JP2863556B2 - Electrophotographic developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention frictionally charges a developer inside a developing device,
The developer is held in a layered form on the surface of the developing roller and transported, and the electrostatic latent image on the photosensitive member is developed by contacting or approaching the photosensitive member, and a toner cartridge is detachably mounted on the developing unit. Related to the device.

2. Description of the Related Art In an image forming apparatus using an electrophotographic process such as an electrophotographic copying machine, an electrostatic printer, and a facsimile, an electrostatic latent image formed on a photoconductor by an electrophotographic process is developed by a developer in a developing process. The toner image is visualized as a toner image, and the toner image is transferred to a transfer sheet and fixed to form an image.

The development by the adhesion of the toner to the image portion in the above-described development process is performed based on the relationship between the charging polarity of the toner and the polarity of the development potential (difference between the image portion potential and the development bias). Therefore, the developing bias is set so that the developing potential of the image portion where the toner is manufactured to have a certain polarity has a polarity opposite to that of the toner. Explaining with an example of a non-magnetic one-component development process, the toner is manufactured so as to be charged to (-), and a developing bias is applied so that the development potential of the image area on the photoconductor becomes (+). . The development potential of the non-image area becomes (-),
The toner charged to (-) does not adhere and the background becomes white on copy or print.

However, at present, the charge amount (g / g
As shown qualitatively in FIG. 2, the distribution of m) is distributed over a certain range around the charge amount of (-), and (+)
Partially charged toner. Therefore, (+)
Is attached to the potential region (-), that is, the non-image portion.

The (+) toner adheres to the non-image area evenly on the photoreceptor, but in the transfer area, the (+) corona is used to transfer the (−) toner adhering to the image area to the transfer paper. Charge is being applied. As a result, the (+) toner adhering to the non-image portion receives the electrostatic repulsion and does not substantially adhere to the transfer paper. However, the mechanical contact force between the transfer paper and the photoreceptor (mainly Van der Waals force, other frictional force)
Some of the toner adheres to the transfer paper and is fixed by a fixing device, which is a mechanism of generating background stain.

This development becomes more remarkable in the case of the second transfer in the case where the transfer paper is thick paper or in the case of double-sided printing. The reason for this is that in the case of thick paper, the (+) toner repulsion force through the paper by the transfer charger is weakened, which makes it easier to adhere to the paper. In addition, thick paper has high rigidity and the paper surface has a photoconductor. This is because the toner in the non-image area on the photoreceptor easily adheres to the paper surface because of strong mechanical contact with the sheet. In the case of double-sided printing, the first fixing reduces the water content of the paper and increases the volume resistance of the paper, so that the repulsive force to the (+) charged toner attached to the photoconductor during the second transfer is reduced. And
(+) The toner easily adheres to the paper. Further, in the case of double-sided printing on thick paper, since the rigidity of the paper is high, the rigidity is further increased in conjunction with the decrease in moisture, and the paper is mechanically strongly contacted with the photoreceptor, and the background stain is easily generated.

Of course, if the paper is humidified before the back side printing is performed, the same level of printing as the back side can be obtained, but the apparatus becomes complicated.

The presence of the opposite polarity developer not only causes background stains, but also uniformly adheres to the non-image area of the photoconductor as described above, so that even if it is not transferred to paper, wasteful toner consumption occurs. As toner consumption increases and remains on the photoreceptor after transfer and is collected by the cleaning device, wear of the cleaning blade is promoted, leading to a number of disadvantages such as deterioration of cleaning performance and shortening of the life of the cleaning device. It is.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems caused by the fact that a developer having a polarity opposite to the original polarity is mixed in a developer. It is an object of the present invention to provide a developing device that does not contain a reverse polarity developer.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a reverse polarity developer adsorption device that adsorbs a developer inside a developing device charged to a polarity opposite to the original charging polarity, and this adsorption device is provided. And a friction member attached to the toner cartridge at a position in contact with the endless belt at the operation position so as to be pivotally provided on the toner cartridge at an operation position in contact with the toner in the developing device. .

By providing the opposite polarity developer attracting device in the developing device as described above, almost no developer charged to the opposite polarity is contained in the developer supplied to the photosensitive member by the developing roller.

As a result, it is possible to solve the problems such as background contamination due to the mixture of the opposite polarity charged developer, an increase in the consumption of the developer, and a reduction in the life of the cleaning device.

Embodiment An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a view showing an embodiment in which the present invention is applied to a developing device using a one-component developer.

The developing device 1 includes a developing device housing 3 having an opening at a portion facing the photosensitive drum 2, a developing roller 4 provided therein in contact with the photosensitive drum 2 through the opening, and a developing device housing 3. One-component developer (toner) 5
A toner supply roller 6 provided at the bottom of the developing device, an agitator 7 for stirring toner stored in the developing device, and a toner replenishing roller 6 In order to regulate the layer thickness of the supplied toner that is adhered and conveyed, it is constituted by a doctor blade 8 attached to the housing so that the leading end thereof resiliently contacts the developing roller.

An opening for toner replenishment is provided in the upper part of the developing device housing 3, and the toner cartridge 10 is mounted on the opening, and a sealing material covering the opening of the toner cartridge is provided.
By pulling out 11, the toner in the toner cartridge 10 falls into the developing device at once and is supplied.

The configuration of the developing device described so far is not particularly different from the conventional one.

However, in the developing device of this embodiment, the opposite polarity (in this case, (+) polarity) toner suction device 12 is provided in the toner cartridge 10 in accordance with the present invention.

This device is provided on the side close to the developing roller 4 when the toner cartridge 10 is mounted on the developing device, and is fixed to an endless belt 15 wound around a pair of rollers 13 and 14, and to the inner surface of the housing of the toner cartridge. Belt 15
Friction member that contacts the belt over its entire width in use
16 is comprised. When the toner cartridge 10 is not mounted, the roller 14 and the belt 15 rotate in a direction indicated by an arrow A from a predetermined position as shown by a chain line in the drawing, and are housed inside the sealant 11 of the toner cartridge 10. Yes,
When the sealing material 11 is pulled out, it rotates in the direction opposite to the arrow A by the force of a spring (not shown), and comes into contact with a stopper (not shown) to be positioned at the use position shown by a solid line in the figure and held at this position. . At this position, the end of the belt 11 wound around the roller 14 contacts the toner around the developing roller 4, and the belt 15 slides on the friction member 16 over the entire width between the rollers 13 and 14. The roller 13 can be driven to rotate by a drive transmission system (not shown) with the developing device mounted at a predetermined position, and the belt 15 rotates in the direction of arrow B during development. When the belt 15 rotates, the belt 15
And the belt 15 is charged to (−). The material of the belt 15 and the friction member 16 is selected such that the belt 15 and the friction member 16 are charged to the (-) polarity when they are rubbed. On the other hand, the toner includes a developing roller 4, a toner replenishing roller 6, a doctor blade 8
For the most part, (−) charge is caused by the friction between them. However, it is inevitable that a part of the toner is charged to (+) due to the problem of the composition of the toner. However, as described above, the (−) charged belt 15 rotates while contacting the toner around the developing roller.
The toner is electrostatically attracted to the belt 15 and is carried by the belt 15, and is stopped by the friction member 16 and accumulates thereon. The accumulated waste toner is discarded together with the used cartridge when the toner cartridge is replaced.

In the above embodiment, the (+) toner suction device is provided on the toner cartridge side and is disposed together with the cartridge. However, the main part of the suction device is installed on the developing device side, and only the collected toner collects on the cartridge side. It may be configured as follows. This will reduce the cost of consumables. However, it is indispensable to reduce the deterioration over time of the charging characteristics of the belt.

Further, since the frictional charging of the toner is also performed at the contact portion of the doctor blade 8, in order to complete the effect of removing the (+) charged toner, the (+) toner adsorbing device must be connected to the downstream side of the doctor blade, for example. It is desirable to provide it near the portion C shown in FIG.

As described above, according to the present invention, since the toner charged to the opposite polarity is removed from the toner supplied to the photoconductor by the developing roller of the developing device, the opposite polarity toner is applied to the non-image portion of the photoconductor. Various problems such as background contamination, wasteful use of toner, and shortened life of the cleaning device due to the adhesion can be solved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a curve diagram qualitatively showing an example of the polarity and charge amount distribution of toner. DESCRIPTION OF SYMBOLS 1 ... Developing device 2 ... Photoconductor 4 ... Developing roller 5 ... Toner (developer) 10 ... Toner cartridge 12 ... Reverse polarity developer adsorption device 15 ... Belt 16 ... Friction member

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Claims (1)

(57) [Claims] An electrostatic latent image on a photosensitive member is developed by contacting or approaching the photosensitive member with a developer, wherein the developer is triboelectrically charged in a developing device, the developer is held in a layered form on a developing roller surface and transported. And
In the developing device in which the toner cartridge is detachably mounted on the upper part of the developing device, a reverse polarity developer absorbing device is provided for absorbing the developer inside the developing device charged to the polarity opposite to the original charging polarity. An endless belt rotatably provided in the toner cartridge at an operation position in contact with the toner in the developing device, and a friction member attached to the toner cartridge at a position in contact with the endless belt at the operation position. Developing device.