JP3697918B2 - Optical deflection apparatus and motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical deflection device and a motor mounted on an optical device such as a laser printer.
[0002]
[Prior art]
Conventionally, an optical deflection device is provided in an optical device such as a laser printer. A dynamic pressure generating groove is formed on a bearing of a rotating shaft of a motor that supports a rotating polygon mirror used in an optical deflecting device in order to enable high-speed copying. The dynamic pressure generating groove causes the fluid to flow in as the rotating shaft rotates at a high speed to generate positive pressure, and rotates the rotating shaft to lubricate.
[0003]
A motor that uses this dynamic pressure generating groove has a rotating shaft and bearing that are worn when starting / stopping or receiving an impact, and dust generated by wear is sandwiched between the rotating shaft and the rotating shaft. There was a problem such as preventing the rotation of.
[0004]
The following conventional techniques are disclosed as countermeasures against dust and the like.
[0005]
As a method of preventing dust contamination from the outside, the gap between the rotary shaft, which is the air intake of the thrust bearing, and the fixed member is smaller than the depth of the dynamic pressure generating groove, and the ingress of dust is blocked by the air intake, Japanese Patent Application Laid-Open No. 8-200333 discloses an invention in which fine dust is accumulated in a dynamic pressure generating groove.
[0006]
Japanese Patent Laid-Open No. 8-261239 discloses an invention in which a wear material of a thrust bearing composed of a rotating shaft and a sliding material is utilized as a lubricant.
[0007]
[Problems to be solved by the invention]
However, in Japanese Patent Laid-Open No. 8-200333, although large dust can be blocked by the gap of the air intake, there is no effect on dust smaller than the gap, and if dust enters and accumulates in the dynamic pressure generating groove. The above-mentioned problem occurs. Further, the wear on the inner peripheral surface of the radial bearing is not taken into consideration.
[0008]
Japanese Patent Laid-Open No. 8-261239 uses a rotating shaft and a sliding material that have been treated to generate a wear product having a shear strength lower than that of the rotating shaft and the sliding material. It is a material, and the cost is high due to processing at the time of film thickness generation. As shown in FIGS. 14 and 15, when the lower end portion of the rotating shaft 2 is convex and the thrust bearing (sliding material) 4 is flat, a radial bearing (not shown) and the rotating shaft are provided. Precipitate 6 such as wear powder generated by contact with the dust, dust entering from the outside, lubricating oil deteriorated with time accumulates in the sliding portion 8, and friction torque of the rotating shaft 2 is generated by the viscosity of the precipitate 6. However, there is a problem that the motor cannot be started.
[0009]
The present invention has been made in view of the above circumstances, and suppresses as much as possible generation of wear powder generated in the gap between the rotating shaft and the sleeve, alteration of the lubricating oil, and friction torque of the rotating shaft due to external dust intrusion. As a result, an object is to provide an optical deflecting device and a motor that are inexpensive and have a long life.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a first aspect of the present invention provides a rotating body including a rotating shaft that supports a rotating polygon mirror, a thrust bearing portion that supports the rotating shaft in a thrust direction, and the rotating shaft in a radial direction. And a drive member that rotates the rotating body, and a gap between the rotary shaft and the bearing member is filled with lubricating oil, and the rotary shaft is substantially horizontal. In the optical deflecting device arranged and rotated, three dynamic pressure generating grooves extending in the thrust direction on the inner peripheral surface of the radial bearing portion are provided, and the two dynamic pressure generating grooves are formed substantially in the lower part in the gravitational direction. It is arranged .
[0011]
The invention described in claim 1 will be described.
[0018]
Three dynamic pressure generating grooves extending in the thrust direction on the inner peripheral surface of the radial bearing portion are provided, and two dynamic pressure generating grooves are arranged in the lower portion of the substantially gravity direction, so that the radial bearing portion and the rotating shaft are Precipitates such as wear powder generated by sliding, dust entering from the outside, and lubricating oil that deteriorates with time gather below the inner peripheral surface. Since the two dynamic pressure generating grooves are disposed in the lower part of the inner peripheral surface of the radial bearing portion in the direction of gravity, the deteriorated lubricating oil and the like can be stored in the dynamic pressure generating grooves disposed in the lower part .
[0022]
DETAILED DESCRIPTION OF THE INVENTION
The optical deflection apparatus according to the first embodiment of the present invention will be described in detail below. First, a schematic description of a laser printer using an optical deflecting device will be given.
(Laser printer)
As shown in FIG. 12, the laser printer 12 reflects the scanning light emitted from the optical scanning device 16 accommodated in the optical box 14 by a mirror 18 and irradiates the photosensitive drum 20 with the scanning light on the photosensitive drum 20. To form an image.
[0023]
In the optical scanning device 16, as shown in FIG. 13, the laser beam L emitted from the semiconductor laser 22 is reflected by the rotary polygon mirror 26 constituting the optical deflecting device 10 via the collimator lens 24, and via the lens 28. The light is emitted to the mirror 18 (photosensitive drum 20).
(Light deflection device)
The optical deflecting device 10 used for the laser printer 12 will be described in detail below.
[0024]
The light deflection apparatus 10 includes a motor 31 that is erected vertically on an iron printed board 30 that also serves as a housing. The motor 31 includes a rotating shaft 44 and a rotating body 34 that is rotatably supported by a sleeve member 32.
[0025]
As shown in FIG. 2, the sleeve member 32 includes a radial bearing portion 40 and a thrust bearing portion 42, and a substantially cylindrical hole portion 36 is formed. A herringbone-shaped dynamic pressure generating groove 38 having a groove depth of about several μm is formed on the inner peripheral surface of the radial bearing portion 40 (hole portion 36). Further, the thrust bearing portion 42 (the bottom surface of the hole portion 36) is formed from a sliding material (a thermoplastic industrial resin agent). Further, as shown in FIGS. 4 and 5, the thrust bearing portion 42 is formed with a groove 43 that circulates in a portion where an end surface 45 of a rotating shaft 44 described later does not contact.
[0026]
The rotating body 34 includes a rotating shaft 44 having an end surface 45 abutting the thrust bearing portion 42 formed in an R-curved surface, a rotating polygon mirror 26 attached to one end of the rotating shaft 44 by a leaf spring 46, and a rotating shaft 44. And a drive magnet 52 which is installed on the inner peripheral surface of the yoke member 50 and is alternately magnetized with multiple north and south poles.
[0027]
By inserting the rotating shaft 44 into the hole 36, an armature coil group 54 fixed to the outer peripheral portion of the sleeve member 32 is disposed at a position facing the drive magnet 52 in the radial direction.
[0028]
The clearance between the rotating shaft 44 and the hole 36 is about several μm to several tens of μm, and the clearance is filled with lubricating oil.
[0029]
The printed circuit board 30 is provided with a magnet position detector 62 at a position facing the control unit 60 and the drive magnet 52 in the thrust direction.
[0030]
As shown in FIG. 3, the control unit 60 is driven by supplying an excitation current to the armature coil group 54 based on a signal from the magnet position detector 62 when a start signal is input to the motor drive circuit 70. The motor 31 (rotating body 34) is rotated at high speed by the induced magnetic force with the magnet 52. The speed information signal of the rotating body 34 obtained by the speed detector 74 is fed back to a constant speed control circuit (PLL control) 76, and compared with a reference signal corresponding to the target rotational speed, and the motor is driven to compensate for the error. The circuit 70 is controlled to rotate at a constant speed.
(Explanation of operation of optical deflector)
The operation and action of the optical deflection apparatus 10 according to the present embodiment configured as described above will be described.
[0031]
Here, the operations of the laser printer 12 and the optical deflection apparatus 10 will be described. When the activation signal is input to the above-described control unit 60, the rotating body 34 rotates at a constant speed within a range of 10,000 to 30,000 rpm. As a result, the rotary polygon mirror 26 scans the scanning light in a predetermined direction. At this time, as shown in FIG. 6, oil flows into the dynamic pressure generating groove 38 to generate a positive pressure, and the rotating shaft 44 is prevented from coming into contact with the radial bearing portion 40. After the image recording ends, a stop signal is input to the control unit 60, whereby the rotation of the rotating body 34 is stopped. This operation is performed at least about 400,000 times for a printer.
[0032]
The relationship between the rotating shaft 44, the sleeve member 32, and the lubricating oil during the starting and stopping operations in the optical deflecting device 10 will be described.
[0033]
Since the rotary shaft 44 in the radial direction is supported by the herringbone-like dynamic pressure generating groove 38, the dynamic pressure (axial rigidity) is the relative speed between the rotary shaft 44 and the sleeve member 32 (the inner peripheral surface of the hole 36). It grows in proportion to the difference. Therefore, the dynamic pressure immediately after the start and just before the stop is small, and the rotating shaft 44 tilts due to the unbalance of the rotating body 34. As a result, the viscous shear stress acting on the lubricating film of the lubricating oil formed at the opening of the hole 36 is locally increased, and the fluid lubrication state is disturbed to generate heat.
[0034]
Here, the deterioration factors of the lubricating oil will be described. Deterioration factors of the lubricating oil include heat, a hydropolymerization reaction, base oil oxidation, and contamination with impurities.
[0035]
The thermal deterioration is caused by the increase in the environmental temperature, the heat generation of the control unit 60 of the light deflector 10, the heat generation of the armature coil group 54, etc., and the base oil (for example, poly α olefin) contained in the lubricating oil, the additive ( For example, stearic acid) is pyrolyzed to produce sludge and carbon.
[0036]
In the hydropolymerization reaction, a lubricating oil (for example, ester series) reacts with moisture in the air and changes into a gel.
[0037]
In the oxidation of the base oil, the base oil is oxidized over time due to consumption of the antioxidant, and sludge is generated.
[0038]
Impurity contamination includes sludge generated by thermal degradation, carbon, abrasion powder due to mechanical contact between the sleeve member 32 and the rotating shaft 44, and dust entering from the outside.
[0039]
Next, formation of an oil film of deteriorated lubricating oil will be described. The oil film forming ability of the deteriorated lubricating oil is lowered, and the oil film forming surface is reduced because sludge, carbon, and dust are present in the oil film. By the disturbance of the fluid lubrication state due to repeated starting and stopping operations, the rotating shaft 44 and the sleeve member 32 (inner peripheral surface of the radial bearing portion 40) cause mechanical contact. Generally, the rotating shaft 44 is made of an iron-based alloy, and the sleeve member 32 is made of a copper-based alloy. Local heat generation due to mechanical contact decreases the viscosity of the lubricating oil and the ability to form an oil film, and causes thermal deterioration of the lubricating oil. Further, the abrasion powder generated by the mechanical contact reduces the oil film forming surface, damages the sleeve member 32 and the rotating shaft 44, and further reduces the oil film forming ability. During high-speed rotation, when a vibration and impact are applied from the outside, the viscous shear stress acting on the lubricating film locally increases, which is one of the major factors that degrade the lubricating oil. As a result, the sleeve member 32 and the rotary shaft 44 are galled and seized. In addition to the deterioration factors described above, the accumulation of lubricating oil containing sludge, carbon, wear powder, dust, etc. in the dynamic pressure generating groove also accelerates the time until the sleeve member 32 and the rotary shaft 44 are galled and seized. It is. If the dynamic pressure generating groove 38 having a groove depth of about several μm is clogged, the target dynamic pressure cannot be obtained, the shaft rigidity is lowered, and the vibration of the rotating body is increased. Depending on the configuration, half-wheel vibration may also occur. It is also weak against external vibrations and shocks.
[0040]
The effects of the deteriorated lubricating oil and sludge, carbon, wear powder and the like on the rotation of the rotating shaft 44 are removed by the optical deflecting device 10 of the present embodiment as follows.
[0041]
That is, by providing the groove 43 that circulates on the outer periphery of the sliding portion of the thrust bearing portion 42 formed of the sliding material, the wear powder generated at the opening portion of the hole portion 36 described above, dust entering from the outside, Precipitates such as lubricating oil that have deteriorated are directed downward in the thrust direction and reach the bottom of the hole 36 (thrust bearing portion 42). Further, the precipitate accumulates in a groove 43 formed in the thrust bearing portion 42. Therefore, the deposit interposed between the thrust bearing portion 42 and the end face 45 of the rotary shaft 44 is reduced, and the friction torque of the rotary shaft 44 generated by the viscosity of the deposit can be suppressed.
[0042]
Further, since the groove 43 is formed at a predetermined distance from a portion (hereinafter referred to as a sliding contact portion) 48 where the end surface 45 of the rotating shaft 44 is slidably contacted in the thrust bearing portion 42, the end surface 45 of the rotating shaft 44 is the groove. The rotating state is not affected by contact with the end portion of 43.
[0043]
In the present embodiment, the groove 43 is formed in the thrust bearing portion 42, but it may be formed in the end surface 45 of the rotating shaft 44.
[0044]
Next, an optical deflecting device according to a second embodiment of the present invention will be described. Since only the thrust bearing portion 42 is different from the first embodiment, only this portion will be described with reference to FIG. In addition, the same component as 1st Embodiment attaches | subjects the same referential mark, and abbreviate | omits the detailed description.
[0045]
A groove 80 formed in the thrust bearing portion 42 is formed in a spiral shape in the outer peripheral direction from a position separated from the sliding portion 48 by a predetermined distance. The groove 80 is curved toward the outer periphery in the rotational direction of the rotary shaft 44 (arrow A direction), and is a dynamic pressure generating groove that generates positive pressure as the rotary shaft 44 rotates. Become.
[0046]
Therefore, even if the above-mentioned deposits collect on the bottom surface of the hole 36 along the rotation shaft 44, they accumulate in the groove 80, so that the rotation of the rotation shaft 44 is sandwiched between the end surface 45 of the rotation shaft 44 and the thrust bearing portion 42. Hindering (generating wear torque) can be suppressed. In particular, since the groove 80 is curved from the center toward the outer periphery in the direction of rotation of the rotary shaft 44 (in the direction of arrow A), a flow toward the outer periphery is generated with the rotation of the rotary shaft 44, and the precipitate Can be collected in the outer circumferential direction.
[0047]
Subsequently, an optical deflecting device according to a third embodiment of the present invention will be described. The difference from the first embodiment is that the rotating shaft rotates horizontally and the sediment accumulation groove is formed in the radial bearing portion instead of the thrust bearing portion. Therefore, the radial bearing portion will be described, the same reference numerals are given to the same components as those in the first embodiment, and detailed description thereof will be omitted.
[0048]
As shown in FIG. 8, the optical deflection apparatus 10 according to the present embodiment has a printed circuit board 30 erected, and a motor 31 is disposed perpendicular thereto. Therefore, the rotating body 34 is rotated around the rotating shaft 44 installed in a horizontal state.
[0049]
On the inner peripheral surface of the radial bearing portion 40 (hole portion 36) of the sleeve member 32, as shown in FIG. 9, three dynamic pressure generating grooves 82A to 82C extending in the thrust direction have a predetermined interval in the circumferential direction. The rotary shaft 44 is supported in the radial direction. The depth of the dynamic pressure generating groove 82 is about several μm. The thrust bearing portion 42 is the same as in the first embodiment.
[0050]
In the optical deflecting device 10 configured as described above, the precipitate generated by the rotation of the rotating body 34 gathers downward in the hole 36 due to gravity, but the dynamic pressure generated substantially in the lower part in the direction of gravity. It is possible to suppress the accumulation in the grooves 82 </ b> A and 82 </ b> B and affecting the rotation state of the rotating shaft 44 (generating wear torque).
[0051]
The mechanism that supports the rotating shaft 44 in the thrust direction may be a magnetic bearing that is supported by the magnetic force between the drive magnet 52 and the armature coil group 54.
[0052]
Finally, an optical deflection apparatus according to the fourth embodiment of the present invention will be described. This embodiment is different from the third embodiment in that a herringbone-like dynamic pressure generating groove is provided on the inner peripheral surface of the radial bearing portion 40 of the optical deflector 10. Components similar to those in the third embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
[0053]
As shown in FIG. 10B, a herringbone-like dynamic pressure generating groove 38 is formed on the inner peripheral surface of the radial bearing portion 40, and an annular groove 84 is formed at the center thereof.
[0054]
With this configuration, the lubricating oil and the sediment flow into the annular groove 84 from the dynamic pressure generating groove 38 due to the rotation of the rotating shaft 44, and the sediment having a high specific gravity accumulates in the annular groove 84. Therefore, the influence of the precipitate on the rotation of the rotating shaft 44 can be minimized.
[0055]
【The invention's effect】
The optical deflecting device according to claim 1 is provided with three dynamic pressure generating grooves extending in the thrust direction on the inner peripheral surface of the radial bearing portion even when the rotating shaft rotates substantially horizontally, and is substantially lower in the gravity direction. The two dynamic pressure generating grooves are arranged on the rotating shaft, so that precipitates such as wear powder generated by sliding between the rotating shaft and the bearing member, dust entering from the outside, and lubricating oil deteriorated over time can be removed from the rotating shaft. By utilizing the rotation, it can be accumulated in the dynamic pressure generating groove arranged at the lower portion, and the friction torque of the rotating shaft can be suppressed. As a result, the life of the optical deflecting device can be provided longer and inexpensively.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an optical deflecting device according to a first embodiment of the present invention.
FIG. 2 is an exploded cross-sectional view of the optical deflection apparatus according to the first embodiment of the present invention.
FIG. 3 is a block diagram showing a control unit of the optical deflection apparatus according to the first embodiment of the present invention.
FIG. 4 is a diagram showing a rotating shaft and a thrust bearing of the optical deflection apparatus according to the first embodiment of the present invention.
FIG. 5 is a plan view showing a relationship between sliding portions and grooves in the thrust bearing according to the first embodiment of the present invention.
FIG. 6 is an explanatory diagram showing a flow of lubricating pressure and a dynamic pressure generating groove of the optical deflector according to the first embodiment of the present invention.
FIG. 7 is a plan view showing a relationship between a sliding portion and a groove in a thrust bearing of an optical deflecting device according to a second embodiment of the present invention.
FIG. 8 is a cross-sectional view of an optical deflecting device according to a third embodiment of the present invention.
FIG. 9 is a cross-sectional view of a radial bearing portion according to a third embodiment of the present invention.
10A is a cross-sectional view of an optical deflector according to a third embodiment of the present invention, and FIG. 10B is a cross-sectional view of a sleeve member.
FIG. 11 is an explanatory view showing the flow of the dynamic pressure generating groove and the lubricating oil of the optical deflector according to the first embodiment of the present invention.
FIG. 12 is a schematic view of a laser printer.
FIG. 13 is a plan view showing an optical scanning device in a laser printer.
FIG. 14 is a diagram illustrating a relationship between a rotary shaft, a thrust bearing, and accumulated sediment according to a conventional example.
FIG. 15 is a view showing a relationship between a rotary shaft and a thrust bearing according to a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Optical deflection apparatus 26 Rotating polygon mirror 32 Sleeve member (bearing member)
34 Rotating body 38 Dynamic pressure generating groove 40 Radial bearing portion 42 Thrust bearing portion 43 Groove (concave portion)
44 Rotating shaft 80 Groove (concave)
84 Groove (concave)

Claims (1)

A rotating body including a rotating shaft that supports the rotating polygon mirror;
A bearing member including a thrust bearing portion that supports the rotating shaft in a thrust direction, and a radial bearing portion that supports the rotating shaft in a radial direction;
Driving means for rotating the rotating body;
An optical deflector in which a gap between the rotary shaft and the bearing member is filled with lubricating oil, and the rotary shaft is disposed substantially horizontally and rotates.
3. An optical deflecting device comprising: three dynamic pressure generating grooves extending in a thrust direction on an inner peripheral surface of the radial bearing portion, and two dynamic pressure generating grooves arranged at a lower portion in a substantially gravity direction .

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