JP3877435B2 - Bearing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bearing device, and more particularly to a bearing device using a radial dynamic pressure air bearing and an axial magnetic bearing.
[0002]
[Prior art]
An electrophotographic recording apparatus using a laser writing system such as a digital copying machine or a laser printer has features such as good printing quality, high printing speed and low noise, and a low price. Recently, it has been spreading rapidly.
[0003]
The polygon scanner used in the laser writing system of this electrophotographic recording apparatus is required to rotate the polygon mirror at a rotation speed corresponding to the printing speed and pixel density of the recording apparatus. As the printing speed increases and the pixel density increases, the polygon scanner is required to rotate at an ultra-high speed of 20000 rpm or more.
[0004]
For such polygon scanners that require ultra-high speed rotation, conventional ball bearing type bearing devices cannot satisfy the image quality required in terms of bearing life and bearing noise.
[0005]
Therefore, conventionally, a dynamic pressure air bearing using dynamic pressure air has been used for polygon scanners that require ultra-high speed rotation.
[0006]
As an apparatus using such a dynamic pressure air bearing, for example, an optical deflection apparatus described in JP-A-8-5951 has been proposed. In this optical deflecting device, a rotating sleeve and a cylindrical fixed shaft constituting a dynamic pressure bearing are formed of a ceramic material, a permanent magnet constituting a repulsive magnetic bearing is disposed inside an upper end of the rotating sleeve, and a tip of the fixed shaft A second permanent magnet for repulsion is disposed at a predetermined gap in the axial direction.
[0007]
Conventionally, a hydrodynamic bearing device described in JP-A-7-279966 has been proposed. In this hydrodynamic bearing device, a hydrodynamic bearing is constituted by an outer periphery of a rotary sleeve and an inner periphery of a fixed shaft, one of the bearings is coated with polyamideimide, and the other is anodized or nickel-plated. Further, a permanent magnet constituting a magnetic bearing is disposed at the upper end of the rotating sleeve outside the dynamic pressure bearing.
[0008]
[Problems to be solved by the invention]
However, in such a conventional bearing device, there is still room for improvement as a high-speed rotation bearing such as a polygon scanner.
[0009]
That is, the optical deflection apparatus described in Japanese Patent Laid-Open No. 8-5951 has a configuration in which a permanent magnet for a magnetic bearing is disposed on the upper part of the rotating body, so that the entire apparatus becomes longer and larger. there were. In addition, there has been a problem that magnetic particles generated by wear from the permanent magnets disposed on the upper part of the rotating body fall off and enter the bearing gap, and the bearing does not rotate normally.
[0010]
Further, in the hydrodynamic bearing device described in JP-A-7-279966, the permanent magnet constituting the magnetic bearing is disposed at the upper end of the rotating sleeve outside the hydrodynamic bearing. However, there was a problem that the size and lengthened. In addition, the shape of the rotating sleeve is complicated, and the material of the rotating sleeve is limited to a metal with good workability, such as an aluminum alloy, and there is a problem that the degree of freedom in design is limited. Furthermore, in order to prevent bearing locks that occur when used in hydrodynamic bearings with metal surfaces, the bearings are coated with polyamide-imide, anodized or nickel-plated. And the workability is poor, the productivity of the bearing device is poor, and the bearing device is expensive.
[0011]
  Accordingly, the invention according to claim 1 is a fixed shaft fixed to a predetermined housing, a hollow rotary shaft having a hollow portion into which the fixed shaft is inserted in the axial direction, and a seating surface.Is formedIt has a collar part and is attached in a state where a hollow part is closed and a predetermined air pocket is formed on the distal end side opposite to the housing of the hollow rotating shaft.Cap shapeA holding member, a polygon mirror mounted on the seat surface and fixed to the rotating body, and the dynamic pressure of the air generated when the rotating body is rotated by a motor, the inner peripheral surface of the hollow rotating shaft and the outer peripheral surface of the fixed shaft A bearing device that rotatably supports a rotating body in a radial direction and an axial direction by a radial dynamic pressure air bearing received by a dynamic pressure air bearing surface comprising an axial bearing using a magnetic force, and having a fixed shaft and a hollow The rotating shaft is formed in a cylindrical shape having a uniform thickness by a ceramic material.Positioned and fixed in the axial direction on a housing with a bottom in the centerBy storing in the fixed shaft, the fixed shaft and the hollow rotary shaft are machined at low cost and with high accuracy using ceramic with good wear resistance, and the axial bearing is stored in the fixed shaft for reliability. It is an object of the present invention to provide a small and inexpensive bearing device capable of improving the performance.
[0012]
According to a second aspect of the present invention, there is provided an axial bearing comprising: a ring-shaped suction type magnetic bearing fixing portion fixed inside a fixed shaft; and a ring-type suction type magnetic bearing fixing portion fixed to a holding member. By including the bearing fixing portion and the attraction type magnetic bearing rotating portion inserted in a state in which a predetermined magnetic gap is formed in the radial direction, the axial bearing is appropriately accommodated inside the fixed shaft, and more The object is to provide a bearing device that is smaller and less expensive.
[0013]
  The invention described in claim 3A fixed shaft fixed to a predetermined housing, a hollow rotary shaft having a hollow portion into which the fixed shaft is inserted in the axial direction, and a hollow portion is closed on a distal end side opposite to the housing of the hollow rotary shaft, A holding member attached in a state of forming a pool, and a polygon mirror fixed to the rotating body,The housing has a bottom with a predetermined shape to which the fixed shaft is fixed at a substantially central portion thereof, and the axial bearing is housed inside the cylindrical fixed shaft and is fixed upright on the bottomed portion. Positioning of the axial bearing is simple and appropriate by positioning in the axial direction with a predetermined spacer housed inside and communicating with the outside through a minute hole of a predetermined size formed in the holding member. An object of the present invention is to provide a small and inexpensive bearing device capable of providing an appropriate damping characteristic to an axial bearing and further improving the reliability.
[0014]
According to a fourth aspect of the present invention, there is provided an axial bearing having a ring-shaped suction type magnetic bearing fixing portion fixed inside the fixed shaft, and a ring-type suction type magnetic bearing fixing portion fixed to the holding member. And a suction-type magnetic bearing rotating portion inserted in a state in which a predetermined magnetic gap is formed in a radial direction, and the suction-type magnetic bearing fixing portion is positioned at the upper end of the spacer. Axial bearings are inserted into the fixed shaft in this state, and the upper end of the suction type magnetic bearing fixed portion is held by a predetermined fixing bush press-fitted into the fixed shaft, and held and fixed inside the fixed shaft. A small and even cheaper bearing device that can reliably and easily perform positioning in the axial direction of the shaft without using a special jig or perform a special process and further improve the reliability. It is an object of Rukoto.
[0015]
  The invention according to claim 5Meets the demand for ultra-high-speed rotation of polygon scanners by using bearing devicesThe purpose is that.
[0016]
[Means for Solving the Problems]
  The bearing device according to claim 1, a fixed shaft fixed to a predetermined housing, a hollow rotary shaft having a hollow portion into which the fixed shaft is inserted in the axial direction, and a seating surfaceIs formedIt has a collar part, and is attached in a state in which the hollow part is closed and a predetermined air pocket is formed on the distal end side opposite to the housing of the hollow rotating shaft.Cap shapeA holding member, a polygon mirror placed on the seat surface and fixed to the rotating body, and a dynamic pressure of air generated when the rotating body is rotated by a motor to the inner peripheral surface of the hollow rotating shaft and the fixed A bearing device that rotatably supports the rotating body in a radial direction and an axial direction by a radial dynamic pressure air bearing received by a dynamic pressure air bearing surface formed by an outer peripheral surface of a shaft and an axial bearing using magnetic force. The fixed shaft and the hollow rotary shaft are formed in a cylindrical shape having a uniform thickness from a ceramic material, and the axial bearing isPositioned and fixed in the axial direction to the housing having a bottomed portion at the centerIt is housed in the fixed shaft.
[0017]
  According to the above configuration, the fixed shaft fixed to the predetermined housing, the hollow rotation shaft having the hollow portion into which the fixed shaft is inserted in the axial direction, and the seat surfaceIs formedIt has a collar part and is attached in a state where a hollow part is closed and a predetermined air pocket is formed on the distal end side opposite to the housing of the hollow rotating shaft.Cap shapeA holding member, a polygon mirror mounted on the seat surface and fixed to the rotating body, and the dynamic pressure of the air generated when the rotating body is rotated by a motor, the inner peripheral surface of the hollow rotating shaft and the outer peripheral surface of the fixed shaft A bearing device that rotatably supports a rotating body in a radial direction and an axial direction by a radial dynamic pressure air bearing received by a dynamic pressure air bearing surface comprising an axial bearing using a magnetic force, and having a fixed shaft and a hollow The rotating shaft is formed in a cylindrical shape having a uniform thickness by a ceramic material.Positioned and fixed in the axial direction on a housing with a bottom in the centerSince it is housed inside the fixed shaft, the fixed shaft and hollow rotating shaft can be machined at low cost and with high precision using ceramic with good wear resistance, and the axial bearing is housed in the fixed shaft. Thus, the reliability can be improved, and the bearing device can be made small and inexpensive.
[0018]
In this case, for example, as described in claim 2, the axial bearing includes a ring-shaped suction type magnetic bearing fixing portion fixed inside the fixed shaft, and a ring-shaped suction member fixed to the holding member. The suction type magnetic bearing fixing part and the suction type magnetic bearing rotating part inserted in a state in which a predetermined magnetic gap is formed in the radial direction may be provided in the type magnetic bearing fixing part.
[0019]
According to the above configuration, the axial bearing is fixed to the ring-shaped suction type magnetic bearing fixing portion fixed inside the fixed shaft, and the suction-type magnetic bearing fixing portion is fixed to the holding member in the ring-shaped suction type magnetic bearing fixing portion. And a suction-type magnetic bearing rotating part inserted in a state in which a predetermined magnetic gap is formed in the radial direction, the axial bearing can be properly accommodated in the fixed shaft, and the bearing The device can be made even smaller and cheaper.
[0020]
  ContractClaim 3 describedThe bearing device ofFixed to a predetermined housingFixed shaft and the fixed shaft is insertedHollow rotary shaft having a hollow portion in the axial directionAnd beforeIn a state where the hollow portion is closed on the tip side opposite to the housing of the hollow rotating shaft to form a predetermined air reservoirIt is attachedHolding memberAnd fixed to the rotating bodyPolygon mirrorA radial dynamic pressure air bearing that receives a dynamic pressure of air generated when the rotating body is rotated by a motor at a dynamic pressure air bearing surface composed of an inner peripheral surface of the hollow rotary shaft and an outer peripheral surface of the fixed shaft; An axial bearing using a magnetic force, and a bearing device that supports the rotating body rotatably in a radial direction and an axial direction, wherein the fixed shaft and the hollow rotating shaft have a uniform thickness made of a ceramic material. Formed into a shape, andThe housing has a bottom portion having a predetermined shape to which the fixed shaft is fixed at a substantially central portion thereof, and the axial bearing is housed in the cylindrical fixed shaft and is erected on the bottom portion. In the state, it is positioned in the axial direction by a predetermined spacer housed inside the fixed shaft, and the air reservoir is communicated to the outside through a minute hole of a predetermined size formed in the holding member.It is characterized by that.
[0021]
According to the above configuration, the housing has a bottom portion with a predetermined shape to which the fixed shaft is fixed at a substantially central portion thereof, and the axial bearing is housed inside the cylindrical fixed shaft, and at the bottom portion. Axial bearings are positioned in the axial direction by a predetermined spacer housed inside the fixed shaft in an upright state, and the air reservoir communicates with the outside through a minute hole of a predetermined size formed in the holding member. Positioning can be performed easily and appropriately, moderate damping characteristics can be imparted to the axial bearing, reliability can be further improved, and the bearing device must be small and inexpensive. Can do.
[0022]
  ContractClaim 4 describedThe bearing device according to claim 3,The axial bearing includes a ring-shaped suction-type magnetic bearing fixing portion fixed inside the fixed shaft, and a suction-type magnetic bearing fixing portion fixed to the holding member and in the ring-shaped suction-type magnetic bearing fixing portion. An attraction-type magnetic bearing rotating portion inserted in a state in which a predetermined magnetic gap is formed in a radial direction, and the attraction-type magnetic bearing fixing portion is located inside the fixed shaft in a state of being positioned at an upper end of the spacer. The upper end of the suction-type magnetic bearing fixing portion is inserted and held by a predetermined fixing bush press-fitted into the fixed shaft, and is held and fixed inside the fixed shaft.It is characterized by that.
[0023]
According to the above configuration, the axial bearing is fixed to the ring-shaped suction type magnetic bearing fixing portion fixed inside the fixed shaft, and the suction-type magnetic bearing fixing portion is fixed to the holding member in the ring-shaped suction type magnetic bearing fixing portion. And a suction-type magnetic bearing rotating part inserted in a state in which a predetermined magnetic gap is formed in a radial direction, and the suction-type magnetic bearing fixing part is positioned at the upper end of the spacer. Inserted into the fixed shaft, the upper end of the suction type magnetic bearing fixed portion is held and fixed inside the fixed shaft by pressing with a predetermined fixing bush press-fitted into the fixed shaft. Axial positioning can be performed reliably and easily without using special jigs or special process treatments, and the reliability can be further improved. It can be made layer inexpensive.
[0024]
  ContractClaim 5 describedThe brushless motor is characterized in that the bearing device according to any one of claims 1 to 4 is used.
[0025]
  According to the above configuration,A brushless motor capable of ultra-high speed rotation of 20000 rpm or more can be realized..AndThere is little vibration even at high temperatures due to temperature rise during high-speed rotation, and the reflection surface accuracy of the polygon mirror can be maintained with high accuracy, further improving the reliability and further improving the image quality. Can be made.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. The embodiments described below are preferred embodiments of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. As long as there is no description which limits, it is not restricted to these aspects.
[0027]
1 and 2 are views showing an embodiment of a bearing device of the present invention. FIG. 1 is a front view of a hydrodynamic air bearing type polygon scanner 1 to which an embodiment of the bearing device of the present invention is applied. It is sectional drawing.
[0028]
In FIG. 1, a dynamic pressure air bearing type polygon scanner 1 has an appearance formed by a housing 2 and an upper cover 3 screwed onto the housing 2, and the housing 2 has a peripheral wall at the bottom center. A bottomed portion 2a having a bottom on a plane that is recessed in a columnar shape by a predetermined amount is formed. A cylindrical fixed shaft 4 is fixed to the bottomed portion 2a of the housing 2 by a method such as press fitting or shrink fitting. When the fixed shaft 4 is fixed to the housing 2, the bottomed portion 2 a is formed in the housing 2, so that the fixed shaft 4 is fixed to the bottomed portion 2 a only by press-fitting or shrink fitting. The reference of the axial position of the fixed shaft 4 can be set at a place other than the bottomed portion 2a, and the fixed shaft can be easily and easily fixed without using a special jig or adjusting the position. 4 can be fixed to the housing 2.
[0029]
The fixed shaft 4 is formed with a herringbone groove 4a at an appropriate position on the peripheral wall portion, and a ring-shaped suction having a predetermined length in the axial direction (axial direction) is inserted into the upper end recess of the fixed shaft 4. A mold magnetic bearing fixing portion 5 is embedded.
[0030]
As shown in FIG. 2, the attraction-type magnetic bearing fixing portion 5 has a ring-like shape in which a center circle of a predetermined size is formed in the center portion, is magnetized in two poles in the axial direction, and the magnetic poles are oriented in the axial direction. The permanent magnet 6 and a pair of first magnets made of a ferromagnetic material fixed at both axial ends (both axial ends) of the permanent magnet 6 and having a center circle smaller than the center circle (inner diameter) of the permanent magnet 6 formed at the center thereof. The first fixed yoke plate 7 and the second fixed yoke plate 8 are formed. The attraction-type magnetic bearing fixing portion 5 is embedded in the upper end recess of the fixed shaft 4 with the permanent magnet 6 sandwiched between the first fixed yoke plate 7 and the second fixed yoke plate 8. As shown in FIG. 1, the permanent magnet 6 is sandwiched between the first fixed yoke plate 7 and the second fixed yoke plate 8 in the axial direction of the fixed shaft 4 as shown in FIG. And, the center circle of the first fixed yoke plate 7 and the center circle of the second fixed yoke plate 8 coincide with (coaxial with) the axis center of the fixed shaft 4 and are embedded in the upper end recess of the fixed shaft 4. ing. The first fixed yoke plate 7 and the second fixed yoke plate 8 are formed of a steel plate material, and the permanent magnet 6 is mainly a rare earth permanent magnet, for example. The suction type magnetic bearing fixing portion 5 is not limited to the fixing bush 9 fixed in the upper end recess of the fixed shaft 4. For example, the suction type magnetic bearing fixing portion 5 is fixed in the upper end recess of the fixed shaft 4 with an adhesive or the like. Also good.
[0031]
As shown in FIG. 1, the fixed shaft 4 is inserted into the hollow of a rotary sleeve (hollow rotary shaft) 10, and is formed in a cap shape from the upper end surface to the outer peripheral surface of the rotary sleeve 10, and A flange (holding member) 11 protruding in a bowl shape in the direction (radial direction) is fixed by shrinkage or press fitting. A bearing gap formed between the outer peripheral surface of the fixed shaft 4 and the inner peripheral surface of the rotary sleeve 10 is maintained at several μm.
[0032]
A suction-type magnetic bearing rotating portion 12 is press-fitted into the center of the flange 11 and fixed to the flange 11. As shown in FIG. 2, the suction-type magnetic bearing rotating portion 12 is fixed to the first fixed yoke plate 7. Outer cylindrical surfaces 12a and 12b constituting a magnetic gap are formed between the central circle portion of the second fixed yoke plate 8 and the central circle portion of the second fixed yoke plate 8. The outer cylindrical surfaces 12a and 12b are arranged so as to be coaxial with the rotation center axis of the attraction type magnetic bearing rotating portion 12.
[0033]
As shown in FIG. 1, a polygon mirror 13 made of an aluminum alloy is placed on the seat surface 11 a protruding in a flange shape of the flange 11. The polygon mirror 13 is fixed to the flange 11 of the rotary sleeve 10 by a leaf spring 14. And the leaf spring 14 is fixed to the attraction type magnetic bearing rotating part 12 by being screwed into a screw hole 12c formed at the upper end of the attraction type magnetic bearing rotating part 12. Thus, the suction type magnetic bearing rotating part 12 is fixed. As described above, the flange 11 is attached to the rotary sleeve 10 in a state where the hollow portion above the rotary sleeve 10 is closed, and the hollow of the rotary sleeve 10 closed by the upper end of the fixed shaft 4 and the flange 11 is provided. An air reservoir 16 is formed in the part.
[0034]
A cylindrical spacer 17 is stored below the fixed magnetic bearing fixing portion 5 of the fixed shaft 4, and the spacer 17 is stored in the fixed shaft 4 while standing upright on the bottomed portion 2a. Yes. The spacer 17 serves to reduce the axial positioning of the suction type magnetic bearing fixing portion 5 and the volume of the air reservoir 16. Therefore, the axial positioning of the attraction type magnetic bearing fixing portion 5 constituting the axial bearing can be reliably and easily performed without using a special jig or performing a special process.
[0035]
The attraction-type magnetic bearing rotating portion 12 is formed of a material with high dimensional accuracy, such as a permanent magnet or a steel-based ferromagnetic material. The fixed shaft 4 and the rotating sleeve 10 are formed in a cylindrical shape from a ceramic material, and the flange 11 fixed to the rotating sleeve 10 is formed from the same aluminum alloy material as the polygon mirror 13. That is, the flange 11 is formed of an aluminum alloy material having a thermal expansion coefficient substantially the same as that of the polygon mirror 13.
[0036]
When the fixed shaft 4 and the rotating sleeve 10 are formed of a ceramic material in this way, the wear resistance is excellent, but cutting and the like cannot be performed, so that processing is difficult. This will reduce the mass productivity and reduce the quality and cost.
[0037]
Therefore, in the present embodiment, both the fixed shaft 4 and the rotary sleeve 10 are formed in a simple cylindrical shape with uniform inner and outer diameters, that is, a thickness, and an axial bearing is configured inside the fixed shaft 4. The suction type magnetic bearing fixing part 5 and the suction type magnetic bearing rotating part 12 are arranged to improve mass productivity while taking advantage of the characteristics of the ceramic material.
[0038]
The leaf spring 14 is formed of a nonmagnetic material such as an aluminum alloy, for example.
[0039]
  FigureAs shown in 1,On the peripheral surface of the attraction type magnetic bearing rotating part 12, there is a plateA fine hole 11b communicating with the outside of the rotating sleeve 10 through a slit (not shown) of the spring 14ShapeThe fine hole 11b has an appropriate damping characteristic for an axial bearing described later, due to the viscous resistance of the air passing through the fine hole 11b.
[0040]
As shown in FIG. 1, a rotor magnet 18 is attached to the lower surface of the flange 11 of the rotating sleeve 10 and in the outer circumferential direction of the rotating sleeve 10. The rotor magnet 18 is, for example, lightweight and mechanical. It is made of an aluminum-manganese metal magnet having high proof stress (tensile strength).
[0041]
The rotating sleeve 10 to which the flange 11, the suction type magnetic bearing rotating unit 12, the polygon mirror 13, the leaf spring 14, the screw 15, the rotor magnet 18 and the like are attached constitutes a rotating body 19.
[0042]
A stator core 20 is disposed on the inner peripheral side facing the rotor magnet 18, and a winding coil 20 a is wound around the stator core 20. The stator core 20 is attached to a support member 21 fixed to the housing 2. A printed circuit board 22 and a hall element 23 are disposed below the stator core 20 around which the rotor magnet 18 and the winding coil 20a are wound. The printed circuit board 22 is attached to the housing 2, and the hall element 23 is attached to the printed circuit board 22. A drive circuit is formed on the printed circuit board 22, and the rotor magnet 18, the printed circuit board 22, the winding coil 20 a, the hall element 23, and the like have a magnetic gap with the rotor magnet 18 in the outer diameter direction of the stator core 20. A radial gap outer rotor type brushless motor 24 is configured. The brushless motor 24 rotates the rotator 19 by controlling the energization to the winding coil 20a sequentially based on the position detection signal of the Hall element 23 by the drive circuit of the printed circuit board 22 and switching the excitation. Control at a constant speed.
[0043]
Further, the rotating body 19 is subjected to balance correction up and down so that vibration does not occur even at high speed rotation. The upper balance correction is a bent portion 14a of the leaf spring 14, and the lower balance correction. Is the outer diameter portion 11 c of the flange 11. The balance of the rotating body 19 is corrected with an accuracy of several mg or less by applying an adhesive to the bent portion 14a of the leaf spring 14 and the outer diameter portion 11c of the flange 11.
[0044]
Since the herringbone groove 4a is formed on the outer peripheral surface of the fixed shaft 4 as described above, when the rotating body 19 is rotated by driving the brushless motor 24, the pressure in the gap between the rotating sleeve 10 and the fixed shaft 4 is increased. A radial bearing (dynamic motion) using dynamic pressure air with the surface where the rotary sleeve 10 and the herringbone groove 4a of the fixed shaft 4 are formed by the rotary sleeve 10, the fixed shaft 4 and the herringbone groove 4a as the dynamic pressure air bearing surface. It functions as a pressure bearing and supports the rotating body 19 in a radial direction (radial direction) without contact.
[0045]
Further, the suction type magnetic bearing rotating portion 12 fixed to the flange 11, the permanent magnet 6 embedded and fixed in the upper end recess of the fixed shaft 4, the first fixed yoke plate 7 and the second fixed yoke plate 8 are attracted. The type magnetic bearing fixing part 5 is an axial bearing (magnetic) in which an attractive force is generated in the attraction type magnetic bearing fixing part 5 embedded and fixed to the attraction type magnetic bearing rotating part 12 and the fixed shaft 4 to float the rotating body 19. The rotating body 19 is supported in a non-contact manner in the axial direction.
[0046]
A glass window 25 is fixed to the upper cover 3 with an opening window 3a for entering / exiting laser light from a semiconductor laser (not shown) with a double-sided tape or an adhesive, and the inside is sealed.
[0047]
Next, the operation of the present embodiment will be described. In the dynamic pressure air bearing type polygon scanner 1, the fixed shaft 4 fixed to the bottomed portion 2 a of the housing 2 is inserted into the rotary sleeve 10, and the suction type magnetic bearing fixed portion 5 is embedded in the upper end recess of the fixed shaft 4. Yes. The attraction type magnetic bearing fixing portion 5 includes a ring-shaped permanent magnet 6 magnetized in two poles in the axial direction, and a pair of ring-shaped first fixed yoke plate 7 and second fixed yoke plate in the vertical direction (axial direction). 8, the center circle of the first fixed yoke plate 7 and the second fixed yoke plate 8 is formed smaller than the center circle of the permanent magnet 6 and coincides with the axis of the rotary sleeve 10. It is arranged in the state to do.
[0048]
In the assembly of the dynamic pressure air bearing type polygon scanner 1, specifically, first, the fixed shaft 4 formed in a cylindrical shape with a uniform thickness is fixed to the bottomed portion 2 a of the housing 2, and the upper side of the fixed shaft 4 is fixed. The spacer 17 is inserted into the fixed shaft 4 and arranged in an upright state on the bottomed portion 2a, and then the second fixed yoke plate 8, the permanent magnet 6 and the first fixed portion constituting the attractive magnetic bearing fixing portion 5. The yoke plate 7 is inserted into the fixed shaft 4, and the fixing bush 9 is press-fitted into the fixed shaft 4 and fixed.
[0049]
Therefore, fixing the fixed shaft 4 to the housing 2 and fixing the spacer 17 to the housing 2 can be achieved by simply pushing the fixed shaft 4 and the spacer 17 to the bottomed portion 2a formed on the housing 2 and fixing them. The positioning of the bearing fixing portion 5 can be performed with high accuracy and ease without using other standards, and without performing any special jig or adjustment, thereby improving workability.
[0050]
The fixed shaft 4 is inserted into the hollow of the rotary sleeve 10. A flange 11 is attached to the rotary sleeve 10, and the polygon mirror 13, the rotor magnet 18, and the suction type magnetic bearing rotate on the flange 11. The rotating body 19 is configured by attaching the part 12 and the like.
[0051]
An attraction type magnetic bearing rotating part 12 that enters the center circle of the attraction type magnetic bearing fixing part 5 embedded in the upper end recess of the fixed shaft 4 is fixed to the flange 11. Is a material having high dimensional accuracy, such as a permanent magnet or a steel-based ferromagnetic material, and is formed in a columnar shape or a cylindrical shape, and the first fixed yoke plate 7 and the second fixed yoke plate 7 of the attraction type magnetic bearing fixing portion 5. The outer cylinder surfaces 12 a and 12 b are formed at positions facing the two fixed yoke plates 8, and a magnetic gap with a fine interval is formed between the first fixed yoke plate 7 and the second fixed yoke plate 8.
[0052]
As described above, the attraction-type magnetic bearing rotating portion 12 is formed of a permanent magnet or a ferromagnetic material, and includes the permanent magnet 6 of the attraction-type magnetic bearing fixing portion 5, the first fixed yoke plate 7, the attraction-type magnetic bearing. A magnetic field line is formed in a closed loop shape toward the rotating portion 12 and the second fixed yoke plate 8 and again toward the permanent magnet 6, and the attractive magnetic bearing fixed portion 5 and the flange embedded in the upper end recess of the fixed shaft 4. 11, an attraction force is generated between the attraction-type magnetic bearing rotating portion 12 fixed to the rotary sleeve 10 via 11, and the attraction-type magnetic bearing rotating portion 12 fixed to the flange 11 and the upper end recess of the fixed shaft 4 The attraction-type magnetic bearing fixing portion 5 embedded in the shaft functions as an axial bearing that floats the rotating body 19 and supports the rotating body 19 in a non-contact manner in the axial direction.
[0053]
In addition, the dynamic pressure air bearing type polygon scanner 1 is provided with a stator core 20 around which a winding coil 20a is wound at a position facing the rotor magnet 18 attached to the flange 11 in the circumferential direction, and the rotor magnet. A hall element 23 and a printed circuit board 22 are disposed at a position below the printed circuit board 18. The printed circuit board 22, the stator core 20 around which the winding coil 20a is wound, the hall element 23, and the like are a radial gap, outer rotor type brushless. The rotating body 19 is rotated by configuring the motor 24 and controlling the energization to the winding coil 20a by the drive circuit of the printed circuit board 22 and switching the excitation.
[0054]
A herringbone groove 4 a is formed on the outer peripheral surface of the fixed shaft 4. When the rotating body 19 is rotated by driving the brushless motor 24, the pressure in the gap between the rotating sleeve 10 and the fixed shaft 4 increases, and the rotating sleeve 10. The fixed shaft 4 and the herringbone groove 4a function as a radial bearing using dynamic pressure air, and support the rotating body 19 in the radial direction without contact.
[0055]
As described above, the dynamic pressure air bearing type polygon scanner 1 uses the dynamic pressure air by the axial bearing supporting the rotating body 19 in a non-contact manner in the axial direction and rotating the rotating body 19 by the brushless motor 24. The radial bearing supports the rotating body 19 in the radial direction without contact.
[0056]
The dynamic pressure air bearing type polygon scanner 1 is formed in a cylindrical shape with a uniform wall thickness which is a simple shape by the fixed shaft 4 and the rotating sleeve 10 ceramic material, so that mass production is performed while taking advantage of the characteristics of the ceramic material. It is possible to produce a dynamic pressure air bearing type polygon scanner 1 with good performance.
[0057]
Further, since the polygon mirror 13 attached to the rotary sleeve 10 is formed of an aluminum alloy, a difference in thermal expansion coefficient between the rotary sleeve 10 and the polygon mirror 13 becomes a problem. That is, aluminum has a thermal expansion coefficient of 2.3 × 10 −5 / ° C., and ceramic [alumina] has a thermal expansion coefficient of 0.7 × 10 −5 / ° C.
[0058]
When the polygon mirror 13 made of an aluminum alloy is directly bonded and fixed to the rotary sleeve 10 formed of the ceramic material as described above, there is a fitting gap between the parts, and the temperature rise (100) during high-speed rotation. As a result, a slight positional shift occurs, and the rotational balance of the rotating body 19 is lost, resulting in an increase in vibration of the polygon mirror 13. In this case, if the polygon mirror 13 is shrink-fitted or press-fitted and fixed to the rotary sleeve 10, the accuracy of the reflective surface of the polygon mirror 13 processed with high accuracy is deteriorated, causing problems such as image distortion.
[0059]
However, in the dynamic pressure air bearing type polygon scanner 1 of the present embodiment, an aluminum alloy polygon mirror 13 is attached to a rotary sleeve 10 made of a ceramic material via a flange 11. That is, the dynamic pressure air bearing type polygon scanner 1 is formed in a cap shape from the upper end surface of the rotary sleeve 10 to the outer peripheral surface, and the flange 11 protruding outwardly (in the radial direction) in a bowl shape is shrink-fitted or press-fitted. The polygon mirror 13 is mounted on the seat surface 11a protruding in a bowl shape of the flange 11 and is pressed against the seat surface 11a of the flange 11 of the rotary sleeve 10 by the leaf spring 14 and fixed. Yes.
[0060]
Therefore, vibration can be suppressed even in a high temperature state during high-speed rotation, and image quality can be improved by preventing image distortion.
[0061]
As described above, in the dynamic pressure air bearing type polygon scanner 1 according to the present embodiment, the fixed shaft 4 is fixed to the housing 2, and the rotating body 19 having the polygon mirror 13 fixed to the rotary sleeve 10 having a hollow portion in the axial direction. The fixed shaft 4 is inserted into the hollow portion of the rotating sleeve 10, the flange 11 is attached to the distal end side of the rotating sleeve 10 in a state where the hollow portion is closed to form the air reservoir 16, and the rotating body 19 is attached by the brushless motor 24. A radial dynamic pressure air bearing that receives a dynamic pressure of air generated when it is rotated by a dynamic pressure air bearing surface composed of an inner peripheral surface of the rotating sleeve 10 and an outer peripheral surface of the fixed shaft 4, and an axial bearing using a suction type magnetic force The fixed shaft 4 and the rotating sleeve 10 are formed in a cylindrical shape having a uniform thickness with a ceramic material, and the axial bearing is disposed inside the front end side of the fixed shaft 4. It has been paid.
[0062]
Therefore, the fixed shaft 4 and the rotating sleeve 10 can be machined inexpensively and with high precision using a ceramic having good wear resistance, and the axial bearing can be accommodated in the fixed shaft 4. The dynamic pressure air bearing type polygon scanner 1 can be made small and inexpensive.
[0063]
The hydrodynamic air bearing type polygon scanner 1 has an axial bearing fixed to the inside of the distal end side on the flange 11 side of the fixed shaft 4 and a ring-shaped suction type magnetic bearing fixing portion 5 fixed to the flange 11 and ring-shaped. The attraction type magnetic bearing fixing part 5 includes the attraction type magnetic bearing fixing part 5 and an attraction type magnetic bearing rotating part 12 inserted in a state of forming a predetermined magnetic gap in the radial direction.
[0064]
Therefore, the axial bearing can be appropriately accommodated inside the distal end side of the fixed shaft 4, and the hydrodynamic air bearing type polygon scanner 1 can be made smaller and cheaper.
[0065]
Further, the housing 2 has a bottomed portion 2a to which the fixed shaft 4 is fixed at a substantially central portion thereof, and the axial bearing is housed in the cylindrical fixed shaft 4 and is erected on the bottomed portion 2a. In this state, positioning is performed in the axial direction by the spacer 17 housed inside the fixed shaft 4, and the air reservoir 16 communicates with the outside through a minute hole 11 b having a predetermined size formed in the flange 11.
[0066]
Therefore, the axial bearing can be positioned easily and appropriately, and an appropriate damping characteristic can be imparted to the axial bearing, and the reliability can be further improved. 1 can be small and inexpensive.
[0067]
Further, the axial bearing is fixed to the inside of the distal end side of the fixed shaft 4 on the flange 11 side, and the suction type magnetic bearing fixing portion 5 is fixed to the flange 11 and the suction type magnetic bearing fixing portion 5 is connected to the suction type magnetic bearing fixing portion 5. The magnetic bearing fixing portion 5 and the suction type magnetic bearing rotating portion 12 inserted in a state in which a predetermined magnetic gap is formed in the radial direction are provided. Inserted into the fixed shaft 4 while being positioned at the upper end, the upper end of the suction type magnetic bearing fixing portion 5 is held by the fixing bush 9 press-fitted into the fixed shaft 4, and held and fixed inside the fixed shaft 4. is doing.
[0068]
Therefore, the axial positioning of the axial bearing can be reliably and more easily performed without using a special jig or performing a special process, and the reliability can be further improved. The dynamic pressure air bearing type polygon scanner 1 can be made smaller and more inexpensive.
[0069]
Further, the flange 11 is attached to the rotary sleeve 10 in a state where the hollow portion of the rotary sleeve 10 is closed to form the air reservoir 16, and the polygon mirror 13 is formed of an aluminum alloy having a predetermined thermal expansion coefficient and the flange 11. The flange 11 is formed of an aluminum alloy having a thermal expansion coefficient substantially the same as that of the polygon mirror 13.
[0070]
Therefore, there is little vibration even in a high temperature state due to a temperature rise during high-speed rotation, the reflection surface accuracy of the polygon mirror 13 can be maintained with high accuracy, the reliability can be further improved, and the image quality can be improved. This can be further improved.
[0071]
The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. Needless to say.
[0072]
【The invention's effect】
  Claim 1Axis ofAccording to the receiving device, the fixed shaft fixed to the predetermined housing, the hollow rotary shaft having the hollow portion into which the fixed shaft is inserted in the axial direction, and the seat surfaceIs formedIt has a collar part and is attached in a state where a hollow part is closed and a predetermined air pocket is formed on the distal end side opposite to the housing of the hollow rotating shaft.Cap shapeA holding member, a polygon mirror mounted on the seat surface and fixed to the rotating body, and the dynamic pressure of the air generated when the rotating body is rotated by a motor, the inner peripheral surface of the hollow rotating shaft and the outer peripheral surface of the fixed shaft A bearing device that rotatably supports a rotating body in a radial direction and an axial direction by a radial dynamic pressure air bearing received by a dynamic pressure air bearing surface comprising an axial bearing using a magnetic force, and having a fixed shaft and a hollow The rotating shaft is formed in a cylindrical shape having a uniform thickness by a ceramic material.Positioned and fixed in the axial direction on a housing with a bottom in the centerSince it is housed inside the fixed shaft, the fixed shaft and hollow rotating shaft can be machined at low cost and with high precision using ceramic with good wear resistance, and the axial bearing is housed in the fixed shaft. Thus, the reliability can be improved, and the bearing device can be made small and inexpensive.
[0073]
According to the bearing device of the second aspect of the present invention, the axial bearing is mounted in the ring-shaped suction type magnetic bearing fixing portion fixed inside the fixed shaft, and in the ring-shaped suction type magnetic bearing fixing portion fixed to the holding member. The suction type magnetic bearing fixed part and the suction type magnetic bearing rotating part inserted in a state in which a predetermined magnetic gap is formed in the radial direction are provided. The bearing device can be accommodated, and the bearing device can be made smaller and cheaper.
[0074]
According to the bearing device of the third aspect of the present invention, the housing has a bottom portion having a predetermined shape to which the fixed shaft is fixed at a substantially central portion thereof, and the axial bearing is disposed inside the cylindrical fixed shaft. In addition to being housed, it is positioned in the axial direction by a predetermined spacer housed inside the fixed shaft while standing upright on the bottomed portion, and the air pocket communicates with the outside through a minute hole of a predetermined size formed in the holding member. As a result, the axial bearing can be positioned easily and appropriately, an appropriate damping characteristic can be imparted to the axial bearing, the reliability can be further improved, and the bearing device can be made compact. And cheap.
[0075]
According to the bearing device of the fourth aspect of the present invention, the axial bearing is mounted in the ring-shaped suction type magnetic bearing fixing portion fixed inside the fixed shaft, and in the ring-shaped suction type magnetic bearing fixing portion fixed to the holding member. A suction-type magnetic bearing fixing portion and a suction-type magnetic bearing rotating portion inserted in a state in which a predetermined magnetic gap is formed in the radial direction. It is inserted into the fixed shaft in a state where it is located at the upper end of the shaft, and the upper end of the suction type magnetic bearing fixing portion is held by a predetermined fixing bush press-fitted into the fixed shaft, and is held and fixed inside the fixed shaft. As a result, the axial positioning of the axial bearing can be performed reliably and easily without using a special jig or special processing, and the reliability can be further improved. , The receiving apparatus can be made more inexpensive compact.
[0076]
  Claim 5Brushless motor using bearing deviceAccording toA brushless motor capable of ultra-high speed rotation of 20000 rpm or more can be realized..AndThere is little vibration even at high temperatures due to temperature rise during high-speed rotation, and the reflection surface accuracy of the polygon mirror can be maintained with high accuracy, further improving the reliability and further improving the image quality. Can be made.
[Brief description of the drawings]
FIG. 1 is a front sectional view of a hydrodynamic air bearing type polygon scanner to which an embodiment of a bearing device of the present invention is applied.
2 is a front sectional view of an attraction type magnetic bearing portion of the dynamic pressure air bearing type polygon scanner of FIG. 1;
[Explanation of symbols]
1 Dynamic pressure air bearing type polygon scanner
2 Housing
2a Bottomed part
3 Top cover
3a Open window
4 Fixed shaft
5 Suction type magnetic bearing fixed part
6 Permanent magnet
7 First fixed yoke plate
8 Second fixed yoke plate
9 Bushing for fixing
10 Rotating sleeve
11 Flange
11a Seat
11b Fine hole
11c Outer diameter part
12 Suction type magnetic bearing rotating part
12a, 12b outer cylinder surface
12c Screw hole
13 Polygon mirror
14 leaf spring
14a Bent part
15 screws
16 Air pocket
17 Spacer
18 Rotor magnet
19 Rotating body
20 Stator core
20a Winding coil
21 Support member
22 Printed circuit board
23 Hall element
24 brushless motor
25 glass window

Claims (5)

A fixed shaft fixed to a predetermined housing;
A hollow rotary shaft having a hollow portion into which the fixed shaft is inserted in the axial direction;
A cap-shaped holding member having a flange portion on which a seat surface is formed and attached in a state in which the hollow portion is closed to form a predetermined air pocket on the distal end side opposite to the housing of the hollow rotary shaft When,
A polygon mirror mounted on the seating surface and fixed to the rotating body;
A radial dynamic pressure air bearing that receives a dynamic pressure of air generated when the rotating body is rotated by a motor at a dynamic pressure air bearing surface composed of an inner peripheral surface of the hollow rotary shaft and an outer peripheral surface of the fixed shaft;
An axial bearing using magnetic force, and a bearing device that supports the rotating body in a radial direction and an axial direction so as to be rotatable,
The fixed shaft and the hollow rotary shaft are formed in a cylindrical shape having a uniform thickness by a ceramic material,
The axial bearing is housed in the fixed shaft that is axially positioned and fixed to the housing having a bottomed portion at the center . The axial bearing includes a ring-shaped suction type magnetic bearing fixing portion fixed inside the fixed shaft;
A suction-type magnetic bearing rotating portion fixed to the holding member and inserted in a state in which a predetermined magnetic gap is formed in the radial direction in the ring-shaped suction-type magnetic bearing fixing portion; The bearing device according to claim 1, wherein the bearing device is provided. A fixed shaft fixed to a predetermined housing;
A hollow rotary shaft having a hollow portion into which the fixed shaft is inserted in the axial direction;
A holding member attached in a state in which the hollow portion is closed to form a predetermined air reservoir on the distal end side of the hollow rotating shaft opposite to the housing;
A polygon mirror fixed to the rotating body;
A radial dynamic pressure air bearing that receives a dynamic pressure of air generated when the rotating body is rotated by a motor at a dynamic pressure air bearing surface composed of an inner peripheral surface of the hollow rotary shaft and an outer peripheral surface of the fixed shaft;
An axial bearing using magnetic force, and a bearing device that supports the rotating body in a radial direction and an axial direction so as to be rotatable,
The fixed shaft and the hollow rotating shaft are formed in a cylindrical shape having a uniform thickness from a ceramic material, and
The housing has a bottom portion with a predetermined shape to which the fixed shaft is fixed at a substantially central portion thereof,
The axial bearing is housed inside the cylindrical fixed shaft and is axially positioned by a predetermined spacer housed inside the fixed shaft in an upright state on the bottomed portion,
The bearing device is characterized in that the air reservoir communicates with the outside through a minute hole having a predetermined size formed in the holding member. The bearing device according to claim 3, wherein the axial bearing includes a ring-shaped attraction type magnetic bearing fixing portion fixed inside the fixed shaft;
A suction-type magnetic bearing rotating portion fixed to the holding member and inserted in a state in which a predetermined magnetic gap is formed in the radial direction in the ring-shaped suction-type magnetic bearing fixing portion; ,
The attraction type magnetic bearing fixing portion is inserted into the fixed shaft in a state of being positioned at the upper end of the spacer, and the upper end of the attraction type magnetic bearing fixing portion is press-fitted into the fixed shaft. A bearing device, wherein the bearing device is held by a bush and is held and fixed inside the fixed shaft.   A brushless motor using the bearing device according to any one of claims 1 to 4.

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