JPH02238478A - developing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device capable of forming an image using toner. [Prior Art] In recent years, electrophotographic technology that forms images using toner has been widely used in copying machines. It is applied to printers. In order to achieve high image quality, it is necessary to eliminate unevenness in color saturation, eliminate background fog, and reduce toner scattering. Many methods have been proposed for these problems. For example, JP-A-63-
No. 96678 discloses a method for eliminating ghosts by removing unnecessary toner, a method for preventing toner scattering when toner is removed, and a method for uniformly distributing toner on a developing sleeve that faces a latent image carrier and supplies toner to the latent image carrier. A structure for adding even more thickness has also been proposed. [Problems to be Solved by the Invention] However, with conventional developing devices, it is insufficient to improve the quality of images and to control the toner charge amount, which is the fundamental cause of toner scattering, and the density caused by variations in the charge amount is insufficient. Deterioration, increase in fog, etc. are unavoidable. In addition, no effective method has been found to prevent toner scattering during development due to a decrease in the amount of charge on the toner, and there have been problems such as image unevenness due to the charge on the photoreceptor and staining of the optical system. SUMMARY OF THE INVENTION Therefore, the present invention aims to solve such problems, and its purpose is to ensure that the developing sleeve always supplies toner with a uniform charge amount to the latent image carrier, thereby preventing uneven development, background fogging, and toner scattering. The objective is to provide a developing device that can form high-quality images. [Means for Solving the Problems] The developing device of the present invention includes a developing sleeve that is disposed adjacent to a latent image carrier that forms an electrostatic latent image and that conveys toner that is an image forming body, A developing device that electrostatically attaches toner on a developing sleeve to a latent image carrier to visualize an electrostatic latent image includes a toner charging means for charging the toner, and a charged toner conveyor adjacent to the developing sleeve. The present invention is characterized in that a voltage applying means for applying a voltage between the developing sleeve and the charged toner conveying means is provided.

Further, the developing device of the present invention is characterized in that the voltage applied by the voltage applying means for applying voltage between the developing sleeve and the charged toner conveying means is made variable. Further, the developing device of the present invention is characterized in that the circumferential speed of the charged toner conveying means or the circumferential speed of the developing sleeve is made variable. Further, the developing device of the present invention is characterized in that a toner scraping plate is provided which slides into contact with the charged toner conveying means and scrapes off the charged toner. [Function] According to the above configuration of the present invention, the toner charged by the toner charging means for charging the toner is transported to a location facing the developing sleeve by the charged toner transporting means. Here, the amount of toner to be charged by the toner charging means and conveyed by the charged toner conveying means is specified. A voltage is applied between the charged toner and the developing sleeve, and an electric field is formed between them. When the charged toner that has been transported is placed in an electric field, a force is exerted to draw it toward the developing sleeve. Here, toner particles with an electrical charge of more than a certain value are attracted toward the developing sleeve, and those with an electrical charge less than a certain value remain on the charged toner conveyor or are scattered. As a result, only toner with a certain amount of charge or more adheres to the developing sleeve. The toner adhering to the developing sleeve is conveyed by the developing sleeve to a location facing the latent image carrier. Between the developing sleeve and the latent image carrier,
An electrostatic force acts, and all the toner adheres to the latent image carrier, making the electrostatic latent image visible.

As a result of the above, toner with a constant charge amount is stably supplied during development between the developing sleeve and the latent image carrier, and development is performed stably, eliminating image unevenness, background fogging, and toner scattering, resulting in high quality. Images can be realized. In addition, by changing the voltage applied between the charged toner conveyor and the developing sleeve, it is possible to adjust the environment such as humidity and temperature, which have a large effect on development. Alternatively, even if the charging characteristics of the toner or the distance between the charged toner carrier and the developing sleeve change, toner with a certain charging value or higher can be attached to the developing sleeve by changing the applied voltage. As a result, the development of the latent image with toner between the developing sleeve and the latent image carrier is in the same state, and the developed image is stable under any circumstances, with no image unevenness, background fog, toner scattering, etc. It is possible to achieve high quality images without any problems.

In addition, by changing the circumferential speed of the charged toner conveyor or the circumferential speed of the developing sleeve, the amount of toner that has a certain charge value or more that is supplied onto the developing sleeve is controlled, and the amount of toner that adheres to the developing sleeve is controlled. The amount can be kept constant. This makes the amount of toner supplied to the latent image carrier constant and eliminates image unevenness. Ground cover. High-quality images can be achieved without toner scattering. In addition, by providing a toner scraping plate that comes into sliding contact with the charged toner conveying means and scrapes off the charged toner, the toner remaining on the charged toner conveying body with an amount of charge smaller than a certain value is removed and the toner is removed from the charged toner conveying body. This prevents the formation of a thin layer of toner with a small amount of charge, making it easier to charge the toner, and stably supplying toner with a certain charge value or higher. This stabilizes the amount of toner supplied to the latent image carrier and reduces image unevenness and background fog. High-quality images can be achieved without toner scattering. Hereinafter, the present invention will be explained in detail with reference to Examples. [Example] FIG. 1 is an example of the present invention, and is a schematic sectional view of a developing device of the present invention. The latent image carrier 1 has a photosensitive film 2 having photoconductivity coated on a conductive support portion 3. After the photoresist film 2 is charged to a predetermined potential using a charger 13, the light emitted from a light source 14 such as a laser is scanned using a rotating polygon mirror (not shown), and an optical system 15
An electrostatic latent image is formed on the latent image carrier 1 by forming an image on the photoresist film 2 to obtain a potential contrast. On the other hand, the developing device 12 mainly includes a toner charging means 7 that charges toner 9 as an image forming body, a charged toner conveying means 5 that conveys the toner, and a developing sleeve 4 that conveys the toner to a position facing the latent image carrier 1. It is composed of. Support part 3 and developing sleeve 4
By applying a voltage between the developing bias applying means 11 and the developing electric field according to the potential contrast of the electrostatic latent image on the latent image carrier 1, a location facing the latent image carrier 1 (development gap) is generated. The charged toner 9 that has been carried up to this point is flown towards the electrostatic latent image on the latent image carrier 1 to obtain a toner adhesion amount according to the potential contrast and visualize the latent image. The present invention is based on this. The developing device mainly relates to the developing device 12, and will be explained in more detail based on an embodiment. A developing device 12 is filled with toner 9. In the present invention, an example using magnetic toner will be shown. Charged toner conveying means 5
has a cylindrical shape, and inside the cylinder there are arranged multi-pole magnetized cylindrical magnetic rollers 6, each of which rotates. Due to these rotations, the magnetic toner moves in the same direction (clockwise) as the charged toner transport means.
Here, the rotation direction of the magnetic roller and the toner charging means does not define the essence of the present invention, depending on the type of toner used. The toner charging means 7 consists of blades arranged in a wedge-like manner so that the gap becomes narrower in the toner conveying direction. Toner 9 and charged toner conveying means 5
Friction is caused between the toner charging means 7 and the toner charging means 7, and the toner 9 is charged by a series of charges on the substance caused by the friction. In the case of the present invention, the charged toner conveying means 5 is made of aluminum. It is a metal such as iron, and when it rubs against the toner 9, the toner 9 becomes negatively charged. The toner charging means generates friction between the toner, the charged toner conveying means, and the toner charging means, and at the same time, the blade is arranged in a wedge shape to regulate the amount of toner conveyed to a position facing the developing sleeve. ．． Here, a friction method was used to charge the toner 9, but other methods may also be used, such as the method proposed by the present applicant in Japanese Patent Application No. 1983-91000. The charged toner 9 is conveyed to a position facing the developing sleeve 4 by the charged toner conveying means 5.

A voltage is applied between the charged toner conveying means 5 and the developing sleeve 4 by a voltage applying means 10 to generate an electric field. The toner 9 charged by the generated electric field is caused to fly from the charged toner conveying means 5 to the developing sleeve 4, and the toner 9 is supplied to the developing sleeve 4. Here, the amount of charge of the toner flying onto the developing sleeve 4 is greater than a certain value, and those whose amount of charge is less than a certain value remain on the charged toner conveying means 5 or scatter during flight. In this process, the toner regulated by the toner charging means is being transported to the location where the charged toner transporting means and the developing sleeve face each other. The amount was small. According to Figure 2,
The above process will be explained in more detail. FIG. 2 is a diagram showing the relationship between the toner charge amount and the distribution number. The amount of charge of the toner charged by the toner charging means 7 and the distribution number have a relationship shown by a distribution curve 21. Charged toner conveying means 5
After the above process of causing the toner 9 to fly between the developing sleeve 4 and the developing sleeve 4, only the toner having a larger charge amount than the line 22 (the shaded area in FIG. 2) adheres to the developing sleeve 4. ．． As a result, only toner having a charge amount equal to or higher than a certain value exists on the developing sleeve 4. The rotation of the developing sleeve 4 transports the toner 9 to a position facing the latent image carrier 1 . A voltage is applied between the developing sleeve 4 and the latent image carrier 1 by a developing bias applying means 11 to generate an electric field. The toner 9 charged by the generated electric field is flown from the developing sleeve 4 to the latent image carrier 1 to visualize the latent image. Here, the electric field intensity generated by the developing bias applying means 11 is made stronger than the electric field intensity generated by the voltage applying means 10. By setting the voltage in this way, between the developing sleeve 4 and the latent image carrier 1,
Toner having a charge amount equal to or higher than line 23 in FIG. 2 can fly to the latent image carrier. The amount of charge of the toner on the developing sleeve 4 is above the line 22, and all of the toner 9 supplied onto the developing sleeve 4 flies to the latent image carrier 1. For example, in this embodiment, the potential of the latent image carrier is set to O■, the developing sleeve 4 is set to a potential of -500V by the developing bias applying means 11, and the charged toner conveying means 5 is set by the voltage applying means 10.
The potential of the charged toner conveying means 5 was set to -900V so that the potential difference between the developing sleeve 4 and the developing sleeve 4 was -400V. Further, the voltage of the voltage applying means 10 that applies a voltage between the charged toner conveying means 5 and the developing sleeve 4 is made variable.
In this embodiment, the gap between the charged toner conveying means 5 and the developing sleeve 4 is set to 200 μm, and the applied voltage is changed depending on the value of this gap. Toner having the same amount of charge could always be supplied to the developing sleeve 4 regardless of the value of the blob. Additionally, charging characteristics vary depending on the type of toner.
Even when the same toner charging means 7 is used, the amount of charge may be different. Even in this case, by making the voltage of the voltage applying means 10 variable, toner having the same amount of charge can be supplied to the developing sleeve 4. Further, even if the same gap and the same toner are used, the amount of toner charge will change as the humidity changes, but by making the voltage of the voltage applying means 10 variable, it was possible to supply toner with the same amount of charge to the developing sleeve 4. Furthermore, the peripheral speed of the charged toner conveying means 5 or the developing sleeve 4 can be changed. The peripheral speed of the developing sleeve 4 is related to the peripheral speed of the latent image carrier 1, and the peripheral speed of the latent image carrier 1 is determined by the developing speed. Once the specifications of the developing device are determined, the circumferential speed of the developing sleeve 4 is also determined.
In order to perform high-quality development, the amount of toner supplied must be appropriate, and in order to keep the amount of toner supplied to the developing sleeve 4 constant, the peripheral speed of the charged toner conveying means relative to the developing sleeve 4 is adjusted. As a result, even if the developing speed of the developing device was changed, a constant amount of toner could be supplied to the latent image carrier l, and a high-quality image could be visualized. Further, a toner scraping plate 8 that slides into contact with the charged toner conveying means 5 is provided. Developing sleeve 4 and charged toner conveying means 5
During the toner flight process in the opposing gap, toner with a charge amount below a certain value remains on the surface of the charged toner conveying means 5. If this toner remains, a thin film of toner with a small amount of charge is formed on the surface of the charged toner conveying means 5. This thin film makes it difficult for uncharged toner to rub against the surface of the charged toner conveying means 5, making it difficult for the toner to be charged during the toner charging process. By attaching the toner scraping plate 8, this film can be prevented from forming.
Toner charging operation can be performed reliably. Although the embodiments have been described above, the present invention can be applied not only to the above embodiments but also to a wide range of image forming apparatuses as developing devices such as electrophotographic recording devices, and in particular to copying machines that record pictures, photographs, etc. It is effective if applied to an image forming apparatus using a developer, such as a printer or a page printer.

[Effects of the Invention] As described above, according to the present invention, toner flight from the charged toner transport means to the developing sleeve is stabilized by regulation of the charged toner transport mechanism of the toner charging means, and the amount of charge on the developing sleeve is reduced. It can supply stable toner and reliably fly the toner onto the latent image carrier, making it possible to achieve high-quality images without background fog or uneven development. In addition, in the process of attaching toner to the latent image carrier, the toner on the developing sleeve can be attached to the latent image carrier without scattering, so that other devices near the developing unit can be used without toner scattering. It is no longer dirty. When scattered toner adheres to a charger, etc., it causes uneven charging and transfer of the latent image carrier, as well as background fog due to dirt in the optical system, but with the present invention, toner scattering has been eliminated and high-quality image development has been realized. did it. As described above, the present invention has provided a developing device that can perform high-quality image development.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of the developing device of the present invention. Figure 2 shows
FIG. 3 is a diagram showing the relationship between the toner charge index and the distribution number in the developing device of the present invention. 1 ... Latent image carrier 4 ... Developing sleeve 5 ... Charged toner conveying means 6 ... Magnetic roller 7 ... Toner charging means 8 ... Toner scraping plate 9 ... Toner 10 ... Voltage application means 11 ... Development bias application means 12 ...
Applicant for developing device or above Se. Iko Epson Co., Ltd. Agent Patent Attorney Kisaburo Suzuki (and 1 other person) 231! Figure 1 Figure 2

Claims (4)

[Claims] (1) A developing sleeve is disposed adjacent to a latent image carrier that forms an electrostatic latent image and conveys toner as an image forming body, and the toner on the developing sleeve is electrostatically transferred to the latent image carrier. In a developing device that visualizes the electrostatic latent image by adhering it to an image bearing member, a toner charging means for charging the toner, a charged toner conveying means adjacent to the developing sleeve, and a toner comprising: the developing sleeve and the toner; A developing device comprising a voltage applying means for applying a voltage between charged toner conveying means. (2) The developing device according to claim 1, wherein the voltage applied by the voltage applying means for applying a voltage between the developing sleeve and the charged toner conveying means is variable. (3) The developing device according to claim 1, wherein the peripheral speed of the charged toner conveying means or the peripheral speed of the developing sleeve is made variable. (4) The developing device according to claim 1, further comprising a toner scraping plate that comes into sliding contact with the charged toner conveying means and scrapes off the charged toner.