JPS59185366A - Developing device of electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To maintain a trimmer gap with high accuracy and to obtain copies with always good image quality by contacting and holding scrapers with/by a photosensitive drum and a tracking roll respectively. CONSTITUTION:The scrapers 3, 4 consisting of elastic bodies are fitted to the photosensitive drum 1 and the tracking roll 2, respectively. The scraper 3 e.g. is obtained by backing a plastic thin plate 31 such as mylar film by a holding member 32 and fixing the thin plate 31 on a copying machine body by using a blacket 33 and a screw 34. Since the scrapers 3, 4 scrape an adhered magnetic developer from the photosensitive drum 1 and the tracking roll 2 in said constitution, the contact surface between the drum 1 and the roll 2 is always kept clean, the trimmer gap is maintained at always high accuracy and copies of good quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improvement in a developing device for an electrophotographic copying machine, particularly in a magnetic brush developing device.

BACKGROUND TECHNOLOGY In general, electrophotographic copying machines using a magnetic development system that use a one-component magnetic developer and a two-component developer consisting of toner and a magnetic carrier use a photosensitive P ram carrying an electrostatic latent image and a magnetic roll. Controlling the gap between the magnetic rollers is extremely important, and the layer thickness of the developer that stands up on the magnetic roll is affected by the size of this gap. The density of the image obtained varies depending on the layer thickness of the spiked developer, and for example, images obtained from line areas, low gradation areas, solid areas, etc. of the document are slightly affected. Generally, the roundness of the photosensitive drum is on the order of 0.1 mm, but the gap must be controlled on the order of 0.01 m. Therefore, in consideration of the precision of photosensitive drum manufacturing, the floating method, which controls the gap between the photosensitive drum and the magnetic roll based on the surface of the drum, has been widely adopted due to its simplicity and ease of maintaining gap accuracy. . In this method, a tracking roll circumscribing the circumferential edge of the photosensitive drum is installed concentrically with the magnetic roll to maintain a predetermined gap (see FIG. 1).

However, the toner cloud 9 generated during the development process,
Due to toner leakage, toner (developer) adheres to the surface of the photosensitive ram and tracking ram, and the gap increases in proportion to the amount of adhesion, increasing the amount of developer spikes and reducing the image quality of the resulting copy. There were five drawbacks:

OBJECTS OF THE INVENTION In order to eliminate the above-mentioned drawbacks of the developing device in a conventional magnetic development type electrophotographic copying machine, the present invention prevents developer from adhering to the photosensitive drum and the tracking roll. Another object of the present invention is to provide a developing device that can constantly keep the surface of a tracking roll clean and provide stable and good image quality.

Structure of the Invention The developing device according to the present invention has a photosensitive drum and a tracking roll provided concentrically with a magnetic roll disposed opposite to the photosensitive drum. It has a structure in which a scraper is applied. The present invention will be described in detail below with reference to the drawings.

In FIG. 1, a magnetic developer (7) is accommodated in a space formed by a magnetic roll (5) and a housing (61).When the magnetic roll (5) rotates in the direction of the arrow, the developer (5) ) is conveyed by a magnetic roll, and the amount of spikes is regulated by a trimmer (8) attached to the 7S housing.
to visualize the electrostatic latent image on the photosensitive drum. At this time, the gap is the difference (r) between the radius (r) of the tracking roll (2), which is attached concentrically to the sides of both rows of the magnetic roll (5), and the radius (r) of the magnetic roll (5).
r□−r2).

According to the present invention, each of the photosensitive drum 9 (1) and the tracking roll (2) is provided with a scraper group made of an elastic material.
+31 and +41 have been applied. These scrapers will be explained with reference to FIG. FIG. 2 is an exploded view of a scraper. For example, the scraper (3) that contacts the photosensitive drum (1) is made of an elastic material, such as a thin plastic plate (31) such as Mylar film, lined with a holding member (32), and further It is fixed to the main body of the copying machine with a bracket (33) and screws (34). In addition, the scrape A-+41 that comes into contact with the tracking roll (2) is made of a similar elastic thin plate (41) lined with a holding member (42) and further fixed to the developing device with a bracket (43) and screws (44). It is something. In addition, scraper #-431
and (4) are installed so as to be in constant contact with both ends of the photosensitive drum 9 and the surface of the tracking roll opposite the ends. Even if magnetic developer adheres to both ends of the photosensitive drum and the surface of the tracking roll during the development operation, the scrapers (3) and (4) scrape off the adhered magnetic developer from the photosensitive drum and the tracking roll, so that both ends are The contact surface is always kept clean, and therefore the trimmer gap is always maintained with high accuracy, resulting in good image quality.

Effects of the Invention According to the developing device of the present invention, the contact portion of the tracking roll and the photosensitive drum 9 with the tracking roll is always kept cleaner than the scraper e-1c, so the trimmer gap can be maintained with high precision. This allows you to always get good quality copies.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a developing device according to the present invention, and Part 2 is an exploded view of a scraper according to the present invention. Symbols in the figure = 1...photosensitive drum, 2...tracking roll. 3.4...Scraper, 5...Magnetic roll. 6...Housing, 7...Magnetic developer. (3 others)

Claims (1)

[Claims] 1. A developing device for a magnetic development type electrophotographic copying machine having a magnetic roll and a tracking roll, characterized in that a scraper is held in contact with the photosensitive P ram and the tracking roll, respectively.