JP2010026135A - Dynamic pressure pneumatic bearing, brushless motor, optical deflector and optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem: in a conventional dynamic pressure pneumatic bearing, dynamic pressure increases proportionally to the number of revolutions of a shaft or a sleeve and power consumption, vibration in operation, noise in operation and electric radiation noise increase. <P>SOLUTION: The dynamic pressure pneumatic bearing includes a shaft on the outer peripheral face of which a helical groove is formed and a sleeve inserted into the shaft with a gap, thus the power consumption, the vibration in operation, the noise in operation and the electric radiation noise are suppressed better than the case in the conventional dynamic pressure pneumatic bearing by gradually increasing the width of the groove from the one end of the groove to the other end. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a dynamic pressure air bearing, a brushless motor, an optical deflector, and an optical scanning device used in an image forming apparatus such as a laser printer and a digital copying machine, an exposure apparatus for medical equipment, and the like.

  Optical scanning devices used in image forming apparatuses such as laser printers and digital copying machines include a light source that emits laser light, an optical deflector that deflects and reflects the laser light emitted from the light source, and deflected and reflected by the optical deflector. A mirror, a lens, and the like for guiding the laser beam to the photosensitive drum or the like (see, for example, Patent Document 1 and Patent Document 2).

Here, what is shown in FIG. 15 is known as an optical deflector (for example, refer patent document 3).
This optical deflector has a columnar fixed shaft 101 fixedly disposed on a housing 100 and a rotating body 110 rotatably supported by the fixed shaft 101. The rotating body 110 includes a sleeve 111 disposed with a slight gap between the rotating shaft 110, a ring-shaped magnet 112 fixedly disposed inside the upper portion of the sleeve 111, and the center of the sleeve 111. A polygon mirror 113 fixedly disposed on the outside of the part and a ring-shaped rotor magnet 115 fixedly disposed on the outer side of the lower portion of the sleeve 111 via a flange 114 are provided. Reference numeral 116 denotes a groove in which a balance weight (not shown) for correcting the eccentricity of the weight of the rotating body 110 is attached.

  A ring-shaped magnet 102 is fixedly disposed on the outer side of the upper portion of the fixed shaft 101 so as to face a ring-shaped magnet 112 provided on the rotating body 110. The rotating body 110 is supported by the ring-shaped magnets 102 and 112. A thrust magnetic bearing S for bearing in the thrust direction is configured.

  Furthermore, an iron core coil 103 is fixedly disposed in the housing 100 so as to face a ring-shaped rotor magnet 115 provided on the rotating body 110, and the rotating body 110 is rotated by the rotor magnet 115 and the iron core coil 103. A brushless motor M is configured.

  Of the sleeve 111 of the rotating body 110, the inner peripheral surface 111a facing the fixed shaft 101 is finished with a bearing surface, while the outer peripheral surface 101a of the fixed shaft 101 facing the inner peripheral surface 111a of the sleeve 111. Is formed with a herringbone groove 104 as indicated by a broken line in the figure. The herringbone groove 104 constitutes a radial dynamic pressure air bearing R that supports the rotating body 110 in the radial direction. In some cases, instead of the herringbone groove 104, a spiral groove is provided on the fixed shaft (see, for example, Patent Document 4).

In this optical deflector, when the rotating body 110 is rotated by the brushless motor M, the rotating body 110 is supported in a non-contact manner with a fixed distance (gap) from the fixed shaft 101 by the radial dynamic pressure air bearing R. The thrust magnetic bearing S supports the fixed shaft 101 at a constant height. Accordingly, there is an advantage that the height of the optical deflector can be made lower than that of a type using a dynamic pressure bearing as a bearing in the thrust direction.
Moreover, since the position of the center of gravity of the rotating body 110 can be set to the position of the approximate center in the axial direction of the rotating body 110, the rotating body 110 can be stably rotated.

JP 2007-183327 A JP-A-10-268222 JP-A-5-071532 JP 2004-332784 A

  A rotating device such as an optical deflector using a dynamic pressure air bearing needs a force (dynamic pressure) for holding the rotating body so as to withstand an external force applied during the operation of the rotating device. Here, the external force means a force received from the outside due to an impact or the like, and more specifically, an impact force received by an image forming apparatus including an optical deflector due to an earthquake, an operator's collision, or the like.

  On the other hand, the external force applied from the outside is unrelated to the rotational speed of the rotating device. For this reason, it is desirable that the rotating device always has a necessary holding force (dynamic pressure) that is not affected by an external force, from the start to the end of the rotating device, regardless of the rotational speed of the rotating device.

However, the above-described dynamic pressure air bearings (Patent Documents 3 and 4) have the following problems because the dynamic pressure that is the holding force of the rotating body varies greatly depending on the number of rotations of the rotating device.
(1) Since the generated dynamic pressure increases in proportion to the increase in the rotational speed of the rotating body, it reaches a rotational speed (predetermined rotational speed) set to obtain a necessary holding force that is not affected by external force. There is a problem that it takes time to start up the apparatus and it takes time to start up the apparatus (until it can be used).

(2) At the same time, until the predetermined number of rotations is reached, there is a problem in that a necessary holding force that is not affected by the external force cannot be obtained and the external force cannot be endured.
(3) Furthermore, a common dynamic pressure air bearing may be used at a plurality of rotation speeds (for example, high speed and low speed). However, if the predetermined rotation speed is set to the high speed side, the dynamic pressure is insufficient on the low speed side and the external force If the predetermined number of revolutions is set on the low speed side, excessive dynamic pressure is generated on the high speed side, which increases power consumption, vibration during operation, noise during operation, and electrical radiation noise. It was.

  Here, as a case where the common dynamic pressure air bearing is used at a plurality of rotation speeds, for example, when the light deflector is used at a plurality of rotation speeds in an image forming apparatus having one light deflector, This is the case when a dynamic pressure air bearing is used as a standard part and a dynamic pressure air bearing that is a standard part is used in a plurality of image forming apparatuses that use different rotational speeds.

  The present invention has been made to solve such a problem, and the width of the spiral groove formed on the outer peripheral surface of the shaft or the inner peripheral surface of the sleeve is gradually increased from one end to the other end. With a simple configuration, the desired dynamic pressure can be obtained in a short time (reaching the predetermined number of rotations in a short time), and the excessive dynamic pressure during high-speed rotation can be suppressed to reduce power consumption and operation. An object of the present invention is to provide a dynamic pressure air bearing, a brushless motor, an optical deflector, and an optical scanning device that suppress an increase in vibration, noise during operation, and electric radiation noise.

(First invention)
The dynamic pressure air bearing according to the first aspect of the present invention comprises a shaft and a sleeve inserted with a gap in the shaft, and has a spiral groove formed on the outer peripheral surface of the shaft or the inner peripheral surface of the sleeve. Regarding the compressed air bearing, the width of the groove is gradually increased from one end of the groove toward the other end.

(Second invention)
The dynamic pressure air bearing according to a second aspect of the present invention is the dynamic pressure air bearing according to the first aspect, wherein a plurality of grooves are formed on the outer peripheral surface of the shaft or the inner peripheral surface of the sleeve, and the center lines of the plurality of grooves are formed without intersecting each other. They are parallel to each other. Here, the center line of the groove is a line formed by connecting points equidistant from both wall surfaces in the short direction of the groove.

(Third invention)
A dynamic pressure air bearing according to a third invention is the one in which the groove is bent at one or a plurality of locations in the first invention or the second invention.

(Fourth invention)
The brushless motor according to a fourth aspect of the present invention is the hydrodynamic air bearing of the first aspect, the second aspect or the third aspect, wherein the rotor magnet is fixed to the shaft, the sleeve is fixed to the substrate, and the motor core fixed to the substrate is It is opposite to the rotor magnet.

(Fifth invention)
The brushless motor according to a fifth aspect of the present invention is the hydrodynamic air bearing of the first, second or third aspect, wherein the rotor magnet is fixed to the sleeve, the shaft is fixed to the substrate, and the motor core fixed to the substrate is It is opposite to the rotor magnet.

(Sixth invention)
An optical deflector according to a sixth aspect of the invention is the brushless motor according to the fourth aspect of the invention, further comprising a polygon mirror fixed to the shaft.

(Seventh invention)
An optical deflector according to a seventh aspect of the invention is the brushless motor of the fifth aspect of the invention, further comprising a polygon mirror fixed to the sleeve.

(Eighth invention)
An optical deflector according to an eighth aspect of the present invention relates to an optical scanning device including the optical deflector of the sixth aspect or the seventh aspect.

  According to the present invention, desired dynamic pressure can be obtained in a short time, and excessive generation of dynamic pressure during high-speed rotation is suppressed to reduce power consumption, vibration during operation, noise during operation, and electric radiation noise. It is possible to provide a dynamic pressure air bearing, a brushless motor, an optical deflector, or an optical scanning device that suppresses an increase in the above.

  Hereinafter, the present invention will be described in detail using examples.

A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a plan view of an optical scanning device according to the present invention, FIG. 2 is a cross-sectional view showing a state in which an optical deflector is fixed to a housing (AA cross-sectional view in FIG. 1), and FIG. FIG. 4 is a perspective view (indicated by an arrow B in FIG. 3) of an annular protrusion formed on the surface of the housing. In order to simplify the explanation, in FIG. 2, the sections other than the fixed shaft are shown in a cross-sectional view. Moreover, in FIG. 2, the groove | channel which exists in the part which cannot be seen (opposite side of a fixed axis | shaft) is not illustrated by the wavy line.

[Optical scanning device]
First, the basic configuration of the optical scanning device according to the present invention will be described.
As shown in FIG. 1, an optical scanning device 1 includes a light source 2 such as a laser diode that emits laser light 3, a collimator lens 4 that collimates the laser light 3 emitted from the light source 2, and a collimator lens 4. A cylindrical lens 5 that narrows the laser beam 3 that has passed through in the sub-scanning direction, an optical deflector 6 that includes a polygon mirror 14 that deflects and reflects the laser beam 3 that has passed through the cylindrical lens 5 in the main scanning direction, and the polygon mirror 14 deflects the laser beam 3. It has an Fθ lens 8 and a reflection mirror 9 that guide the reflected laser light 3 to the photoreceptor 7.

  Here, the main scanning direction refers to the moving direction of the laser beam 3 when the optical scanning device 1 irradiates the surface of the photoconductor 7 with the laser beam 3. The sub-scanning direction is the moving direction of the surface of the photoconductor 7. The main scanning direction and the sub-scanning direction are orthogonal to each other.

In addition, the optical scanning device 1 includes a reflection mirror 10 and a detection sensor 11 for detecting the timing at which the laser beam 3 scans the surface of the photoreceptor 7.
The light source 2, the collimator lens 4, the cylindrical lens 5, the optical deflector 6, the Fθ lens 8, the reflection mirrors 9 and 10, and the detection sensor 11 are fixed to the housing 12.

[Optical deflector]
Next, the configuration of the optical deflector 6 will be described in detail with reference to FIG.
As shown in FIG. 2, the optical deflector 6 includes a metal substrate 13 and a multistage columnar ceramic fixed shaft 16 (outer diameter φ11 mm−4 μm) fixed to the substrate 13 by a plurality of screws 15. And a rotating body 17 rotatably supported on the fixed shaft 16.

  The rotating body 17 includes a ceramic sleeve 18 (inner diameter φ11 mm, outer diameter φ16 mm), a flange 46 fixed to the sleeve by press fitting or the like, and an inner peripheral surface of the skirt portion 19 of the flange 46 by an adhesive or the like. The fixed rotor magnet 20, the polygon mirror 14 mounted on the upper surface of the flange 46, the spring 21 mounted on the upper surface of the polygon mirror 14, and the press that is press-fitted and fixed to the flange 46 while pressing the spring 21 downward. The member 22 is composed of a lid 63 fixed to the upper surface of the flange 46 with a screw or the like (not shown).

The polygon mirror 14 is fixed by being pressed against the upper surface of the flange 46 by the elastic force generated by the spring 21 because the spring 21 is pressed downward by the pressing member 22.
A ring-shaped motor core 23 having a plurality of coils is fixed to the substrate 13 with screws 15, an adhesive, and the like, and the terminals of the coils are soldered to wirings provided on the substrate 13.

  A coil of the motor core 23 fixed to the board 13 is excited by an electric signal sent from a driver IC (Integrated Circuit) 24 or the like mounted on the board 13, and the rotor magnet 20 facing the motor core 23 moves. As a result, the rotating body 17 rotates at a high speed.

  Further, as shown in FIG. 2, three spiral grooves 50 are formed on the outer peripheral surface of the fixed shaft 16. These three grooves 50 are set so that their center lines (illustrated by a one-dot chain line in FIG. 2) are parallel to each other and adjacent center lines are equally spaced so that the grooves 50 do not cross each other. Yes. Each groove 50 is formed so that the width of the groove gradually increases from the lower end (one end) 51 to the upper end (other end) 52 of the portion facing the inner peripheral surface of the flange 18. In Example 1, the groove width at one end 51 was 2 mm, the groove width at the other end 52 was 4 mm, and the depth of the groove 50 was 4 μm (constant). That is, the groove width of the groove 50 increases linearly from one end (groove width 2 mm) to the other end (groove width 4 mm).

  A dynamic pressure air bearing is constituted by the fixed shaft 16 in which the spiral groove 50 is formed and the sleeve 18 inserted with a gap (4 μm) from the fixed shaft 16. For this reason, when the rotating body 17 starts to rotate clockwise as viewed from above, a desired dynamic pressure is generated in a short time, and generation of excessive dynamic pressure during high-speed rotation is suppressed, thereby reducing power consumption, An increase in vibration during operation, noise during operation, and electric radiation noise can be suppressed.

[Fixed structure of optical deflector]
Next, the fixing structure of the optical deflector 6 will be described with reference to FIGS.
As shown in FIG. 2, the substrate 13 of the optical deflector 6 is placed on the upper surface 26 of an annular protrusion 25 formed on the surface of the housing 12. The protruding amount of the annular protrusion 25 with respect to the upper surface of the housing 12 is the same everywhere, and the upper surface 26 of the protrusion 25 is flat. When the substrate 13 is placed on the upper surface 26 of the protrusion 25, a fixed shaft 16 fixed to the substrate 13 is used at the center 27 of the circle formed by the annular protrusion 25 shown in FIG. The center (center axis) of is located.

  As shown in FIG. 3, four through holes 28 are formed in the vicinity of the inner side of the annular protrusion 25 of the housing 12. The through hole 28 only needs to be formed at a position close to the inner peripheral surface of the protrusion 25, and a female screw 31 is formed at the position of the substrate 13 corresponding to the through hole 28. Here, the position of the substrate 13 corresponding to the through hole 28 is the top surface of the protrusion 25 so that the center 27 of the circle formed by the annular protrusion 25 coincides with the center axis of the fixed shaft 16 as described above. The position of the substrate 13 immediately above the through-hole 28 when the substrate 13 is placed on 26. That is, the through hole 28 and the female screw 31 are located on the vertical line.

  As shown in FIG. 2, the male screw 29 is inserted into the through hole 28 from the back surface of the housing 12, and the tip of the male screw 29 is screwed into a female screw 31 formed on the substrate 13 and tightened (screwed). Is fixed to the housing 12. More specifically, in the first embodiment, the male screw 29 is inserted into each of the four through holes 28 formed at intervals of A = 90 ° in the housing 12, and the substrate 13 corresponding to the four through holes 28. The optical deflector 6 is fixed to the housing 12 of the optical scanning apparatus 1 by screwing the tip of the male screw 29 into the four female screws 31 formed at 90 ° intervals at the positions of the male screw 29 and tightening the male screw 29. Yes.

  Since the four male screws 29 are located in the vicinity of the inside of the housing 12, after the male screws 29 are tightened to such an extent that the optical deflector 6 can be fixed to the housing 12, at least one of the four male screws 29 is further provided. When the tightening force is increased, the substrate 13 in the vicinity of the fixed shaft 16 is deformed. As a result, the angle of the fixed shaft 16 with respect to the vertical direction can be changed, so that the axis collapse can be corrected.

A second embodiment according to the present invention will be described below with reference to FIG.
FIG. 5 is a sectional view showing a state in which the optical deflector is fixed to the housing. In order to simplify the explanation, in FIG. 5, the sections other than the fixed shaft 16 are shown in cross section.
Only differences from the first embodiment will be described in detail, and description of the same parts as those of the first embodiment will be omitted.

  The main difference between the second embodiment and the first embodiment is that the number of spiral grooves 50 formed on the fixed shaft 16 is one. In this case, the angle of the groove 50 with respect to the horizontal line is reduced so that the groove 50 makes at least one round of the outer periphery of the fixed shaft 16. If it does so, the effect similar to above-mentioned Example 1 can be acquired.

A third embodiment according to the present invention will be described with reference to FIG.
FIG. 6 is a side sectional view of the optical deflector. For the sake of simplicity, FIG. 6 shows a cross section other than the rotating shaft.

  The optical deflector 6 is a cylindrical and ceramic sleeve 18 (inner diameter φ11 mm-4 μm, outer diameter φ16 mm) fixed to a housing 49 made of aluminum with screws or the like, and is rotatably supported by the sleeve 18. The rotating body 17 is constituted.

  The rotating body 17 has a cylindrical shape inserted with a slight gap (4 μm) between the rotating body 17 and a ceramic rotating shaft 47 (outside diameter φ11 mm), and aluminum fixed to the rotating shaft 47. A flange 46 made of aluminum, an aluminum polygon mirror 14 which is placed on the flange 46 and has a large number of mirror surfaces on its outer peripheral surface, and a ring-shaped leaf spring 21 placed on the polygon mirror 14. A pressing member 22 made of aluminum, which is placed on the leaf spring 21 and is forcibly inserted into the upper portion of the rotary shaft 47 by press fitting or shrink fitting so as to press the polygon mirror 14 against the upper surface of the flange 46; The rotor magnet 20 fixed to the skirt portion 19 of the flange 46 with an adhesive or the like, and the outer peripheral surface of the sleeve 18 so as to face the rotor magnet 20 The motor core 23 is attached to the motor core 23.

Since the thrust magnetic bearing is constituted by the attractive force between the rotor magnet 20 and the motor core 23, the rotating body 17 is always kept in a floating state.
A metal substrate 13 is fixed to the housing 49, and a brushless motor control circuit (not shown) composed of the rotor magnet 20 and the motor core 23 is mounted on the substrate 13.

  In this optical deflector 6, a radial dynamic pressure bearing is configured by the outer peripheral surface of the rotating shaft 47 and the inner peripheral surface of the sleeve 18. That is, one spiral groove 50 is formed on the outer peripheral surface of the rotating shaft 47. The groove 50 is formed so that the width of the groove gradually increases from the lower end (one end) 51 of the portion facing the inner peripheral surface of the sleeve 18 toward the upper end (other end) 52.

  For this reason, when the rotating body 17 rotates counterclockwise as viewed from above, the air around the optical deflector 6 is sucked into the brushless motor, and the outer peripheral surface of the rotating shaft 47 and the inner peripheral surface of the sleeve are Dynamic pressure is generated between them. Then, the desired dynamic pressure can be obtained in a short time, and the generation of excessive dynamic pressure during high-speed rotation is suppressed to suppress the increase in power consumption, vibration during operation, noise during operation, and electric radiation noise. be able to.

  The groove 50 sucks air around the brushless motor in one direction (downward) toward the inside of the brushless motor, and thus differs from the two directions (upward and downward) as in the prior art. Therefore, the axial length of the groove for generating the dynamic pressure can be reduced to about half of the conventional length.

A fourth embodiment according to the present invention will be described below with reference to FIG.
FIG. 7 is a sectional view showing a state in which the optical deflector is fixed to the housing. In order to simplify the explanation, in FIG. 7, the sections other than the rotating shaft are shown in cross section. Further, a groove existing in an invisible part (opposite side of the rotation axis) is not shown by a wavy line or the like.
Only differences from the third embodiment will be described in detail, and the same parts as those of the third embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  The main difference between the fourth embodiment and the third embodiment is that the number of spiral grooves 50 formed on the rotating shaft 47 is three. These three grooves 50 are set at equal intervals so that their center lines (shown by a one-dot chain line in FIG. 7) do not cross each other in parallel. And each groove | channel 50 is formed so that the width | variety of a groove | channel may become large gradually toward the upper end (other end) from the lower end (one end) 51 of the part facing the inner peripheral surface of the flange 18. As shown in FIG. In Example 1, the groove width at one end 51 was 2 mm, the groove width at the other end 52 (not shown) was 4 mm, and the depth of the groove 50 was 4 μm (constant).

[Rotation test results]
FIG. 10 shows the result of the rotation test using this optical deflector 6.
In FIG. 10, the horizontal axis represents the rotational speed (rpm) of the rotating body 17, and the vertical axis represents the dynamic pressure (total pressure (MPa) of the bearing surface) generated by the rotation of the rotating body 17. The circles in FIG. 10 are data of the optical deflector 6 according to the fourth embodiment shown in FIG.

  As a comparative example, FIG. 10 shows data of the optical deflector shown in FIGS. 8 and 9 in which only the groove shape of the optical deflector 6 shown in FIG. 7 is changed. The data indicated by Δ in FIG. 10 is for the optical deflector shown in FIG. 8 in which a spiral groove having a constant (uniform) groove width formed on the rotation axis is used. Further, the data indicated by □ in FIG. 10 is for the optical deflector shown in FIG. 9 in which a herringbone groove used conventionally is formed on the rotation axis. 8 and FIG. 9, the grooves existing in the invisible part (the side opposite to the rotation axis) are not shown by wavy lines or the like.

  As can be seen from the graph shown in FIG. 10, when the dynamic pressure required by the optical deflector 6 is 1.0 MPa, the optical deflector 6 shown in the fourth embodiment is required until the rotational speed reaches 10,000 rpm. Dynamic pressure can be generated. It can also be seen that the increase in the dynamic pressure is lower than that of the conventional optical deflector even when the rotational speed is increased.

  On the other hand, the conventional optical deflector shown in FIGS. 8 and 9 reaches the dynamic pressure required by the optical deflector shown in FIG. In both cases, it can be seen that when the rotational speed is increased, the dynamic pressure is greatly increased over the optical deflector of the fourth embodiment.

  Excessive dynamic pressure exceeding the required specifications causes increase in current consumption, vibration during operation, noise during operation, and electric radiation noise, and therefore it is necessary to keep it as low as possible. 10, the dynamic pressure air bearing, the brushless motor, the optical deflector, and the optical scanning device according to the present invention have the conventional spiral groove (FIG. 8) and herringbone groove (FIG. 9). It can be seen that the generation of excessive dynamic pressure can be suppressed as compared with the optical deflector and the like provided, so that increase in current consumption, vibration during operation, noise during operation, and electrical radiation noise can be suppressed.

A fifth embodiment according to the present invention will be described below with reference to FIG.
FIG. 11 is a cross-sectional view showing a state where the optical deflector is fixed to the housing. In order to simplify the description, in FIG. 11, the sections other than the rotating shaft are shown in cross section. A groove existing in an invisible part (opposite side of the rotation axis) is not shown by a wavy line or the like.
Only differences from the fourth embodiment will be described in detail, and the same parts as those of the fourth embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  The main difference between the fifth embodiment and the fourth embodiment is that the spiral groove 50 formed on the rotating shaft 47 is bent at one place. Even with this configuration, it is possible to obtain the same effects as those of the fourth embodiment.

A sixth embodiment according to the present invention will be described below with reference to FIG.
FIG. 12 is a cross-sectional view showing a state where the optical deflector is fixed to the housing. In order to simplify the explanation, in FIG. 12, the section other than the rotating shaft is shown in cross section. A groove existing in an invisible part (opposite side of the rotation axis) is not shown by a wavy line or the like.
Only differences from the fifth embodiment will be described in detail, and the same parts as those of the fifth embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  The main difference between the sixth embodiment and the fifth embodiment is that the spiral groove 50 formed on the rotating shaft 47 is bent at a plurality of locations. Even with this configuration, it is possible to obtain the same effects as those of the fourth embodiment.

  The above-described embodiments have been illustrated for the purpose of explanation, and the present invention is not limited to these embodiments. The present invention can be recognized by those skilled in the art from the claims, the description, and the drawings. Modifications, deletions, and additions are possible as long as they are not contrary to the technical idea of the above.

  In the above-described embodiments, the shaft and sleeve are made of ceramic, but the present invention is not limited to this, and a metal such as iron or aluminum may be used as the material of the shaft and sleeve.

  For example, in the above-described embodiment, the spiral groove 50 is formed on the outer peripheral surface of the shaft. However, the groove 50 is not formed on the outer peripheral surface of the shaft, and as shown in FIGS. Alternatively, a spiral groove 50 may be used on the inner peripheral surface. Specifically, the sleeve shown in FIGS. 13 and 14 is replaced with, for example, the sleeve 18 of the optical deflector 6 shown in FIG. 2, and the spiral groove 50 of the fixed shaft 16 of the optical deflector 6 shown in FIG. The optical deflector 6 may be configured by eliminating the above. Even in this case, it is possible to obtain the same effect as that shown in the above-described embodiment.

FIG. 13 is a front view of a sleeve in which a spiral groove 50 is formed on the inner peripheral surface, and FIG. 14 is a cross-sectional view of FIG. 13 cut in half vertically.
For the sleeve 62, when the sleeve is made of ceramic, a mask sheet having the same shape as the groove 50 is prepared on the inner peripheral surface of the sleeve 62, and the mask sheet is attached to the inner peripheral surface of the sleeve 62. The inner peripheral surface of the sleeve 62 can be manufactured by subjecting it to shot peening and removing the mask sheet.

  When the sleeve is made of a metal such as iron, the sleeve 62 is provided with a mask sheet having the same shape as the groove 50 on the inner peripheral surface of the sleeve 62, and the mask sheet is used as the inner peripheral surface of the sleeve 62. It can be manufactured by applying a solution for dissolving the metal to the inner peripheral surface of the sleeve 62 and then washing the solution to remove the mask sheet.

  Further, in the above-described third to sixth embodiments, the optical deflector 6 fixed to the housing 49 is shown, but is above the substrate 13 including the substrate 13 in the optical deflector 6 shown in the third to sixth embodiments. The configuration may be replaced with the optical deflector 6 shown in the first embodiment as it is. That is, the optical deflector 6 shown in the third to sixth embodiments can be used in the optical scanning device shown in FIG.

  Further, in the above-described embodiment, the case of one or three grooves 50 is shown, but the number is not limited to this number, and may be two or five.

  The present invention is applied to a dynamic pressure air bearing, a brushless motor, an optical deflector, and an optical scanning device used in an image forming apparatus or the like.

1 is a plan view of an optical scanning device according to the present invention (Example 1). (Example 1) which is sectional drawing which shows the state by which the optical deflector was fixed to the housing. (Example 1) which is the elements on larger scale (plan view) of the attachment location of the optical deflector in a housing. (Example 1) It is a perspective view (arrow B in FIG. 3) of the annular | circular shaped protrusion formed in the surface of a housing. (Example 2) which is sectional drawing which shows the state by which the optical deflector was fixed to the housing. (Example 3) which is a sectional view which shows the state where the optical deflector was fixed to the housing. (Example 4) which is sectional drawing which shows the state by which the optical deflector was fixed to the housing. (Example 4) which is a sectional view showing the state where the conventional optical deflector was fixed to the housing. (Example 4) which is a sectional view showing the state where the conventional optical deflector was fixed to the housing. (Example 4) which is a graph which shows the relationship between the rotation speed of a rotary body, and the pressure of dynamic pressure. (Example 5) which is sectional drawing which shows the state by which the optical deflector was fixed to the housing. (Example 6) which is sectional drawing which shows the state by which the optical deflector was fixed to the housing. It is a front view of a sleeve. It is sectional drawing of a sleeve. It is sectional drawing of the conventional optical deflector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical scanning device 6 Optical deflector 12 Housing 13 Board | substrate 14 Polygon mirror 16 Fixed shaft 17 Rotor 18 Sleeve 20 Rotor magnet 23 Motor core 50 Spiral groove 51 One end 52 The other end

Claims (8)

A shaft and a sleeve inserted with a gap in the shaft;
In the dynamic pressure air bearing in which a spiral groove is formed on the outer peripheral surface of the shaft or the inner peripheral surface of the sleeve,
A hydrodynamic air bearing characterized in that the width of the groove is gradually increased from one end to the other end of the groove. A plurality of the grooves are formed on the outer peripheral surface of the shaft or the inner peripheral surface of the sleeve;
2. The hydrodynamic bearing according to claim 1, wherein the plurality of grooves do not intersect each other, and the center lines of the plurality of grooves are parallel to each other.   The hydrodynamic air bearing according to claim 1, wherein the groove is bent at one or a plurality of locations. In the hydrodynamic air bearing according to any one of claims 1 to 3,
A rotor magnet is fixed to the shaft,
The sleeve is fixed to the substrate;
A brushless motor in which a motor core fixed to the substrate faces the rotor magnet In the hydrodynamic air bearing according to any one of claims 1 to 3,
A rotor magnet is fixed to the sleeve,
The shaft is fixed to the substrate;
A brushless motor in which a motor core fixed to the substrate faces the rotor magnet The brushless motor according to claim 4,
Furthermore, an optical deflector having a polygon mirror fixed to the axis The brushless motor according to claim 5,
Furthermore, an optical deflector in which a polygon mirror is fixed to the sleeve   An optical scanning device comprising the optical deflector according to claim 6.

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