Optical scanning device and image forming apparatus therewith

An optical scanning device is provided with a housing, a plurality of laser light sources, and a substrate. The laser light sources are attached to a side wall of the housing in a state wherein three terminals are protruding outward. The substrate is disposed to face an outer surface of the side wall of the housing. The laser light sources include: a first laser light source having a predetermined angle with respect to the substrate; and a second laser light source having a symmetrical angle to the angle of the first laser light source with respect to the substrate. In the first laser light source, only one of the three terminals is bent in the direction to be separated from other two terminals, and the second laser light source is disposed by inverting 180° a laser light source having a configuration same as that of the first laser light source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of International Application No. PCT/JP2015/081587 filed Nov. 10, 2015, in the International Patent Office, which claims priority to Japanese Application No. 2014-238377, filed Nov. 26, 2014, in the Japanese Property Office, the disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an optical scanning device that scans with laser light to write and form an image and that is incorporated in an image forming apparatus such as a printer, a copier, or a facsimile machine, and relates also to an image forming apparatus provided with such an optical scanning device.

BACKGROUND ART

Conventional image forming apparatuses exploiting electrophotography such as copiers, printers, etc., incorporate an optical scanning device that scans and thereby irradiates the surface of a photosensitive drum which has been electrostatically charged uniformly by a charging device with laser light modulated based on entered image data. An electrostatic latent image formed by the optical scanning device is developed into a toner image by a developing device. Then, the toner image is transferred to a recording sheet or the like, and is then turned into a permanent image by a fixing device. In this way, an image forming process proceeds.

The optical scanning device includes a laser light source (LD) that emits laser light for writing an electrostatic latent image, an optical system for scanning, while reflecting the emitted laser light, in the axial direction (the main scanning direction) of the photosensitive drum, a housing for housing these, a light source circuit board fitted to the housing, etc. The optical scanning device writes an electrostatic latent image on the surface of the photosensitive drum with laser light with which the optical system scans the surface.

For example, Patent Document 1 discloses an optical scanning device that includes four laser light sources, an optical system for scanning with laser light, and four light source circuit boards for controlling the output of the laser light sources respectively. For another example, Patent Document 2 discloses an optical scanning device that includes four laser light sources, an optical system for scanning with laser light, and one light source circuit board for controlling the output of four laser light sources.

LIST OF CITATIONS

Patent Literature

Patent Document 1: Japanese Patent Application Publication No. 2006-227494Patent Document 2: Japanese Patent Application Publication No. 2010-256770

SUMMARY OF THE INVENTION

Technical Problem

In an optical scanning device like the one described above, when a plurality of LDs having mutually different angles with respect to a circuit board are fitted to the housing and one circuit board, an attempt to fit the LDs with their terminals (leads) extending straight results in a narrow gap between oblong terminal insertion holes formed in the circuit board; this makes it difficult to form a copper layer (land) on the circuit board. Thus, it is necessary to widen the gap between the terminal insertion holes by previously having the terminals of the LDs subjected to forming (bending). Here, as the number of places subjected to forming increases, the likeliness of electrostatic breakdown, cracks, wire bonding breakage, etc., in the LDs increases. Thus, a reduction is sought in the number of places subjected to forming.

When the angles of two LDs with respect to a circuit board are in symmetry, using two types of LDs which have their terminals subjected to forming in different shapes increases the number of components, and also makes it necessary to sort these two types of LDs to fit them to places corresponding thereto respectively. This inconveniently complicates the manufacturing process.

Devised against the background discussed above, an object of the present invention is to provide an optical scanning device that can minimize the number of places where an LD terminal has to be subjected to forming, that allows easy formation of a copper layer on the circuit board, and that can achieve a reduced number of components and simplified assembly, and to provide an image forming apparatus incorporating such an optical scanning device.

Means for Solving the Problem

To achieve the above object, according to first aspect of the present invention, an optical scanning device includes a housing, a plurality of laser light sources, and a circuit board. The optical scanning device scans a scanned surface with laser light emitted from the laser light sources. The plurality of laser light sources are fitted to a side wall of the housing such that three terminals of the laser light sources protrude outward. The circuit board is arranged opposite an outer face of the side wall of the housing, and has formed therein insertion holes through which the terminals of the laser light sources are inserted. The laser light sources each include a first laser light source which has a predetermined angle with respect to the circuit board, and a second laser light source which has such an angle with respect to the circuit board as to be in symmetry with the first laser light source. The first laser light source has, of the three terminals thereof, only one terminal subjected to bending in a direction away from the other two terminals. The second laser light source is a laser light source having the same structure as the first laser light source but arranged rotated through 180° therefrom.

Advantageous Effects of the Invention

According to the first aspect of the present invention, it is possible to use the same component for both the first laser light source having a predetermined angle with respect to the circuit board and the second laser light source having such an angle with respect to the circuit board as to be in symmetry with the first laser light source. This helps reduce the number of components, and thus helps improve assembly efficiency. The first and second laser light sources each have, of the three terminals thereof, only one terminal subjected to bending in a direction away from the other two terminals. Thus, it is possible to suppress the likeliness of electrostatic breakdown, cracks, wire bonding breakage, etc., and also to secure a gap between terminal insertion holes required to form a copper layer.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.FIG. 1is a schematic sectional view of an image forming apparatus100incorporating an optical scanning device4according to the present invention, here showing a tandem-type color image forming apparatus. Inside the main body of the image forming apparatus100, four image forming portions Pa, Pb, Pc, and Pd are arranged in this order from the upstream side (the right side inFIG. 1) with respect to the transport direction. These image forming portions Pa to Pd are provided to correspond to images of four different colors (cyan, magenta, yellow, and black) respectively, and sequentially form cyan, magenta, yellow, and black images respectively, each through the processes of electrostatic charging, exposure to light, image development, and image transfer.

In these image forming portions Pa to Pd, there are respectively arranged photosensitive drums1a,1b,1cand1dthat carry visible images (toner images) of the different colors. Moreover, an intermediate transfer belt8that rotates in the clockwise direction inFIG. 1by being driven by a driving means (unillustrated) is arranged next to the image forming portions Pa to Pd. Toner images formed on these photosensitive drums1ato1dare sequentially transferred to the intermediate transfer belt8that moves while being in contact with the photosensitive drums1ato1d, and are then transferred all at once to a transfer sheet P by a secondary transfer roller9. Then, the toner images are fixed to the transfer sheet P in a fixing portion7, and the transfer sheet P is then discharged out of the apparatus main body. While the photosensitive drums1ato1dare rotated in the counter-clockwise direction inFIG. 1, an image forming process is performed with respect to each of them.

Transfer sheets P to which toner images are to be transferred are stored in a sheet cassette16in a lower part of the apparatus, and are transported via a sheet feeding roller12aand a registration roller pair12bto the secondary transfer roller9. As the intermediate transfer belt8, a dielectric resin sheet is used, which typically is, for example, a seamless belt having no seam.

Now, the image forming portions Pa to Pd will be described. Around and under the photosensitive drums1ato1d, which are rotatably arranged, there are arranged charging devices2a,2b,2c, and2dfor electrostatically charging the photosensitive drums1ato1d, an optical scanning device4for exposing the photosensitive drums1ato1dto light based on image data, developing units3a,3b,3c, and3dfor forming toner images on the photosensitive drums1ato1d, and cleaning portions5a,5b,5c, and5dfor removing developer (toner) left unused on the photosensitive drums1ato1d.

When an instruction to start image formation is fed in by a user, the surfaces of the photosensitive drums1ato1dare first electrostatically charged uniformly by the charging devices2ato2d, and are then irradiated with laser light by the optical scanning device4so that electrostatic latent images based on the image signal are formed on the photosensitive drums1ato1drespectively. The developing units3ato3dare charged with predetermined amounts of toner of different colors, namely cyan, magenta, yellow, and black respectively, by a supplying device (unillustrated). The toner is fed from the developing units3ato3donto the photosensitive drums1ato1d, and electrostatically attaches to them, thereby forming toner images based on the electrostatic latent images formed by exposure to light from the optical scanning device4.

Then, an electric field is applied between primary transfer rollers6ato6dand the intermediate transfer belt8with a predetermined transfer voltage, and then, by the primary transfer rollers6ato6d, the cyan, magenta, yellow and black toner images on the photosensitive drums1ato1dare transferred to the intermediate transfer belt8. These images of four colors are formed in a predetermined positional relationship prescribed to form a predetermined full-color image. Thereafter, in preparation for subsequent formation of new electrostatic latent images, toner left unused on the surfaces of the photosensitive drums1ato1dis removed by the cleaning portions5ato5d.

The intermediate transfer belt8is wound around a transport roller10on the upstream side and a driving roller11on the downstream side. As the driving roller11rotates by being driven by a driving motor (unillustrated), the intermediate transfer belt8rotates in the clockwise direction; meanwhile, a transport sheet P is transported from the registration roller pair12b, with predetermined timing, to the secondary transfer roller9arranged next to the intermediate transfer belt8so that a full-color image formed on the intermediate transfer belt8is transferred to the transport sheet P. The transfer sheet P having the toner images transferred to it is transported to the fixing portion7.

The transfer sheet P transported to the fixing portion7is then heated and pressed there by a fixing roller pair13so that the toner images are fixed to the surface of the transport sheet P to become a permanent image. The transfer sheet P having the full-color image fixed on it in the fixing portion7is distributed between different transport directions by a branching portion14which branches into a plurality of directions. When an image is formed only on one side of the transfer sheet P, the transfer sheet P is discharged, as it is, onto a discharge tray17by a discharge roller pair15.

On the other hand, when images are formed on both sides of the transfer sheet P, a large part of the transfer sheet P having passed through the fixing portion7is momentarily discharged onto the discharge tray17; then, the discharge roller pair15is rotated in the reverse direction so that the transfer sheet P is pulled back into the apparatus. The pulled-back transfer sheet P is then distributed into a reverse transport passage18by the branching portion14; thus the transfer sheet P is, with the image side reversed, transported once again to the secondary transfer roller9. Then, the next image formed on the intermediate transfer belt8is transferred by the secondary transfer roller9to the side of the transfer sheet P on which no image has yet been formed. The transfer sheet P is then transported to the fixing portion7, where the toner image is fixed, and is then discharged onto the discharge tray17.

FIG. 2is a plan view showing an internal structure of the optical scanning device4according to one embodiment of the present invention;FIG. 3is a side sectional view (as seen from the direction indicated by arrows A and A′ inFIG. 2) showing the internal structure of the optical scanning device4according to the present embodiment. InFIG. 2, plane mirrors49ato49care omitted from illustration. As shown inFIGS. 2 and 3, the optical scanning device4has a housing48, and substantially in a central part of a bottom surface48aof the housing48, a polygon mirror45is arranged. In this embodiment, the polygon mirror45is formed as a rotary multiple-face mirror in the shape of a regular hexagon having, as its side faces, six deflection surfaces (reflection surfaces)45a. The polygon mirror45is driven to rotate at a predetermined speed by a polygon motor38. The polygon motor38is fixed to a motor supporting plate39, and the motor supporting plate39is fixed to the bottom surface48a.

On a side wall48bof the housing48on its front side (on the bottom side inFIG. 2), there are arranged four laser light sources40ato40d. The laser light sources40ato40dcomprise LDs (laser diodes), and emit laser light (beam light) D1to D4optically modulated based on an image signal.

Between the laser light sources40ato40dand the polygon mirror45, there are arranged four collimator lenses41that are arranged so as to correspond to the laser light sources40ato40drespectively, apertures42that give the laser light beams D1to D4having passed through the collimator lenses41a predetermined beam width, four cylindrical lenses43through which, after having passed through the apertures42, the laser light beams D1, D2, D3and D4pass respectively, and two turning mirrors44that direct the laser light beams D1to D4having passed through the cylindrical lenses43to the deflection surfaces45aof the polygon mirror45. InFIG. 2, only the collimator lenses41, the apertures42, and the cylindrical lenses43that correspond to the laser light sources40band40care illustrated, meaning that the collimator lenses41, the apertures42, and the cylindrical lenses43that correspond to the laser light sources40aand40dare omitted from illustration.

The collimator lenses41form the laser light beams D1to D4emitted from the laser light sources40ato40dinto substantially parallel light beams; the cylindrical lenses43have a predetermined refractive power only in the sub-scanning direction (the up/down direction inFIG. 3). Inside the housing48, a first scanning lens46ais arranged opposite a first scanning lens46bacross the polygon mirror45; second scanning lenses47aand47bare arranged opposite second scanning lenses47cand47dacross the polygon mirror45. The first scanning lenses46aand46band the second scanning lenses47ato47dhave113characteristics so as to focus the laser light beams D1to D4reflected and deflected by the polygon mirror45on the photosensitive drums1ato1d(seeFIG. 1). In the optical paths of the laser light beams D1to D4from the polygon mirror45to the photosensitive drums1ato1d(seeFIG. 1), the plane mirrors49ato49care arranged.

Now, how the optical scanning device4configured as described above performs scanning with the laser light beams D1and D2will be described. First, the laser light beams D1and D2emitted from the laser light sources40aand40bare formed into substantially parallel light beams through the collimator lenses41, and are then given a predetermined optical path width by the apertures42. Then, the laser light beams D1and D2having been formed into substantially parallel light beams are incident on the cylindrical lenses43. The laser light beams D1and D2having entered the cylindrical lenses43exit as they are, that is, as the parallel light beams in the main scanning section but after been converged in the sub-scanning direction, so as to be focused as linear images on the deflection surfaces45aof the polygon mirror45. Here, for easy separation between two optical paths of the laser light beams D1and D2deflected by the polygon mirror45, these laser light beams D1and D2are configured to be incident on the deflection surfaces45aat different angles in the sub-scanning direction.

The laser light beams D1and D2incident on the polygon mirror45are deflected by the polygon mirror45at a constant angular velocity, and are then deflected by the first scanning lens46aat a constant velocity. The laser light beams D1and D2having passed through the first scanning lens46aare bent a predetermined number of times by the plane mirrors49aand49barranged in their respective optical paths; then, the laser light beams D1and D2are incident on the second scanning lenses47aand47brespectively to be deflected by the second scanning lenses47aand47bat a constant velocity. Then, the laser light beams D1and D2deflected at a constant velocity are bent by the last plane mirrors49carranged in their respective optical paths so as to be directed, through windows60aand60bformed in a top cover60that covers an opening of the housing48, to the photosensitive drums1aand1b.

Likewise, the laser light beams D3and D4emitted from the laser light sources40cand40dare, after passing through the collimator lenses41, the apertures42, and the cylindrical lenses43, deflected by the polygon mirror45at a constant angle, and are then deflected by the first scanning lens46bat a constant velocity. Then, after being bent by the plane mirrors49aand49b, the light beams laser D3and D4are deflected by the second scanning lenses47cand47drespectively at a constant velocity. Then, the laser light beams D3and D4are bent by the last plane mirrors49cso as to be directed, through windows60cand60d, to the photosensitive drums1cto1d.

Now, the structure around the laser light sources40ato40dwill be described in detail.FIG. 4is a perspective view of the side wall48bof the housing48, to which the laser light sources40ato40dare fitted.

As shown inFIG. 4, in the side wall48bof the housing48, there are formed four light source insertion holes50ato50din which the four laser light sources40ato40dare fitted respectively.

Moreover, in the side wall48b, there are formed, each in a predetermined position, screw holes57ato57dinto which screws (unillustrated) are threaded so as to fix a circuit board70(seeFIG. 7) to the side wall48b, and two positioning bosses59aand59bthat protrude outward from the side wall48bto determine the position of the circuit board70.

FIGS. 5 and 6are respectively a perspective view and a sectional view of the light source insertion hole50dformed in the side wall48b.FIG. 7is a plan view of the circuit board70fitted on the side wall48b.FIG. 8is a side view of the circuit board70having terminals53of the laser light sources40ato40dinserted in it.FIG. 9is a plan view of the laser light source40aas seen from the side at which it has the terminals53ato53c. Although the structure of the light source insertion hole50dalone is illustrated inFIGS. 5 and 6, the light source insertion holes50ato50chave a similar structure. The laser light source40dhas the same structure as that of the laser light source40a; the laser light sources40band40chave the same structure as the laser light source40a, except that, in these, the terminal53bis not subjected to forming.

As shown inFIG. 5, the light source insertion holes50ato50deach have a press-in portion55, which has a two-stage structure in which a large diameter portion55ahaving a larger diameter than a flange51b(seeFIG. 8) of the laser light sources40ato40dand a small diameter portion55bhaving a smaller diameter than the flange51bare formed in this order from the outer side of the side wall48b. At one place on the open rim of the press-in portion55, a convexity56is formed that engages with a concavity51ba(seeFIG. 9) formed in the circumferential surface of the flange51bto determine the position of the laser light sources40ato40din their circumferential direction.

As shown inFIGS. 8 and 9, the laser light sources40ato40dare each composed of a main body51ain the shape of a cylinder from which a laser light beam is emitted, a flange51bthat protrudes in the shape of a brim from the circumferential surface of the main body51a, and three terminals53ato53cthat protrude substantially perpendicularly from the bottom surface of the flange51b. At one place on the circumferential rim of the flange51b, there is formed a first concavity51bain a rectangular shape. At positions each 45° apart from the first concavity51baon opposite sides thereof, there are formed second concavities51bbin a triangular shape.

As shown inFIG. 9, in the two outer laser light sources40a(first laser light source) and40d(second laser light source), one (the terminal53b) of the three terminals53ato53chas been subjected to a forming (bending) process. The laser light sources40ato40dare in a reference position when they are arranged as shown inFIG. 9, where the first concavity51bapoints upward in the vertical direction (the direction of straight line L1) and the second concavities51bbpoint in the horizontal direction (the direction of straight line L2). In the laser light sources40aand40d, due to a restriction of a jig with which the terminal53bis subjected to forming, the terminal53bhas been subjected to forming in a direction inclined by an angle θ (here 23°) with respect to the horizontal direction.

To the side wall48b, the circuit board70that controls the output of the four laser light sources40ato40dis fixed to face the outer side of the side wall48b. The circuit board70controls the output of the four laser light sources40ato40d, and as shown inFIG. 7, on the circuit board70, electronic components71such as IC chips, resistors, and capacitors are mounted.

As shown inFIG. 7, in the circuit board70, there are formed terminal insertion holes73ato73din which the terminals53ato53cof the four laser light sources40ato40dare inserted and fixed, four screw insertion holes75ato75bin which screws are inserted, and two boss insertion holes77aand77bwith which the positioning bosses59aand59bon the side wall48bof the housing48are engaged. The boss insertion hole77ain which the positioning boss59ais inserted is an oblong hole that is elongate in the horizontal direction; the boss insertion hole77bin which the positioning boss59bis inserted is a circular hole.

The terminal insertion holes73band73c, in which the terminals53ato53cof the two inner laser light sources40band40care inserted, are formed in the shape of a circular hole having a slightly larger diameter than the terminals53ato53c. On the other hand, the terminal insertion holes73aand73d, in which the terminals53ato53cof the two outer laser light sources40aand40dare inserted, are formed in the shape of an oblong hole (seeFIG. 19) to allow easy insertion of the terminals53ato53cof the laser light sources40aand40d, which obliquely protrude from the flange51b.

Around the terminal insertion holes73ato73din the circuit board70, there is formed a layer of copper (unillustrated) referred to as a land so as to permit soldering from the direction (from front with respect to the plane ofFIG. 7) opposite to the inserting direction of the terminals53ato53c. This copper layer may be formed by etching copper foil or by plating.

Now, how the laser light sources40ato40dand the circuit board70are fitted to the housing48will be described.FIG. 10is a sectional view showing a state where the flange51bof the laser light source40b(40c) is held in a counter-bored part of the press-in portion55in the light source insertion hole50b(50c).FIGS. 11 to 13are sectional views showing states where the laser light sources40b(40c),40a, and40dare pressed and fixed in the press-in portions55of the light source insertion holes50b(50c),50a, and50drespectively.FIG. 14is a plan view showing a state where the laser light source40b(40c) is pressed and fixed in the press-in portion55of the light source insertion hole50b(50c).FIGS. 15 and 16are perspective views showing states where the laser light sources40aand40dare pressed and fixed in the press-in portions55of the light source insertion holes50aand50drespectively.FIGS. 17 and 18are respectively a front view and a sectional view showing a state where the laser light sources40ato40dare pressed and fixed in the light source insertion holes50ato50d.

First, from the outer side of the side wall48bof the housing48, the four laser light sources40ato40dare pressed and fixed, with their terminals53pointing to the outer side of the side wall48b, in the four light source insertion holes50ato50drespectively. Specifically, as shown inFIG. 10, with the concavity51baof the flange51bpositioned at the convexity56of the press-in portion55, the flange51bof each of the laser light sources40band40cis inserted in the press-in portion55. Here, the small diameter portion55bhas a smaller diameter than the flange51b, and thus the flange51bcan be held in a counter-bored part between the large diameter portion55aand the small diameter portion55b. This permits the flange51bto be held parallel to the side wall48b. Likewise, the laser light sources40aand40dare inserted in the press-in portions55of the light source insertion holes50aand50d, and the flanges51bare each held in a counter-bored part between the large diameter portion55aand the small diameter portion55b.

In this state, a force is applied to the laser light sources40aand40dso that, as shown inFIGS. 11 to 18, while the flange51band the side wall48bare held parallel to each other, the flange51bcan be pressed and fixed in the small diameter portion55b. That is, placing the flange51btemporarily in a counter-bored part between the large diameter portion55aand the small diameter portion55bof the press-in portion55permits the flange51bto be pressed in while the side wall48band the flange51bare held parallel to each other.FIG. 11shows a section of the flange51bcutting through the second concavity51bb.

As shown inFIGS. 17 and 18, the four laser light sources40ato40dare pressed and fixed in the light source insertion holes50ato50dfrom the outer side of the housing48such that the terminals53ato53cprotrude outward through the side wall48b. Of the laser light sources40ato40d, the two inner laser light sources40band40care arranged at substantially the same height, and the two outer laser light sources40aand40dare arranged at substantially the same height, at a higher position than the laser light sources40band40c.

The two outer laser light sources40aand40deach have a predetermined angle (inclination) with respect to the circuit board70relative to perpendicular line O (seeFIGS. 15 and 16) as an axis of rotation, and the angles of the laser light source40dand the laser light source40awith respect to the circuit board70are in symmetry. In this embodiment, used as the laser light source40d(second laser light source) inserted in the light source insertion hole50dis one obtained by rotating through 180° the laser light source40a(first laser light source) inserted in the light source insertion hole50a.

Then, as shown inFIG. 8, the circuit board70is fitted to the side wall48bfrom its outer side. As described above, owing to the flange51bbeing held in a counter-bored part between the large diameter portion55aand the small diameter portion55b, the laser light sources40ato40dcan be prevented from being inclined when pressed in. This reduces variations in the protruding positions of the terminals53ato53c. As a result, it is possible to smoothly insert the terminals53ato53cin the terminal insertion holes73ato73dof the circuit board70.

As shown inFIG. 15, the laser light source40ais inserted in the light source insertion hole50asuch that the first concavity51bapoints downward, and at the light source insertion hole50a, the convexity56is formed at a position deviated from perpendicular line O by the angle θ (23°) in the counter-clockwise direction. As shown inFIG. 9, the terminal53bhas been subjected to forming in a direction inclined by an angle θ (23°) with respect to the horizontal direction. Thus, when the first concavity51bais fitted on the convexity56, the laser light source40ais fitted to the side wall48bsuch that a tip end part of the terminal53bpoint in the horizontal direction (the leftward direction inFIG. 15).

On the other hand, the terminals53aand53c, which has not been subjected to forming, protrude perpendicularly from the flange51b, and thus, irrespective of the rotation of the flange51b, the terminals53aand53cprotrude with an inclination equal to the inclination angle of the laser light source40awith respect to the side wall48bin the horizontal direction (the rightward direction inFIG. 15). Thus, all of the three terminals53ato53cof the laser light source40aprotrude with their tip end parts pointing in the horizontal direction.

Likewise, as shown inFIG. 16, the laser light source40dis inserted in the light source insertion hole50dsuch that the first concavity51bapoints upward, and at the light source insertion hole50d, the convexity56is formed at a position deviated from perpendicular line O by the angle θ (23°) in the counter-clockwise direction. Thus, the laser light source40dachieves a state as if the laser light source40awere rotated through 180° and fitted on, with the result that the three terminals53ato53cof the laser light source40dalso protrude with their tip end parts pointing in the horizontal direction.

FIG. 19is an enlarged view of the terminal insertion hole73a(inside the broken-line inFIG. 7) formed in the circuit board70. As shown inFIG. 19, the terminal insertion hole73ahas a first insertion hole73aain which the terminal53ais inserted, a second insertion hole73abin which the terminal53bis inserted, and a third insertion hole73acin which the terminal53cis inserted. All of the first to third insertion holes73aato73acare formed in the shape of an oblong hole that is elongate in the same direction (horizontal direction).

All of the first to third insertion holes73aato73achave the same dimension A1(about 1.6 mm) in their longitudinal direction. While the first and third insertion holes73aaand73achave the same dimension A2(about 0.8 mm) in the direction orthogonal to their longitudinal direction, with consideration given to variations in the forming of the terminal53b, the second insertion hole73abis given a slightly larger dimension (about 1 mm) than the first and third insertion holes73aaand73ac. Here, no description will be given of the structure of the terminal insertion hole73din which the terminals53ato53dof the laser light source40dare inserted, since the terminal insertion hole73dis one obtained by rotating through 180° the terminal insertion hole73a(the first to third insertion holes73aato73ac) shown inFIG. 19.

As described above, all of the three terminals53ato53cof the laser light sources40aand40dprotrude with their tip end parts pointing in the horizontal direction, and thus the first to third insertion holes73aato73acthat constitute the terminal insertion holes73aand73dare also formed in the shape of an oblong hole that is elongate in the horizontal direction. This makes it easy to position the terminals53ato53cat the first to third insertion holes73aato73ac.

As the result of the terminal53bbeing subjected to forming in a direction away from the terminals53aand53c, the second insertion hole73abin which the terminal53bis inserted can be located away from the first and third insertion holes73aaand73ac. Specifically, as compared with a case where the terminal53bis not subjected to forming, a gap G (about 0.45 mm) between the second insertion hole73aband the third insertion hole73accan be secured, and this facilitates the formation of the copper layer (land) on the circuit board70.

Then, after the terminals53ato53care inserted in the terminal insertion holes73ato73d, the circuit board70is moved further toward the side wall48bso as to insert the two positioning bosses59aand59b(seeFIG. 4) in the boss insertion holes77aand77bin the circuit board70. In this way, the circuit board70is positioned in the planar direction (the direction parallel to the side wall48b). The circuit board70is positioned in the inserting direction by making contact with the circumferential rims of the light source insertion holes50ato50dand the screw holes57ato57d.

Then, screws are inserted through the screw insertion holes75ato75d(seeFIG. 7) of the circuit board70, and are threaded in the screw holes57ato57d(seeFIG. 4) of the side wall48bso that the circuit board70is fixed to the side wall48b. Then, the terminals53ato53dof the laser light sources40ato40dare soldered on the copper layer on the circuit board70, and thereby the laser light sources40ato40dare electrically connected to the circuit board70. In the manner described above, the laser light sources40ato40dand the circuit board70are fixed to the housing48.

In this embodiment, of the three terminals53ato53cof the laser light sources40aand40dhaving an angle with respect to the circuit board70, the terminal53balone is subjected to forming in a direction away from the terminals53aand53c. This helps minimize the number of terminals (one terminal) which have to be subjected to forming, and thus it is possible to reduce the risk of electrostatic breakdown, cracks, wire bonding breakage, etc., in the laser light sources40aand40d, which are prone to occur during the forming. Subjecting the terminal53bto forming in a direction away from the terminals53aand53chelps secure a sufficient gap G to form the copper layer (land) between the first and third insertion holes73aaand73acand the second insertion hole73ab, which together constitute the terminal insertion holes73aand73d.

Used as the laser light source40d(second laser light source) inserted in the light source insertion hole50dis one obtained by rotating through 180° the laser light source40a(first laser light source) inserted in the light source insertion hole50a. This helps reduce the number of components, and thus helps improve assembly efficiency.

The flanges51bof the laser light sources40ato40dare each temporarily held in a counter-bored part between the large diameter portion55aand the small diameter portion55b, and are then pressed in the small diameter portion55bso that the flanges51bcan be pressed in the light source insertion holes50ato50dwhile being held parallel to the side wall48b. Thus, it is possible to quickly and accurately fit the laser light sources40ato40dto the housing48.

The terminals53bof the laser light sources40aand40d, which have been subjected to forming, are inserted in the light source insertion holes50aand50dwith their tip end parts pointing in the horizontal direction, and thereby all of the terminals53ato53cof the laser light sources40aand40dprotrude in the horizontal direction. This facilitates the positioning with respect to the first to third insertion holes73aato73acformed in the circuit board70.

The embodiments described above are in no way meant to limit the present invention, which thus allows for many modifications and variations within the spirit of the present invention. For example, although the above-described embodiments deal with an optical scanning device4in which laser light beams D1to D4are emitted through the top face of a housing48to illuminate photosensitive drums1ato1darranged over the housing48, the photosensitive drums1ato1dmay be arranged under the optical scanning device4, and the laser light beams D1to D4may be emitted through the bottom face of the housing48.

Although the above-described embodiments deal with an optical scanning device4in which a polygon mirror45is arranged substantially at the center of a housing48such that laser light beams D1and D2and laser light beams D3and D4are deflected in opposite directions, the polygon mirror45may be arranged at one end of the housing48such that the laser light beams D1to D4are, while being deflected in the same direction, separated in the sub-scanning direction.

INDUSTRIAL APPLICABILITY

The present invention is applicable to optical scanning devices that scans with laser light to write and form an electrostatic latent image and that are incorporated in image forming apparatuses such as printers, copiers, facsimile machines, etc. Based on the present invention, it is possible to provide an optical scanning device that can minimize the number of places where an LD (laser diode) lead has to be subjected to forming and that can obtain simple assembly owing to the reduced number of components, and to provide an image forming apparatus incorporating such an optical scanning device.