JPH0895368A - Image forming device - Google Patents

Abstract

(57) [Summary] [Object] To provide an image forming apparatus capable of preventing unevenness in image density due to an imbalance in toner consumption with a simple configuration. A toner replenishing roller 11 provided in a toner hopper 10 is rotatably driven by a drive device 12 capable of rotating in the normal and reverse directions. The toner replenishing roller 11 is divided into three areas, a central portion and left and right portions, and a central roller portion 18 fixed to a roller shaft 17 is provided in the central portion. On the other hand, the left and right portions are provided with left and right roller portions 20 on the roller shaft 17 via a one-way clutch 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile, etc., in which an electrostatic latent image formed on an image bearing member is developed by a developing device using a two-component developer. .

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus equipped with a developing device using a two-component developer, if the development of an image in which the image portion is partially offset is repeated for a long time, the toner density in the portion corresponding to the image portion decreases. As a result, the toner density is likely to be different from that of the other non-developed portion. Therefore, if the entire surface image is developed immediately after that, there arises a problem that a partial defect in image density occurs due to a partial decrease in toner density. Further, when toner is partially consumed and the toner concentration in this portion decreases, if the toner is uniformly replenished over the entire width by the signal of the toner concentration detector provided in the lowered portion, the toner in that portion Although the carrier ratio is proper, the toner becomes excessive in other portions. Therefore, in a developing device using a two-component developer, in order to prevent the occurrence of such a phenomenon, the developer is agitated in the width direction to make the toner concentration uniform in the width direction.

However, when the developing width is widened, there is a time limit in uniformizing the toner density in the agitating member in the width direction, and it is not possible to reliably prevent a partial defect in the image density. .

Therefore, in order to prevent such a partial toner concentration, in JP-A-60-131573, the toner supply port is covered with a plurality of plate members, and at least one plate member is moved to open the toner supply port. And a toner replenishing device that replenishes toner according to the copy size. In this apparatus, the toner can be replenished according to the portion where the toner is consumed, and it is possible to prevent the unevenness of the copy density due to the imbalance of the toner consumption.

[0005]

However, the above-mentioned toner replenishing device requires a device for moving the plate material,
There is a problem in that the size of the device becomes large due to the configuration of changing the opening.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to provide an image forming apparatus capable of preventing uneven image density due to imbalance of toner consumption with a simple structure.

[0007]

To achieve the above object, the present invention provides an image forming apparatus in which an electrostatic latent image formed on an image bearing member is developed by a developing device using a two-component developer. A toner replenishing member for replenishing the developing device by rotating the toner stored in the toner storage portion is coaxially divided into two or more and rotatable independently. It is characterized in that a driving means for rotatively driving the toner replenishing member is provided, and the toner replenishing member for replenishing the toner in a region corresponding to a portion where the toner density is lowered in the width direction of the image formation is rotationally driven.

Further, in order to achieve the above object, according to the present invention, when it is set that a plurality of images each having a size smaller than the maximum image forming width are continuously formed, at least the image is formed and the image is formed at the same time. The toner replenishing member that replenishes toner to a region substantially corresponding to the size is driven to rotate.

Further, in order to achieve the above object, the present invention is characterized in that the toner replenishing member is provided in the toner storage portion, and the toner storage portion is detachable from the main body of the image forming apparatus. .

[0010]

According to the above structure, the toner replenishing member for replenishing the developing device by rotating the toner stored in the toner storage portion is divided into two or more coaxially, and the toner replenishing members are independent from each other. Since the toner replenishing member for revolving each toner replenishing member is provided and the toner replenishing member for replenishing the toner in the area corresponding to the portion where the toner concentration decreases in the width direction of the image formation is rotationally driven, Even if the toner is partially consumed, the toner can be replenished only to this portion, and the unevenness of the image density can be prevented.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic view showing an image forming system of an image forming apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a drum-shaped photoconductor serving as an image carrier, and when the photoconductor 1 is rotationally driven in the clockwise direction, its surface is charged by a charger 2 and its charged portion is shown in the figure. An electrostatic latent image is formed by the optical writing by the optical writing unit that does not exist. This latent image is developed by the developing device 3 into a toner image, which is transferred under the action of the transfer device 4 to a transfer sheet (not shown) fed in synchronism therewith. The transfer paper on which the toner image is transferred is separated from the photoconductor 1 by the separator 5 and conveyed to a fixing device (not shown). After fixing, the transfer paper is ejected to the outside of the machine or the like. On the other hand, the residual toner on the photoconductor 1 after the transfer is cleaned by the cleaning device 6, and the residual charge is removed by the static eliminator (not shown) to prepare for the next image formation.

The developing device 3 is composed of a toner and a carrier.
A device that uses a component developer, and when the toner is consumed and the ratio of the toner and the carrier changes due to the use, a signal from a toner concentration detector 7 provided in the developing device 3 causes a toner hopper 10 that is a toner storage unit. Toner is replenished to the developing device 3.

Here, it is assumed that the image forming apparatus of this embodiment has a width of the photosensitive member 1 and a width of the developing device 3 of 900 mm and conveys the transfer paper with the center as a reference. If the central portion 210 mm (A4 vertical width) of toner is continuously consumed, the toner concentration of this portion decreases, and if the toner concentration detector 7 is at the center in the width direction, the toner concentration decreases. Thus, the toner is uniformly supplied from the toner hopper 10 over the entire width. When the toner is replenished in this way, the ratio of the toner to the carrier in the central portion becomes appropriate, but the toner becomes excessive in other portions. A horizontal stirring member 8 for stirring the developer in the width direction is provided in the developing device 3.
However, it takes some time for the horizontal stirring member 8 to uniformly stir the developer in the width direction, and if image formation is performed with the maximum width while the width direction is not uniform, the image density becomes unsatisfactory. As described above, there is a problem that uniformity occurs.

Therefore, the present invention takes the following measures in order to solve such a problem.

In FIG. 2, a toner replenishing roller 11 provided in the toner hopper 10 is rotationally driven by a driving device 12 capable of rotating in the normal and reverse directions. The drive device 12 includes a reversible motor 13, pulleys 14 and 15 fixed to the motor shaft and a roller shaft 17 of the toner supply roller 11, and a belt 16 wound around the pulleys 14 and 15. Has been done.

The toner replenishing roller 11 is divided into three areas, a central portion and left and right portions. The central portion is shown in FIG.
Further, as shown in FIG. 3A, a central roller portion 18 fixed to the roller shaft 17 is provided. On the other hand, the left and right portions are provided with left and right roller portions 20 on the roller shaft 17 via a one-way clutch 19 as shown in FIGS. 2 and 3B. The left and right one-way clutches 19 are connected in the same direction. Further, the width of the central roller portion 18 is preferably set to a substantially predetermined width of the transfer paper, for example, the vertical width of A4.

In the image forming apparatus having such a configuration, if the central roller portion 18 and the left and right roller portions 20 are rotated when the toner replenishing roller 11 is normally rotated, the toner replenishing roller 11 is rotated.
When the central roller portion 18 is rotated in the reverse direction, the left and right roller portions 20 are not rotated by the one-way clutch 19. Therefore, the toner concentration detector 7 can be arranged at a position corresponding to at least one of the central portion and the left and right portions, and the toner replenishing roller 11 can be controlled to rotate normally and reversely by the signal. Further, instead of the toner density detector 7, a detector 9 for detecting the density of the toner image formed on the photoconductor may be used to control by the signal. Moreover, since the toner in the central portion can be replenished with a simple configuration in which the rotation direction of the toner replenishing roller 11 is changed, the apparatus does not become large and can be provided at a low cost. The toner replenishing roller 11 may be any one that can reversibly replenish toner such as foamed polyurethane, a fur brush, and a grooved roller.

By the way, in the above control, toner is replenished when a difference in image density occurs between the central portion and the left and right portions, so that it is possible that an image having an uneven image density is sufficiently formed. Therefore, in the above embodiment, when a large number of A4 vertical image formations are set by repeat or the like, the toner replenishing roller 11 may be reversed at the same time as the image formation.

According to this structure, the toner consumed in the image formation can be predicted and supplied, so that the difference in image density between the central portion and the left and right portions hardly occurs, and an image with uneven image density can be formed. It can also be prevented from being formed.

4 and 5 are a perspective view and a sectional view showing another embodiment of the present invention. In this embodiment, a toner cartridge 21 which is detachable from the developing device 3 is provided as a toner storage portion. This toner cartridge 21 is provided with an appropriate number of small holes 22, and when the cartridge is set on the developing device 3, the small holes 22 face the developing device 3 as shown in FIG. The stirring member 2 provided inside the toner cartridge 21 as a toner replenishing member
By rotating 3 the developing device 3 through the small hole 22.
It is configured to replenish the toner. Stirring member 2
3 is divided into three areas, a central portion and left and right portions, and the central portion is a central stirring plate 2 fixed to a rotary shaft 24.
5 are provided. On the other hand, the left and right portions are provided with the left and right stirring plates 27 via the spring clutch 26, which is connected in the same direction to the rotary shaft 24 as the connecting direction.

In the image forming apparatus having such a configuration, the central stirring plate 25 and the left and right stirring plates 27 can be simultaneously rotated by reversibly rotating the rotating shaft 24, or only the central stirring plate 25 can be rotated. The same effect as the example is obtained. Moreover, since the toner cartridge 21 can be attached to and detached from the developing device 3, it is easy to replace the toner storage portion.

Although the toner replenishing member is divided into the center and the left and right in the above-described embodiment, the toner replenishing member may be divided into the left and the right in a device that conveys the transfer paper on the basis of one side.

[0024]

According to the first aspect of the invention, since the toner replenishing member for replenishing toner to the area corresponding to the area where the toner concentration decreases in the width direction of the image formation is rotationally driven, the toner is partially supplied. Even if the toner is continuously consumed, the toner can be replenished only to that portion, and the unevenness of the image density can be prevented.

According to the second aspect of the present invention, since the toner consumed in the image formation can be predicted and supplied, the difference in image density between the central portion and the left and right portions hardly occurs.
It is also possible to prevent the formation of an image having non-uniform image density.

According to the third aspect of the present invention, even if the toner storage portion is detachably attached to the developing device, the toner can be replenished only to the portion, and the toner storage portion can be easily replaced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an image forming system of an image forming apparatus according to the present invention.

FIG. 2 is a sectional view showing a toner supply roller of the present invention.

FIG. 3A is a sectional view of a central roller portion of the toner supply roller, and FIG. 3B is a sectional view of left and right roller portions of the toner supply roller.

FIG. 4 is a perspective view of the toner cartridge of the present invention.

FIG. 5 is a sectional view of the toner cartridge of the present invention.

FIG. 6 is a sectional view showing a state in which the toner cartridge of the present invention is set in a developing device.

[Explanation of symbols]

 3 developing device 10 toner hopper 11 toner replenishing roller 12 driving device 17 roller shaft 18 central roller part 19 one-way clutch 20 left and right roller part 21 toner cartridge 23 stirring member 24 rotating shaft 25 central stirring plate 26 spring clutch 27 left and right stirring plate

Claims (3)

[Claims] 1. An image forming apparatus in which an electrostatic latent image formed on an image bearing member is developed by a developing device using a two-component developer, by rotating the toner stored in a toner storage portion. The toner replenishing member for replenishing the developing device is divided into two or more parts which are coaxially rotatable and can be rotated independently of each other. An image forming apparatus characterized in that the toner replenishing member for replenishing toner to a region corresponding to a portion where the toner concentration is lowered in the width direction is rotationally driven. 2. The image forming apparatus according to claim 1, wherein when a plurality of images having a size smaller than the maximum image forming width are set to be continuously formed, at least the image is started and the image is formed at the same time. The image forming apparatus is characterized in that the toner replenishing member that replenishes toner to a region substantially corresponding to the size is driven to rotate. 3. The image forming apparatus according to claim 1, wherein the toner replenishing member is provided in the toner storage portion, and the toner storage portion is removable from the image forming apparatus main body. Image forming apparatus.