JPH04119219A - Dynamic bearing - Google Patents

Abstract

PURPOSE:To enable control of load allowable capacity by providing a magnetic fluid between both opposite faces of a pair of members capable of turning relatively freely, and providing a magnetic field forming means controlling the viscousity of magnetic fluid through formation of magnetic field between both the opposite faces. CONSTITUTION:Magnetic fluid L is filled in a crearance between a radial bearing member 21 and a sleeve-shaped opposite member 24 fitted on a rotary shaft in an integrated manner, and the fluid L is retained without falling out of the clearance with its surface tention. When a rotary shaft 22 tends to rotate in a specified direction, the magnetic fluid L generates dynamic pressure due to action of dynamic groove 25 to rotate the shaft 22 in a non-contact manner with a radial bearing member 21 and control the movement in the radial direction. On the circumferential face of the radial bearing member 21 a plurality of magnetic coil 26 are arranged and through the conductive condition of solenoid coil 26 magnetic field is formed between the coil 26 and the iron core 23 built in the rotary shaft 22. With this arrangement, the viscousity of magnetic fluid L is changed to enable control the load allowable quantity as bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dynamic pressure bearing that supports the load of a rotating body by utilizing the dynamic pressure effect of a fluid.

[Prior Art] In general, a dynamic pressure bearing consists of a rotating body and a body that rotatably supports the rotating body, and a dynamic pressure groove is formed on one of the opposing surfaces of the bearing. . When the rotating body is rotated, dynamic pressure is generated in the working fluid interposed between the rotating body and the bearing based on the action of the dynamic pressure groove.
The pressure film of the working fluid supports the rotor and the bearing without contacting the body.

[Problems to be Solved by the Invention] In general, in dynamic pressure bearings, depending on the size and magnitude of the load to be supported, while considering the characteristics of the working fluid used,
The body dimensions of the rotating body and the bearing are determined. Therefore, the viscosity of the working fluid has a significant influence on the performance of the bearing, especially the load carrying capacity.

However, the viscosity of the working fluid is affected by temperature. Therefore, when a liquid lubricant is used as the working fluid, the load capacity fluctuates due to heat generation due to the viscous resistance of the fluid and the influence of outside temperature during high-speed rotation, and the hydrodynamic bearing does not perform as designed. The problem was that I couldn't do it.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide dynamic pressure that allows the load capacity to be adjusted by making it possible to adjust the viscosity of the working fluid interposed between a pair of relatively rotatable members. Our goal is to provide bearings.

[Means and operations for solving the problems] In order to solve the above problems, the present invention provides a dynamic pressure bearing in which a dynamic pressure groove is formed on either one of the opposing surfaces of a pair of relatively rotatable members. A magnetic fluid is interposed between the opposing surfaces, and a magnetic field forming means is provided for forming a magnetic field between the opposing surfaces to control the viscosity of the magnetic fluid.

According to the structure of this bearing, since a magnetic fluid is interposed as a working fluid between each opposing surface of a pair of members, when these pair of members are rotated relative to each other, based on the action of the dynamic pressure groove, Dynamic pressure is generated in the magnetic fluid, and one member is supported without contacting the other member.

Here, when a magnetic field is formed between both opposing surfaces of the pair of members by the magnetic field forming means, the magnetic fluid is influenced by the magnetic field, and the viscosity of the magnetic fluid is controlled according to the magnitude of the magnetic field. . Therefore, even if the temperature of the magnetic fluid increases due to the viscous resistance of the fluid and the viscosity decreases as the two members rotate relative to each other, the viscosity of the magnetic fluid can be reduced by adjusting the magnitude of the magnetic field. By increasing the relative value, the viscosity of the magnetic fluid can be kept constant regardless of temperature changes, and the load capacity of the bearing can be kept constant.

Preferably, the magnetic field forming means is composed of a combination of a magnetic material and an electromagnetic coil.

According to this configuration, the magnitude of the magnetic field is adjusted depending on the amount of current applied to the electromagnetic coil. Furthermore, by combining it with a magnetic material, a larger magnetic field can be created.

Examples of the magnetic fluid include those obtained by dispersing magnetic particles (particle size: 50 to 150) such as iron nitride and iron oxide in a dispersion medium such as hydrocarbon, kerosene, fluorine oil, and water.

[Example] An example in which the present invention is embodied in a thrust bearing will be described below with reference to the drawings.

As shown in FIG. 1, a sphere support member 2 is provided at the lower end of the thrust bearing l, and above the sphere support member 3, a lower opposing member 3 formed in the shape of a disk from 13% chromium stainless steel supports a sphere 4. It is provided through. An engagement recess (path shown) is provided on the lower surface of the periphery of the lower facing member 3, and the tip of a pin 5 protruding from the upper surface of the periphery of the spherical body support member 2 engages in the engagement recess. Accordingly, the lower facing member 4
Free rotation of is restricted.

A shaft support member 6 is disposed at the upper end of the thrust bearing 1, and a rotating shaft 7 is rotatably mounted on the shaft support member 6. An upper opposing member 8 formed into a disk shape and made of 13% chromium-based stainless steel is fixed to the lower end of the rotating shaft 7 with bolts 9. The lower surface of this upper opposing member 8 is arranged to face the upper surface of the lower opposing member 3 in parallel.

A ceramic plate 10 formed into a disk shape and made of sintered silicon carbide material is interposed between the upper and lower opposing members 3 and 8. As shown in FIGS. 1 and 2, a through hole 11 is provided in the center of this ceramic plate 10. Further, the ceramic plate IO is provided with a land 12 continuous to the inner peripheral edge of the through hole 11 over a predetermined width. Further, on each of the upper and lower surfaces of the ceramic plate 10, a plurality of spiral dynamic pressure grooves 13 and 14 (black colored portions in FIG. 2) are formed in a region extending from the outer peripheral edge of the land 12 to the outer peripheral edge of the ceramic plate 10. ing.

Note that, when the upper opposing member 8 is rotated in a specific direction (positive direction) together with the rotating shaft 7, the dynamic pressure grooves 13 formed on the upper surface of the ceramic plate 10 have the following effects: The direction of the spiral is determined so that dynamic pressure is generated in the working fluid interposed between the ceramic plate 10 and the upper opposing member 8. On the other hand, ceramic plate 1
The dynamic pressure grooves 14 formed on the lower surface of the ceramic plate 1
0 is rotated in the opposite direction (reverse direction) to the specific direction, the working fluid interposed between the ceramic plate 10 and the lower facing member 3 is moved based on the action of the dynamic pressure groove 14. The direction of the spiral is determined so that pressure is generated.

As shown in FIG. 1, a retaining pin 15 is protruded from the center of the lower facing member 3, and its tip is connected to the ceramic plate I
It is inserted into the through hole 11 of O. Due to the engagement between the retaining pin 15 and the through hole 11, the ceramic plate 10 is restricted from moving in the radial direction, and is constantly rotated around the retaining pin 15.

Further, each clearance between the lower facing member 3 and the ceramic plate IO and between the upper facing member 8 and the ceramic plate IO is filled with a magnetic fluid made by dispersing iron nitride fine particles in hydrocarbon. ing. Incidentally, such a magnetic fluid has a characteristic that it is magnetized under the influence of an external magnetic field, and as the magnetization increases, the viscosity also increases.

Furthermore, a plurality of electromagnetic coils 16 are attached to the lower surface side of the lower opposing member 3, and a plurality of magnets 17 corresponding to the respective electromagnetic coils 16 are fitted to the upper surface side of the upper opposing member 8. has been done. In addition, each electromagnetic coil 1
6 and the magnet 17 constitute a magnetic field forming means.

Now, in the thrust bearing configured as described above, when a downward load (thrust load) is applied to the rotating shaft 7, there are The members 3, 8 and 10 are attracted to each other with a magnetic fluid interposed between them.

Here, when the rotating shaft 7 is rotated in the forward direction, the magnetic fluid between the upper opposing member 8 and the ceramic plate 10 is moved as the upper opposing member 8 rotates based on its viscosity.

At this time, the magnetic fluid is guided by the dynamic pressure grooves 13 on the top surface of the ceramic plate 10 and gradually guided to the center of the plate 10, so that the upper opposing member 8 and the ceramic plate IO are separated from each other at the center of the plate 10. Dynamic pressure is generated. This dynamic pressure supports the thrust load of the rotating shaft 7,
The rotating shaft 7 and the upper opposing member 8 are rotated without contacting the ceramic plate IO. Furthermore, at this time, the ceramic plate I
No dynamic pressure is generated between O and the lower opposing member 3, and the ceramic plate 10 is attracted to the lower opposing member 3.

On the other hand, when the rotating shaft 7 is rotated in the opposite direction, unlike the above case, no dynamic pressure is generated between the upper opposing member 8 and the ceramic plate lO, and the ceramic plate lO is 8 and rotated in the same direction. Then, the magnetic fluid between the lower facing member 3 and the ceramic plate 10 is guided by the dynamic pressure grooves 14 on the lower surface of the ceramic plate 10 and gradually guided to the center of the plate 10, so that the magnetic fluid flow is generated at the center of the plate 10. Dynamic pressure is generated that tends to separate the lower facing member 3 and the ceramic plate IO. The thrust load of the rotating shaft 7 is supported by this dynamic pressure, and the rotating shaft 7, the upper opposing member 8, and the ceramic and sock plate 10 are rotated without contacting the lower opposing member 3. At this time, the lower facing member 3
and the ceramic plate 10 are separated from each other, but the retaining pin 15
Due to the engagement between the ceramic plate 10 and the through hole 11, the ceramic plate 1O does not become eccentric with respect to the rotation axis of the upper and lower opposing members 3 and 8.

By the way, as the rotating shaft 7 rotates for a long period of time, the temperature of the magnetic fluid increases due to the viscous resistance between each member 3, 8, 10 and the magnetic fluid, causing a decrease in the absolute value of the viscosity. Sometimes. In such a case, each electromagnetic coil 16
By starting the energization control and forming a magnetic field between each magnet 17, the magnetic fluid is magnetized according to the magnitude of the magnetic field, and the viscosity of the magnetic fluid is increased. Therefore, regardless of the temperature rise of the magnetic fluid, each member 3,
The viscosity of the magnetic fluid between 8 and 10 is maintained constant, and stable dynamic pressure is always generated.

In this way, this embodiment uses a magnetic fluid as the working fluid, and by making it possible to form a magnetic field between the upper and lower opposed members 3 and 8 by the electromagnetic coil 16 and the magnet 17, the temperature of the magnetic fluid can be controlled. Despite the decrease in viscosity associated with increase, the absolute viscosity of the magnetic fluid can be increased to maintain a constant viscosity during operation. Therefore, stable performance as a bearing can be exhibited. Further, by appropriately adjusting the magnitude of the magnetic field described above and changing the viscosity of the magnetic fluid, the load capacity of the bearing can be freely changed within a certain range.

Furthermore, even when the rotating shaft 7 rotates in either the forward or reverse direction, the thrust load can be supported by dynamic pressure. Therefore, when this thrust bearing 1 is applied to, for example, a motor, even if the rotating shaft 7 is accidentally rotated in a direction different from the original rotation direction due to a wiring error, the thrust load can be reduced by dynamic pressure. Because the components that make up the bearing come into frictional contact under excessive load,
There is no risk of burning and damage.

In this embodiment, the magnet 17 may be omitted and the magnetic field forming means may be configured only by the electromagnetic coil 16.

[Example 2] An example in which the present invention is embodied in a radial bearing will be described.

As shown in FIG. 3, a rotating shaft 22 is rotatably inserted into a member 21 of the sleeve-shaped radial bearing on the fixed side. The rotating shaft 22 has a built-in iron core 23 that extends along its central axis, and the radial bearing is disposed on the outer circumference of the rotating shaft 22 and faces the inner circumferential surface of the member 21 at a predetermined distance. A sleeve-shaped opposing member 24 is attached so as to be rotatable therewith.

A herringbone-shaped dynamic pressure groove 25 is formed on the outer circumferential surface of this facing member 24 . Further, in the radial bearing, the clearance between the member 21 and the opposing member 24 is filled with the same magnetic fluid as in the first embodiment, and the magnetic fluid is held by its surface tension without flowing down from the clearance. ing. Then, when the rotating shaft 22 is rotated in a specific direction, the magnetic fluid generates dynamic pressure based on the action of the dynamic pressure groove 25, and the rotating shaft 22 is rotated by the radial bearing without contacting the member 21. While being rotated, movement of the rotating shaft 22 in the radial direction is restricted.

Furthermore, in the radial bearing, a plurality of electromagnetic coils 26 are arranged on the outer circumferential surface of the member 21, and when each electromagnetic coil 26 is energized, a magnetic field is created between the iron core 23 and each electromagnetic coil 26. It is formed.

Thereby, the load capacity of the bearing can be adjusted by changing the viscosity of the magnetic fluid.

[Example 3] An example in which the present invention is embodied in a bearing that supports both radial and thrust directions will be described.

As shown in FIG. 4, an iron rotating shaft 32 is rotatably inserted into a member 31 of the ring-shaped bearing on the fixed side. The bearing is attached to the member 3 on the outer periphery of the rotating shaft 32.
A sleeve-shaped radial opposing member 33 is mounted so as to be integrally rotatable with respect to the inner circumferential surface of the member 1 at an interval of 5 to 50 μm.

Furthermore, the radial opposing member 33 is
At upper and lower adjacent positions of the bearing, a pair of thrust opposing members 34 formed in the shape of discs facing each other with an interval of 5 to 50 μm are mounted on the upper and lower surfaces of the member 31 so as to be integrally rotatable. ing.

A herringbone-shaped dynamic pressure groove 35 is formed on the outer peripheral surface of the radial opposing member 33, and a spiral dynamic pressure groove 36 is formed on each opposing surface of both thrust opposing members 34. There is.

Further, in the bearing, the clearance between the member 31 and the radial opposing member 33 and thrust opposing member 34 is filled with the same magnetic fluid as in the first embodiment, and the magnetic fluid is held by its surface tension. ing. When the rotating shaft 32 is rotated in a specific direction, the magnetic fluid generates dynamic pressure based on the action of the dynamic pressure grooves 35 and 36, and the rotating shaft 32 and the radial and thrust opposing members 33, 34 However, the bearing rotates without contacting the member 31, and movement of the rotating shaft 32 in the radial direction and the thrust direction is restricted.

Further, a plurality of electromagnetic coils 37 are arranged on the outer circumference of the bearing member 31. Then, by energizing each electromagnetic coil 37, the iron rotating shaft 32 and each electromagnetic coil 3
A magnetic field is formed between 7 and 7.

Thereby, the load capacity of the bearing can be adjusted by changing the viscosity of the magnetic fluid L'.

[Effects of the Invention] As detailed above, according to the present invention, by making it possible to adjust the viscosity of the working fluid interposed between a pair of relatively rotatable members, the dynamic pressure that allows the load capacity to be adjusted is adjusted. This has the excellent effect of eliminating the need to provide bearings.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing Example 1 embodying the present invention, FIG. 2 is a plan view of the same ceramic plate, FIG. 3 is a sectional view showing Example 2, and FIG. 4 is Example 3. FIG. 3.8... Lower and upper opposing members, 10... Ceramic plate (3, 10.8, and IO each constitute a pair of members), 13. 1.4. 25. 35.
36... Dynamic pressure groove, 16, 26, 37... Electromagnetic coil, 17, 23. 32... Magnet as magnetic material, iron core, rotating shaft, 21... Radial bearing is member, 24
... Opposing member (21 and 24 constitute a pair of members), 31... Bearing is a member, 33 Radial opposing member, 34... Thrust opposing member (31 and 33. 31 and 3
4 respectively constitute a pair of members), L...
magnetic fluid. Patent applicant: IBIDEN Co., Ltd. Agent: Patent attorney: Hironobu Onda (and one other person) Figure 2

Claims (1)

[Scope of Claims] 1. A dynamic pressure bearing in which a dynamic pressure groove (13, 14, etc.) is formed on one of the opposing surfaces of a pair of relatively rotatable members (3, 8, 10, etc.), , a magnetic fluid (L) is interposed between the two opposing surfaces, and a magnetic field forming means (16) for controlling the viscosity of the magnetic fluid by forming a magnetic field between the two opposing surfaces.
, 17, etc.). 2. The hydrodynamic bearing according to claim 1, wherein the magnetic field forming means comprises a combination of a magnetic material (17, etc.) and an electromagnetic coil (16, etc.).