JP2000321934A - Cleaning device for image forming apparatus - Google Patents

Abstract

An object of the present invention is to prevent defective cleaning due to a shortage of an external additive which also serves as a polishing agent for a developer used in an image forming apparatus. A means for detecting an amount of toner consumed by a transfer material and a means for supplying an external additive to a developing means according to a result of the detection are provided.

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 using an electrostatic transfer process, such as an electrostatic copying machine and a printer, and more particularly to a cleaning device for the image forming apparatus.

[0002]

2. Description of the Related Art A known image forming apparatus which repeats a process of applying a toner to an electrostatic latent image formed on the surface of an image carrier to form a toner image and transferring the toner image to a transfer material such as paper,
At the time of transfer, it is difficult to transfer all the toner from the image carrier side to the transfer material, and it is inevitable that a part of the toner remains on the image carrier. Sufficient removal is an essential requirement for obtaining a good quality image.

Various means have been conventionally proposed for reducing the residual toner. One sharp edge of a cleaning blade made of an elastic material such as urethane rubber is provided on the surface of the image carrier. It is well known that it is widely used because it is configured to abut on the downstream side of the transfer site to scrape off the residual toner, or it is small and simple in construction and has excellent toner removal function. It is as follows.

When an organic semiconductor is used as a photosensitive layer on the surface of the image carrier and Teflon or the like is dispersed for hardening the surface, the friction between the image carrier and the cleaning blade is prevented from becoming excessive, and the chargeability is reduced. To make
It has been proposed to roughen the surface of an image carrier at the beginning of use.

However, since the cleaning blade is in contact with the image carrier during the image forming operation, the surface of the cleaning blade is polished, and the surface is smoothed. Inevitably tend to. In particular, when a thinner having a small particle size (for example, 8 μm or less) is used, this tendency is remarkable, and the surface of the image carrier is smoothened deeply, and the cleaning failure easily occurs due to the occurrence of blade turning and chatter vibration. .

In order to avoid such a situation, an external additive having a particle diameter of 0.5 μm or more and having the function of forming the surface of the image carrier itself into an appropriate rough surface is used for the toner having a small particle diameter. It has been proposed to externally add to the surface to form a mat.

However, during the transfer, when a transfer bias is applied to the transfer member at the transfer portion, the external additive also has polarity, so that the external additive adheres to the image carrier depending on the charging potential of the image carrier. Since the amount differs and the amount of transfer to the transfer material also differs, the amount of the external additive coming to the cleaning delivery also differs.

For this reason, when an image in which the external additive easily adheres to the image carrier continues, the external additive in the developing device is reduced, the external adding function is reduced, and the above-described problem is likely to occur.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to cope with such a situation, and suppresses an increase in friction between a cleaning blade and an image carrier to prevent the cleaning blade from being turned up or having a defective cleaning. It is an object of the present invention to provide a cleaning device for an image forming apparatus, which can prevent the occurrence of an image and stably maintain a good cleaning function for a long period of time.

[0010]

In order to achieve the above-mentioned object, the present invention provides a moving image carrier, a developing means for electrostatically forming a toner image on the surface of the image carrier, and a method for forming the toner image on a surface. Transfer means for electrically transferring to a transfer material, and a cleaning means for removing residual toner remaining on the image carrier even after the transfer,
In an image forming apparatus provided with a unit for supplying an external additive to the developing unit, a unit for detecting an amount of toner consumed by the transfer material and a unit for supplying the external additive to the developing unit based on a detection result are provided. (1) The image forming apparatus according to (1), wherein the image forming apparatus is a multicolor image forming apparatus including a plurality of developing units. The image of claim 1, wherein the external additive has a polarity opposite to that of the toner and has a particle diameter of 0.5 μm or more. A cleaning device (3) for the forming device.

With this configuration, it is possible to prevent the turning of the blade or the cleaning failure, increase of the friction between the image carrier and the blade, increase of the torque of the image carrier, and the like, and perform stable and good cleaning for a long period of time. Can be.

In the present invention, the amount of toner supplied from the toner supply portion to the developing device of the image forming apparatus is detected, and the consumption of the external additive is calculated from the number of images and the supplied amount. An external agent replenishing member capable of replenishing the external additive is provided. As a result, an image forming apparatus capable of avoiding blade turning and poor cleaning and constantly performing good cleaning stably can be obtained.

[0013]

FIG. 1 is a schematic side view of the configuration of a color copying machine showing an embodiment of the present invention. The copier 1 has a rotating cylindrical image carrier 2 having an axis perpendicular to the paper surface. Around the periphery, a primary charger 3, and a developing device containing yellow toner, cyan toner, magenta toner, and black toner, respectively. A developing device 4 including devices 4Y, 4C, 4M, and 4BK, a pre-electrification charger 6, and a cleaning device 7 are provided.

Further, a means for forming an electrostatic latent image on the image carrier is provided in the traveling direction of the image carrier 2 and on the downstream side of the primary charger 3. This will be described below.

Normally, an image signal coming from a document 25 placed on the top surface of the apparatus
The image signal processing circuit 28 decomposes the image signal into a large number of pixels and outputs a photoelectric conversion signal corresponding to the density of each pixel.
Is converted into a pixel image signal of an output level corresponding to the density of the pixel, and is sent to the pulse width modulation circuit 29.

The laser drive pulse output from the Pari width modulation circuit 29 causes the semiconductor laser 30 to emit light for a time corresponding to the pulse width.

More specifically, for a high density pixel, the low density is exposed for a longer time in the main scanning direction (direction substantially parallel to the axis of the image carrier) than the sparse, and the dot size of the latent image is corresponding to the density of the pixel. Differently, the high-density pixels naturally consume more toner than the low-density pixels. "Figure 2"
In (d), low, medium, and high density latent electrostatic images are represented by L and L, respectively.
Indicated by M and H.

The laser beam 30a emitted from the laser 30 is applied to a polygon mirror 31, an f-Θ lens 32, and a reflection mirror 33.
By this time, by this time, the primary charger 3 forms an image on the surface of the image carrier 2 which is charged to one leaf, thereby forming an electrostatic latent image.

A transfer drum 5 is provided near the image carrier 2. A transfer sheet 8 made of a ferroelectric material extends on the transfer drum, and a transfer member 11 is disposed inside the transfer drum 5 at a transfer site where the image carrier 2 and the transfer drum 5 are cut off. It is.

Hereinafter, the color image forming scan will be briefly described. When a gradual increase of the yellow component color is formed on the image bearing member 2 on the document, and the latent image reaches the developing site where the developing device 4 is provided by the rotation of the image bearing member,
A developing device 4Y containing a yellow toner in the developing device 4 takes an operating position close to the image carrier, and toner is applied to the latent image to form a yellow toner image.

When the yellow toner image reaches the transfer portion where the transfer drum 5 is disposed close to the transfer portion by the movement of the image carrier, the transfer material taken out of the cassette 16 by the paper feed roller 17 by this time. P is the runway 1
8, the transfer sheet is cut into the transfer drum 5 which is cut off on the image carrier 2, and the transfer sheet is formed by the attraction charger 9 provided on the transfer drum side and the conductive roller 10, which is located opposite to the charger 9. After that, it is rotated integrally with the transfer drum and reaches the transfer portion. Reference numeral 24 denotes a cassette for temporarily holding a transfer material when forming a double-sided copy.

When the transfer material P adsorbed on the transfer drum 5 reaches the transfer site, a transfer bias is applied to the transfer member 11, and the yellow toner image on the image carrier side is transferred by the action of the electric field formed thereby. And the transfer drum then travels as it is.

After the transfer, the residual toner on the image carrier 2 is removed by the cleaning device 7, the surface of the image carrier is charged again by the primary charger 3, and a latent image of a cyan component color is formed on the charged surface. .

When the latent image of the conoscian component color reaches the developing site, the developing device 4 holding the cyan toner in the developing device
C moves to the operating position and applies cyan toner to the latent image to form a cyan toner image.

Further, when the cyan toner image reaches the transfer portion, the yellow toner image portion of the transfer material on the transfer drum 5 reaches the transfer portion by this time, and a transfer bias is applied to the transfer member 11. Then, the cyan toner image is superimposed and transferred on the yellow toner image.

Thereafter, similarly, a magenta toner image and a black toner image are sequentially superimposedly transferred onto the transfer material.

After the transfer of the transfer material, the transfer material is discharged at the positions of the charge-removing chargers 12 and 13, separated from the transfer drum 5 by the separation claws 14, passed through the transport path 19, and fixed to the fixing roller 20 and the pressure roller. 221, where the toner is heated and pressurized to melt the respective color toners to form a color image, fixed on a transfer material, and discharged to a paper discharge tray 23 via a discharge roller 22. . Reference numeral 15 denotes an AC corona discharger for preventing image quality deterioration due to peeling discharge at the time of separation.

In such an apparatus, in order to supply the external additive in an amount corresponding to the image ratio of the recording material, it is necessary to know the amount of toner supplied from the toner supply portion to the developing device. The amount detecting means will be described. The output signal of the pulse width modulation circuit 29 is inputted to one of the leading terminals of the AND gate 47, and the clock pulse of the clock pulse generator 48 (the pulse shown in FIG. 2B) is inputted to the other of the leading terminals. .

Thus, from the AND gate 47, as shown in FIG. 2 (c), corresponding to the pulse widths L, M and H based on the image density difference shown in FIG. 2 (d).
The number of clock pulses corresponding to the pulse width, that is, the image density, is output.

The number of clock pulses is integrated by the counter 49 for each pixel to calculate the number of video counters (A4 maximum video count is 3707 × 1).
0 ^6). Therefore, the video count from the counter 49 corresponds to the amount of toner required to form a toner image of one document.

In this embodiment, an external additive having a polarity opposite to that of the toner and having a function of matting the surface of the image carrier itself is used, and this is easily developed in a white image area.
When the density of each pixel is low, that is, when the L state shown in FIG. 2D is large, the external additive is supplied to each developing unit. As for the external additive, an external additive replenishing tank may be provided in a portion located in a replenishing tank for storing toner of each color and successively replenishing the toner to the developing device.

The number of clock pulses is integrated, and this is [(maximum number of chlorochrome pulses) 10]> (number of clock pulses). External additives are replenished accordingly. That is, clock pulses are integrated until a toner image of one document is formed, and the value at this time is set to K, and this value and the external additive consumption reference value K
1 and the external additive is supplied when K> Kl.

As described above, since the replenishment amount of the external additive having a matting function can be adjusted by the image ratio and the replenishment amount can always be replenished, it is possible to prevent the blade from being turned over due to excessive smoothing and the cleaning failure, Further, an increase in friction between the image carrier and the cleaning blade, an increase in the torque of the image carrier, and the like are prevented, so that good cleaning can be stably performed.

The case where the present invention is applied to a color image forming apparatus has been described above. However, it is easily understood that the present invention is not limited to this and can be applied to a monochrome image forming apparatus. By the way.

[0035]

As described above, according to the present invention,
After toner is applied to the electrostatic latent image formed on the elementary image carrier to form a toner image, and the toner image is transferred to a transfer material, residual toner on the image carrier is removed by a cleaning blade, and toner is removed. In an image forming apparatus configured to supply an external additive, the external additive itself is provided with a grinding function, the replenishment amount is controlled by an image density ratio, and the consumption amount of the external additive by an image is kept constant. By doing so, the friction between the image carrier and the cleaning blade can be effectively increased, thereby effectively preventing the occurrence of turning over of the blade and poor cleaning, and performing good cleaning stably for a long period of time. effective.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a method of counting image density information by a counter of the above device.

FIG. 3 is a flowchart showing the operation of the above device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image carrier 3 Primary charger 4 Developing device 5 Transfer drum 9 Adsorption charger 11 Transfer member 14 Separation claw 16 Cassette 20 Fixing roller 23 Discharge tray 25 Document 27 Image sensor 28 Image signal processing circuit 29 Pulse width Modulation circuit 30 Laser 31 Polygon mirror 32 f / Θ lens 33 Reflecting mirror 49 Counter

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[Procedure amendment]

[Submission date] June 4, 1999 (1999.6.4)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

FIG. 3

Claims (3)

[Claims] A moving image carrier; developing means for electrostatically forming a toner image on the surface of the image carrier; transfer means for electrostatically transferring the toner image to a transfer material; A cleaning unit for removing residual toner remaining on the image carrier; and an image forming apparatus including a unit for supplying an external additive to the developing unit, wherein a unit for detecting an amount of toner consumed by the transfer material; And a means for supplying an external additive to the developing means based on the detection result. 2. An image forming apparatus according to claim 1, wherein said image forming apparatus is a multicolor image forming apparatus having a plurality of developing means.
A cleaning device for an image forming apparatus according to the above. 3. The image forming apparatus according to claim 1, wherein the external additive has a polarity opposite to that of the toner and has a particle diameter of 0.5 μm or more. Cleaning device.