JPS5870252A - Developing device - Google Patents

Abstract

PURPOSE:To eliminate the need for light sources for destaticizing by providing the 2nd developer carrying body for receiving the developer in proximity to a developer carrying body for the purpose of developing latent images, and shifting the developer to the 2nd developer carrying body only when said body faces the non-picture parts of an image carrying body by a control means. CONSTITUTION:AC voltage is applied to the 1st sleeve 2 by an electric power source 7, and further about 100V DC component is superposed thereon. The 2nd sleeve 9 is kept 0V when a photosensitive drum 1 is in a picture area, and when a drum is in a non-picture area, higher voltage than the potential in the dark part of the drum 1 is applied to said sleeve. The timings for application of said voltage are controlled by a sequence controller 13. By this method, the toner on the sleeve 2 facing the drum 1 when said drum comes to a non-picture area is held stuck on the sleeve 9 and is not developed even when the drum 1 is at the potential in the dark part. The toner stuck on the sleeve 9 is scraped off by a rubber blade 12 which is held in press contact with the sleeve 9, and the scraped toner is contained in a hopper 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for developing a latent image on a latent image carrier such as a photoreceptor that is used repeatedly, and particularly to a device for developing a latent image that does not consume unnecessary developing toner.

In conventional electrophotographic devices, a corona discharger is provided along the moving path of a cylindrical or belt-shaped photoreceptor.
Charge the photoreceptor and imagewise expose it to form an electrostatic latent image,
Generally, a developing toner is applied and the image is transferred to a transfer paper such as paper.

In such a device, the corona discharger remains in a well-charged operating state while the sensing body is moving, so the potential of the area on the surface of the photoreceptor where no image exposure is made is in a dark state, and unnecessary toner is removed. In order to prevent such a situation, conventional electrophotographic equipment removes non-image areas that are not exposed to light. a static elimination light source is provided between the charging section and the exposure section, and lighting of the static elimination light source corresponds to relative movement of a single area where an electrostatic latent image is formed and a non-image area of the photoreceptor; By electrically controlling turning off the light, or by providing a mechanical shutter between the static elimination light source and the surface of the photoreceptor and mechanically controlling the opening and closing of the shutter, the charges accumulated in the non-image area can be reduced. The static electricity is removed.

However, in these devices, when the light source is turned on and off electrically, the so-called rise of the light source,
With rounding, which always requires a certain amount of time for the fall, and with the speeding up of electronic zeroing devices in recent years, the problem of not being able to completely eliminate the charge accumulated in the non-image area has become a serious problem. In addition, if the shutter is opened and closed mechanically, it not only inevitably becomes mechanically complicated but also generates noise. It is divided into several parts depending on the size, and when printing on a paper size smaller than the maximum paper size, it also serves as ii*exposure and 4 exposure for static elimination (so-called black erasure) that exposes the non-image area at the same time. This exposure requires sharpness at the boundary between exposed and non-exposed areas, and conventionally, a small lamp and a slit are used together.

Due to the above-mentioned requirements, this blackout lamp must be a point light source with a small temperature rise, but as copying machines have become faster in recent years, the amount of exposure has become insufficient and it has become impossible to achieve the purpose. be.

The present invention has been made in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a developing device that has no time delay, does not generate noise, does not require a light source for static elimination, and can simplify the device. That is.

The present invention will be explained in detail below. FIG. 1 is a front view of a conventional developing device.

Reference numeral 1 denotes an electrostatic image carrier having a electrostatic latent image obtained by a known electrophotographic method;
This is a developing sleeve as a non-magnetic developer carrier having a fixed magnet roll 3 inside. In the developing part, a magnetic pole (e.g., 8. pole, 650 Gauss as shown in the figure) is disposed inside the developing sleeve 2 facing the electrostatic image holder 1, and the distance between the developing sleeve 2 and the electrostatic health support member l is It is maintained at 300 μm. A blade 4 is made of a magnetic material and regulates the magnetic developer 6 in the hopper 5 to a desired thickness. One magnetic pole (for example, N1 pole, 850 Gauss in the illustrated example) of the magnet roll 3 is disposed inside the 3JII sleeve 2, facing the blade 4 made of this magnetic pole body.

In this case, the distance between the developing sleeve 2 and the blade 4 made of magnetic material is set to 250 swall C, and the magnetic developer 60 of the developing sleeve as a developer carrier is caused by the magnetic field between the blade 4 made of magnetic material and the developing sleeve 2. The direction of rotation of the tube sleeve 140 that regulates the thickness of the layer is the same as the direction of the sensory drum 1 as shown by the arrow. 7 out of 5 figures
is an alternating bias power supply which forms an alternating electric field in the gap between the photosensitive drum 1 and the surface of the toner layer on the sleeve 2. Also, 8 is the scraper blade.
The toner 6 inside adheres to the sleeve 2, its coat thickness is limited by the blade 4, and when it faces the photosensitive drum IK, it is transferred to the photosensitive drum according to the potential on the photosensitive drum.

Since all the dark areas on the photosensitive drum are developed,
The conventional method is to set the area of the photoreceptor other than the area to which the original is exposed to a bright area potential using a light source for neutralization, and then make the area face the developing sleeve. However, as mentioned above, this conventional method is becoming increasingly imperfect as copying machines have become faster in recent years.

FIG. 2 is a schematic sectional view of the current device of the <3j1m apparatus based on the present invention, and FIG. 3 is a schematic front view of the sleeve viewed from the photosensitive drum side. In the figure, the same members as in FIG. 1 are given the same reference numerals. The toner is restricted to an appropriate amount by the blade 4 on the first developer sleeve 2. The toner receiver of 2 has a sleeve 9 (with a magnet inside) 10 for defeating the toner.
After confronting the photosensitive drum IK.

The gap between the second sleeve 9 and the first sleeve 2 is slightly smaller than the gap between the first sleeve 2 and the photosensitive drum l. Second sleeve 9Fi As shown in Figure 3, there are several crabs depending on the paper size, here 9a and 9b.
A method of using the developing device according to the present invention having a configuration of 0 or more, which is divided into two parts, each electrically insulated by a spacer 11, will be described below. An alternating current voltage is applied to the first sleeve 2 by a power source 7, and the voltage may be 0 or only alternating current, which is synergized with the direct current component of the 100V front bale. When the photosensitive drum 1 is in the image area, a voltage of 0 is applied to the second sleeve 9, and a voltage higher than the dark area potential (for example, +500 V) of the photosensitive drum 1 is applied when the photosensitive drum 1 is in the non-1IIR area. The timing of applying this voltage is such that the non-image area of the photosensitive drum 1 is at the second position facing the first sleeve 2.
It is controlled by the sequence controller 13 so as to set the time to the position facing the sleeve 9.

By this method, when the photosensitive drum becomes a non-image area, the toner on the opposing first sleeve 2 adheres to the second sleeve 9, and is not developed even if the photosensitive drum 1 has a dark potential.

The toner adhering to the second sleeve 9 is scraped off by a rubber blade 12 pressed against the second sleeve, stored in the hopper 5 again, and reused as toner.

When paper other than the maximum paper size is used, the toner in the excess size is divided and collected onto the second sleeve by applying a voltage only to the small part 9b of the second sleeve. It does not appear as a black mark on the photosensitive drum, and serves as a so-called black eraser.

The developing device of the present invention as described above enables non-developing of non-image areas without time delay and mechanical noise even in high-speed copying machines. In this way, a light source for so-called blank exposure is no longer necessary, so that the power consumption of approximately 20 W or more is reduced and the temperature increase caused by the lamp is also eliminated. Further, unnecessary consumption of toner is eliminated, thereby significantly reducing the burden on the residual toner cleaning device.

[Embodiment 1] A developing device based on the present invention was applied to a copying machine with a process speed, that is, a circumferential speed of the photosensitive drum 1 of 300 mm. The diameter of the assembled sleeve 2 is 39I111. Diameter of second sleeve 9: 26 m1
The distance between the first sleeve and the photosensitive drum is 300 mm.
The latent image was set so that the potential of the dark area of the sleeve 2 and the second sliver body was +500v%, and the potential of the bright area was 0. An AC voltage of 400 Hz% 800 Vp-p was applied to the first sleeve 2, and +150 V was superimposed as a DC component. A DC voltage of +600V with timing controlled by the sequence controller 13 is applied to the second sleeve 9. Photosensitive drum 1, 1st
Sleeve 2, second sleeve 9 The electrophotographic electrostatic latent image was developed and transferred at the same dust speed, and the dark area ms density was 1.2.
Meibu painting g! ! The density was 0.07, and the density on the photoreceptor in the non-image area was 0.08.

[Example 2] The existing device of Example 1 was applied to an electrophotographic copying machine with a process speaker of 400 m. 1st sleeve 2Kti100
A 0 Hz, 1200 Vp-po AC voltage was applied, and a DC positive voltage +1 ooV was superimposed. Other points were the same as in Example 1, and similar results were obtained. Further, when using small size paper, the excess portion of the photoreceptor was not developed.

[Brief explanation of the drawing]

1Ii1 is a sectional view showing a conventional sleeve-type developer, FIG. 2 is a schematic sectional view of a developing device based on the present invention, and FIG. 3 is a schematic front view of the sleeve as viewed from the photoreceptor side. In the figure, L: photosensitive drum, 2: developing sleeve, 3:
・Magnetic roller, 4...Magnetic blade, 5...
- Hopper, 6 - toner, 7 - alternating bias power supply, 9 - toner receiver, IJ-tub for taking, lO - magnet, 11 spacer, 13 - sequence controller. Applicant Canon Co., Ltd.

Claims (2)

[Claims] (1) A second developer carrier for removing the amount of developer is provided in close proximity to the first developer carrier for developing the latent image on the latent image carrier, and A control means for transferring the developer from the carrier to the second developer carrier transfers the developer to the second developer carrier only when corresponding to a non-image area of the image carrier, and retains the latent image. 1. A developing device characterized in that K is configured to suppress development of non-image areas on a body. (2) The developing device according to claim 1, wherein the second developer carrier is divided into a plurality of parts in the longitudinal direction, and each part is electrically insulated.