This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-153405 filed on Aug. 17, 2018, the entire contents of which are incorporated herein by reference.
The technology of the present disclosure relates to a light deflecting device, an optical scanning device and an image forming apparatus.
In general, a light deflecting device, is provided in an image forming apparatus, for example. The light deflecting device includes a rotary polyhedron and a cover that covers the rotary polyhedron, and the cover is formed with an opening facing a peripheral surface of the rotary polyhedron. Light emitted from a light source is irradiated to the peripheral surface of the rotary polyhedron through the opening of the cover, and the rotary polyhedron allows the light to be deflected and scanned with respect to an image carrying member as an object to be irradiated through the opening while rotating about an axial center thereof. In this way, an electrostatic latent image is formed on a surface of the image carrying member.
Since the cover of this type of light deflecting device is a non-sealed type cover formed with the opening, noise generated by the rotation of the rotary polyhedron leaks out of the cover from the opening. In this regard, in the related art, the noise is reduced by forming the opening as small as possible.
A light deflecting device of an aspect of the present disclosure includes a rotary polyhedron and a cover that covers the rotary polyhedron. The cover includes an opening facing a peripheral surface of the rotary polyhedron. Light beam emitted from a light source is irradiated to the peripheral surface of the rotary polyhedron through the opening of the cover. The rotary polyhedron allows the light beam to be deflected and scanned with respect to an object to be irradiated through the opening while rotating about an axial center thereof.
In the light deflecting device, when an opening angle of the opening centered on the axial center of the rotary polyhedron is θ and n is set as a natural number smaller than a number of surfaces of the rotary polyhedron, θ satisfies Equation (1) θ>((360°/the number of surfaces of the rotary polyhedron)×n)×0.83 . . . (1) and Equation (2) θ<((360°/the number of surfaces of the rotary polyhedron)×n)×1.17 . . . (2).
A light deflecting device of another aspect of the present disclosure includes a rotary polyhedron and a cover that covers the rotary polyhedron. The cover includes an opening facing a peripheral surface of the rotary polyhedron. Light beam emitted from a light source is irradiated to the peripheral surface of the rotary polyhedron through the opening of the cover. The rotary polyhedron allows the light beam to be deflected and scanned with respect to an object to be irradiated through the opening while rotating about an axial center thereof.
In the light deflecting device, when an opening angle of the opening centered on the axial center of the rotary polyhedron is θ and n is set as a natural number smaller than a number of surfaces of the rotary polyhedron, θ satisfies Equation (3) θ≈(360°/the number of surfaces of the polygon mirror 63)×n.
An optical scanning device of another aspect of the present disclosure includes the light deflecting device and the light source.
An image forming apparatus of another aspect of the present disclosure includes the optical scanning device and the object to be irradiated. The object to be irradiated is a an image carrying member having a surface on which an electrostatic latent image is formed.
Hereinafter, an example of an embodiment will be described on the basis of the drawings.
[Structure of Image Forming Apparatus 1]
The body housing 10 receives a plurality of processing units for performing image forming processing on a sheet therein. In the present embodiment, the processing units include image forming units 2Y, 2C, 2M, and 2Bk, an optical scanning device 23, an intermediate transfer unit 28, and a fixing device 30.
The body housing 10 is provided on the upper surface thereof with a sheet discharge tray 11. A sheet discharge port 12 is opened in opposition to the sheet discharge tray 11. A manual sheet feeding tray 13 is attached to a sidewall of the body housing 10 so as to be freely openable and closable. A sheet feeing cassette 14 is detachably mounted at a lower part of the body housing 10.
The image forming units 2Y, 2C, 2M, and 2Bk form toner images of yellow (Y), cyan (C), magenta (M), and black (Bk) on the basis of image information transmitted from an external device. The image forming units 2Y, 2C, 2M, and 2Bk are arranged in tandem at predetermined intervals in a horizontal direction.
Each of the image forming units 2Y, 2C, 2M, and 2Bk includes the following parts and devices, that is, a cylindrical body-shaped photosensitive drum 21 (corresponding to an image carrying member and an object to be irradiated) for carrying an electrostatic latent image and a toner image, a charging unit 22 for charging a drum peripheral surface of the photosensitive drum 21, a developing device 24 for forming the toner image by attaching a developer to the electrostatic latent image, a primary transfer roller 26 for primarily transferring the toner image formed on the photosensitive drum 21, and a cleaning device 27 for removing residual toner on the drum peripheral surface of the photosensitive drum 21, and the image forming units 2Y, 2C, 2M, and 2Bk include toner containers 25Y, 25C, 25M, and 25Bk of yellow, cyan, magenta, and black for supplying toner of each color to the developing device 24, respectively.
In the following description, when the photosensitive drum 21 provided in each of the image forming units 2Y, 2C, 2M, and 2Bk is particularly described, the photosensitive drum provided in the image forming unit 2Y is referred to as a “first photosensitive drum 21Y”. Furthermore, the photosensitive drum provided in the image forming unit 2C is referred to as a “second photosensitive drum 21C”. The photosensitive drum provided in the image forming unit 2M is referred to as a “third photosensitive drum 21M”, and the photosensitive drum provided in the image forming unit 2Bk is referred to as a “fourth photosensitive drum 21Bk”.
The optical scanning device 23 forms the electrostatic latent image on the drum peripheral surface of the photosensitive drum 21 of each color. The optical scanning device 23 includes an incident optical system having a plurality of light sources prepared for each color, a light deflecting device 6 (see
The intermediate transfer unit 28 primarily transfers the toner image formed on the photosensitive drum 21. The intermediate transfer unit 28 includes a transfer belt 281 that rotates in contact with the drum peripheral surface of each photosensitive drum 21, and a driving roller 282 and a driven roller 283 over which the transfer belt 281 is stretched. The transfer belt 281 is pressed to the drum peripheral surface of each photosensitive drum 21 by the primary transfer roller 26. The toner image on the photosensitive drum 21 of each color is superimposed on the same place of the transfer belt 281 and is primarily transferred. In this way, a full-color toner image is formed on the transfer belt 281.
A secondary transfer roller 29 is arranged to face the driving roller 282 and forms a secondary transfer nip part T with the transfer belt 281 interposed therebetween. The full-color toner image of the transfer belt 281 is secondarily transferred to a sheet at the secondary transfer nip part T. Toner remaining on the peripheral surface of the transfer belt 281 is collected by a belt cleaning device 284 arranged to face the driven roller 283.
The fixing device 30 includes a fixing roller 31 having a heat source incorporated therein and a pressure roller 32 that forms a fixing nip part N together with the fixing roller 31. The fixing device 30 heats and presses the sheet, on which the toner image has been transferred at the secondary transfer nip part T, at the fixing nip part N, thereby allowing toner to be welded to the sheet. The sheet subjected to the fixing process is discharged from the sheet discharge port 12 to the sheet discharge tray 11.
The body housing 10 is provided therein with the sheet conveyance path for conveying a sheet. The sheet conveyance path includes a main conveyance path P1 extending in a vertical direction through the secondary transfer nip part T and the fixing device 30 from the vicinity of a lower part of the body housing 10 to the vicinity of an upper part thereof. A downstream end of the main conveyance path P1 is connected to the sheet discharge port 12. A reverse conveyance path P2 for conveying a sheet in a reverse direction during duplex printing extends from the lowermost stream end to the vicinity of an upstream end of the main conveyance path P1. Furthermore, a manual sheet conveyance path P3 from the manual sheet feeding tray 13 to the main conveyance path P1 is arranged above the sheet feeing cassette 14.
The sheet feeing cassette 14 receives a bundle of sheets. On the rear upper side of the sheet feeing cassette 14, a pick-up roller 151 for delivering sheets of the uppermost layer of the bundle of the sheets one by one and a sheet feeding roller pair 152 for sending the sheets to the upstream end of the main conveyance path P1 are provided.
Sheets placed on the manual sheet feeding tray 13 are sent to the upstream end of the main conveyance path P1 through the manual sheet conveyance path P3. On an upstream side from the secondary transfer nip part T of the main conveyance path P1, a resist roller pair 153 is arranged to send the sheets to the transfer nip part.
When the sheet is subjected to one side printing (image formation), the sheet is sent to the main conveyance path P1 from the sheet feeing cassette 14 or the manual sheet feeding tray 13. Then, the toner image is transferred to the sheet at the secondary transfer nip part T. Furthermore, toner is fixed to the sheet by the fixing device 30. The sheet with the toner fixed thereto is discharged from the sheet discharge port 12 to the sheet discharge tray 11.
When the sheet is subjected to duplex printing, the aforementioned transfer process and fixing process are performed on one side of the sheet and then the sheet is subjected to switchback conveyance. Then, the sheet is returned to the vicinity of the upstream end of the main conveyance path P1 through the reverse conveyance path P2. Thereafter, the transfer process and the fixing process are performed on the other side of the sheet. The sheet subjected to the fixing process is discharged from the sheet discharge port 12 to the sheet discharge tray 11.
[Structure of Optical Scanning Device 23]
Next, the optical scanning device 23 will be described in detail. In the following description, with reference to
The optical scanning device 23 is horizontally arranged below the image forming units 2Y, 2C, 2M, and 2Bk and the intermediate transfer unit 28. In the optical scanning device 23, the second direction A2 coincides with the vertical direction. The third direction A3 coincides with a front and rear direction corresponding to the movement direction of the transfer belt 281 that rotates, and the fourth direction A4 coincides with a right and left direction corresponding to a rotation axis direction (axial center direction) of the photosensitive drum 21.
The first direction A1 is a direction intersecting with the third direction A3 and the fourth direction A4 at an approximately 45°. In the second direction A2 coinciding with the vertical direction, an upper side in the vertical direction is referred to as “one side” and a lower side in the vertical direction is referred to as “the other side”.
In the third direction A3 coinciding with the front and rear direction, a front side in the front and rear direction is referred to as “one side” and a rear side in the front and rear direction is referred to as “the other side”. In the fourth direction A4 coinciding with the right and left direction, a right side in the right and left direction is referred to as “one side” and a left side in the right and left direction is referred to as “the other side”.
As illustrated in
The yellow light beam LY is laser light beam for yellow image drawing and the cyan light beam LC is laser light beam for cyan image drawing. The magenta light beam LM is laser light beam for magenta image drawing and the black light beam LBk is laser light beam for black image drawing.
As illustrated in
The reflective mirrors 73Y1 and 73Y2 for yellow reflect the yellow light beam LY, and the reflective mirrors 73C1 and 73C2 for cyan reflect the cyan light beam LC. The reflective mirrors 73M1, 73M2 and 73M3 for magenta reflect the magenta light beam LM, and the reflective mirror 73Bk for black reflects the black light beam LBk.
The first scanning lens 71, the second scanning lenses 72Y, 72C, 72M, and 72Bk, the reflective mirrors 73Y1 and 73Y2 for yellow, the reflective mirrors 73C1 and 73C2 for cyan, the reflective mirrors 73M1, 73M2 and 73M3 for magenta, and the reflective mirror 73Bk for black constitute an image forming optical system.
The optical housing 4 has a light deflecting device receiving part 41 (see
The incident optical system 5 is received in the optical housing 4 and is an optical system for allowing each color light beam to be incident on a deflection surface 631 which is a peripheral surface of a polygon mirror 63 (corresponding to a rotary polyhedron) to be described below. As illustrated in
The light source 51 is composed of a laser element and emits light beam to be irradiated to the deflection surface 631 of the polygon mirror 63. The collimator lens 52 converts the light beam diffused after being emitted from the light source 51 into parallel light. The cylindrical lens 53 converts the parallel light from the collimator lens 52 into linear light long in the fourth direction A4 and forms an image of the linear light on the deflection surface 631 of the polygon mirror 63.
As described above, the fourth direction A4 is a direction coinciding with the right and left direction corresponding to the rotation axis direction of the photosensitive drum 21 and coincides with the main scanning direction of scanning with respect to the photosensitive drum 21 by the optical scanning device 23.
The first scanning lens 71 is a lens having distortion aberration (fθ characteristic) in which an angle of incident light beam is proportional to an image height and is a long lens extending along the fourth direction A4 (main scanning direction). The first scanning lens 71 collects light beam reflected by the deflection surface 631 of the polygon mirror 63.
Similarly to the first scanning lens 71, the second scanning lens 72Y is a lens having the distortion aberration (fθ characteristic) and is a long lens extending along the fourth direction A4 (main scanning direction). The second scanning lenses 72Y collects the yellow light beam LY having passed through the first scanning lens 71 and forms an image of the yellow light beam LY on the drum peripheral surfaces 211 of the first photosensitive drum 21Y.
Similarly to the first scanning lens 71, the second scanning lens 72C is a lens having the distortion aberration (fθ characteristic) and is a long lens extending along the fourth direction A4 (main scanning direction). The second scanning lenses 72C collects the cyan light beam LC having passed through the first scanning lens 71 and forms an image of the cyan light beam LC on the drum peripheral surfaces 211 of the second photosensitive drum 21C.
Similarly to the first scanning lens 71, the second scanning lens 72M is a lens having the distortion aberration (fθ characteristic) and is a long lens extending along the fourth direction A4 (main scanning direction). The second scanning lenses 72M collects the magenta light beam LM having passed through the first scanning lens 71 and forms an image of the magenta light beam LM on the drum peripheral surfaces 211 of the third photosensitive drum 21M.
Similarly to the first scanning lens 71, the second scanning lens 72Bk is a lens having the distortion aberration (fθ characteristic) and is a long lens extending along the fourth direction A4 (main scanning direction). The second scanning lenses 72Bk collects the black light beam LBk having passed through the first scanning lens 71 and forms an image of the black light beam LBk on the drum peripheral surfaces 211 of the fourth photosensitive drum 21Bk.
The reflective mirrors 73Y1 and 73Y2 for yellow reflect the yellow light beam LY on the image forming optical path of the yellow light beam LY having passed through the first scanning lens 71.
The reflective mirrors 73C1 and 73C2 for cyan reflect the cyan light beam LC on the image forming optical path of the cyan light beam LC having passed through the first scanning lens 71.
The reflective mirrors 73M1, 73M2 and 73M3 for magenta reflect the magenta light beam LM on the image forming optical path of the magenta light beam LM having passed through the first scanning lens 71.
As illustrated in
The cyan light beam LC reflected by the deflection surface 631 of the polygon mirror 63 is collected by the first scanning lens 71. Then, the cyan light beam LC is reflected by the reflective mirror 73C1 for cyan and passes through the second scanning lens 72C. Thereafter, the cyan light beam LC is reflected by the reflective mirror 73C2 for cyan and the image of the cyan light beam LC is formed on the drum peripheral surfaces 211 of the second photosensitive drum 21C.
The magenta light beam LM reflected by the deflection surface 631 of the polygon mirror 63 is collected by the first scanning lens 71. Then, the magenta light beam LM is reflected by the reflective mirrors 73M1 and 73M2 for magenta and passes through the second scanning lens 72M. Thereafter, the magenta light beam LM is reflected by the reflective mirror 73M3 for magenta and the image of the magenta light beam LM is formed on the drum peripheral surfaces 211 of the third photosensitive drum 21M.
The black light beam LBk reflected by the deflection surface 631 of the polygon mirror 63 is collected by the first scanning lens 71 and the second scanning lens Bk. Thereafter, the black light beam LBk is reflected by the reflective mirror 73Bk for black and the image of the black light beam LBk is formed on the drum peripheral surfaces 211 of the fourth photosensitive drum 21Bk.
<Structure of Light Deflecting Device 6>
As illustrated in
[Structure of Board 61]
As illustrated in
[Structure of Driving Motor 62]
As illustrated in
[Structure of Polygon Mirror 63]
As illustrated in
[Structure of Cover Body 65]
As illustrated in
[Structure of First Cover Part 651]
As illustrated in
The peripheral wall 651B is formed with a first opening 651C (corresponding to an opening) facing the deflection surface 631 of the polygon mirror 63. As illustrated in
As illustrated in
[Structure of Second Cover Part 652]
The second cover part 652 forms a second space S2 (see
[Structure of First Extending Part 653]
As illustrated in
[Structure of Second Extending Part 654]
As illustrated in
As illustrated in
As illustrated in
Furthermore, as illustrated in
[Pressure Variation in Air in First Cover Part 651]
When the polygon mirror 63 rotates, air in the first cover part 651 is pushed in the rotation direction by a corner of the polygon mirror 63. Then, the air in the first cover part 651 is blown out from a first gap K1 (see
Since the peripheral wall 651B of the first cover part 651 has a circular section and the polygon mirror 63 has a regular hexagonal section, the first gap K1 and the second gap K2 change depending on the rotation of the polygon mirror 63.
Accordingly, first pressure of the air (air in the first gap K1) between the deflection surface 631 of the polygon mirror 63 and the first opening end A of the first opening 651C varies periodically with the rotation of the polygon mirror 63 (see
[Noise Prevention Structure of Light Deflecting Device 6]
Since the first opening 651C is formed in the peripheral wall 651B of the first cover part 651 that covers the polygon mirror 63, noise generated by the rotation of the polygon mirror 63 is leaked out of the first opening 651C to the outside of the first cover part 651. In this regard, in the present embodiment, the first opening 651C of the first cover part 651 is formed as follows, so that noise is reduced.
As illustrated in
θ≈(360°/the number of surfaces of the polygon mirror 63)×n (3)
In the present embodiment,
[A] Since the first opening 651C is formed such that the opening angle θ satisfies Equation (1) below, when one of the six corners of the polygon mirror 63 is positioned near the first opening end A as illustrated in
[B] That is, the first gap K1 and the second gap K2 always have approximately the same length during the rotation of the polygon mirror 63, so that the first pressure and the second pressure have approximately the same magnitude (absolute value). On the other hand, since air in the first cover part 651 is blown out from the first gap K1 and air is suck into the first cover part 651 from the second gap K2, the phase of a pressure variation in the first pressure and the phase of a pressure variation in the second pressure are shifted by 180° (corresponding to 0.5 cycle) (see
[C] In this way, the phase of sound generated in the air blowing port near the first gap K1 and the phase of sound generated in the air suction port near the second gap K2 are also shifted by 180°. As a consequence, these sounds are mutually canceled out and a noise level is reduced. Consequently, even when the non-sealed type first cover part 651 is used, it is possible to sufficiently reduce noise generated by the rotation of the polygon mirror 63.
When n is 2, θ is 120°, and when n is 3, θ is 180°. As described above, even when n is a natural number of 2, 3, . . . , which is smaller than the number of surfaces of the polygon mirror 63, it is possible to achieve the same effects as those of the aforementioned [A] to [C]. That is, when the first opening 651C is formed such that the opening angle θ satisfies Equation (3), it is possible to reduce the noise level. As illustrated in
As illustrated in
That is, in the present embodiment, the phase difference between the first waveform and the second waveform is set such that the amplitude of the waveform obtained by synthesizing the first waveform (see
As illustrated in
L1<L2 (4)
Even when θ is 120°, it is possible to achieve the same effects as those of the aforementioned [A] to [C]. That is, since the first opening 651C is formed such that the opening angle θ satisfies Equation (3), it is possible to reduce the noise level. As described above, it has been confirmed by experiments that the noise level is reduced when θ is 120° (see
As illustrated in
When the opening angle θ of the first opening 651C is 72°,
[A1] Since the first opening 651C is formed such that the opening angle θ satisfies Equation (3), when one of the five corners of the polygon mirror 63 is positioned near the first opening end A, another one corner is positioned near the second opening end B. Even when the center between a pair of adjacent corners of the polygon mirror 63 is positioned near the first opening end A, the center between another pair of adjacent corners thereof is positioned near the second opening end B similarly to the above.
Consequently, it is possible to achieve the same effects as those of the aforementioned [B] and [C].
When the opening angle of the first opening 651C centered on the axial center P of the polygon mirror 63 is θ and n is set as a natural number smaller than the number of surfaces of the polygon mirror 63, the first opening 651C may also be formed such that the opening angle θ satisfies Equations (1) and (2) below.
θ>((360°/the number of surfaces of rotary polyhedron)×n)×0.83 (1)
θ<((360°/the number of surfaces of rotary polyhedron)×n)×1.17 (2)
When n is 1, 49.8°<θ<70.2° according to Equations (1) and (2) (the number of surfaces of the polygon mirror 63 is 6).
When 49.8°<θ<70.2°, the noise level is reduced. The reason will be described.
Equations (1) and (2) indicate that the opening angle θ of the first opening 651C is within +/−17% of the opening angle θ of the first opening 651C in the first embodiment. This indicates that the phase difference between the first waveform of the pressure variation in the first pressure and the second waveform of the pressure variation in the second pressure in the present fifth embodiment increases/decreases by +/−0.17 cycle with respect to the phase difference in the first embodiment. In the first embodiment, there is the phase difference corresponding to 0.5 cycle. Therefore, in the range of 49.8°<θ<70.2°, a phase difference corresponding to 0.33 cycle to 0.67 cycle occurs in both waveforms.
As illustrated in
Number | Date | Country | Kind |
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2018-153405 | Aug 2018 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
20040104994 | Ishihara | Jun 2004 | A1 |
20130222863 | Yoshida | Aug 2013 | A1 |
20140211288 | Ohta | Jul 2014 | A1 |
20170299975 | Mizutani et al. | Oct 2017 | A1 |
20180113396 | Fukuhara | Apr 2018 | A1 |
20200166864 | Yoshida | May 2020 | A1 |
Number | Date | Country |
---|---|---|
6-95021 | Apr 1994 | JP |
6-308416 | Nov 1994 | JP |
2017-191257 | Oct 2017 | JP |
Entry |
---|
Extended European Search Report dated Jan. 16, 2020 in corresponding European Patent Application No. 19191680.8. |
Number | Date | Country | |
---|---|---|---|
20200057300 A1 | Feb 2020 | US |