JPS62165674A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent carriers from entering the 2nd developing device and the carriers of the 1st developing device from being consumed, and to obtain an images having good quality by returning the carriers recovered to a carrier sticking preventing member into the 1st developing device. CONSTITUTION:The 1st developing device 2 has a two-component developer 3 consisting of carriers and toner and performs contact development. The 2nd developing device 6 has a single-component developer 7 containing no carrier and performs noncontacting development. A shutter 10 is provided between a photosensitive drum 1 and a developing roller 8 and the carriers from a photosensitive drum 1 which are attracted by the developing roller 8 are accumulated nearby the tip part of the shutter 10. The shutter 10, on the other hand, moves back to a position distant from the photosensitive drum 1 as the 2nd developing device 6 approaches to the photosensitive drum 1 and the tip part which holds carriers CR is stopped at a position below the developing roller 4 of the 1st developing device 2. Therefore, the carriers CR accumulated at the tip part of the shutter are attracted to the developing roller 4 and recovered into the 1st developing device.

Description

Detailed Description of the Invention --1 The present invention provides a first developing device having a two-component developer on the upstream side of a latent image carrier, and a one-component developer on the downstream side of the first developing device. The present invention relates to an image forming apparatus including at least one second developing device.

Recently, the demand for color images has rapidly increased not only in special fields but also in the general °+Sa field, and various image forming apparatuses have been proposed to meet this demand.

In image forming apparatuses that are currently widely used, contact development is performed using a two-component developer consisting of toner and carrier on the upstream side of the Wq image carrier, and in particular, a first developer for color toners such as red and blue is used. A developing device is provided, and a second developing device for black toner, which performs non-contact development using an l-component developer without a carrier, is provided downstream of the :51 developing device. This is because bright colored toner cannot be produced using a one-component developer, and also because it is preferable to place the black toner at the bottom to minimize the problem of color mixing.

, 1 ga Shira ,
1 In such an image forming apparatus, the toner and carrier in the two-component developer of the first developing device are charged with opposite polarities, so that the carrier is not transferred to the background potential area (non-image area) on the latent image carrier. Adhesion is inevitable.

Therefore, when a two-component developing system is used in the first developing device, when the carrier attached to the latent image carrier passes through the second developing device, it is attracted to the second developing device by the magnetic force of the second developing device. , get mixed inside.

For this reason, the carrier may be trapped in the toner thickness regulating section of the second developing device, causing failure in coating the developer on the developer holding member such as the developing roller, or may rub against the latent image carrier, resulting in the formation of an image. There were problems such as staining.

Also, in the first developing device, if the device adopts a developing method in which the mixing ratio of toner and carrier is controlled by the volume, once the carrier is consumed, the mixing ratio cannot be kept constant; This had the disadvantage that it was not possible to achieve the required development.

The present invention was made in view of the above problems, and its purpose is to prevent carrier from being mixed into the second development stage, and to:
1. An object of the present invention is to provide an image forming device capable of preventing the consumption of this carrier and obtaining high quality images.

81. The objective of 42.1 for aging is achieved by the image forming apparatus according to the present invention. In summary, Book 9.1jI includes a first developing device that performs contact development using a two-component developer consisting of toner and carrier disposed on the flow side of a latent image carrier; and at least one second developing device that performs non-contact development using a one-component developer without a carrier, which is disposed on the downstream side, wherein the first developing device is provided with a carrier from the device. Carrier adhesion +1:i to prevent adhesion to the developer holding member at the second development stage Sc
′! The image forming apparatus is characterized by having a B material and a means for returning the carrier collected by the carrier adhesion prevention member into the first developing device.

Although the image forming apparatus according to the present invention can be suitably used in a multi-color or full-color photocopying apparatus, a color recording apparatus for a computer output section, etc., in this embodiment, The present apparatus will be described as being applied to a color electrophotographic copying apparatus for obtaining two-color images of black and red.

Further, such a color electrophotographic copying apparatus includes various electrostatic latent image forming processes, such as an rtN p process or a single rtN p process, including various electrostatic latent image forming processes, such as a single image forming process, a secondary charging/color separation exposure process, and a full surface exposure process. The so-called Carlson process, which includes steps of subsequent charging and color separation exposure, and others may be used, but in this embodiment, an electrophotographic copying apparatus to which the Carlson process is applied will be described.

First, the overall configuration of the color electrophotographic copying device will be described with reference to FIG. 1. At the approximate center of the copying device,
A Wq image carrier, that is, in this embodiment, a photosensitive drum l having an electrophotographic photosensitive layer formed on its surface is disposed. The photosensitive drum l is mounted on a rotation support shaft (with a rotation center O) in a well-known manner.
In the embodiment in which the photosensitive drum 1 is rotatably and removably attached to a drum (not shown), it is assumed that the photosensitive drum 1 rotates in the direction of arrow X, that is, clockwise in FIG.

1 is placed on the right side of the photosensitive drum 1 (as viewed in FIG. 1). A transfer discharger T is disposed approximately directly below the photosensitive drum 1, and a cleaning device C is disposed on the left side of the photosensitive drum 1 (as viewed in FIG. 1). Further, an optical system (not shown) is disposed in the upper part of the electrophotographic copying apparatus, and an optical system (not shown) is arranged in the upper part of the electrophotographic copying apparatus to transfer the original image to the exposure section E located close between the primary charging device and the developing device 2!12. and is configured to project the image onto the photosensitive drum 1.

The operation of a color electrophotographic copying apparatus configured as a duplex will be briefly explained.

The photosensitive drum 1 begins to rotate in the direction of the arrow X at the start of operation, and is charged by the primary charging device.

The loaded photosensitive drum 1 further rotates, and the optical system exposes the light image to slit light at the exposure section E, forming electrostatic latent images of each color on the photosensitive drum 1. The latent image on the photosensitive drum 1 is then transferred to the developing device 2 by rotation of the photosensitive drum 1.
6 is brought to the development area where t is arranged. In the developing device, the electrostatic latent image on the photosensitive drum 1 is visualized as a toner image.

The toner image on the photosensitive drum 7 is transferred onto a transfer material P fed from a paper feeding device (not shown) in a transfer area where a transfer discharger T is arranged. The transfer JJP carrying the toner image is then conveyed to a fixing device (not shown) and fixed thereon.

After the photosensitive drum 1 is subjected to the action of the cleaning device c and the light source, the next image forming process is performed again.

Next, the developing device 212.6 will be explained. Each developing device includes a developing roller, ie, a developer holding member 4.8, consisting of a non-magnetic sleeve with a magnet inside.

In this embodiment, a first developing device 2 is provided upstream of the latent image carrier, that is, the photosensitive drum l. Does the first developing device 212 consist of carrier and toner? It has a component developer 3 and can freely approach and separate from the photosensitive drum 1, and when in contact, the photosensitive drum 1 is moved by a developing brush formed on the developing roller.
The amount of bristling of the developing brush that performs contact development on the upper electrostatic latent image is adjusted by the brush regulating member 5.

Further, on the downstream side of the first developing device 2, a second developing device 2 is arranged so as to be able to freely approach and separate from the photosensitive drum 1, and to be slightly separated from the photosensitive drum 1 during close development operation.
16 are provided. The second developing device 2t6 coats a one-component magnetic developer 7 without a built-in carrier on a developing roller 8, which is a developer holding member, in a thin layer to form an electrostatic latent image formed on the photosensitive drum l. The developer coating thickness for performing non-contact development (jumping development) is adjusted by a developer layer thickness regulating member 9.

Further, the developing roller 8 is preferably not operated, ie, not rotated, while the first developing device 2 is in use. The reason for this will be explained later.

According to the final IJ+, the first developing device 2 and the second developing device 6
A developer holding member near the second developing unit, i.e.,
A shutter 10 made of a non-magnetic material is provided to cover the developing roller 8.

In this embodiment, the shutter IO is formed of a rectangular plate member whose cross section is approximately in the shape of the character "<", and extends over the entire longitudinal direction of the developing device, and has both ends connected to the guide (1).
1 and 12). The shutter 1O is moved toward and away from the photosensitive drum 1 by a driving means such as a solenoid (not shown).
When the front edge 10a of 0 is close to the photosensitive drum l (FIG. 1), it covers the exposed part of the developing roller 8 of the second developing device, and when it is separated from the photosensitive drum l (FIG. 2), it covers the exposed part of the developing roller 8 of the second developing device. The second developing device 6 is configured to be separated from the movement path of the second developing device 6 so that it can approach the photosensitive drum l.

Now, when development is performed by the first developing device 2, each developing device is arranged as shown in FIG. 1, and as described above, the developing roller 8 of the second developing device 6 is not rotating. When development is performed in the first developing device 212, some carrier adheres to the photosensitive drum l. When the photosensitive drum 1 passes near the second developing device 6, this carrier is attracted toward the developing roller 8 by the magnetic force (31 poles) of the developing roller 8 of the second developing device 6. However, according to the present invention, the photosensitive drum 1 and the developing roller 8 of the second developing device
A shutter 10 is disposed between the developing roller 8 and the developing roller 8. Therefore, the carriers from the photosensitive drum 1 that are attracted by the 53 poles of the developing roller 8 are blocked near the tip of the shutter 10 and remain there. .

On the other hand, as the developing mold fi6 approaches the photosensitive drum 1 in order to activate the second developing device 6, the shutter 10 retreats to a position away from the photosensitive drum 1, as shown in FIG. The tip of the shutter 10 holding the carrier CR is the first developing device F! It is stopped at a point located below the 12 developing rollers 4. As a result, the carrier CR staying at the leading end of the shutter is attracted to the developing roller 4 and collected into the first developing device.

As described above, in this embodiment, the shutter, that is, the carrier adhesion prevention means lO, moves toward the photosensitive drum in synchronization with the movement of the first developing device 212 toward the photosensitive drum only when the first developing device 6 is used. , and the second developing device 6
The carrier adhesion preventing means 10 moves backward as the second developing device 6 moves toward the photosensitive drum, and transfers the captured carrier to the first developing roller 8. It cooperates with the developing roller of the developing device and functions to return the image to the first developing device 2.

As described above, according to the image forming apparatus according to the present invention, the carrier is prevented from entering the second developing device, and the second developing device is prevented from entering the second developing device.
This solves the problem of color mixing in the developing device, prevents carrier scattering to the transfer device, separation charging device, etc., and eliminates damage to the cleaning blade of the cleaning device caused by the carrier. Furthermore, the carrier scattered from the first developing device 92t is recovered, so that the carrier field within the first developing device can be kept constant, and there is an advantage that a good image can be obtained.

[Brief explanation of drawings]

FIG. 1 shows a schematic configuration of an embodiment of an image forming apparatus according to the present invention, and is a sectional view in which a first developing device is in a developing operation position. be. FIG. 2 is a schematic sectional view showing only the developing device portion of the image forming mold shown in FIG. 1, with the second developing device in the developing operation position. 1: Photosensitive drum (image carrier) 2: First developing device 3: Two-component developer 4.8: Developer holding member 6: Second developing device 7: One-component developer IO: Carrier adhesion prevention means agent Patent attorney Shikura Tachibana Aki Ko-ζ・,jll 1.2,! ; Figure 2

Claims (1)

[Scope of Claims] 1) A first developing device that performs contact development using a two-component developer consisting of toner and carrier, which is disposed upstream of the latent image carrier, and a downstream side of the first developing device. and at least one second developing device that performs non-contact development using a one-component developer without a carrier disposed in the first developing device, wherein the carrier from the first developing device is used in the second developing device. It is characterized by comprising a carrier adhesion prevention member for preventing the carrier from adhering to the developer holding member of the device, and a means for returning the carrier collected by the carrier adhesion prevention member into the first developing device. Image forming device. 2) The carrier adhesion prevention means is a shutter provided to cover the developer holding member of the second developing device, and the means for returning the carrier to the first developing device moves the shutter to the position of the developer holding member of the first developing device. 2. The image forming apparatus according to claim 1, wherein the carrier held by the shutter is returned to the first developing device by the magnetic force of the developer holding member of the first developing device.