JPH08328367A - Multicolor image forming device - Google Patents

Abstract

PURPOSE: To provide a rotary developing device which is a small, simple structure, has a stable development characteristic flee of irregular development density, fog, etc., and prevents toner scatter. CONSTITUTION: In each of developing units 91-94, a partition B having an opening A is provided between a developing-roll container 12 containing a developing roll 10 and a toner hopper 13 storing toner 16, and a shutter 14 for opening/ closing the opening A is provided on the side of the developing-roll container 12. When developing units 91-94 rotate as the rotary developing device 9 rotates, the toner in the toner hopper 13 is restrained from excessively moving into the developing-roll container 12 through the opening A. Thus, because the insufficiently-electrified toner is prevented from excessively moving into the container 12, the stable development characteristic can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus equipped with an electrophotographic developing device, such as an electrophotographic copying machine or an electrophotographic printer, and more particularly to a rotary multicolor developing device comprising a plurality of developing devices. The present invention relates to a provided multicolor image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, a copying machine or a laser beam printer using an electrophotographic process has a structure as shown in FIG.

In the figure, the photosensitive drum 1 rotating in the direction of arrow R1 is charged to a predetermined potential by a charging device 2, and then an image forming exposure optical system based on color separation of a color original image and image information. The first color component of the target color image by receiving the optical image information by the exposure device 3 including the scanning exposure optical system by the laser scanner that outputs the laser beam modulated corresponding to the time series electric digital pixel signal, For example, an electrostatic latent image corresponding to the magenta component image is formed.

Then, the electrostatic latent image is formed on the rotary developing device 4.
By facing the first developing device 41, for example, a magenta color developing device, the image is visualized in magenta color. The magenta developed image on the photosensitive drum 1 is electrostatically transferred onto the recording paper 6 which is electrostatically carried on the surface of the transfer drum 5, and the residual developer on the photosensitive drum 1 is cleaned by the cleaning device 7.

Thereafter, similarly, the cyan, yellow, and black development and transfer processes are sequentially repeated, so that the above-described four toner images (magenta) are formed on the recording paper 6 on the transfer drum 5 fed from the recording paper cassette 20. M, cyan C, yellow Y, and black B toner images) are superimposed and transferred to form a composite color toner image corresponding to the target color image.

The recording paper 6 which has undergone the superposition transfer process is
The toner image is separated from the transfer drum 5, conveyed to the fixing device 8 and heated and pressed by the fixing roller 81 and the pressure roller 82 which are heated and adjusted to a predetermined temperature, and the toner image is fixed and finally output.

The rotary developing device 4 described above comprises a magenta developing device 41, a cyan developing device 42, a yellow developing device 43 and a black developing device 44. Each developing device mixes a magnetic carrier such as iron oxide powder with a non-magnetic colored toner and develops it with a magnetic brush in the developing section. A two-component developing device or a developer consisting of only non-magnetic toner is applied to the developing roll for development. A non-magnetic one-component developing device or the like is used.

The rotary developing device 4 is driven to rotate in the direction of arrow R2, and the developing device corresponding to the electrostatic latent image of each color formed on the photosensitive drum 1 stands still at a position facing the photosensitive drum 1, and the developing roller Rotates while keeping the opposition to the photosensitive drum to visualize the electrostatic latent image.

[0009]

However, in the rotary developing device described in the above-mentioned conventional example, the insufficiently charged developer in the developer hopper excessively moves to the developing position due to the reversal of the developing device accompanying the rotation operation. As a result, the developer may be insufficiently charged, resulting in uneven development density, fogging, and toner scattering into the apparatus. In order to prevent these, each developing device is configured like a ferris wheel so as to always maintain an up and down posture even when it is rotated. However, the attaching / detaching mechanism at the position facing the supporting means of each developing device and the photosensitive drum. Therefore, there is an inconvenience that the size and complexity of the apparatus are increased due to the provision of the above.

Therefore, an object of the present invention is to provide a multicolor image forming apparatus having a rotary developing device which is compact and has a simple structure and which can achieve the above-described stabilization of the developing characteristics and prevention of scattering of the developer. is there.

[0011]

The above object can be achieved by a multicolor image forming apparatus according to the present invention. In summary, the present invention provides a multi-color image having a rotary developing device that carries and rotates a plurality of developing devices and stops the rotation at a position where the developing devices face the image carrier to perform visualization. In the forming apparatus, the developing device includes a first container for accommodating a developer and a second container including a developer carrier, which are joined to each other with an opening. A multicolor image forming apparatus characterized by comprising a shutter mechanism that opens and closes only at the top.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multicolor image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. In the embodiments described below, the present invention is embodied in the multicolor image forming apparatus shown in FIG. Therefore, the detailed description of the overall configuration and function of the multi-color image forming apparatus is incorporated by reference above, and the features of the present invention will be described.

Embodiment 1 Referring to FIG. 1, a rotary developing device according to Embodiment 1 of the present invention comprises a photosensitive drum 1 as an image carrier, a charging device 2 and an exposing device 3 which are arranged around the photosensitive drum 1. This is similar to the above-mentioned conventional example. The developing device shown in this embodiment uses a two-component developer including a magnetic carrier such as iron oxide powder and a non-magnetic toner.

The rotary developing device 9 includes magenta M, cyan C, yellow Y, and black B developing units 91, 92, and 9.
3, 94, which rotate in the direction of arrow R2 in order to switch each developing device to a position facing the photosensitive drum 1. Further, since the developing devices 91, 92, 93, and 94 are fixed to the main body of the rotary developing device and rotate, the developing device alone is rotated vertically and horizontally. Each developing device has the same configuration.

In FIG. 2, each developing device constituting the rotary developing device 9 includes a developing roll 10 composed of a non-magnetic sleeve 10b having a magnet roll 10a therein and rotating, and a non-magnetic toner 15 and Magnetic carrier 1
A developing roll container 12 as a second container for containing the developer T composed of 6 and a toner hopper 13 as a first container for containing the non-magnetic toner 16 are provided.

Developing roll container 12 and toner hopper 1
3 is joined via the opening A, and the toner 16 in the toner hopper 13 is configured to move to the developing roll container 12 through the opening A.

More specifically, a shutter 14 is provided in the opening A, and the shutter 14 is swingably fixed to a partition plate B above the opening by a hinge 11. Since the shutter 14 is disposed on the developing roll container 12 side and the free end C thereof is below the opening A, the opening / closing operation of the shutter 14 is limited to the developing roll container 12 side.

Next, the attitude of the developing device and the movement of the shutter 14 at each station due to the rotation of the rotary developing device will be described with reference to FIGS.

FIG. 3A shows the magenta developing unit 91 shown in FIG.
In this position, the developing device faces the photosensitive drum carrying the electrostatic image and visualizes the image. The mixed two-component developer T in the developing roll container 12 is in a state in which the toner 16 is electrostatically attached to the surface of the magnetic carrier 15 and is evenly applied to the surface of the developing roll 10 by the doctor blade 17. A magnetic brush is formed at a position facing the photosensitive drum by the magnetic field of the internal magnet, and the toner 16 is adhered to the electrostatic image to visualize it. At this time, the shutter 14 loosely closes the opening A in a state of hanging downward by its own weight as shown in the figure.

FIG. 3B shows the position of the cyan developing device 92 shown in FIG. 1 at the station which has come to the upper position due to the rotation of the device after the developing device has completed the image development process. At this time, the shutter 14 receives a downward force due to its own weight and the weight of the developer T, but since its length is longer than the joint opening A of the developing roll container 12 and the toner hopper 13, it is opened toward the toner hopper 13 side. The opening A is substantially closed to prevent the developer T from moving into the toner hopper 13.

FIG. 3C shows the yellow developing device 93 of FIG.
3B shows the state of the developing device when it is rotated by 90 degrees from the state of FIG. Although the free end C of the shutter 14 is located above and is about to open toward the developing roll container 12 side due to gravity, the movement of the shutter 14 is restricted by the developer T in the container 12. Even if the shutter 14 is slightly open, the toner 16 on the toner hopper 13 side is located below the toner hopper 13,
The developer T does not move to the developing roll 10 side through the opening A.

FIG. 3D shows the black developing device 94 of FIG.
In this position, the developing device is in the lowest position of the rotary developing device. The shutter 14 is
Although it opens to the developing roll 10 side by gravity, the open state is suppressed by the developer T in the developing roll container 12, and the toner 16 as the shortage of the developer T in the developing roll container 12 opens the shutter 14 from the toner hopper 13. It moves to the developing roll container 12 side through the opened portion.

As described above, the shutter 14 provided in the opening A of the developing roll container 12 moves excessive developer T from the developing roll container 12 to the toner hopper 13 side by the rotating operation of the rotary developing device. In addition to preventing the above, it functions by opening and closing in the opposite direction to make up for the insufficient amount.

As a result, the insufficiently charged toner 16 in the toner hopper 13 excessively moves to the developing roll container 12, causing the developer T to be in an insufficiently charged state, resulting in uneven development density, fog and in-apparatus. It is possible to solve the conventional problem such as toner scattering to the surface.

By the way, the graphs shown in FIGS. 4 (a) and 4 (b) are based on the present invention, and there is a shutter mechanism at the opening between the toner hopper and the developing roll container (a).
In the case (b) where there is none, a black image is formed every time the rotary developing device makes one revolution in the developing device using the black B developer, and the density transition thereof is recorded.

As shown in FIG. 4, in the case where the shutter mechanism is not provided (b), the density fluctuates greatly when the density is excessively high, and on the other hand, background stain (fogging phenomenon) is conspicuous. Further, when the rotating operation was repeated 1000 times, the accumulation of scattered toner on the lower portion of the developing device was conspicuous.

On the other hand, when the shutter mechanism is provided at the opening according to the present invention (a), the image density reproducibility is stable. In addition, the fogging phenomenon has remained inconspicuous.

FIGS. 5A and 5B show the toner charge amount (Q / M) and the toner application amount (M) on the developing sleeve with and without the shutter mechanism (a) and (b), respectively. / S), the shutter mechanism (a) maintains a high toner charge amount and the toner application amount is a low constant value, whereas the shutter mechanism does not have a shutter mechanism. In the case of only part (b), the toner application amount is relatively large and the charge amount is largely changed in a low region.

In this phenomenon, when the developing device is turned upside down, the magnetic developer once flows into the toner hopper, and then, when it returns to the developing roll container side due to rotation, an excessive amount of toner is entrained, so that the toner amount increases. The chances of frictional electrification decrease, the electrification becomes insufficient, the density fluctuation, the fog phenomenon increase, and the toner scattering in the apparatus occurs.

Second Embodiment Next, the second embodiment of the rotary developing device according to the present invention will be described.
This will be described with reference to FIGS. 6 and 7. The present embodiment relates to the case where a non-magnetic one-component developer is used in each developing device.

As shown in FIG. 6, the rotary developing device according to the present embodiment has a configuration similar to that of the first embodiment.
The rotary developing device 9A includes magenta M, cyan C, yellow Y, and black B developing units 91A, 92A, 93A, and 94.
A is provided and rotates in the direction of arrow R2 in order to switch each developing device to a position facing the photosensitive drum 1.
Further, since the developing devices 91A, 92A, 93A, 94A are fixed to the rotary developing device main body and rotate, the developing device alone is rotated upside down and horizontally. Each developing device has the same configuration.

In FIG. 7, the non-magnetic one-component developing device comprises a developing roll container 12 containing a developing roll 19 and a toner hopper 13 containing a non-magnetic toner 16, and the developing roll container 12 and toner hopper 13 are Similar to the first embodiment, they are joined through the opening A, and the shutter 14 is provided in the opening A so as to be opened and closed only on the developing roll container 12 side.

The developing roll 19 is a semi-conductive magnetic developing roll, and an elastic roll 18 such as a conductive rubber sponge and an elastic blade 21 are arranged in pressure contact with the developing roll 19. The non-magnetic toner 16 is charged by the elastic roll 18 to the developing roll 19 by pressure contact rotation. After that, a uniform developer layer is formed on the developing roll 19 by the elastic blade 21.

The charging mechanism of the non-magnetic toner 16 in the present developing device is a frictional contact between the elastic coating roll 18 and the developing roll 19 and the elastic blade 21 and the developing roll 19.
When the developing device is turned over by the rotation of the developing device, the movement of the toner in the developing roll container 12 is restricted by the opening / closing operation of the shutter, so that a large amount of the non-magnetic toner 16 Is less likely to be generated by directly supplying toner to the developing roll 19, and thus stable image reproduction characteristics can be achieved.

[0035]

As is apparent from the above description, according to the present invention, the developing device has the first container for accommodating the developer and the second container including the developer carrier having the opening. And a shutter mechanism that opens and closes only on the side of the second container is provided in the opening, so that a small and simple rotary developing device configuration can prevent upside-down movement due to rotation of the developing device. Also, stable image reproducibility can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of a rotary developing device according to the present invention.

FIG. 2 is a configuration diagram of a developing device included in the rotary developing device of FIG.

FIG. 3 is a rotation station (a) to (d) of the first embodiment.
FIG. 3 is an explanatory diagram illustrating the attitude of the developing device and the movement of the shutter in FIG.

FIG. 4 is a graph for explaining density and fog transition depending on presence / absence of a shutter.

FIG. 5: Q / on the developing roll with / without shutter
It is a graph for explaining the transition of M and M / S.

FIG. 6 is an explanatory view showing a second embodiment of the rotary developing device according to the present invention.

FIG. 7 is a configuration diagram of a non-magnetic one-component developing device that constitutes a rotary developing device.

FIG. 8 is a configuration diagram showing an example of a conventional rotary developing device.

[Explanation of symbols]

 1 Photosensitive Drum (Image Carrier) 10 Development Roll (Developer Carrier) 12 Development Roll Container (Second Container) 13 Toner Hopper (First Container) 14 Shutter A Opening

Claims (1)

[Claims] 1. A multicolor image forming apparatus equipped with a rotary developing device that carries a plurality of developing devices, rotates, and stops rotation at a position where the developing devices face the image carrier to visualize the image. In the developing device, a first container for containing a developer and a second container containing a developer carrier are joined together with an opening, and the opening is provided only on the side of the second container. A multicolor image forming apparatus comprising a shutter mechanism that opens and closes.