OPTICAL SCANNING DEVICE AND IMAGE FORMING APPARATUS INCLUDING THE SAME

INCORPORATION BY REFERENCE

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2024-001952 filed on Jan. 10, 2024, the contents of which are hereby incorporated by reference.

BACKGROUND

The present disclosure relates to an optical scanning device that is incorporated in an electrophotographic image forming apparatus so as to irradiate an image carrier with light to thereby form an electrostatic latent image, and also relates to an image forming apparatus including the optical scanning device.

Conventional optical scanning devices irradiate a charged image carrier with light so as to form an electrostatic latent image on the image carrier. An optical scanning device includes a housing, a transmissive member, a linear member, a drive member, a guide rail, a cleaning holder, a cleaning member, and a stopper.

In the housing, an emission port for laser light for irradiating the image carrier is formed to extend in a main scanning direction of the laser light. The transmissive member extends in the main scanning direction of the laser light and seals the emission port for the laser light. The linear member extends in an extending direction of the transmissive member. The guide rail is juxtaposed with the emission port so as to extend in the extending direction of the transmissive member.

The cleaning holder, which is coupled to the linear member, includes two cleaning holders that each move along the transmissive member as the linear member travels in a loop. The cleaning member, which is fixed to the cleaning holder, includes two cleaning members that each slide on the transmissive member along with the movement of the cleaning holder to thereby clean the transmissive member. The cleaning holder comes into abutment with a stopper at one end of a movement path thereof to thereby cause the linear member to stop traveling.

SUMMARY

According to one aspect of the present disclosure, an optical scanning device includes a housing, a transmissive member, a linear member, a drive portion, a guide rail, a cleaning holder, a cleaning member, a detection portion, and a control portion. The optical scanning device irradiates an image carrier with laser light so as to form an electrostatic latent image. In the housing, a laser-light emission port is formed to extend in a main scanning direction of the laser light so as to correspond to the image carrier. The transmissive member is transmissive with respect to the laser light, extends in the main scanning direction of the laser light, and seals the laser-light emission port. The linear member is stretched in a loop on the housing. The drive portion drives the linear member to travel in a predetermined direction. The guide rail is juxtaposed with the laser-light emission port so as to extend in the extending direction of the transmissive member. The cleaning holder is fixed to the linear member and, when the linear member is driven by the drive portion to travel, moves over the transmissive member along the guide rail. The cleaning member is fixed to the cleaning holder and slides with respect to the transmissive member along with movement of the cleaning holder to thereby clean the transmissive member. The detection portion is disposed on one side in the extending direction of the transmissive member so as to detect that the cleaning holder has reached one end part of a movement path of the cleaning holder. The control portion controls driving of the drive portion. The detection portion includes a light emitter that emits light in a juxtaposition direction of the transmissive member and a light receiver that receives light emitted from the light emitter, and the detection portion is disposed along the housing such that longitudinal directions of the light emitter and the light receiver are parallel to a movement direction of the cleaning holder. The cleaning holder includes a light blocking portion that is located, when the cleaning holder reaches the one end part of the movement path thereof, between the light emitter and the light receiver so as to block light emitted from the light emitter, with a gap formed between the light blocking portion and the housing. The housing includes a light leakage prevention portion formed between the light emitter and the light receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view schematically illustrating an overall configuration of an image forming apparatus incorporating an optical scanning device of the present disclosure.

FIG. 2 is a perspective view of an optical scanning device according to a first embodiment of the present disclosure.

FIG. 3 is an enlarged perspective view of and around a cleaning holder fitted to a cover portion of the optical scanning device according to the first embodiment.

FIG. 4 is an enlarged perspective view of and around the cleaning holder fitted to the cover portion of the optical scanning device according to the first embodiment.

FIG. 5 is a sectional view of the cleaning holder fitted to the cover portion of the optical scanning device according to the first embodiment as seen from a movement direction of the cleaning holder.

FIG. 6 is a plan view of the optical scanning device according to the first embodiment, illustrating a state where the cleaning holder has been detected by a detection portion.

FIG. 7 is a plan view of the optical scanning device according to the first embodiment, illustrating a state where the cleaning holder has been detected by the detection portion.

FIG. 8 is a schematic perspective view illustrating a positional relationship between the detection portion and a first light blocking portion of the optical scanning device according to the first embodiment.

FIG. 9 is a schematic perspective view illustrating a positional relationship between the detection portion and a second light blocking portion of the optical scanning device according to the first embodiment.

FIG. 10 is a block diagram illustrating an example of a control path used in the image forming apparatus.

FIG. 11 is a perspective view illustrating a state where the detection portion of the optical scanning device according to the first embodiment is shielded from light by the first light blocking portion.

FIG. 12 is a plan view illustrating a state where the detection portion of the optical scanning device according to the first embodiment is shielded from light by the first light blocking portion.

FIG. 13 is a sectional view illustrating a state where the detection portion of the optical scanning device according to the first embodiment is shielded from light by the first light blocking portion, as seen from the movement direction of the cleaning holder.

FIG. 14 is an enlarged view illustrating a positional relationship, in height a direction, among a light emitter, the first light blocking portion, and a light blocking rib in FIG. 13.

FIG. 15 is a plan view illustrating a configuration of and around a detection portion of an optical scanning device according to a second embodiment of the present disclosure.

FIG. 16 is a sectional view illustrating a state where the detection portion of the optical scanning device according to the second embodiment is shielded from light by a first light blocking portion, as seen from a movement direction of a cleaning holder.

FIG. 17 is a plan view illustrating a configuration of and around a detection portion of an optical scanning device according to a third embodiment of the present disclosure.

FIG. 18 is a sectional view illustrating a state where the detection portion of the optical scanning device according to the third embodiment is shielded from light by a first light blocking portion, as seen from a movement direction of a cleaning holder.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. FIG. 1 is a sectional view schematically illustrating an overall configuration of an image forming apparatus 1 incorporating an optical scanning device of the present disclosure. The image forming apparatus 1 is a tandem-type color printer. The image forming apparatus 1 includes photosensitive drums 11a to 11d, which are rotatable, as image carriers. Each of the photosensitive drums 11a to 11d is formed of, for example, an organic photosensitive member (an OPC photosensitive member) on which an organic photosensitive layer is formed or an amorphous silicon photosensitive member on which an amorphous silicon photosensitive layer is formed. The photosensitive drums 11a to 11d are disposed in a tandem manner respectively corresponding to colors of yellow, magenta, cyan, and black.

Around the photosensitive drum 11a, there are disposed a developing device 2a, a charger 13a, and a cleaning device 14a. Likewise, around the photosensitive drums 11b to 11d, there are disposed developing devices 2b to 2d, chargers 13b to 13d, and cleaning devices 14b to 14d, respectively. Furthermore, below the developing devices 2a to 2d, an optical scanning device 12 is disposed.

The developing devices 2a to 2d are each disposed on a right side of a corresponding one of the photosensitive drums 11a to 11d. The developing devices 2a to 2d each face a corresponding one of the photosensitive drums 11a to 11d, and each supply toner to the corresponding one of the photosensitive drums 11a to 11d. Herein, directions indicated as “right” and “left” refer to a rightward direction and a leftward direction in the drawings, respectively.

The chargers 13a to 13d are each disposed upstream of a corresponding one of the developing devices 2a to 2d with respect to a rotation direction of the corresponding one of the photosensitive drums 11a to 11d, and each face a surface of the corresponding one of the photosensitive drums 11a to 11d. The chargers 13a to 13d each uniformly charge the surface of the corresponding one of the photosensitive drums 11a to 11d.

Based on image data such as letters and patterns fed from a personal computer or the like to an image input portion, the optical scanning device 12 irradiates (optically scans), with light, the surfaces of the photosensitive drums 11a to 11d having been uniformly charged by the chargers 13a to 13d, as a result of which electrostatic latent images are formed on the surfaces of the photosensitive drums 11a to 11d.

The optical scanning device 12 has a housing 12a that includes an accommodation portion 12b having an opening in one surface thereof and a cover portion 12c covering the opening. The accommodation portion 12b has a scanning optical system 120 incorporated therein. In the cover portion 12c, emission ports 12d (see FIG. 4) for light (laser light) emitted from the scanning optical system 120 are formed so as to correspond to the photosensitive drums 11a to 11d, respectively. Furthermore, as will be described later, the emission ports 12d are each covered with a transmissive member 52. The transmissive member 52 is transmissive with respect to the light emitted from the scanning optical system 120.

The scanning optical system 120 includes a laser light source (unillustrated) and a polygon mirror. The scanning optical system 120 further includes at least one reflection mirror and a lens so as to correspond to each of the photosensitive drums 11a to 11d. The laser light emitted from the laser light source is applied, via the polygon mirror, the reflection mirrors, and the lenses, to the surface of each of the photosensitive drums 11a to 11d from a downstream side of a corresponding one of the chargers 13a to 13d with respect to the rotation direction of the corresponding one of the photosensitive drums 11a to 11d. In this manner, electrostatic latent images are formed on the surfaces of the photosensitive drums 11a to 11d. These electrostatic latent images are developed into toner images by the developing devices 2a to 2d.

An intermediate transfer belt 17, which is an endless belt, is stretched among a tension roller 6, a driving roller 25, and a driven roller 27. The driving roller 25 is caused by a motor (unillustrated) to rotate, and thereby drives the intermediate transfer belt 17 to circulate in a clockwise direction in FIG. 1.

The photosensitive drums 11a to 11d are arranged below the intermediate transfer belt 17 so as to be adjacent to each other along a conveyance direction (an arrow direction in FIG. 1). Furthermore, the photosensitive drums 11a to 11d are each in contact with the intermediate transfer belt 17. Primary transfer rollers 26a to 26d each face a corresponding one of the photosensitive drums 11a to 11d with the intermediate transfer belt 17 therebetween. The primary transfer rollers 26a to 26d are pressed against the intermediate transfer belt 17 to form primary transfer portions together with the photosensitive drums 11a to 11d, respectively. In these primary transfer portions, the toner images are transferred to the intermediate transfer belt 17. To be more specific, a primary transfer voltage is applied to each of the primary transfer rollers 26a to 26d, and thereby the toner images on the photosensitive drums 11a to 11d are sequentially transferred onto the intermediate transfer belt 17 with predetermined timing. In this manner, on a surface of the intermediate transfer belt 17, a full-color toner image is formed in which the toner images of four colors of yellow, magenta, cyan, and black are superimposed on each other in a predetermined positional relationship.

A secondary transfer roller 34 faces the driving roller 25 with the intermediate transfer belt 17 therebetween. The secondary transfer roller 34 is pressed against the intermediate transfer belt 17 to form a secondary transfer portion together with the driving roller 25. In this secondary transfer portion, a secondary transfer voltage is applied to the secondary transfer roller 34, and thereby the toner image on the surface of the intermediate transfer belt 17 is transferred onto a sheet P. After the transfer of the toner image, a belt cleaning device 31 cleans residual toner off the intermediate transfer belt 17.

A sheet feed cassette 32 is arranged on a lower side inside the image forming apparatus 1. The sheet feed cassette 32 accommodates a plurality of sheets P. On a right side of the sheet feed cassette 32, a stack tray 35 is arranged for manual sheet feeding. On a left side of the sheet feed cassette 32, a first sheet conveyance path 33 is arranged. The first sheet conveyance path 33 conveys a sheet P fed out from the sheet feed cassette 32 to the secondary transfer portion. Further, on a left side of the stack tray 35, a second sheet conveyance path 36 is arranged. The second sheet conveyance path 36 conveys a sheet fed out from the stack tray 35 to the secondary transfer portion. Moreover, a fixing portion 18 and a third sheet conveyance path 39 are arranged on an upper left side inside the image forming apparatus 1. The fixing portion 18 performs a fixing process on the sheet P having an image formed thereon. The third sheet conveyance path 39 conveys the sheet P having been subjected to the fixing process to a sheet discharge portion 37.

Sheets P stacked in the paper feed cassette 32 is fed out one by one by a pick-up roller 33b and a pair of separation rollers 33a toward the first sheet conveyance path 33.

The first sheet conveyance path 33 and the second sheet conveyance path 36 join together before reaching a pair of registration rollers 33c (on an upstream side of the pair of registration rollers 33c). The pair of registration rollers 33c convey a sheet P to the secondary transfer portion with timing coordinated with the image forming operation performed on the intermediate transfer belt 17 and the operation of sheet feeding to the secondary transfer portion. Onto the sheet P having been conveyed to the secondary transfer portion, the full-color toner image on the intermediate transfer belt 17 is secondarily transferred by the secondary transfer roller 34 having the secondary transfer voltage applied thereto. The sheet P having the full-color toner image transferred thereon is conveyed to the fixing portion 18.

The fixing portion 18 includes a fixing belt that is heated by a heater, a fixing roller that is internally in contact with the fixing belt, a pressing roller that is pressed against the fixing roller with the fixing belt therebetween, etc. The fixing portion 18 applies heat and pressure to the sheet P having the toner image transferred thereon. In this manner, the fixing process is performed. The sheet P having the toner image fixed thereon in the fixing portion 18 is turned upside down, as necessary, through a fourth sheet conveyance path 40. Thereafter, the sheet P is conveyed again to the secondary transfer portion via the pair of registration rollers 33c, and thereafter, a new toner image is secondarily transferred onto a back side of the sheet P by the secondary transfer roller 34 and is then fixed in the fixing portion 18. The sheet P having the toner image fixed thereon passes through the third sheet conveyance path 39 to be discharged by a pair of discharge rollers 19 into the sheet discharge portion 37.

Next, with reference to FIGS. 2 to 6, a description will be given of the optical scanning device 12. FIG. 2 is a perspective view of an optical scanning device 12 according to a first embodiment of the present disclosure. FIG. 3 and FIG. 4 are enlarged perspective views of and around cleaning holders 511 and 512, respectively, which are fitted to a cover portion 12c of the optical scanning device 12. FIG. 5 is a sectional view of the cleaning holder 511, which is fitted to the cover portion 12c of the optical scanning device 12, as seen from a movement direction of the cleaning holder 511. FIG. 6 and FIG. 7 are each a plan view of the optical scanning device 12.

In the drawings referred to below, an extending direction of the transmissive member 52 is referred to as direction X, X1 being one side in the extending direction of the transmissive member 52 toward a detection portion 56, X2 being the other side in the extending direction of the transmissive member 52 away from the detection portion 56. A juxtaposition direction of the transmissive members 52 is referred to as direction Y, Y1 being one side in the juxtaposition direction of the transmissive members 52, Y2 being the other side in the juxtaposition direction of the transmissive members 52. Further, descriptions will be given of shapes of, and a positional relationship among, the various portions assuming that the cleaning holder 511 and a cleaning holder 512 are positioned above the cover portion 12c as shown in FIG. 2. Note that an up-down direction is a term used only for description, and does not limit directions when the optical scanning device 12 is incorporated in the image forming apparatus 1.

The optical scanning device 12 includes a housing 12a, a transmissive member 52, a linear member 54, a motor (a drive portion) 55, a guide rail 61, a stopper 62, the cleaning holders 511 and 512, a cleaning member 53, a detection portion 56, and a control portion 90 (see FIG. 10).

The housing 12a includes an accommodation portion 12b and the cover portion 12c fitted to cover the accommodation portion 12b. In the cover portion 12c, four emission ports 12d (see FIG. 5) for laser light are juxtaposed with each other so as to correspond to the four photosensitive drums 11a to 11d, respectively. Each of the emission ports 12d has a rectangular shape elongated in the main scanning direction (direction X) of a corresponding ray of the laser light, and the emission ports 12d are formed such that longitudinal directions (direction X) thereof are parallel to each other.

The transmissive members 52 are formed in a rectangular plate shape, and each seal a corresponding one of the emission ports 12d. This makes it possible to prevent entry of toner, dust, and the like into the optical scanning device 12 through the emission ports 12d. The four transmissive members 52 are juxtaposed with each other such that their longitudinal directions (direction X) are parallel to each other. Each of the transmissive members 52 is a glass cover, for example.

As the guide rail 61, a pair of guide rails 61 are disposed one on each of opposite sides of each pair of the transmissive members 52, with the each pair of the transmissive members 52 therebetween. In short, four guide rails 61 are juxtaposed with each other. The guide rails 61 protrude from an upper surface of the cover portion 12c and extend in the extending direction (in direction X) of the transmissive members 52. The guide rails 61 have guide ribs 61a, one for each, protruding outward from leading ends of the guide rails 61 and extend in the extending direction (direction X) of the transmissive members 52 (see FIG. 5).

The stopper 62 is disposed on one side (side X1) in an extending direction of the guide rails 61 and restrict movement of each of the cleaning holders 511 and 512 toward the one side (side X1) in the extending direction. The stopper 62 is fixed to the upper surface of the cover portion 12c. In the present embodiment, the stopper 62 includes two stoppers 62, of which one is disposed on one of two guide rails 61 straddled by the cleaning holder 511, and of which the other is disposed on one of two guide rails 61 straddled by the cleaning holder 512. The two stoppers 62 extend in the juxtaposition direction of the transmissive members 52 (in direction Y).

The cleaning holders 511 and 512 are disposed on the upper surface (the surface on the side of the photosensitive drums 11a to 11d) of the cover portion 12c, and each include a main body portion 51a, an engagement portion 51b, and respectively a first light blocking portion 511a and a second light blocking portion 512a. The main body portion 51a is formed in a plate shape, and extends in the juxtaposition direction (direction Y) of the transmissive members 52 so as to straddle corresponding two adjacent ones of the transmissive members 52.

The cleaning member 53 is fixed to a lower surface of the main body portion 51a (see FIG. 5). As the cleaning member 53, a pair of cleaning members 53 are disposed inward of the engagement portion 51b in the juxtaposition direction (in direction Y). Each of the cleaning members 53, along with loop traveling of the linear member 54, slides on an upper surface (a surface on the side of the photosensitive drums 11a to 11d) of a corresponding one of the transmissive members 52. In this manner, the upper surfaces of the transmissive members 52 are simultaneously cleaned, each by a corresponding one of the cleaning members 53.

The cleaning members 53 are each a rubber pad, for example. A material usable for the rubber pads is silicone rubber, for example. Each of the cleaning holders 511 and 512 is formed of a resin, for example. Note that each of the cleaning members 53 is not limited to a rubber pad and may instead be made of a non-woven fabric, for example.

As the engagement portion 51b, a pair of engagement portions 51b are disposed one on each of opposite sides with a corresponding pair of the guide rails 61 therebetween. Each of the engagement portions 51b protrudes downward from a bottom surface of the main body portion 51a, with a leading end part thereof bent toward an adjacent one of the guide rails 61. The engagement portions 51b each engage with a corresponding one of the guide ribs 61a. The cleaning holders 511 and 512 are each guided along a corresponding pair of the guide rails 61. This enables the cleaning holders 511 and 512 to stably move on the transmissive members 52 along the extending direction (direction X).

Further, the engagement portions 51b are in engagement with the guide ribs 61a, and thus opposite ends of the main body portion 51a are respectively latched on the guide rails 61 in a direction (an upward direction in FIG. 5) away from the housing 12a of the optical scanning device 12. This makes it possible to restrict upward movements (positional deviation) of the cleaning holders 511 and 512 and thus to prevent them from coming off from the cover portion 12c. Thus, the cleaning members 53 are allowed to be stably in close contact with the transmissive members 52.

Further, the other side (side X2) of each of the guide rails 61 in the extending direction is open in the extending direction thereof (in direction X) (see FIGS. 6 and 7). This allows easy installation of the cleaning holders 511 and 512 on the guide rails 61 by bringing the engagement portions 51b into engagement with the guide ribs 61a from the other ends of the guide rails 61 in the extending direction thereof and sliding the cleaning holders 511 and 512 toward the one side (side X1) in the extending direction of the guide rails 61. Thus, the optical scanning device 12 can be assembled with improved workability.

Note that the engagement portions 51b and the guide ribs 61a are an example of engagement of the cleaning holders 511 and 512 with the cover portion 12c, and the present disclosure is not limited to this structure.

The first light blocking portion 511a is disposed, in the cleaning holder 511, at a side end part on one side (side Y1) of the main body portion 51a in the juxtaposition direction, and protrudes in a direction (direction X1) toward one side in the extending direction (see FIG. 6 and FIG. 7). The second light blocking portion 512a is disposed, in the cleaning holder 512, at a side end part on the other side (side Y2) of the main body portion 51a in the juxtaposition direction, and protrudes in the direction (direction X1) toward the one side in the extending direction (see FIG. 6 and FIG. 7). As to shapes of the first light blocking portion 511a and the second light blocking portion 512a, a detailed description will be given later.

The main body portion 51a has a concave portion 51c that is concave downward from an upper surface thereof, and the linear member 54 is fitted in the concave portion 51c. Further, the concave portion 51c has a protrusion portion 51d protruding inward from an internal side surface thereof. Due to the provision of the protrusion portion 51d, the linear member 54 is bent inside the concave portion 51c. In this manner, the cleaning holders 511 and 512 are robustly fixed to the linear member 54. Note that the concave portion 51c may instead be formed to be concave upward from the lower surface of the main body portion 51a.

The linear member 54 is a timing belt or a wire, for example. The linear member 54 is stretched in the housing 12a in a loop between four stretching pulleys 57 so as to pass between the two adjacent transmissive members 52 in each pair of the transmissive members 52. The linear member 54 extends between the two adjacent transmissive members 52 of each pair so as to be parallel to the extending direction (direction X) of the transmissive members 52. The four stretching pulleys 57 are rotatably held on the upper surface of the cover portion 12c.

Further, one of the stretching pulleys 57 is coupled to a gear 57a disposed on a lower surface of the cover portion 12c (see FIG. 6 and FIG. 7). The gear 57a is coupled to the motor 55. The motor 55 drives the gear 57a to rotate, and thereby the linear member 54 is driven to travel in a loop.

The motor (the drive portion) 55 is disposed outward of the linear member 54, and is also fixed to the lower surface of the cover portion 12c. That is, an upper end of the motor 55 is disposed below an upper end of the linear member 54. This makes it possible to reduce space on the upper surface of the cover portion 12c. Furthermore, by disposing the motor 55 outward of the linear member 54, it is possible to achieve improved workability in maintenance of the motor 55 and the gear 57a. The motor 55 is rotatable both forward and backward directions, and drives the linear member 54 to travel, in top view, in a loop in a clockwise direction (direction D2) or in a counterclockwise direction (direction D1) (see FIG. 6 and FIG. 7). As a result, the cleaning holders 511 and 512 reciprocate along the longitudinal directions of the transmissive members 52 (the main scanning direction of the laser light). Further, in their reciprocation movements, the cleaning holder 511 and the cleaning holder 512 linearly move in mutually opposite directions.

Note that a cleaning process is executed, when the image forming apparatus 1 is in a maintenance mode, in response to a user inputting process starting instructions via an operation portion 80 (see FIG. 10) or a host device such as a personal computer. Further, the cleaning process may also be executed periodically each time printing (image formation) is performed on, for example, about 10000 sheets.

The detection portion 56 is disposed on the one side (side X1) in the extending direction of the transmissive members 52 so as to be disposed between a movement path of the cleaning holder 511 and a movement path of the cleaning holder 512 in the juxtaposition direction (in direction Y) of the transmissive members 52 (see FIGS. 6 and 7). The detection portion 56 detects that one of the cleaning holders 511 and 512 has reached the one end part of its movement path. Note that each of the cleaning holders 511 and 512, on reaching the one end part of its movement path, comes into contact with a corresponding one of the stoppers 62, so that its movement toward the one side (side X1) in the extending direction is restricted.

The detection portion 56 is a transmissive optical sensor (a photo interrupter) that includes a light emitter 56a and a light receiver 56b, and is capable of detecting, with a single sensor, that the cleaning holder 511 or the cleaning holder 512 has reached the one end part of its movement path. The light emitter 56a emits light in the juxtaposition direction of the transmissive members 52 (in direction Y). The light receiver 56b receives light emitted from the light emitter 56a. Note that, although, in the present embodiment, the light emitter 56a is disposed more on the one side (side Y1) in the juxtaposition direction than the light receiver 56b is, the light emitter 56a may instead be disposed more on the other side (side Y2) in the juxtaposition direction than the light receiver 56b is.

Next, with reference to FIG. 8 and FIG. 9, a description will be given of the detection portion 56 and the first and second light blocking portions 511a and 512a. FIG. 8 and FIG. 9 are perspective views schematically illustrating the detection portion 56 and the first and second light blocking portions 511a and 512a. FIG. 8 illustrates a positional relationship between the detection portion 56 and the first light blocking portion 511a, and FIG. 9 illustrates a positional relationship between the detection portion 56 and the second light blocking portion 512a.

The first light blocking portion 511a and the second light blocking portion 512a have different shapes. In the present embodiment, the second light blocking portion 512a has a through hole 512b formed therein to penetrate therethrough in the juxtaposition direction (direction Y) (see FIG. 9), but in the first light blocking portion 511a, no through hole 512b is formed (see FIG. 8).

As a result, when the cleaning holder 511 or the cleaning holder 512 reaches the one end part of its movement path, depending on whether the first light blocking portion 511a has reached or the second light blocking portion 512a has reached, the light receiver 56b receives light in different patterns.

Specifically, when a leading end part of the first light blocking portion 511a moving toward the one side (side X1) in the extending direction is inserted between the light emitter 56a and the light receiver 56b, light emitted from the light emitter 56a is blocked by the leading end part of the first light blocking portion 511a. As a result, the light receiver 56b becomes unable to receive light emitted from the light emitter 56a. At this time, the detection portion 56 is turned into an ON state. Furthermore, by moving the first light blocking portion 511a toward the one side (side X1) in the extending direction, the cleaning holder 511 reaches the one end part in its movement path to make contact with the corresponding one of the stoppers 62. As a result, the movement of the cleaning holder 511 is restricted in the direction toward the one side (side X1) in the extending direction. At this time, light emitted from the light emitter 56a is blocked by the first light blocking portion 511a, and the detection portion 56 is maintained in the ON state (see FIG. 8).

On the other hand, when a leading end part of the second light blocking portion 512a moving to the one side (side X1) in the extending direction is inserted between the light emitter 56a and the light receiver 56b, the light emitted from the light emitter 56a is blocked by the leading end part of the second light blocking portion 512a. As a result, the light receiver 56b becomes unable to receive light emitted from the light emitter 56a. At this time, the detection portion 56 is turned into the ON state. Furthermore, by moving the second light blocking portion 512a toward the one side (side X1) in the extending direction, the cleaning holder 512 reaches the one end part in its movement path to contact the corresponding one of the stoppers 62. As a result, the movement of the cleaning holder 512 is restricted in the direction toward the one side (side X1) in the extending direction. At this time, light emitted from the light emitter 56a passes through the through hole 512b to be received by the light receiver 56b, and the detection portion 56 switches to an OFF state (see FIG. 9).

In this manner, during execution of a cleaning mode, in the case where the On state of the detection portion 56 has been maintained for a predetermined time, the detection portion 56 detects that the cleaning holder 511 has reached the one end part of its movement path. Further, during execution of the cleaning mode, in the case where the detection portion 56 has switched to the OFF state after being maintained in the ON state for the predetermined time, the detection portion 56 detects that the cleaning holder 512 has reached the one end part of its movement path. At this time, the linear member 54 stops travelling. That is, when one of the cleaning holders 511 and 512 reaches the one end part of its movement path, so that its movement is restricted by the stopper 62, the other one of the cleaning holders 511 and 512 stops moving. This makes it possible to prevent the other one of the cleaning holders 511 and 512 from coming off from the guide rails 61 on the other side (side X2) of the guide rails 61 in the extending direction thereof where the guide rails 61 are open.

Next, referring back to FIG. 6 and FIG. 7, a description will be given of how the cleaning holders 511 and 512 operate. In the present embodiment, as mentioned previously, in one execution of the cleaning process, along the extending direction of the transmissive members 52 (direction X), a corresponding one of the cleaning members 53 reciprocates once. The description here will deal with a case where, during the cleaning process, a travelling direction of the linear member 54 changes from a direction (a first direction) indicated by arrow D1 to a direction (a second direction) indicated by arrow D2.

At a start of the cleaning process, the cleaning holder 511, at the one end of its movement path, holds the detection portion 56 in the ON state (see FIG. 6). At the start of the execution of the cleaning mode, by setting the state where the cleaning holder 511 is disposed at the one end part of its movement path as an initial position, the detection portion 56 is in the ON state and is able to detect the cleaning holder 511. This makes it possible to prevent occurrence of an initial error in the cleaning process.

When the cleaning process is started, the linear member 54 travels in the first direction indicated by arrow D1 (see FIG. 6). As a result, the cleaning holder 511 and the cleaning holder 512 move from their respective positions shown in FIG. 6 to their respective positions shown in FIG. 7, and the detection portion 56 detects that the cleaning holder 512 has reached the one end part of its movement path, and the linear member 54 is caused to stop travelling. Thereby, the cleaning holder 511 and the cleaning holder 512 stop moving.

Next, the motor 55 starts to rotate in an opposite direction, causing the linear member 54 to travel in the second direction (which is opposite to the first direction) indicated by arrow D2 (see FIG. 7). As a result, the cleaning holder 511 and the cleaning holder 512 move from their respective positions shown in FIG. 7 to their respective positions shown in FIG. 6, and the detection portion 56 detects that the cleaning holder 511 has reached the one end part of its movement path, and the linear member 54 is caused to stop travelling. Thereby, the cleaning holder 511 and the cleaning holder 512 stop operating.

FIG. 10 is a block diagram illustrating one example of a control path used in the image forming apparatus 1. Note that the image forming apparatus 1 is used with various controls executed on its various portions, and this results in a complex control path of the entire image forming apparatus 1. Hence, the description here will be focused on necessary part of the control path for implementation of the present disclosure.

A voltage control circuit 71, which is connected to a motor drive power supply 73, activates the motor drive power supply 73 in accordance with an output signal from the control portion 90. The motor drive power supply 73, in accordance with a control signal from the voltage control circuit 71, applies a predetermined drive voltage to the motor 55 disposed inside the optical scanning device 12.

In the operation portion 80, there are provided a liquid crystal display portion 81 and LEDs 82 that indicate various kinds of states, so as to indicate states of the image forming apparatus 1 and display conditions of image formation, how many sheets have been printed, etc. Various settings for the image forming apparatus 1 are made via a printer driver of the personal computer.

The control portion 90 at least includes a CPU (central processing unit) 91 as a central processor, a ROM (read-only memory) 92 which is a read-only storage portion, a RAM (random access memory) 93 which is a readable/writable storage portion, a timer 95, and an I/F (interface) 96 that transmits a control signal to various devices in the image forming apparatus 1 and receives an input signal from the operation portion 80.

The ROM 92 stores therein a control program for the image forming apparatus 1, data that stays unchanged during use of the image forming apparatus 1, such as numerical values necessary for controlling the image forming apparatus 1, and the like. The RAM 93 stores therein necessary data generated during control of the image forming apparatus 1, data temporarily required for controlling the image forming apparatus 1, and the like. The RAM 93 (or the ROM 92) further stores therein, for example, a voltage value (DUTY) applied to the motor 55 in each of later-described various operation modes of the cleaning holders 511 and 512 and a driving time of the motor 55 measured during cleaning of the transmissive members 52 of the optical scanning device 12, etc. The timer 95 measures the driving time of the motor 55.

According to the present embodiment, during the execution of the cleaning mode, when the detection portion 56 detects that one of the cleaning holders 511 and 512 has reached the one end part of its movement path, the linear member 54 is driven to start a forward travel operation, while, when the detection portion 56 detects that the other of the cleaning holders 511 and 512 has reached the one end part of its movement path, the linear member 54 is driven to start a backward travel operation. In other words, by the control portion 90 determining switching between the forward travel operation and the backward travel operation based on a detection result of the detection portion 56, it is possible to reduce load on the linear member 54 and to prevent the stretching pulleys 57 from being damaged.

Further, the first light blocking portion 511a and the second light blocking portion 512a have different shapes, and the second light blocking portion 512a has the through hole 512b. This enables the detection portion 56 to detect, on the basis of the pattern of light received by the light receiver 56b, which of the cleaning holders 511 and 512 has reached the one end part of its movement path. Thus, it is possible to simplify the detection portion 56 so as to reduce production cost of the optical scanning device 12.

Further, by forming the through hole 512b in the second light blocking portion 512a, it becomes easy to detect which of the cleaning holders 511 and 512 has reached the one end

Further, at the start of the execution of the cleaning mode, by setting the state where the cleaning holder 511 is disposed at the one end part of its movement path as the initial position, it is possible to have the detection portion 56 in the ON state so as to detect the cleaning holder 511. This makes it possible to prevent occurrence of an initial error in the cleaning process.

Further, on starting the execution of the cleaning mode, the control portion 90 determines, via the detection portion 56, which of the cleaning holders 511 and 512 is located at the one end part of its movement path, and decides which of the forward travel operation and the backward travel operation should be started. This enables a quick start-up of the cleaning operation no matter which of the cleaning holders 511 and 512 may be located at the one end part of its movement path when the previous execution of the cleaning mode is finished.

FIG. 11 and FIG. 12 are respectively a perspective view and a plan view illustrating a state where the detection portion 56 of the optical scanning device 12 according to the first embodiment is shielded from light by the first light blocking portion 511a. FIG. 13 is a sectional view (taken along line A-A of FIG. 12) as seen from the movement direction of the cleaning holder 511, illustrating a state where the detection portion 56 of the optical scanning device 12 according to the first embodiment is shielded from light by the first light blocking portion 511a.

As illustrated in FIG. 11, the detection portion 56 is disposed horizontally along the upper surface of the cover portion 12c such that longitudinal directions of the light emitter 56a and the light receiver 56b are parallel to the movement direction of the cleaning holder 511 (directions X1, X2). With this configuration, as compared to a case where the light emitter 56a and the light receiver 56b are disposed vertically, it is possible to reduce a protrusion amount of the detection portion 56 in its height direction and thus to achieve a reduced height (a lower profile) of the optical scanning device 12. On the other hand, with the above configuration, a distance from each of the light emitter 56a and the light receiver 56b to the upper surface of the cover portion 12c becomes short.

Further, as illustrated in FIG. 13, a gap is formed between the first light blocking portion 511a provided on the cleaning holder 511 and the upper surface of the cover portion 12c. This makes it possible to eliminate frictional resistance between the cleaning holder 511 and the upper surface of the cover portion 12c during movement of the cleaning holder 511 and thus to move the cleaning holder 511 smoothly.

As illustrated in FIG. 12 and FIG. 13, the first light blocking portion 511a of the cleaning holder 511 is disposed closer to the light emitter 56a than is a central part between the light emitter 56a and the light receiver 56b in a facing direction in which the light emitter 56a and the light receiver 56b face each other. Thus, with the first light blocking portion 511a of the cleaning holder 511 blocking an optical path between the light emitter 56a and the light receiver 56b, light emitted from the light emitter 56a passes through the gap between the first light blocking portion 511a and the cover portion 12c.

As a result, light having passed through the gap between the first light blocking portion 511a and the cover portion 12c may be reflected by the upper surface of the cover portion 12c to enter the light receiver 56b, leading to degradation in detection accuracy of the detection portion 56.

To prevent this, in the present embodiment, a light blocking rib 63 (a light leakage prevention portion) is formed on the upper surface of the cover portion 12c, which extends along the facing direction (directions Y1, Y2) of the light emitter 56a and the light receiver 56b of the detection portion 56, so as to be disposed in a region that faces a space between the light emitter 56a and the light receiver 56b. The light blocking rib 63 protrudes upward from the cover portion 12c substantially at the central part between the light emitter 56a and the light receiver 56b in the facing direction. In other words, the light blocking rib 63 protrudes on a side (a side of the light receiver 56b) that is opposite to the light emitter 56a with respect to the first light blocking portion 511a.

FIG. 14 is an enlarged view illustrating a positional relationship in height direction among the light emitter 56a, the first light blocking portion 511a, and the light blocking rib 63 in FIG. 13. As illustrated in FIG. 14, height h1 of the light blocking rib 63 from the upper surface of the cover portion 12c is set to be smaller than height h2 from the upper surface of the cover portion 12c to a lower end part of a light emitting region 56al of the light emitter 56a, and also to be equal to or greater than height h3 of the gap between the cover portion 12c and the first light blocking portion 511a. That is, height h1 of the light blocking rib 63 is determined so as to satisfy inequality (1) below:

$\begin{matrix} h 3 \leq h 1 < h 2. & (1) \end{matrix}$

When h3≤h1 is satisfied, the light blocking rib 63 is allowed to securely block light (indicated by a dashed-line arrow in FIG. 13) that has passed through the gap between the first light blocking portion 511a and the cover portion 12c to be reflected by the upper surface of the cover portion 12c. Further, when h1<h2 is satisfied, there is no risk of the light blocking rib 63 blocking the optical path from the light emitter 56a to the light receiver 56b.

Note that, when the cleaning holder 512 has reached the one end part of its movement path, the second light blocking portion 512a of the cleaning holder 512 is inserted closer to the light receiver 56b than is the central part between the light emitter 56a and the light receiver 56b in the facing direction. In this case as well, light reflected by the upper surface of the cover portion 12c is blocked by the light blocking rib 63, and thus there is no risk of light reflected by the upper surface of the cover portion 12c passing through the gap between the second light blocking portion 512a and the cover portion 12c to enter the light receiver 56b.

FIG. 15 is a plan view illustrating a configuration of and around a detection portion 56 of an optical scanning device 12 according to a second embodiment of the present disclosure. FIG. 16 is a sectional view illustrating a state where the detection portion 56 of the optical scanning device 12 according to the second embodiment is shielded from light by a first light blocking portion 511a, as seen from the movement direction of a cleaning holder 511. In the present embodiment, instead of the light blocking rib 63 of the first embodiment, a coarse surface portion 65 (a reflection suppression portion) is formed in an upper surface of a cover portion 12c so as to face a space between a light emitter 56a and a light receiver 56b.

The coarse surface portion 65 is such that fine irregularities are formed throughout such part of the cover portion 12c as faces the space between the light emitter 56a and the light receiver 56b, and has a lower reflectivity than other parts of the cover portion 12c. The coarse surface portion 65 is formed by processing the upper surface of the cover portion 12c by granulating (pear-skin) treatment. Light that has passed through the gap between the first light blocking portion 511a and the cover portion 12c (the light being indicated by the dashed-line arrow of FIG. 16) is reflected by the coarse surface portion 65 to become scattered light scattered in irregular directions. Thus, it is possible to suppress degradation of the detection accuracy of the detection portion 56 due to entry of light into the light receiver 56b after passing through the gap between the first light blocking portion 511a and the cover portion 12c.

FIG. 17 is a plan view illustrating a configuration of and around a detection portion 56 of an optical scanning device 12 according to a third embodiment of the present disclosure. FIG. 18 is a sectional view illustrating a state where a detection portion 56 of the optical scanning device 12 according to the third embodiment is shielded from light by a first light blocking portion 511a, as seen from a movement direction of a cleaning holder 511. In the present embodiment, instead of the coarse surface portion 65 of the second embodiment, a reflection suppression sheet 67 (a reflection suppression portion) is attached to the upper surface of a cover portion 12c so as to face a space between a light emitter 56a and a light receiver 56b.

The reflection suppression sheet 67 is formed of a material having a lower reflectivity than the cover portion 12c, and is attached and fixed to the cover portion 12c to entirely cover such part of the cover portion 12c as faces the space between the light emitter 56a and the light receiver 56b. Light that has passed through the gap between the first light blocking portion 511a and the cover portion 12c (the light being indicated by the dashed-line arrow of FIG. 18) enters the reflection suppression sheet 67 to become scattered light scattered in irregular directions. Thus, as in the second embodiment, it is possible to suppress degradation of the detection accuracy of the detection portion 56 due to entry of light into the light receiver 56b after passing through the gap between the first light blocking portion 511a and the cover portion 12c. As the reflection suppression sheet 67, for example, a sheet (a granulated sheet) formed by granulating a surface of a resin film such as a polycarbonate film or the like, an ND filter (a neutral density filter), or the like can be used.

Besides, the present disclosure may be implemented in any other manner than specifically described above as embodiments, and various modifications are possible within the scope of the invention. For example, each of the embodiments described above has dealt with the optical scanning device 12 including a pair of the cleaning holders 511 and 512 that are driven to reciprocate in mutually opposite directions by traveling of the linear member 54, but the present disclosure is equally applicable to an optical scanning device 12 including a single cleaning holder.

Further, each of the embodiments described above has dealt with a tandem-type color printer as an example of the image forming apparatus 1 incorporating the optical scanning device 12, but the present disclosure is applicable, not limited to color printers, also to electrophotographic image forming apparatuses provided with the optical scanning device 12, such as color copiers, monochrome printers, monochrome copiers, digital multifunction peripherals, facsimile machines, and the like.

The present disclosure is usable in optical scanning devices that form an electrostatic latent image by irradiating an image carrier with light. By using the present disclosure, it is possible to provide an optical scanning device capable of preventing degradation of detection accuracy and maintaining smooth movement of a cleaning holder in a case where a transmissive detection portion is used, and an image forming apparatus including such an optical scanning device.

OPTICAL SCANNING DEVICE AND IMAGE FORMING APPARATUS INCLUDING THE SAME

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