JPH01233467A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a copy image with good reproducibility according to an original by adjusting the rotating speed of a sleeve according to the picture quality of the original. CONSTITUTION:A photosensitive body 10 is slid on a magnetic brush formed on the sleeve 13 which rotates around a magnet roller 12 and a driving device 14 which rotates the sleeve 13 has a main driving belt 21 extended between the driving pulley 16 of a main motor 17 having two high and low stages of rotating speeds and the 1st gear 18a of a developing device driving gear 18. Consequently, the rotating speeds of the sleeve 13 are switched to easily obtain desired picture quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement in a developing device for developing an electrostatic latent image using a magnetic brush in an image forming apparatus.

(Prior Art) In an image forming apparatus such as a copying machine, a sleeve surrounding a magnet roll is rotated to develop an electrostatic latent image on a photoreceptor, which is an image bearing member, and a magnetic brush is formed around the sleeve. However, magnetic brush developing devices in which this magnetic brush is brought into sliding contact with an electrostatic latent image are in widespread use. On the other hand, in recent years, image forming apparatuses have been made faster. If you try to use the magnetic brush developing device used in conventional models as is, the number of rotations of the sleeve is set at a fixed number, and the image quality characteristics of the magnetic brush will be constant. There is a problem in that an original image with a large amount of opacity may be blurred, and on the other hand, an original image with halftones may have a reduced reproducibility of density changes.

(Problem to be solved by the invention) Conventionally, since the number of rotations of the sleeve is specified, it is not possible to obtain a copy image of appropriate image quality according to the original image, especially in high-speed models, and the image quality deteriorates. It has the following drawbacks.

Therefore, the present invention aims to eliminate the above-mentioned drawbacks, and provides a developing device that can obtain good images by increasing the contrast depending on the original striped image, or conversely by increasing the reproducibility of halftones. With the goal.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a drive device that changes the number of rotations of the sleeve depending on the document image.

(Function) The present invention aims to obtain a good copy image by easily obtaining different image qualities such as clear contrast or halftone by using the above-mentioned means.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2. Main unit (9) with copy speed 40 (sheets/min)
) A developing device (11) is installed at the developing position of the photoreceptor (10), which is an image carrier. and photoreceptor (10)
is capable of sliding contact with a magnetic brush (not shown) formed on a sleeve (13) rotating around a magnet roller (12). On the other hand (14) is a drive device that rotates the sleeve (13), and the drive pulley (16) of the motor (17) has two levels of rotation speed: high speed and low speed.
, and the first gear (18) of the developer drive gear (18).
a) A main drive belt (21) is passed between them. Furthermore, the sleeve drive gear (20) attached to the shaft (13a) of the sleeve (13) meshes with the second gear (18b). Also, (22) is the main body (
9) Provided on the top control panel (23),
Selection button (24) for switching the rotation speed of the motor (17)
) is the manuscript.

However, when copying, the motor (17) is usually automatically set to high speed rotation, so if the content of the original (24) has many characters or solid black areas, , the operator starts copying without operating the selection button (22). As a result, the photoreceptor (10) and other image forming devices (not shown) are moved, and
In the space movement device (14), a motor (17) is rotated at high speed. This rotation is caused by the drive pulley (17a),
Main drive belt (21), first gear (18a)
, the sleeve drive gear (2) via the second gear (18).
0) and rotates the sleeve (13) at a high speed of 300 [times/min] via the shaft (13a). As the sleeve (13) rotates at high speed, a high-density magnetic brush (not shown) is formed around the sleeve (13), and by sliding contact with this magnetic brush, an electrostatic latent image is formed through a charging process and an exposure process. The photoreceptor (10) thus processed is then developed. Thereafter, the toner image is transferred to a sheet of paper (not shown) by a transfer device (not shown), and the sheet paper is ejected through a fixing device to complete a copy image, while the photoreceptor (10) is removed by one (not shown). The next copy is made possible after passing through a cleaning device and a static eliminator. After repeating such copying operations and obtaining the required number of copies, if the content of the next new document (24) is a photograph or the like and includes halftones, the operator presses the selection button (22). After switching the motor (17) from high-speed rotation to low-speed rotation, copying is started. This allows the sleeve (
13) is rotated by the drive device (14) at a low speed of 200 [times/min], and a magnetic brush (not shown) is formed around it, but the density of the magnetic brush at this time is compared to high-speed rotation. and is reduced. In this state, the electrostatic latent image on the photoreceptor (10) is developed in the same way as when rotating at high speed, and then a copy image is completed through the transfer and fixing steps. 10) is also made ready for the next copy after each process of cleaning and neutralization, and by repeating this process, the required copy can be obtained.

As a result, the copy image obtained by rotating the sleeve (13) at high speed had strong contrast, clear characters and lines, high image density, and was clearly reproduced without blurring in solid areas. On the other hand, in the copy image obtained by rotating the sleeve (13) at low speed, the reproducibility of the halftone part is high, the photograph is clearly reproduced without unevenness, and the resolution is good and fine lines are also eliminated. Because it can be expressed, even if you use the copied item as the original for the next copy, the lines will not smudge or the characters will be blurred, and you can make more copies from the copied original. A clear image was also obtained.

With this configuration, desired image quality can be easily obtained by switching the rotation speed of the sleeve (13).
For originals with a lot of text and solid areas, you can obtain clear copies without blurring, while for originals with halftones such as photographs, the images can be reproduced without unevenness. This makes it possible to obtain copies with good quality, and the image quality is significantly improved compared to the conventional method.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be modified in various ways, and, for example, the copy speed of the main body is not limited, and may be faster. Also, the number of rotations of the sleeve is not limited, and in high-speed rotation it is approximately 300 [times/minute] to 4
The rotation speed may be approximately 0.00 times/minute, or approximately 200 times/minute to 250 times/minute for low speed rotation. Furthermore, the number of rotations of the sleeve may not be changed in two steps, but may be changed in multiple steps, so that an image quality more suitable for the document can be selected. On the other hand, the structure of the drive device may be arbitrary, and the rotation speed of the motor may be constant, and the rotation speed of the sleeve may be changed by providing a multi-stage gear in the middle and switching the multi-stage gear that meshes with the sleeve drive gear. .

〔Effect of the invention〕

As explained above, according to the present invention, by adjusting the rotation speed of the sleeve according to the image quality of the original, it is possible to obtain a copy image with good reproducibility according to the original, and the copy speed is increased. However, while it is possible to obtain clear images with high contrast for manuscripts with a lot of text,
For original documents containing photographs, etc., halftone reproduction is good, and even when copies are repeated, lines do not smear or characters become blurred, making it possible to improve the image quality. Furthermore, if the rotation speed of the sleeve can be changed with one touch using the selection button on the control panel as in the embodiment, the operability during copying will not be impaired.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 being a schematic side view thereof, and FIG. 2 being a schematic perspective view of its main body.

Claims (1)

[Claims] In an apparatus that performs development by sliding a magnetic brush into contact with an image carrier having an electrostatic latent image, a magnet roll, a sleeve rotatably provided around the magnet roll and supporting the magnetic brush, and a sleeve that is rotated at different times. A developing device characterized by comprising a drive device that rotates by a number of rotations.