Optical scanning device and image forming apparatus including the same

An optical scanning device includes a mirror adjusting mechanism which includes an abutting surface and a mirror holding member. The abutting surface is provided with one or more first support protrusions making point contact or line contact with a reflecting surface of a planar mirror on the same straight line. The mirror holding member includes a mirror receiving part provided with one second support protrusion making point contact with the reflecting surface of the planar mirror. The mirror holding member is rotated while maintaining a contact state between the planar mirror and the first support protrusions and a contact state between the mirror receiving part and the abutting surface, so that an angle of the planar mirror is adjustable only in one direction by employing a straight line, which connects contact points between the plurality of first support protrusions and the planar mirror to each other, as a swing axis.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-088040 filed on Apr. 22, 2014, the entire contents of which are incorporated herein by reference.

BACKGROUND

The technology of the present disclosure relates to an optical scanning device that forms a latent image on a surface to be scanned by exposure scanning, and an image forming apparatus including the same such as a copy machine, a printer, a facsimile, and a multifunctional peripheral thereof.

Conventionally, in an optical scanning device used in an image forming apparatus, beam light emitted from a light source is deflected in a deflector such as a polygon mirror, is led to a photosensitive drum (an image carrying member) by passing through an optical member such as a lens, exposes and scans a surface of the photosensitive drum, and forms an electrostatic latent image thereon.

In such an optical scanning device, a sensor for detecting writing light is arranged in order to decide a writing position (a writing timing) of an image. A writing position is controlled such that after the writing light is incident into the detection sensor, an image is written after a predetermined time (several μseconds) passes. The writing light is reflected toward the detection sensor by a mirror. However, at this time, when an angle of the mirror in a sub-scanning direction is shifted, since the writing light is deviated in a vertical direction (the sub-scanning direction) of the detection sensor and is not detected, drawing is not started.

Conventionally, in order to correct a position of the writing light in the sub-scanning direction, a correcting lens is mounted. However, since the correcting lens is expensive as compared with general resin parts, it is preferable to employ a configuration with no correcting lens in order to enhance a cost-down effect by reducing parts. Therefore, particularly, when an optical path length from the mirror to the detection sensor is long, since the accuracy of a mirror angle has a large influence on shift of the writing light in the sub-scanning direction, there is a case in which a means for adjusting the mirror angle is necessary.

In this regard, there has been known various technologies for adjusting the mirror angle with a simple configuration. For example, there has been proposed a configuration for adjusting the mirror angle by allowing one end of the mirror to be brought into press-contact with a support point of a housing side by an elastic member and to directly press the other end of the mirror by an adjusting screw.

Furthermore, for example, there has been proposed a configuration for adjusting the mirror angle by mounting the mirror in a wedge-shaped mirror holding member and rotating the mirror holding member.

SUMMARY

An optical scanning device according to one aspect of the present disclosure includes a light source unit, a polygon mirror, a planar mirror, and a mirror adjusting mechanism. The light source unit emits beam light. The polygon mirror deflects and scans the beam light from the light source unit with respect to a surface to be scanned. The planar mirror changes an optical path of beam light reflected by the polygon mirror. The mirror adjusting mechanism adjusts an angle of the planar mirror. The mirror adjusting mechanism includes an abutting surface and a mirror holding member, and the mirror holding member includes a mirror pressing part and a mirror receiving part. The abutting surface is provided with one or more first support protrusions making point contact or line contact with a reflecting surface of the planar mirror on the same straight line. The mirror pressing part of the mirror holding member presses a first end side portion of the planar mirror to the first support protrusions. The mirror receiving part of the mirror holding member is provided with one second support protrusion facing a second end side portion of the reflecting surface of the planar mirror and making point contact with the reflecting surface of the planar mirror. The abutting surface is parallel to a straight line, which connects contact points between the plurality of first support protrusions and the planar mirror to each other, and is not parallel to a plane including contact points between the planar mirror and the plurality of first support protrusions/the second support protrusion. The mirror holding member is rotated while maintaining a contact state between the planar mirror and the first support protrusions and a contact state between the mirror receiving part and the abutting surface, so that an angle of the planar mirror is adjustable only in one direction by employing the straight line, which connects the contact points between the plurality of first support protrusions and the planar mirror to each other, as a swing axis.

DETAILED DESCRIPTION

Hereinafter, the present embodiment will now be described with reference to the drawings.FIG. 1is a schematic configuration diagram illustrating an entire configuration of an image forming apparatus1according to the present embodiment, and illustrates the right side as a front side of the image forming apparatus1. At a lower portion of an apparatus body1aof the image forming apparatus1(here, a monochrome printer), a paper feeding cassette2for accommodating loaded papers is disposed. Above the paper feeding cassette2, a paper conveyance path4is formed to extend substantially horizontally from the front side to the rear side of the apparatus body1a, to further extent upward, and to reach a paper discharge unit3formed on the upper surface of the apparatus body1a. Sequentially from an upstream side along the paper conveyance path4, a pick-up roller5, a feed roller6, an intermediate conveying roller7, a resist roller pair8, an image forming unit9, a fixing unit10, and a discharge roller pair11are disposed.

The paper feeding cassette2is provided with a paper loading plate12rotatably supported to the paper feeding cassette2. When papers loaded on the paper loading plate12have been sent toward the paper conveyance path4by the pick-up roller5and a plurality of papers have been simultaneously sent by the pick-up roller5, it is configured that the papers are loosened by the feed roller6and a retard roller13and only the uppermost one paper is conveyed. The papers sent to the paper conveyance path4are conveyed to the resist roller pair8by the intermediate conveying roller7by changing the conveyance direction to the rear side of the apparatus body1a, and are supplied to the image forming unit9by the resist roller pair8with its timing adjusted.

The image forming unit9forms a predetermined toner image on a paper by an electrophotographic process, and includes a photosensitive drum14serving as an image carrying member pivotally supported to be rotatable clockwise inFIG. 1, and a charging device15, a developing device16, a cleaning device17, a transfer roller18, and an optical scanning device19disposed in the vicinity of the photosensitive drum14, wherein the transfer roller18is disposed so as to face the photosensitive drum14while interposing the paper conveyance path4therebetween, and the optical scanning device19is disposed above the photosensitive drum14. Above the developing device16, a toner container20for refilling toner to the developing device16is disposed.

The charging device15includes a conductive rubber roller15aconnected to a power supply (not illustrated), wherein the conductive rubber roller15ais disposed so as to abut the photosensitive drum14. When the photosensitive drum14rotates, the conductive rubber roller15acontacts with the surface of the photosensitive drum14and is driven to rotate. At this time, a predetermined voltage is applied to the conductive rubber roller15a, so that the surface of the photosensitive drum14is uniformly charged.

Next, an electrostatic latent image based on input image data is formed on the photosensitive drum14by beam light emitted from the optical scanning device19, and toner is attached to the electrostatic latent image by the developing device16, so that a toner image is formed on the surface of the photosensitive drum14. Then, a paper is supplied from the resist roller pair8to a nip portion (a transfer position) between the photosensitive drum14and the transfer roller18at a predetermined timing, so that the toner image of the surface of the photosensitive drum14is transferred onto the paper by the transfer roller18.

The paper with the transferred toner image is separated from the photosensitive drum14and is conveyed toward the fixing unit10. The fixing unit10is disposed at a downstream side of the image forming unit9with respect to the paper conveyance direction, and the paper with the transferred toner image in the image forming unit9is heated and pressed by a heating roller21and a pressing roller22brought into press-contact with the heating roller21, which are provided in the fixing unit10, so that the toner image transferred onto the paper is fixed.

The image-formed paper is discharged to the paper discharge unit3by the discharge roller pair11. On the other hand, toner remaining on the surface of the photosensitive drum14is removed by the cleaning device17. The photosensitive drum14is charged again by the charging device15, and image formation is performed in the same manner.

FIG. 2is a perspective view of the optical scanning device19mounted in the image forming apparatus1. In addition,FIG. 2illustrates the state in which an upper lid of a housing has been removed in order to illustrate the inner structure of the optical scanning device19.

The optical scanning device19includes a light source unit33, a polygon mirror34serving as a rotating polygon mirror, a polygon motor39for rotationally driving the polygon mirror34, a scanning optical system35, a folding mirror36, a detection mirror37, and a detection sensor38. The light source unit33, the polygon mirror34, the polygon motor39, the scanning optical system35, and the folding mirror36are disposed in a housing31.

The light source unit33has a light source such as a laser diode for outputting laser light, and a cylindrical lens, a collimate lens and the like for shaping a beam diameter of the laser light, and outputs beam light modulated on the basis of image data input from a personal computer and the like (not illustrated).

The polygon mirror34is rotated by the polygon motor39at a predetermined speed, and deflects the beam light output from the light source unit33by using a reflective mirror surface provided at a side thereof. The polygon motor39is driven and controlled by a driver circuit provided in a circuit board40.

The scanning optical system35includes a plurality of lenses, and converts the beam light reflected by the polygon mirror34so as to be scanned at a constant speed, and forms an image of the beam light on a surface to be scanned. The folding mirror36reflects the beam light having passed through the scanning optical system35toward the lower side of the scanning optical system35, and leads the beam light to the photosensitive drum14(seeFIG. 1).

The detection sensor38outputs a signal for controlling an exposure range (a writing timing) of a main scanning direction, and receives the beam light (writing light) having passed through the scanning optical system35via the detection mirror37disposed out of the exposure range.

In the aforementioned configuration, the light source unit33outputs the beam light modulated on the basis of image data toward the polygon mirror34. The polygon mirror34reflects the beam light from the light source unit33, and deflects and scans the reflected light by the rotation thereof. The scanning optical system35converts the beam light reflected by the polygon mirror34into constant speed scanning light, and forms an image of the constant speed scanning light on the photosensitive drum14(seeFIG. 1) serving as a surface to be scanned via the folding mirror36. In this way, the optical scanning device19exposes and scans a predetermined range on the uniformly charged photosensitive drum14in the scanning direction, so that an electrostatic latent image in which charging has been attenuated is formed on the photosensitive drum14.

The housing31has a bottom surface portion31a, a side wall portion31brising from a peripheral edge of the bottom surface portion31a, and the upper lid (not illustrated) mounted on an upper edge of the side wall portion31b, and is formed in a predetermined shape by using resin. In a space formed by the bottom surface portion31a, the side wall portion31b, and the upper lid, the light source unit33, the polygon mirror34, the polygon motor39, the scanning optical system35, and the folding mirror36are accommodated. In order to reflect the beam light toward the photosensitive drum (seeFIG. 1) via an emission port (not illustrated) formed in the bottom surface portion31a, the folding mirror36is fixed to the bottom surface portion31aobliquely with respect to the bottom surface portion31aat a predetermined angle.

The detection mirror37and the detection sensor38are mounted at predetermined positions of the side wall portion31b. A detailed mounting structure of the detection mirror37will be described later.

The polygon mirror34is mounted at a rotating shaft of the polygon motor39, and the polygon motor39is fixed to the bottom surface portion31awhile interposing the circuit board40between the polygon motor39and the bottom surface portion31a. The circuit board40is provided with a driver IC and the like for controlling the rotation driving of the polygon motor39, and is fixed to the bottom surface portion31a. In addition, the circuit board40may be disposed at other parts of the bottom surface portion31a, or may be disposed at an upper portion of the housing31such as the upper lid.

FIG. 3is a perspective view of the vicinity (within a broken line circle ofFIG. 2) of a mirror adjusting mechanism50for adjusting an angle of the detection mirror37,FIG. 4is a perspective view illustrating a state in which the detection mirror37has been removed from the mirror adjusting mechanism50illustrated inFIG. 3, andFIG. 5is a perspective view illustrating a state in which the detection mirror37and a mirror holding member51have been removed from the mirror adjusting mechanism50illustrated inFIG. 3. With reference toFIG. 3toFIG. 5, a detailed configuration of the mirror adjusting mechanism50will be described. In addition, inFIG. 3, an arrow XX′ direction indicates the main scanning direction and an arrow YY′ direction indicates the sub-scanning direction.

The mirror adjusting mechanism50includes the detection mirror37, the mirror holding member51for holding the detection mirror37, and mirror holding member support portions55ato55cfor rotatably supporting the mirror holding member51.

The mirror holding member support portions55ato55care integrally formed with one another so as to protrude outward from the side wall portion31bof the housing31. A part surrounded by the mirror holding member support portions55ato55cof the side wall portion31bis an abutting surface57abutted by the mirror holding member51, and an opening60is formed in a substantially central portion of the abutting surface57. The beam light reflected by the polygon mirror34is incident into the detection mirror37via the opening60, and the beam light reflected by the detection mirror is incident into the detection sensor38(seeFIG. 2) via the opening60. Furthermore, below the opening60, first support protrusions61aand61bare formed to protrude outward from the abutting surface57. The mirror holding member support portion55cis formed on an inner side surface (an upper surface) thereof with a rack part63in which concave and convex portions are alternately continued.

The mirror holding member51is a substantially cylindrical member made of metal having a spring property (restorability), and has pressure-contact pieces65ato65cbrought into press-contact from the inside with the mirror holding member support units55ato55c. The pressure-contact piece65cbrought into press-contact with the mirror holding member support unit55cis provided with an engaging protrusion67engaged with the rack part63of the mirror holding member support unit55c. Furthermore, pressing parts69aand69bare formed between the pressure-contact pieces65aand65cand between the pressure-contact pieces65band65c, respectively.

A mirror pressing part70is formed closely above the pressure-contact piece65c. The mirror pressing part70presses the lower portion of a rear surface (a front side surface of a paper surface ofFIG. 4) of the detection mirror37, thereby pressing the lower portion of a reflecting surface (a back side surface of the paper surface ofFIG. 4) of the detection mirror37to the first support protrusions61aand61bof the abutting surface57. Furthermore, between the pressure-contact pieces65aand65b, a mirror receiving part is formed to hold the upper portion of the reflecting surface of the detection mirror37. In an inner surface side of the mirror receiving part71, a second support protrusion72having a hemispherical shape is arranged. The lower portion of the detection mirror37corresponds to a first end side portion of the planar mirror and the upper portion of the detection mirror37corresponds to a second end side portion of the planar mirror.

When the detection mirror37is mounted in the housing31, the upper portion of the reflecting surface of the detection mirror37is allowed to abut the mirror receiving part71of the mirror holding member51, and the lower portion of the rear surface of the detection mirror37is allowed to abut the mirror pressing part70of the mirror holding member51, so that the detection mirror37is set in the mirror holding member51.

Then, in the state in which the pressure-contact pieces65ato65care respectively allowed to face the mirror holding member support units55ato55c, the mirror holding member51is inserted into the part surrounded by the mirror holding member support portions55ato55cwhile the pressing parts69aand69bare being pressed by fingers. The mirror holding member51is inserted until the mirror holding member51abuts the abutting surface57and the lower portion of the reflecting surface of the detection mirror37abuts the first support protrusions61aand61b, so that the mounting of the detection mirror37to the housing31is completed.

When the detection mirror37is removed from the housing31, in the state in which the pressure-contact pieces65aand65bare bent inward to release pressure-contact to the mirror holding member support units55aand55b, the mirror holding member51is drawn out from the mirror holding member support units55ato55c, so that it is possible to remove the mirror holding member51and the detection mirror37from the housing31.

FIG. 6is a side sectional view (a sectional view taken along an arrow AA′ ofFIG. 3) of the mirror adjusting mechanism50taken along vertical line passing through a rotating axis0of the mirror holding member51, andFIG. 7is a plane sectional view (a sectional view taken along an arrow BB′ ofFIG. 3) of the mirror adjusting mechanism50taken along horizontal line passing through the vicinity of the first support protrusions61aand61b. A method for adjusting the angle of the detection mirror37will be described usingFIG. 6andFIG. 7while referring toFIG. 2toFIG. 4according to necessity. In addition, similarly toFIG. 3, an arrow XX′ direction indicates the main scanning direction and an arrow YY′ direction indicates the sub-scanning direction.

As illustrated inFIG. 6andFIG. 7, the detection mirror37is positioned with respect to the housing31at three points of the first support protrusions61aand61bformed on the abutting surface57, and the second support protrusion72formed on the mirror receiving part71of the mirror holding member51contacting with the abutting surface57. The abutting surface57is parallel to a straight line L (a straight line extending in the main scanning direction) connecting contact points P1and P2between the reflecting surface of the detection mirror37and the first support protrusions61aand61b. Furthermore, as illustrated inFIG. 6, the abutting surface57is inclined outward from the bottom to the top of the housing31, and is not parallel to a plane Q including the contact points P1and P2, and a contact point P3between the reflecting surface of the detection mirror37and the second support protrusion72. That is, the abutting surface57is an inclined surface inclined only in the sub-scanning direction while maintaining a parallel state with respect to the main scanning direction.

When the mirror holding member51is rotated counterclockwise while maintaining the contact state between the mirror receiving part71and the abutting surface57from the state ofFIG. 3, the mirror receiving part71of the mirror holding member51is also rotated counterclockwise about the rotating axis0so as to move below the abutting surface57. As a consequence, the second support protrusion72supporting the upper portion of the reflecting surface of the detection mirror37moves in an inner direction (broken line positions ofFIG. 6andFIG. 7) of the housing31along the inclination of the abutting surface57.

On the other hand, since the first support protrusions61aand61bsupporting the lower portion of the detection mirror37have been fixed to the abutting surface57, the positions of the contact points P1and P2do not change by the rotation of the mirror holding member51. Accordingly, the angle of the detection mirror37changes such that the detection mirror37falls down inside the housing31as indicated by a broken line ofFIG. 6. That is, since the detection mirror37swings by employing the straight line L of the main scanning direction, which connects the contact points P1and P2to each other, as a swing axis, and the angle of the detection mirror37in the main scanning direction does not change, the angle only in the sub-scanning direction changes.

According to the mirror adjusting mechanism50of the present embodiment, it is possible to change the angle of the detection mirror37only in the sub-scanning direction without changing the angle of the detection mirror37in the main scanning direction. Consequently, optical path adjustment of beam light only in the sub-scanning direction is possible without changing the incident timing of the beam light to the detection sensor38.

Furthermore, the mirror holding member51made of metal having a spring property is only configured to be fitted into the mirror holding member support units55ato55cformed on the outer side surface of the side wall portion31bof the housing31, so that it is possible to perform maintenance such as angle adjustment of the detection mirror37and exchange of the detection mirror37or the mirror holding member51without removing the upper lid of the housing31.

Furthermore, with the rotation of the mirror holding member51, the engaging protrusion67formed on the pressure-contact piece65cmoves in engagement with the rack part63, so that a worker has catching feeling (click feeling) and can recognize that the mirror holding member51has rotated only by a predetermined angle. Moreover, it is possible to hold the mirror holding member51after the adjustment so as not to be easily moved.

Other technologies of the present disclosure are not limited to the aforementioned embodiment, and various types of modification can be made without departing from the scope of the present disclosure. For example, in the aforementioned embodiment, the two first support protrusions61aand61bare allowed to abut the reflecting surface of the detection mirror37. However, three or more first support protrusions can also be provided such that abutting points with the detection mirror37are arranged in parallel to each other on the same straight line, or first support protrusions continued in a rib shape can also be provided. However, when the number of contact points between the first support protrusions and the detection mirror37increases (or they make line contact with each other), the dimension accuracy of the first support protrusions is required in order to highly accurately perform the positioning of the detection mirror37. Accordingly, as described in the present embodiment, it is preferable to employ a configuration in which the detection mirror37is supported at two points of the first support protrusions61aand61b.

Furthermore, the aforementioned embodiment has a configuration in which the mirror holding member51is rotated along the abutting surface57inclined outward from the bottom to the top of the housing31. However, an abutting surface57inclined inward from the bottom to the top of the housing31may also be used. It is sufficient if the inclination direction of the abutting surface57is decided in consideration of a die releasing direction when molding the housing31.

Furthermore, in the aforementioned embodiment, the mirror adjusting mechanism50for adjusting the angle of the detection mirror37for leading beam light to the detection sensor38has been described. However, the technology of the present disclosure is not limited thereto, and the mirror adjusting mechanism50may also be used as an adjusting mechanism of other mirrors disposed between the polygon mirror34and a surface to be scanned (the photosensitive drum14).

Furthermore, it is natural that the technology of the present disclosure can be applied to various image forming apparatuses provided with an optical scanning device, such as a monochrome copy machine, a digital multifunctional peripheral, a tandem or rotary type color printer or color copy machine, and facsimile, in addition to the monochrome printer as illustrated inFIG. 1.

The technology of the present disclosure can be used in an optical scanning device that forms an electrostatic latent image on a surface to be scanned by exposure scanning using a polygon motor, and an image forming apparatus including the same such as a copy machine, a printer, a facsimile, and a multifunctional peripheral thereof. When the technology of the present disclosure is used, it is possible to provide an optical scanning device capable of high accurately adjusting an angle only in one direction, in which the adjustment of a mirror angle is necessary, by using a simple configuration.