JPH0322994B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a non-magnetic sleeve with an N pole and an S pole inside.
Dry development in which high-resistance one-component magnetic developer is conveyed to the development position using a developing roller with magnets arranged alternately with poles, and is supplied to the latent image on the latent image forming body to perform development. Regarding equipment.

Conventionally, this type of developing device uses a developing roller in which a magnet with several poles is placed inside a non-magnetic sleeve. However, the magnetic toner on the sleeve can only move slowly, and sufficient triboelectric charging cannot be obtained. There is a method of improving frictional charging by rotating both the sleeve and the magnet in opposite directions, but in this case, the toner tends to scatter, causing background stains during development. There is a method of developing by forming a thin film of developer on the sleeve, but in this case the development gap becomes extremely narrow and it is difficult to maintain this gap.Also, because the gap is narrow, the electric field development effect is small and the reproducibility of low contrast is poor. bad. In addition, in the touch-down method, in which a thin layer of toner is brought into contact with a latent image forming body and developed, the toner is brought into pressure contact, which tends to cause toner blocking, which causes deterioration of image quality, and also has a small electric field development effect, resulting in low contrast reproducibility. It had some bad flaws.

The present invention provides a developing device that improves the above-mentioned drawbacks of conventional various developing methods using high-resistance one-component magnetic developers, can obtain sufficient triboelectric charging, and can easily maintain a development gap and provide high image quality. The purpose is to

Hereinafter, the present invention will be explained in detail based on drawings showing embodiments thereof.

FIG. 1 is a diagram showing an embodiment in which a developing device of the present invention is used in a copying machine using a photoconductive belt as a latent image forming member.

Photoconductive belt 1 is wound around a pair of belt transport rollers 2 and rotated in the direction of the arrow. Around the photoconductive belt 1, in the order of its rotating direction,
A charging charger 3, an exposure system 10, a developing device D, a transfer roller 11, a transfer charger 12, a static elimination charger 14, a static elimination lamp 15, and a cleaning device 16 are provided.

As shown in the figure, in the developing device which is the subject of the present invention, a developing roller 4 is provided in a developing tank in close proximity to the photoconductive belt 1, and the point of proximity is the developing position. A toner peeling roller 6 having a magnet 6 - 1 inside is provided in contact with the developing roller 4 on the downstream side of the developing position, and a magnetic doctor 9 is located at a position approximately symmetrical to the developing position, and a magnetic doctor 9 is attached between its tip and the developing roller 1 . A gap is provided between the two and the toner layer to obtain a toner layer thickness of approximately 0.1 to 0.5 mm. A high-resistance one-component magnetic toner 5 is stored in the developing tank, and a toner stirring roller 8 is provided to loosen the toner into a light ash and supply it to the developing roller 4.

The developing roller 4 is a fixed non-magnetic sleeve 4.
-1 and a small section magnet 4 rotating within the sleeve.
It is composed of 2. The segment width (reversal magnet width) of the small segment magnet 4-2 is about 0.1 to 2 mm, which is much narrower and has a larger number of segments than conventional magnets with several poles. For this reason, sleeve 4-1
Since the upper magnetic developer 5-2 is conveyed toward the development position while rotating many times on the sleeve, sufficient frictional electrification can be obtained.

At the developing position on the developing roller sleeve 4-1,
A chevron-shaped development auxiliary member 4-4 made of an elastic material containing a high permeability magnetic material is provided with its protruding portion facing toward the photoconductive belt 1. Belt conveyance roller 2
A development auxiliary magnet 2-1 is provided at a position facing the development auxiliary member on the inner side. The height from the base of the development auxiliary member 4-4 in contact with the sleeve 4-1 to the tip is about 0.5 to 3 mm, and the gap between the tip and the surface of the photoconductive belt 1 is about 0.2 to 2 mm. The sum is set to be 1 mm or more. The resistance of the development auxiliary member 4-4 is 10 ⁹ Ω
It is desirable to set it to cm or more.

Since this device is constructed as described above, the high-resistance one-component magnetic toner 5 in the developing tank is thinned to a film thickness of about 0.1 to 0.5 by the magnetic doctor 9, and the subdivided magnet in the developing roller 4 is 4-2 rotates, it moves on the fixed sleeve 4-1 while rotating much more actively than in the past, and is conveyed to the developing section. This improves the effects of developer movement, rotation, and mixing, and provides sufficient triboelectric charging.

In the developing section, the toner is formed on a developing auxiliary member 4-4 by a developing auxiliary magnet 2-1 disposed within the belt conveyance roller 2 to form a toner brush 5-1, and is charged by the charging charger 3 and exposed to light. The imagewise exposure by system 10 develops the electrostatic latent image formed on photoconductive belt 1 .

The development auxiliary member 4-4 is not only made of an elastic material containing the above-mentioned high magnetic permeability magnetic material, but also made of fiber having high magnetic permeability and having a high central portion when viewed in cross section, as shown in FIG. It is also possible to make it as a brush 4-4b.

After development, the toner on the sleeve 4 is removed into the developer tank by a toner peeling roller 6. On the other hand, the toner image visualized on the photoconductive belt 1 is transferred by the transfer charger 12 to a transfer paper 13 fed to a transfer position, and the transfer paper is separated from the photoconductive belt 1. The image is fixed by a fixing device (not shown) and the copying is completed.

After transfer, the photoconductive belt is placed in static elimination charger 1.
4 and a static eliminating lamp 15, and a cleaning device 16 cleans the remaining toner. In the case of this developer, it is appropriate to use a magnetic fibrous roller or the like as a cleaning device.

Since the sum of the height of the development auxiliary member 4-4 and the toner brush formed between its protrusion and the surface of the photoconductive belt 1 is 1 mm or more, the reproducibility of low-contrast images is improved. It is easy to adjust and maintain a good development gap, and image unevenness is reduced. Furthermore, even if the distance between the development auxiliary member 4-4 and the conductive belt 1 changes, the thickness of the toner brush will be the same as the development auxiliary member 4-4 and the magnet 2-4, which is disposed opposite to the inside of the belt conveyance roller 2. The tip of the toner brush is always in contact with the surface of the conductive belt 1, allowing for good development without uneven development.

As in the embodiments described above, the present invention can be applied not only to a developing device of a copying machine that uses a photoconductive belt as a latent image forming member, but also to an image recording device that uses a dielectric belt or a magnetic belt. effect can be obtained. In the case of a magnetic belt, a magnetic recording head or a laser head is used as the recording method.
The magnetic material is preferably a perpendicular recording medium. If a magnetic recording head is used, it is desirable to locate the head inside the belt to avoid contamination of the head with toner.

As described above, according to the present invention, it is possible to obtain sufficient triboelectric charging using a high-resistance one-component magnetic developer, and it is easy to adjust and maintain the development gap in the best condition, thereby improving the quality of recorded images. You can get a noticeable effect on improvement.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view showing another embodiment of the development auxiliary member. 1...Latent image forming body, 2-1...Development auxiliary magnet,
4...Developing roller, 4-1...Nonmagnetic sleeve,
4-2... Subdivided magnet, 4-4... Development auxiliary member, 5... High resistance one-component magnetic developer.

Claims (1)

[Claims] 1. A divided width is provided inside the fixed non-magnetic sleeve.
A high-resistance one-component magnetic developer is conveyed to a developing position using a developing roller equipped with magnets in which north and south poles are arranged alternately in subdivisions of about 0.1 to 2 mm, and the latent image forming body is conveyed to the developing position. In a dry type developing device that performs development by supplying the latent image to A developing device characterized in that a developing auxiliary magnet is disposed at a position facing the protrusion of the developing auxiliary member.