JPH09101676A - Developing device and multicolor image forming apparatus using the same - Google Patents

Abstract

The present invention provides a small-sized and simple-structured developing device, and a small-sized and labor-saving multicolor image forming apparatus. A developing device 11 supplies a toner T contained in a developing casing 12 to a developing roll 14 by a supply roll 13. The developing roller 14 transfers the toner T to the electrostatic latent image on the photoconductor 18 to develop the electrostatic latent image. A sheet member 15 is bonded to the peripheral edge of the lower opening of the developing casing 12 by hot melt or high frequency bonding. The sheet member 15 is a single-sheet sheet having a trapezoidal opening at the center, and the upper portion a that abuts the developing roll 14 serves as a doctor blade,
The lower part c serves as a scooping sheet, and the side portions integrally connecting these serve as sealing members for sealing both ends of the developing roll 14. Since the upper portion a is in surface sliding contact with the developing roller 14, the developing roller 14 can be easily rotated in the clockwise direction in the reverse direction. To prevent unnecessary toner from flying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device and a multicolor image forming apparatus using the same, and more specifically to a small developing device with a small number of members used and easy to assemble, and a multicolor image forming apparatus using the same. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, various developing methods using a non-magnetic one-component developer have been proposed because an image forming apparatus does not require a toner conditioner and is suitable for colorization. There is.

FIG. 5 schematically shows a general structure of an image forming section which is a main part of a conventional color image forming apparatus. As shown in the figure, the image forming unit includes a charger 2
A photosensitive drum 1 which is rotated in a clockwise direction indicated by an arrow A in FIG.
An exposure device (not shown) that exposes the photosensitive drum 1 according to image information to form an electrostatic latent image on the peripheral surface thereof, and color toner 3 (3a, 3b, and 3c) on the electrostatic latent image is developed on the developing roll 4
Developing devices 5 (5a, 5b, and 5) that perform transfer (4a, 4b, and 4c) to perform development (to form an electrostatic latent image into a toner image).
c). The color toner 3 is a non-magnetic one-component developer and is a container 6 (6a, 6b and 6c) of the developing device 5.
Housed within. The developing roll 4 is rotatably engaged with the opening of the container 6, and is arranged at the contact point P with the photosensitive drum 1.
Then, the color toner 3 is transferred to the photosensitive drum 1.
The color toner image formed on the peripheral surface of the photosensitive drum 1 by this transfer is transferred to a sheet of paper (not shown) and thermally fixed on the sheet of paper.

The contact point P indicates the contact line on the peripheral surfaces of the photosensitive drum 1 and the developing roll 4, and in actuality, it is not a contact but a gap of about 200 μm (millimeter micron) which is almost abut. Is formed.

In order to form a color image, as shown in the figure, at least three types of developing devices for developing the three primary colors of yellow (yellow), magenta (red dye) and cyan (blue with green) are provided. 5 is required, and in some cases, four types of developing devices including a developing device dedicated to developing black for character information and the like must be prepared.

In this case, when the developing device 5a develops the first color toner 3a and then the developing device 5b develops the second color toner 3b, The developing rolls 4a and 4c of the developing device 5c for developing after this must be separated from the photosensitive drum 1. The color toner 3 before development adheres to the entire surface above the contact point P of the developing roller 4 which is not developed, and the peripheral surface below the contact point P is not transferred (non-transferred) by the previous development. The residual color toner 3 which has been printed is attached. Generally, for example, in a document, the print area ratio is 5
%, A large amount of color toner 3 corresponding to 95% of the whole remains on the developing roll 4 after development. That is, the color toner 3 is always attached to one surface above and below the contact point on the peripheral surface of the developing roller 4 facing the photosensitive drum 1. Therefore, when the development with the second color toner 3b is performed by the developing device 5b as described above,
If the developing roller 5a that has completed the development and the developing rollers 4a and 4c of the developing device 5c that performs the subsequent development are in contact with the photosensitive drum 1 as in the case where the development is performed, the color toners 3a And 3c may be unnecessarily transferred to the photosensitive drum 1. Then, the transferred color toners 3a and 3c
However, there is a problem that the developing device 5b that is currently developing scrapes off the peripheral surface of the photosensitive drum 1 as excess color toner and mixes colors in the container 6a of the developing device 5b. In order to avoid this, only the developing roll 4b of the developing device 5b under development is in contact with the photosensitive drum 1 so that the developing rolls 4a and 4c of the other developing devices 5a and 5c are in contact with each other.
Are separated from the photosensitive drum 1.

Therefore, the three developing devices 5a, 5b and 5 are provided.
The c is configured to move in both forward and reverse directions with respect to the peripheral surface of the photosensitive drum 1 indicated by double-headed arrows B1, B2, and B3 in the figure.

Further, as described above, the developing roll 4 is disposed so as to engage with the opening of the container 6 of the developing device 5. The engaging portion between the developing roll 4 and the opening of the container 6 prevents the excess color toner 3 from leaking outside from the engaging portion between the developing roll 4 and the container 6 and contaminating surrounding members. In, various accessory members are arranged.

FIG. 6 is a perspective view showing such a developing roll 4 together with its accompanying members. As shown in the figure,
Sealing members 7 are provided at both ends of the developing roller 4 in the longitudinal direction between the developing roller 4 and a container 6 (not shown).
These seal members 7 prevent the color toner 3 from leaking from the shaft end of the developing roll 4. A doctor blade 8 is erected on the upper part of the developing roll 4 in parallel with the axis. This doctor blade 8 has a container 6 as a whole.
Of the toner is prevented from leaking from the upper portion of the opening of the color toner 3, and the lower end of the toner is substantially in contact with the peripheral surface of the developing roller 4 to adhere to the peripheral surface of the developing roller 4 from inside the container 6. The color toner 3 conveyed to the contact portion between the photosensitive drum 1 and the developing roll 4 is suppressed to a predetermined thickness. A scooping sheet 9 is disposed below the developing roll 4. Scooping sheet 9
On the one hand, the color toner 3 is prevented from leaking from the lower part of the opening of the container 6, and on the other hand, the residual color toner 3 of the non-dislocation portion (non-printing portion) after development on the peripheral surface of the developing roll 4 is introduced into the container 6. Play a role.

[0010]

However, the above-mentioned conventional color image forming apparatus has the following problems.

First, there is a problem in that the structure of the member attached to the developing roll of the developing device is complicated as described above, and it is difficult to reduce the size in terms of design or manufacturing process. In particular, sponges are used for the above-mentioned sealing members and the like from the viewpoint of their functions, but attachment of sponges of small pieces in the assembly process is difficult to automate, and it depends exclusively on manual work. If the members are mounted by hand in this way, there is a problem in that the positional accuracy is poor, the frequency of occurrence of defective products such as toner leakage increases, and the product yield decreases. In order to improve the product yield, there is no solution except to train a skilled person and use it for the work or to carry out the work carefully with sufficient time. In either case, the problem arises that it increases the cost of the assembly process. Further, as described above, in order to bring the developing device into and out of contact with the photosensitive drum at the time of development execution and non-execution, a drive mechanism for driving the contact and separation movement is required. Since it cannot be miniaturized and is large, its driving mechanism also becomes large, and a strong driving force, that is, a large power source is required. This not only cannot cope with the recent demand for downsizing of devices, but also increases the product price and raises the use and maintenance cost, which is uneconomical. Further, when the developing device is moved toward and away from the developing device as described above, the adjusting mechanism for accurately maintaining the positional accuracy when returning to the developing position becomes extremely complicated.
It has a problem of increasing the product price more and more.

An object of the present invention is to provide a small-sized and simple-structured developing device and a small-sized and labor-saving multicolor image forming apparatus.

[0013]

The structures of a developing device and a multicolor image forming apparatus according to the present invention will be described below. First, a developing device according to a first aspect of the present invention includes a developing casing that accommodates a one-component developer, and a developing casing that is rotatably disposed so that a peripheral surface portion faces the inside and outside of the developing casing. A developing roll that carries the one-component developer on the peripheral surface for development and conveys it, and is formed into a single sheet having an opening of a predetermined size in the substantially central portion. The developing roll is fixed to both ends in the rotation direction and both ends in the longitudinal direction of the developing roll, and the opening edge is brought into contact with the peripheral surface of the developing roll inside the developing casing to form a gap between the developing casing and the developing roll. In addition to sealing, the opening serves as a supply portion of the one-component developer to the developing roll, and one of the contact portions of the opening edge portion in the developing roll rotation direction regulates the layer thickness of the one-component developer. Double friction charging unit Constructed and a the sealing member. This makes it possible to provide a developing device that is small and has a simple structure.

Next, a second aspect of the present invention is provided with a plurality of developing devices around the image carrier which is circulated and moved, and a charging process, an exposing process and a developing process are sequentially repeated on the surface of the image carrier to carry out a multicolor image. It is applied to a multi-color image forming apparatus for forming an image.

In the multicolor image forming apparatus of the present invention, the above-mentioned plurality of developing devices are rotatably arranged so as to expose the peripheral surface portion to the inside and outside of the developing casing, each containing a one-component developer. A developing roll for carrying the one-component developer on the peripheral surface for developing the latent image formed on the image carrier and carrying the same; and a single sheet having an opening of a predetermined size in the substantially central portion thereof. And is fixed to both ends of the developing casing in the developing roll rotation direction and both ends of the developing roll in the developing roll longitudinal direction, and the opening edge is brought into contact with the peripheral surface of the developing roll inside the developing casing. While sealing the gap between the developing casing and the developing roll,
The opening serves as a supply portion of the one-component developer to the developing roll, and one of the abutting portions of the opening edge portion in the developing roll rotation direction serves as a layer thickness regulation / friction charging portion of the one-component developer. And a seal member that has been formed, and for the developing device in the non-developing step among the plurality of developing devices,
The developing roll is rotated by a predetermined angle in the direction opposite to the developing step so that the one-component developer is not carried on the peripheral surface of the developing roll outside the developing casing, and the developing roll is moved to the rotating position. A driving means for holding the developing roller and a means for applying a predetermined bias voltage having the same polarity as the charging potential of the surface of the image carrier to the developing roll are provided. This makes it possible to provide a compact and labor-saving multicolor image forming apparatus.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view of the developing device according to the first embodiment. As shown in the figure,
The developing device 11 accommodates the toner T and has a hopper-shaped developing casing 12 having an opening below, a supply roll 13 rotatably supported inside the lower opening of the developing casing 12, and the supply roll 13. The developing roller 14 rotatably disposed outside the lower opening of the developing casing 12 in pressure contact with the sheet, and the sheet member 1 interposed between the developing roller 14 and the peripheral edge of the opening of the developing casing 12.
5, and a leaf spring 16 for urging the portion of the sheet member 15 that abuts the upper portion of the developing roll 14 from above to below.
It has. Above the inside of the developing casing 12, there is a stirring blade 17 that rotates in order to keep the toner T always in a fluidized state so that the toner T contained therein does not coagulate or the like and hinders development. It is provided.

The developing casing 12 includes a toner T
Is filled and replenished from above. The toner T is a non-magnetic one-component developer composed of fine particles, is stirred by the stirring blade 17, flows toward the supply roll 13, and adheres to the upper half surface of the supply roll 13. The supply roll 13 is a roll made of a foam (sponge body) such as conductive rubber,
The developing roller 14 is pressed against the developing roller 14 with a biting amount of about 0.5 mm to 0.7 mm, and rotates in the counterclockwise direction in the drawing to slidably contact the developing roller 14 during development. This supply roll 13
Due to the adhesiveness formed by the porous peripheral surface, the toner T is held and transported, and the toner T is frictionally charged by sliding contact with the developing roll 14, and the toner T is pressure-bonded so as to rub against the developing roll 14. And transfer.

The developing roll 14 is a roll made of an elastic material such as silicon rubber. During development, the developing roll 14 rotates counterclockwise in the drawing while developing the toner T supplied from the supply roll 13 in the developing casing 12. It is conveyed to the outside of the casing 12. The sheet member 15, which will be described in detail later, is made of a urethane sheet or Mylar film having a thickness of about 100 μm, and is provided with a supply roll 13 at the center.
Further, the opening is provided so as to escape from the sandwiching by pressure contact with the developing roll 14, and the peripheral edge of the opening is adhered to the end of the developing casing 12 by hot melt or high frequency adhesion.

The toner T conveyed by the developing roll 14 is charged by further triboelectric charging at the upper contact point (contact peripheral surface) between the developing roll 14 and the sheet member 15, and is developed in a more stable state. The sheet is held by the roll 14 and adjusted to a predetermined thin layer by the doctor blade function of the upper contact portion a of the sheet member 15, and is carried out of the developing casing 12.

The lower portion of the developing roller 14 rotated approximately 180 degrees from the upper contact point faces the photosensitive belt 18 which will also be described in detail later. In this embodiment, the distance between the developing roller 14 and the photosensitive belt 18 is about 0.2 mm.
A gap of some degree is provided. This gap is defined by the photoconductor belt 1.
It is maintained by the tension of the guide plate 19 and the photoconductor belt 18 which support the facing portion 8 from below. The toner T conveyed by the developing roller 14 is transferred to the electrostatic latent image formed on the photoconductor belt 18 at the facing portion and developed.

In this development, a negative high potential is applied to the photosensitive belt 18 by the charger, and a negative low potential portion is selectively formed on the surface of this high potential by the exposure of the exposure head. Then, a negative bias voltage is applied to the developing roller 14, whereby the toner T on the peripheral surface of the developing roller 14 is attracted and transferred to the low potential portion of the photoconductor belt 18 having a relatively positive polarity.
As a result, development is performed on the photosensitive belt 18. After the development, the toner T remaining on the developing roll 14 passes through the opening edge c-1 which is the lower contact end of the sheet member 15 with the developing roll 14 and is collected in the developing casing 12.

In such a configuration, the toner leakage sealing function, the triboelectric charging function, the doctor blade function, and the toner collecting function are provided at the peripheral portion of the opening of the developing casing 12, that is, at the upper and lower portions of the developing roller 14 and both ends in the axial direction. Each functional part having is formed of one sheet member as described above.

FIG. 2A is a developed plan view of the sheet member. As shown in FIG. 3A, the seat member 15 is a single-sheet seat having a trapezoidal opening at the center,
The upper part 21 of the development view corresponds to the view of arrow E in FIG. 1, and the lower part 22 of the development view corresponds to the view of arrow F of FIG. Also, the same figure
(b), (c), and (d) show partial modifications thereof, respectively.

As shown in FIG. 1A, the sheet member 15
Is the upper contact portion a that abuts the developing roll 14 described above.
The sliding contact surface of the portion (indicated by diagonal lines in the drawing) that is in contact with the developing roll 14 is subjected to a roughness treatment such as a matting treatment or a hairline treatment to form a rough surface. As shown in FIG. 1, the upper contact portion a is pressed against the developing roll 14 side by a biasing member (a leaf spring 16 in this example). As described above, the pressing force and the roughly formed sliding contact surface give the toner T passing through the upper contact portion a a charge by frictional charging and adjust the toner T into a predetermined thin layer. In the selection of the sheet material, in the case of a material having a low friction coefficient, good results can be obtained by performing the roughness treatment on the sliding contact surface of the upper contact portion a as described above.

On the other hand, the opening edge c-1 of the lower contact portion c of the sheet member 15 is opened larger than the upper contact portion a,
As a result, both end portions of the opening of the sheet member 15 that integrally connects the upper contact portion a and the lower contact portion c are formed so as to diverge from the upper contact portion a to the lower contact portion c. The toner T collected in the developing casing 12 after finishing the development tends to be somewhat diffused in the lateral direction (width direction) of the developing roller 14 as compared with when it is carried out.
Are scraped inward by the inclined portion. This prevents the toner T from leaking to the end of the developing roll 14.

The opening edge a-1 of the upper contact portion a of the sheet member 15 has a center line Ct of the developing roll 14.
(See also FIG. 1) It is formed so as to protrude by about 2 mm to 3 mm. As a result, the toner T is introduced to some extent and a toner layer having a predetermined thickness is formed between the toner T and the developing roller 14. Both ends of this protruding portion are notched upward to a position corresponding to the center line Ct of the developing roll 14. Due to this notch, the upper contact portion a maintains the same degree of freedom at both ends as in the central portion, whereby a uniform toner layer can be formed.

Further, the developing roll 1 in the cutout portion
The upper end portion b formed at a position corresponding to the center line Ct of 4 forms a straight line having a certain length along the center line Ct. As a result, the toner T at the end can be reliably scraped off. The edge connecting the upper end b forming this straight line and the projecting opening edge a-1 may be formed by attaching R (d1) as shown in FIG. It may be formed vertically (d2) as shown in FIG. 6 (c), or may be formed with an inclination (d3) as shown in FIG.

As described above, in the mode of this embodiment,
A single sheet member 15 has an integral structure having three functions of a doctor blade, a side sheet (sealing member) and a scooping sheet. Therefore, in the assembling process, manual work is eliminated, automation is easy, and a small-sized developing device can be easily realized.

Further, the upper contact portion a functioning as a doctor blade has a structure in which the upper contact portion a is in sliding contact with the developing roll 14 as described above, and since the other functional portions are also integrally formed into a sheet shape, the developing roll 14 There is no possibility that the developer (toner T) will be scattered or the functional portions will be deformed even if the toner is rotated in the reverse direction. Therefore, the developing roll 14 can be easily rotated in the reverse direction.

Next, as a second embodiment, as described above, the developing device 1 which is extremely small and has a characteristic that the developing roll 14 can be easily rotated in the reverse direction.
1 is used to configure a multicolor image forming apparatus. Hereinafter, this will be described.

FIG. 3 is a schematic side sectional view showing a schematic structure of a main part of the multicolor image forming apparatus. As shown in the figure, in the multi-color image forming apparatus, a belt drive roll 21 and a driven roll 22 are arranged at a predetermined interval in the front-back direction (left-right direction in the drawing) inside the apparatus, and the belt drive roll 21 and the driven roll 21 are driven. An endless photoconductor belt 18 is rotatably stretched between the rolls 22. The photosensitive belt 18 is formed to have a width substantially the same as the width of the paper on which the multicolor image is transferred, and rotates in the clockwise direction indicated by arrow G in the figure. A corona charger 23 is provided upstream of the upper surface of rotation of the photosensitive belt 18 (on the left side of the drawing), and an LED head 24 is provided downstream thereof. The corona charger 23 uniformly charges the surface of the photoconductor belt 18 to a negative potential by corona discharge. The LED head 24 performs exposure according to the image information for each color to form an electrostatic latent image on the surface of the photoconductor belt 18 charged to the uniform negative potential.

Downstream of the LED head 24, there are four LED heads shown in FIG.
The developing device 11 (11a, 11b, 11c and 1 shown in FIG.
1d) are sequentially arranged, and the developing rolls 14 (14a, 14b, 14c and 14d) of these developing devices 11 are arranged.
Faces the upper rotating surface of the photosensitive belt 18. The guide plate 1 is brought into contact with the lower surface of the photoconductor belt 18 at the facing portion.
9 (19a, 19b, 19c and 19d) are arranged,
As a result, a gap of about 200 μm is formed at the portion where the photosensitive belt 18 and the developing roller 14 face each other. The four developing devices 11 are Y (yellow: yellow), M which are three primary colors of subtractive color mixture in color printing.
(Magenta: red dye) and C (cyan: greenish blue) color toners Ty, Tm, and Tc, and Bk (black: black: dedicated to forming a black monochromatic image such as characters).
The color toner Tk of black) is respectively supplied to the developing casing 12 (12
a, 12b, 12c and 12d).

In this multicolor image forming apparatus, the rotating photoreceptor belt 18 is charged by the corona charger 23, and the LED head 24 exposes the yellow image information to the charged surface, so that the yellow image is statically exposed. An electrostatic latent image is formed, and the yellow color toner Ty is transferred (developed) to the electrostatic latent image by the developing device 11a. Next, the photoconductor belt 18 is continuously rotated, charging is performed again by the corona charger 23, an electrostatic latent image of a magenta image is formed by the exposure of the LED head 24, and the magenta color toner Tm is transferred by the developing device 11b. (Development) is performed. This is the developing device 1
Cyan toner Tc transfer and developing device 1c
By sequentially repeating the transfer of the black color toner Tk by 1d, the four color toners Ty, Ty are formed on the photosensitive belt 18.
Superimpose m, Tc and Tk. The color image in which the four colors are superimposed is transferred to a sheet (not shown) by the transfer unit 25.

In the transfer (development) of the above color toner,
The developing roller 14 of each developing device 11 is connected to an independent pulse motor (not shown) for each developing roller 14, rotates at the same speed in the feeding direction of the photosensitive belt 18 during development, and is assisted by the leaf spring 16. The color toner T is thinned and conveyed by the upper contact portion a of the sheet member 15, and the color toner T is transferred to the photosensitive belt 18 and developed.

The developing roll 14 rotates in the reverse direction at the time of non-developing, that is, at the time of developing another color by the other developing device 11, and the rotation of the supply roll 13 (see FIG. 1) and the sheet member 15 are stopped. With the opening edge c-1 of the lower contact portion c, the color toner T remaining on the developing roll 14 is scraped off to leave the roll surface free of toner, thereby preventing the toner T from flying unnecessarily. The reverse rotation angle at this time is about 90 degrees in the front and rear (left and right in the drawing) in the vicinity of a point (opposite line) facing the photosensitive belt 18. As a result, the surface facing the photosensitive belt 18, that is, the substantially half surface of the developing roller 14 is in a state where the toner T does not exist.

Further, a potential equal to or higher than the charging potential of the photosensitive belt 18 is applied to the developing roll 14 so that the color toner T does not fly backward, and the toner developed on the photosensitive belt 18 is prevented. I try to pass the image.

FIGS. 4 (a) and 4 (b) show movement models of the color toner T described above. FIG. 3A shows the developing process for the exposed portion according to the image information. As shown in the figure,
The photoconductor belt 18 is composed of a conductor 18-2 on the back surface and an insulating dielectric material 18-1 on the front surface. For example, "-650V (volt)" is applied to the front surface by the corona charger 23 (see FIG. 3).
Uniform high-potential portion 18-1b is formed. The low potential portion 18-1a in which the potential is attenuated to approximately "-50V" is generated on this surface by the exposure of the LED head 24, and thereby the high potential portion 18-1 in which the potential is substantially maintained at "-650V" is produced.
An electrostatic latent image is formed by b and the low potential portion 18-1a of "-50 V" by exposure. On the other hand, the developing roll 14
Conveys the non-magnetic color toner T charged to a weak negative potential to a portion facing the photoconductor belt 18. A developing bias of "-250V" is applied from the power supply 26 to the developing roll 14, and a potential difference of "-200V" is generated between the developing roll 14 and the low potential portion 18-1a of the electrostatic latent image of "-50V". To form. That is, the low-potential portion 18-1 a of the electrostatic latent image forms a positive polarity potential relative to the developing roll 14. Due to the electric field due to this potential difference, the color toner T charged in the negative polarity transfers to the positive polarity electrostatic latent image low potential portion 18-1a of the photoconductor belt 18 to form a color toner image. The developed color toner image is conveyed to the transfer unit 25 by the rotation of the photosensitive belt 18 as described above (see FIG. 3). The sheet is conveyed to the transfer unit 25 by a not-shown conveying mechanism, and the transfer roll pairs 27a and 27b are conveyed.
And the transfer belt 2 is sandwiched between the photoconductor belt 18 and
The toner image on the photoconductor belt 18 is transferred onto the sheet by a transfer bias of a positive potential applied to a transfer power source (not shown) at 7a.

Then, when developing is performed by another developing device 11, the developing roll 14 rotates in the reverse direction, and the supply roll 13 and the opening edge c-1 of the lower contact portion c of the sheet member 15 are brought into contact with each other. The residual color toner T is removed by
As shown in (b), the roll surface facing the photosensitive belt 18 is set to a toner-free state. Then, the developing roll 14
The developing bias of "-250 V" is continuously applied from the power source 26. Since the surface of the developing roller 14 is cleaned and the color toner T is not adhered, even if the developing bias is applied in this way, the developing roller 14 in the non-development state does not use the color toner T on the photosensitive belt 18. T
Never fly. On the other hand, by applying the developing bias to the developing roll 14 in the non-developing state, the color toner T developed on the photosensitive belt 18 is prevented from flying backward to the developing roll 14 side. .

Incidentally, FIG. 3C shows the undeveloped developing roll 14
In order to prevent the color toner T from flying to the photoconductor belt 18 from the developing bias, the developing bias is cut (grounded). The photoconductor belt 18
The reverse flying state of the color toner T in the case where the color toner T is not separated is shown. By adopting this embodiment, it is possible to eliminate the inconvenience as shown in FIG. 7C even if the developing roller 14 which is not developed is separated from the photosensitive belt 18.

As described above, since the developing roll 14 in the non-developing state can be rotated in the reverse direction, it is easy to put the surface of the developing roll 14 in the toner-free state. Photoconductor belt 18
It is possible to prevent unnecessary flying of the color toner T of the non-developed color onto the photoconductor belt 18 without separating from it, and to make the surface of the developing roll 14 in the non-developed state a toner-free state. Can be continuously applied, which prevents the developed color toner T on the photoconductor belt 18 from flying back to the developing roller 14 in the non-developed state. This makes it possible to form a high-quality image with a simple structure.

Since the developing device can be constructed in a very small size, it is possible to slightly rotate the developing device 11 from the developing position without providing a dedicated drive mechanism by utilizing the reverse rotation drive of the developing roll 14. This can be easily realized by appropriately changing the shape of the joint portion or using a cam or the like. By doing so, the facing point of the developing roller 14 facing the photosensitive belt 18 on the vertical line can be easily separated from the developing position, and the useless flight of the color toner T and the reverse flight can be further ensured. Can be prevented.

[0042]

As described above, according to the developing device of the present invention, since a plurality of functional parts are integrated into one part to have a seamless integrated structure, the yield of the device related to toner leakage can be improved. It is possible to provide an improved and thus inexpensive device. Similarly, by integrating a plurality of parts, the positional accuracy of each part is always kept constant, thus improving the reliability of the device. Similarly, by integrating a plurality of components, the number of stocks in the production factory is reduced and the component management is facilitated. Therefore, the management labor can be reduced and the labor can be saved. Similarly, the integration of a plurality of parts facilitates the handling of the parts during work, thus improving the efficiency of the assembly work. Similarly, by integrating a plurality of parts, it is possible to easily downsize the device.

Further, according to the multicolor image forming apparatus of the present invention, since the developing roll of the developing device can be rotated in the reverse direction, useless toner is transferred even when the developing device is kept in contact with the photoconductor during non-developing. There is no fear, and therefore, a drive mechanism for contacting / separating movement of the developing device is not necessary, which allows miniaturization and further contributes to energy saving. Further, since the developing device does not move to and away from the developing device, the positional accuracy of the image forming portion is kept constant, and therefore a high quality image is obtained and the reliability of the device is improved.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a developing device according to a first embodiment.

[FIG. 2] (a) is a developed plan view of a sheet member, (b), (c), (d)
[Fig. 3] is a diagram showing respective partial modifications thereof.

FIG. 3 is a schematic side sectional view showing a schematic configuration of a main part of a multicolor image forming apparatus according to a second embodiment.

4 (a) and (b) are diagrams showing a moving model of color toner,
FIG. 6C is a diagram showing a reverse flying state of color toner when the undeveloped developing roll is not separated from the photoconductor by the same image forming process as in the related art.

FIG. 5 is a diagram schematically showing a schematic configuration of a main part of a conventional color image forming apparatus.

FIG. 6 is a perspective view showing a developing roll of a conventional developing device together with an auxiliary member.

[Explanation of symbols]

1 Photosensitive Drum 2 Charging Device 3 (3a, 3b, 3c) Color Toner 4 (4a, 4b, 4c) Developing Roll P Contact 5 (5a, 5b, 5c) Developing Device 6 (6a, 6b, 6c) Container 7 Seal Member 8 Doctor blade 9 Scooping sheet T Toner 11 (11a, 11b, 11c, 11d) Developing device 12 (12a, 12b, 12c, 12d) Developing casing 13 Supply roll 14 (14a, 14b, 14c, 14d) Developing roll 15 Sheet member 16 Leaf spring 17 Stirring blade 18 Photoreceptor belt 19 (19a, 19b, 19c, 19d) Guide plate a-1, c-1 Opening edge a Upper contact portion c Lower contact portion 21 Belt drive roll 22 Driven roll 23 Corona charger 24 LED head 25 Transfer part Ty Yellow color toner Tm Magenta color toner Tc Shear Color toner Tk Black color toner

Claims (2)

[Claims] 1. A developing casing for accommodating a one-component developer, and a developing casing rotatably disposed so as to face a peripheral surface portion inside and outside the developing casing, for developing a latent image formed on an image bearing member. A developing roll that carries a one-component developer on its peripheral surface and conveys it, and a developing roller that is formed in the shape of a single sheet with an opening of a predetermined size in the substantially central portion. While being fixed to both ends and both ends of the developing roll in the longitudinal direction, the gap between the developing casing and the developing roll is sealed by bringing the opening edge portion into contact with the developing roll peripheral surface portion inside the developing casing. The opening serves as a supply portion of the one-component developer to the developing roll, and one of the contact portions of the opening edge portion in the developing roll rotation direction serves as a layer thickness regulation and friction charging portion of the one-component developer. Sealed part Developing apparatus is characterized in that it comprises, when. 2. A multicolor image in which a plurality of developing devices are provided around an image carrier that circulates, and a charging process, an exposing process, and a developing process are sequentially repeated on the surface of the image carrier to form a multicolor image. In the forming device, each of the plurality of developing devices is provided with a developing casing that accommodates a one-component developer, and is rotatably disposed so that a peripheral surface portion faces the inside and outside of the developing casing. A developing roll that carries and conveys the one-component developer on the peripheral surface for developing an image, and an opening of a predetermined size in the substantially central portion, which is formed into a single sheet, The casing is fixed to both ends in the developing roll rotation direction and both ends in the developing roll longitudinal direction, and the opening edge portion is brought into contact with the developing roll peripheral surface portion inside the developing casing so that the developing casing and the developing roll are connected. while While closing the gap, the opening serves as a supply portion of the one-component developer to the developing roll, and one of the abutting portions of the opening edge portion in the developing roll rotation direction is a layer of the one-component developer. A seal member that serves as a thickness regulation and friction charging unit, and a developing device outside the developing casing is provided for a developing device in the non-developing process among the plurality of developing devices. Drive means for rotating the developing roll by a predetermined angle in a direction opposite to the direction during the developing process so as to keep the one-component developer unsupported on the surface portion, and holding the image on the developing roll. A multicolor image forming apparatus comprising: a means for applying a predetermined bias voltage having the same polarity as the charging potential of the surface of the carrier.