JPH07248660A - Color electrophotographic device and developing mechanism thereof - Google Patents

Abstract

PURPOSE:To prevent the drop and scattering of a developer from the developing roll of a developing device. CONSTITUTION:A separate member 29 constituted of a support member 29a, an elastic member 29b, and a seal member 29c is integrally assembled between the bottom face of a developing device 8 and a belt cartridge 28 behind a rotary roll 3 rotating a photosensitive belt 2 and the developing roll 25a of the developing device 8 in no contact with the photosensitive belt 2 to secure a position nearly on the same plane. The drop and scattering of a developer 26k from the developing roll 25a can be prevented by the noncontact separate member 29, and such troubles as the damage of the photosensitive belt 2, the locking of a rotary shaft, and defective development can be excluded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus such as a printer and a copying machine using electrophotographic technology and a developing mechanism therefor, and in particular, a developing apparatus equipped with a developer carrier / toner drop / scattering prevention means. It is related to the mechanism.

[0002]

2. Description of the Related Art In an electrophotographic two-component developing system, a mixture of a magnetic carrier, each of which is a fine particle, and an insulating toner in a predetermined ratio is used as a developer. In a developing device, the developer is attracted to a magnetic developing roller rotating at a high speed and conveyed to a predetermined developing position, and a magnetic brush is formed to rub the electrostatic latent image surface to develop. . That is, the electrostatic latent image is visualized by the toner that is electrostatically attracted to the surface of the magnetic carrier. The toner consumed by this development is successively replenished from the toner cartridge.

In such a developing device, the carrier and the toner rub against each other to charge the toner,
Repeated adhesion of toner to the carrier surface causes toner particles to stick to the carrier surface (spent), the carrier surface characteristics change due to peeling of the coating agent that coats the carrier surface, or The carrier is crushed due to the stirring operation of the developer, and the life of the developer is exhausted due to deterioration of the charging characteristics of the toner. The life of the developer is affected by the physical properties of the toner and carrier, the amount of the developer, the structure of the apparatus, etc., but generally corresponds to printing or copying of tens of thousands of pages.

Now, a color electrophotographic apparatus will be described with reference to FIG. 5 and a sectional view of a developing apparatus with reference to FIG. FIG. 5 is a vertical cross-sectional side view of the color laser printer.
A belt cartridge 28, which is stretched around 5 and rotatably held, incorporates a charger 6 and a belt cleaner 16 which will be described later, and is detachably configured is arranged. The rotating roll 3 for driving the belt is about 70 mm in length for the photosensitive belt 2.
Rotate to convey at a speed of / s. Rotating roll 3,
4 is arranged so as to form a flat development area on the photosensitive belt 2. The rotating rolls 4 and 4a are arranged so as to form a toner image transfer area described later. Further, the rotating roll 5 guides the photosensitive belt 2 so as to form a stable exposure surface for scanning exposure, which will be described later, on the photosensitive belt 2.

Above the photosensitive belt 2, the photosensitive belt 2
Of the developing device 8 to
1 is detachably arranged, and the electrostatic latent image is developed by rubbing the surface of the photosensitive belt 2 with a developer magnetic brush formed in each of the developing devices 8 to 11. The developing device 8 uses a developer mixed with a carrier and a yellow (Y) color toner, the developing device 9 uses a developer mixed with a carrier and a magenta (M) color toner, and the developing device 10 uses a developer. Is a developer in which a carrier and a cyan (C) toner are mixed, and the developing device 11 is a developer in which a carrier and a black (K) toner are mixed. Then, these developing devices 8 to
By selectively acting 11 on the photosensitive belt 2 according to the corresponding color of the electrostatic latent image, each electrostatic latent image is developed into a toner image of the corresponding color. In order to develop each electrostatic latent image, one developing device is selected from the developing devices 8 to 11 and the time to act on the photosensitive belt 2 is about 5 seconds.

The developing device 8 for yellow (Y) is arranged such that the axial centers of the vertical cross sections of the developing roll 25a and the rotary roll 3 that conveys the photosensitive belt 2 are substantially aligned with each other. Therefore, as shown in the detailed explanatory diagram of FIG.
The developer 26k conveyed in is about 1m from the photosensitive belt 2.
Although it is necessary to pass the developing gap of about m by the magnetic force of the developing roll 25a, the developing gap is small, so that the resistance is large and the developer 26k that cannot pass through the developing roll 25a and the rotating roll 3 part.
Will accumulate. The same applies to the developing devices 9, 10, and 11 for magenta (M), cyan (C), and black (K), but the developing device 8 for yellow (Y) at the rearmost end faces the rotating roll 3. Therefore, the developer 26k in the pool portion formed in the curved portion of the rotating roll 3 is
The carrier that cannot be adsorbed by the magnetic force of 5a is detached and drops onto the belt cartridge 28. Similarly, developing roll 2
Since 5a rotates at a high speed, the carrier crushed during stirring is less likely to be adsorbed by the developing roll 25a, and loses to the centrifugal force to be scattered. The detachment of the developer 26k from the developing roll 25a reduces the amount of the developer 26k in the developing device 8, and the detached carrier damages the photosensitive belt 2 or the like, or the bearings are arranged in various places of the printer body 1. It may invade (not shown) and cause a serious obstacle such as locking a rotating shaft (not shown). Further, the reduction of the developer 26k in the developing device 8 makes it impossible to convey the developer 26k necessary for forming a magnetic brush for development, which causes a serious defect that required development cannot be performed. There is a problem to do. Further, there is a problem that the scattered toner adheres to the belt cartridge 28 and stains the inside of the machine.

[0007] Conventionally, as a technical example relating to the prevention of toner scattering, there is Japanese Utility Model Laid-Open No. 1-149653. This is a developing unit located closest to the exposing unit among a plurality of developing units is provided with a toner scattering prevention member that is in close contact with the photoconductor to prevent the toner from scattering to the exposing unit. Since the scattering prevention member is always in close contact with the photoconductor, it is unavoidable that the photoconductor is destroyed or worn. As a conventional improvement of the toner scattering prevention seal material,
Although there are JP-A Nos. 8-159542 and the like, all of them are used by bringing them into contact with an electrostatic latent image bearing member, and therefore conventional defects cannot be eliminated only by improving the material. According to the developing device described in Japanese Utility Model Laid-Open No. 1-149653, in which a plurality of developing portions, an exposing portion, and a charging portion are formed on the same flat portion of the photosensitive belt, the above-described drawings are used. Unlike the developing device 8 of No. 6, the curving portion of the rotating roll 3 does not have a pool of the developer 26k, but by forming the developing area, the exposure area, and the charging area in a straight line as a whole, However, there is a drawback that the color electrophotographic apparatus itself becomes large.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a structure in which a developer pool generated on the rear side of a developing roll of a developing device is applied to a curved portion of a rotating roll and the developer is easily separated from the developing roll. Another object of the present invention is to prevent the developer from coming off, eliminate the above-mentioned problems, and perform stable development, and thereby to make the color electrophotographic apparatus compact.

[0009]

SUMMARY OF THE INVENTION The above object is to provide a structure in which a rotary roll for transporting a photosensitive belt is arranged immediately below a developing roll of a developing device at the rearmost end, and a facing portion between the developing roll and the rotating roll. A separate member is provided further rearwardly at a position substantially in contact with the surface of the photosensitive belt without contacting the photosensitive belt and at the bottom of the belt cartridge or the developing device to prevent the pool of the developer from falling down. Is achieved by being composed of a supporting member, an elastic member and a sealing member.

Further, the object is to arrange the rotating roll of the belt cartridge rearward until the flat portion of the photosensitive belt is located immediately below the developing roll of the developing device at the rearmost end, and the belt cleaner of the belt cartridge and the charger. And the laser beam scanning exposure unit is disposed below the rotating photosensitive belt.

[0011]

As described above, the developing mechanism portion of the present invention is provided with another member for forming a non-contact flat portion on the photosensitive belt, so that no developer pool is formed behind the developing roll and the photosensitive belt Since the developer pool is not formed even along the curved portion of the rotating roll, the magnetic force of the developing roll easily acts on the carrier of the developer to which the developer is supplied, so that the developer is less likely to be scattered. Then, the rotary roll for conveying the photosensitive belt is arranged immediately below the developing roll of the developing device at the rearmost end or slightly rearward to form the flat portion of the developing area at the shortest, and the belt cleaner, the charger and the laser beam are formed. Since the scanning exposure unit and the like are provided below the rotating photosensitive belt, the color electrophotographic apparatus as a whole can be made compact and compact.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a vertical sectional side view of the color laser printer, in which the photosensitive belt 2 is provided at the center of the printer body 1.
Is stretched around the rotating rolls 3, 4, 4a, 5 and rotatably held, and further includes a charger 6 and a belt cleaner 16 which will be described later.
, And a belt cartridge 28 configured to be detachable is arranged. Rotating roll 3 for driving the belt
Rotates to convey the photosensitive belt 2 at a speed of about 70 mm / s. The rotating rolls 3 and 4 are arranged so as to form a flat developing area on the photosensitive belt 2.
4a is arranged so as to form a toner image transfer area, which will be described later, in the vertical portion where the photosensitive belt 2 is turned. Further, the rotating roll 5 guides the photosensitive belt 2 so as to form a stable exposure surface for scanning exposure, which will be described later, on the photosensitive belt 2.

Below the photosensitive belt 2, a corona discharge type charger 6, a laser beam scanning exposure unit 7 and a belt cleaner 16 are arranged. A laser beam 7a generated from the laser beam scanning exposure unit 7 under the control of a video signal given from a higher-order image signal generator.
Is repeatedly deflected at a period of 1.225 ms in a direction traversing the surface of the photosensitive belt 2 rotating along the rotating roll 5 to scan and expose the surface of the photosensitive belt 2, thereby rotating the photosensitive belt 2. An electrostatic latent image having a pixel density of about 300 dpi is formed in the direction.

Above the photosensitive belt 2, the photosensitive belt 2 is provided.
Of the developing device 8 to
1 is detachably arranged, and the electrostatic latent image is developed by rubbing the surface of the photosensitive belt 2 with a developer magnetic brush formed in each of the developing devices 8 to 11. The developing device 8 uses a developer mixed with a carrier and a yellow (Y) color toner, the developing device 9 uses a developer mixed with a carrier and a magenta (M) color toner, and the developing device 10 uses a developer. Is a developer in which a carrier and a cyan (C) toner are mixed, and the developing device 11 is a developer in which a carrier and a black (K) toner are mixed. Then, these developing devices 8 to
11 is developed into a toner image of the corresponding color of the electrostatic latent image. Any one of the developing devices 8 to 11 arranged along the rotation direction of the photosensitive belt 2 for developing each electrostatic latent image.
Development is performed while selecting one developing device, but the time for which the one developing device acts on the photosensitive belt 2 is about 5
Seconds.

The intermediate transfer drum 12 is arranged so as to rotate while contacting the photosensitive belt 2 positioned in the printer body 1 in the toner image transfer area, and the toner image formed on the surface of the photosensitive belt 2 is formed by this toner. The image is transferred to the intermediate transfer drum 12 in the image transfer area. At this time, the intermediate transfer drum 12 also rotates at a speed of about 70 mm / s like the photosensitive belt 2. This is a speed equal to the rotation speed of the photosensitive belt 2, and the photosensitive belt 2 and the intermediate transfer drum 12 rotate in synchronization. Around the intermediate transfer drum 12, a pre-charging device 13, a transfer roll 14, and a drum cleaner 15 are arranged so as to face the outer peripheral surface of the intermediate transfer drum 12. The toner image of each color is transferred from the photosensitive belt 2 to the outer peripheral surface of the intermediate transfer drum 12. Are sequentially transferred to form a color toner image.

The precharger 13 is a corona discharger,
A corona discharge is generated by being urged to provide a charge for supporting the transfer of the completed color toner image onto the recording paper 17 on the surface of the intermediate transfer drum 12. Drum cleaner 15
Is movable toward and away from the surface of the intermediate transfer drum 12, and from the outer peripheral surface in the process of forming a color toner image by transferring a plurality of single-color toner images from the photosensitive belt 2 onto the intermediate transfer drum 12 in an overlapping manner. After the color toner image is transferred to the recording paper 17 and the completed color toner image is transferred to the outer peripheral surface, the surface of the intermediate transfer drum 12 is contacted to remove the residual toner.

The paper feed mechanism is installed in the space below the scanning exposure unit 7, and the recording paper 1 stored in the paper feed cassette 18 is provided.
7 is extracted by a paper feed roll 19 and sent out.

A registration roll 20 is provided between the paper feed roll 19 and the transfer roll 14 so as to match the transport timing of the color toner image formed on the surface of the intermediate transfer drum 12 with the recording paper 17 onto which the toner image is transferred. The recording paper 17 fed from the paper feed roll 19 is fed to the transfer roll 14 with the conveyance timing adjusted. The registration roll 20 holds the recording paper 17 at about 70 mm / s (photosensitive belt 2
And the intermediate transfer drum 12 is rotated at the same speed).

A transport guide 21 is provided downstream of the transfer roll 14.
The fixing device 22 and the paper discharge roll 23 are provided, and the discharge tray 24 on which the printed matter (recording paper 17 having the toner image fixed) sent from the paper discharge roll 23 is placed is the printer body 1.
Is formed on the upper surface of. The printer main body 1 has a control circuit device for controlling the operation of the color laser printer, which is not shown.

Next, the details of the developing devices 8 to 11 will be described. Since the four developing devices 8 to 11 have basically the same configuration, the developing device 8 will be described as an example. Figure 1
The positional relationship of another member 29 integrated with the developing device 8 and the belt cartridge 28 for preventing the carrier / toner of the developer from dropping / scattering is shown.

The developing device 8 applies the developer to the photosensitive belt 2
Developing unit 2 fixed for developing by acting on
5, the developer mixed and charged by stirring is supplied to the developing unit 25, and the developer which has completed the developing action is collected from the developing unit 25 and is detachable from the developing unit 25. And a toner cartridge 27 detachably engaged with the developing cartridge 26 so as to replenish the developing cartridge 26 with toner.

The developing frame 25e, which is the basis of the developing unit 25, is a non-replaceable component fixedly fixed to the frame of the printer body 1 and is magnetized so as to face the photosensitive belt 2 with a predetermined developing gap. Developing roller 25a and transport roller 25b, a developer receiving port 25f for receiving the developer 26k supplied from the developing cartridge 26 and giving it to the developing roller 25a, and a developer magnetically held on the surface of the developing roller 25a. 26k and a non-magnetic material that removes the developer 26k transferred from the developing roll 25a to the transport roll 25b from the transport roll 25b, and the spike cutting blade 25c that is formed of a non-magnetic material that defines the height of the magnetic brush. The peeling blade 25d formed by the above and the developer discharge port 25g for discharging the peeled developer 26k. To.

The developing cartridge 26 is a developing unit 25.
In the new state, a new developer 26k is stored in a developer storage container 26p. The developing cartridge 26 includes a stirring screw 26b that stirs the developer 26k to make the mixed state of the carrier and the toner uniform and frictionally charges the toner, and a developer supply port 26c from which the developer 26k is stirred while stirring the developer 26k. An agitating and supplying roll 26a that supplies the developer receiving port 25f of the developing unit 25, an engaging lever 26j that engages and fixes at a predetermined position of the developing unit 25, and a developer that is peeled off from the conveying roll 25b by a peeling blade 25d. A guide base 26i that receives the developer 26k discharged from the discharge port 25g from the developer recovery port 26s and guides it to the toner concentration detection container 26n, and a toner concentration detection container 26n.
The toner concentration detecting element 26f installed inside the support shaft 2
A developer shutter 26d supported by 6q and biased by a spring so as to rotate counterclockwise to close the developer supply port 26c, and a support shaft 26r as a center in response to attachment / detachment of the toner cartridge 27. A shutter lever 26e which is rotated to operate to open and close the developer shutter 26d.
With. The toner cartridge 27 is a replacement part that is detachably engaged with the developing cartridge 26. The developer 26k in the developing cartridge 26 is a mixture of magnetic carrier and insulating toner, and is supplied from the developer supply port 26c to the developer receiving port 25f of the developing unit 25 by the stirring and supplying roll 26a. The developing roll 25a is driven before the stirring and supplying roll 26a is rotated, and the developer 26k held on the surface thereof by the magnetic force of the developing roll 25a is exposed to the developing roll 25a and the photosensitive roll 25a by the spike cutting blade 25c. The electrostatic latent image formed on the surface of the photosensitive belt 2 is rubbed against the photosensitive belt 2 while being conveyed in the direction of the arrow while being cut into a predetermined thickness corresponding to the distance between the belts 2 (about 1 mm). To develop.

The developer 26k which has passed through the developing area is transferred from the developing roll 25a to the carrying roll 25b and carried to the upper part of the developing unit 25, peeled from the carrying roll by the peeling blade 25d and pushed out from the developer discharge port 25g. From the developer recovery port 26s to the guide base 26i
And is collected in the developing cartridge 26.

The separate member 29 fixed to the belt cartridge 28, as shown in an enlarged view in FIG.
9a, elastic member 29b protruding at the tip, seal member 29
c is integrally formed, and the bottom surface is the rotating roll 3
It is arranged so that it can hold almost the same surface as the photosensitive belt 2 wound around. Further, the tip end portion is arranged in a non-contact manner with a gap of about 2 to 3 mm with the photosensitive belt 2 so that even if another member 29 is vertically deformed, it is not strongly pressed against the photosensitive belt 2. There is. Separate member 29
The elastic member 29b protruding to the end portion on the side of the photosensitive belt 2 is for preventing damage when it contacts the photosensitive belt 2, and is made of a soft material such as a polyester film or a urethane rubber sheet. In addition, the support member 29a
Is made of a material such as a polyester sheet having a thickness of about 0.2 to 0.3 mm in order to prevent the elastic member 29b from being deformed in the longitudinal direction. The seal member 29c is the support member 29.
It is a foam material having a rectangular cross section and is arranged so as to eliminate a gap between the belt cartridge 28 and the bottom surface of the developing device 8 and has a length of 2 to 2 mm from the tip of the elastic member 29b.
It is retracted about 4 mm.

The operation of the separate member 29 is as follows.
Developing device 8 arranged at the end of the plurality of developing devices
Of the developing roll 25a and the rotating roll 3 which conveys the photosensitive belt 2 are substantially aligned with each other in the axial center of the vertical section (ideally, the axial centers are vertically aligned in this manner). It is arranged so that the rotating roll 3 comes just below. Therefore, the developer 26k conveyed by the developing roll 25a passes through the developing gap of about 1 mm formed by the developing roll 25a and the photosensitive belt 2, so that the developer 26k is accumulated behind the developing roll 25a. However, when the separate member 29 is installed, the pool of the developer 26k is held in the space formed by the elastic member 29b of the separate member 29 and the seal member 29c. Therefore, the developer 26k does not exist in the curved portion of the photosensitive belt 2 caused by the rotating roll 3, and the magnetic force of the developing roll 25a easily acts on the developer 26k. Furthermore, the elastic member 29 of the separate member 29
b and the seal member 29c, the developing roll 25a
The crushing carrier and the toner scattering due to the high speed rotation are also prevented. Therefore, by installing the separate member 29, the developing roll 2
The rotary roll 3 can be arranged immediately below 5a, the developing area of a color printer having a plurality of developing devices 8 to 11 can be shortened, and the entire device can be made compact and compact.

FIG. 4 shows another embodiment of the present invention in which the rotating roll 3 is arranged slightly behind the developing roll 25a, and the developing roll 25a of the developing device 8 at the rearmost end also faces the flat portion of the photosensitive belt 2. It was done like this. As a result, the bent portion of the photosensitive belt 2 under the developing roll 25a does not exist and the flat portion of the photosensitive belt 2 has a pool of the developer 26k, so that the dropping / scattering of carrier toner can be prevented. In this case, the flat portion of the developing area becomes longer than that in the above-described embodiment of FIG. 2, but the exposure area, the charging area, etc. are arranged below the rotating photosensitive belt 2, and Since only the developing area is installed on the upper side, the device can be made compact and compact.

[0028]

As described above, according to the present invention, it is possible to prevent the developer (carrier and toner) of the developing device from being scattered to the belt cartridge or the like, so that the development amount is reduced due to the reduction of the developer amount in the developing device. Can be eliminated. Further, since the scattered developer is prevented from entering the bearings and the like arranged everywhere in the printer body, and the photosensitive belt and the like can be prevented from being damaged or contaminated, a printer having high reliability and excellent image quality can be provided. Further, there is an effect that a small and compact printer can be provided.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a main part of a developing device according to an embodiment of the present invention.

FIG. 2 is a vertical sectional side view of a printer body according to an embodiment of the present invention.

FIG. 3 is an enlarged cross-sectional view of another member of the embodiment of the present invention.

FIG. 4 is a vertical sectional side view of a printer body according to another embodiment of the present invention.

FIG. 5 is an explanatory diagram of a conventional printer.

FIG. 6 is an explanatory diagram of a conventional developing device.

[Explanation of symbols]

1 ... Printer body, 2 ... Photosensitive belt, 3 ... Rotating roll,
6 ... Charger, 7a ... Laser beam, 8 ... Developing device, 16
... belt cleaner, 25a ... developing roll, 26k ... developer, 27 ... toner cartridge, 28 ... belt cartridge, 29 ... separate member 29a ... supporting member, 29b ... elastic member, 29c ... sealing member.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tetsuro Akasaki 1-1-1, Higashitaga-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Information & Video Media Division

Claims (4)

[Claims] 1. A developer stirred in a developer accommodating space is held on the surface of a developing roll to act on the electrostatic latent image surface, and the developer finished working on the electrostatic latent image surface is treated on the developing roll. A developing device, which is separated from the surface and collected in the developer accommodating space and is replenished with toner from the toner cartridge to the developer that has consumed toner, a rotating roll, and an electrostatic latent image surface that is rotated by the rotating roll. In a developing mechanism of a color electrophotographic apparatus including a photosensitive belt that forms a sheet, a belt cleaner that is disposed opposite to the photosensitive belt, and a belt cartridge that is detachably provided in the printer body by incorporating a charger and the like, The rotating roll of the belt cartridge is arranged just below the developing roll of the apparatus, and the photosensitive belt is provided in the rear of the developing roll and the rotating roll without contacting the photosensitive belt. A developing mechanism for a color electrophotographic apparatus, characterized in that a separate member for preventing the fall of the developer pool, which is integrally incorporated in the belt cartridge or the bottom surface of the developing device, is provided at a position substantially coincident with the surface. . 2. A support member, an elastic member, and a seal member, wherein the elastic member is projected at the tip side of the support member, and the seal member is provided on the support member in an overlapping manner.
2. The developing mechanism for a color electrophotographic apparatus according to claim 1, wherein another member adapted to hold a pool of the developer is provided in a space formed by the elastic member and the seal member. 3. A developer stirred in a developer accommodating space is held on the surface of a developing roll to act on the electrostatic latent image surface, and the developer which has finished acting on the electrostatic latent image surface is treated on the developing roll. A plurality of developing devices that are separated from the surface and are collected in the developer accommodating space and are replenished with toner from the toner cartridge, and a rotating roll and an electrostatic device that is rotated by the rotating roll. In a developing mechanism of a color electrophotographic apparatus, which includes a photosensitive belt that forms a latent image surface, and a belt cartridge that is detachably provided in a printer main body by incorporating a belt cleaner, a charger and the like that are arranged to face the photosensitive belt, The rotating roll of the belt cartridge is arranged rearward immediately below the developing roll of the rearmost developing device until the flat portion of the photosensitive belt is positioned, and the belt cartridge is installed. A developing mechanism for a color electrophotographic apparatus, in which the belt cleaner, the charger, and the laser beam scanning exposure unit are disposed below the rotating photosensitive belt. 4. A toner image transfer area is formed at a positioning portion of a photosensitive belt which is provided with the developing mechanism according to claim 1 and passes through a flatly rotating developing area to change direction. A color electrophotographic apparatus, wherein a toner image is transferred in the image transfer area.