JP3676114B2 - Optical deflector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of an optical deflector used in apparatuses such as a laser printer, a copying apparatus, and a barcode reader.
[0002]
[Prior art]
Image forming apparatuses such as laser printers and copiers, and readers such as barcode readers use a polygon mirror (polyhedral mirror) as a means to reflect the light emitted from a light source such as a laser or LED and scan the reflected light. The used optical deflector is used. When a polygon mirror is used as a scanning device, continuous scanning at high speed is possible during image formation and data reading.
[0003]
For example, in an image forming apparatus such as a laser beam copying apparatus, an image of a document is read by a scanner unit, and an electrostatic latent image is formed by exposing the surface of a photosensitive member charged to a single polarity by image light based on the image data. Then, the toner image obtained by visualizing the electrostatic latent image is printed and fixed on a predetermined transfer sheet, and the printed sheet is discharged. In such an image forming apparatus, the optical deflector is used when irradiating the surface of the photoreceptor with image light for forming an electrostatic latent image.
[0004]
FIG. 9 is a schematic sectional view showing the structure of a conventional optical deflector. The optical deflector includes a polygon mirror 70, a rotor part 51, a stator part 52, and a bearing part 53. Further, the rotor unit 51, the stator unit 52, and the bearing unit 53 constitute a motor, and a DC brushless motor or the like is conventionally applied.
[0005]
The rotor unit 51 includes a rotor 73a, a magnet 74 provided inside the rotor 73a, a rotating shaft 71 that supports the rotor unit 51, and a polygon mirror 70 supported by the rotating shaft.
[0006]
The stator portion 52 includes a coil 75 provided around the bearing unit 72, a frame 78 that holds the bearing unit 72, and the like.
The bearing portion 53 includes a bearing unit 72 that holds a rotating shaft 71 of the rotor and incorporates a bearing, and a lubricant is applied to the bearing unit 72 in order to smoothly rotate.
[0007]
When an exciting current flows through the coil 75 by a control circuit (not shown), a magnetic field is generated, and an attractive force or a repulsive force is generated between the coil 74 and the rotor unit 51 rotates.
[0008]
10 and 11 are a top view and a side view showing a configuration example of a laser writing unit (LSU) using an optical deflector used in the image forming apparatus.
[0009]
The LSU is a laser irradiation unit 60, an optical deflector 69 having a polygon mirror 61, a first mirror 63 that changes the optical path of the laser light reflected by the polygon mirror 61, a second mirror 64, and a laser beam reflected by the polygon mirror 61. The first f-θ lens 62 and the second f-θ lens 65 that perform f-θ correction are configured.
[0010]
The light emitted from the laser irradiation unit 60 is reflected by the polygon mirror 61 that rotates in the arrow direction (main scanning direction) in FIG. The reflected light is reflected by the first mirror 63 and the second mirror 64 via the first f-θ lens 62, changes the optical path, and is guided to the photosensitive drum 28 via the second f-θ lens 65.
[0011]
The printing resolution of image forming apparatuses such as recent laser beam copying apparatuses and laser printers has been dramatically improved, and accordingly, the motor of the optical deflector is required to rotate at a higher speed. For example, when printing at a resolution of 600 dpi, the image writing width H per line (one dot) is 1 inch = 25.4 mm.
H = 25.4 (mm) / 600 (dpi) = 42.3 (μm / line)
It becomes. In this case, if the image forming speed in the sub-scanning direction is 180 mm / second, the number N of lines written on the photosensitive drum 28 per second is
N = 180 (mm / sec) /42.3 (μm / line ) = 4.2 × 10 ³ (line / sec)
It becomes. Therefore, the number of revolutions M per minute in the motor of the optical deflector including the polygon mirror having six reflecting surfaces is
M = 4.2 × 10 ³ (line / second) / 6 (surface) = 42000 (RPM)
It is.
[0012]
As described above, the motor of the optical deflector in the high-resolution image forming apparatus rotates at high speed. In FIG. 9, the lubrication in the bearing unit 72 is caused by the frictional heat between the rotating shaft 71 and the bearing in the bearing unit 72. The fluidity of the agent is increased, and the lubricant leaks from the gap between the seal members (not shown) provided at the upper part of the bearing unit 72. Then, as indicated by an arrow B in FIG. 9, the air flow generated by the rotation of the rotor unit 51 is scattered from the upper part of the bearing unit 72 toward the outside. Further, the lubricant that leaks out and adheres to the rotor 73a is scattered toward the outside by centrifugal force when the rotor 73a rotates. The scattered lubricant adheres to the surface of the polygon mirror 70 and the lens and mirror in the optical path, and the surface is soiled. Therefore, the conventional image processing apparatus incorporating the optical deflector has a problem that the image deteriorates.
[0013]
As a configuration for solving this problem, Japanese Patent Application Laid-Open No. 62-94814 discloses a configuration in which an oil scattering prevention function is provided in a motor that drives a polygon mirror to prevent deterioration in image quality.
[0014]
[Problems to be solved by the invention]
However, when used in an image processing apparatus that performs high-speed rotation as described above, the configuration of the apparatus disclosed in Japanese Patent Application Laid-Open No. 62-94814 is a labyrinth mechanism, but has a gap structure. Therefore, the lubricant may leak from the gap. In particular, the amount of frictional heat generated during high-speed rotation is large, and the lubricant is likely to flow due to the frictional heat, so that the lubricant easily leaks from the gap.
[0015]
An object of the present invention is to provide an optical deflector having a structure capable of reliably preventing leakage of a lubricant even when driven at high speed rotation.
[0016]
[Means for Solving the Problems]
The present invention has the following configuration as means for solving the above problems.
[0017]
(1) a flat frame,
Is erected on the frame, a rotor exhibiting a bearing portion for supporting the rotary shaft, a stator portion disposed around the shaft receiving portion, said being supported by the rotary shaft, concave shape opening surface is opposed to the frame a is a motor having a low data formed along the outer periphery of the bearing portion and the stator portion,
A wall that surrounds the outer periphery of the rotor and is provided with a space for ventilation between the frame and the frame;
On the frame, a lubricant absorbing member erected around the wall;
It is supported by the rotary shaft, and a rotating polygon mirror the row data and both
With
Characterized in that the formation of the thread-shaped groove of the rotating direction and the forward direction of the row data to the outer peripheral portion of the row data.
[0018]
In this configuration, a bearing portion lubricant is applied, the lubricant absorbing member faces over the entire circumference, the screw groove of the rotational direction of the row data and forward is formed on the outer periphery of the rotor, the frame a wall provided with a space for ventilation between the outer peripheral portion of the row data is enclosed. Therefore, when the motor rotates at high speed, by a screw-shaped groove formed on the outer periphery of the rotor, the air flow is generated in the direction toward the frame from the rotor between the outer peripheral portion and the wall of the rotor, leaked The lubricant is not scattered by the polygon mirror but is absorbed by the absorbing member and does not contaminate the polygon mirror.
[0027]
(2) an optical system that reflects light reflected from said polygon mirror, a height from the frame, characterized in that arranged to direct the reflected light to be a high position Ri by the polygon mirror.
[0028]
In this configuration, the optical system that reflects the reflected light from the polygon mirror is arranged so that the reflected light is guided to a position where the height from the frame is higher than that of the polygon mirror . Therefore, when the motor rotates at a high speed, the lubricant applied to the bearing part leaks with increased fluidity due to frictional heat, and even if it is scattered toward the periphery of the optical deflector, it becomes a means for forming an optical path. It will not adhere.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a sectional view of an optical deflector according to a first embodiment of the present invention. The optical deflector includes a polygon mirror 70 and a motor including a stator portion, a rotor portion, and a bearing portion.
[0030]
The rotor portion includes a rotor 73a, a magnet 74 provided inside the rotor portion, a rotating shaft 71 that supports the rotor portion, and a polygon mirror 70 supported by the rotating shaft.
[0031]
The stator portion is constituted by a coil 75 provided around the bearing unit 72 and is installed on the frame 78. Further, a belt-like lubricant absorbing member 76a having one end (lower end) in contact with the upper surface of the frame 78 and the other end (upper end) being an open end is disposed around the rotor portion, and the outer periphery of the absorbing member 76a. An oil fence 77a is disposed on the wall. The upper end of the oil fence 77a is an open end similarly to the absorbing member 76a, and the lower end is joined to the frame 78.
[0032]
The bearing portion includes a bearing unit 72 that holds a rotating shaft 71 of the rotor and incorporates a bearing, and a lubricant is applied to the bearing unit 72 in order to smoothly rotate.
[0033]
When an excitation current flows through the coil 75 by a control circuit (not shown), a magnetic field is generated, and an attractive force or a repulsive force is generated between the coil 74 and the rotor portion rotates. When the rotor portion rotates at a high speed, the fluidity of the lubricant increases, leaks from the bearing unit 72, adheres to the rotor 73a, and scatters toward the periphery due to centrifugal force. Further, as shown by an arrow B in FIG. 1, the air flow generated by the rotation of the rotor portion scatters outward from the bearing unit 72. The scattered lubricant adheres to the absorbing member 76a and is absorbed. Further, the end surface of the absorbing member 76a is in contact with the frame 78, since the lower end of the boom 77a is bonded to the frame 78, the lubricant or splash to the outside from the oil fence 77a, no or outflow. That is, with this structure, the lubricant is not scattered outside the optical deflector.
[0034]
In addition, as a material of the absorbing member, Japanese paper suitable for absorbing the lubricant or foamed member such as urethane can be used, but a member suitable for absorbing the other lubricant is used. Also good.
[0035]
FIG. 2 is a sectional view of an optical deflector according to the second embodiment of the present invention. Since this optical deflector is obtained by making the absorbing member 76a and the oil fence 77a of the optical deflector according to the embodiment shown in FIG. 1 into different shapes, only different parts will be described.
[0036]
In FIG. 2, it is set as the structure which bent a part of the open end side of the absorption member 76b and the oil fence 77b to the rotor side.
[0037]
As shown in FIG. 2, the gap between the absorbing member 76 b and the oil fence 77 b on the open end side is bent toward the rotor side so that the gap with the rotor 73 a can be made small. Further, as shown by an arrow B in FIG. 2 due to the air flow generated by the rotation of the rotor portion, the air is scattered outward from the bearing unit 72. However, since the air flow moves along the absorbing member 76b, it is absorbed by the absorbing member 76b. In addition, since the gap between the open end side of the absorbing member 76b and the oil fence 77b and the rotor 73a is small, scattering to the outside of the motor can be prevented.
[0038]
FIG. 3B is a cross-sectional view of a conventional optical deflector. Since it is the same as that of FIG. 9, description of a structure etc. is omitted. In FIG. 3B, the outer periphery of the rotor 73a and the outer periphery (mirror surface) of the polygon mirror 70 have the same diameter. In this case, when the motor rotates at a high speed, the outer peripheral portion of the polygon mirror may become a negative pressure region. In this case, the scattered lubricant is attracted to the negative pressure region, and the mirror surface of the polygon mirror 70 is soiled.
[0039]
FIG. 3A is a cross-sectional view of an optical deflector according to the third embodiment of the present invention. 3A, since the diameter of the rotor 73b is larger than the diameter of the polygon mirror 70, the outer peripheral portion (mirror surface) of the polygon mirror 70 is located inside the outer peripheral portion of the rotor 73b. In this configuration, even if the outer peripheral portion of the polygon mirror 70 becomes a negative pressure region, the gap between the rotor 73b and the absorbing member 76a is located outside the negative pressure region of the outer peripheral portion of the polygon mirror 70. Even if it scatters, it adheres to the absorbing member 76a and is absorbed, and even if the lubricant scatters from the gap, the polygon mirror 70 is not soiled for the above reasons.
[0040]
FIG. 4 is a sectional view of an optical deflector according to the fourth embodiment of the present invention. Since this optical deflector is obtained by making the rotor 73a of the optical deflector according to the embodiment shown in FIG. 1 into another shape, only different parts will be described. In FIG. 4, the rotor 73c has a frustoconical shape and is formed so that its diameter gradually increases from the polygon mirror side (upper part) to the stator side (lower part). When the motor rotates at a high speed, the pressure at the surface of the point f is lower than the pressure at the surface of the point e because the rotational speed of the point f is faster than that of the point e. Therefore, an air flow is generated in the direction from point e to point f. Due to this air flow, the scattered lubricant is sent to the absorbing member 76a, and thus is prevented from adhering to the polygon mirror.
[0041]
FIG. 5 is a sectional view of an optical deflector according to a fifth embodiment of the present invention. In this optical deflector, the rotor 73a of the optical deflector according to the embodiment shown in FIG. 1 is replaced with another shape 73d, and a wall 81 is provided between the rotor 73d and the absorbing member 76a. Only the differences will be described. A screw-like groove is formed in the rotation direction on the outer periphery of the rotor 73d. In addition, a wall 81 provided with a space that can be ventilated at the frame side end portion between the rotor 73d and the absorbing member 76a is provided. With this configuration, when the motor rotates at a high speed, a downward air flow is generated between the outer side of the rotor 73d and the inner side of the wall 81 by a screw-like groove formed on the outer periphery of the rotor 73d. Due to this air flow, the scattered lubricant is sent to the absorbing member 76a, and thus is prevented from adhering to the polygon mirror.
[0042]
FIG. 6 is a side view of an optical deflector according to the sixth embodiment of the present invention. The optical deflector provided with the polygon mirror 61 reflects a light beam emitted from a laser irradiation unit (not shown), and forms an electrostatic latent image on the photosensitive drum 28 via the first f-θ lens 62 and the second f-θ lens 65. Form. The first f-θ lens 62 and the second f-θ lens 65, which are optical system components, are arranged at a position higher than the rotor 66.
[0043]
In this structure, since the optical system component is disposed at a position higher than the rotor 66, even if the motor rotates at high speed and the lubricant scatters, it does not adhere to the first f-θ lens 62 and the second f-θ lens 65. .
[0044]
FIG. 7 is a side view of another embodiment of the optical deflector according to the sixth embodiment of the present invention. An optical deflector provided with a polygon mirror 61 reflects a light beam emitted from a laser irradiation unit (not shown) and reflects the light beam by the first mirror 63 and the second mirror 64 via the first f-θ lens 62 to change the optical path. An electrostatic latent image is formed on the photosensitive drum via the second f-θ lens 65. Also in FIG. 7, the first f-θ lens 62, the mirror 63, the mirror 64, and the second f-θ lens 65 are arranged at a position higher than the rotor 66 as in FIG. 6. Does not adhere to the first f-θ lens 62, the mirror 63, the mirror 64, and the second f-θ lens 65.
[0045]
6 and 7, since the lubricant does not scatter in the optical system parts, the light deflector 69 need not include the absorbing member and the oil fence. However, even in the optical deflector having such a configuration, if the configuration shown in FIGS. 1 to 5 can prevent the scattering of the lubricant, the performance of the apparatus incorporating the optical deflector is further improved.
[0046]
FIG. 8 shows an image forming apparatus employing the optical deflector of the present invention as the image forming apparatus. The image forming apparatus includes a scanner unit A, a printing unit B, and a conveyance unit C that conveys printing paper.
[0047]
The scanner unit A includes a document table 7 made of transparent glass and the like, and a scanner optical system unit. The scanner optical system unit includes an exposure lamp 11, reflecting mirrors 12-1, 12-2 and 12-3, an imaging lens 13, and a photoelectric conversion element (CCD) 14.
[0048]
The light emitted from the exposure lamp 11 scans the document placed on the upper surface of the document table 7. The reflected light of the document is guided to the imaging lens 13 and the CCD 14 by the reflecting mirrors 12-1, 12-2, 12-3. The CCD 14 receives the reflected light imaged by the imaging lens 13 and generates image data of an electrical signal corresponding to the reflected light.
[0049]
The printing unit B includes a photosensitive drum 28, a charging unit 29, a developing unit 30, a transfer charger 31, a fixing roller 23, a cleaning device 32, and a laser writing unit (LSU) 51.
[0050]
The drum-shaped photosensitive drum 28 is rotationally driven in the direction of arrow a, and the charging unit 29 uniformly charges the surface of the photosensitive drum 28 to a predetermined potential. The LSU 51 forms an electrostatic latent image corresponding to the image data generated by the scanner unit A on the surface of the photosensitive drum 28 by exposing the charged surface of the photosensitive drum 28 with laser light. The developing unit 30 forms a toner image on the photosensitive drum 28 by developing the electrostatic latent image formed by the LSU 51 with the developing roller 30a. The transfer charger 31 transfers the toner image on the photosensitive drum 28 to a sheet. The fixing roller 23 heat-fixes the unfixed toner image transferred to the sheet on the sheet. The cleaning device 32 removes the toner remaining on the surface of the photosensitive drum 28 after the toner image is transferred to the sheet . The paper conveyance unit C includes a main transport path L, the fixed sheet cassette 15, a pickup roller 18, registration rollers 22, sheet discharge port R and the discharge roller 25, and a pre-registration detection switch (not shown).
[0051]
The fixed paper feed cassette 15 is for storing sheets P for printing.
The pickup roller 18 is a half-moon roller for feeding sheets P one by one from the fixed sheet feeding cassette 15 and feeding them to the main conveyance path L. The pre-registration detection switch is for detecting that the sheet P conveyed by the pickup roller 18 has passed a predetermined position on the main conveyance path L and outputting a predetermined detection signal.
The registration roller 22 temporarily holds the sheet P that has been transported along the main transport path L. The sheet P is transported to the transfer charger 31 in a timely manner in accordance with the rotation of the photosensitive drum 28 so that the toner image on the photosensitive drum 28 can be satisfactorily transferred to the sheet P. That is, the registration roller 22 conveys the sheet P so that the leading edge of the toner image on the photosensitive drum 28 is pressed against the leading edge of the printing range on the sheet P based on the detection signal output by the pre-registration detection switch. It has become. The paper discharge roller 25 is provided near the paper discharge port R, and is a roller for discharging the sheet P outputted from the fixing roller 23 to a paper discharge tray (not shown). Moreover, in order to control each part, it has a control part outside a figure.
[0052]
Although the present invention has been described as having a bearing ball as a bearing, the present invention is not limited to this mechanism. For example, the bearing ball is not provided like an oil dynamic pressure bearing, but oil is used as a bearing. The present invention can be applied to an optical deflector having other mechanisms such as a provided bearing.
[0053]
【The invention's effect】
According to the present invention, a bearing portion lubricant is applied lubricant absorbing member and are opposed over the entire circumference, forming a screw groove to the direction of rotation of the row data and forward the outer periphery of the rotor, the frame with a space for ventilation on the wall provided between, by surrounding the outer peripheral portion of the row data, when the motor rotates at high speed, by a screw-shaped groove formed on the outer periphery of the rotor, and low motor and the wall During this time, an air flow is generated in the direction from the rotor to the frame, and the leaked lubricant does not scatter to the polygon mirror, but is absorbed by the absorbing member and does not contaminate the polygon mirror.
[0059]
According to the present invention, when the optical system that reflects the reflected light from the polygon mirror is arranged so that the reflected light is guided to a position where the height from the frame is higher than that of the polygon mirror , the motor rotates at high speed. In addition, the lubricant applied to the bearing portion leaks with increased fluidity due to frictional heat, and does not adhere to the means for forming the optical path even if scattered toward the periphery of the optical deflector.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an optical deflector according to a first embodiment of the present invention.
FIG. 2 is a schematic sectional view of an optical deflector according to a second embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view of an optical deflector according to a third embodiment of the present invention.
FIG. 4 is a schematic sectional view of an optical deflector according to a fourth embodiment of the present invention.
FIG. 5 is a schematic sectional view of an optical deflector according to a fifth embodiment of the present invention.
FIG. 6 is a schematic side view of an optical deflector according to a sixth embodiment of the present invention.
FIG. 7 is a schematic side view of another embodiment of the optical deflector according to the sixth embodiment of the present invention;
FIG. 8 is a side view of an image forming apparatus employing the optical deflector according to the present invention.
FIG. 9 is a schematic cross-sectional view showing the structure of a conventional optical deflector.
FIG. 10 is a top view showing a configuration example of a laser writing unit (LSU) using an optical deflector used in a conventional image forming apparatus.
FIG. 11 is a side view showing a configuration example of a laser writing unit (LSU) using an optical deflector used in a conventional image forming apparatus.
[Explanation of symbols]
28-photosensitive drum 51-rotor part 52-stator part 53-bearing part 60-laser irradiation part 61, 70-polygon mirror 62-first f-theta lens 63-first mirror 64-second mirror 65-second f- θ lenses 66, 73a, 73b, 73c, 73d-rotor 69-light deflector 71-rotating shaft 72-bearing unit 74-magnet 75-coils 76a, 76b-absorbing members 77a, 77b-oil fence 78-frame 81-wall

Claims (2)

A flat frame,
Is erected on the frame, a rotor exhibiting a bearing portion for supporting the rotary shaft, a stator portion disposed around the shaft receiving portion, said being supported by the rotary shaft, concave shape opening surface is opposed to the frame a is a motor having a low data formed along the outer periphery of the bearing portion and the stator portion,
A wall that surrounds the outer periphery of the rotor and is provided with a space for ventilation between the frame and the frame;
On the frame, a lubricant absorbing member erected around the wall;
It is supported by the rotary shaft, and a rotating polygon mirror the row data and both
With
Optical deflector, characterized in that the formation of the thread-shaped grooves and the rotating direction forward of the row data to the outer peripheral portion of the row data. 2. The light according to claim 1, wherein an optical system that reflects the reflected light from the polygon mirror is arranged so as to guide the reflected light to a position where a height from the frame is higher than that of the polygon mirror. Deflector.

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