Image forming apparatus having a dust proofing member for an exposure device

This application is based on Japanese Patent Application No. 2007-162331 filed on Jun. 20, 2007, with the Japanese Patent Office, the entire content of which is hereby incorporated by reference.

The present invention relates to an image forming apparatus employing an electro-photographic method.

The image forming apparatus, employing the electro-photographic method, is an apparatus which forms a toner image by an electrical charge, subsequent exposure and development, and then transfers the formed image onto a recording member as a permanent image.

Since dried toner particles are used in the image forming apparatus employing the electro-photographic method, various problems occur due to dust, such as loosened toner particles, paper-sheet powder, and particles generated by electrical discharge.

Among various dusts in the apparatus, dust on an exposure section directly results in lower image quality, leading to various technologies being developed to prevent the exposure section from creating such dust.

Unexamined Japanese Patent Application Publication No. 6-317951 discloses that an aperture to introduce light rays is formed at the top of a frame, mounted on a laser emitting section of a laser exposure device, to support a dustproof glass, and that members positioned more upstream in the moving direction of a photoconductor are placed higher than members positioned more downstream in the moving direction of the photoconductor, so that air is prevented from flowing toward dustproof glass, whereby the particles, such as spattered toner, are prevented from landing on dustproof glass.

Unexamined Japanese Patent Application Publication No. 2000-258968 discloses an image forming apparatus in that an air regulating member to control airflows is mounted upstream of an exposure position in the moving direction of a photoconductor.

Unexamined Japanese Patent Application Publication No. 2003-054024 discloses an image forming apparatus in that a cover is provided which protrudes from the top of an LED head toward the upstream in the moving direction of the photoconductor, and said cover is declined to come close to the photoconductor toward the LED head.

Dustproofing members, disclosed in the above patent documents, effectively prevent dust from landing on the exposure device, however they are not effective to counter dust which has landed and accumulated on dustproofing members themselves. The above documents do not address this problem.

Most of the image forming apparatuses are structured so that their interior can be opened for maintenance or changing components of the photoconductor, as well as a charging device, an exposure device, a developing device, and a cleaning device, all being arranged around the photoconductor. As shown by the dashed lines in FIG. 2 , some image forming apparatus are structured so that the photoconductor opens when the upper section is moved upward.

Since a laser-ray exposure device, being a complex structure, occupies much space in the image forming apparatus, said exposure device is mounted on the skeleton structure of the image forming apparatus. When the interior of the apparatus is open, most of the laser-ray exposure devices are not structured of movable sections.

On the other hand, when an LED (being a light emitting diode) exposure device is used in the image forming apparatus, said LED exposure device is preferably structured to be open by a cover.

In the above patent documents, dustproofing members are open with the exposure device, but the landed dust on dustproofing members drops onto the exposure device, whereby the exposure device becomes dusty, which is a major problem.

In order to clean the exposure device, long laborious hours are required.

The present invention has been achieved to overcome the above problem, and an object of the present invention is to provide an image forming apparatus in which the exposure device is prevented from coming dusty by the dust dropped from the dustproofing members, and maintenance is easily conducted.

The object can be attained by the items described below.

Item 1. An image forming apparatus, including:

a photoconductor,

an exposure device to expose the photoconductor,

a dustproofing member arranged upstream of an exposure position of the exposure device, in a moving direction of the photoconductor, and

a cover which supports the exposure device and the dustproofing member, wherein said cover pivots on a shaft which is arranged upstream of the exposure position in the moving direction of the photoconductor.

Item 2. An image forming apparatus, including:

a photoconductor,

an exposure device to expose the photoconductor,

a dustproofing member arranged upstream of an exposure position of the exposure device in a moving direction of the photoconductor, and

a cover which supports the exposure device and dustproofing member,

wherein said cover pivots on a shaft which is arranged downstream of the exposure position in the moving direction of the photoconductor, and wherein the dustproofing member is structured of an L-shaped member including a first dustproofing section protruding toward the photoconductor from the cover and a second dustproofing section protruding toward the exposure device from the top of the first dustproofing section.

FIG. 1 shows the structure of an image forming apparatus relating to embodiments of the present invention.

FIG. 2 shows embodiment 1 of the present invention.

FIG. 3 shows dust which landed on a dustproofing member and then dropped onto an exposure device from the dustproofing member.

FIG. 4 shows embodiment 2 of the present invention.

FIG. 5 shows embodiment 3 of the present invention.

FIG. 6 shows a color image forming apparatus relating to embodiment 4.

FIG. 7 shows drawer unit 60 .

FIG. 8 shows embodiment 5 of the present invention.

FIG. 9 shows embodiment 6 of the present invention.

The embodiments of the present invention, will be detailed below, however the invention is not limited to the embodiments.

FIG. 1 shows the structure of an image forming apparatus of the embodiments of the present invention.

The image forming apparatus, which forms an image on a recording member by an electro-photographic process, is structured of electrical charging device 2 , exposure device 3 , developing device 4 , image transfer device 5 , and cleaning device 6 , arranged in that order around photoconductor 1 , in the rotating direction of photoconductor 1 , indicated by arrow A.

At the bottom section of the image forming apparatus, sheet supplying section 8 , transfer device 5 , fixing device 7 and sheet ejecting section 9 are arranged from the left to the right in that order.

To form the image, photoconductor 1 rotates counterclockwise, as shown by arrow A, a toner image is formed on photoconductor 1 by the operations of electrical charging device 2 , exposure device 3 and developing device 4 .

In synchronizing the formation of the toner image, recording member P is conveyed from sheet supplying section 8 , whereby the toner image on photoconductor 1 is transferred onto recording member P by transfer device 5 .

The toner image, carried on recording member P, passes through fixing device 7 to be fixed via heating and pressure.

Recording member P, carrying the fixed image, is ejected onto a tray of sheet-ejection section 3 .

FIG. 2 shows embodiment 1 of the present invention, having a structure to prevent dust from landing and accumulating onto exposure device 3 .

In FIG. 2 , exposure device 3 includes an LED array in which a plurality of LED elements are arranged perpendicular to the moving direction of photoconductor 1 , and an optical element array which concentrates the outputted light rays emitted from the LEDs onto the surface of photoconductor 1 . Based on driving signals to drive the LEDs, exposure device 3 conducts a dot exposure on photoconductor 1 to form an image on photoconductor 1 .

Cover 10 , which forms an upper exterior package of the image forming apparatus, is hinged at right end section 10 a , and can be opened and closed in arrowed directions B by the operation of the operator.

Exposure device 3 is suspended from cover 10 via supporting member 12 , and dustproofing member 11 is also suspended from cover 10 .

Dustproofing member 11 is mounted upstream of exposure device 3 in the moving direction (which is shown by arrow AA), at the exposure position of photoconductor 1 . The bottom of dustproofing member 11 is closer to photoconductor 1 than the bottom of exposure device 3 .

During the rotation of photoconductor 1 shown by arrow A, airflows are generated on the surface of photoconductor 1 so as to follow the rotation of photoconductor 1 . Any loose dust in the airflow, such as toner particles, are blocked by dustproofing member 11 so that a light emitting surface of exposure device 3 is prevented from being covered by dust.

Hinge 10 a is mounted upstream of exposure device 3 in the moving direction at the exposure position, of photoconductor 1 , that is, hinge 10 a is mounted upstream of the exposure position, which corresponds to the rotation shown by arrow A, in moving direction AA.

During any maintenance work, cover 10 rotates around hinge 10 a as shown by arrow B, and changes its position from an operational position shown by solid lines to a non-operational position shown by dashed lines. Exposure device 3 and dustproofing member 11 move with cover 10 .

Dust particles “C” tends to accumulate on an upstream edge of dustproofing member 11 in moving direction AA of photoconductor 1 . Accumulated dust particles C tends to drop, specifically when cover 10 is opened or closed.

Since cover 10 rotates around hinge 10 a which is mounted upstream of exposure device 3 in moving direction AA of photoconductor 1 , dustproofing member 11 is positioned lower than exposure device 3 when cover 10 opens. Accordingly, dropped dust particles C cannot land onto exposure device 3 .

The structure of the present embodiment, that is, the structure to prevent exposure device 3 from being covered with dust particles C will now be detailed while comparing it to the structure shown in FIG. 3 .

In FIG. 3 , cover 10 is rotated in directions B 1 around hinge 10 a , which is mounted downstream of exposure device 3 in rotating direction AA of photoconductor 1 , so that cover 10 can be opened or closed as shown arrows B 1 .

In this structure, when cover 10 is opened, dustproofing member 11 is positioned above exposure device 3 .

As a result, dust particles C drop onto the light emitting surface of exposure device 3 as shown by arrow D, and exposure device becomes dusty.

In the embodiment shown in FIG. 2 , it is clear that exposure device 3 is effectively prevented from becoming dusty.

FIG. 4 shows embodiment 2 of the present invention.

In the present embodiment, dustproofing member 11 is structured of first dustproofing section 11 a and second dustproofing section 11 b which is attached on the bottom end of first dustproofing section 11 a.

A clearance is formed between the surface of photoconductor 1 and first dustproofing section 11 a , protruded from cover 10 toward the surface of photoconductor 1 , whereby airflow E following the rotation of photoconductor 1 is blocked so that dust particles C are prevented from entering the space in which exposure device 3 exists.

Second dustproofing section 11 b , protruding from the bottom end of first dustproofing section 11 a toward the peak of photoconductor 1 , prevents dust particles C from entering the space of exposure device 3 , which is the same manner as first dustproofing section 11 a . Further, as will be detailed below, dust particles C landed on dustproofing member 11 are prevented from dropping onto exposure device 3 .

In the present embodiment, hinge 10 a of cover 10 is mounted downstream of exposure device 3 in moving direction AA of photoconductor 1 .

The clearance between second dustproofing section 11 b and photoconductor 1 is narrower than the clearance between exposure device 3 and photoconductor 1 .

By such structure of second dustproofing section 11 b , the airflows, generated by being blocked by an upstream edge of first dustproofing section 11 a , in moving direction AA of photoconductor 1 , smoothly flow between photoconductor 1 and second dustproofing section 11 b , whereby dust particles C are accumulated on the upstream edge of first dustproofing section 11 a , but are not accumulated on second dustproofing section 11 b.

When cover 10 is opened while being upwardly rotated around hinge 10 a (being a pivot shaft) as shown by arrow B 2 in FIG. 4 , though dust particles C may drop by an opening movement, dust particles C can be blocked by second dustproofing section 11 b , so that dust particles C are prevented from landing on exposure device 3 .

FIG. 5 shows embodiment 3 of the present embodiment.

In the present embodiment, on both sides of exposure device 3 , that is, in moving direction AA of photoconductor 1 , dustproofing member 111 is mounted upstream of exposure device 3 , while auxiliary dustproofing member 112 is mounted downstream of exposure device 3 . Dustproofing member 111 is structure of first dustproofing section 111 a and second dustproofing section 111 b , while auxiliary dustproofing member 112 is structure of first dustproofing section 112 a and second dustproofing section 112 b.

Further, surfaces 111 br and 112 br of second dustproofing sections 111 b and 112 b , each opposing photoconductor 1 , are concavely formed to be concentric with the surface of photoconductor 1 .

Due to the above structures of second dustproofing sections 111 b and 112 b , dust particles C land at the upstream edge of second dustproofing section 111 b of dustproofing member 111 , however dust particles C are prevented from landing on other sections.

Further, when cover 10 is opened while being upwardly rotated around hinge 10 a which is mounted downstream of exposure device 3 in moving direction AA, though dust particles C may drop from dustproofing member 111 , dust particles C can be blocked by second dustproofing sections 111 b and 112 b , so that dust particles C are prevented from landing at exposure device 3 .

In the embodiment shown in FIG. 5 , since other than the light emitting section are hermetically closed by dustproofing member 111 and auxiliary dustproofing member 112 , dustproof effect for exposure device 3 is extremely high, which is advantageous.

FIG. 6 shows a color image forming apparatus relating to embodiment 4 .

The present image forming apparatus is an color image forming apparatus to form a color image on recording sheet P, including automatic document feeding device 30 which feeds a document one by one to a document reading position, image reading section 40 , and image forming section 50 .

Image reading section 40 reads out document “d”, conveyed by automatic document feeding device 30 or placed on document platen 42 , by reading elements 41 to form image data.

Image forming section 50 includes a plurality of processing units 20 Y, 20 M, 20 C and 20 K, intermediate transfer body 21 , primary transfer sections 5 Y, 5 M, 5 C and 5 K, secondary transfer section 5 A, fixing device 7 , a plurality of recording sheets storing section, and sheet ejection tray 9 .

Processing unit 20 Y to form an yellow image is structured of photoconductor 1 Y, and electrical charging device 2 Y, exposure device 3 Y, developing device 4 Y and cleaning unit 6 Y, each mounted around photoconductor 1 Y.

Processing unit 20 M to form a magenta image is structured of photoconductor 1 M, and electrical charging device 2 M, exposure device 3 M, developing device 4 M and cleaning unit 6 M, each mounted around photoconductor 1 M.

Processing unit 20 C to form a cyan image is structured of photoconductor 1 C, and electrical charging device 2 C, exposure device 3 C, developing device 4 C and cleaning unit 6 C, each mounted around photoconductor 1 C.

Processing unit 20 K to form a black image is structured of photoconductor 1 K, and electrical charging device 2 K, exposure device 3 K, developing device 4 K and cleaning unit 6 K, each mounted around photoconductor 1 K.

Intermediate transfer body 21 , being a rotatable belt, is entrained about a plurality of rollers. Fixing device 7 has a heated roller to fix the image on sheet P.

Each color image, formed by processing unit 20 Y, 20 M, 20 C and 20 K, is sequentially transferred onto rotating intermediate transfer body 21 by primary transfer sections 5 Y, 5 M, 5 C and 5 K, so that the color image is formed.

Recording sheet P, stored in recording sheet storing section 8 structured of a plurality of trays, is conveyed one by one by sheet supplying rollers 22 , and is conveyed to paired registration rollers 24 , which are in the stopped condition, via paired sheet supplying rollers 23 . Sheet P temporally stops there, after the leading edge of sheet P and the toner image on transfer body 21 precisely meet each other, paired registration rollers 24 start the rotation so that sheet P is conveyed to secondary transfer section 5 A, where a color image is formed on recording sheet P (which is a secondary transfer operation). Sheet P, on which the color image has been transferred, is heated and pressured at fixing device 7 , so that the color image is fixed on sheet P. Then, sheet P is ejected by paired ejection rollers 25 onto sheet ejection tray 9 exterior the apparatus.

After the color image was transferred onto recording sheet P by secondary transfer section 5 A, intermediate transfer body 21 , from which sheet P was separated by a sharp angled conveyance, is cleaned by cleaning device 6 A so that residual toner is removed.

Processing units 20 Y, 20 M, 20 C and 20 K are integrally formed to be a drawer unit 60 .

Drawer unit 60 can be pulled toward the operator, which is the depth direction of FIG. 6 .

FIG. 7 shows drawer unit 60 .

After drawer unit 60 is pulled out from the image forming apparatus, cover 10 can be rotated around hinge 10 a to open upwardly, whereby processing unit 20 Y, 20 M, 20 C and 20 K are checked for the maintenance.

Hinge 10 a of cover 10 exists more upstream than exposure device 3 Y, 3 M, 3 C and 3 K in the moving direction at the exposure positions of photoconductors 1 Y, 1 M, 1 C and 1 K.

Exposure devices 3 Y, 3 M, 3 C and 3 K of processing units 20 Y, 20 M, 20 C and 20 K are structured of LED arrays and optical element arrays, which are the same as the image forming apparatus in FIG. 1 .

In the moving direction at the exposure positions of photoconductors 1 Y, 1 M, 1 C and 1 K, dustproofing members 11 , arranged upstream of exposure devices 3 Y, 3 M, 3 C and 3 K respectively, can prevent dust particles C from landing on the light emitting surfaces of exposure devices 3 Y, 3 M, 3 C and 3 K. Further, as detailed for the image forming apparatus of FIG. 1 , when cover 10 opens, dust particles C, landed on dustproofing members 11 , are prevented from dropping onto exposure devices 3 Y, 3 M, 3 C and 3 K.

FIG. 8 shows embodiment 5 of the present invention.

In embodiment 5 , dustproofing member 11 and auxiliary dustproofing member 13 are mounted to sandwich exposure device 3 .

The clearance between the top of auxiliary dustproofing member 13 and surface of photoconductor 1 is greater than the clearance between the top of dustproofing member 11 and the surface of photoconductor 1 .

Accordingly, while photoconductor 1 rotates, dust do not land on auxiliary dustproofing member 13 .

As shown in FIG. 8 , dustproofing member 11 and auxiliary dustproofing member 13 are mounted for processing units 20 Y, 20 M, 20 C and 20 K, respectively.

As shown in FIG. 8 , cover 10 opens up to dashed lined position 101 , or further upper to dashed lined position 102 .

When cover 10 rotates up to position 102 , cover 10 is approximately vertical, whereby exposure device 3 M comes lower than dustproofing member 11 of exposure device 3 Y, exposure device 3 C comes lower than dustproofing member 11 of exposure device 3 M, and exposure device 3 K comes lower than dustproofing member 11 of exposure device 3 C.

As results, dust particles C may drop from dustproofing members 11 to exposure devices 3 M, 3 C and 3 K.

Further, when cover 10 opens, auxiliary dustproofing members 13 prevent dust particles C, which drop from upper-positioned dustproofing member 11 , from landing at lower-positioned exposure device 3 .

FIG. 9 shows embodiment 6 of the present invention.

In the present embodiment, cover 10 rotates around hinge 10 a which is mounted at downstream of the exposure devices 3 Y, in the moving direction of photoconductor 1 Y at the exposure position.

Further in the present invention, dustproofing member 111 and auxiliary dustproofing member 112 are provided at both sides of each of exposure devices 3 Y, 3 M, 3 C and 3 K.

Still further, dustproofing member 111 includes first dustproofing section 111 a and second dustproofing section 111 b , while auxiliary dustproofing member 112 includes first auxiliary dustproofing section 112 a and second auxiliary dustproofing section 112 b.

As described in FIG. 5 , though hinge 10 a of cover 10 is provided downstream of the moving direction of photoconductor 1 , due to dustproof effects of first dustproofing sections 111 a and 112 a , as well as second dustproofing sections 111 b and 112 b , while the operator opens or closes cover 10 , dust particles C are effectively prevented from landing at the light emitting sections of exposure devices 3 Y, 3 M 3 C and 3 K.