Image forming apparatus

Abstract

In an image forming apparatus (1) utilizing electrophotographic technology, position and posture of a laser scan unit (5) with respect top a frame (13) is adjusted easily without cost rise and upsizing of the apparatus. Semicircular recesses (53) and an elongate hole (54) are formed at each of three fixing portions (52a, 52b and 52c) in the vicinities of side faces (51b) and a rear face (51c) of a housing (51) of the laser scan unit (5), and an adjuster 30 serving as a spacer is attached to each of the fixing portions (52a, 52b and 52c). Each adjuster (30) is elected among a plurality of kinds of adjustors respectively having different thicknesses manufactured by press working of metal plates commercially produced and having different thicknesses with using the same dies. The adjustor has a pair of semicircular engaging portions 30b and a coupling portion 30a perpendicular to and coupling the engaging portions (30b).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described hereinafter with reference to the annexed drawings. It is to be noted that all the drawings are shown for the purpose of illustrating the technical concept of the present invention or embodiments thereof, wherein:

FIG. 1 is a sectional view showing a configuration of a laser beam printer which is an example of an image forming apparatus in accordance with an embodiment of the present invention;

FIG. 2 is a perspective view showing a configuration of a laser scan unit in the image forming apparatus mentioned above;

FIG. 3 is a perspective view showing a configuration of mounting structure to mount the laser scan unit on a frame in the image forming apparatus mentioned above;

FIG. 4 is a perspective view showing an appearance of an adjuster used to adjust position and posture of the laser scan unit in the image forming apparatus;

FIG. 5 is a perspective view showing a problem caused by miss-positioning of the laser scan unit with respect to the frame in a horizontal plane;

FIG. 6 is a front view showing a problem caused by miss-positioning of the laser scan unit with respect to the frame in a vertical plane including a main scanning direction;

FIG. 7 is a perspective view showing a problem caused by miss-positioning of the laser scan unit with respect to the frame in a vertical plane including a sub-scanning direction; and

FIG. 8 is a perspective view showing a modified configuration of the mounting structure to mount the laser scan unit on the frame in the image forming apparatus mentioned above.

Claims

1. An image forming apparatus utilizing electrophotographic technology, comprising: a laser scan unit which is previously adjusted to have a predetermined quality when components thereof are assembled as a unit, and can be treated as a black box after being assembled with no adjustment, whereinthe laser scan unit is fixed on a frame by screws at three fixing portions respectively provided in vicinities of different three faces among a front face, a rear face and side faces of a housing of the laser scan unit made of resin molding, so as to be rotated in a horizontal plane around a vertical rotation axis;an adjuster, which can serve as a spacer to adjust inclination of the laser scan unit with respect to the frame in a vertical plane, is attached to each of the three fixing portions of the laser scan unit; andthe adjuster is selected among plurality kinds of adjusters each of which is formed of metal plate having different thickness.

2. The image forming apparatus in accordance with claim 1, wherein each of the three fixing portions has at least one guide which is formed on at least one of a top face and a bottom face of the housing of the laser scan unit; andthe adjuster has a coupling portion which faces or contacts to one of the front face, the rear face and the side faces of the housing of the laser scan unit, and a pair of engaging portions which are formed at both ends of the coupling portion to protrude in same direction and at least one of which engages with the guide of each of the three fixing portions.

3. The image forming apparatus in accordance with claim 2, wherein an inner dimension between the engaging portions of the adjuster has a predetermined value with no relation to the thickness of the metal plates of the adjuster.

4. The image forming apparatus in accordance with claim 2, wherein a first elongate hole which penetrates through the housing from the top face to the bottom face is formed at each of the three fixing portions; anda second elongate hole having substantially same shape as the first elongate hole is formed at each of the engaging portions of the adjuster, so that the screw penetrates through the first and second elongate holes when the laser scan unit is mounted on the frame.

5. The image forming apparatus in accordance with claim 2, wherein the guide is a recess formed on the top face or the bottom face of the housing of the laser scan unit;the engaging portions of the adjuster have substantially same shape of the recess; anda depth of the guide is shallower than a smallest thickness of the metal plate of the adjusters, so that the bottom face of the housing of the laser scan unit never contacts with the frame.

6. The image forming apparatus in accordance with claim 2, wherein the guide is at least one protrusion formed on the top face or the bottom face of the housing of the laser scan unit; andthe protrusion contacts with at least one sides of the engaging portions of the adjuster, so that the bottom face of the housing of the laser scan unit never contacts with the frame.

7. An image forming apparatus comprising: a photoconductor drum having a photoconductive layer formed on a surface thereof;an exposing means that irradiates laser beams on the surface of the photoconductive drum while scanning so as to form a latent image on the photoconductive layer;a developing means that forms a toner image on the surface of the photoconductor drum by adhering toner particles to portions where the latent image is firmed;a transfer means that is provided at a predetermined transfer position downstream from the developing means in a rotation direction of the photoconductor drum so as to face the surface of the photoconductor drum, and transfer the toner image to a recording paper sheet;a fixing means that fixes the toner image on the recording paper sheet by applying predetermined pressure and heat to the recording paper sheet;a paper feeding means to convey the recording paper sheet from a paper feed tray to an exit tray through the transfer means and the fixing means; anda control means to control the entire of the image forming apparatus, whereinthe exposing means is a laser scan unit which is previously adjusted to have a predetermined quality when components thereof are assembled as a unit, and can be treated as a black box after being assembled with no adjustment;the laser scan unit comprises a laser diode that emits a laser beam, a collimator lens that collimates the laser beam emitted from the laser diode, a cylindrical lens that focuses the laser beam in a main scanning direction, a polygon mirror that reflects the laser beam focused in the main scanning direction by the cylindrical lens to scan in the main scanning direction, an fθ lens that corrects aberration of the laser beam reflected by the polygon mirror while the laser beam passes therethrough, a mirror that reflects the laser beam passes through the fθ lens toward the surface of the photocondctor drum, and a boxy housing made of resin molding into which the above mentioned elements are installed;the housing of the laser scan unit is fixed on a frame of the image forming apparatus by screws at three fixing portions, two of which are provided in vicinities of both side faces of the housing and one of which is provided in a vicinity of a rear face of the housing;each fixing portion has a pair of semicircular recesses formed on a top face and a bottom face of the housing and a first elongate hole which penetrates through the housing from the top face to the bottom face;an adjuster, which can serve as a spacer to adjust inclination of the laser scan unit with respect to the frame in a vertical plane, is attached to each of the three fixing portions of the laser scan unit;the adjuster is selected among a plurality kinds of adjusters which are respectively formed of metal plates having different thickness, and has a coupling portion which faces or contacts the rear face and the side faces of the housing of the laser scan unit, and a pair of engaging portions which are formed at both ends of the coupling portion to protrude in same direction and engage with the recesses of each fixing portion;the engaging portions of the adjuster have substantially same shape and dimensions of the recess but smaller by predetermined tolerances that the recess, and an inner dimension between the engaging portions of the adjuster is substantially same dimension as but larger by a predetermined tolerance than a dimension between the recesses formed on the top face and the bottom face of the housing in each fixing portion;a first elongate hole which penetrates through the housing from the top face to the bottom face is formed at each of the three fixing portions, and a second elongate hole having substantially same shape as the first elongate hole is formed at each of the engaging portions of the adjuster, so that the screw penetrates through the first and second elongate holes when the laser scan unit is mounted on the frame;a depth of the recess is shallower than a smallest thickness of the metal plate of the adjusters, so that the bottom face of the housing of the laser scan unit never contacts with the frame, and thereby enabling to prevent cracking of the housing even when the laser scan unit is mounted on the frame by the screws.