JPH0546015A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] In an image forming apparatus in which the distance between the image bearing member and the developing roller of the developing unit is kept constant without using a spacer roller, especially against the pressure applied to the image bearing member by the cleaning blade. Therefore, the above-mentioned distance can be maintained. A means for elastically biasing one or several developing rollers in the direction of the center of rotation of the image carrier, and elastic means in a predetermined direction so as to sufficiently oppose the pressing action from the cleaning blade side of the image carrier. And a means for biasing the position is provided.

Description

Detailed Description of the Invention

[0001]

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus using an electrostatic transfer process such as an electrostatic copying machine and a printer.

[0002]

2. Description of the Related Art A plurality of developing devices are arranged around an image carrier, which is usually formed in the shape of a rotating cylinder, and electrostatic latent images formed on the surface of the image carrier in a predetermined order. In an image forming apparatus that forms a color image by adhering to a sheet, jumping development that performs development at an appropriate interval between an image carrier that carries a latent image and a developing roller of each developing device that supplies toner. In this case, it is necessary to maintain an appropriate distance between the image carrier and the developing roller. Especially, in a color image forming apparatus in which a slight discrepancy in image position is recognized as a color misregistration, the above distance is increased. It is necessary to maintain accuracy.

In this type of apparatus, as means for maintaining the distance between the image bearing member and the developing roller, spacers having a radius increased by a predetermined gap are arranged at both ends of the developing roller, and the rollers are A member that contacts the image carrier to maintain a predetermined distance between the image carrier and the developing roller, a side plate that supports the image carrier is provided with a positioning member having a position-adjustable bearing, and the positioning is performed. There has been proposed a device in which a developing roller is brought into contact with a bearing portion of a member and brought into contact therewith.

By the way, in the case of the former structure, the toner or the like scattered in the apparatus adheres to the contact portion of the image carrier and the spacer roller which abuts against the image carrier, and this further causes pressure and friction between the two. There is a risk of fusing due to heat or the like to change the distance between the image carrier and the developing roller, which may lead to deterioration of image quality. Therefore, in the color image forming apparatus with severe image conditions, The latter, which does not use spacer rollers, is now being used.

However, on the other hand, since such a member does not press the image carrier from the developing roller side,
When using a cleaner that presses the cleaning blade against the image bearing member, when the pressure contact state of the cleaning blade with the image bearing member changes, the play between the shaft of the image bearing member and its bearing, the developing roller and the positioning member, There is a problem in that image quality is deteriorated due to looseness between the electrostatic latent images to be written and a decrease in accuracy of the distance between the image bearing member and the developing roller due to looseness between them.

The present invention has been made to cope with such a situation, and in the above-mentioned type of image forming apparatus which does not use the spacer roller on the developing roller side,
The developing roller is brought into contact with the bearing portion of the positioning member provided on the side plate that supports the image carrier, presses each developing roller toward the rotation center of the image carrier, and pressurizes the cleaning blade to the image carrier. By pressing the image bearing member rotating shaft toward the bearing with a sufficiently large force, the pressure acting from the cleaner side and the resulting vibration of the image bearing member are well resisted to obtain a high quality image. It is an object of the present invention to provide such an image forming apparatus.

[0007]

[Constitution of the invention] [Prior art and problems to be solved]

In order to achieve the above-mentioned object, the present invention is an image forming apparatus comprising a rotating cylindrical image carrier, a developing device and a cleaner arranged in the vicinity thereof, and the image carrier supports the image carrier. In an image forming apparatus which is attached to a positioning and holding frame via a bearing and in which the developing roller in the developing device is positioned with respect to the center of rotation of the image carrier, the developing roller is elastically moved toward the center of rotation of the image carrier. And a means for biasing the image bearing member in the radial direction of the rotation axis of the image bearing member.

With this structure, the side plate supporting the image bearing member is provided with a positioning member having a bearing portion whose position can be adjusted, the developing roller is brought into contact with the bearing portion of the positioning member, and the spacer roller is removed. In an image forming apparatus that maintains the distance between the image carrier and the developing roller without using it, it is possible to compensate for the pressure applied to the image carrier by the cleaning blade and maintain the interval at a predetermined level at all times. Become.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a side view of an image forming apparatus showing an embodiment of the present invention, particularly showing only an image carrier, a charger, a developing device and a cleaner portion. Members such as writing means that are not directly related to the present invention are omitted.

Reference numeral 2 in the drawing denotes a rotating cylindrical image bearing member having an axis line in the direction perpendicular to the paper surface, and a developing device 3Y containing, for example, yellow toner, magenta toner, cyan toner and black toner, respectively, in the vicinity thereof. 3M, 3
C and 3B are arranged, and the developing roller 1 is provided in each developing device.
It is assumed that Y, 1M, 1C, and 1B are provided, and these developing rollers sequentially supply toner to the latent images on the image carrier 2 as needed.

A cleaner 4 having a cleaning blade is provided at a predetermined position in the vicinity of the image carrier in order to remove the residual toner remaining on the image carrier through the well-known development and transfer processes.

On the developing roller 1Y of the developing device 3Y, a positioning member 6 having a bearing portion for positioning the roller is provided outside the positioning and holding frame of the image carrier 2 (hereinafter referred to as "positioning member 6"). The configuration of each developing roller 1M, 1C
All are the same for 1B, so unless you need
Only the developing device 3Y will be described below), and a spring 9 is arranged between the shaft of the developing roller 1Y and the positioning and holding frame of the image carrier 2 so that the developing roller 1Y can move the image carrier 2Y. Will be positioned through the member 6 toward the center of rotation.

Further, a spring 10 is suspended between the shaft 8 of the image carrier 2 and a proper position of the positioning frame in a radial direction so as to oppose with a force sufficiently larger than the pressing action of the cleaner 4 against the image carrier. There is.

With this configuration, even if the contact state of the cleaning blade with the image carrier changes, the image carrier itself and each developing device are biased to one side, so the image carrier By vibrating the image carrier due to backlash between the shaft and its bearing, and between the developing roller and the positioning member, the latent image to be written is prevented from blurring or the distance between the image carrier and the developing roller is prevented from changing. You can get good quality images.

FIG. 2 shows another embodiment of the present invention. Basically, the image carrier 2 and the developing rollers 1Y, 1M of the developing devices of the same apparatus as the apparatus of FIG. 1 are used. 1C, 1
B, only the spring 9 that pulls them is shown.

In this apparatus, each spring 9 is suspended between the shaft 8 of the developing roller and the shaft of the image carrier 2, and the pulling force of these springs presses the cleaner 4 against the image carrier 2. It shall have sufficient force to counteract the action.

With such a configuration, it can be easily expected that the same operation as that of the above embodiment can be expected. Further, this configuration can reduce the number of springs.

FIG. 3 is a front view of an essential part showing still another embodiment, in which an inter-shaft member 16 is arranged between the shaft of the image carrier 2 and the shaft of each developing roller. In addition to fixing the distance, a spring 14 is arranged between the bearing 11 on the image carrier side and the bearing 12 on the developing roller side, and the action of this spring is made sufficiently larger than the pressing force on the image carrier by the cleaning blade. There is. Even with such a configuration, the same operation as that of each of the above-described embodiments can be achieved.

FIG. 4 shows another embodiment, in which each developing device is biased by a spring 15 from behind each developing device 3Y, 3M3C and 3B to bias the developing roller, The play between the positioning member and the positioning member is removed.

FIG. 5 shows still another embodiment, in which the direction in which the resultant force of the pressure applied by the cleaner 4 and the pressing force of the developing roller by the spring 15 acts is A, and the image is repelled by the bounce 10 in this direction. A pressing force is applied to the shaft of the carrier 2. With this configuration, it is possible to prevent the play between the shaft and the bearing of the image carrier, the vibration of the image carrier, and the influence of uneven rotation with a smaller pressure.

[0022]

As described above, according to the present invention, the shaft of the rotating cylindrical image carrier is attached to the positioning holding frame, and the developing roller of the developing device carries the image carrying member of the positioning holding frame. In an image forming apparatus configured to be positioned with respect to the center of rotation of the body, each developing roller is elastically biased in the direction of the center of rotation of the image carrier, and the image carrier rotation axis is aligned with the image carrier of the cleaner. Since it is elastically biased in the radial direction with a sufficiently large force so as to oppose the applied pressure of the cleaning blade, even if the contact state of the cleaning blade with the image carrier changes, the latent image that causes the vibration is generated. Image blurring and changes in the distance between the image bearing member and the developing roller can be minimized, and particularly when applied to a color image forming apparatus with severe image conditions, it has a remarkable effect in obtaining a good quality image. .

[Brief description of drawings]

FIG. 1 is a side view of a main part of an image forming apparatus showing an embodiment of the present invention.

FIG. 2 is a side view of an essential part of an image forming apparatus showing another embodiment.

FIG. 3 is a front view of a main part of an image forming apparatus showing still another embodiment.

FIG. 4 is a side view of a main part of an image forming apparatus showing still another embodiment.

FIG. 5 is a side view of an essential part of an image forming apparatus showing still another embodiment.

[Explanation of symbols]

 1Y, 1M, 1C, 1B Developing roller 2 Image carrier 3Y, 3M, 3C, 3C Developing device 4 Cleaner 5 Charging device 6 Positioning member 9, 10 Spring

Claims (4)

[Claims] 1. An image forming apparatus comprising a rotating cylindrical image carrier, a developing device and a cleaner disposed in proximity to the image carrier,
In the image forming apparatus, the image carrier is attached to a positioning and holding frame via a bearing supporting the image carrier, and the developing roller in the developing device is positioned with respect to the rotation center of the image carrier. An image forming apparatus comprising means for elastically biasing the image bearing member toward the center of rotation of the image bearing member, and means for biasing the image bearing member in the radial direction of its rotation axis. 2. The image forming apparatus according to claim 1, wherein a plurality of developing devices are provided. 3. The elastic biasing action of the means for biasing the image bearing member is sufficiently large with respect to the far pressure applied to the image bearing member of the cleaner, according to claim 1. Image forming device. 4. The method according to claim 1, wherein the means for displacing the image carrier coincides with the direction of the total force of all the forces applied in the radial direction of the image carrier. Image forming device.