LIGHT EMISSION DEVICE ARRAY FITTING STRUCTURE OF ELECTROPHOTOGRAPHIC APPARATUS

Abstract: A light emission device array fitting structure of an electrophotographic apparatus for forming an electrostatic latent image by exposing a photosensitive drum to light from an array composed of a large number of light emitting diodes, etc. It is intended to keep a stable condition for a long time to expose the photosensitive drum with image-carrying light of high quality. The fitting structure comprises a fixed bracket (31) made of a rigid body fixedly disposed in the electrophotographic apparatus, a rotary bracket (33) made of a rigid body fixed to the light emission device raay (2) and connected rotatably relative to the fixed bracket (31), urging means (37) for urging the light emission device array to the outer peripheral surface of the photosensitive drum (1), and gap retaining means (38) for keeping a gap between the light emission device array (2) and the outer peripheral surface of the photosensitive drum (1) constant, when it is pushed to the outer peripheral surface of the photosensitive drum (1) by the urging force of the urging means (37).

Description: TECHNICAL FIELD This invention relates to a mount structure of a light emitting element array in an electro-photographic apparatus according to the preamble of claim 1. In such a mount structure of a light emitting element array in an electro-photographic apparatus, a beam emitted from a light emitting element is focused on a photoconductor drum by a lens so that a beam radiated from one light emitting element forms one dot of an image. Therefore, a precise distance between the light emitting array and the photoconductor drum must be maintained. A mount structure of a light emitting element array in an electro-photographic apparatus is known from JP-U-1 173 749. According to this known construction a bias means is provided for holding the light emitting element array against the outer surface of the photoconductor drum. The bias means is comprised of two coil springs which are arranged for pulling the light emitting element array against the outer surface of the photoconductor drum. From JP-A-1 216 371 a mount structure of a light emitting element array in an electro-photographic apparatus is known which comprises a photoconductor drum rotatably driven around an axis, a light emitting element array having a plurality of light emitting elements arranged parallel to the axis of the photoconductor drum and opposite to an outer surface thereof. This known mount structure comprises also a fixed bracket fixedly mounted on the electro-photographic apparatus, a rotatable bracket rotatably mounted on the fixed bracket and fixedly secured to the light emitting element array and a space keeping means which is pushed against the outer surface of the photoconductor drum so as to maintain a constant distance between the light emitting element array and the outer surface of the photoconductor drum. However with this known mount structure there are not provided means for maintaining a permanent contact between the space keeping means and the photoconductive drum. A further known mount structure for a light emitting element array in an electro-photographic apparatus is shown in Fig. 5 (Fig. 5(A) being a front view and Fig. 5(B) being a side view). A plurality of light emitting diodes (LED) are arranged on a LED array 91 that is rigidly mounted on leaf springs 92. The bearings (spacing means) 94 rotatably mounted on the LED array 91 are urged to the photoconductor drum 95, so that the distance between the LED array 91 and outer periphery of the photoconductor drum (information recording media) 95 remains constant. However, due to the rotating photoconductor drum 95, the leaf springs 92 vibrate in the direction A, so that the bearings 94 do not stably contact the surface of the photoconductor drum 95. Therefore, the leaf springs 92 are pushed from the back thereof by means of rubber dampers 97 mounted on the fixed bracket 96 so as to restrict the vibration of the leaf springs 92 and prevent a rough printing. In the mount structure of a light emitting element array in an electro-photographic apparatus known in the prior art as mentioned above, the bearings 94 are strongly urged to the surface of the photoconductor drum 95 by a damping force of the rubber dampers in addition to a spring force of the leaf springs 92 and, therefore, the surface of the photoconductor drum 95 becomes worn after extended use, so that the distance between the LED array 91 and the periphery of the photoconductor drum 95 is reduced. Thus, focusing on the photoconductor drum 95 for one dot will be out of order and image quality will deteriorate. Also, the leaf spring 92, particularly, the central portion 92a thereof which is not pushed by the rubber damper 97 vibrates or is twisted, so that the image deposited on the photoconductor drum 95 will deteriorate or will produce jitters (disorder of dots) and image quality is reduced. DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a mount structure of a light emitting element array in an electro-photographic apparatus, in which a high quality staple light image can be deposited on the photoconductor drum from a light emitting array, even after extended use. According to the present invention this object is solved by the features of claim 1. Further features and improved embodiments of the present invention result from the subclaims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side cross-sectional view of a first embodiment; Figure 2 is a side schematic view of a printer according to the present invention; Figure 3 is a perspective view of the first embodiment; Figure 4 is a side view of a second embodiment; Figure 5 shows a prior art, particularly, (A) is a front view and (B) is a side view. BEST MODE FOR CARRYING OUT THE INVENTION Embodiments will now be described with reference to the drawings. Fig. 2 shows a printer using the present invention. In the drawing, the reference numeral 1 denotes a photoconductor drum rotated in the direction B about an axis and has a cylindrical outer surface electrified by a pre-electrification unit, not illustrated. The reference numeral 2 denotes a light emitting diode array in which a plurality of light emitting diodes are arranged parallel to the axial direction of the photoconductor drum 1. One image beam of one dot from one light emitting diode is radiated to the outer surface of the photoconductor drum and a latent image is formed on the outer surface of the photoconductor drum 1. The reference numeral 4 denotes a developing unit for developing the latent image on the photoconductor drum 1 with a toner; 5, a transfer unit for transferring the toner image on the photoconductor drum 1 to a recording sheet; and 6, a cleaner for cleaning the toner remaining on the outer surface of the photoconductor drum 1. The recording sheet 100 is fed by a sheet feeding roller 7 to a passage in a printer and the toner image is fixed onto the recording sheet 100 by a fixing unit. The fixed recording sheet 100 is then discharged by a discharge roller 106 to a stacker 107, and after the transfer operation, the surface of the photoconductor drum 1 is cleaned by the cleaner 6. Fig. 3 is a perspective view of a supporting section for supporting the light emitting diode array and Fig. 1 is a side sectional view thereof. The reference numeral 21 denotes a light emitting diode (LED); and 22 denotes a drive circuit thereof, which are both mounted on a printed board 23. A beam emitted from the light emitting diode 21 is focused by a focusing lens 24 on the outer surface of the photoconductor drum 1. The light path of this beam is directed to the center axis O of the photoconductor drum 1. The reference numeral 31 denotes a fixing bracket metal made of a rigid metal plate fixed on the printer by screws. The shafts 32 are projected from the right and left ends of the bracket. A rotatable bracket 33 also made of a rigid metal plate is rotatably supported on the shafts 32. One of the bearing holes 34 and 35 engaged with the shafts 32 has a circular section engaged with the shaft 32 and the other bearing hole 35 is an elongated hole extending in the same direction as the light path of the beam emitted from the light emitting diode 21. The reference numeral 37 is a torsion spring for urging the rotatable bracket 33 around the shaft 32 and, thus, the light emitting diode array 2 is urged toward the outer surface of the photoconductor drum 1. The respective bearings 38 are rotatably mounted at the left and right ends of the light emitting diode array 2, so that the head portions thereof are projected toward the photoconductor drum 1. Therefore, the bearings 38 are always urged to the outer surface of the photoconductor drum 1 by the bias force of the torsion springs 37 and thus the distance between the light emitting diode array 2 and the photoconductor drum 1 always remains constant. Due to the position or mount errors of various members, such as, the fixed bracket 31 and the photoconductor drum 1, the light emitting diode array 2 may not be parallel to the outer surface of the photoconductor drum 1 and, therefore, one of the pair of bearings 38 may not contact the photoconductor drum 1. However, since one of the bearing holes is an elongated hole parallel to the light path of the beam as mentioned above, the shaft 32 at the side of the elongated bearing hole 35 is freely movable in the direction parallel to the light path, toward or away from the outer surface of the photoconductor drum 1. Therefore, if the bracket 31 is fixed so that the position at the circular bearing hole 34 is set at an appropriate position, the left and right bearings 38 are both urged to the outer surface of the photoconductor drum 1 and thus the light emitting diode array 1 is automatically set in an appropriate position so as to be parallel to the outer surface of the photoconductor drum 1. According to the first embodiment of a mount structure of a light emitting element array in an electro-photographic apparatus, the rotatable bracket for mounting the light emitting element array and the fixed bracket for supporting the same are both rigid bodies and mutually and rotatably connected by means of a bias means. Therefore, vibration or torsion can be prevented as a whole and a high quality light image can be produced on the photoconductor drum. In addition, it is no longer necessary to provide a rubber damper or the like to absorb the vibration, and therefore the space keeping means, such as bearings, can be forced to the surface of the photoconductor drum by a small force. Therefore, wear of the photoconductor drum is very small for extended use and the distance between the light emitting element and the outer surface of the photoconductor drum is minimal, and thus a good focus, less jitter and stable exposure can be maintained. Also, one of the supporting means for supporting the light emitting element array by its respective ends is movable and parallel to the light path of the beam, and therefore the light emitting element array is automatically parallel to the outer surface of the photoconductor drum. Thus, since a parallel adjustment is no longer necessary at the time of assembling the same, a mount can very easily be effected and the apparatus can be assembled beforehand as an unit. Fig. 4 is a side view of a second embodiment of a mount structure of an optical head in an electro-photographic apparatus according to the present invention. In the drawing, the reference numeral 31 denotes a fixed bracket, which is the same as the fixed bracket 12 in Fig. 1, except that it integrally provides a bracket pushing spring 42 (a second urging means). The other structural members are indicated by the same reference numerals as Fig. 1. The bracket pushing spring 42 urges the portion of the ring hole of the rotatable bracket 33 in a direction toward the photoconductor drum 1, i.e., in the direction parallel to the light path. Therefore, the micro-vibration of the rotatable bracket 33 at the portion of the elongated hole 35 can be restricted and the respective gap bearings 38 can be forced to the photoconductor drum 1, so that the distance between the photoconductor drum 1 and the optical head (LED array) 2 remain constant. As a result, the problem in the prior art, i.e., a print disarray can be prevented. The bracket pushing spring 42 can be small enough to restrict micro-vibration, so that it does not affect the force of the qap bearings 38 for pushing the photoconductor drum 1. As mentioned above, the respective gap bearings 38 of the optical head (LED array) are stably pushed to the photoconductor drum 1 at the respective ends thereof by means of the bracket pushing springs 42, so that the distance between the photoconductor drum 1 and the optical head 2 remains constant. Therefore, the beam from the optical head 2 is focused stably on the surface of the photoconductor drum 1 so as to prevent a print disorder. According to the second embodiment as mentioned above, the respective gap bearings of the optical head (LED array) are in constant and stable contact with the surface of the photoconductor drum 1 at the respective ends thereof. [Industrial Applicability] It should be understood by those skilled in the art that the present invention can be applied to various kinds of electro-photographic apparatuses, in which light emitting element arrays each having a plurality of light emitting elements arranged parallel to the axis of the photoconductor drum are arranged with a certain interval along the outer surface of the photoconductor drum.

Claims: A mount structure of a light emitting element array in an electro-photographic apparatus, comprising a photoconductor drum (1) rotatably driven around an axis, a light emitting element array (2) having a plurality of light emitting elements (21) arranged parallel to the axis of the photoconductor drum (1) and opposite to an outer surface thereof, said mount structure comprising: a fixed bracket (31) fixedly mounted on the electro-photographic apparatus; a rotatable bracket (33) rotatably mounted on the fixed bracket (31) and fixedly secured to the light emitting element array (2); a bias means (37) for holding the light emitting element array (2) against the outer surface of the photoconductor drum (1); a space keeping means being pushed by the bias means (37) against the outer surface of the photoconductor drum (1) so as to maintain a constant distance between the light emitting element array (2) and the outer surface of the photoconductor drum (1); wherein the rotatable bracket (33) is rotatably mounted on the fixed bracket (31) by a pair of bearings (34, 35) arranged a certain interval apart and parallel to the axis of the photoconductor drum (1), wherein said rotatable bracket (33) is supported on said fixed bracket (31) so as to be movable toward or away from the photoconductor drum (1) at one of the bearings (35); wherein said one of the bearings (35) comprises an elongated hole (35) formed by either one of the fixed bracket (31) and the rotatable bracket (33) and a shaft (32) provided on the other bracket and engaged with the elongated hole (35); and wherein said bias means (37) comprises a first torsion spring provided at the one end of the rotatable bracket (33) associated to the bearing (34) of the shaft (32) arranged opposite to the elongated hole (35) for urging this end of the rotatable bracket (33) towards the conductor drum (1), and comprises a second torsion spring provided at the other end of the rotatable bracket (33) associated to the bearing (35) of the shaft (33) at the elongated hole (35) for urging the other end of the rotatable bracket (33) towards the conductor drum (1), said first and said second torsion springs being arranged in the vicinity of said pair of bearings (34, 35) and being arranged around said shaft (32), respectively. A mount structure of a light emitting element array in an electro-photographic apparatus as set forth in claim 1, wherein the fixed bracket (31) and the rotatable bracket (33) are both made of rigid metal plates. A mount structure of a light emitting element array in an electro-photographic apparatus as set forth in claim 1, wherein said space keeping means comprises bearings rotatably mounted on the light emitting element array (2) at the respective ends thereof in such a manner that said bearings are pushed against the outer surface of the photoconductor drum (1) and rotated by the rotation of the photoconductor drum (1). A mount structure of a light emitting element array in an electro-photographic apparatus as set forth in claim 1, wherein that one of the respective axial ends at which said rotatable bracket (33) rotatably connected to said fixed bracket (31) is only rotatably supported to said fixed bracket (31), and the other end is connected to the same rotatably and movably toward and away from the photoconductor drum (1); and in that further bias means (42) are integrally mounted on said fixed bracket (31) for urging said other end of the rotatable bracket (33) toward said photoconductor drum (1).

Inventors: TOMITA HIROYUKI, YOSHIDA KOHICHI, TOMITA, HIROYUKI, YOSHIDA, KOHICHI
Applicants: FUJITSU ISOTEC LTD, FUJITSU LTD, FUJITSU ISOTEC LIMITED, FUJITSU LIMITED
Application year: 1992
Main classification: G03G15
IPC codes: B41J2, G03G15