JPH08232966A - Sealing device of bearing - Google Patents

Abstract

PURPOSE: To hold stably even when injected oil quantity changes and moves by making a device furnished with a thrust bearing with a middle hole in basic structure and setting a clearance changing part of a bearing part at a specific value. CONSTITUTION: The minimum clearance is provided at a clearance changing part 56 on a clearance changing part inner end 56a on the side of a bearing part 57, and the maximum clearance is provided on a clearance changing part outer end 56b. Clearance inclination from the clearance changing part inner end 56a to the clearance changing part outer end 56b is set at 0 deg. or more. A clearance of the clearance changing part outer end 56b against a oppositely facing surface is 0.8mm or less and positioned at clearance inclination 45 deg. or less, and a clearance total of the bearing part 57 in the axial direction is st at 200μm or less. Additionally, total content quantity of the clearance changing part 56 against total content quantity of a thrust bearing part 5 is set as 100% or more and total content quantity of the clearance changing part 56 is set as 30% or more against total content quantity from one of the clearance changing parts to the other clearance changing part respectively. Thereafter, clearance measurement of the clearance changing part outer end 56b is set three times or more of clearance measurement of the clearance changing part inner end 56a.

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 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. The motor shown in FIG. 4 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. In this motor, a hub 4 is rotatably mounted on a fixed shaft 2 fixed to a frame 1 via a radial bearing 3 and a thrust bearing 5. The thrust bearing 5 is axially opposed to the thrust bearing plate 6, and oil as a rotary lubricant is supplied into the gap between the thrust bearing 5 and the thrust bearing plate 6. This oil adheres to the bearing portion of the thrust bearing 5 and is held by the 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, This causes a problem of oil leakage, 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-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 has a basic structure of a device provided with a thrust bearing having a bore, and includes contents for satisfying the above conditions. The thrust bearing that rotatably supports the fixed member and the rotating member relative to each other is formed by an annular groove portion that extends in the radial direction and a thrust disc that is rotatably inserted into the groove portion. The thrust bearing is provided with a dynamic pressure generating groove formed on at least one of the four axially facing surfaces of the annular groove portion and the thrust disk, and the facing surface thereof. A thrust bearing portion is provided, and the thrust bearing faces the axial direction 4
A gap change portion that opens to the outside is provided on each of the inner diameter sides of the two gaps formed by the surfaces, oil is filled from one gap change portion of the two gaps to the other gap change portion, and A seal device for a bearing provided with a hole that axially communicates between the gap change portion and the thrust bearing portion in the gap, wherein the gap change portion comprises:
1) A minimum gap in the gap change portion is provided at the inner end of the gap change portion on the bearing portion side, and a maximum gap is provided at the outer end of the gap change portion on the opposite side of the bearing portion 2). When the angle of the gap changing portion viewed from the bearing 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,
3) At the outer end of the gap changing portion, the gap between the facing surface of the gap changing portion is 0.8 mm or less and the gap inclination angle is 45 ° or less, and 4) the total axial clearance of the bearing portion is , 200 μm or less, the total inner volume of the gap changing portion with respect to the total inner volume of the thrust bearing portion is set to 100% or more, and the total inner volume of the gap changing portion is set to one of the above. It is set to 30% or more of the total internal capacity from the gap change portion to the other gap change portion, and the gap size of the outer end of the gap change portion is set to be three times or more the gap size of the inner end of the gap change portion. Have the means

In the present invention, there are two oil outlets, but the two outlets form a pseudo single-bag structure in the direction orthogonal to the axis of rotation so that the advantages of the single-bag structure can be utilized. There is. That is, by providing a gap change portion at two oil outlets and providing a hole for communicating both gap change portions in the axial direction, the oil pressure is made substantially the same,
As a result, an action equivalent to that of the single bag structure is obtained, and the pressure due to the centrifugal force is entirely supported by the single bag portion.

[0007] Specifically, oil is filled from the annular groove portion to both gap changing portions located at the outlet portion, and the gap of the gap changing portion is 0.8 mm or less and the outer end of the gap changing portion is The gap inclination angle is set to 45 ° or less, which makes it difficult for air to mix in the oil, which is stable and difficult to leak.

Further, according to the present invention, the inner volume of the gap changing portion is set to be larger than the inner volume of the annular bag-shaped groove portion and the inner volume of the thrust bearing portion, and the thrust bearing of the thrust bearing due to variations in oil injection amount and inner volume, rotation, etc. Even if the internal volume changes due to levitation or heat generation, or the oil volume changes due to evaporation or internal mixed air, the oil is always retained in the bearing portion and does not leak to the outside.

Further, in the present invention, a large gap ratio between the inner end and the outer end of the gap change portion is set, and even if air is mixed in the oil surface portion, it does not move to the bearing portion, Air naturally moves to the outlet side 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.

Further, according to the present invention, as described above, the total of the axial clearances in the bearing portion is set to 200 μm or less, whereby the movement in the thrust direction is practically suppressed and the gap having the greatest influence is obtained. The change of is suppressed and the oil is held well.

[0011]

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 looking at 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, if the capillary suction pressure is A and B,
The oil moves from the position of A = B to the position of (A = B + external pressure), and the movement of the oil stops in a balanced state.

In such a structure in which the outlets are in two directions, 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 examination, the pseudo single bag structure shown as the embodiment of the present invention (the annular groove extending in the radial direction in the space from the outlet on one side to the outlet on the other side and the groove portion) A bearing sealing device having a space defined by a thrust disk inserted relatively rotatably and having a radially outer peripheral end closed) has a structure in which the outlet is in two directions. Different, 1 on the opposite side of the exit
The structure that can be seen as a wall that holds and generates atmospheric pressure 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.

Now, an embodiment of the present invention that embodies the above effects will be described in detail below with reference to the drawings.

The HDD motor shown in FIG. 4 is a typical example of a device to which the sealing device of the present invention is applied. As described above, the radial bearing 3 and the thrust bearing 5 are mounted on the fixed shaft 2 fixed to the frame 1. The hub 4 is rotatably mounted via the. The thrust bearing 5 is axially opposed to the thrust bearing plate 6, and oil as a rotary lubricant is supplied into the gap between the thrust bearing 5 and the thrust bearing plate 6.

More specifically, as shown in FIGS. 1 and 4, the thrust bearing 5 is mounted on the fixed shaft 2 in a radially extending annular bag-shaped groove 51 formed on the hub 4 side. An integrally formed thrust disk 52 is rotatably inserted, and oil 7 is continuously filled in a gap between the annular bag-shaped groove portion 51 and the thrust disk 52. In the thrust bearing 5, a dynamic pressure generating groove is normally formed on at least one of the four surfaces facing each other by the annular bag-shaped groove portion 51 and the thrust disk 52.

In the thrust bearing 5, the groove 5
On the small diameter side (center side) of the two gaps 53, 54 formed by the four axially opposed surfaces of 1 and the thrust disk 52, the gap changing portion 5 opened to the external passage along the fixed shaft 2.
6, 56 are provided respectively. That is, the gaps 53, 54 in the thrust bearing 5 are the thrust bearing portion 57, the gap changing portion 56 provided on the small diameter side (center side) of the bearing portion 57 and satisfying the following conditions, and these bearing portions. 57 and a small diameter side inner space portion 58 for oil storage formed between the gap changing portion 56, a small diameter outer space portion 59 formed on the small diameter side of the gap changing portion 56, two gaps 53, 54 and a large-diameter side inner space portion 60 communicating with each other. The small-diameter side inner space portion 58 for storing the oil may be omitted.

The oil 7 is continuously filled from the one gap changing portion 56 to the other gap changing portion 56, and the small-diameter side inner space portions 58, 58 are axially connected by the inner hole 8. It is made to communicate.

Here, the gap changing portions 56, 56 are
It is formed as follows. That is, each gap changing portion 5
In Nos. 6 and 56, the bearing portion 57 side, that is, the innermost end on the large diameter side is the gap changing portion inner end 56a, and the outermost end on the outlet side, that is, the small diameter side is the gap changing portion outer end 56b.
The outer side of b, that is, the outlet side becomes the small-diameter side outer space portion 59. Further, when the angle α formed by the gap formed in the gap changing portion 56 at a predetermined horizontal position in the drawing as viewed from the bearing portion 57 side (back side) is a gap inclination angle, and the gap is parallel to the facing surface of the thrust disk 52. Is α = 0 °, and the angle α that spreads outward, that is, the upper left side in the drawing is set to be positive, and the angle α that spreads to the bearing portion 57 side, that is, the upper right side in the drawing, is set to be negative. The changing portion inner end 56a is narrowest, the gap changing portion outer end 56b is widest, and the gap inclination angle α from the gap changing portion inner end 56a to the gap changing portion outer end 56b is set to 0 ° or more. The gap inclination angle α of 0 ° indicates that a region parallel to the thrust disk 52 may be present in a part of the gap changing portion 56.

When there is a gap having a negative gap inclination angle α with the bearing portion, the gap changing portion inner end 56a is the outermost end in the axial direction 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 56b of the gap changing portion must be 0.8 mm or less,
The area exceeding 0.8 mm corresponds to the outer space portion 59 on the small diameter side, and the clearance inclination angle α at the point where the clearance is 0.8 mm is 4 mm.
In the case of 5 ° or more, 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 56b.

Further, in the embodiment of the present invention, the total of the axial clearances in the bearing portion 57 is 20.
It is set to 0 μm or less and the thrust bearing 5
Relative to the total internal capacity of the gap (capacity formed between the bearing 57 and the thrust disk 52) of the gap changing portion 56 (both gap changing portion inner ends 56a, 56a to both gap changing portion outer ends 5).
(Capacity formed between the thrust disc 52 up to 6b, 56b) is set to 100% or more, and the total internal volume of the gap changing portion 56 is the bearing portion 57 and the small diameter side inner space portion 5
8 and the outer space 60 on the large diameter side and the total inner volume of the bore 8 are 3
The gap change portion outer end 56b is set to 0% or more.
Is 3 with respect to the clearance dimension of the clearance changing portion inner end 56a.
It is set to more than double.

The operation of the bearing seal device according to the present invention having the above-described structure will be described. First, as a basic structure, there are two gap changing portions 56 serving as oil outlets. I try to take advantage of the single bag structure. Specifically, in the present embodiment, the small diameter side inner spaces 58, which act as oil reservoirs at two locations, are communicated with each other by the inner holes 8 so that the pressures are substantially the same and the gap changing portions 56, 56 at the two locations are connected. Since the external pressure is applied at substantially the same position in the radial direction as in the radial direction, the radial outer peripheral end (the large-diameter side outer space portion 60 side) in FIG. As can be seen, the oil 7 does not move even when an external force is applied from the radially inner side (left side in the figure) to the outer side (right side in the figure), so that the same action as the one-bag structure can be obtained. There is. Further, according to the above configuration, the advantage that the pressure due to the centrifugal force is entirely supported by the single bag portion can be obtained.

Therefore, it is not necessary to consider the oil movement due to the external force applied, and therefore the oil holding space by the gap changing portion 56 can be made small. 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, from the bearing portion 57 to the gap changing portion 5 at both ends.
6 and 56 are filled with oil 7, the gap between the gap changing portions 56 and 56 and the thrust disk 52 is 0.8 mm or less, and the gap inclination angle α of the gap changing portion outer ends 56b and 56b is 4 mm.
The outer end 5 of the gap changing portion 56 is set to 5 ° or less.
Since the gap size at 6b and 56 is set to be three times or more as large as the gap size at the inner ends 56a and 56, it becomes difficult for air to be mixed into the oil 7 and the bearing sealing device is stable and does not leak easily. There is. That is, the gap change portion inner end 56
Since the gap ratio between a and the outer end 56b is large and the gap inclination angle α is provided, even if air is mixed in the oil surface portion 7a located in the gap changing portion 56, the air is mixed with the bearing. The air does not move to the outside, and due to the pressure difference due to the gap ratio, the air naturally moves to the outside, and the mixed state is eliminated.

As already described, the thrust bearing 5
Since the inner volume of the gap changing portions 56, 56 is larger than the inner volume of the hub, even if the amount of oil injected or the inner volume of the thrust bearing 5 at the time of manufacture varies, the hub as a rotating body can also be used. Even if there is a change in the internal capacity of the thrust bearing 5 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 7 due to evaporation or air mixed in the inside will occur. However, the thrust bearing 5 always holds the oil 7 and does not leak to the outside.

Further, as described above, the total axial clearance in the bearing portion 57 is set to 200 μm or less, so that the movement in the thrust direction is suppressed and the change in the gap that greatly affects the oil is suppressed. The oil is well retained.

Further, in the embodiment of the present invention, the amount of oil injected into the thrust bearing 5 is 0. 0 from the gap change portion inner end 56a when the stationary state is stable, when the internal volume of the gap change portion 56 is A. The amount is set to a position between 1A and 0.9A.

That is, basically, if the oil surface 7a is located in the gap changing portion 56, it is stably held and no problem occurs, but the amount of oil, the internal capacity, etc. may change depending on time and environment. In order to prevent oil shortage and oil leakage, it is possible to maintain sufficient performance in a normally used environment by filling the amount of oil (position of the oil surface 7a) in the gap changing portion 56 within the above range. can do.

Further, in the embodiment of the present invention, as shown in FIG. 5, the contact angle θ between the oil 7 and the thrust disk 52 as a fixing member in both gap changing portions 56, 56.
1 and the gap changing portion 56 itself as the rotating member and the oil 7
It is desirable to set both the contact angle θ1 with and 15 ° or more. The fact that the oil surface 7a is located inside the gap changing portion 56 means that the oil 7 contacts the thrust disk 52 and the gap changing portion 56 itself at a certain contact angle θ1, so that the contact angle θ1 should be 15 ° or more. Set it.

Next, as a result of various studies by the present inventor, in order to prevent leakage of the oil 7 to the outside, it is necessary to prevent 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 wet expansion (clipping phenomenon), it is necessary to create a state in which the oil does not cause the wet expansion 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 certain solid surface and the 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 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) 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.

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 (γS> γL + γSL) is satisfied in this way, 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 θ 1 between the thrust disk 52 and the oil 7 in both the gap changing portions 56, 56 and the contact angle θ 1 between the gap changing portion 56 itself and the oil 7 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, if the inner wall surfaces of the gap changing portions 56, 56 are made of a low surface tension plastic material,
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 56,
It can be formed on the inner wall surface of 56 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 56, 56.

Further, if the difference between the contact angle θ1 of the oil with respect to the thrust disk 52 and the contact angle θ1 of the oil with respect to the gap changing part 56 itself in both gap changing portions 56, 56 is small, it becomes difficult to leak, so this difference is 15 ° or less. It is better to set to.

On the other hand, the gap changing portions 56, 56 are arranged in the bearing direction from the bearing portion 57 side toward the small diameter side outer space portion 59 side.
The gap is formed to open at an angle of 5 ° or less, and the inclination angle of the gap outside the gap changing portions 56, 56 is also extended to 45 ° or less. By doing so, even if the oil 7 should rise above the originally designed position of the gap changing portions 56, 56 (move to the left in the drawing), the solid surface of the gap changing portions 56, 56 and the oil 7 may be changed. A stable state can be obtained and the oil 7 can be prevented from leaking.

Further, in this embodiment, in order to reduce the surface roughness of the solid surface, the surface roughness Ra of the inner wall surfaces of the gap changing portions 56, 56 is set to 0.25 μm or less. If there are irregularities on the inner wall surfaces of both gap change parts 56, 56,
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 56, 56 to be small, the substantial contact angle between the solid and the liquid can be increased and the leakage can be prevented. Thus, the surface roughness Ra is 0.2
The setting of 5 μm or less is also applied to the thrust disk 52 side as needed.

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 both gap changing portions 56, 56 to the outside, the unevenness (surface roughness) is as small as possible,
It is necessary to minimize dirt (uneven surface tension).

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

If there are irregularities, 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 56 of the gap changing portions 56, 56.
When the position within 1/2 of the axial length of the gap changing portions 56, 56 from b, 56b is set as the reference position, the inner wall surface extending from the reference position to the outside is the bearing portion 5 from the reference position.
Contact angle θ that is at least 15 ° larger than the inner wall surface on side 7
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.

In the bearing device using the bearing seal device of the present invention, the dynamic pressure generating groove formed in the bearing portion 57 causes the dynamic pressure in the direction to cancel the centrifugal force outwardly acting on the oil 7 in the radial direction. Is configured to obtain. That is, both the centrifugal force and the dynamic pressure are pressures that are generated when they start to rotate, and stability can be obtained by a configuration in which they cancel each other out.

Further, in the embodiment of the present invention, the outer end (left end in the figure) of the dynamic pressure generating groove of the thrust bearing portion 57 may be extended to the inner end 56a of the gap changing portion 56. . If the dynamic pressure generating groove is configured to extend to the inner end 56a of the gap changing portion as described above, the gap inclination angle α from the thrust bearing portion 57 is always in the state of α ≧ 0 °, and air is injected when oil is injected. It becomes difficult for the oil 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.

Furthermore, in the embodiment of the present invention, the gap inclination angle α in the gap changing portion 56 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 shown in FIGS. 2 and 3, the thrust disk 52 facing the gap changing portion 56 on the upper side of FIG. 2 satisfies the above-mentioned gap changing portion conditions. The gap 56c is added in the axial direction. By providing the gap 56c in the axial direction in this way, the internal capacity for retaining oil can be increased, and in particular, by keeping the gap 56c smaller than the outer end width of the gap changing portion 56, the oil 7 in the gap 56c is prevented. It is surely held. Further, since the gap 56c in the axial direction does not have a dimension in the thrust bearing direction, the dimension in the thrust bearing direction can be suppressed and
Impact resistance is advantageous.

The gap 56c at this time can be provided only on one side of both gap changing portions 56. Further, as shown in conjunction with FIG. 2, the gap 56d in the axial direction may be formed in the gap changing portion 56, or may be formed in a hole shape. These cases are similar to the above cases, but especially in the case of holes, the ratio of the solid surface to the capacity increases and the pressure generated by the capillary phenomenon doubles, so the hole radius is different from the gap when facing each other. Corresponds.

Further, in the present invention, the gap dimension 0.
The parallel gap may be set within 4 mm (gap inclination angle α = 0 °). With such a shape, a large space can be provided in the gap changing portion 56, more variations and changes in the oil 7 can be absorbed, and the gap distance in the parallel gap portion can be suppressed to a small value, which is difficult to leak. Will be secured.

Returning again to the embodiment shown in FIG.
As shown by the broken line in the middle, the oil circulation hole 61 may be provided in a substantially T shape so as to connect the large diameter side inner space portion 60 and the small diameter side inner space portion 58. That is, since the dynamic pressure generated inside is very large, leak pressure may be created in some cases. By connecting both sides of the thrust bearing portion 57 with the circulation hole 61 as in the present embodiment, the pressure difference is minimized, which is effective in preventing leakage.

Further, in the present invention, although not shown, a groove or a convex strip extending in the radial direction from the gap changing portion 56 to the outside thereof is provided. With this configuration, when the air is mixed for some reason, the oil 7 and the air can be smoothly exchanged, and the air can be more reliably pushed out. The reason for this is that if there are grooves or convex stripes, the oil 7 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 radial direction, the oil and air can move separately along the groove or ridge without hitting each other, and the oil and air can be replaced more smoothly. You can

On the other hand, in the present invention, the inner end 5 of the gap changing portion is
The oil contact angle at 6a is configured to be 45 ° or less. That is, the smaller the contact angle of the narrowest gap portion that generates the maximum holding pressure, the larger the pressure that can be generated, which is about 70% at 45 °, and it is necessary to suppress the contact angle to this extent.

Further, in the present invention, the average gap inclination angle in the gap changing portion 56 is preferably set to 10 ° or more. That is, in order to prevent the movement of the oil 7 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.

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 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.

[0062]

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, in the present invention, since the inner volume of the gap changing portion is set larger than the inner volume of the entire annular bag-shaped groove portion, the variation of the oil injection amount, the variation of the internal volume,
Even if there is a change in the internal volume due to floating 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, oil is always retained in the bearing,
In addition, it does not leak outside.

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 main part of 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 a plan explanatory view of the bearing device according to the embodiment shown in FIG.

FIG. 4 is a transverse cross-sectional view showing a typical example of a device to which the sealing device according to the embodiment of the present invention is applied.

FIG. 5 is a semi-transverse cross-sectional explanatory view showing, on an enlarged scale, the gap changing portion on the upper side in the embodiment shown in FIG.

[Explanation of symbols]

 5 Radial bearing 56 Gap changing part 57 Bearing part 58 Small diameter side inner space part 59 Small diameter side outer space part 60 Large diameter side inner space part

Claims (12)

[Claims] 1. A thrust bearing for rotatably supporting a fixed member and a rotary member relatively rotatably, and an annular groove portion extending in a radial direction, and a thrust disc rotatably inserted in the groove portion. The thrust bearing is constituted by a dynamic pressure generating groove formed on at least one of the four surfaces of the annular groove portion and the thrust disk that face each other in the axial direction, and the facing surface thereof. A thrust bearing portion, and a gap changing portion that opens to the outside is provided on each of the inner diameter sides of the two gaps formed by the four axially opposed surfaces of the thrust bearing. One of the two gaps is changed. A seal device for a bearing, in which oil is filled from one portion to the other gap change portion, and holes are provided for axially communicating the gap change portion and the thrust bearing portion in both the gaps. , 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 bearing portion side, and a maximum in the gap changing portion at an outer end of the gap changing portion on the side opposite to the bearing portion. 2) When the angle of the gap changing portion viewed from the bearing 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. Yes, 3) At the outer end of the gap changing portion, the gap with respect to the facing surface of the gap changing portion is 0.8 mm or less, and the gap inclination angle is 45 °.
The following positions, 4) The total axial clearance in the bearing is
It is set to 200 μm or less, the total inner volume of the gap changing portion with respect to the total inner volume of the thrust bearing portion is set to 100% or more, and the total inner volume of the gap changing portion is set to one of the gaps. It is set to 30% or more with respect to the total internal capacity from the changing portion to the other gap changing portion, and the gap size at the outer end of the gap changing portion is set to be three times or more as large as the gap size at the inner end of the gap changing portion. The bearing sealing device is characterized by being. 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 seal device according to claim 1, wherein the dynamic pressure generating groove formed in the bearing portion is configured to obtain a dynamic pressure in a direction for canceling a centrifugal force acting on the oil. Characteristic bearing seal device. 8. The bearing seal 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. 9. The bearing seal device according to claim 1, wherein 2/3 or more of the gap change portion is set to a parallel gap having a gap dimension of 0.4 mm or less. 10. 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. 11. The bearing sealing device according to claim 10, 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. 12. The bearing seal device according to claim 10, wherein an average gap inclination angle in the gap change portion is set to 10 ° or more.