JPH0375668A - Developing device - Google Patents

Abstract

PURPOSE:To lower a space around an image carrier and to easily replenish a developer by providing a developer carrier facing the image carrier and plural developer delivery means facing the developer carrier. CONSTITUTION:A developing device is provided with developer carrier 20 being provided while facing to the image carrier 2, holding a developer layer on its surface and developing an electrostatic latent image formed on the image carrier 2, and plural developer delivery means 21a-21d being provided while facing to the developer carrier 20, selectively giving a prescribed color developer T on the developer carrier 20, and recovering the developer T on the developer carrier 20 after the electrostatic latent image is developed at the same time. Consequently, only one developer carrier 20 is arranged with respect to the image carrier 2. Thus, the space factor around the image carrier 2 can be lowered. Plural developer delivery means 21a-27d facing the developer carrier 20 are fixedly provided, so that the developer T is easily replenished without generating the noise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a developing device applied to an image forming apparatus such as an electrophotographic color printer.

(Prior Art) In recent years, developing devices such as electrophotographic full-color printers have conventionally used three colors such as yellow, magenta, and cyan around a photoreceptor drum a as an image carrier, as shown in FIG.
Developing device containing 4 colors of developer including color or black 2
．． , b2. It had a configuration in which b3 (three in this example) were arranged.

However, such a structure requires a space for arranging three or four developing rollers C around the photoreceptor drum a, and therefore requires a large photoreceptor drum a.

As a result, there is a problem in that the entire device becomes large.

On the other hand, in recent years, as shown in FIG.
d2. Rotating frame f that rotates d3+d4 around axis e
Attach it to the developer d of the required color.

A device has appeared that brings only da, d3, d4 to a position facing the photosensitive drum g.

According to this configuration, since the photosensitive drum g can be made smaller, there is a greater degree of freedom in the arrangement of the entire apparatus, and there is an advantage that the entire apparatus can be made smaller.

Furthermore, since the developing position is constant, it is easy to ensure the effect of dark decay of the photosensitive drum g. However, this structure
lr d2. Since d3p and d4 rotate, it is not only difficult to replenish toner, but also causes noise.

(Problem to be Solved by the Invention) As described above, in the past, a plurality of developing devices were arranged around an image bearing member such as a photoreceptor drum, so the diameter of the image bearing member had to be increased. Further, since the developing device facing the image carrier is changed by mechanical switching, there are problems such as an increase in the size of the device and a complicated mechanism.

The present invention has been made to solve the above problems, and its purpose is to provide a developing device that has a small space factor around an image carrier, allows easy toner replenishment, and is noiseless. be.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a developing device capable of multicolor development of an electrostatic latent image formed on an image bearing member. a developer holder, which is provided opposite to the developer holder and which holds a developer layer on its surface to develop the electrostatic latent image formed on the image carrier; The present invention is configured to include a plurality of developer transfer means for selectively applying a developer of a predetermined color onto the holder and recovering the developer on the developer holder after the electrostatic latent image is developed. It is something.

(Function) That is, since the present invention has the above structure, it is sufficient to arrange one developer holder for the image carrier, and it is possible to reduce the space factor around the image carrier. Further, it is sufficient to provide a plurality of developer transfer means fixedly facing the developer holder, and replenishment of the developer becomes easy, and there is no noise caused by rotating a plurality of developing devices. Furthermore, since the developer on the developer holder is collected into the developer transfer means containing the developer of the same color after the electrostatic latent image is developed, there is no need for a special mechanism. By simply changing the bias relationship of the delivery/reception means, etc., it becomes possible to distinguish between supply, collection, and non-use, making control easier.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 2 shows the configuration of a full-color laser printer employing the developing device of the present invention, and 1 in the figure is the main body of the device. At the upper center of the apparatus main body 1 is a photoreceptor drum 2 whose surface is coated with an organic photoreceptor as an image carrier.
A charging device 3, a multicolor developing device 4 (described later), a transfer drum 5, a cleaning device 6, and a static eliminator are arranged around the photosensitive drum 2 in the direction of rotation (direction of arrow A). Devices 7 are arranged one after the other. moreover,
A laser exposure device 8 for exposing image information is provided in the upper part of the main body 1 between the charging device 3 and the multicolor developing device 4.

Further, a paper feed cassette lO containing paper P such as plain paper is installed on one side of the main body 1, and the paper feed means 1
1, the sheets are fed one by one.

Paper P fed from the paper feed cassette 10 is conveyed along a U-turn conveyance path 12, and guided to a paper discharge tray 13 mounted above the paper feed cassette 10. The transfer drum 5, the peeling means 14, and the fixing device 15 are opposed to the U-turn conveyance path 12.

During image formation, the photoreceptor drum 2 rotates in the direction of the arrow, and the surface of the photoreceptor drum 2 is uniformly negatively charged by the charging device 3.

Thereafter, the image information is exposed by the laser exposure device 8, and the charge on the surface of the photoreceptor drum 2 is selectively removed to form an electrostatic latent image.

This electrostatic latent image is then developed with a first color non-magnetic component developer (toner) T in a multicolor developing device 4.

On the other hand, at this time, the paper P fed from the paper feed cassette 10 is wound around the transfer drum 5 with its leading edge held by the gripper 5aI. Then, the transfer drum 5 is moved as indicated by arrow B in a state where a positive bias is applied.
When the photosensitive drum 2 rotates in the direction and reaches the transfer position C, the photosensitive drum 2
The upper toner image is transferred to paper P.

Note that the toner T that has not been completely transferred is cleaned by the cleaning device 6, and the memory of the photosensitive drum 2 is removed by the static eliminator 7, and the next cycle begins.

Here, when transferring a plurality of colors, the transfer drum 5 is rotated once again, and during this period, the developing device 4 is switched to the second color.

After the transfer has been performed a predetermined number of times in this manner, the peeling means 14 operates to peel the paper P from the transfer drum 5 and enters the paper ejection process. Then, the fixing device 15 fixes the paper P.
The upper toner image is heated and fixed, and the paper is discharged onto the paper discharge tray 13.

Next, the configuration of the multicolor developing device 4 will be explained.

As shown in FIG. 2, the multicolor developing device 4 is arranged to the left of the photosensitive drum 2. As shown in FIG. And photosensitive drum 2
A developing drum 20 as a developer holding body is provided to face the developer drum 20 with a minute gap G1 of 0.25 mm between them. The developing drum 20 holds a developer layer (toner layer) T' on its surface and rotates in the direction of the arrow in the with mode with respect to the rotational direction (direction of the arrow) of the photoreceptor drum 2. Also, facing the developing drum 20 is yellow toner T.
4-color developer unit 4 containing v1 magenta toner TkAs cyan toner TCs and black toner TB
a, 4b, 4c, and 4d are arranged side by side.

These developing unit units 4a, 4b, 4c, and 4d have developing rollers 21a, 21b, and 21c as developer transfer means for the developing drum 20, respectively.

21d with the photoreceptor drum 2, with a gap G2 of 0, 25 mm.
They are in a state where they are facing each other. Then, as will be described later, toners T1 of predetermined colors, that is, yellow toner TV, magenta toner TM, and cyan toner T are deposited on the developing drum 20. and black toner TB are selectively applied, and the toner T on the developing drum 20 is collected after the electrostatic latent image is developed.

These developing rollers 21a, 21b, 21c.

21d is a stainless steel sleeve whose surface is sandblasted with #600.

Next, regarding the configuration of the developing unit 4a.

This will be explained with reference to FIG. Note that the other developer units 4b, 4c, and 4d are also approximately the same as the developer unit 4a.
Since the configuration is the same, the same reference numerals are given and the explanation will be omitted.

In the figure, reference numeral 25 denotes a casing, and the developing roller 21a is disposed at the front end opening of the casing 25. Inside the casing 25, there is an elastic foam such as Moltoprene as a toner conveying roller. A roller 26 and a foamed urethane roller 27 as a scraping roller are arranged. Further, a stainless steel blade 28 with a thickness of about 0.15 as a layer forming member and two urethane blades with a thickness of about 0.3 as a collection blade are in pressure contact with the developing roller 21a.

Therefore, the non-magnetic component toner T in the casing 25,
is carried by the toner conveying roller 26 to the developing roller 21a side, and is sent between the developing roller 21a and a stainless steel blade 28 that is pressed against the developing roller 21a with a contact pressure of too g/cm 2 . Here, the toner T is triboelectrically charged and at the same time thinned to a thickness of about 30 μ-. As the developing roller 21a rotates in the direction of arrow E, a toner transfer position is set in the gap G2 between the developing roller 21a and the developing drum 20. Transported to 30.

At this toner transfer position 30, the toner T is transferred to the developing drum 20 side according to the principle of jumping development according to the bias relationship between the developing roller 21a and the developing drum 20.

Note that the developing roller 21 does not move to the developing drum 20 side.
The toner TY remaining on a is collected into the casing 25 by the urethane blade 29 and then scraped off by the foamed urethane roller 27.

Note that the foamed urethane roller 27 as a scraping roller prevents the same toner TY from always adhering around the developing roller 21a and causing an excessive amount of toner charge, but it is not necessarily indispensable. Therefore, the developer unit 4b for magenta toner 7M and the developer unit 4d for black toner TB are omitted.

Next, the developing operation will be explained.

First, the surface of the photoreceptor drum 2 is uniformly negatively charged to -400V by the charging device 3. It is assumed that after this, the image information is exposed by the laser exposure device 8, and the surface potential of the portion of the photosensitive drum 2 to be developed is removed to oV.

AC biased to DC-250V for developing drum 20
By applying a bias voltage of l, 2KV, if
If there is negatively charged toner T on the developing drum 20, this toner T flies toward the exposed portion of the opposing photoreceptor drum 2 whose surface potential is ov, with a minute gap G1, that is, toward the electrostatic latent image. Then, the electrostatic latent image will be developed.

On the other hand, the developer unit I containing the yellow toner TY
・By applying a bias voltage of -400 V to the developing roller 21a of 4a, the toner TY on the developing roller 21a is
moves onto the developing drum 20 according to the principle of jumping development, so that the electrostatic latent image on the photosensitive drum 2 is developed yellow.

At this time, the developer units 4b and 4c are not in use.

The developing rollers 21b, 21c, and 21d of 4d are applied with the same potential as the developing drum 20, that is, ACl biased at DC-250V, and a bias voltage of 2KV is applied. As a result, the developing drum 20 and the developing rollers 21b, 21c, 21 of the unused developing unit 4b, 4c, 4d
The toner T is not transferred to and from d.

Also, at this time, the developing unit 4b is not in use.

It is desirable to stop the rotation of the developing rollers 21b, 21c, and 21d of 4c and 4d.

In this manner, when the development cycle of the yellow toner TY is completed, a collection cycle of the yellow toner TY on the developing drum 20 begins.

In this recovery cycle, the photosensitive drum 2 is biased to -400V, and the developing drum 2o and the developing rollers 21b, 21c, 21d of the unused developing unit 4b, 4c, 4d are
The developing roller 21a of the developer unit 4a is biased to OV. As a result, the yellow toner T on the developing drum 2o is transferred to the developing roller 21.
It flies to side a and is collected by the developing device unit 4a of the same color.

At this time, the developer units 4b and 4c are not in use.

Between the developing rollers 21b, 21c, and 21d of 4d,
As before, no jumping phenomenon occurs.

Further, a jumping phenomenon occurs between the photoreceptor drum 2 and the developing drum 2o, but since the photoreceptor drum 2 is negatively biased, the toner TY returns to the developing drum 2 as a result.

Furthermore, development using magenta toner TM1, cyan toner T0, and black toner TB is performed in the same manner as described above by changing the respective bias relationships.

Note that 35 shown in FIG. 2 is a cleaning device provided to further enhance the cleaning effect of the developing roller 20, and is used to collect toner from the developing drum 20 to the developing roller 21 (
cleaning blade 35a after the completion of the cleaning cycle)
The residual toner T is removed by bringing the two parts into contact with each other.

Further, in the present invention, it is sufficient to arrange one developing drum 20, which is a developer holding body, for the photoconductor drum 2, which is an image carrier, and the space factor around the photoconductor drum 2 can be reduced. I can do it. In addition, the developing drum 20
It is only necessary to provide a plurality of developer delivery/reception means in a fixed manner in opposition to the toner T, which makes it easy to replenish the toner T as the developer, and eliminates the noise of rotating a plurality of developing devices as in the prior art. Further, after developing the electrostatic latent image, the toner T on the developing drum 20 is transferred to the developing rollers 21a and 21b.

Developing unit 4 a + 4 b r 4 c in which toner T of the same color is accommodated via 21 c and 21 d
.

Since the configuration is such that 4 dl is collected, there is no need for a special mechanism, and moreover, the developing rollers 21a and 21b.

By simply changing the bias relationships of 21c, 21d, etc., it becomes possible to distinguish between supply, recovery, and non-use, making control easier.

Note that the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a developing device in which the space factor around the image carrier is small, toner replenishment is easy, and there is no noise.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention,
FIG. 1 is a schematic configuration diagram of a developing device, FIG. 2 is an internal configuration diagram of a full-color printer employing the developing device of the present invention, FIG. 3 is a partially enlarged view of FIG. 1, and FIGS. Each figure shows a different conventional example. 2... Image carrier (photosensitive drum), 4... Developing device, 4a to 4d... Developing device unit, 20... Developer holding body (developing drum), 21a, 21b, 21c. 21d...Developer transfer means (developing roller) T+T,
l TMI Tcl "r,"'Developer (toner).

Claims (1)

[Scope of Claims] A developing device capable of multi-color development of an electrostatic latent image formed on an image carrier, provided opposite to the image carrier and holding a developer layer on the surface of the image carrier. a developer holder that develops the electrostatic latent image formed on the developer holder; A developing device comprising a plurality of developer transfer means for recovering the developer on the developer holder after developing an image.