JPH0642094Y2 - Fluid bearing - Google PatentsFluid bearing
- Publication number
- JPH0642094Y2 JPH0642094Y2 JP1987036741U JP3674187U JPH0642094Y2 JP H0642094 Y2 JPH0642094 Y2 JP H0642094Y2 JP 1987036741 U JP1987036741 U JP 1987036741U JP 3674187 U JP3674187 U JP 3674187U JP H0642094 Y2 JPH0642094 Y2 JP H0642094Y2
- Prior art keywords
- shaft body
- peripheral surface
- permanent magnet
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- 230000002093 peripheral Effects 0.000 claims description 27
- 239000011148 porous materials Substances 0.000 claims description 14
- 230000000694 effects Effects 0.000 description 7
- 239000002184 metal Substances 0.000 description 3
- 239000000463 materials Substances 0.000 description 2
- 239000007769 metal materials Substances 0.000 description 1
- 239000002923 metal particles Substances 0.000 description 1
DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a hydrodynamic bearing which is frequently used in a polygon mirror scanner or the like in a laser beam printer or the like.
<Prior Art> In the dynamic pressure type hydrodynamic bearing using the sleeve and the shaft, which side is to be the rotating side is arbitrary, but the conventional configuration will be described with reference to FIG. 4, taking the sleeve as the rotating side as an example. .
In the figure, reference numeral 1 denotes a sleeve which is rotated at a high speed and has a radial inner peripheral surface 2. Reference numeral 3 denotes a thrust bearing member having a thrust bottom surface 4, which is fixed to one end of the sleeve 1 and has a flow hole 5 for gas flow provided in the center thereof. Reference numeral 6 denotes a shaft body for axially supporting the sleeve 1, which is appropriately supported by fixing means 7, and cooperates with the radial outer peripheral surface 8 cooperating with the radial inner peripheral surface 2 and the thrust bottom surface 4. The radial outer peripheral surface 8 is provided with a thrust end surface 9 which forms a dynamic pressure generating groove 10. Reference numeral 11 is a magnet fixed to the outer periphery of the sleeve 1, and faces a plurality of sets of driving coils 13 and yokes 14 attached to an appropriate fixing means 12. Reference numeral 15 is an inlet for gas inflow provided on the lower end side of the sleeve 1 in the drawing, and 16 is a pocket (pressure chamber) of a minute volume formed between the thrust bottom surface 4 and the thrust end surface 9. is there.
In the above configuration, when the sleeve 1 is stationary, that is, when the sleeve 1 is not rotating, the thrust bottom surface 4 and the thrust end surface 9 are in contact with each other. Then, from this state, the coil 13
When the sleeve 1 is selectively energized and the sleeve 1 is rotated, the gas flowing from the inflow port 15 by the action of the groove 10 is, as is known, a small amount of about several μm between the radial inner peripheral surface 2 and the radial outer peripheral surface 8. It is guided up through the gap and pumped up.
Raise about m. When the sleeve 1 floats, the pressurized pocket 16 communicates with the outside through the flow hole 5, and the gas in the pocket 16 can flow out from the flow hole 5, so that the pressure in the pocket 16 is always The self-weight of the rotating system including the sleeve 1 and the magnetic attraction force applied to the rotating system and the external atmospheric pressure applied thereto are self-adjusted so as to maintain a balance, and as is well known, the sleeve 1 continues to rotate at high speed in a floating state. become.
FIG. 5 shows another conventional configuration. In FIG. 5, the same components as those in FIG. 4 described above are designated by the same reference numerals. As is apparent from the drawing, this conventional configuration has no thrust bearing surface, and the sleeve 1 on the rotating side is levitated and held by a magnetic attraction force even when stationary. When the sleeve 1 is rotated from this state, gas is introduced from the upper and lower inflow ports 15 by the action of the groove 10 as described above, and the air thin film between the radial inner peripheral surface 2 and the radial outer peripheral surface 8 is formed. Due to the existence (dynamic pressure radial bearing), the sleeve 1 is kept in a non-contact state with the shaft body 6 and continues to rotate at high speed.
<Problems to be Solved by the Invention> By the way, in the conventional structure shown in FIG. 4, the gas discharged from the flow hole 5 acts to keep the pressure in the pocket 16 in an appropriate state. The pressure adjusting mechanism by the so-called orifice effect by the flow hole 5 is important for adjusting the pressure fluctuation in the pocket 16 and is greatly related to the centering action. Therefore, the flow hole 5 has severe dimensional accuracy and positional accuracy. However, this micro-diameter drilling is considerably difficult. Further, since the vicinity of the circulation port 5 and the thrust end surface 9 are repeatedly brought into contact with each other at every start / stop, the circulation port 5
There is also a problem in that the edge of the hole easily causes frictional damage and deteriorates the reliability accuracy of the bearing. Further, if the thrust bearing member 3 is made of a high-hardness wear-resistant material in order to cope with this frictional damage, the degree of difficulty in processing is further increased.
On the other hand, in the above-mentioned conventional structure shown in FIG. 5, the thrust bearing surface does not exist, so the above-mentioned problem does not occur. Also,
Since the creeping distance of the gas flowing in from the inflow port 15 can be made smaller than that of the configuration shown in FIG. 4, the groove for generating the dynamic pressure is formed.
The design of 10 is relatively easy, and the possibility of characteristic deterioration due to friction loss of flowing gas is relatively low. However, since there is no thrust dynamic pressure bearing effect, the magnetic levitation holding force of the magnet 11 with respect to the sleeve 1 is unbalanced due to the ripple of the current flowing in the coil 13, and the sleeve 1 (rotation system) is There was a problem that it was easy to vibrate vertically.
<Purpose of Invention> Therefore, the technical problem to be solved by the present invention is to eliminate the above-mentioned conventional drawbacks, and the purpose thereof is to repeatedly contact the vicinity of the flow port with the thrust end face at the time of starting and stopping. It is intended to provide a fluid bearing which fundamentally eliminates frictional damage on the edge of the flow port hole, and also solves the problem of minute vibration in the thrust direction of the sleeve during rotation, and further the problem of workability.
<Means for Solving the Problems> In order to achieve the above object, a fluid dynamic bearing of the present invention has a shaft having a sleeve having a radial inner peripheral surface and a radial outer peripheral surface cooperating with the radial inner peripheral surface of the sleeve. Body, a thrust bottom member formed on the thrust bottom surface of the sleeve or on the thrust end surface of the shaft body, partially or entirely made of a porous material through which a fluid can pass, and a drive permanent member fixed to the rotating side. Even when the magnet and the drive coil are wound, the drive permanent magnet faces the drive permanent magnet with a gap and is fixed to the fixed side, and the rotating side is stationary, the sleeve and the shaft body cooperate with the drive permanent magnet in the thrust direction. A yoke for floating and holding the sleeve or the shaft body in a non-contact state.
<Operation> As described above, the sleeve or the shaft body on the rotating side is held by a magnetic holding force so that there is a predetermined gap between the thrust bottom surface member and the thrust end surface even when stationary. If the predetermined gap is made of porous material to allow gentle ventilation to the outside, the porous material acts so that the pressure in the gap between the thrust bottom face and the thrust end face is always constant during high speed rotation of the rotating system, and Assures stable high speed rotation without vertical fluctuation.
In addition, even when stationary, a predetermined gap between the thrust bottom surface and the thrust end surface, for example, the diameter of the shaft body is 16 mm
If they are separated by about 1.0 to 1.5 mm, there is no possibility that the thrust bottom surface and the thrust end surface will come into contact with each other even when the gas in the above-mentioned predetermined gap flows into the minute gap of several μm in the radial and outer peripheral surfaces at the time of startup. Therefore, there is no fear of frictional damage at the time of starting and stopping.
On the other hand, the porous material can be easily formed by, for example, a sintered metal element that can be regarded as an assembly of innumerable capillaries, the particle diameter of the metal particles to be sintered, and the thickness of the element,
The air flow rate can be freely controlled by the area.
<Embodiment> The present invention will be described below with reference to an illustrated embodiment. FIG. 1 is a simplified sectional front view of a fluid dynamic bearing according to a first embodiment of the present invention. In addition, in FIG. 2 and FIGS. 2 and 3 described later, the same components as those in the above-described conventional configuration are denoted by the same reference numerals, and the description thereof will be omitted to avoid duplication.
The groove 10 for generating the dynamic pressure of the shaft body 6 shown in FIG.
It has the same herringbone shape as the conventional example shown in FIG.
It is formed so as to be vertically symmetrical and is formed in a shape that guides gas from both end surface directions of the sleeve 1 to a minute gap of about several μm between the radial inner peripheral surface 2 and the radial outer peripheral surface 8. Reference numeral 17 denotes a thrust bottom member fixed to the upper end surface side of the sleeve 1 in the drawing, which is made of a disk-shaped porous material P in this embodiment.
May be formed only on the central portion or the peripheral portion of the thrust bottom surface member 17.
A material having an appropriate gas flowability is selected as the porous material P, and, for example, porous sintered metal or porous ceramics is used for this. In the embodiment, a so-called bronze sintered body obtained by sintering a raw material obtained by applying an Sn coating to bronze (alloy for bronze casting) powder is used as the porous material P. It is a sintered metal element that can be regarded as an assembly of capillary tubes connected to each other, and has a gentle air permeability. The degree of air permeability can be controlled by the particle size of the raw material, the thickness and area of the porous material P, and its production is extremely easy.
Further, even when the sleeve 1 is stationary, the magnetic attraction between the magnet 11 and the yoke 14 causes the sleeve 1 to float above the shaft body 6 by a predetermined amount.
The positional relationship between the magnet 11 and the yoke 14 in the height direction is precisely set. Due to the floating of the sleeve 1, a gap 18 having a predetermined separation distance d is formed between the thrust bottom surface 4 and the thrust end surface 9 even when stationary. The predetermined separation distance d depends on the size of the fluid bearing used, but the gas in the gap 18 may be the radial inner / outer peripheral surface 2,
It is set to a value sufficient to ensure that the thrust bottom surface 4 and the thrust end surface 9 do not come into contact with each other even if it transiently and suddenly flows into the minute gap between the shafts 8. For example, when the diameter of the shaft body 6 is 16 mm. In addition, the value of d is set to be about 1.0 to 1.5 mm, that is, an order of magnitude larger than a minute gap of about several μm between the radial inner and outer peripheral surfaces by about four digits.
In the above structure, when the coil 1 is selectively energized and the sleeve 1 is rotated, the action of the groove 10 causes gas to flow between the radial inner / outer peripheral surfaces 2 and 8 from the inflow port 15 at the lower end side of the sleeve 1 in the figure. At the upper end side of the sleeve 1 in the drawing, the gas in the gap 18 also flows in between the radial inner and outer peripheral surfaces 2 and 8 to form a dynamic pressure radial bearing by an air thin film between the two and 8. It On the other hand, since the porous material P having an appropriate air permeability is present on the upper end side of the sleeve 1, outside air is exposed to the gap 18 before the thrust portion comes into contact with the pressure drop in the gap 18 described above. Flow into the interior of the porous material P, and a gap is created at a predetermined time after activation by a pressure adjusting mechanism by the orifice effect of the porous material P.
The pressure in 18 becomes constant, and the sleeve 1, that is, the rotary system, continues stable high speed rotation without vertical fluctuation. Therefore, even if there is a slight change in the drive current, the rotary system will not fluctuate vertically, and the thrust bearing surface will not suffer frictional damage during start-up and stop unlike the conventional configuration shown in FIG.
FIG. 2 relates to a second embodiment of the present invention. In this embodiment, one end surface of the sleeve 1 is completely closed by a thrust bottom member 17 'made of a non-permeable metal material, and the shaft 6 is used instead.
The porous material P fixed to the end portion of the shaft body 6 has a suitable air permeability between the hollow portion 19 (which communicates with the outside air side) and the gap 18 formed at the end, and the gap is generated when the sleeve 1 is started and rotated. Gas is allowed to flow from the outside into the inside of the hollow 18 through the hollow portion, and in this case, the same effect as that of the first embodiment can be expected.
FIG. 3 relates to a third embodiment of the present invention. In this embodiment, the sleeve 1 is on the fixed side and the shaft body 6 is on the rotating side, and the shaft body 6 is levitated by a magnetic attraction force even when it is stationary. The gap 18 is formed, and in this case, the same effect as that of the first embodiment can be expected.
The present invention can be variously modified without departing from the spirit of the invention. For example, the groove for generating the dynamic pressure is the sleeve 1.
It may be formed on the radial inner peripheral surface of.
<Effect> As described above, according to the present invention, the advantage is impaired in the dynamic pressure type hydrodynamic bearing in which the fluid is guided from the both end surface directions of the sleeve to the minute gap between the radial outer peripheral surface and the radial inner peripheral surface. In addition, it is possible to provide a product in which there is no vertical fluctuation of the rotating system, a fluid pressure self-adjusting mechanism is provided, and a member having this fluid pressure adjusting effect is easily formed, and its practical value is great.
FIG. 1 is a simplified sectional front view of a hydrodynamic bearing according to a first embodiment of the present invention, FIG. 2 is a partially omitted sectional front view of a second embodiment of the present invention, and FIG. 3 is the present invention. 4 is a partially cutaway front view according to the third embodiment of FIG. 4, FIG. 4 is a cutaway front view of a first conventional example, and FIG. 5 is a cutaway front view of a second conventional example. 1 …… Sleeve 2 …… Radial inner peripheral surface 4 …… Thrust bottom surface 6 …… Shaft body 8 …… Radial outer peripheral surface 9 …… Thrust end surface 10 …… Groove for generating dynamic pressure 11 …… Magnet 13 …… Coil 14 …… Yoke 15 …… Inflow port 17, 17 ′ …… Thrust bottom member 18 …… Gap P …… Porous material
Priority Applications (1)
|Application Number||Priority Date||Filing Date||Title|
|JP1987036741U JPH0642094Y2 (en)||1987-03-13||1987-03-13||Fluid bearing|
Applications Claiming Priority (2)
|Application Number||Priority Date||Filing Date||Title|
|JP1987036741U JPH0642094Y2 (en)||1987-03-13||1987-03-13||Fluid bearing|
|US07/160,774 US4820950A (en)||1987-03-03||1988-02-26||Fluid Bearing|
|Publication Number||Publication Date|
|JPS63145016U JPS63145016U (en)||1988-09-26|
|JPH0642094Y2 true JPH0642094Y2 (en)||1994-11-02|
Family Applications (1)
|Application Number||Title||Priority Date||Filing Date|
|JP1987036741U Active JPH0642094Y2 (en)||1987-03-13||1987-03-13||Fluid bearing|
Country Status (1)
|JP (1)||JPH0642094Y2 (en)|
Families Citing this family (1)
|Publication number||Priority date||Publication date||Assignee||Title|
|JP2521074Y2 (en) *||1989-06-27||1996-12-25||光洋精工株式会社||Dynamic bearing device|
Family Cites Families (2)
|Publication number||Priority date||Publication date||Assignee||Title|
|JPH0421844B2 (en) *||1982-06-24||1992-04-14||Tokyo Shibaura Electric Co|
|JPS61211517A (en) *||1985-03-15||1986-09-19||Canon Inc||Dynamic pressure hydraulic bearing device|
- 1987-03-13 JP JP1987036741U patent/JPH0642094Y2/en active Active
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