JPH0738925Y2 - Cleaning Magnet Roll for Electrophotographic Equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Utilization of the Invention] The present invention relates to a cleaning magnet roll of an electrophotographic apparatus having a magnetic pole for removing a carrier attached to a photosensitive drum.

[Background of the Invention] In an electrophotographic apparatus using a two-component developer composed of a carrier and a toner, transfer failure may occur due to the carrier attached to the photosensitive drum during development, resulting in partial missing characters or missing characters. Therefore, a cleaning magnet roll having a magnetic pole is widely provided between the developing unit and the transfer unit for the purpose of removing the iron powder carrier attached to the photosensitive drum before the transfer. This cleaning magnet roll has a rotatable sleeve around the outer circumference of a cylindrical magnet having a plurality of magnetic poles, and the magnetic poles facing the photosensitive drum attract the carrier attached to the photosensitive drum to attract it onto the sleeve. The carrier is conveyed by the rotation of. The conveyed carrier is naturally dropped after being deposited on the magnetic pole S ₃ of the cleaning magnet roll by a certain amount.
At this time, some of the carriers deposited on the magnetic pole S ₃ may be transported to the magnetic pole S ₁ without spontaneously dropping. The carrier thus conveyed causes panicles at the magnetic pole N ₁ facing the photosensitive drum, and the carrier comes into contact with the toner image on the photosensitive drum, disturbing the toner image and adversely affecting print quality. Has become.

FIGS. 1 (a) and 1 (b) show the problems of the above-mentioned conventional technique. The problems during carrier transportation will be described with reference to the drawings. Carrier 2 attached to photosensitive drum 1 during development
Are sent as the photosensitive drum 1 rotates. Carrier 2
Is iron, and when the carrier 2 is sent to the cleaning magnet roll 3, the carrier 2 is generated by the magnetic force of the magnetic pole N ₁ of the magnet 3a of the cleaning magnet roll 3.
Is sucked and adsorbed on the sleeve 3b. The sleeve 3b is rotating at a constant rotation speed, and the carrier 2 is generated by the magnetic force of the magnetic pole S ₂ of the magnet 3a provided in the rotation direction of the sleeve 3b.
Is transported. The same action, the carrier 2 adsorbed on the sleeve 3b is transported to the final magnetic pole S ₃ of the magnet 3a, is constrained by the magnetic pole S _3, deposited on ₃ pole S, after a certain amount deposited, the carrier 2a Gradually falls naturally.

In the cleaning magnet roll 3 having such a structure, there is a carrier 2b that rides on the magnetic pole S ₁ without naturally falling on the magnetic pole S ₃ . Carrier 2b riding on this magnetic pole S ₁
Is conveyed to the magnetic pole N ₁ facing the photosensitive drum and forms a carrier spike 2c larger than the cleaning magnet roll-photosensitive drum gap δ on the magnetic pole N ₁ . Therefore, the tip of the bristle carrier 2c comes into contact with the photosensitive drum 1, and the toner image formed on the photosensitive drum 1 is blurred by the bristle carrier 2c, which has a serious adverse effect on print quality. Conventionally, in order for this riding carrier 2b is prevented from being conveyed to the S ₁ pole, the S ₃ pole and S ₁ machining gap, have a plate 4 for carrier scraper taken is configured to contact the sleeve 3b However, in this configuration, the carrier scraping plate 4 and the sleeve 3b are
The carrier 2 is sandwiched between them, and the carrier 2 sleeves.
There is a problem that the carrier 3 is damaged and the transportability of the carrier 2 is deteriorated. Therefore, there is a demand for the development of a cleaning magnet roll that does not cause carriers to climb between the magnetic poles S ₃ and S ₁ .

[Purpose of device]

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to prevent carrier pick-up from the magnetic pole arranged at the position where the recovered carrier falls naturally, to the downstream side in the sleeve rotation direction, and to attach it to the photosensitive drum. It is an object of the present invention to provide a cleaning magnet roll that effectively removes the generated carrier and does not deteriorate the transportability of the carrier on the sleeve.

[Outline of device]

According to the present invention, the magnetic force of the first magnetic pole arranged at a position where the recovered carrier of the cleaning magnet roll naturally falls, and the first magnetic pole and the same magnetic pole as the first magnetic pole, and the first magnetic pole. If the magnetic force of the opposite pole generated between the second magnetic pole and the second magnetic pole arranged at a predetermined angle downstream of the magnetic pole of the second magnetic pole is set to a constant value, the first magnetic pole is moved to the downstream side of the sleeve rotational direction. The relationship between the magnetic pole angle and the magnetic force of the cleaning magnet roll is devised, paying attention to the fact that the carrier does not get on the carrier.

[Example of device]

As a concrete embodiment of the present invention, FIG. 2 shows the entire structure, and FIG. 3 shows its operation.

A cleaning magnet roll 3 is provided between the developing magnet roll 5 and the transfer device 6 facing the photosensitive drum 1 with a gap δ between the cleaning magnet roll 3 and the photosensitive drum 1. A magnet 3a is fixed inside the cleaning magnet roll 3, and a rotatable sleeve 3b is provided around the magnet 3a.
Is provided. The magnet 3a has magnetic poles S ₁ , N ₁ , S ₂ ,
N ₂ and S ₃ are installed at angles of θ ₁ , θ ₂ , θ ₃ , θ ₄ , and θ ₅ , respectively, and the magnet 3a is fixed at a position where the magnetic pole N ₁ faces the photosensitive drum 1. The sleeve 3b is rotated in the same direction as the rotation direction of the photosensitive drum 1 at a constant rotation speed by an appropriate motor or the like.

The operation of removing the carrier 2 attached to the photosensitive drum 1 at the time of development in such a configuration will be described below.

At the time of development, the carrier 2 attached to the photosensitive drum 1 by the developing magnet roll 5 is attracted by the magnetic pole N ₁ of the magnet 3a at the portion facing the cleaning magnet roll 3 and adsorbed on the sleeve 3b. Adsorbed carrier 2
Is conveyed from the pole N ₁ by a suction force of the rotation and the magnetic pole S ₂ of the sleeve 3b, passing through the magnetic pole S _2, N ₂ and is constrained deposited on the end portion magnetic pole S _3, after a certain amount of deposition, gradually Nature To fall. At this time, due to the action as shown in FIG. 3, the carriers deposited on the magnetic pole S ₃ do not ride on the magnetic pole S ₁ .

The operation will be described below.

Figure 3 (a) is an illustration of the field distribution of the conventional products between the magnetic poles S ₃ -S _1, it is between the magnetic poles S ₃ -S _1, reverse polarity n has occurred. Due to the attraction force of the reverse pole n, the carriers 2 deposited on the magnetic pole S ₃ are transported to the reverse pole n and further to the magnetic pole S ₁ . Figure 3 (b) is shows the magnetic field distribution between the magnetic poles S ₃ -S ₁ of the present invention, to reduce the attraction of opposite polarity n by lowering the conventional magnetic forces of opposite polarity n, pole S ₁ It is possible to prevent riding on Although the magnetic force of the opposite pole n, the carrier transportability depends on the circumferential speed of the sleeve. Therefore, according to experiments, the relationship between the magnetic flux density n of the opposite pole, the magnetic flux density S of the magnetic pole S ₃ , and the circumferential speed v of the sleeve is shown. Should satisfy n / Sv ≦ 2.2 (cm / s). Further, FIG. 3 (c) shows the magnetic force distribution between the magnetic poles N _{2 and} S ₁ of the present invention, in which the magnetic flux density of the magnetic pole S ₃ is reduced to about 1/2 of the magnetic flux density of the magnetic pole N _2. Is. By lowering the magnetic force of the magnetic pole S _3, pole attraction force of the carrier 2 is reduced from N _2, as shown in FIG. 3 (d), the conventional magnetic pole S ₃ carrier 2 which has been deposited on the magnetic pole N to become as deposited between ₂ -S _3, even if reverse polarity n has occurred between the magnetic poles S ₃ -S _1, pole
Carrier 2 is never transported to S ₁ .

[Advantages of the Invention] According to the present invention, it is possible to prevent the carrier collected from the cleaning magnet roll from riding on the downstream side in the sleeve rotation direction from the magnetic pole arranged at the position where the carrier naturally falls, thus improving print quality. It is possible to obtain a cleaning magnet roll that does not have an adverse effect.

[Brief description of drawings]

1 (a) and 1 (b) are cross-sectional views showing problems of the prior art, FIG. 2 is a cross-sectional view showing an embodiment of a cleaning roll of an electrophotographic apparatus according to the present invention, and FIG. 3 (a). ~ (D)
FIG. 4 is an explanatory view showing the operation of the present invention. In the figure, 1 is a photosensitive drum, 2 is a carrier, 3 is a cleaning magnet roll, 3a is a magnet, and 3b is a sleeve.

Claims (2)

[Scope of utility model registration request] 1. A cylindrical magnet having a plurality of magnetic poles, and a sleeve rotatably supported on the outer circumference of the magnet, and a carrier adhering to the photosensitive drum at a portion facing the photosensitive drum is attracted onto the sleeve. In the cleaning magnet roll of the electrophotographic apparatus, which collects and collects the magnet, the magnet has at least a first magnetic pole arranged at a position where the collected carrier naturally falls, and the first magnetic pole has the same pole as the first magnetic pole and the first magnetic pole. A second magnetic pole arranged at a predetermined angle downstream from the magnetic pole in the sleeve rotation direction, and a magnetic flux density of a reverse pole generated between the first magnetic pole and the second magnetic pole is n, When the magnetic flux density of the first magnetic pole is S and the peripheral speed of the sleeve is v, the relationship of (n / S) v ≤ 2.2 (cm / s) is satisfied. Gumma roll. 2. The magnetic flux density of the first magnetic pole is S,
S / N ≦ 1/2, where N is the magnetic flux density of the third magnetic pole that is opposite to the magnetic pole of the third magnetic pole and is located closer to the upstream side in the sleeve rotation direction than the first magnetic pole. A cleaning magnet roll for an electrophotographic apparatus according to claim 1, wherein