Patent Application
20180234565
The present invention relates to a light scanning apparatus used in an image forming apparatus such as a copy machine, a printer, a facsimile, or a multi-function peripheral.
As a light scanning apparatus used in an image forming apparatus of an electrophotographic printing method, a light scanning apparatus having the following configuration is known in the art. That is, a light spot is formed on a surface of a photosensitive member by deflecting laser light emitted from a light source using a rotary polygon mirror and condensing them onto the photosensitive member using an imaging optical system. The light spot scans on the surface on the photosensitive member so that a latent image is formed on the surface of the photosensitive member.
Inside the light scanning apparatus, a deflector having a rotary polygon mirror is provided for scanning by deflecting the laser light emitted from a semiconductor laser device. A predetermined latent image is obtained on the photosensitive member by scanning the laser light on the photosensitive member using the rotary polygon mirror and repeatedly turning on and off the semiconductor laser device in association with the operation of the photosensitive member.
Japanese Patent Application Laid-Open No. 2013-125041 discusses a light scanning apparatus in which a plurality of semiconductor laser devices are arranged in parallel in a rotation axis direction of the rotary polygon mirror in order to mount a plurality of semiconductor laser devices used as a light source in a single housing.
In order to respond to demands for high image quality and high productivity, it is demanded for a single light source of the light scanning apparatus to provide a plurality of light emitting points (hereinafter, referred to as “multi-beam”). The multi-beam increases a size of the light source. If a plurality of multi-beam light sources are arranged in parallel in the rotation axis direction of the rotary polygon mirror as discussed in Japanese Patent Application Laid-Open No. 2013-125041, a size of the light scanning apparatus also increases in the rotation axis direction of the rotary polygon mirror.
In view of such circumstances, an object of the invention is to miniaturize the light scanning apparatus in the rotation axis direction of the rotary polygon mirror.
According to an aspect of the invention, there is provided a light scanning apparatus, comprising:
a plurality of optical elements including a mirror and a lens;
a housing configured to house the plurality of optical elements therein;
a first laser light source having a plurality of light emitting points to emit laser lights for exposing a first photosensitive member;
a first holder attached to the housing and configured to hold the first laser light source;
a second laser light source having a plurality of light emitting points to emit laser lights for exposing a second photosensitive member;
a second holder attached to the housing and configured to hold the second laser light source;
a rotary polygon mirror configured to be rotated and provided with a plurality of reflection surfaces by which the laser lights emitted from each of the first laser light source and the second laser light source are deflected; and
a lens, of the plurality of optical elements, to which the laser lights emitted from each of the first laser light source and the second laser light source and deflected by the rotary polygon mirror are first incident,
wherein the laser lights emitted from each of the first laser light source and the second laser light source are incident to the rotary polygon mirror without being reflected by a mirror,
wherein the first holder and the second holder are attached to the housing in mutually different positions in a rotation axis direction of the rotary polygon mirror and in an optical axis direction of the lens, and
wherein the first holder and the second holder are attached to the housing so that a first incident light path of the laser lights emitted from the first laser light source and incident to the rotary polygon mirror is placed between a second incident light path of the laser lights emitted from the second laser light source and incident to the rotary polygon mirror and the lens, and a part of the first holder and a part of the second holder overlap one another in the rotation axis direction.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
The embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. In the following description, a rotation axis direction of a rotary polygon mirror 42 described below will be referred to as a “Z-axis direction,” a longitudinal direction of an optical element will be referred to as a “Y-axis direction,” and a direction perpendicular to the Y-axis and Z-axis directions will be referred to as an “X-axis direction.” In addition, a rotational direction of the rotary polygon mirror 42 will be referred to as a main scanning direction, and a direction perpendicular to the main scanning direction will be referred to a sub-scanning direction. In this case, a main scanning direction may become in parallel with the Y-axis or Z-axis, and a sub-scanning direction may become in parallel with the Z-axis.
<Configuration of Image Forming Apparatus>
A configuration of an image forming apparatus according to a first embodiment will be described.
The intermediate transfer belt 20 is formed in an endless shape and is looped around a pair of belt conveyance rollers 21 and 22. As the intermediate transfer belt 20 is rotated in an arrow direction H, the toner images formed by the image forming engine 10 are transferred. In addition, a secondary transfer roller 30 is arranged oppositely to one of the belt conveyance rollers 21 by interposing the intermediate transfer belt 20. A recording sheet P is inserted between a secondary transfer roller 30 and the intermediate transfer belt 20 pressed to each other, so that the toner images are transferred from the intermediate transfer belt 20. The four image forming engines 10Y, 10M, 10C, and 10Bk described above are arranged in parallel one another under the intermediate transfer belt 20, so that the toner images formed to match image information of each color are transferred to the intermediate transfer belt 20 (hereinafter, referred to as “primary transfer”). The four image forming engines 10 are arranged in order of a yellow image forming engine 10Y, a magenta image forming engine 10M, a cyan image forming engine 10C, and a black image forming engine 10Bk along a rotational direction of the intermediate transfer belt 20 (arrow direction H).
A light scanning apparatus 40 for exposing a photosensitive drum 50 as a photosensitive member provided in each image forming engine 10 depending on the image information is arranged under the image forming engine 10. The photosensitive drums 50Y, 50M, 50C, and 50Bk serve as first, second, third, and fourth photosensitive members, respectively. Note that the light scanning apparatus 40 is not illustrated specifically in
Each image forming engine 10 has a photosensitive drum 50 and a charging roller 12 for electrically charging the photosensitive drum 50 to a uniform background voltage. In addition, each image forming engine 10 has a developing device 13 configured to develop an electrostatic latent image formed on the photosensitive drum 50 (photosensitive member) through exposure of the laser light to form a toner image. The developing device 13 forms a toner image depending on image information of each color on the photosensitive drum 50 as a photosensitive member. The developing devices 13Y, 13M, 13C, and 13Bk serve as first, second, third, and fourth developing devices, respectively.
A primary transfer roller 15 is arranged to face the photosensitive drum 50 of each image forming engine 10 by interposing the intermediate transfer belt 20. The primary transfer roller 15 transfers the toner image on the photosensitive drum 50 to the intermediate transfer belt 20 by applying a predetermined transfer voltage. The primary transfer rollers 15Y, 15M, 15C, and 15Bk serve as first, second, third, and fourth transfer members, respectively.
Meanwhile, the recording sheet P is supplied from a feeding cassette 2 housed in a lower part of the printer housing 1 to the inside of the printer, specifically, a secondary transfer position inside of the printer where the intermediate transfer belt 20 and the secondary transfer roller 30 abut on each other. A pickup roller 24 and a feeding roller 25 are juxtaposed in an upper part of the feeding cassette 2 to pick up the recording sheet P stored in the feeding cassette 2. A retardation roller 26 for preventing duplicated delivery of the recording sheet P is arranged to face the feeding roller 25. The conveyance path 27 of the recording sheet P inside the printer is provide substantially vertically along the right side surface of the printer housing 1. The recording sheet P extracted from the feeding cassette 2 positioned in the bottom of the printer housing 1 is lifted along the conveyance path 27 and is fed to a registration roller 29 that controls an entering timing of the recording sheet P into a secondary transfer position. Then, the toner images are transferred to the recording sheet P in the secondary transfer position, which is then fed to a fixing unit 3 (indicated by a dotted line) provided in the downstream side of the conveyance direction. The recording sheet P having the toner images fixed by the fixing unit 3 is discharged to a discharge tray 1a provided in an upper part of the printer housing 1 through the discharge roller 28. In formation of a full-color image using the color laser beam printer configured in this manner, first, the light scanning apparatus 40 exposes the photosensitive drums 50 of each image forming engine 10 at predetermined timings depending on image information of each color.
<Light Scanning Apparatus>
The rotary polygon mirror 42 that deflects the laser light emitted from the light source 51 and the scanner motor 41 that rotates the rotary polygon mirror 42 are installed on the bottom surface of the housing 101. The laser light emitted from the light source 51 is reflected by the rotary polygon mirror 42, and the laser light reflected by the rotary polygon mirror 42 is directed to the photosensitive drum 50 serving as a surface to be scanned. In addition, the laser light emitted from the light source 51a is reflected by the rotary polygon mirror 42 and is directed to the light receiving sensor 55 mounted on the circuit board 45.
It is necessary to constantly maintain the time elapsing until the latent image starts to be formed on the photosensitive drum 50 by the laser light from the timing at which the light receiving sensor 55 receives the laser light. The light receiving sensor 55 is provided to maintain this time constantly. That is, the light receiving sensor 55 is used to determine the timing at which laser lights are emitted from the light sources 51a to 51d. The light receiving sensor 55 is arranged immediately over the light source 51a (chip holder 46a) (in the +Z direction) (refer to
As the circuit board 45 is attached to the side wall portion 101d of the light scanning apparatus 40, the chip holders 46a and 46b protrude inward of the light scanning apparatus 40 (refer to
<Light Path of Laser Light>
The laser light LM emitted from the light source 51b and mated with the photosensitive drum 50M is deflected by the rotary polygon mirror 42 and is incident to the optical lens 60a. The laser light LM passing through the optical lens 60a is reflected by the reflection mirrors 62b and 62c, is incident to the optical lens 60e, passes through the optical lens 60e, and is then reflected by the reflection mirror 62d. The laser light LM reflected by the reflection mirror 62d passes through the transparent window (not shown) and scans the photosensitive drum 50M. The optical lens 60a is a lens where the laser lights emitted from the light sources 51a and 51b out of a plurality of optical elements and deflected by the rotary polygon mirror 42 are initially incident.
The laser light LC emitted from the light source 51c and mated with the photosensitive drum 50C is deflected by the rotary polygon mirror 42 and is incident to the optical lens 60c. The laser light LC passing through the optical lens 60c is reflected by the reflection mirrors 62e and 62f and is incident to the optical lens 60f, and the laser light LC passing through the optical lens 60f is reflected by the reflection mirror 62g. The laser light LC reflected by the reflection mirror 62g passes through the transparent window (not shown) and scans the photosensitive drum 50C.
The laser light LBk emitted from the light source 51d and mated with the photosensitive drum 50Bk is deflected by the rotary polygon mirror 42 and is incident to the optical lens 60c. The laser light LBk passing through the optical lens 60c is incident to the optical lens 60d, passes through the optical lens 60d, and is then reflected by the reflection mirror 62h. The laser light LBk reflected by the reflection mirror 62h passes through the transparent window (not shown) and scans photosensitive drum 50Bk. The optical lens 60c is a lens where the laser lights emitted from the light sources 51c and 51d out of a plurality of optical elements and deflected by the rotary polygon mirror 42 are initially incident.
<Light Source Unit>
The laser light deflected and scanned by the rotary polygon mirror 42 passes through the optical lenses 60a and 60c having strong power in the main scanning direction and is then guided to the optical lenses 60b, 60d, 60e, and 60f having strong optical power in the sub-scanning direction (refer to
A pair of light source units 47a and 47b are provided on the side wall portion 101d of the housing 101. Specifically, the light source unit 47a has the light source 51a mated with the photosensitive drum 50Y and the light source 51b mated with the photosensitive drum 50M, and the light source unit 47b has the light source 51c mated with the photosensitive drum 50C and the light source 51d mated with the photosensitive drum 50Bk. Hereinafter, the subscripts “a” and “b” will be omitted unless necessary. A pair of light source units 47 are provided plane-symmetrically with respect to a plane passing through a rotation axis of the rotary polygon mirror 42 in parallel with the YZ-plane. A single light source 51 has a plurality of light emitting points such as eight (or four) light emitting points, and eight (or four) laser lights are emitted from a single light source. For this reason, the size of the light source 51 increases, compared to a light source having, for example, a single light emitting point. The light emitting point of the laser light can be reduced to be equal to or smaller than 1 mm even when the number of emitted laser lights increases. However, a size of the component consisting of an electrical connection part for driving a plurality of light emitting points increases. For this reason, a packaging size of the light source having a plurality of light emitting points increases as a result.
<Arrangement of Light Source>
In order to reduce the size of the housing 101 as small as possible, the light scanning apparatus 40 is configured as described below. The size of the housing 101 is determined such that a length of the reflection mirror 62 is set to a necessary and sufficient length so that the reflection mirror 62 guides the laser light to the surface to be scanned, and the size of the housing 101 has a minimum size required to house the reflection mirror 62. The light source 51 is arranged to match the side wall portion 101d in the housing 101 having such a size. As a result, it is possible to compactly reduce the size of the whole light scanning apparatus 40.
According to the first embodiment, for example, the light source 51 has eight light emitting points having an outer diameter of ϕ11.6. In order to arrange the light source 51 on the side wall portion 101d of the housing 101, it is necessary to increase the angular difference between a pair of light sources 51. This is because interference between a pair of light source units 47 can be prevented when the angular difference between a pair of the light sources 51 arranged in the same light source unit 47 is provided only in the sub-scanning direction (Z-axis direction). Here, the light path of the laser light emitted from the light source 51a will be referred to as a light path 511a as a first light path, and the light path of the laser light emitted from the light source 51b will be referred to as a light path 511b as a second light path. The angular difference between a pair of light sources 51 refers to an angle between the light paths 511a and 511b. As the angular difference between the light paths 511a and 511b of the pair of light sources 51 in the sub-scanning direction increases, the reflection surface of the rotary polygon mirror 42 becomes distant from an ideal position. Therefore, an error of the position where the laser light arrives on the photosensitive drum 50 increases. As a result, image quality is degraded. For example, an irradiation position of the laser light on the photosensitive drum 50 deviates due to surface eccentricity of the rotary polygon mirror 42.
In order to reduce the angular difference between the light paths 511a and 511b of the light sources 51a and 51b in the sub-scanning direction, it is assumed that the light source unit 47 is disposed apart from the rotary polygon mirror 42. Then, it is necessary to separate the side wall portion 101d where the light source unit 47 of the light scanning apparatus 40 is provided from the rotary polygon mirror 42. That is, the size of the housing 101 in the Y-axis direction increases. Therefore, in order to reduce the size of the light scanning apparatus 40 as small as possible while guaranteeing sufficient necessary image quality, the light source unit 47 is arranged to emit the laser light such that an angular difference is also provided in the main scanning direction. As a result, it is possible to bring the side wall portion 101d of the housing 101 closer to the rotary polygon mirror 42 and reduce the size of the housing 101 in the Y-axis direction. An angle β as a second angle illustrated in
The chip holder 46a as the first holder and the chip holder 46b as the second holder are attached to mutually different positions in the rotation axis direction of the rotary polygon mirror 42 and the optical axis direction of the lens. The chip holder 46a is arranged in the bottom surface side of the housing 101 relative to the chip holder 46b. The chip holders 46a and 46b are attached to the housing 101 such that a first incident light path (first light path 511a) of the laser light emitted from the light source 51a and incident to the rotary polygon mirror 42 is placed between a second incident light path (second light path 511b) of the laser light emitted from the light source 51b and incident to the rotary polygon mirror 42 and the optical lens 60a. In addition, the chip holders 46a and 46b are attached to the housing 101 such that a part of the chip holder 46a and a part of the chip holder 46b overlap one another in the rotation axis direction of the rotary polygon mirror 42. Specifically, a part of the upper end of the chip holder 46a and a part of the lower end of the chip holder 46b overlap one another in the rotation axis direction of the rotary polygon mirror 42. At least in the rotation axis direction of the rotary polygon mirror 42, a part of the upper end of the lens barrel portion of the chip holder 46a and a part of the lower end of the lens barrel portion of the chip holder 46b overlap one another. The lens barrel portion is a tubular portion that connects a portion for holding the collimator lens 53a (53b) and a portion for holding the light source 51a (51b) to each other. That is, the chip holders 46a and 46b are arranged to incline with respect to a rotation axis of the rotary polygon mirror 42. For this reason, the light scanning apparatus 40 can be designed in a small size in the rotation axis direction of the rotary polygon mirror 42, compared to a light scanning apparatus in which a pair of chip holders are juxtaposed in the rotation axis direction of the rotary polygon mirror 42.
The light source 51a is provided under the virtual plane Sp so as to have an angle γ/2 with respect to the virtual plane Sp in the sub-scanning direction (Z-axis direction). The light source 51b is provided over the virtual plane Sp so as to have an angle γ/2 with respect to the virtual plane Sp in the sub-scanning direction (Z-axis direction). The angle γ/2 is designed, for example, to be equal to or smaller than 3° in order to miniaturize the housing 101 and reduce the surface eccentricity of the rotary polygon mirror 42. That is, the angle γ is designed, for example, to be larger than 0° and equal to or smaller than 6°. Note that the angle γ may be set to “0°” depending on applications. In this case, in
In a pair of light sources 51a and 51b mounted on the same light source unit 47a, the chip holders 46a and 46b are arranged to have the following positional relationship. The chip holder 46a has the light source 51a that emits laser light directed to the photosensitive drum 50Y arranged outside of the light scanning apparatus 40 with respect to the rotary polygon mirror 42. The chip holder 46a is arranged in a direction (−Z direction) opposite to the direction (+Z direction) directed from the light scanning apparatus 40 to the photosensitive drum 50Y, compared to the other chip holder 46b.
The laser lights directed to a pair of photosensitive drums 50M and 50C arranged in the vicinity of the center of the width direction (X direction) of the image forming apparatus out of a plurality of photosensitive drums 50 are finally reflected by the reflection mirrors 62d and 62g inside the light scanning apparatus 40. The reflection mirrors 62d and 62g are arranged in the vicinity of the rotary polygon mirror 42. Furthermore, the reflection mirrors 62d and 62g are provided on the left surfaces 70d and 70g (refer to
The laser light directed to the photosensitive drum 50 is not perpendicular to the installation surface of the light scanning apparatus 40 (parallel to the Z direction). As described above in conjunction with
In this manner, the laser lights LM and LC emitted from the light scanning apparatus 40 are irradiated to the photosensitive drums 50M and 50C substantially at the same angle α. For this reason, the left surface 70d of the reflection mirror 62d where the laser light LM is finally reflected inside the light scanning apparatus 40 becomes closer to the chip holder 46 relative to the left surface 70b of the reflection mirror 62g in the width direction (X direction) of the light scanning apparatus 40.
<Configuration of Light Source Unit>
The chip holders 46a and 46b mounted with the light sources 51a and 51b and the collimator lenses 53a and 53b are attached to a single laser holder 44a. The laser holder 44a is inserted into openings 43a and 43b provided in the laser holder 44a from the collimator lenses 53a and 53b side. A plate spring 52a is inserted between the chip holders 46a and 46b attached to the laser holder 44a. The chip holders 46a and 46b are fixed to the laser holder 44a by virtue of an elastic force of the plate spring 52a so as not to move inside the laser holder 44a. Note that, although the chip holders 46a and 46b are attached to the laser holder 44a separate from the housing 101 in the embodiment, the chip holders 46a and 46b may be directly attached to the housing 101. If the chip holders 46a and 46b are directly attached to the housing 101, a structure such as the laser holder 44a illustrated in
The laser holder 44a to which a pair of chip holders 46a and 46b are attached is attached between the housing 101 and the circuit board 45a using screws or the like as illustrated in
<Arrangement of Light Receiving Sensor>
The rotational direction of the rotary polygon mirror 42 or the arrangement of the light receiving sensor 55 is determined such that the laser light reflected by the rotary polygon mirror 42 is received by the light receiving sensor 55, and is then irradiated to the photosensitive drum 50. A timing for starting formation of the latent image on each photosensitive drum 50 (hereinafter, referred to as a “write timing”) is determined on the basis of the timing at which the laser light arrives at the light receiving sensor 55. As a result, it is possible to align the latent image start position on the photosensitive drum 50. The light receiving sensor 55 is arranged to satisfy these conditions.
Since the laser light reflected by the rotary polygon mirror 42 is incident to the light receiving sensor 55, it is necessary to prevent the chip holder 46 arranged in the vicinity of the light receiving sensor 55 from interfering with the laser light. The chip holder 46 has the adjustment protrusion 48 and the fixing portion 49. The adjustment protrusion 48 and the fixing portion 49 are arranged such that a pair of light sources 51 housed in a single light source unit 47 become distant from each other. Specifically, the chip holder 46a is arranged such that the adjustment protrusion 48a becomes distant from the chip holder 46b, and the fixing portion 49a becomes distant from the chip holder 46b. The chip holder 46b is arranged such that the adjustment protrusion 48b becomes distant from the chip holder 46a, and the fixing portion 49b becomes distant from the chip holder 46a. That is, the chip holders 46a and 46b are arranged as illustrated in
The adjustment protrusion 48 and the fixing portion 49 are arranged in this way for the two following reasons. First, using this arrangement, it is possible to design the receiving portion 54 for bonding the fixing portion 49 of the chip holder 46 to the laser holder 44. Second, using this arrangement, it is possible to secure a space for manipulating a tool when the adjustment protrusion 48 for controlling an interval of the laser light in the sub-scanning direction is manipulated with the tool.
Here, it is assumed that light scanning apparatus 40 is configured such that the laser light emitted from the chip holder 46 is received by the light receiving sensor 55. The laser light emitted from the light source 51a and reflected by the rotary polygon mirror 42 is necessarily incident to the light receiving sensor 55 without colliding with the adjustment protrusion 48a and the fixing portion 49a of the chip holder 46a.
In
In the first embodiment, the cyan light source unit 47c is arranged in a position higher than that of the black light source unit 47d in the sub-scanning direction (Z-axis direction). In the first embodiment, the virtual line obtained by linking the four chip holders 46a to 46d has a parallelogram shape. According to the second embodiment, the chip holders 46a and 46b and the light receiving sensor 55 are arranged similarly to those of the first embodiment. However, according to the second embodiment, the chip holders 46c and 46d are arranged reversely to those of the first embodiment, and the chip holder 46d is arranged to be higher than the chip holder 46c in the sub-scanning direction (Z-axis direction). According to the second embodiment, the four chip holders 46a to 46d are arranged in the shape of an unfolded fan.
<Arrangement of Light Source>
As described above, according to the second embodiment, a pair of light sources 51 are held in a single light source unit 47, and a pair of light source units 47 are arranged symmetrically to the side wall portion 101d of the housing 101 with respect to a plane parallel to the YZ-plane through the rotation axis of the rotary polygon mirror 42. One of the pair of light sources 51 of the single light source unit 47 having a larger incident angle in the main scanning direction is positioned under the other light source 51 in a vertical direction. As a result, according to the second embodiment, it is possible to miniaturize the light scanning apparatus in the rotation axis direction of the rotary polygon mirror.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2017-025996, filed Feb. 15, 2017, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-025996 | Feb 2017 | JP | national |
