JPH07261543A - Image forming device - Google Patents

Abstract

PURPOSE:To position a developing unit and an image carrier with high accuracy without transmitting the shock generated when the developing unit is moved to the image carrier by providing a circular arc face centering on a rotary shaft on a bearing block rotatably supporting the image carrier, and bringing the circular arc face into contact with the developing unit. CONSTITUTION:A frame section is formed with the front and rear side plates 61 of a unit connected by a connecting member 5, a drum guide member 66 and a bearing block 62 are fixed to the front and rear side plates 61 with screws 63, 64 respectively, and the drum guide member 66 and bearing block 62 support boss sections 1h provided on the front and rear flanges 1b, 1c. The bearing block 62 has a circular arc face 62a centering on the drum shaft. The bearing block 62 has a fan shape extended to nearly the same shape as a photoreceptor drum 1 on the development side, and a positioning face 62a butted with a butt roller provided concentrically with a sleeve carrying the developer of multiple developing units is provided on the end face. The gap between the photoreceptor drum 11 and the developing sleeve can be secured with high accuracy.

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 such as an electrophotographic system and an electrostatic recording apparatus, and more particularly to a full color image forming apparatus.

[0002]

2. Description of the Related Art In a one-drum full-color copying machine, conventionally, the position of a developing device and a photosensitive drum has been ensured by abutting rollers provided coaxially with a developing sleeve directly contacting the surface of the photosensitive drum. In the case of four-color development, at the timing when each of the developing devices containing four M, C, Y, and K toners develops each color, the photosensitive drum is brought into contact with or separated from each other without causing color mixing. A toner image of each color is made visible, and similarly, when viewed from the rotation direction of the photosensitive drum, a full-color image is obtained by transferring and superimposing each color onto the transfer material held on the transfer drum that is in contact with the downstream side of the developing device. I was able to.

However, with the recent demand for higher image quality, the shock of contact of the developing device with the photosensitive drum causes image blurring, which poses a problem, and it is possible to position the developing device without directly contacting the surface of the photosensitive drum. preferable.

Therefore, it is considered that the developing device is positioned at a position away from the surface of the photosensitive drum. That is, there is a method of providing positional accuracy by providing an abutting block with which a part of the developing device abuts on the front and rear side plates of the copying machine or the main body stay or the front and rear side plates of the drum kit frame.

[0005]

According to this method, the image blur is certainly reduced, but the dimensional accuracy is considerably deteriorated. Therefore, it is necessary to adjust and assemble the abutting block with high accuracy, and the workability is deteriorated. Problems such as displacement of the butting block due to loosening of the fixing screw will occur.
In particular, in a full-color copying machine with a four-color fixed development system, it is necessary to adjust the blocks at four locations, which complicates the work and makes mistakes.

[0006]

The present invention for solving the above problems provides an image forming apparatus having an image bearing member and a developing device provided in the vicinity of the image bearing member. It is characterized in that a bearing block having a bearing portion rotatably supported is provided with an arc surface centering on the rotation axis, and the developing device is brought into contact with the arc surface.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a full-color image forming apparatus according to an embodiment of the present invention.

This example has a digital color image reader section in the upper part and a digital color image printer section in the lower part.

In the reader unit, the original 30 is placed on the original table glass 31 and is exposed and scanned by the exposure lamp 32, whereby the reflected light image from the original 30 is condensed by the lens 33 on the full color sensor 34, and the color color is obtained. Obtain a decomposed image signal. The color-separated image signal passes through an amplifier circuit (not shown), is processed by a video processing unit (not shown), and is sent to the printer section.

In the printer section, the photosensitive drum 1 which is an image bearing member is rotatably supported in the direction of the arrow, and a pre-exposure lamp 11, a corona charger 2, a laser exposure optical system 3 and a potential sensor 12 are provided around the photosensitive drum 1. , Four developing devices 4y, 4c, 4m, 4Bk of different colors, on-drum light amount detecting means 1
3, the transfer device 5 and the cleaning device 6 are arranged.

In the laser exposure optical system 3 , the image signal from the reader section is converted into an optical signal by a laser output section (not shown), and the converted laser light is reflected by the polygon mirror 3a, and the lens 3b and the mirror. It is projected onto the surface of the photosensitive drum 1 through 3c.

During image formation in the printer section, the photosensitive drum 1
Is rotated in the direction of the arrow, the photosensitive drum 1 after the charge is removed by the pre-exposure lamp 11 is uniformly charged by the charger 2, and the light image E is emitted for each separated color to form a latent image.

Next, a predetermined developing device is operated to develop the latent image on the photosensitive drum 1 to form a powder toner image based on resin on the photosensitive drum 1. The developing device is adapted to selectively approach the photosensitive drum 1 according to each separated color by the operation of the eccentric cams 24y, 24c, 24m and 24Bk.

Further, the toner image on the photosensitive drum 1 is
The recording material is transferred onto the recording material supplied from the recording material cassette 7 to the position facing the photosensitive drum 1 via the transport system and the transfer device 5. In this example, the transfer device 5 includes a transfer drum 5a, a transfer charger 5b, and an attraction charger 5c for electrostatically attracting a recording material.
A recording material carrying sheet 5f made of a dielectric material in the peripheral opening area of a transfer drum 5a which has a suction roller 5g, an inner charging device 5d, and an outer charging device 5e which face each other. Is integrally stretched in a cylindrical shape. The recording material carrying sheet 5f uses a dielectric sheet such as a polycarbonate film.

As the drum-shaped transfer device, that is, the transfer drum 5a is rotated, the toner image on the photosensitive drum is transferred onto the recording material carried on the recording material carrying sheet 5f by the transfer charger 5b.

In this way, a desired number of color images are transferred to the recording material that is adsorbed and conveyed to the recording material carrying sheet 5f, and a full color image is formed.

In the case of full-color image formation, when the transfer of the four color toner images is completed in this way, the recording material is separated from the transfer drum 5a by the action of the separation claw 8a, the separation push-up roller 8b and the separation charger 5h, and the heat is removed. The sheet is discharged onto the tray 10 via the roller fixing 9 .

On the other hand, the post-transfer photosensitive drum 1 is subjected to an image forming process again after the residual toner on the surface is cleaned by the cleaning device 6.

When images are formed on both sides of the recording material,
Immediately after the fixing device 9 is discharged, the transport path switching guide 19 is driven, and after being guided to the reversing path 21a through the transport vertical path 20, the reverse end of the reversing roller 21b causes the trailing end when fed to the beginning. Then, it is withdrawn in the direction opposite to the direction in which it was fed and is stored in the intermediate tray 22. After that, an image is formed on the other surface by the above-described image forming step.

Further, in order to prevent the powder from being scattered on the recording material-carrying sheet 5f of the transfer drum 5a and the oil from being adhered to the recording material, the brush is interposed via the fur brush 14 and the recording material-carrying sheet 5f. 14, a backup brush 15 facing the sheet 14, an oil removing roller 16 and a recording material carrying sheet 5
Cleaning is performed by the action of the backup brush 17 that faces the roller 16 via f. Such cleaning should be done before or after image formation, or jam (paper jam)
When it occurs, it will be done as needed.

Further, in this embodiment, the eccentric cam 25 is operated at a desired timing and the cam follower 5i integrated with the transfer drum 5f is operated, so that the gap between the recording material carrying sheet 5a and the photosensitive drum 1 is reduced. The configuration can be set arbitrarily. For example, during standby or when the power is off, the transfer drum and the photosensitive drum are separated from each other.

2 to 6 are partial enlarged views around the photosensitive drum of the embodiment of the present invention.

FIG. 5 is a perspective view of the drum cylinder.

In FIG. 5, the drum cylinder 1a shown by the alternate long and short dash line is closed at both ends by a front flange 1b and a rear flange 1c whose outer diameters are substantially the same as the cylinder, and a connecting stay 1d is arranged inside. Has been done.

The front and rear flanges 1b and 1c are fixed screws 1f.
Are respectively screwed to the connecting stays 1d. In other words, the drum cylinder 1a is sandwiched by the front and rear flanges 1b and 1c and is pressed and fixed by the fastening force of the screw, whereby the drum cylinder 1a is integrally fixed. Through holes 1 in the flanges 1b and 1c
e, 1g are provided, and when incorporated in the main body of the copying machine, the drum shaft 1j is inserted and the fixed key 1k is provided with the cutout portion 1h provided on the outer diameter part of the boss portion 1h of the front flange 1b. The drum shaft and the flange are maintained in the rotational direction by being fitted to the position '.

FIG. 3 shows an assembled perspective view of the drum unit.

A drum guide member 66 and a bearing block 62 are fixed to the front and rear side plates by screws 63 and 64, respectively, in a frame portion formed by the unit front and rear side plates connected by a connecting member 65 and 61 (only the front side is shown). The drum guide member 66 and the bearing block 62 support the boss portion 1h provided on the front and rear flanges 1b and 1c.

This bearing block has an arc surface 62a centered on the drum shaft.

FIG. 6 is a sectional view of the drum unit.

As shown in FIGS. 3 and 6, the drum unit 1 is rotatably supported by the bearing block 62 and the bearing 62b even if the drum shaft 1j is not inserted in the flanges 1b and 1c in the copying machine main body. Has been done.

Next, the positioning of the image carrier and the developing device of this embodiment will be described in detail with reference to FIGS.

FIG. 2 is an enlarged view of a main part.

In FIG. 2, only the eccentric cam 24Y operates so that the developing device 4Y comes to a position (image forming state) where the developing device 4Y approaches the photosensitive drum. Further, the developing devices 4c, 4m and 4Bk are in the retracted position as can be seen from the eccentric cams 24c, 24m and 24Bk.

FIG. 3 shows a partial perspective view of the periphery of the bearing block 62.

A drum guide member 66 and a bearing block 62 are fixed to the front and rear side plates of the drum kit by screws 63 and 64, respectively, on a frame body formed by the front and rear side plates 61 (only the front side is shown) connected by a connecting member 65. The bearing block 62 is a boss portion 1h provided on flanges 1b fixed to both ends of the photosensitive drum cylinder 1a.
Is rotatably supported. On the other hand, the drum guide member 66
Is fixed to the back side of the front and rear side plates 61 of the drum kit and is supported by the drum guide member 66 even if the bearing block 62 is removed from the frame, so that the drum unit 1 does not drop in the direction of gravity and is not damaged. .

When the bearing block 62 is removed, the kit front and rear side plates 61 are provided with finger insertion notches 61a, and finger insertion holes 1b 'are also formed on the drum flange side. Therefore, when removing the drum unit from the frame when replacing the drum cylinder, first remove the bearing block 62, then rotate it until the finger insertion hole 1b 'of the drum flange matches the position of the notch 61a of the kit front and rear side plate 61, and then The order is that the finger is inserted and the finger is pulled out along the drum guide member 66.

In FIG. 4, 67 is a side plate of the image forming apparatus, and 68 is a bearing for rotatably supporting the drum shaft.

As shown in FIG. 2, the bearing block 62 is fan-shaped and extends to substantially the same shape as the photosensitive drum on the developing side, and its end face is concentric with the developing sleeve 4a carrying the developers of a plurality of developing devices. There is provided a positioning surface 62a on which the abutting roller provided on the abutting surface abuts.

Therefore, the gap between the photosensitive drum and the developing sleeve can be secured with high accuracy.

Further, since the drum and the developing device can be assembled without adjustment, the workability can be improved.

[0042]

As described above, according to the present invention, the developing device and the image bearing member can be positioned with high accuracy without transmitting a shock when the developing device is moved to the image bearing member.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a partially enlarged view.

FIG. 3 is a frame perspective view of a drum unit.

FIG. 4 is a sectional view of the drum unit frame in the axial direction.

FIG. 5 is a perspective view of a photosensitive drum.

FIG. 6 is a sectional view of the drum unit frame body in the axial direction when mounted on the main body.

[Explanation of symbols]

 1 Photosensitive Drum 4a Developing Sleeve 4b Abutting Roller 62 Bearing Block 62a Arc Surface 62b Bearing

Claims (4)

[Claims] 1. An image forming apparatus having an image bearing member and a developing device provided in proximity to the image bearing member, wherein the image bearing member is rotated by a bearing block having a bearing portion for rotatably supporting the image bearing member. An image forming apparatus characterized in that an arc surface centering on an axis is provided, and a developing device is brought into contact with the arc surface. 2. The image forming apparatus according to claim 1, wherein a plurality of the developing devices are provided, and the plurality of developing devices contact the arc surface. 3. The image forming apparatus according to claim 1, wherein the developing device is in contact with the circular arc surface during development and retracts when not developing. 4. The image forming apparatus according to claim 1, wherein the developing device has a positioning roller that abuts on the arc surface.