WO2021130895A1

WO2021130895A1 - Fluid bearing

Info

Publication number: WO2021130895A1
Application number: PCT/JP2019/050808
Authority: WO
Inventors: 村上　幸義
Original assignee: 村上　幸義
Priority date: 2019-12-25
Filing date: 2019-12-25
Publication date: 2021-07-01
Also published as: JPWO2021130895A1; JP6814912B1

Abstract

[Problem] The present invention pertains to a fluid bearing used in a hard disk, a cooling fan, etc., and more specifically, to an oil-containing fluid bearing that avoids integration and has enhanced exchangeability and versatility as a component. [Solution] A fluid bearing according to the present invention is a fluid bearing 1 that comprises a bearing body 5 formed of an oil-containing porous sintered body and has arranged therein an outer ring 2 and an inner ring 3, the periphery of the bearing body 5 being covered by a seal cover 4. The fluid bearing 1 is characterized in that: side surfaces of the bearing body 5 are sealed with shielding films 6; an inclined groove 2a, which has inclined surfaces, is engraved into the outer ring 2 to form an oil pressure space α for guiding oil, which flows in due to a centrifugal force, in a rotational transverse direction between the bearing body 5 and the outer ring 2; blades are mounted to the side surfaces of the bearing body 5 to form an air pressure space β for guiding the air from the blades 7a in the rotational transverse direction between the bearing body 5 and the seal cover 4; and the oil pressure produced in the oil pressure space α and the air pressure produced in the air pressure space β confront each other at the contact portion of the bearing body and the outer ring so as to balance the pressures with each other.

Description

Fluid bearing

The present invention relates to a fluid bearing used for a hard disk, a cooling fan, etc., and more particularly to an oil-impregnated fluid bearing having improved interchangeability and versatility as a component by avoiding integration.

Today, bearings used in information devices such as hard disks of servers and PCs are strongly required to be quiet and improve rotational accuracy, and ball bearings have limitations. Therefore, fluid bearings have been proposed as an alternative.
There are two types of fluid bearings: dynamic pressure type, static pressure type, and static pressure type. The dynamic pressure type applies pressure to the fluid by rotation and inserts the fluid into the gap between the shaft and the rotating body to connect the shaft and the bearing. It is intended to obtain smooth rotation between the bearings, but when the rotation is low, the fluid is insufficient, and friction and NRRO are likely to occur. Therefore, there is a drawback that it can be applied only to a constant high-speed rotation.
The static pressure type adopts a method of introducing an external pump and preliminarily flowing fluid in the shaft and bearing by the pump pressure, and while relatively stable operation can be obtained, the equipment becomes large and maintenance is performed. Will be a big deal.
The static pressure type operates an external pump at low speeds and tries to use the dynamic pressure at high speeds, and stable operation can be obtained over a relatively wide range. The same is true.
And since all of these are integrated, the equipment becomes large, the bearing part cannot be handled as a part, it lacks versatility, it is not easy to replace or repair, and it is extremely costly. Become.
By the way, in this fluid bearing, a technique called an oil-impregnated sintered bearing has been developed (for example, Patent Document 1). The outline is that a sintered body with holes is impregnated with lubricating oil, an oil film of lubricating oil is held on the friction surface between the rotating shaft and the bearing, and the lubricity of the oil film alleviates friction and makes it smooth. It is intended to encourage rotation.
However, the fact that external pressure is required to hold the oil film is the same as in the above-mentioned dynamic pressure type and static pressure type, and the vacant sintered body is immersed in the sealed oil-liquid layer. Yes, there is no change in the size of the integrated type and the difficulty of replacing parts.

Japanese Patent No. 5384014

Therefore, the present invention makes it possible to hold an oil film by internal pressure without relying on external power by using a sinterable bearing body having this oil-containing property and adding a unique device to the bearing body. , We propose a fluid bearing that avoids integration and enhances interchangeability and versatility as a part.

The fluid bearing according to claim 1 includes a bearing body formed of an oil-impregnated porous sintered body, and has an outer ring on the outer side and an inner ring on the inner side, and the periphery thereof is covered with a seal cover. A fluid bearing to be fitted, the bearing body having a substantially square cross section and its side surface sealed with a shielding film, and a slanted wall groove having an inclined surface in which the central portion of the outer ring serves as a valley bottom is carved. A hydraulic space α is formed between the bearing body and the outer ring to guide the oil flowing in by the centrifugal force generated by the rotation of the bearing body in the lateral rotation direction, and the blades are on the outer ring side on the side surface of the bearing body. A wind turbine facing toward the surface is mounted on the side surface of the bearing body, and a wind pressure space β that guides the wind generated by the rotation of the wind turbine in the rotation vertical direction is formed between the bearing body and the seal cover, and the above hydraulic space α is formed. The feature is that the hydraulic pressure generated in the bearing body and the wind pressure generated in the wind pressure space β face each other at the contact portion between the bearing body and the outer ring so that the mutual pressures are balanced.

In the fluid bearing according to claim 2, a concave groove is carved in the central portion of the inner ring, and oil that flows back due to a negative pressure generated by stopping the rotation of the bearing body is stored between the bearing body and the inner ring. It is characterized by forming an oil reservoir space γ.

The fluid bearing according to claim 3 is characterized in that a holding member is provided on a part of the inner ring and a seal ring is arranged between the inner ring and the holding member.

When the bearing starts to rotate, centrifugal force acts on the bearing body formed of the oil-containing porous sintered body, and the impregnated oil flows. The direction of the flow is a radial direction toward the outer ring side, which is a rotation vertical direction once orthogonal to the shaft body.
At the same time, a part of the flow goes to the side surface of the bearing body facing the seal cover side, but since the side surface of the bearing body is provided with a shielding film, the flow is sealed there, reflected and returned. Since the centrifugal force acts there, it joins the flow in the radial direction and becomes a flow toward the outer ring.

Then, when the flow of oil stored in the porous material reaches a certain amount, the tip of the oil flow overflows beyond the surface of the bearing body and enters the hydraulic space α.
The invading oil flows in the hydraulic space α, but it goes to the central part of the slanted wall groove that became the valley bottom, and each flow concentrates there. Then, they collide with each other in the middle, a reaction force is generated there, and the flowing oil flows along the inclined surface of the inclined wall groove in the thrust direction converted in the rotational lateral direction.
The flow in the converted thrust direction goes toward the peripheral edge portion, and eventually enters a narrow gap where the bearing body and the outer ring come into contact with each other.

On the other hand, on the wind pressure hydraulic space α side, since a wind turbine whose blades are directed toward the outer ring side is mounted on the side surface of the bearing body, the wind turbine rotates with the rotation of the bearing body, and a wind flow is induced.
Since the blades are formed toward the outer ring, the wind flows in the wind pressure space in the radial direction, which is the vertical rotation direction, and presses the narrow gap that is the contact portion between the bearing body and the outer ring. ..

Then, in the contact portion which becomes the narrow gap, the oil pressure in the thrust direction and the wind pressure in the radial direction confront each other, and the pressures antagonize each other and maintain a balanced state.
As a result, even if the oil flow on the hydraulic space α side is continued as it is, the oil flow is sealed by the wind turbine and does not leak beyond the gap.
At the same time, the oil that has entered the gap is continuously pressurized by the action of the hydraulic space α, and due to the pressure, an oil film is stably formed between the contact part and the gap, and the bearing body and the outer ring No contact or friction occurs between the two, and smooth rotation can be continuously obtained.

In addition to the stable formation of an oil film under this pressure, when the bearing body rotates at low speed, the oil-impregnated bearing body functions as a sliding bearing and can maintain smooth rotation, from high speed to low speed. It is possible to handle rotation in a wide range.

Further, since the inclined wall groove of the hydraulic space α has a symmetrical shape about the center line of the valley, the oil flowing into the symmetrical valley bottom is concentrated in the central part while being balanced, which has a centering effect on the bearing body. This results in the elimination of shaking of the entire fluid bearing due to left-right imbalance, and avoids phenomena such as lateral displacement of the outer ring and inner ring and NRRO.

Since each action and effect relies on the centrifugal force associated with the rotation of the shaft body linked to the drive of the motor, there is no need to add an external power source, and everything is autonomous. It will be something like that.

When trying to replace it as a part, by removing the inner ring fitted to the shaft body, the entire fluid bearing can be replaced, it becomes easier to deal with failures and maintenance, and a great cost saving effect can be obtained.

According to the fluid bearing according to claim 2, the oil that flows back due to the negative pressure generated by the stop of the rotation of the bearing body can be stored in the oil reservoir space γ, and the flow of the entire oil during the backflow and the rotation can be increased. It can be smoothed.

According to the fluid bearing according to claim 3, it is possible to improve the airtightness and improve the suction force due to the negative pressure generated in the bearing sintered body when the rotation is stopped.

It is an overall side view of the fluid bearing of this invention. It is an enlarged sectional view of the main part of this invention. In a schematic side view showing the oil flow state in the main part of the present invention, (a) is when the oil starts to flow, (b) is when the oil overflows into the hydraulic space, and (c) is the wind flow. Indicates the start time. In the schematic side view of the same as above, (d) shows a state where the oil pressure and the wind pressure face each other, and (e) shows a state where the oil flows backward.

Hereinafter, the best embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the fluid bearing 1 of the present invention is roughly fitted to a shaft body A which is a shaft connected to a motor, and has an outer ring 2 framed from the outside and an inner ring 3 framed from the inside. It is composed of a seal cover 4 covering the side surface and a bearing body 5 formed of an oil-containing porous sintered body interposed between the outer ring 2 and the inner ring 3.
The inner ring 3 fitted to the shaft body A and the bearing body 5 coupled to the inner ring 3 are in a connected state, while the outer ring 2 coupled to the housing side and the seal cover 4 coupled to the outer ring 2 are in a connected state.

The bearing body 5 is a bearing body formed of an oil-containing porous material, and can be made of a porous material having holes such as a sintered metal, grown cast iron, or synthetic resin.
In the case of a sintered metal, a metal alloy powder that is press-molded and then fired at a high temperature to be molded can be used.
Porous means that it has holes inside, and the holes allow the lubricating oil to soak in and hold the oil, and the centrifugal force generated by the rotation of the shaft body A causes the oil to slowly flow in and out. It means that it has a hole diameter that allows it to be freely used.
Further, the oil used is a lubricating oil that reduces friction and has a viscosity sufficient to maintain the above-mentioned fluidity.

The shape of the bearing body 5 is an annular body that surrounds the shaft body A via the inner ring 3, and the cross-sectional shape thereof is substantially square. As shown in FIG. 2, the substantially square shape means that the outer surface 5a, the side surface 5b, and the inner surface 5c form a substantially flat shape toward the upper and lower outer ring 2, inner ring 3, and seal cover 4 side surfaces. A square shape is a typical example, but in relation to the hydraulic space α and the oil reservoir space γ, which will be described later, a slightly curved surface is allowed if it is a symmetrical shape centered on the valley bottom.

The outer side of the bearing body 5 is covered with a shielding film 6 on the side surface facing the seal cover 4.
The shielding film 6 refers to a film body having a function of sealing the flow of oil impregnated in the porous bearing body 5.
Specifically, as shown in the drawing, the film body is brought into close contact with the side surface of the bearing body 5, or the bearing body 5 and the wind turbine 7 are integrally molded in manufacturing and the film body is brought into close contact with the surface thereof. can do.
When the flow of oil moving by the action of the centrifugal force of the bearing body 5 tries to go to the seal cover 4 side, it plays a role of blocking the flow and directing it to the hydraulic space α side, which will be described later.

By the way, a hydraulic space α is formed between the bearing body 5 and the outer ring 2.
The hydraulic space α attempts to guide the oil in the vertical rotation direction (radial direction) that flows in due to the centrifugal force generated by the rotation of the bearing body 5 in the thrust direction that is the horizontal rotation direction, and is the central portion of the outer ring 2. Is formed by engraving a slanted wall groove 2a which serves as a valley bottom.
The central portion is a portion corresponding to the center of the outer ring 2 having a rectangular cross section, and a v-shaped inclined wall having a v-shaped cross section having a slanted inclined surface 2b whose central portion becomes a valley bottom and becomes shallow toward the peripheral portion 2c. It is formed in the groove 2a.
As shown in FIG. 2, the peripheral edge portion 2c is a widened portion in which the inclined surface 2b gradually approaches the side surface side of the bearing body 5 and eventually approaches a narrow gap that becomes a contact portion.
The slanted wall groove 2a has a valley shape with a v-shaped cross section as described above, but the slanted surface 2b has a symmetrical shape with the center line of the valley as the axis, and it is formed in an annular shape over the circumferential direction of the outer ring 2. To.
Then, a hydraulic space α having a constant volume is formed between the inclined wall groove 2a of the outer ring 2 and the bearing body 5. The constant volume means a volume suitable for guiding the oil flowing in by the centrifugal force generated by the rotation of the bearing body, which will be described later, in the thrust direction.

On the other hand, a wind pressure space β is formed between the bearing body 5 and the seal cover 4.
The wind pressure space β is intended to guide the wind generated by the rotation of the wind turbine 7 mounted on the bearing body 5 in the radial direction which is the rotation vertical direction, and the wind turbine 7 with the blades 7a facing the outer ring 2 side is the bearing body. It is formed by being attached to the side surface of the seal cover 5 facing the seal cover 4.
In the form of the wind turbine 7, the blades 7a are tilted toward the outer ring side to direct the flow of wind accompanying the rotation toward the outer ring 2.
The form of the blades 7a is determined in relation to the required wind pressure, and the number, length, inclination angle, etc. are set according to the purpose in consideration of the rotation speed of the shaft body A and the like.
It is desirable that the bearing body 5 be detachably attached, and the position thereof is fixed to the outside of the shielding film 6 attached to the side surface.

Further, an oil reservoir space γ can be provided between the bearing body 5 and the inner ring 3.
The oil reservoir space γ is intended to store oil that flows backward due to a negative pressure generated when the rotation of the bearing body 5 is stopped, and is formed by carving a concave groove 3a in which the central portion of the inner ring 3 is a depression. To.
The concave groove 3a is located on the opposite side of the slanted wall groove 2a of the outer ring 2, and stores the oil impregnated in the bearing body 5 when the shaft body A stops rotating and is stationary, so that a sufficient amount of flowing oil can be stored. Play a role in securing.
The shape of the groove is preferably a recess shape in which the central portion is the deepest, and is formed symmetrically with respect to the bottom portion of the concave groove 3a so that oil can be stably supplied when the bearing body 5 rotates.

A holding member 8 from which a part of the inner ring 3 is separated is attached to a part of the inner ring 3. The holding member 8 is a member for assembling and replacing the bearing body 5, and the bearing body 5 can be removed from the inside and replaced by removing the holding member 8 fitted to the inner ring 3.
A seal ring 9 such as an O-ring is fitted to the boundary between the inner ring 3 and the holding member 8 and the bearing body 5.
This is because the seal ring 9 is for sealing the inside of the bearing body 5, and if the bearing body 5 is not hermetically sealed, the oil pressure and the wind pressure will be hindered and the device will not function.
For the same purpose, the sealing material 4a and the ring 4b are also applied to the joint portion of the seal cover 4 with the outer ring 2.

When the inner ring 3 and the bearing body 5 are connected and the outer ring 2 and the seal cover 4 are connected, there is a slight amount between the lower end portion of the seal cover 4, which is the boundary between the inner ring 3 and the holding member 8. A gap is allowed so that the pressure of the wind pressure space β generated by the change in wind pressure can be adjusted and the rotation can be smoothed.

As a specific example, assuming mounting on a shaft body having a diameter of 8.0 mm, the width of the outer ring 2 is 6.0 mm, the thickness thereof is 0.95 mm, and the depth of the groove serving as the hydraulic space α is 20 μm. The groove width is 4.5 mm. The width of the inner ring 3 is 6.0 mm, the thickness thereof is 0.95 mm, the depth of the groove serving as the oil reservoir space γ is 15 μm, and the groove width is 3.0 mm. In the wind pressure space β, the blade 7a has a height of 0.5 mm, and the distance between the bearing body 5 and the seal cover 4 is 1.0 mm. The bearing body 5 has an inner diameter of 3.5 mm and a height of 2.5 mm, and the oil content of the porous sintered body can be about 10% to 35%.

Next, the operation and effect of the fluid bearing of the present invention will be described.
First, when the motor is started and the shaft body A starts to rotate, the bearing body 5 fixed to the shaft body A via the inner ring 3 is driven to start the rotation.
Then, due to the rotation of the bearing body 5, a centrifugal force acts inside the annular bearing body 5, and the lubricating oil impregnated in the bearing body 5 causes a radial flow along the centrifugal force. That is, since the bearing body 5 is porous and has holes formed inside the bearing body 5, when it rotates, centrifugal force acts on the oil stored in the holes, and the oil flows outward through the holes. Is evoked.
Since the flow is along the centrifugal force, it goes toward the outer ring 2 side along the shaft body A, and when the oil in the porous body moves, a part of the oil stored in the oil reservoir space γ is also accompanied. Moving.

At this time, a part of the oil flow also faces the side surface of the bearing body 5, to be exact, the side surface side facing the seal cover 4, but a shielding film 6 is provided on the side surface of the bearing body 5. Since there is, the flow is sealed there.
The sealed flow is reflected and returned, but since the centrifugal force acts on it, it joins the flow in the Rasil direction and becomes a flow toward the outer ring 2 (see FIG. 3A). ).

Then, when the flow of oil stored in the porous material reaches a certain amount, the tip of the oil flow overflows beyond the surface of the bearing body 5 and enters the hydraulic space α ( See FIG. 3 (b)).
The invading oil flows in the hydraulic space α, but it goes to the central part of the slanted wall groove 2a which is the bottom of the valley, and each flow concentrates there. That is, since the inclined surface 2b toward the valley bottom is formed symmetrically with respect to the central portion of the inclined wall groove 2a, it flows along the inclined surface 2b and is concentrated on the valley bottom while being balanced.
Then, when they are concentrated, they collide with each other in the middle, and a reaction force is generated there, and the counterforce causes the flowing oil to be in the thrust direction along the inclined surface 2b of the inclined wall groove 2a. It becomes a converted flow toward the peripheral portion 2c away from the center.
The flow in the converted thrust direction eventually reaches the tip end portion of the peripheral edge portion 2c, that is, the vicinity of the portion where the bearing body 5 and the outer ring 2 come into contact with each other.
The contact portion is formed by rubbing the v-shaped slanted wall groove 2a and the relatively flat bearing body 5 to form an extremely narrow gap, and the oil enters the narrow gap (FIG. 3). (C).

On the other hand, on the wind pressure space β side, the wind turbine 7 also rotates with the rotation of the shaft body A, and the blades 7a start to rotate in accordance with the rotation, which induces the flow of wind.
Since the blades 7a are formed toward the outer ring 2, the wind flows in the wind pressure space β in the radial direction, and eventually it creates a narrow gap that becomes a contact portion between the bearing body 5 and the outer ring 2. Press.

Then, in the contact portion that becomes the narrow gap, the oil pressure acting in the thrust direction and the wind pressure acting in the radial direction confront each other.
That is, as described above, the oil that has entered through the v-shaped slanted wall groove 2a exerts pressure on the oil due to the action of centrifugal force that continues to rotate, while the wind force that accompanies the rotation of the blades 7a is on the opposite side. The forces are opposed to each other at the contact points that form a narrow gap, and the forces antagonize each other to maintain a balanced state (see FIG. 4 (d)).

As a result, first, if the flow of oil on the hydraulic space α side is continued as it is, this will leak beyond the gap, but the wind pressure generated in the wind turbine 2 confronts and acts to seal it. To do.
As a result, the oil leakage of concern is prevented, which is maintained at all times as long as the rotation of the shaft body A is continued.
At this time, in principle, the equilibrium state is such that the oil pressure and the wind pressure are equal to each other, but if the wind pressure is slightly higher, the oil leakage can be completely sealed.

Then, as described above, the oil that has entered the gap is continuously hydraulically applied by the action accompanying the rotation of the shaft body A, and the pressure causes a stable oil film to be formed between the contact portion and the gap. That is, even if the oil enters the narrow space, if it is left as it is, the oil layer is pushed to one side due to the swinging due to the rotation of the shaft body, and the bearing body 5 and the outer ring 2 may come into contact with each other, resulting in a risk of friction. However, when hydraulic pressure is applied to the oil film, the force acts as a drag against rocking and the like, and the oil film can maintain a stable layer.
As a result, the bearing body 5 and the outer ring 2 do not come into contact with each other due to the stable action of the oil film, and smooth rotation can be continuously obtained.

At this time, in the slanted wall groove 2a of the hydraulic space α, as described above, the inclined surface 2b of the slanted wall groove 2a is symmetrical about the valley bottom, so that the oil flowing into the valley bottom at the center of symmetry is in the central portion. The bearing body 5 moves to the center and exerts a so-called centering effect.
As a result, the shaking of the entire fluid bearing due to the imbalance between the left and right sides is eliminated, and phenomena such as NRRO can be eliminated along with smooth rotation and quietness.

Next, when the operation is completed and the rotation of the shaft body A is stopped, the oil pressure applied to the hydraulic space α is released, and then the pressure difference between the hydraulic space α and the inner surface of the bearing body 5 is released. On the contrary, a negative pressure is generated in the bearing body 5.
Then, the oil stored in the hydraulic space α starts to flow back and is returned to the bearing body 5, while the surplus reaches the oil reservoir space γ and is stored (see FIG. 4 (e)).
As a result, a sufficient amount of oil is secured for the entire body including the bearing body 5, the buffer caused by the lack of oil and the deviation of the roundness of the inner and outer diameters are reduced, and the quietness is also improved.

In the case of a speed intermediate between the high-speed rotation and the rotation stop of the bearing body 5, the oil-impregnated bearing body functions as a sliding bearing, and thus can correspond to a wide range of rotation from low speed to high speed. ..

Further, since each of the above actions and effects depends on the centrifugal force accompanying the rotation of the shaft body A linked to the drive of the motor, it is not necessary to add an external power source. Everything becomes autonomous.
Therefore, the structural complexity of adding a power source is avoided, and the size is small and the operating cost is low.

At the time of replacement, the fluid bearing of the present invention becomes removable and can be replaced as a part by removing the outer ring 2 from the housing and removing the inner ring 2 fitted to the shaft body A. This indicates that it can be handled in the same way as a general rolling bearing.
Further, when only the bearing body 5 is to be replaced, the bearing body 5 can be pulled out from the inside by removing the holding member 8 and the cover ring 9 and removing the inner ring 3.
In the event of a failure or maintenance, it is sufficient to replace a part as a part instead of replacing the whole part, which is a great cost saving effect.

Claims

A fluid bearing fitted to a shaft body having a bearing body formed of an oil-impregnated porous sintered body, an outer ring arranged on the outside and an inner ring on the inside, and the periphery covered with a seal cover. ,
The bearing body has a substantially square cross section and its side surface is sealed with a shielding film.
An inclined wall groove having an inclined surface in which the central portion of the outer ring serves as a valley bottom is carved, and oil flowing in between the bearing body and the outer ring due to centrifugal force generated by the rotation of the bearing body is rotated in the lateral direction. Forming a guiding hydraulic space α,
A wind turbine with blades facing the outer ring side is mounted on the side surface of the bearing body, and a wind pressure that guides the wind generated by the rotation of the wind turbine between the bearing body and the seal cover in the rotational vertical direction. Forming space β,
A fluid bearing characterized in that the oil pressure generated in the hydraulic space α and the wind pressure generated in the wind pressure space β face each other at a contact portion between the bearing body and the outer ring so that the mutual pressures are balanced.
A concave groove is carved in the center of the inner ring to form an oil reservoir space γ between the bearing body and the inner ring to store the oil that flows back due to the negative pressure generated when the rotation of the bearing body is stopped. The fluid bearing according to claim 1.
The fluid bearing according to claim 1 or 2, wherein a holding member is provided on a part of the inner ring, and a seal ring is arranged between the inner ring and the holding member.