Leaf spring, housing, light scanning apparatus, and image forming apparatus

A leaf spring configured to mount an optical element to a housing, the housing containing: a rotary polygon mirror configured to deflect a laser beam emitted from a light source; and the optical element configured to guide the laser beam deflected by the rotary polygon mirror to a member to be scanned, wherein an adhesive is applied to the leaf spring, the adhesive being configured to adhere separated material scraped from the housing, the separated material being scraped from the housing by rubbing between the leaf spring and the housing at a time of mounting the optical element to the housing.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a leaf spring, a housing, a light scanning apparatus, and an image forming apparatus.

Description of the Related Art

As a light scanning apparatus to be used in an electrophotographic image forming apparatus, a light scanning apparatus having the following configuration is well known. Specifically, there has been known a light scanning apparatus configured to form a latent image on a photosensitive member by deflecting a light beam emitted from a light source with a rotary polygon mirror and guiding the deflected light beam onto a photosensitive surface of the photosensitive member with optical components such as a lens and a mirror.

Inside the light scanning apparatus, there is provided a deflector including the rotary polygon mirror for performing deflection scanning with laser beams guided from a semiconductor laser, for example, the rotary polygon mirror. This forms a mechanism in which the semiconductor laser is repeatedly turned on and off in accordance with operation of a photosensitive drum while laser beams are scanned on the photosensitive drum to obtain a desired latent image.

Normally, optical components forming such a mechanism are stored in a housing so as to be protected from dart-causing substances. However, there has been a problem in that the housing is scraped off by the operation of mounting a variety of components to generate a separated material separated from the housing and the separated material adheres to the optical component. In order to deal with this problem, for example, there has been proposed a technology of collecting the separated material and the like with use of an adhesive applied onto the bottom surface and the side surface of the housing (Japanese Patent Application Laid-Open No. H06-148550).

In the related art, however, the adhesive is applied almost throughout the bottom surface and the side wall inside the housing except a circuit board for driving a polygon mirror. That is, the related art has the problem in that the adhesive is to be extensively applied onto places to which the separated material may move.

SUMMARY OF THE INVENTION

The present invention has been made in such circumstances, and an object of the present invention is to collect a separated material with use of a smaller amount of adhesive than in the related art.

In order to solve the above-mentioned problem, according to one embodiment of the present invention, there is provided a leaf spring configured to mount an optical element to a housing, the housing containing: a rotary polygon mirror configured to deflect a laser beam emitted from a light source; and the optical element configured to guide the laser beam deflected by the rotary polygon mirror to a member to be scanned, wherein an adhesive is applied to the leaf spring, the adhesive being configured to adhere separated material scraped from the housing, the separated material being scraped from the housing by rubbing between the leaf spring and the housing at a time of mounting the optical element to the housing.

DESCRIPTION OF THE EMBODIMENTS

Now, embodiments of the present invention are described in detail with reference to the drawings. In the following description, a rotation axis direction of a rotary polygon mirror42of a deflector43, which is to be described later, is defined as a Z-axis direction, a main scanning direction, which is a scanning direction of a light beam, or a longitudinal direction of optical lenses and reflection mirrors62, which are to be described later, is defined as a Y-axis direction, and a direction orthogonal to a Y axis and a Z axis is defined as an X-axis direction.

<Configuration of Image Forming Apparatus>

The configuration of an image forming apparatus according to a first embodiment of the present invention will be described.FIG. 1is a schematic structural view for illustrating an entire configuration of a tandem type color laser beam printer of the first embodiment. The laser beam printer (hereinafter referred to simply as “printer”) includes four image forming engines10Y,10M,10C, and10Bk (indicated by the dashed-dotted lines) configured to form toner images for respective colors of yellow (Y), magenta (M), cyan (C), and black (Bk). Further, the printer includes an intermediate transfer belt20serving as an intermediate transfer member onto which a toner image is transferred from each of the image forming engines10Y,10M,10C, and10Bk. The toner images multiply transferred onto the intermediate transfer belt20(intermediate transfer member) are configured to be transferred onto a recording sheet P serving as a recording medium so that a full-color image is formed. In the following, unless otherwise necessary, the reference symbols Y, M, C, and Bk indicating the colors are omitted.

The intermediate transfer belt20is formed into an endless shape and is carried over a pair of belt conveyance rollers21and22so that a toner image formed by each image forming engine10is transferred onto the intermediate transfer belt20while the intermediate transfer belt20is rotating in a direction indicated by the arrow H. Further, a secondary transfer roller65serving as a second transfer member is provided at a position opposed to one belt conveyance roller21across the intermediate transfer belt20. The recording sheet P is inserted between the secondary transfer roller65and the intermediate transfer belt20that are held in press-contact with each other, with the result that a toner image is transferred onto the recording sheet P from the intermediate transfer belt20. The four image forming engines10Y,10M,10C, and10Bk described above are arranged in parallel on a lower side of the intermediate transfer belt20so that a toner image formed in accordance with image information of each color is transferred onto the intermediate transfer belt20(hereinafter referred to as “primary transfer”). The four image forming engines10are arranged in the following order: the image forming engine10Y for yellow, the image forming engine10M for magenta, the image forming engine10C for cyan, and the image forming engine10Bk for black in a rotation direction (direction indicated by the arrow H) of the intermediate transfer belt20.

Further, a light scanning apparatus40configured to expose a photosensitive drum (photosensitive member)50to light in accordance with image information is provided below the image forming engines10, the photosensitive drum50being a member to be scanned that is included in each image forming engine10. The light scanning apparatus40is shared by all of the image forming engines10Y,10M,10C,10Bk and includes four semiconductor lasers serving as light sources (not shown) configured to emit laser beams (light beams) that are each modulated in accordance with image information of each color. Further, the light scanning apparatus40includes a rotary polygon mirror unit (hereinafter referred to as “deflector”)43that rotates at a high speed to perform scanning with laser beams of the four optical paths along the direction of the rotary shaft of the photosensitive drum50(FIG. 2B). Each laser beam used in scanning by the deflector43travels along a predetermined route while being guided by an optical element mounted in the light scanning apparatus40. Each laser beam having traveled along the predetermined route exposes each photosensitive drum50of each image forming engine10through a dustproof glass142(FIG. 2B) that is an irradiation port provided on the top of the light scanning apparatus40.

Further, each image forming engine10includes the photosensitive drum50and a charging roller12configured to charge the photosensitive drum50to a uniform background potential. Further, each image forming engine10includes a developing device (developing unit)13configured to form a toner image by developing an electrostatic latent image formed on the photosensitive drum50(member to be scanned) by exposure to the laser beam. The developing device13forms a toner image in accordance with image information of each color on the photosensitive drum50serving as the photosensitive member. The developing device13has a system using a two-component developer with a toner and a carrier mixed therein. The developing device13is supplied with the developer having the toner and the carrier mixed therein from a supply cartridge (not shown) so as to omit maintenance of replacing the developer due to a temporal change. For the developing device13, a development system to automatically discharge a degraded developer is used.

A primary transfer roller15serving as a first transfer member is provided at a position opposed to the photosensitive drum50of each image forming engine10across the intermediate transfer belt20. When a predetermined transfer voltage is applied to the primary transfer roller15, a toner image on the photosensitive drum50is transferred onto the intermediate transfer belt20.

Meanwhile, the recording sheet P is supplied from a feed cassette2housed in a lower portion of a printer housing1to an inner portion of the printer, specifically a secondary transfer position at which the intermediate transfer belt20and the secondary transfer roller65come into abutment with each other. In an upper portion of the feed cassette2, a pickup roller24configured to pull out the recording sheet P contained in the feed cassette2and a feed roller25are arranged in parallel. Further, a retard roller26configured to prevent overlap feeding of the recording sheet P is provided at a position opposed to the feed roller25. A conveyance route27of the recording sheet P inside the printer is provided substantially vertically along a right side surface of the printer housing1. The recording sheet P pulled out from the feed cassette2positioned in a bottom portion of the printer housing1ascends through the conveyance route27and is sent to registration rollers29configured to control an entry timing of the recording sheet P with respect to the secondary transfer position. After that, a toner image is transferred onto the recording sheet P at the secondary transfer position, and then the recording sheet P is sent to a fixing device3serving as a fixing unit (indicated by the broken line) provided on a downstream side in the conveyance direction. An unfixed toner image on the sheet P (recording medium) is fixed onto the sheet P by the fixing device3. The recording sheet P having the toner image fixed thereonto by the fixing device3is discharged to a discharge tray1aprovided on the top of the printer housing1through discharge rollers28.

In formation of a full-color image by the color laser beam printer configured as above, first, the light scanning apparatus40exposes the photosensitive drum50of each image forming engine10to light at predetermined timing in accordance with image information of each color. With this, a latent image in accordance with the image information is formed on the photosensitive drum50of each image forming engine10. In order to obtain an image of good quality, the latent image formed by the light scanning apparatus40needs to be reproduced with accuracy at a predetermined position on the photosensitive drum50.

<Configuration of Light Scanning Apparatus>

FIG. 2Ais a view illustrated so as to make the inside of a housing105visible by removing a cover70(FIG. 2B), and is a view for illustrating a configuration of the first embodiment. In the inside and the outer periphery of the light scanning apparatus40, a light source unit51, in which a light source configured to emit a light beam is mounted, and the deflector43, which is configured to reflect and deflect a light beam, are provided. Further, in the inside of the light scanning apparatus40, an optical lens60(60ato60d) and a reflection mirror62(62ato62h) that are needed for guiding a light beam to the surface of the photosensitive drum50to form an image are provided.

The light beams deflected by the rotary polygon mirror42are configured to pass through first optical lenses60aand60chaving strong power in the main scanning direction (Y-axis direction) and then be guided to second optical lenses60band60dhaving strong power in a sub scanning direction (X-axis direction). The light beams having passed through the first optical lenses60aand60cand the second optical lenses60band60dare each reflected at least once by the reflection mirror62and guided to the photosensitive drum50being the member to be scanned to form an image.

FIG. 2Bis a schematic view for illustrating an entire image of mounting of the optical components. The light scanning apparatus40includes the housing105and the cover70for covering an opening at the top of the housing105. In the inside and the outer periphery of the light scanning apparatus40, the light source unit51, in which the light source configured to emit a light beam is mounted, and the deflector43, which includes a motor unit41and the rotary polygon mirror42, and is configured to deflect a light beam, are provided. Further, in the light scanning apparatus40, the plurality of optical lenses60(60ato60d) and the plurality of reflection mirrors62(62ato62h) for guiding each of light beams to the top of the photosensitive drum50to form an image are provided. The housing105has a mounted surface, on which the deflector43is mounted, and a support surface, on which a support portion configured to support at least one reflection mirror of the reflection mirrors62ato62his formed, and which is located closer to the photosensitive drum50(photosensitive member) than the rotary polygon mirror42.

A light beam LY corresponding to a photosensitive drum50Y emitted from the light source unit51is deflected by the rotary polygon mirror42and enters the optical lens60a. The optical lens60ais an optical element that the light beam LY enters first among the lenses and the mirrors arranged on the optical path of the light beam LY. An optical axis of the optical lens60ais in a direction substantially parallel to the X axis illustrated inFIG. 1. The light beam LY having passed through the optical lens60aenters the optical lens60b, and passes through the optical lens60bto be reflected by the reflection mirror62a. The light beam LY reflected by the reflection mirror62ascans the photosensitive drum50Y through a dustproof glass142Y.

A light beam LM corresponding to a photosensitive drum50M emitted from the light source unit51is deflected by the rotary polygon mirror42and enters the optical lens60a. The optical lens60ais an optical element that the light beam LM enters first among the lenses and the mirrors arranged on the optical path of the light beam LM. The light beam LM having passed through the optical lens60aenters the optical lens60b, and passes through the optical lens60bto be reflected by the reflection mirrors62b,62c, and62d. The light beam LM reflected by the reflection mirror62dscans the photosensitive drum50M through a dustproof glass142M.

A light beam LC corresponding to a photosensitive drum50C emitted from the light source unit51is deflected by the rotary polygon mirror42and enters the optical lens60c. The optical lens60cis an optical element that the light beam LC enters first among lenses and the mirrors arranged on the optical path of the light beam LC. An optical axis of the optical lens60cis in a direction substantially parallel to the X axis illustrated inFIG. 1. The optical lens60aand the optical lens60cin the light scanning apparatus of the first embodiment are provided in the housing105such that the optical axis of the optical lens60cand the optical axis of the optical lens60aare parallel to each other. The light beam LC having passed through the optical lens60centers the optical lens60d, and the light beam LC having passed through the optical lens60dis reflected by the reflection mirrors62e,62f, and62g. The light beam LC reflected by the reflection mirror62gscans the photosensitive drum50C through a dustproof glass142C.

A light beam LBk corresponding to the photosensitive drum50Bk emitted from the light source unit51is deflected by the rotary polygon mirror42and enters the optical lens60c. The optical lens60cis an optical element that the light beam LBk enters first among the lenses and the mirrors arranged on the optical path of the light beam LBk. The light beam LBk having passed through the optical lens60centers the optical lens60d, and passes through the optical lens60dto be reflected by the reflection mirror62h. The light beam LBk reflected by the reflection mirror62hscans the photosensitive drum50Bk through a dustproof glass142Bk.

<Optical Path of Laser Beam>

FIG. 3is a schematic view for illustrating an optical path of a laser beam emitted from a semiconductor laser52to the rotary polygon mirror42. In the inside of the light scanning apparatus40, the light source unit51, the rotary polygon mirror42, a cylindrical lens55, the optical lens60, the reflection mirror62, and the like are provided.

The light source unit51includes the semiconductor laser52, a collimator lens53, and a diaphragm54, and diffused light emitted from the semiconductor laser52is converted to parallel light by the collimator lens53. A Laser beam emitted from the light source unit51is collected on the rotary polygon mirror42by the cylindrical lens55. As described above, the light beams deflected by the rotary polygon mirror42, are configured to pass through the first optical lenses60aand60chaving strong power in the main scanning direction and then be guided to the second optical lenses60band60dhaving strong power in the sub scanning direction. The light beam reflected by the reflection mirror62passes through the dustproof glass142provided on the cover70and is guided to the photosensitive drum50being the member to be scanned, to form an image.

The reflection mirror62is fixed to the housing105with use of a leaf spring702(FIG. 4B). The leaf spring702is configured so as to urge the reflection mirror62in two directions, namely, a normal direction and a transverse direction of a reflection surface of the reflection mirror62, while not urging the reflection mirror62in a longitudinal direction of the reflection surface of the reflection mirror62. With such a configuration, the reflection mirror62is prevented from being deformed due to a difference in linear expansion between the housing105and the reflection mirror62at the time of a temperature rise.

The leaf spring702being an elastic member illustrated inFIG. 4Ais formed by bending one thin plate. The leaf spring702has a first plate portion702h, which is a plate portion having a reference surface702a, and a second plate portion727being a second arm portion, a third plate portion702jbeing a first arm portion, and a pair of fourth plates702k, which are separately bent with respect to the first plate portion702h.

The first plate portion702his a contact portion that is in contact with a protruding portion633(FIG. 4Bdescribed later) being a second support portion described later and receives repulsing force from the protruding portion633. The first plate portion702hand the second plate portion727are coupled by a bent portion702p. The bent portion702pis formed by folding the second plate portion727from one end of the first plate portion702htoward the first plate portion702hto form a substantially V shape. Then, the bent portion702pis elastically deformed to change the relative positional relationship (relative angle) between the first plate portion702hand the second plate portion727. The second plate portion727extends toward the other end side of the first plate portion702hon the opposite surface to the reference surface702a. The first plate portion702hand the third plate portion702jare coupled to each other by a bent portion702o. The bent portion702ois formed by bending the third plate portion702jat substantially a right angle to the first plate portion702h, and the bent portion702ois elastically deformed to change the relative positional relationship (angle) between the first plate portion702hand the third plate portion702j. The pair of fourth plates702kare bent at substantially a right angle from both lateral ends of the first plate portion702hto the opposite side to the second plate portion727and the third plate portion702j.

The reference surface702ais one surface of the thin plate-like first plate portion702hand abuts against a spring reception surface736of the protruding portion633provided in the housing105to serve as a reference of the position of the leaf spring702(FIG. 4B). A first press portion704for pressing the reflection mirror62is formed in the second plate portion727. The first press portion704is a portion that is bent convexly so as to protrude at the end portion of the second plate portion727to the opposite side to the first plate portion702h. The second plate portion727and the first plate portion702hof the leaf spring702are inserted between the reflection mirror62and the protruding portion633under a deflected (shrunk) state against elastic force so that the first press portion704abuts against a mirror reflection surface706(FIG. 4B) of the reflection mirror62. The mirror reflection surface706is a surface at which a light beam enters the reflection mirror62. With this configuration, the first press portion704presses the reflection mirror62toward a first mirror bearing surface707being a second contact portion of a mirror support portion631that is a first support portion described later (FIG. 4B). The first mirror bearing surface707is in contact with a second surface parallel to the mirror reflection surface706of the reflection mirror62.

A second press portion705for pressing the reflection mirror62is formed in the third plate portion702j. The second press portion705being the press portion is a portion in a dogleg shape formed by bending an end portion702dof the third plate portion702jin a direction to the second plate portion727and further bending the end portion702dat substantially a right angle in the opposite direction to the second plate portion727. A part of the third plate portion702j, the portion of the third plate portion702jthat is bent at an obtuse angle, and a part of the second press portion705form a second press arm729. The second press portion705abuts against a mirror flat surface710being a predetermined surface of the reflection mirror62(FIG. 4B). The leaf spring702is locked to the protruding portion633while the third plate portion702jof the leaf spring702is deflected with respect to the first plate portion702hagainst elastic force. With this configuration, the second press portion705elastically presses the reflection mirror62to a second mirror bearing surface709that is a first contact portion of the mirror support portion631being a support portion (FIG. 4B). The second mirror bearing surface709is in contact with a first surface parallel to the mirror flat surface710(the rear surface of the first surface) of the reflection mirror62.

A hole portion713is an opening provided on the reference surface702aand penetrates the first plate portion702hbetween the front and rear surfaces thereof. In the hole portion713, an engagement portion733(leaf spring-side engagement portion) is formed of a part of the first plate portion702hthat forms the hole portion713, the engage portion733being engaged with an engagement portion703(housing-side engagement portion) of the protruding portion633. The first plate portion702hhas protruding flat portions722and724protruding on both sides between the pair of fourth plates702kand the bent portion702othat is folded toward the third plate portion702j. Further, the first plate portion702hhas protruding flat portions723and725protruding on both sides between the pair of fourth plates702kand the bent portion702pthat is folded toward the second plate portion727. The end portions of the protruding flat portions723and725are bent to the opposite side to the second plate portion727to form stoppers734and735. The stoppers734and735abut against a surface (not shown) of the protruding portion633. Thus, even when the pressing of the leaf spring702onto the guide surface by a jig described later is not released with some cause, the leaf spring702can be prevented from moving down.

As thus described, the leaf spring702is configured so as to engage the engagement portion733formed in the leaf spring702itself to the engagement portion703provided in the housing105. With this configuration, the leaf spring702can hold its posture without falling off the housing105due to the repulsing force from the reflection mirror62. Although symbols of the respective portions of the leaf spring702are shown inFIG. 4A, detailed symbols of the leaf spring702are omitted in the other drawings for easiness to see the drawings. The shape of the leaf spring according to the first embodiment is not limited to the shape ofFIG. 4A.

<Configuration of Spring Support Member and Mirror Support Member>

As illustrated inFIG. 4B, the protruding portion633and the mirror support portion631are integrally molded inside the housing105, the protruding portion633being a leaf spring support portion configured to support the leaf spring702, the mirror support portion631supporting the reflection mirror62for accurately mounting the reflection mirror62to the housing105. The protruding portion633is a gap forming portion configured to form a gap with respect to the reflection mirror62supported on the mirror support portion631described later. In the Y-axis direction of the protruding portion633, a Y-axial width of the protruding portion633is formed in the housing105so as to be slightly narrower than the pair of fourth plates702kof the leaf spring702. The protruding portion633is inserted between the pair of fourth plates702kwhen the leaf spring702is inserted between the reflection mirror62and the protruding portion633from a +Z-axis direction to perform the function of guiding the leaf spring702. Further, the spring reception surface736of the protruding portion633is in contact with the reference surface702aof the leaf spring702when the leaf spring702is engaged with the engagement portion703of the housing105.

The mirror support portion631has the first mirror bearing surface707and the second mirror bearing surface709that abut against the reflection mirror62pressed by the first press portion704and the second press portion705of the leaf spring702. The first mirror bearing surface707supports the rear surface side of the mirror reflection surface706against a pressed point in the reflection mirror62that is pressed by the first press portion704of the leaf spring702. A process for mounting the leaf spring702to the housing105is described later with use ofFIG. 11A,FIG. 11B, andFIG. 11C.

At the time of fixing the reflection mirror62mounted on the mirror support portion631with use of the leaf spring702, the housing105may be scraped off by the leaf spring702to generate a separated material. The separated material is a material separated from the housing when the housing is scraped off due to mounting operation for a variety of components. The separated material is made of the same material as the housing105because the separated material is generated by the housing105being scraped off. The housing105in the first embodiment contains, for example, polyphenylene ether (PPE) and polystyrene resin (PS). Further, a specific gravity of the resin used for the housing105of the first embodiment is, for example, 1.36 g/cm3. Typically, a resin having almost a similar specific gravity is used for the housing.

In the first embodiment, a collecting portion (a catching portion) configured to collect (catch) the separated material is formed by applying an adhesive onto the leaf spring702. That is, the leaf spring702itself becomes the collecting portion. A method of applying the adhesive onto the leaf spring702involves, for example, immersing the leaf spring702into an adhesive solution and then pulling up the leaf spring702for drying. Thus, the adhesive is applied onto the entire leaf spring702to form the collecting portion. As indicated by dots inFIG. 4C, the adhesive500is applied on the entire leaf spring702. When a plurality of kinds of leaf springs are used for one housing105, a collecting portion is desirably provided by applying the adhesive to all of the leaf springs. However, the leaf spring702provided with the collecting portion may be used as particularly limited to some leaf springs in the case of fixing an optical component with a small spot diameter on the surface, for example.

<Verification of Influence on Image by Separated Material>

At the time of mounting the reflection mirror62to the housing105with use of the leaf spring702, a separated material is generated due to rubbing between the leaf spring702and the housing105.FIG. 5is a graph for showing a size of a separated material being a separated material on the optical component and a density difference between an image with a density to be essentially formed and a white streak generated due to the separated material in each of a plurality of light scanning apparatus with different placement of the optical components. InFIG. 5, a horizontal axis indicates the size (mm) of the separated material, and a vertical axis indicates the density difference. The density difference is a difference between a density of an image in which a latent image is formed by a laser beam having passed through a region without a separated material and a density of a region in which a latent image is formed by a laser beam having passed through a region with a separated material. A broken line at the density difference of 4 indicates a permissible value of the density difference such that a white streak is easily viewed when the density difference is not smaller than 4 and a white streak cannot be viewed when the density difference falls below 4. A, B, and C inFIG. 7indicate different light scanning apparatus referred to as a product A, a product B, and a product C in the following.

FIG. 6is a diagram for illustrating a light-shielding chart provided on the dustproof glass142. Symbols G to L above the dustproof glass142denote light-shielding parts corresponding to separated materials with different sizes, and light-shielding portions with six sizes from a line width of from 50 μm to 300 μm are provided in the main scanning direction at an interval of 50 μm.FIG. 7is obtained by assembling the dustproof glass142provided with such a light-shielding chart to each of the product A, the product B, and the product C to form images with different densities (hereinafter also referred to as “test charts”). White streaks are generated on the test charts due to the light-shielding parts corresponding to separated materials. The largest difference between a white streak part (hereinafter referred to as “white streak portion”) and a black part at each gradation in an image is used as a density difference.

In measurement for evaluating the test charts ofFIG. 7, ES-1000G (Seiko Epson Corporation) was used as an image reader. The evaluation was performed on measurement conditions of 256-level (8-bit) grayscale, a 300-dpi resolution, and a black image. InFIG. 7, for example in the product A, 16 densities out of densities of the 256 gradations are extracted and a density difference between the black image and the white streak portion at each gradation is measured. There are six points of light-shielding parts corresponding to the separated materials with different sizes at each density as illustrated inFIG. 6, and hence density differences are measured at a total of 96 points. Then, six points at a gradation with the largest density difference among the measured 96 points are plotted in the graph ofFIG. 5. The same applies to the product B and the product C. As seen fromFIG. 5, in any one of the products, the density difference falls below 4, which is a permissible value for the density difference, when the separated material has a size of smaller than 100 μm, and hence the white streak is hardly viewed. For this reason, the adhesive to be used needs to have adhesive force by which a separated material with a size of not smaller than 100 μm can be collected.

FIG. 8is a graph obtained by normalizing the graph ofFIG. 5by taking a laser spot diameter into consideration. The position of an optical element differs and the spot diameter on the optical element differs depending on the product, and hence a horizontal axis indicates an area occupancy of the separated material, which is an area of the separated material with respect to an area of the spot on the optical element. The optical element is an element corresponding to the dustproof glass142in the first embodiment. A vertical axis and a broken line at the density difference of 4 inFIG. 8are the same as those inFIG. 5. The separated material with a size of not smaller than 100 μm, which was a target in the first embodiment, corresponds to dimensions of about 1% of the spot diameter on the optical element. That is, the optical element is not limited to the dustproof glass142, and an image defect can be prevented as long as a separated material corresponding to the dimensions of about 1% of the spot diameter on the optical element can be collected.

The adhesive force of the collecting portion is set from the dimensions of the separated material mounted thereto. In the first embodiment, the adhesive force of the collecting portion was set so that the separated material does not fall when one 0.19-mg piece of the same material as that of the housing105is placed on the collecting portion (leaf spring) without pressurization, and the collecting portion is turned upside-down such that a self-weight of the separated material is directed in a peeling direction from the collecting portion. In the material for the housing105, this is a mass with which a diameter of the separated material is 642 μm on the assumption of the separated material being a sphere, and is sufficient adhesive force for collecting the separated material with a size of 100 μm that causes an image defect. At the same time, this is adhesive force not to impair the sliding properties of the housing105and the leaf spring702and not to affect the assembling property. In addition, many of separated materials that can be generated in an assembly process of the light scanning apparatus40have sizes of not larger than 400 μm. A separated material with a size of 400 μm is easily found by visual observation, and for example when the separated material is visually observed at the time of assembly, an operator can perform the operation of removing the separated material with use of a blower or the like.

Herein, the shape of the separated material that adheres to the adhesive of the leaf spring702is assumed to be a sphere. The shape of the connecting portion between the leaf spring702and the separated material is assumed to be a circle. Further, a radius “r” of the circle being the contact portion at the time when the separated material comes into contact with the leaf spring702is assumed to be 1% of a radius R of the separated material assumed to be the sphere (r=0.01×R). For example, when the radius of the separated material is 200 μm, the radius “r” of the circle being the contact portion between the leaf spring702and the separated material is 2 μm, which is 1% of 200 μm. A lower limit of the adhesive force (N/μm2) per unit area of the adhesive is obtained as follows. First, assuming that a density of the separated material, namely, the material forming the housing105, is ρ (kg/μm3), a mass Md (kg) of the separated material is obtained from the following expression (1):
Md=4/3×π×R3×ρ  (1),
where π is a circumference ratio. A weight Fg (N) that acts when the collecting portion is turned upside-down such that the self-weight of the separated material is directed in the peeling direction from the collecting portion is obtained from the next formula (2):
Fg=Md×g=4/3×π×R3×ρ×g(2),
where “g” is a gravitational acceleration (=9.8 m/s2=9.8×106μm/s2).

An area Sc (μm2) of the contact portion is obtained from the next formula (3):
Sc=π×r2(3).
From the above, a lower limit of an adhesive force F (N/μm2) per unit area of the adhesive is obtained from the following formula (4):

F=⁢4/3×(200)3/(2)2×1.36×10-15×9.8×106≈⁢35.5×10-3⁢⁢N⁢/⁢µm2.
In such a manner as above, the lower limit of the adhesive force F per unit area of the adhesive is obtained.

<Material for Adhesive of Collecting Portion>

For the adhesive to be applied onto the leaf spring702, for example, an acrylic ester type substance is preferably used. For the adhesive in the first embodiment, an acrylic ester type copolymer mixture is used. The material used as the adhesive to be applied onto the leaf spring702is not limited to the material described above, but may be a substance that holds stickiness without being cured after applied onto the leaf spring702. As thus described, according to the first embodiment, it is possible to collect a separated material that is generated at the time of assembly in the source of generation of the separated material.

In the first embodiment, the adhesive has been applied onto the leaf spring702to form the collecting portion, but in a second embodiment of the present invention, a configuration in which the collecting portion is provided on the housing105side is described. A collecting portion111is provided in the housing105. The collecting portion111is formed by applying an adhesive for optical use onto the surface of the housing105and drying the adhesive. In a related-art product, there has been an example in which a drying lubricant is applied between the reflection mirror62and the leaf spring702, but this has no stickiness and thus no function of collecting the separated material.

FIG. 9AandFIG. 9Bare views for illustrating a region in which the collecting portion111is provided on the housing105. As indicated by dots inFIG. 9AandFIG. 9B, the collecting portion111comprises adhesive500applied on the protruding portion633.FIG. 9Ais a view for illustrating a state in which the reflection mirror62is mounted to the housing105with use of the leaf spring702.FIG. 9Bis a view obtained by removing the reflection mirror62and the leaf spring702fromFIG. 9Aso as to improve the visibility of the collecting portion111provided in the protruding portion633. The collecting portion111is provided on the surface of the housing105, and is provided in a region in which the collecting portion111slides with the leaf spring702when the leaf spring702is inserted. That is, the collecting portion111of the second embodiment is provided in the protruding portion633configured to support the leaf spring702.FIG. 10is a top view ofFIG. 9Aseen from a +Z direction.FIG. 11A,FIG. 11B, andFIG. 11Care views for illustrating a mounting process of the leaf spring702, as well as sectional views along the line XI-XI ofFIG. 10described later. InFIG. 11A, the leaf spring702inserted from above (+ side of the Z direction) is elastically deformed and gets over the engagement portion703(FIG. 11A). Thereafter, the elastic deformation is released and the engagement portion733of the leaf spring702is hooked on the engagement portion703so as to prevent falling of the leaf spring702(snap fit system) (FIG. 11B). The leaf spring702is inserted downward inFIG. 11Cunder a state in which the force generated by the elastic deformation acts between the housing105and the leaf spring702(FIG. 11C). As a result, the housing105is scraped off to generate a separated material, but as illustrated inFIG. 9B, the separated material is collected in a collecting portion111f. As a result, the separated material does not move in the housing105.

Further, in the snap fit system, a clearance between the leaf spring702and the housing105is large and the posture of the leaf spring702at the time of insertion varies, and thus the bent portion702pbeing an edge portion of the leaf spring702may slide with the housing105to generate a separated material. Similarly, however, the separated material is collected by the collecting portion111. In the second embodiment, the pair of fourth plates702kof the leaf spring702may slide with the housing105. However, the separated material is collected by a collecting portion111c. Further, the collecting portion111may be provided in such a position as collecting portions111a,111b,111d, and111eas illustrated inFIG. 9A.

Although one leaf spring702has been focused and described in the second embodiment, a plurality of leaf springs are typically provided in the housing105. When the collecting portion is provided with respect to the protruding portion being a support portion of each of all the leaf springs, the frequency of generation of the image defect can be further reduced. The collecting portion may be provided in any one of the housing105and the leaf spring702, or may be provided in both of the housing105and the leaf spring702. As thus described, according to the second embodiment, it is possible to collect a separated material that is generated at the time of assembly without causing deterioration in assembling property.

In a third embodiment of the present invention, a configuration in which the leaf spring is fixed to the housing with a screw or the like to mount the optical element to the housing will be described. The collecting portion of the third embodiment collects a separated material that is generated when a screw is screwed into a screw hole in the case of fixing the leaf spring to the housing with the screw.

FIG. 12is an example in which a leaf spring120is fixed to a housing130with a self-tap screw121(hereinafter referred to as “screw121”).FIG. 13is a sectional view taken along a line passing through a screw hole123inFIG. 12. The leaf spring120is positioned by fitting of a round hole124into a boss125and a long round hole126into a boss127. The leaf spring120is then fixed to the housing130with the screw121. In this case, the leaf spring120and the bosses125and127slide to cause generation of a separated material. For collecting this separated material, a collecting portion131is provided on the surfaces of the boss125and the boss127. The collecting portion131comprises adhesive500applied on the surfaces of the boss125and the boss127.

Further, the screw121enters the housing130while scraping off the housing130to thereby generate a separated material. Particularly, due to the screw hole123being a through hole, the separated material may fall on the rear surface side of the housing130. This increases the possibility that the separated material is deposited in the process to be mixed. For collecting such a separated material, the collecting portion132is provided inside the screw hole123. The collecting portion132comprises adhesive500applied on the inner surface of the screw hole123. The collecting portion may also be provided inside the screw hole123and in a region in which the housing130is exposed from a hole portion122, which is provided in the leaf spring120and through which the screw121passes. The collecting portion is not restrictively provided on the leaf spring configured to fix the reflection mirror62, but may, for example, be provided around the screw hole for fixing the rotary polygon mirror to the housing. As thus described, according to the third embodiment, it is possible to collect a separated material that is generated at the time of assembly without causing deterioration in assembling property. According to the third embodiment, it is possible to collect a separated material at a place at which the separated material is generated at the time of assembly.

This application claims the benefit of Japanese Patent Application No. 2017-046525, filed Mar. 10, 2017, which is hereby incorporated by reference herein in its entirety.