanced. For example, assuming capillary suction pressures 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.

In such a structure having two outlets, the position of the oil in the bearing is determined by the pressure balance, and therefore 1) the oil always moves when an external force is applied.
On the other hand, even if the oil moves, it will not leak,
A space for holding oil is required. Further, there is a high probability that air will be mixed into the oil due to repeated oil movement. 2) The oil pressure generated by the capillarity (holding pressure) is inversely proportional to the clearance gap, but the minimum clearance is usually defined by the bearing clearance, so it is necessary to increase the oil pressure (holding pressure). Has a limit.

As a result of the above-mentioned examination, a single bag structure shown as an embodiment of the present invention (a structure in which one of two outlets is closed like a structure in which one side of a substantially cylindrical shape is closed) Unlike the structure having the two outlets, the bearing sealing device has a structure in which one side can be regarded as a wall that holds and generates a pressure of 1 atm, and therefore has the following effects. 1) Since the oil does not move even when an external force is applied, the oil holding space can be minimized, and the probability that air will be mixed into the oil will be low. 2) Since the oil is held at a very large pressure of 1 atm, it is possible to improve the external force holding performance.

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

The HDD spindle motor shown in FIG.
It is the figure which showed the right half from the rotation center axis line XX. This spindle motor includes a stator assembly 2 as a fixing member assembled to a frame 10 fixed to a disk device.
0, and a rotor set 30 as a rotating member that is assembled to the stator set 20 from above in the figure in a laminated manner. Of these, the stator core 21 that constitutes the stator set 20 is fitted to the outer peripheral portion of a substantially cylindrical bearing holder 22 that is erected at a substantially central position of the frame 10, and the salient pole portion of the stator core 21. A winding wire 23 is wound around.

A radial bearing, which is provided with a pair of radial sliding bearing portions 24, 24 which are axially separated from each other by a predetermined distance, is fixed to the inner peripheral portion of the bearing holder 22, and the pair of radial sliding bearing portions 24, 24 are provided. A rotary shaft 31 is rotatably supported by 24. Conventionally known radial dynamic pressure generating grooves are formed on the inner peripheral surfaces of both the radial slide bearing portions 24, 24, and the bearing oil 15 interposed as a lubricant with respect to the outer peripheral surface of the rotating shaft 31 is formed. The inner peripheral surface of each radial sliding bearing portion 24 and the outer peripheral surface of the rotary shaft 31 constitute a dynamic sliding surface in the radial direction.

The lower end of the rotary shaft 31 is supported by a dynamic pressure thrust bearing. This dynamic thrust bearing
It has a thrust receiving plate 25 that covers the opening formed in the lower end surface of the bearing holder 22.
The sliding surface of No. 5 faces the lower end portion of the rotary shaft 31, and the thrust bearing portion 26 having a groove for generating thrust dynamic pressure is formed on the sliding surface as usual to form a thrust bearing. Then, between the radial bearing having the thrust receiving plate 25 and the pair of radial sliding bearing portions 24, 24 and the rotary shaft 31, a bearing space formed of a substantially cylindrical clearance passage is formed in a bag shape. The portion 40 is formed, and the oil 1 is placed in the bearing space of the bag portion 40.
By being filled with 5, the rotary shaft 31 is rotatably supported.

On the other hand, a hub 37 constituting the rotor set 30 is fixed to the base portion (upper end portion in the drawing) of the rotary shaft 31 so as to rotate integrally with the rotary shaft 31. The hub 37 includes a substantially cylindrical clamper 33 for mounting a plurality of magnetic disks 34 and spacers 33 a, 33.
In addition to having b, a motor rotor drive magnet 36 is mounted on the hub 37 via a back yoke 35. The drive magnet 36 has an annular shape, and is arranged close to the outer peripheral end surface of the stator core 21 so as to face it.

In the present invention, as shown in FIG. 2 in which only the bearing portion is schematically extracted, the oil 15 is provided on the outer side in the axial direction of the radial bearing portion 24 arranged on the outer side in the axial direction.
A gap changing portion 50 is provided for preventing leakage and sealing. The liquid surface 15a of the oil 15 as the lubricant of the bearing filled in the bag-shaped bearing space (including the thrust bearing portion, the radial bearing portion and the space therebetween) formed into the substantially cylindrical bag portion 40 has the above-mentioned gap. It is set so as to be located inside the changing unit 50.

Here, the gap changing portion 50 is formed as follows. That is, in the gap changing portion 50, the axially innermost end on the radial bearing 24 side is located at the gap changing portion inner end 50.
a and the radial bearing 2 from the inner end 50a of the gap change portion.
The 4 side becomes the bag portion 40. The outermost end of the gap changing portion 50 is the gap changing portion outer end 50b, and the gap changing portion outer end 5b.
The outside of 0b is the outside of the gap changing portion 50. The gap changing portion 50 at a predetermined axial position when viewed from the bag portion 40 side
The angle α formed by the gap formed in 1 is defined as the gap inclination angle, α = 0 ° when the gap is parallel to the rotation axis surface, the angle α that spreads to the outside is added, and the angle that spreads to the bag portion 40 side When α is negative, the gap changing portion 50
The innermost end 50a of the gap changing part is the smallest and the outermost end 50b of the gap changing part is widest, and the gap inclination angle α from the inner end 50a of the gap changing part to the outer end 50b of the gap changing part is set to 0 ° or more. is there. The gap inclination angle α of 0 ° indicates that a region parallel to the rotation axis 31 may exist in a partial region of the gap changing portion 50.

If there is a gap having a negative gap inclination angle α with the bearing portion, the gap changing portion inner end 50a is the axially outermost end of the gap where the gap inclination angle α becomes negative for the first time. It will be applicable. Further, the gap at the outer end of the gap change portion needs to be 0.8 mm or less, and
The portion exceeding 8 mm corresponds to the outside of the gap changing portion, and the gap inclination angle α at the point where the gap is 0.8 mm is 45.
In the case of more than 0 °, the maximum gap portion satisfying the conditions of 0.8 mm or less and 45 ° or less is defined as the gap change portion outer end 50b.

In the present invention, the gap changing portion 50
The internal volume of (the volume formed between the gap changing portion inner end 50a and the gap changing portion outer end 50b with the rotating shaft 31) is
It is set to 5% or more of the internal capacity of the entire bag section 40 inside the gap change section inner end 50a, and the two internal capacities of the pair of radial bearing sections 24, 24 (the radial bearing section 24 and the rotary shaft 31 are (Capacity formed between the gaps) is set to 100% or more, and the size of the gap at the outer end 50b of the gap changing part 50 is equal to the inner end 5 of the gap changing part 50.
It is set to twice or more the size of the gap at 0a.

The operation of the bearing seal device according to the present invention having the above-described structure will be described with reference to FIG. 2. The bearing seal device of this structure has, as a basic structure, a substantially cylindrical shape formed by a radial bearing. Since the single bag structure having the bag portion 40 whose cylindrical portion is closed by the thrust receiving plate 25 is adopted, the bottom portion (thrust receiving plate 2
(5 side) can be regarded as a wall that holds and generates a pressure of 1 atm, and the oil 15 does not move even when an external force is applied to the thrust bearing side from the upper part. Therefore, it is not necessary to consider the oil movement due to the application of the external force, and therefore the oil holding space by the gap changing portion 50 can be reduced. In addition, since the movement of oil due to the application of external force does not occur basically, there is no concern about the mixing of air due to the movement of oil, and the oil is held at a very large pressure of 1 atm. A bearing sealing device having high performance can be obtained.

Further, the oil 15 is filled from the bag portion 40 to the gap changing portion 50, and the rotating shaft 3 of the gap changing portion 50 is filled.
The gap between the gap change portion and the outer end 50b is 0.8 mm or less.
The gap inclination angle α is set to 45 ° or less, and the gap size at the outer end 50b of the gap changing portion 50 is set to the inner end 50a.
Since it is set to be twice or more as large as the clearance dimension in (1), it is difficult for air to mix in the oil 15 and the bearing sealing device is stable and does not easily leak. That is, since the gap ratio between the inner end 50a and the outer end 50b of the gap changing portion is increased and the gap inclination angle α is provided, air may be temporarily mixed in the oil surface portion 15a located in the gap changing portion 50. However, the air does not move to the bearing portion, and due to the pressure difference due to the gap ratio, the air naturally moves to the outside and the mixed state is eliminated.

Further, as described above, since the inner volume of the gap changing portion 50 is larger than the inner volume of the bag portion 40 and the inner volume of the radial bearing portions 24, 24, the oil injection amount and the manufacturing time are reduced. Even if there is variation in the internal capacity of the bag portion 40 in the above, there is also a change in the internal capacity of the bag portion 40 due to the fact that the bag floats above the thrust bearing surface due to the rotation of the rotating shaft 31 and that heat is generated during rotation. Even if the amount of oil 15 changes due to evaporation or air mixed therein, the oil 15 is always held in the bearing portion and does not leak to the outside. In addition, in order to absorb variations in the oil injection amount and the internal capacity of the bag portion 40 at the time of manufacturing, an oil reservoir groove 27 may be formed inside the gap changing portion 50.

Furthermore, in the present embodiment, the amount of oil injected into the bag portion 40 that constitutes the bearing space is such that, when the internal volume of the gap changing portion 50 is A, the amount of oil in the gap changing portion is stable when stationary. The amount is set to a position between the end 50a and 0.1A to 0.9A.

That is, basically, if the oil surface 15a is located in the gap changing portion 50, it is stably held and no problem occurs, but even if the oil amount, the internal capacity, etc. change due to time and environment. In order to eliminate oil shortage and oil leakage, the amount of oil (the position of the oil surface 15a) is filled in the gap changing portion 50 within the above range, so that the performance can be sufficiently maintained in the normally used environment. be able to.

Further, in the present embodiment, as shown in FIG. 3, the contact angle θ between the rotary shaft 31 of the gap changing portion 50 and the oil 15 on both surfaces of the gap changing portion 50 itself.
It is desirable to set 1 to 15 ° or more. Gap changing part 5
The fact that the oil surface 15a is located within 0 means that the oil 15 is in contact with the rotating shaft 31 and the gap changing portion 50 at a certain contact angle θ1, and therefore the contact angle θ
1 is set to 15 ° or more.

Next, as a result of various studies by the inventor of the present invention, in order to prevent leakage of the oil 15 to the outside, it is necessary to prevent wet expansion (climbing up 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 / expansion (raising phenomenon), it is necessary to make a state in which the oil does not cause the wetting / expansion phenomenon even if the environment / condition changes 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 ... (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 decreases by 1) (γS> γSL), or increases by 2). (ΓS <γSL), or 3) Does not change (γS = γSL), and 1) when the energy decreases, in a wet state, that is, when a solid-liquid interface is stable,
In the cases of 2) and 3), it is in a non-wetting state, that is, a state in which the solid surface remains stable.

ΓL cos is to fill the difference between γS and γSL.
θ1 and is balanced by the contact angle θ1 between solid and liquid. That is, as (γS −γSL) increases, θ
When 1 becomes small and (γS> γL + γSL), even if the contact angle θ1 = 0 ° between the solid and the liquid becomes unbalanced, the liquid spreads endlessly on the solid surface. 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 upward leak diffusion does not stop.

Incidentally, 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, although these forces try to move the position of the equilibrium point by the force of the surface tension of the liquid, they are helpless under the above-mentioned rising phenomenon.

As long as the condition (γS> γL + γSL) is satisfied as described above, 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) in some cases,
Yes, a rising phenomenon will occur.

Therefore, as a measure for preventing the rising phenomenon, the condition of (γS <γL + γSL) is set. 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, the contact angle θ between the rotating shaft 31 of the gap changing portion 50 and the oil 15 on both surfaces of the gap changing portion 50 itself.
It is necessary to set 1 to 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, when the inner wall surface of the gap changing portion 50 is made of a plastic material having a low surface tension, the plastic material having a low surface tension is less likely to cause oil wetting and diffusion, and is effective for retaining oil by a capillary phenomenon. It is stable and has good workability, so it can be used for practical products. This plastic material can be formed on the inner wall surface of the gap change portion 50 by means such as coating or painting. Further, the inner wall surface of the gap changing portion 50 may be subjected to oil repellent treatment or Teflon coating.

Further, the rotary shaft 3 in the gap changing portion 50
1 and the gap change portion 50 itself have a small difference in contact angle θ1 between the two surfaces, it is difficult to leak. Therefore, it is preferable to set the difference between the contact angles θ1 with the oil 15 on both surfaces above 15 °.

Further, in order to reduce the surface roughness of the solid surface, in the present embodiment, the surface roughness Ra of the surface of the inner wall surface of the gap changing portion 50 is set to 0.25 μm or less. If the inner wall surface of the gap changing portion 50 has unevenness, 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. Therefore, 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 wall surface of the gap changing portion 50 to be small, it is possible to increase the substantial contact angle between the solid and the liquid and prevent leakage. The setting of the surface roughness Ra to 0.25 μm or less is applied to the rotary shaft 31 side as required.

Actually, the contact angle of oil varies depending on the state of the solid surface, and the once wet surface is easier to wet than the non-wetted 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, for some reason, the oil leaks or touches the oil when oil is injected, the contact angle is small and the holding force is small at that portion, which facilitates the passage of the oil. Therefore, it is necessary to reduce the unevenness (surface roughness) and the dirt (uneven surface tension) as small as possible at the bearing outlet, that is, from the gap change portion to the outside.

The contact angle between a macroscopic (apparent) solid and a liquid when the solid surface has irregularities or uneven surface tension is said to be 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 θ is considerably large as θ 1 = 60 ° (cos θ = 0.5), the contact angle of the macro becomes θ W = 0 ° if r = 2 or more due to unevenness, and the rising phenomenon (wet expansion) occurs. 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 keep the surface roughness from the gap change portion to the outside as small as possible, and preferably to make it a mirror surface state.

Next, when the position within 1/2 of the axial length of the gap changing portion 50 from the outer end 50b of the gap changing portion 50 is set as the reference position, the inner wall surface extending from the reference position to the outside is At least 15 from the inner wall surface on the back side from the reference position
It is also effective to use a material or a treated surface that has a contact angle θ1 larger than °. That is, one method is to increase the contact angle between the solid and the liquid to make it difficult to leak, but if the overall contact angle cannot be increased due to some restrictions, only the part most necessary for holding is required. It is also effective to increase the contact angle of.

Furthermore, the contact angle θ1 at the large diameter side of the gap changing portion 50, that is, at the outer end 50b is at the small diameter side, that is,
It is also effective to set the contact angle to be larger than the contact angle at the inner end 50a. That is, when the rotating member rotates, the centrifugal force also acts on the oil in the bearing, so that the surface of the gap changing portion 50 on the radially large diameter side has a higher oil pressure than the surface of the gap changing portion 50 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, if 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 on the small diameter side due to the equilibrium balance and pressure difference at the contact point The difference from the position becomes small, which is advantageous for oil leakage and air mixing.

Further, in the embodiment of the present invention, when the outer end (upper end in the figure) of the dynamic pressure generating groove of the radial bearing portion 24 is provided with the oil sump groove 27 as shown in FIG. Is up to the oil sump groove 27, or the gap changing portion 50 when the oil sump groove 27 is not provided.
May be formed by extending to the inner end 50a. If the dynamic pressure generating groove is configured to extend to the inner end 50a of the gap changing portion 50 in this way, the gap inclination angle α from the radial bearing portion 24 will always be in a state of α ≧ 0 °, and when oil is injected, for example. It becomes difficult for air to mix in, and even if it mixes in, a force in the direction of pushing it out is applied, and it is possible to always maintain a state in which oil can be easily held.

The gap changing portion 50 is formed so as to open at an angle of 45 ° or less from the gap changing portion inner end 50a toward the gap changing portion outer end 50b, and further, the gap inclination outside the gap changing portion 50 is formed. The angle also extends below 45 °. By doing so, even if the oil level rises above the originally designed position of the gap changing portion 50, the gap changing portion 5 can be prevented.
A solid state of 0 and the oil 15 can be in a stable state, and leakage of the oil 15 can be prevented.

Gap inclination angle α in the gap changing portion 50
Is that the clearance inclination angle α is formed substantially constant and is formed on the inner wall surface having a straight cross section because the shape is the easiest to process and the clearance inclination angle α is α> 0 ° at any position. , Oil is inward and air is outward.

The average gap inclination angle in the gap changing portion 50 is preferably set to 10 ° or more. In order to prevent the oil movement 15 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.

It should be noted that 2/3 or more in the axial section of the gap changing portion 50 may be set to a parallel gap (gap inclination angle α = 0 °) within a gap size of 0.4 mm. With such a shape, a large space can be provided in the gap changing portion 50, more variation and change of the oil 15 can be absorbed, and the gap distance of the parallel gap portion can be suppressed to be small, which makes it difficult to leak. Will be secured.

Next, in the embodiment shown in FIG. 4, a gap 51 is provided in the gap changing portion 50 in the radial direction. By providing the gap 51 in the radial direction in this way, the internal capacity for retaining oil can be increased, and in particular, the width of the gap 51 in the axial direction can be set to the outer end 50b of the gap changing portion 50 and the rotary shaft 31. By keeping the width smaller than the gap, the oil in the gap 51 is reliably retained. Further, since the gap 51 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 51 satisfies the conditions of the gap changing part 50 already described, as shown in FIGS. 5 and 6, a groove-like gap 52 is provided in the radial direction in the axial direction, or Alternatively, it can be formed as a hole.

Further, as shown in FIG. 7, a circulation hole 53 for the oil 15 may be provided to connect between the two radial bearings 24 and the outside of each radial bearing 24. Since the dynamic pressure generated in the radial dynamic pressure bearing 24 is very large,
If the dynamic pressure becomes unbalanced, oil leak pressure may be generated. On the other hand, by connecting the two radial bearings 24 and the outside of each radial bearing 24 with the circulation hole 53, it is possible to eliminate the pressure difference due to the dynamic pressure and prevent leakage. Further, also in the gap changing portion 50, the holding pressure of the single bag structure is effectively utilized.

Further, although not shown, the gap changing portion 5
A groove or a ridge extending in the axial direction may be provided from 0 to the outside thereof. With this configuration, when air is mixed in the oil 15 for some reason, the oil 1
The condition that the exchange of 5 and the air can be done smoothly is made,
The air can be pushed out more reliably. This is because if there are grooves or ridges, the oil 15 moves to the side with a narrower gap and the air moves to the side with a wider gap due to 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 and air can move along the groove or ridge separately without colliding, and the oil and air can be replaced more smoothly. You can

Further, it is desirable to set the ratio of air to oil in the bearing space to 2% or less. When air is mixed in the oil, since air is a gas, its volume is inversely proportional to pressure and proportional to absolute temperature. For this reason, oil may leak or become insufficient due to changes in atmospheric pressure and temperature unless the proportion of the mixed air is kept below a certain level. If this ratio is suppressed to 2% or less by the vacuum injection method or the like, the oil capacity including the entrained air is increased by 2% or less even when it is reduced to 0.5 atm, and 0.4% or less when it is increased by 60 ° C. Increased, bag part and gap change part 5
From the capacity ratio of 0, these changes can be sufficiently absorbed.

Next, in the embodiment shown in FIG. 8, the magnetic fluid 15 'is used as oil, and the magnet 53 magnetized in the radial direction is arranged in the gap changing portion 50 to rotate it. A magnetic circuit is formed between the shaft 31 and the shaft 31. The seal plate 5 is located outside the magnet 53.
4 are provided. The magnetic circuit includes the gap changing portion 50.
The inner end side of the gap is strong because it is close to the rotary shaft 31, while the outer end side of the gap changing portion 50 is set to be weak because the gap is wide between the rotary shaft 31 and the gap changing portion 50. Is formed so that the magnetic field has a constant magnetic flux density gradient in almost one direction in at least half of the above.

By setting the magnetic conditions as described above and configuring the gap changing portion 50 as described above,
The magnetic fluid 15 ′ is not only leaked by the action of the gap changing portion 50 but also by the magnetic force exerted toward the inside. Further, by keeping the gradient of the magnetic flux density constant, even if the surface position 15′a of the magnetic fluid 15 ′ changes to some extent, a magnetic force of a certain level or more is surely applied.

[0057]

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.

Further, according to the present invention, since the inner volume of the gap changing portion is set larger than the inner volume of the bag portion and the inner volume of the radial bearing portion and the thrust bearing portion, the variation of the oil injection amount and the internal volume Even if there are variations, changes in the internal volume due to floating or heat generation of the thrust bearing due to rotation, etc., or changes in the oil volume due to evaporation or internal mixed air, the oil is always retained in the bearing and leaks to the outside. I will not put it out.

Further, in the present invention, 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 to the outside due to the pressure difference due to the gap ratio, and the mixed state is eliminated. Further, the gap ratio makes it easy to stabilize the oil at any position.

[Brief description of drawings]

FIG. 1 is a semi-transverse sectional view showing a structure in which a bearing seal device according to an embodiment of the present invention is applied to an HDD motor.

FIG. 2 is a semi-transverse cross-sectional explanatory view showing a bearing sealing device according to an embodiment of the present invention.

FIG. 3 is an explanatory view showing an enlarged main part of the seal device for a bearing of the present invention shown in FIG.

FIG. 4 is a semi-transverse cross-sectional explanatory view showing an enlarged main part of a bearing seal device according to another embodiment of the present invention.

FIG. 5 is an enlarged plan view showing a main part of a seal device for a bearing according to another embodiment of the present invention.

6 is an explanatory view of a half cross section of the seal device for the bearing shown in FIG.

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

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

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

[Explanation of symbols]

 50 Gap changing part 40 Bag part Gap inclination angle

Claims (14)

[Claims] 1. A pair of radial bearing portions provided in the bag portion by inserting a shaft formed on one side of the rotating member and the fixed member into a substantially cylindrical bag portion formed on the other side. The bearing in which the rotating member and the fixed member are rotatably supported by each other, a gap changing portion is provided on the axially outer side of the radial bearing portion, and oil is filled from the inside of the bag portion to the gap changing portion. The seal changing device according to claim 1, wherein the gap changing portion has: 1) a minimum gap in the gap changing portion at an inner end of the gap changing portion on the radial bearing portion side, and a gap changing portion outside of the radial bearing portion. 2) When the angle of the gap changing portion with respect to the axis as viewed from the bag portion side is a gap inclination angle, the gap changing portion has an inner end from the gap changing portion outer end. Gap clearance The angle is 0 ° or more, and 3) the outer end of the gap changing portion has a gap of 0.8 m with the shaft.
m or less and the gap inclination angle is 45 ° or less, 4) The content of the gap changing portion is 5% or more of the content of the bag portion, and the content of the radial bearing portion is 5% or more. On the other hand, it is set to 100% or more, and the radial gap at the outer end of the gap change portion is set to be at least twice as large as the radial gap at the inner end of the gap change portion. . 2. The bearing seal device according to claim 1, further comprising an oil circulation hole for circulating oil connecting between both ends of the radial bearing portion in the bag portion. apparatus. 3. The bearing sealing device according to claim 1, wherein a groove extending in the axial direction is provided from the gap changing portion to the outer side thereof. 4. The bearing sealing device according to claim 1, wherein the gap change portion is filled with a 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 seal device for a bearing, wherein a magnetic circuit is formed so that a magnetic field having a constant magnetic flux density gradient in almost one direction is formed in at least half of the gap changing portion. 5. The bearing seal device according to claim 1, wherein 2/3 or more of the gap change portion in the axial direction section is set to a parallel gap within a gap size of 0.4 mm. Sealing device. 6. 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. 7. 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. 8. The bearing seal device according to claim 1, wherein the difference between the contact angle of the oil on the rotating member side and the contact angle of the oil on the fixed member side in the gap changing portion is set to 15 ° or less. Characteristic bearing seal device. 9. The bearing seal device according to claim 1, wherein the inner wall surface of the gap change portion is formed of a low surface tension plastic material. 10. The bearing sealing device according to claim 1, 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. 11. 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 an inner end of the gap change portion toward an outer end of the gap change portion. Bearing seal device. 12. The bearing seal device according to claim 1, wherein an average gap inclination angle in the gap change portion is set to 10 ° or more. 13. The bearing seal device according to claim 1, wherein the gap inclination angle in the gap change portion is formed substantially constant, and the cross-section is formed on a straight inner wall surface. . 14. 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.