JPH10116012A - Image forming machine and processing unit applied thereto - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent toner scraped down by a foreign matter recovering brush from being accumulated on the upper surface of an electrifier by providing a toner infiltration preventing wall between the electrifier and the foreign matter recovering brush. SOLUTION: The electrifier 43 is composed of a corona discharger for electrification and consists of a grid member 431 and a grid holding member 432. The upper end of the member 432 is formed to be projecting to approach to the peripheral surface of a photoreceptor drum 42, and constitutes the toner infiltration preventing wall 47. In the case residual toner removed with the foreign matter such as paper powder by the foreign matter recovering brush 44 drops, the wall 47 prevents the dropped toner from infiltrating in the corona discharger for electrification 43. The toner whose movement to the electrifier 43 is interrupted is accumulated in a horizontal piece part near the wall 47 of a brush supporting member 440.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention develops an electrostatic latent image formed on a photosensitive layer of a photosensitive drum such as an electrostatic copying machine or a laser printer into a toner image and transfers the toner image to a transfer paper. The present invention relates to an image forming apparatus and a process unit applied thereto.

[0002]

2. Description of the Related Art An image forming machine of this type is provided rotatably and sequentially passes through a charging area, an electrostatic latent image forming area, a developing area and a transfer area. A charger for charging the peripheral surface of the photosensitive drum to a specific polarity; and a developing device disposed in the developing area and developing the electrostatic latent image formed on the peripheral surface of the photosensitive drum in the electrostatic latent image forming area into a toner image. The apparatus includes an apparatus and a transfer unit that is provided in the transfer area and transfers a toner image formed on the peripheral surface of the photosensitive drum to transfer paper. In an image forming apparatus of this type, the position of each area changes depending on whether the transfer paper passes over or under the photosensitive drum. Generally, a configuration in which the transfer paper passes below the photosensitive drum is often used. In this case, the transfer area is located below the photosensitive drum, so the charging area is located above the photosensitive drum. Will be located. Also,
In the type in which the transfer paper is passed above the photosensitive drum, the transfer area is configured to be located above the photosensitive drum, so that the charged area is located below the photosensitive drum.

[0003]

Thus, in an image forming apparatus in which the toner remaining on the peripheral surface of the photosensitive drum that has passed through the transfer area is collected by a developing device, the photosensitive member is transferred during transfer. If foreign matter such as paper dust attached to the peripheral surface of the drum is collected together with the toner in the developing device, the subsequent image quality will be degraded. Therefore, a proposal has been made to dispose a foreign matter collecting brush between the charging area and the transfer area to remove foreign matter such as paper dust adhered to the peripheral surface of the photosensitive drum. However, it is desirable that the foreign matter collection brush removes only foreign matter such as paper dust and passes the residual toner attached to the peripheral surface of the photosensitive drum. However, the residual toner may be scraped off. There is no problem if the scraped residual toner is reliably captured by the foreign matter collecting brush, but most of the toner drops because the particles are smaller than foreign matter such as paper powder. Therefore, in an image forming apparatus in which the charging area is located below the photosensitive drum, the toner scraped off by the foreign matter collecting brush accumulates on the upper surface of the charger provided in the charging area. When toner accumulates on the upper surface of the charger, uneven charging occurs, which causes image defects.

[0004] The present invention has been made in view of the above-mentioned facts, and its main technical problem is that the charging area is located below the photosensitive drum, and the charging area and the transfer area are different. Even if the residual toner removed together with the foreign matter from the peripheral surface of the photosensitive drum by the foreign matter collection brush disposed between the photosensitive drum and the toner falls, it is possible to prevent the toner from being deposited on the charger arranged in the charging area. And a process unit of the image forming apparatus.

[0005]

According to the present invention, in order to attain the above-mentioned main technical problems, the present invention is arranged rotatably and sequentially passes through a charging area, an electrostatic latent image forming area, a developing area and a transfer area. A photosensitive drum, a charger disposed in the charging area and charging the peripheral surface of the photosensitive drum to a specific polarity, and a peripheral surface of the photosensitive drum disposed in the developing area and in an electrostatic latent image forming area A developing device for developing the electrostatic latent image formed on the photosensitive drum into a toner image, and a transfer means provided in the transfer area for transferring the toner image formed on the peripheral surface of the photosensitive drum to transfer paper. Wherein the charging area is defined below the photosensitive drum, and a foreign matter collecting brush is provided between the charging area and the transfer area to contact a peripheral surface of the photosensitive drum. Between the charger disposed in the charging area and the foreign matter collecting brush Upper end on the peripheral surface comprises a toner entrance preventing wall disposed close to the photosensitive drum, the image forming apparatus is provided, characterized in that.

Further, according to the present invention, a photosensitive drum rotatably disposed and sequentially passing through a charging area, an electrostatic latent image forming area, a developing area, and a transfer area, and a photosensitive drum defined below the photosensitive drum. A charger arranged in the charged area and charging the peripheral surface of the photosensitive drum to a specific polarity; and a charger arranged in the developing area and formed on the peripheral surface of the photosensitive drum in an electrostatic latent image forming area. Forming apparatus for developing an electrostatic latent image into a toner image, and a foreign matter collecting brush disposed between the charging area and the transfer area and in contact with a peripheral surface of the photosensitive drum. A process unit comprising: a toner intrusion prevention wall disposed at an upper end close to the peripheral surface of the photosensitive drum between the charger and the foreign matter collecting brush disposed in the charging area. A process unit for an image forming machine is provided.

Further, according to the present invention, the toner intrusion prevention wall is formed of a film member, and the image forming apparatus or a process unit of the image forming apparatus is mounted on a charger holding member for holding the charger. Is provided.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an image forming machine constructed according to the present invention will be described in detail with reference to the accompanying drawings. In the illustrated embodiment, a printer will be described as an example of an image forming apparatus configured according to the present invention.

FIG. 1 schematically shows an embodiment of a printer constructed according to the present invention. Printer 2
Is a small and low-speed laser printer used as a printing device such as a word processor in this embodiment, and includes a body housing 20 made of synthetic resin.
Is provided. The body housing 20 includes a box-shaped housing main body 21 whose upper part is open, and a cover 23 pivotally mounted on a shaft 22 provided on the upper part of the housing main body 21. The process unit 4 is detachably mounted at a substantially central portion of the body housing 20 configured as described above.

As shown in FIG. 2, the process unit 4 includes a photosensitive unit 40 and a developing unit 50 swingably supported by the photosensitive unit 40 via a support shaft 5.
And The photoreceptor unit 40 includes a photoreceptor support means 41, and the photoreceptor support means 41 is provided with a pair of side wall members 411 spaced apart in the front-rear direction (only the rear side wall member is shown in FIG. 2). (Shown) and a connecting member 412 connecting the lower portions of the pair of side wall members 411.
a, 412b. The connecting members 412a and 412b are provided with a charger mounting space 41 in which the inner surfaces facing each other are disposed in parallel and a charger described later is disposed therebetween.
2c is formed. This charging device mounting space 412c is
It is located opposite a charging area described later. The photoconductor supporting means 41 thus configured is integrally formed of a synthetic resin. Support portions 413 each having a mounting hole 414 are provided at the upper end of the pair of side wall members 411 constituting the photosensitive member support means 41 on the developing unit 50 side. By inserting a support shaft 5 made of a metal bar disposed in a later-described developing housing of the developing unit 50 into a mounting hole 414 provided in the supporting portion 413, the photosensitive unit 40 and the developing unit 50 can be connected to each other. Is swingably supported.

The photoreceptor unit 40 has a photoreceptor drum 42 having a photosensitive layer formed on a peripheral surface. The photosensitive drum 42 has a rotating shaft 421. The rotating shaft 421 is rotatably supported by a pair of side wall members 411 constituting the photosensitive member supporting means 41. That is, it is driven to rotate so as to sequentially pass through the charging area 422, the electrostatic latent image forming area 423, the developing area 424, and the transfer area 425. Charge area 422
Is mounted in the charging means mounting space 412c, which is located at a position opposite to the lower peripheral surface of the photosensitive drum. In the illustrated embodiment, the charger 43 is constituted by a charging corona discharger disposed along the axial direction in parallel with the photosensitive drum 42, and holds the grid member 431 and the grid member 431. The grid holding member 432 is made of a synthetic resin, and the grid member 43 is detachably mounted on the grid holding member 432. Charging means 4 configured in this way
Reference numeral 3 denotes a grid holding member 432 which is connected to the charger mounting space 4.
12c is positioned at a predetermined position by fitting and mounting. Further, the charging area 422 and the transfer area 425
A foreign matter collecting brush 44 that comes into contact with the peripheral surface of the photosensitive drum 42 is disposed along the axial direction of the photosensitive drum 42. The paper dust collecting brush 44 is made of acrylic fiber or the like and has substantially the same length as the length of the photosensitive drum 42 in the axial direction. The brush 44 is integrally formed with the grid holding member 432 and extends along the axial direction of the photosensitive drum 42. It is attached to the brush support member 440 arranged. In the illustrated embodiment, the upper end of the grid holding member 432 approaches the peripheral surface of the photosensitive drum 42 between the charging corona discharger 431 disposed in the charging area 422 and the foreign matter collecting brush 44. As a result, the toner intrusion prevention wall 47 is formed. The toner intrusion preventing wall 47 is attached to the peripheral surface of the photosensitive drum 42 and is removed by the foreign matter collecting brush 44 together with the foreign matter such as paper dust. In addition, it has a function of preventing intrusion on the charging corona discharger 431. If the upper end of the toner intrusion prevention wall 47 is in contact with the peripheral surface of the photosensitive drum 42, residual toner adhering to the peripheral surface of the photosensitive drum 42 may be scraped off. It is desirable that the upper end of 47 be as close as possible without contacting the peripheral surface of the photosensitive drum 42. According to experiments by the present inventors, the toner intrusion prevention wall 47
Is 1.0 mm between the upper end of the photosensitive drum 42 and the peripheral surface thereof.
It has been found that by providing a gap of about 2.0 mm, the toner scraped off by the foreign matter collecting brush 44 can be reliably prevented from entering the charging corona discharger 431 side. The toner scraped off by the foreign matter collecting brush 44 and blocked from moving toward the charging corona discharger 431 by the toner intrusion prevention wall 47 accumulates on a horizontal portion of the brush support member 440 near the toner intrusion prevention wall 47. Will do.

Next, another embodiment of the toner intrusion prevention wall will be described with reference to FIG. The toner intrusion prevention wall 470 shown in FIG. 3 is formed of a flexible and elastic film member such as a polyethylene terephthalate (PETP) resin film, and the lower end thereof has a grid member 431 constituting the charging corona discharger. Is adhered by a fixing means such as an adhesive or a double-sided adhesive tape. Therefore, the film member forming the toner intrusion prevention wall 470 is attached to and detached from the grid holding member 432 together with the grid member 431. The grid member 43
1 is attached to the grid holding member 432, the upper end of the film member forming the toner intrusion prevention wall 470 is 1.0 mm or less from the peripheral surface of the photosensitive drum 42.
It is positioned with a gap of about 2.0 mm. As in the embodiment shown in FIG. 3, the toner intrusion prevention wall 470 is formed of a film member, and the charging corona discharger 43 is used.
By using an adhesive or a double-sided adhesive tape or the like attached to the grid member 431 constituting the above, the management of the gap with the peripheral surface of the photosensitive drum 42 becomes easy. The film member constituting the toner intrusion prevention wall 470 is formed by the grid member 4 constituting the charging corona discharger 43.
It may be mounted on a grid holding member 432 holding the 31.

The transfer paper fed from diagonally upper left in FIG. 2 is directed to a transfer area 425 on the peripheral surface of the photosensitive drum 42 between a pair of side wall members 411 constituting the photosensitive member support means 41. A lower guide plate 451 that constitutes one of the pre-transfer guide plate pair 45 that guides the lower guide plate 451 is provided, and the lower guide plate 451 is integrally formed with the pair of side wall members 411. A plurality of guide ribs 451a are integrally formed on the upper surface of the lower guide plate 451 at intervals in the longitudinal direction (the direction perpendicular to the paper surface in FIG. 2). The lower guide plate 451 is also provided with a plurality of reinforcing ribs 45 on the lower surface at intervals in the longitudinal direction (the direction perpendicular to the paper surface in FIG. 2).
1 b is integrally formed, and the reinforcing rib 451 b is configured to abut on the support shaft 5. Therefore,
Even if the lower guide plate 451 is pressed by the upper surface thereof and bends, the reinforcing ribs 451b abut on the support shaft 5 to prevent the lower guide plate 451 from bending. Also, the lower guide plate 451
Is a pair of side wall members 41 constituting the photoreceptor support means 41.
1 serves as a connecting member for connecting the upper portions to each other, and the rigidity of the photosensitive member supporting means 41 can be improved. Further, in the illustrated embodiment, since the lower guide plate 451 is integrally formed with the pair of side wall members 411, the positional relationship with respect to the photosensitive drum 42 rotatably supported by the pair of side wall members 411 can be determined with high precision. Can be maintained. Note that the lower guide plate 4 in the illustrated embodiment is used.
Numeral 51 functions as a member for preventing the photosensitive drum 42 from contacting the photosensitive layer when the process unit 4 is attached and detached, and also functions as a member for preventing the developing unit 50 from touching a later-described developing roller. It also has a function of preventing toner scattered from the surface of the roller from adhering to the transfer paper or the transfer path of the transfer paper.

A post-transfer guide plate 46 for guiding the transfer paper transferred in the transfer area 425 to a fixing means described later is disposed between the pair of side wall members 411 constituting the photosensitive member supporting means 41. The post-transfer guide plate 46 is formed integrally with the pair of side wall members 411. Therefore, the post-transfer guide plate 46 functions as a connecting member for connecting the pair of side wall members 411 constituting the photoconductor supporting unit 41 to each other, and can improve the rigidity of the photoconductor supporting unit 41. The post-transfer guide plate 4 in the illustrated embodiment.
6 can also function as a contact preventing member for the photosensitive layer of the photosensitive drum 42 when the process unit 4 is attached or detached.

Next, the developing unit 50 as an electrostatic latent image developing device will be described. The developing unit 50 in the illustrated embodiment includes a developing housing 51 in which a developer composed of one-component toner is stored. The developing housing 51 has a bottom wall 511 and a front wall and a rear wall 512 (FIG. 2) formed to stand upright from front and rear ends (ends in a direction perpendicular to the paper surface in FIG. 2) of the bottom wall 511.
Only the rear side wall) and a left side wall 513, which are integrally formed of a synthetic resin and define a stirring chamber 514 and a developing chamber 515. A stirring chamber 51 is provided on a bottom wall 511 of the developing housing 51.
A partition wall 516 provided in the front-rear direction (the direction perpendicular to the paper surface in FIG. 2) between the developing chamber 4 and the developing chamber 515 is integrally formed. Both left and right surfaces of the partition wall 516 are formed on arcuate guide surfaces 516a and 516b. Between the front and rear side walls 512 constituting the developing housing 51, a connecting member 517 provided at the upper part on the side of the developing chamber 515 is provided, and is formed integrally with the front and rear side walls 512. A toner supply hole 518 is formed in the rear side wall 512 of the developing housing 51.
8 is fitted with a cap 519. At the upper end of the developing housing 51 on the side of the developing chamber 515, the support shaft 5 is provided so as to penetrate the front and rear side walls 512. The photosensitive unit 4 is provided at both ends of the support shaft 5.
A pair of side wall members 41 constituting the photosensitive member supporting means 41
By fitting the mounting holes 414 provided in the first support portion 413, the photoconductor unit 40 and the developing unit 50 are supported so as to be able to swing mutually. The photoconductor unit 4
0 and the developing housing 51
A coil spring 52 serving as a spring means is interposed between the front end and the rear end of the photosensitive member supporting means 41 and the developing housing 5.
Numerals 1 are urged to draw each other with the support shaft 5 as a fulcrum. The developing housing 51 is open above and to the right, that is, on the photoconductor unit 40 side.

In the developing housing 51, a developing roller 53, a supply roller 54, a stirring means 55 and a developer regulating means 56 are provided. The developing roller 53 is
A rotating shaft 531 provided in the developing chamber 515 of the developing housing 51 and rotatably mounted on the front and rear side walls 512 constituting the developing housing 51, and a solid synthetic rubber roller fixed to the outer peripheral surface of the rotating shaft 531 532. The rotating shaft 531 can be formed from an appropriate metal material such as stainless steel. Solid synthetic rubber roller 53
2 is made of a relatively flexible and conductive material, for example, a conductive solid synthetic rubber such as urethane rubber. In the illustrated embodiment, a solid synthetic rubber roller 5 is used.
The surface roughness of the peripheral surface of No. 32, that is, the ten-point average roughness Rz specified in JIS B 0601 is set to 5.0 to 12.0. The volume resistance of the solid synthetic rubber roller 532 is set to about 10 ⁴ to 10 ⁹ Ω · cm. The roller hardness of the solid synthetic rubber roller 532 is set to 60 to 80 in Asker C hardness in the illustrated embodiment. The roller 532 of the developing roller 53 configured as described above is exposed through a right opening formed in the developing housing 51, and is exposed to the photosensitive drum 42.
Is positioned opposite to. The peripheral surface of the roller 532 constituting the developing roller 53 is pressed against the peripheral surface of the photosensitive drum 42 in the developing region, and the peripheral surface of the roller 532 is slightly elastically compressed at the pressed nip. ing. Rotating shaft 53 of developing roller 53
1 is driven to rotate from the lower side to the upper side in a direction indicated by an arrow by a driving unit (not shown), that is, in a developing area which is a contact portion between the roller 532 and the photosensitive drum 42. The rotation of the rotation shaft 531 causes the roller 532 to rotate.
The roller 532 is also driven to rotate in the direction indicated by the arrow, and the peripheral surface of the roller 532 is sequentially moved through the developer holding area 533, the developer regulating area 534, and the developing area 424. In the illustrated embodiment, a constant voltage of 300 V is applied to the rotating shaft 531 of the developing roller 53.

The replenishing roller 54 is disposed in the developing chamber 515 of the developing housing 51 in parallel with the developing roller 53, and is rotatably mounted on the front and rear side walls 512 constituting the developing housing 51. A shaft 541;
And a roller 542 fixed to the outer peripheral surface of the rotating shaft 541. The rotating shaft 541 can be formed of an appropriate metal material such as stainless steel, similarly to the rotating shaft 531 of the developing roller 53. The roller 542 is made of foam such as foamed silicone or foamed urethane. The roller 542 is a roller 5 of the developing roller 53 in a developer holding region 533 which is a nip portion with the developing roller 53
32. Roller 54 of supply roller 54
The hardness of the foam constituting the developing roller 2 is considerably smaller than the hardness of the roller 532 constituting the developing roller 53 (for example, about 35 in Asker C hardness), and the roller 542 is pressed against the roller 532 of the developing roller 53. It is desirable that the roller 542 be elastically compressed by about 0.1 to 0.6 mm in the nip area. Roller 5
42 also has conductivity, and its volume resistance is 10 ² to 1
It is set to about 0 ⁶ Ω · cm. The rotating shaft 541 of the replenishing roller 54 is rotated from the upper side to the lower side in a direction indicated by an arrow by a driving unit (not shown), that is, in a developer holding area 533 which is a nip portion between the roller 542 and the roller 532 of the developing roller 53. I'm sullen. Rotary axis 5
Due to the above rotation of the roller 41, the roller 542 is also driven to rotate in the direction shown by the arrow. In the illustrated embodiment,
The rotation shaft 541 of the supply roller 54 has the developing roller 53
A constant voltage of 450 V, which is higher than the applied voltage, is applied.

The peripheral speed V1 of the photosensitive drum 42, the peripheral speed V2 of the developing roller 53, and the peripheral speed V3 of the replenishing roller 54 are set in a relationship of V1 <V2 <V3.
In the illustrated embodiment, the relationship between the peripheral speed V1 of the photosensitive drum 42 and the peripheral speed V2 of the developing roller 53 is as follows.
1.2V1 ≦ V2 ≦ 2.5V1, the peripheral speed V2 of the developing roller 53 and the peripheral speed V3 of the replenishment roller 54 are set.
Is set to be 1.0V2 ≦ V3 ≦ 2.0V2. When the peripheral speed V2 of the developing roller 53 becomes 1.2 V1 or less, the supply of the developer to the photosensitive drum 42 becomes insufficient, and the image density is reduced. When the peripheral speed V2 of the developing roller 53 becomes 1.2 V1 or less, the scraping action of the developing roller 53 against the non-transferred developer attached to the photosensitive drum 42 after the transfer is reduced. This causes a so-called offset fog to occur because the photoreceptor drum 42 cannot be removed. On the other hand, when the peripheral speed V2 of the developing roller 53 becomes 2.5 V1 or more, the driving torque of the developing roller 53 increases, and the developer is scattered by centrifugal force. Further, when the peripheral speed V3 of the supply roller 54 becomes 1.0 V2 or less, the supply of the developer to the developing roller 53 becomes insufficient, which causes a decrease in image density. Also, the peripheral speed V of the supply roller 54
When the voltage of the transfer roller 3 becomes 1.0 V2 or less, the non-transferred developer adhered to the photosensitive drum 42 adheres to the developing roller 53 after the transfer because the action of scraping the peripheral surface of the developing roller 53 by the supply roller 54 is weak. It becomes difficult to remove the adhered developer, and the adhered developer causes a so-called ghost phenomenon that appears during the next development. On the other hand, when the peripheral speed V3 of the supply roller 54 becomes 2.0 V2 or more, the supply roller 54
, The developer tends to stay above the nip portion between the supply roller 54 and the developing roller 53, which causes a shortage of the developer supply to the developing roller 53.

In the stirring chamber 514 of the developing housing 51, a stirring means 55 is provided. The stirring means 55
A rotating shaft 551 rotatably mounted on the front and rear side walls 512 constituting the developing housing 51, a stirring member 552 fixed to the rotating shaft 551, and An elastic stirring sheet member 553 attached to the stirring member 552 is included.
The stirring member 552 is formed of a synthetic resin,
A plurality of openings are provided in a longitudinal direction (a direction perpendicular to the paper surface in FIG. 2). The stirring sheet member 553 is made of, for example, polyethylene terephthalate (PET) having flexibility and elasticity.
P) It is formed of resin, and is fixed to the edge of the tip of the stirring member 552 by an adhesive or the like. The stirring means 55 thus configured is continuously driven to rotate in a direction indicated by an arrow in FIG. 2 by a driving means (not shown).

The developer regulating means 56 includes a flexible elastic blade 561 which is pressed against the peripheral surface of the roller 532 constituting the developing roller 32.
The blade 561 has a thickness of, for example, 0.1 to 0.2 mm.
The length of the roller 532 constituting the developing roller 53 is substantially the same as the length in the longitudinal direction. Blade 561
Is a bottom wall 5 whose base end constitutes the developing housing 51.
11 is attached to the blade mounting portion 511a provided at the open end of the photoconductor unit 40 side. That is, the blade 561
The base end of the blade mounting portion 511a and the holding plate 562
And fixed by screws 563. The distal end of the blade 561 is bent, and the bent portion is configured to be pressed against the peripheral surface of the roller 532 constituting the developing roller 53 in the developer regulating region 534.

The developing housing 51 is provided with a lid 57 for covering the opened upper part. The lid 57 is made of a synthetic resin, and is fixed to an upper surface of the front and rear side walls 512, the left side wall 513, and the upper surface of the connecting member 517 constituting the developing housing 51 by an adhesive. A regulating portion 571 that extends in the front-rear direction (a direction perpendicular to the paper surface in FIG. 2) and protrudes toward the developing chamber 515 is integrally formed on the inner surface of the lid 57 at a position facing the supply roller 54. A predetermined interval is provided between the lower end of the regulating portion 571 and the outer peripheral surface of the roller 542 constituting the supply roller 54. In the illustrated embodiment, a sheet-shaped seal member 58 is attached to the connecting member 517 constituting the developing housing 51. The sheet-shaped sealing member 58 is made of, for example, polyethylene terephthalate (P
It is made of a sheet member having flexibility and elasticity, such as ETP) resin, and has substantially the same length as the axial length of the roller 532 constituting the developing roller 53. One end of the sheet-shaped sealing member 58 is connected to the connecting member 517.
Is fixed to the developing roller 53 by a fixing means such as an adhesive.
2 is elastically brought into contact with the peripheral surface. The sheet-shaped sealing member 58 thus configured is provided together with the blade 561 of the developer regulating means 56 on the developing housing 5.
The developer is prevented from scattering from the opening on the side of the photoconductor unit 40.

The process unit 4 configured as described above is detachably mounted on the body housing 20 of the printer 2 as shown in FIG. That is, the upper part of the housing main body 21 constituting the body housing 20 is opened by turning the cover 23 constituting the body housing 20 of the printer 2 around the axis 22 counterclockwise in FIG. Next, the process unit 4 is mounted in the housing body 21 from above. The housing body 21
Inside, a positioning means (not shown) capable of mounting the photoconductor unit 40 of the process unit 4 at a predetermined position is provided. The process unit 4 is connected to the body housing 20.
When the cover 22 is attached to the housing body 21 of the
By turning clockwise in FIG. 1 around two directions, the upper part is closed.

As shown in FIG. 1, a lower part of a housing body 21 constituting a body housing 20 of the printer 2 is provided with:
A laser unit 24 is provided. The laser unit 24 irradiates the photosensitive layer of the photosensitive drum 42 with a laser beam corresponding to print data from, for example, a word processor connected to the printer 2 in the electrostatic latent image forming area 423 of the process unit 4, Form a latent image. A fixing roller pair 25 is disposed on the downstream side of the post-transfer guide plate 46 on the housing body 21 constituting the body housing 20 of the printer 2, and a discharge roller pair 26 is disposed on the downstream side of the fixing roller pair 25. Are arranged. Further, a discharge tray 27 is provided downstream of the discharge roller pair 26.

A cover 23 constituting the body housing 20 of the printer 2 is provided with a paper feed tray 28 on which transfer paper is placed at the upper left side in FIG. A paper feed roller 29 is provided downstream of the paper feed tray 28,
The paper feed roller 29 is driven to rotate in a direction indicated by an arrow in FIG. A friction pad 30 for separating sheets is provided opposite to the sheet feeding roller 29. Further, a non-contact type transfer roller 31 is provided in the transfer area 422 so as to face the photosensitive drum 42. The transfer roller 31 is formed of conductive urethane foam, and is rotatably supported by the cover 23. The transfer roller 31 is provided with collars (not shown) made of an insulating material such as a synthetic resin having an outer diameter larger than that of the transfer roller 31 at both ends thereof, and the collars are arranged in contact with the peripheral surface of the photosensitive drum 42. Has been
Accordingly, the transfer roller 31 is driven to slide while the photosensitive drum 42 rotates. The gap between the peripheral surface of the transfer roller 31 and the peripheral surface of the photosensitive drum 42 is 0.5 m.
m. A constant current of, for example, 10 μA is applied to the transfer roller 31 configured as described above.
An upper guide plate 452 constituting the other of the pre-transfer guide plate pair 45 is disposed on the cover 23.

The printer 2 in the illustrated embodiment is configured as described above, and its operation will be described below. Each of the above members starts to operate based on a print command from a word processor (not shown) or the like, and the charging corona discharger 4
3, the surface photosensitive layer of the photosensitive drum 42 is substantially uniformly charged to a specific polarity. Next, a laser beam corresponding to print data from a word processor or the like is emitted from the laser unit 24 to the charged surface of the photosensitive layer of the photosensitive drum 42, and an electrostatic latent image is formed. The electrostatic latent image thus formed on the photosensitive layer of the photosensitive drum 42 is developed into a toner image by the developing operation of the developing unit 50. The developing operation of the developing unit 50 is described below.
Details will be described later. On the other hand, the transfer paper placed on the paper feed tray 28 is fed one by one by the action of the paper feed roller 29 and the friction pad 30. Then, the transfer paper is guided by the pre-transfer guide plate pair 45 and the photosensitive drum 42 and the transfer roller 3.
1 and the toner image formed on the photosensitive drum 42 is transferred onto the surface thereof. The transfer paper on which the toner image has been transferred is guided by the guide plate 46 after the transfer, and is conveyed to the fixing roller pair 25. The transfer paper on which the toner image has been heated and fixed by the fixing roller pair 25 is discharged onto a discharge tray 27 by the discharge roller pair 26. On the other hand, when the peripheral surface of the photosensitive drum 42 that has passed through the transfer area 425 passes through the foreign matter collecting brush 44, foreign matter such as paper dust adhered to the peripheral surface is removed by the foreign matter collecting brush 44. At this time, a part of the residual toner adhering to the peripheral surface of the photosensitive drum 42 is removed together with the foreign matter such as paper dust. The removed residual toner may fall without being reliably captured by the foreign matter collecting brush 44. If the dropped toner accumulates on the grid member 431 of the charging corona discharger 43, it causes charging unevenness. In the illustrated embodiment, the toner intrusion preventing wall 47 (470) prevents the grid member from dropping the toner. 431 is prevented from entering. The residual toner adhering to the peripheral surface of the photosensitive drum 42 that has passed through the foreign matter collecting brush 44 is collected by the developing roller 53.

Next, the developing operation of the developing unit 50 will be described. By starting the operation of the developing unit 50,
The developing roller 53, the supply roller 54, and the stirring means 5
5 are rotationally driven in directions indicated by arrows by drive means (not shown). Stirring member 55 constituting stirring means 55
2 and the stirring sheet member 553 rotate in the direction indicated by the arrow, the developer accommodated in the stirring chamber 514 passes over the partition wall 516 while being stirred, and
Is supplied into the developing chamber 514 from above. At this time, the regulating portion 571 formed on the inner surface of the lid 57 causes
The amount of the developer supplied into the developing chamber 514 is limited so as not to be excessive. The developer supplied by the agitating unit 55 in this manner rides on the roller 542 of the supply roller 54 and is transported to the nip portion which is the developer holding area 533 with the roller 532 of the developing roller 53. Since the supply roller 54 and the developing roller 53 rotate in the same direction from the upper side to the lower side in the developer holding area 533 which is a nip portion as described above, the supply roller 54 and the developing roller 53
The developer is sufficiently supplied to the developer, and the shortage of the developer can be prevented. The replenishing roller 54 and the developing roller 5
3 is a developer holding area 533 which is a nip portion as described above.
, The motor can be driven reliably without requiring a large driving force.

As described above, the developer conveyed to the developer holding area 533, which is a nip portion between the supply roller 54 and the developing roller 53, is supplied to the roller 53 constituting the developing roller 53.
2 and is conveyed toward the developer regulating area 534. At this time, the supply roller 54 and the developing roller 53
Are rotated in the same direction from the upper side to the lower side in the developer holding area 533 which is the nip portion as described above, so that the developer is held by the developing roller 53 through both nip portions, and the developer is regulated. Since the toner is conveyed to the developing area 534 and the developing area 424, they are rubbed against each other when passing through the nip portion, and are sufficiently charged.

In the developer regulating area 534, the blade 561 of the developer regulating means 56 acts on the developer retained on the peripheral surface of the roller 532 of the developing roller 53 and is retained on the peripheral surface of the roller 532. The developer is regulated to a required amount to form a thin layer. The developer regulated in the developer regulating area 534 by the blade 561 of the developer regulating means 56 and scraped off on the bottom wall 511 of the developing housing 51 is rotated by the supply roller 54 in the direction shown by the arrow. The partition wall 516 without stopping
Along the guide surface 516b. The toner is collected by the developing roller 53 in the developing area 424.

As described above, the developer is held on the peripheral surface of the roller 532 constituting the developing roller 53 in the developer holding area 533, and is formed in a thin layer by the action of the blade 561 of the developer regulating means 56 in the developer regulating area 534. The urged developer is rotated in the direction of the arrow, and the developing area 424 is rotated.
Transported to In the development area 424, a developer is applied to the electrostatic latent image on the electrostatic photoconductor disposed on the peripheral surface of the photoconductor drum 42, and the electrostatic latent image is developed into a toner image. For example, an electrostatic latent image has a non-image area charged to about +600 V and an image area charged to about +120 V, and toner as a developer is attached to the image area (so-called reversal development). The photosensitive drum 42 and the developing roller 53 are driven to rotate in the direction indicated by the arrow in FIG. 2. Therefore, the peripheral surface of the photosensitive drum 42 and the roller 5 forming the developing roller 53 in the developing area 424.
Both of them are moved from the lower side to the upper side in the same direction. The peripheral speed V2 of the roller 532 and the photosensitive drum 4
2 is set to 1.2V1 ≦ V2 ≦ 2.5V1, so that a sufficient amount of developer is conveyed to the developing area 424 by the rollers 532 of the developing roller 53, and the peripheral speed of the photosensitive drum 42 is changed. The developer that once adhered to the non-image portion of the electrostatic latent image is appropriately peeled off by the rubbing action of the peripheral surface of the roller 532 against the surface, so that a good toner image having an appropriate development density and no fogging can be obtained. Obtainable. On the other hand, a roller 532 constituting the developing roller 53
The developer used after passing through the developing area 424 is transferred to the surface of the supply roller 54 at the nip portion between the development roller 53 and the supply roller 54. Since the peripheral speed of the supply roller 54 is set to be higher than the peripheral speed of the developing roller 53, the developer is moved in the nip portion. The adhesive force of the transfer developer can be weakened and collected, so that a so-called ghost caused by the non-transfer developer adhered to the developing roller 53 can be prevented.

Although the present invention has been described based on the embodiment in which the present invention is applied to a printer, the present invention is not limited to the illustrated embodiment, and can be applied to, for example, an electrostatic copying machine. Various changes or modifications can be made without departing from the scope of the technical idea of the present invention.

[0031]

Since the image forming apparatus and the process unit of the image forming apparatus according to the present invention are constructed as described above, the following effects can be obtained.

That is, according to the present invention, a foreign matter collecting brush which is in contact with the peripheral surface of the photosensitive drum is provided between the charging area defined below the photosensitive drum and the transfer area. In an image forming machine or a process unit of an image forming machine provided with a foreign matter collecting brush which comes into contact with the peripheral surface of the photosensitive drum between the transfer area and the transfer device, the foreign matter collecting brush is provided between the charging device and the foreign matter collecting brush. Since the toner intrusion prevention wall is provided with the upper end close to the surface, the residual toner removed together with the foreign matter such as paper dust by the foreign matter collecting brush is not reliably caught by the foreign matter collecting brush and falls. The toner intrusion prevention wall prevents the falling toner from entering the charger. Therefore, it is possible to prevent problems such as uneven charging caused by the accumulation of toner on the upper surface of the charger.

According to the present invention, the toner intrusion prevention wall is formed by a film member, and is mounted on a grid member constituting a charger or a grid holding member holding the grid member. The management of the gap with the peripheral surface of the body drum becomes easy.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing an embodiment of an image forming apparatus configured according to the present invention.

FIG. 2 is a cross-sectional view of the image forming apparatus configured according to the present invention shown in FIG.

FIG. 3 is a sectional view showing another embodiment of a toner intrusion prevention wall provided in the image forming apparatus shown in FIG. 1;

[Explanation of symbols]

 2: printer 4: process unit 5: support shaft 20: body housing 21: housing body 23: cover 24: laser unit 25: fixing roller pair 26: discharge roller pair 27: discharge tray 28: paper feed tray 29: paper feed tray 29: paper feed Roller 30: Friction pad 31: Transfer roller 40: Photoconductor unit 41: Photoconductor support means 42: Photoconductor drum 43: Charger (corona discharger for charging) 44: Foreign matter collection brush 45: Guide plate pair before transfer 46: Post-transfer guide plate 47: toner intrusion prevention wall 50: developing unit 51: developing housing 52: coil spring 53: developing roller 54: supply roller 55: stirring means 56: developer regulating means 57: lid 58: sheet-shaped seal member 431 : Grid member of corona discharger for charging 411: Side wall member of photoconductor support means 412: Photoconductor support Step connecting member 422: charging area 423: electrostatic latent image forming area 424: developing area 425: transfer area 470: toner intrusion prevention wall 514: stirring chamber 515: developing chamber 517: developing housing connecting member 533: developer holding Area 534: Developer regulation area 561: Blade

Claims (6)

[Claims] 1. A photosensitive drum rotatably disposed to sequentially pass through a charging area, an electrostatic latent image forming area, a developing area, and a transfer area, and a peripheral surface of the photosensitive drum disposed in the charging area. A charger for charging to a specific polarity; a developing device disposed in the developing area for developing an electrostatic latent image formed on the peripheral surface of the photosensitive drum in the electrostatic latent image forming area into a toner image; Transfer means for transferring a toner image formed on the peripheral surface of the photosensitive drum to transfer paper, the charging area being defined below the photosensitive drum, An image forming machine provided with a foreign matter collecting brush which is in contact with the peripheral surface of the photosensitive drum between the transfer area and the transfer area, wherein a portion between the charger disposed in the charging area and the foreign matter collecting brush is provided. A toner intrusion prevention wall, whose upper end is disposed close to the peripheral surface of the photosensitive drum, To Bei, an image forming apparatus, characterized in that. 2. The image forming apparatus according to claim 1, wherein said toner intrusion prevention wall is formed of a film member, and is mounted on a grid member detachably mounted on a grid holding member constituting said charger. Machine. 3. The image forming apparatus according to claim 1, wherein said toner intrusion prevention wall is formed of a film member, and is mounted on a grid holding member for detachably mounting a grid member constituting said charger. . 4. A photoconductor drum rotatably disposed to sequentially pass through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and a charging area defined below the photoconductor drum. A charger arranged to charge the peripheral surface of the photosensitive drum to a specific polarity; and a charger disposed in the developing area and forming an electrostatic latent image formed on the peripheral surface of the photosensitive drum in an electrostatic latent image forming area. In a process unit of an image forming machine, a developing device for developing a toner image and a foreign matter collecting brush disposed between the charging area and the transfer area and in contact with a peripheral surface of the photosensitive drum are unitized. An image, comprising: a toner intrusion prevention wall disposed at an upper end close to a peripheral surface of the photosensitive drum between the charger disposed in a charging area and the foreign matter collecting brush. Forming machine process unit. 5. The image forming apparatus according to claim 4, wherein said toner intrusion prevention wall is formed of a film member, and is attached to a grid member detachably attached to a grid holding member constituting said charger. Machine. 6. The image forming apparatus according to claim 4, wherein said toner intrusion prevention wall is formed of a film member, and is mounted on a grid holding member for detachably mounting a grid member constituting said charger. .