JP2000352869A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent much depositions from sticking on a part of a developing sleeve in the peripheral direction. SOLUTION: This image forming device is let forming the toner image (visible image) as the visual image by respectively making developing sleeve 4ay, 4ac, 4am and 4bk of respective color 4y, 4c, 4m and 4bk, beginning rotation in the direction R4y, R4c, R4m and R4bk in the direction respectively shown by the arrow, in synchronism with the time when the primary electrifier 2 is let starting the electrifying operation, and making the developing device of specified color being put to serve for development of the electrostatic latent image is selectively shifted to the developing position close to the photoreceptor drum 1 surface by respective eccentric circular cam 24y, 24m, 24c and 24bk, and moreover making the toner stuck on the electrostatic latent image through the developing sleeve 4a. The rotary operation of the developing sleeve 4ay, 4ac, 4am and 4bk is respectively completed in synchronism with the electrifying operation completion of the primary electrifier 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording type image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional one-drum type full-color image forming apparatus.

The color image forming apparatus of this embodiment is of an electrophotographic type, and has a digital color image reader section at an upper portion and a digital color image printer section at a lower portion. In the following description, four full-color images are formed in the order of yellow, cyan, magenta, and black.

In the reader section, the image of the original 130 placed on the original platen glass 131 is irradiated by an exposure lamp 132, color-separated, and a yellow image is first read by a full-color sensor 134, and a predetermined process is performed. The image data is sent to the printer unit as an image signal.

[0005] The printer section has a photosensitive drum 101 as an image carrier that is driven to rotate in the direction of arrow R1. Around the photosensitive drum 101 along the rotation direction,
A primary charger (charging means) 102, an exposure means (latent image forming means) 103, a developing device 104, a transfer device 105, a cleaning device 106, a pre-exposure lamp 107, and the like are arranged.

In the printer section, the photosensitive drum 101 is rotated in the direction of arrow R1, and is uniformly charged by the primary charger 102. A laser beam is emitted from a laser output unit of the exposure unit 103 based on the image signal sent from the reader unit, and the charged surface of the photosensitive drum 101 is exposed by a light image E via a polygon mirror 103a or the like.
The exposed portion of the surface of the photosensitive drum 101 has its charge removed, thereby forming an electrostatic latent image corresponding to yellow.

In the developing device 104, a yellow developing device (developing means) 104y is arranged at a predetermined developing position. On the other hand, the other cyan, magenta, and black developing devices (developing means) 104c, 104m, and 104bk are retracted from the developing position and stopped.

The electrostatic latent image on the photosensitive drum 101 has yellow toner adhered thereto by a developing unit 104y and is visualized to form a toner image. The yellow toner image on the photosensitive drum 101 is attracted so as to be wound around the surface of the transfer drum 105a, and is transferred onto the recording material P which is rotationally supported in the direction of arrow R5.

On the other hand, the photosensitive drum 101 after the transfer of the toner image
The remaining toner on the surface is removed by a cleaning device 106, and unnecessary charges are removed by a pre-exposure lamp 107, and the resultant image is used for the next image formation starting from primary charging.

[0010] From the reading of the original image, the transfer of the toner image to the recording material on the transfer drum 105 as described above,
The process of cleaning the photosensitive drum 101 and removing electricity is performed in the same manner for other colors than yellow, that is, cyan, magenta, and black, so that the four color toner images overlap the recording material on the transfer drum 105a. Is transcribed.

The recording material to which the four color toner images have been transferred is
After being separated from the transfer drum 105a, the sheet is conveyed to the fixing device 110 and subjected to a fixing process while passing through the fixing device 110, so that a copy image is obtained.

[0012]

Generally, in an electrophotographic image forming apparatus as described above, corona discharge is performed in a latent image forming step, an image transferring step, and the like. Nitrogen oxides) are generated. These discharge products react with moisture (H ₂ O) in the air and adhere to the surface of a member constituting the image forming apparatus.

When a large amount of deposits formed from such discharge products adhere to the surface of the developer carrier of the developing device,
In some cases, the charge amount of the developer carried on the surface of the developer carrier is changed, and in the case of a two-component developer, the toner released from the carrier tends to adhere directly to the surface of the developer carrier. If a large amount of this deposit adheres to only a part of the surface of the developer carrier in the circumferential direction, a so-called pitch unevenness image may occur in which the developed image density is partially different.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of preventing a large amount of deposits on a part of a circumferential direction of a developer carrying member.

[0015]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
An image carrier on which an electrostatic latent image is formed, charging means for charging the image carrier, and a latent image forming means for forming an electrostatic latent image on the image carrier charged by the charging means; An image forming apparatus comprising: a developing container for storing a developer; and a plurality of developing means including a developer carrier rotatably provided at a position of the developing container facing the image carrier. The image forming apparatus is characterized in that all of the developer carriers rotate while a unit performs a charging operation on the image carrier.

It is preferable that the developer carrier has a developing peripheral speed during a developing operation and an idling peripheral speed rotating without performing the developing operation. The idling peripheral speed is preferably lower than the developing peripheral speed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.

First, the overall structure of the color image forming apparatus according to the present embodiment will be described with reference to FIG.

The color image forming apparatus of this embodiment has a digital color image printer unit (hereinafter simply referred to as "printer unit") I at the bottom and a digital color image reader unit (hereinafter simply referred to as "reader unit") at the top. The printer unit I forms an image on the recording material P based on the image of the document 30 read by the reader unit II, for example.

Hereinafter, the configuration of the printer unit I and the configuration of the reader unit II will be described.

The printer unit I has a photosensitive drum 1 as an image carrier that is driven to rotate in the direction of arrow R1. Around the photosensitive drum 1, a primary charger (charging means) 2, an exposure means (latent image forming means) 3, a developing device 4, a transfer device 5, a cleaning device 6, a pre-exposure lamp 7 and the like are arranged.

Below the transfer device 5, that is, the printer unit I
In the lower half portion, a paper feeding and conveying unit 9 for the recording material P is arranged, and further, a separating unit 8 is provided above the transfer device 5, and a downstream side of the separating unit 8 (in the conveying direction of the recording material P). , A fixing unit 10 and a paper discharge unit 11 are arranged.

The photosensitive drum 1 has a drum-shaped base made of aluminum and an OPC (organic optical semiconductor) photosensitive member covering the surface thereof, and is driven by an arrow R1 by driving means (not shown).
It is rotationally driven at a predetermined process speed (peripheral speed) in the direction.

The primary charger 2 includes a shield 2a having an opening at a portion facing the photosensitive drum 1, and a discharge wire 2b disposed inside the shield 2a in parallel with the bus of the photosensitive drum 1.
And a grid 2c disposed at the opening of the shield 2a to regulate the charging potential. In addition, a charging bias is applied to the primary charger 2 by a power supply (not shown), whereby the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and a predetermined potential.

Above the primary charger 2, a suction duct (not shown) for guiding outside air to the vicinity of the primary charger 2 is provided, and a blower fan (not shown) is provided at its suction port. Is provided. The air sucked from outside the machine by the blower fan is guided to a suction duct and blown onto the surface of the photosensitive drum 1 from above the primary charger 2. With this blowing system, ozone, NOx, and the like generated by the discharge in the primary charger 2 are eliminated from the primary charger 2.

Exposure means 3 includes a laser output unit (not shown) that emits a laser beam based on an image signal from reader unit II, a polygon mirror 3a that reflects the laser beam, a lens 3b, and a mirror 3c. Have. Then, the surface of the photosensitive drum 1 is irradiated with the laser light to expose the photosensitive drum 1, thereby removing an electric charge of the exposed portion to form an electrostatic latent image. In this embodiment, the electrostatic latent image formed on the surface of the photosensitive drum 1 is color-separated into four colors of yellow, cyan, magenta, and black based on the image of the original, and a toner image is formed by each color toner. Form.

The transfer device 5 includes a transfer drum (recording material carrier) 5a having a recording material P on the surface thereof, a transfer charger (transfer charging means) 5b for transferring the toner image on the photosensitive drum 1 to the recording material P, It has an adsorption charger 5c for adsorbing the recording material P to the transfer drum 5a, an adsorption roller 5d opposed to the adsorption charger 5c, an inner charger 5e, and an outer charger 5f, and is driven to rotate in the direction of arrow R5. A recording material carrying sheet 5g made of a dielectric is integrally stretched in a cylindrical shape in a peripheral opening area of the transfer drum 5a which is rotatably supported. The recording material supporting sheet 5g uses a dielectric sheet such as a polycarbonate film.

The cleaning device 6 includes a cleaning blade 6a for scraping off residual toner remaining on the surface of the photosensitive drum 1 without being transferred to the recording material P, and a cleaning container 6b for collecting the scraped toner.

The pre-exposure lamp 7 is disposed adjacent to the primary charger 2 on the upstream side in the photosensitive drum rotation direction, and removes unnecessary charges on the surface of the photosensitive drum 1 cleaned by the cleaner 6.

The paper feeding and conveying section 9 is provided with recording materials P of different sizes.
Paper feed cassette 9a for stacking and storing, a paper feed roller 9b for feeding the recording material P in the paper feed cassette 9a, a number of transport rollers 9c, a registration roller 9d, and the like. The recording material P is supplied to the transfer drum 5a.

The separating means 8 is provided for the recording material P after the transfer of the toner image.
Charger 8a for separating the toner from the transfer drum 5a,
It has a separation claw 8b and a separation push-up roller 8c.

The fixing device 10 is disposed below the fixing roller 10a and a fixing roller 10a having a heater inside.
Pressure roller 1 for pressing recording material P against fixing roller 10a
0b.

A potential sensor S1 for detecting the charged potential on the surface of the photosensitive drum 1 is provided between the primary charger 2 and the developing device 4 around the photosensitive drum 1, and between the developing device 4 and the transfer drum 5a. Is provided with a density sensor S2 for detecting the density of the toner image on the photosensitive drum 1.

Next, the reader section II will be described.

A reader unit II disposed above the printer unit I includes a document table glass 31 on which the document 30 is placed, and an exposure lamp 3 for exposing and scanning the image surface of the document 30 while moving.
2. a plurality of mirrors 35 for further reflecting light reflected from the document 30, a lens 33 for condensing the reflected light, and a lens 3
And a full-color sensor 34 for forming a color-separated image signal based on the light from the light source 3. The color-separated image signal is processed by a video processing unit (not shown) through an amplifier circuit (not shown), and is sent to the above-described printer unit I.

The image of the original 30 placed on the original platen glass 31 of the reader unit II is irradiated by an exposure lamp 32, color-separated, and the yellow image is first read by a full-color sensor 34 and subjected to predetermined processing. The image signal is sent to the printer unit I as an image signal.

In the printer section I, the photosensitive drum 1 has an arrow R
It is driven to rotate in one direction, and the surface is uniformly charged by the primary charger 2. A laser beam is emitted from a laser output unit of the exposure unit 3 based on the image signal sent from the reader unit, and the charged photosensitive drum 1 surface is exposed by a light image E via a polygon mirror 3a or the like. . The exposed portion of the surface of the photosensitive drum 1 has its charge removed,
As a result, an electrostatic latent image corresponding to yellow is formed.

In the developing device 4, the yellow developing device 4y is moved to a predetermined developing position by the action of the eccentric cam 24y, and the other developing devices 4c, 4m, 4bk are operated by the actions of the eccentric cams 24c, 24m, 24bk. It is evacuated from the developing position. The electrostatic latent image on the photosensitive drum 1 is transferred to the developing device 4y
As a result, yellow toner is adhered to the toner, and the toner is visualized to form a toner image. The yellow toner on the photosensitive drum 1 is adhered and visualized to form a toner image. The yellow toner image on the photosensitive drum 1 is transferred to the recording material P carried on the transfer drum 5a.

As for the recording material, a recording material P having a size suitable for a document image is transferred from a predetermined paper supply cassette 9a to a transfer drum 5a at a predetermined timing via a paper supply roller 9b, a conveyance roller 9c, a registration roller 9d, and the like. Supplied. The recording material P supplied in this manner is attracted so as to wind around the surface of the transfer drum 5a, rotates in the direction of arrow R5, and the yellow toner image on the photosensitive drum 1 is transferred by the transfer charger 5b. .

On the other hand, the photosensitive drum 1 after the transfer of the toner image
The residual toner on the surface is removed by the cleaning device 6, and unnecessary charges are further removed by the pre-exposure lamp 7, so that the next image formation starting from primary charging is performed.

The processes from the reading of the original image by the reader unit II, the transfer of the toner image to the recording material P on the transfer drum 5a, the cleaning of the photosensitive drum 1, and the charge removal are performed by processes other than yellow. , That is, cyan, magenta, and black, and four color toner images are transferred onto the transfer material P on the transfer drum 5a so as to overlap.

Recording material P to which four color toner images have been transferred
Is separated from the transfer drum 5a by a separation charger 8a, a separation claw 8b, and a separation pushing roller 8c, and is conveyed to the fixing device 10 in a state where an unfixed toner image is carried on the surface. The toner image on the surface of the recording material P is heated and pressed by the fixing roller 10a and the pressure roller 10b of the fixing device 10, and is fused and fixed, that is, is fixed. The recording material P after fixing is discharged onto a discharge tray 11b by a discharge roller 11a in a discharge unit 11.

Next, the operation of the developing device, which is a feature of the present invention, will be described with reference to FIG.

The developing device 4 includes four developing devices in order from the upstream side along the rotation direction of the photosensitive drum 1 (the direction of arrow R1). Developing containers 4by containing the toners (developers) of the respective colors of yellow, cyan, magenta, and black,
Developing units 4y, 4c having 4bc, 4bm, 4bbk,
4m, 4bk. Each developing unit 4y, 4c, 4
m and 4bk denote developing containers 4by such that developing sleeves 4ay, 4ac, 4am, and 4abk, which are developer carriers for attaching toner to the electrostatic latent image formed on the surface of the photosensitive drum 1, respectively, face the photosensitive drum 1. , 4bc, 4b
It is rotatably supported by openings of m and 4bbk.

The developing units 4y, 4c, 4m, 4b
The developing sleeves 4ay, 4ac, 4am, and 4abk of
In synchronization with the start of the charging operation of the primary charging device 2, the developing device of a predetermined color used for developing the electrostatic latent image starts rotating in the directions of R4y, R4c, R4m, and R4bk indicated by arrows, respectively. Eccentric cams 24y, 24m, 24c, 24bk
2 (in FIG. 2, 24y), the toner is selectively moved to a developing position close to the surface of the photosensitive drum 1, and the toner is attached to the electrostatic latent image via the developing sleeve 4ay. Visible image). The rotation operation of the developing sleeve 4a ends in synchronization with the end of the charging operation of the primary charger 2.

When an image forming operation is performed using only a single developing device, for example, an image is formed using only the black developing device 4bk, and the other developing devices 4y for three colors of magenta, cyan, and yellow are used. The developing sleeves 4ay, 4ac, 4am, and 4abk rotate similarly in the case of so-called single-color copying in which the developing operation is not performed on the developing sleeves 4c and 4m.

The developing sleeves 4ay, 4ac, 4a
Even when m and 4abk are uniformly contaminated by the discharge product and the free toner adheres, the developing sleeve 4ay, 4ac, 4am, and 4abk are constantly rotating during the charging operation, so that the developer (mainly, Carrier), the adhered toner is peeled off, and the toner is transferred to the developing sleeves 4ay, 4ac,
It does not deposit on 4am, 4abk.

As described above, in the present embodiment, the developing sleeve of the developing device is rotated in synchronization with the charging operation of the primary charging device, so that the partial development of the developing sleeve by the discharge product generated from the primary charging device is performed. Stain can be prevented and a high-quality color image can be formed.

Embodiment 2 Next, a second embodiment of the present invention will be described.

The feature of this embodiment is that the peripheral speed of the developing sleeve in the developing device other than the developing device used for the development in the first embodiment is lower than that during image formation. That is, the developing sleeve has a developing peripheral speed at the time of the developing operation and an idle rotational speed that rotates without performing the developing operation, and the idle rotational speed is lower than the developing peripheral speed.

As shown in FIG. 3, it is known that the amount of frictional charge of the developer decreases with the rotation time of the developing sleeve. This is due to the deterioration of the developer.

Therefore, the peripheral speed of the sleeve of the unused developing device, that is, the idling peripheral speed was made lower than the peripheral speed of the sleeve during the developing operation.

In this embodiment, the peripheral speed of the sleeve of the unused developing device is set to the peripheral speed of the developing device (30 mm /
sec).

As a result, the number of rotations of the developing sleeve during image formation can be reduced, and partial contamination of the developing sleeve by discharge products generated from the primary charger can be prevented. Can be maintained for a long time.

[0056]

As is apparent from the above description, according to the image forming apparatus of the present invention, all the developer carriers are rotated while the charging means performs the charging operation on the image carrier. In addition, a large amount of deposits can be prevented from being attached to a part of the developer carrier in the circumferential direction, and a high-quality color image can be formed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a color image forming apparatus according to first and second embodiments according to the present invention.

FIG. 2 is an explanatory diagram showing an operation of each developing device in the first embodiment.

FIG. 3 is a graph showing a relationship between a developing sleeve rotation time and a toner charge amount in a second embodiment.

FIG. 4 is a schematic configuration diagram illustrating an example of a conventional one-drum type full-color image forming apparatus.

[Explanation of symbols]

Reference Signs List 1 photosensitive drum (image carrier) 2 primary charger (charging means) 4y, 4c, 4m, 4bk developing device (developing means) 4ay, 4ac, 4am, 4abk developing sleeve (developer carrier) 4by, 4bc, 4bm 4bbk development container

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsuneji Masuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shigeo Kimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon F term in reference company (reference) 2H027 ED02 ED03 ED08 EE03 EF02 EF09 2H077 AD02 BA10 DA01 DB25 GA12 9A001 BB04 HH31 JJ35 KK16 KK31 KK35 KK37 KK42 LL02

Claims (3)

[Claims] An image carrier on which an electrostatic latent image is formed; charging means for charging the image carrier; and an image carrier for forming an electrostatic latent image on the image carrier charged by the charging means. An image comprising: a latent image forming unit; a developing container for storing a developer; and a plurality of developing units including a developer carrier rotatably provided at a position of the developing container facing the image carrier. In the forming apparatus, while the charging unit performs a charging operation on the image carrier,
An image forming apparatus, wherein all the developer carriers rotate. 2. The image forming apparatus according to claim 1, wherein the developer carrier has a developing peripheral speed during a developing operation and an idle rotational speed that rotates without performing the developing operation. 3. The image forming apparatus according to claim 2, wherein the idling peripheral speed is lower than the developing peripheral speed.