JPH08137196A - Image forming device - Google Patents

Abstract

PURPOSE: To suppress the generation of image noises corresponding to the winding seam margin of a ribbon-like brush member of a rotary brush on an arbor roller and to obtain good images by determining the winding seam margin and inter-pile distance so as to satisfy specific conditions. CONSTITUTION: The rotary brush 20 is formed by winding the ribbon-like (band- shaped) brush member 21 on the conductive arbor roller of a columnar shape and adhering this member with a conductive adhesive. The ribbon-like brush member 21 is formed by implanting piles P consisting of many pieces of conductive brush hairs (conductive fibers) on a base fabric. The inter-pile distance (s) is expressed by s=L (inter-pile spacing at both ends)/[n(number of pile arrays)-1] when the spacing between the piles P existing at both side edges of the brush member 21 is defined as L and the number of the arrays of the woven piles as (n). The winding seam margin of the band-shaped brush 21 wound around the roller 22 is (d). The winding seam margin 3d is so set as to satisfy the conditions 0.7s<d<1.5s with respect to the inter-pile distance s.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to an image forming apparatus such as a printer.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as an electrophotographic copying machine or a printer, an electrostatic latent image bearing member is charged by a charging device and an electrostatic latent image is formed by imagewise exposing the charged area. Then, the latent image is developed into a visible image, which is transferred to a transfer material and fixed. After the transfer, the developer remaining on the surface of the electrostatic latent image carrier is removed by a cleaning device.

Recently, in response to demands for compactness and cost reduction of the apparatus, various apparatuses without the cleaning apparatus have been proposed. For example, Japanese Patent Laid-Open No. 3-4283 teaches a so-called cleanerless image forming apparatus in which a developing device also serves as a cleaning device. Although various types of charging devices are known,
Broadly speaking, it can be divided into a corona charging device that uses corona discharge and a contact charging device that brings a charging member into contact with an electrostatic latent image carrier. Examples of the contact charging device include a device using a fixed brush, a device using a charging roller member such as a rotating brush, and a device using a belt-shaped charging member that is rotationally driven.

Although a charging device using corona discharge has an advantage that stable charging can be performed, a large amount of ozone is generated, which causes deterioration of a photoconductor or the like which is generally used as an electrostatic latent image carrier, and a human body. Therefore, a contact charging device, which produces a significantly smaller amount of ozone than a corona charging device, is attracting attention (see Japanese Patent Laid-Open No. 61-57956).

Among the contact charging devices, the brush-type charging device is one in which the developer remaining on the electrostatic latent image carrier after transfer is transferred in the case of the above-mentioned cleanerless image forming apparatus. It is convenient for suppressing the generation of so-called memory due to the residual developer that is scattered by the brush in the charging device. Further, among the brush type charging devices, a charging device using a rotating brush has been attracting attention from the viewpoint of charging stability.

The charging rotary brush is manufactured by various methods. Typical examples are strength, productivity, and
To make the desired flocking density, etc., a ribbon-shaped (belt-shaped) brush body in which a large number of piles of conductive brush bristles are planted at intervals on a base member such as a base cloth is spirally wound on a core rod roller. It is often used that is wound into a shape.

[0007]

However, according to the rotary brush in which such a ribbon-shaped brush body is spirally wound around the core rod roller, in the case of the image forming apparatus having the cleaner-less structure, for example, a halftone dot image uniformly dispersed. However, there is a problem that an exposure memory occurs when the ribbon-shaped brush body is wound around the core rod roller, which causes image noise.

[0008] This is because the transfer residual developer is only unevenly scattered due to such a winding margin, so that so-called exposure kick occurs partially and the electrostatic latent image bearing member surface potential is sufficient at that portion. It is thought that this is due to the occurrence of image "unevenness" without any decrease. In relation to this problem, attention is paid to the rotating brush disclosed in Japanese Patent Laid-Open No. 62-135874. This rotary brush is originally a rotary brush used for electrostatic charging or cleaning of residual developer, and the brush bristle packing density at the edge of the ribbon-shaped brush body is approximately doubled at the center of the brush body. Thus, the brush bristle blank portion between the adjacent ribbon-shaped brush bodies is filled on the core rod roller, and thereby the charging performance or the cleaning performance is improved without increasing the rotation speed of the rotary brush. . Although the purpose is different, it is conceivable to employ such a rotating brush to suppress the image noise generation.

However, when such a rotating brush is adopted, the brush bristle density is partially increased, so that the effect of scattering the residual developer by that portion becomes too large, and rather image unevenness occurs. In addition, the amount of injected charge at that portion is too high, which causes uneven charging and eventually unevenness in the image. In view of the above, the present invention charges the surface by a contact charging device having a charging rotary brush in which a ribbon-shaped brush body having a large number of piles of conductive brush bristles planted on a base member is spirally wound around a core rod roller. The electrostatic latent image bearing member thus formed is imagewise exposed to form an electrostatic latent image, the latent image is developed by a developing device to be visualized, and the visible image is transferred to a transfer material. An image forming apparatus for causing the developing device to remove the developer remaining on the electrostatic latent image carrier, to a core rod roller of a ribbon brush body in a rotating brush of the charging device, which has been conventionally generated. It is an object of the present invention to provide an image forming apparatus that does not generate image noise corresponding to the winding margin or is sufficiently suppressed, and can obtain a good image.

[0010]

Means for Solving the Problems The present inventor has conducted extensive research to solve the above problems, and if the winding allowance of the ribbon-like brush body on the core rod roller and the pile planting interval in the rotating brush are close to each other, It has been found that the occurrence of such image noise is suppressed. The present invention is based on this knowledge, and contact charging having a rotating rotating brush for charging in which a ribbon-shaped brush body having a large number of piles of conductive brush bristles planted on a base member is spirally wound around a core rod roller. An electrostatic latent image is formed on the electrostatic latent image carrier whose surface is charged by a device to form an electrostatic latent image, the latent image is developed by a developing device to be visualized, and the visible image is transferred to a transfer material. Then, in the image forming apparatus that causes the developing device to remove the developer remaining on the electrostatic latent image bearing member after the transfer, the winding allowance d of the ribbon brush body of the rotary brush to the core rod roller and The image forming apparatus is characterized in that a distance s between piles satisfies a condition of 0.7 × s <d <1.5 × s.

The ribbon-shaped brush body is not limited thereto, but from the viewpoint of making strength, productivity, flocking density and the like desirable, a ribbon-like brush body having substantially the same structure as a so-called velvety weave is a typical example. Can be mentioned. That is, as schematically shown in FIG. 2, a large number of piles P of conductive brush bristles are woven into a base cloth B1 serving as a base member at intervals, and a ribbon shape is formed at that stage. The ribbon 21 is cut into a ribbon.

In addition, a large number of piles of electrically conductive brush bristles are planted at intervals on a flexible sheet-shaped synthetic resin base member, and ribbons are formed at that stage, or appropriately. It is also possible to cut into a ribbon shape. The ribbon-shaped brush body as described above is not limited thereto, but as shown in FIG. 3, for example, is made of a conductive material such as a conductive metal, a conductive synthetic resin, or an insulating material whose surface is conductively processed, which is rotationally driven. It is spirally wound around the surface of the core rod roller 22, adhered with a conductive adhesive, and formed on the rotating brush 20.

The "roll margin d" in the present invention means, for example, when the brush body 21 of FIG. 2 is used, as shown in FIG. 5, ribbon-shaped brush bodies adjacent to each other on the core rod roller 22. In FIG. 21, reference numeral 21 denotes the mutual distance between the pile P implanted at the edge portion of one brush body and the pile P implanted at the edge portion of the other brush body. The “pile distance s” referred to in the present invention means the brush body 21 of FIG.
As an example, as shown in FIG. 4, the distance L between the piles P at both ends of the brush body is divided by (the number of rows of the pile P, n−1), that is, s = (the distance between the piles at both ends L). ) /
[(Number of pile rows n) -1].

[0014]

According to the image forming apparatus of the present invention, an image is formed similarly to the conventional image forming apparatus. However, after the visible image is transferred onto the transfer material, the developer remaining on the electrostatic latent image carrier is removed by the developing device. Further, in the rotary brush of the contact charging device, the winding margin d of the ribbon-shaped brush body around the core rod roller and the distance s between the piles are 0.7 × s <d <1.5 × s.
Since the condition (1) is satisfied, the image noise corresponding to the winding margin of the core brush roller of the ribbon-shaped brush body in the rotating brush does not occur or is sufficiently suppressed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a printer according to the present invention. This printer has a photosensitive drum 1 in the center. The drum 1 is rotationally driven in the direction of arrow a (counterclockwise) in the figure by a driving device (not shown). A brush charging device 2, an exposure device 3, a developing device 4, a transfer charger 5 and a separation charger 6 are sequentially arranged around the drum.

The brush charging device 2 is a contact charging device using a roller-shaped rotating brush 20 made of a conductive fiber.
The rotating brush 20 comes into contact with the photosensitive drum 1 and is driven to rotate clockwise in the figure, and a DC voltage -1.
3 (kV) is applied, and the surface of the photosensitive drum 1 is set to −8.
It is charged to 00 (V). The rotary brush 20 will be described later in detail.

The exposure device 3 uses a generally known semiconductor laser. Here, the surface of the photosensitive drum 1 charged to -800 (V) is irradiated by a laser beam for the image portion. The light is adjusted to reduce it to -50 (V). The developing device 4 is a one-component developing device. The developing device 4 is supported by a casing 41 and is driven by a drive roller 42 that is rotated in the direction of arrow b (clockwise direction) in the drawing, and has a flexible inner diameter slightly larger than the outer diameter. The developing sleeve 43 is externally fitted, and both ends of the developing sleeve 43 are pressed against the drive roller 42 by the pressing belt member 44 from the inside of the casing 41 to form a slack portion 430 on the opposite side, and the slack portion is attached to the photosensitive drum 1. They are in contact with each other. Further, a metal regulating blade 45 is in contact with the developing sleeve 43 in the casing 41.

The toner T, which is a one-component developer contained in the casing 41, is supplied to the toner conveying roller 47 while being agitated by the agitating member 46 which is rotationally driven counterclockwise in the figure, and the roller 47 is indicated in the figure. The toner T is moved to the developing sleeve 43 side while being rotationally driven in the clockwise direction. The developing sleeve 43 is driven to rotate in the same direction as the driving roller due to frictional force as the driving roller 42 rotates, while the regulation blade 45 frictionally charges the toner T while adhering a certain amount on the developing sleeve 43. The developing sleeve 43 sequentially supplies the toner T to the contact portion with the photosensitive drum 1 by its rotation.

A developing bias voltage of -250 (V) is applied to the developing sleeve 43 from a power source (not shown), and the toner T can be attached to the electrostatic latent image on the photosensitive drum 1 by this bias voltage. Details of the photosensitive drum 1, the toner T used, and the developing sleeve 43 are as follows. Photoreceptor drum 1: Charge generation layer (CGL) made of phthalocyanine and binder resin on an aluminum substrate (drum)
A charge transporting layer (CTL) of about 0.1 μm and a hydrazone derivative and a binder resin of about 18 μm is formed thereon, and each layer is formed by repeating coating by a dipping method and subsequent drying. Toner T: a one-component non-magnetic toner having a negative charging property, which was obtained from the following composition and manufacturing method. Bisphenol A type polyester resin 100 parts by weight Carbon black (Mitsubishi Kasei Co., Ltd. MA # 8) 5 parts by weight Charge control agent (Orient Chemical Industry Co., Ltd. Bontron S-34) 3 parts by weight Wax (Sanyo Kasei Kogyo Co., Ltd. Viscole TS-200) 2.5 parts by weight The above components are kneaded, pulverized and classified according to a commonly known method to give an average particle size of 10 μm to 7 to 13 μm. 80
The toner particles have a wt% distribution. Further, silica particles (Taranox 5 manufactured by Gabosil Co., Ltd.) are added to the toner particles.
00) was added to 0.75 parts by weight for surface treatment. Developing sleeve 43: A stainless steel round bar (diameter 25 mm) was immersed in a nickel electrolytic solution, and an electroforming method was applied thereon to finish the film thickness to about 35 μm. The nip width with the photosensitive drum 1 at the time of development is about 1 to 1.5 mm.

The regulation blade 45 is capable of adhering the toner T to the developing sleeve 43 at an adhesion amount of 0.6 mg / cm ² , a toner layer thickness of about 0.03 mm, and a charge amount of -20 μc / g. Here, the rotating brush 20 of the contact charging device 2 will be further described. The rotary brush 20 is formed by winding a ribbon-shaped (strip-shaped) brush body 21 shown in FIG. 2 around a cylindrical conductive core rod roller 22 as shown in FIG. 3 and adhering it with a conductive adhesive. . The ribbon-shaped brush body 21 is obtained by implanting a pile P made of a large number of conductive brush bristles (conductive fibers) on the base fabric B1, and as shown in FIG. Assuming that the mutual distance between certain piles P is L and the number of rows of woven piles is n, the inter-pile distance s is expressed by the following equation. Further, the winding margin of the belt-shaped brush 21 wound around the roller 22 is d as shown in FIG.

S = L (pile spacing at both ends) / [n (number of pile rows) -1] In this rotating brush 20, the core rod roller 22 has a diameter of 8 m.
m, the brush pile length is 5 mm, and the tip is about 1 m.
It is pressed against the surface of the photosensitive drum 1 by m. Then, with respect to the peripheral speed of the photosensitive drum 1 of 3.5 cm / sec, the peripheral speed is 1 to 4 times the peripheral speed of the photosensitive drum so as to move in the same direction at the mutual contact portion (to move in the driven direction). It is driven to rotate. The winding margin d is set within the following range with respect to the pile-to-pile distance s.

0.7s <d <1.5s According to the printer described above, the surface of the photosensitive drum 1 that is driven and rotated is uniformly charged to the surface potential -800 (V) by the brush charging device 2. Image exposure is performed on the charged area by the exposure device 3 to form an electrostatic latent image.
The surface potential of the exposed portion drops to about -50 (V). The electrostatic latent image thus formed is developed in the developing device 4 under a developing bias voltage of -250 (V) to become a toner image. In this development, the toner T on the developing sleeve 43 adheres to the electrostatic latent image with a potential difference ΔV = 200 (V).

The toner image thus formed is transferred by the transfer charger 5 onto the paper 7 supplied from the transfer paper supply means (not shown), and the paper 7 after the transfer is separated from the photosensitive drum 1 by the separation charger 6. Then, the toner image is transferred to a fixing device (not shown), and then the toner image is fixed and then discharged. However, all the toner on the photosensitive drum 1 is not transferred onto the sheet 7 by the transfer charger 5, and 10% to 20% of the toner usually remains on the photosensitive drum 1 as residual toner. This residual toner is charged by the charging device 2.
After being subjected to charging by the image forming apparatus and, if necessary, image exposure by the exposure device 3, the toner reaches the developing device 4 again, and the residual toner in the non-image portion is collected by the developing sleeve 43.

The recovery of the toner will be described in more detail. The photosensitive drum 1 is also used for the portion having the residual toner.
The upper surface potential is almost uniformly charged by the charging device 2 and is about -800 (V). On the other hand, a developing bias voltage of −250 (V) is applied to the developing sleeve 43. Therefore, the residual toner T in the non-image portion on the drum 1 has a potential difference of about 550 (V) and is applied to the developing sleeve 4
The force of shifting to the 3 side works, and at the same time, the scraping effect of the residual toner by the developing sleeve 43 is also assisted, and the residual toner in the non-image portion is collected and removed to the developing sleeve 43 side.

Prior to this, the residual toner remaining on the photosensitive drum 1 is disturbed by the rotating brush 20 in the charging device 2 and scattered so as not to remain as an afterimage on the photosensitive drum 1. The mutual relationship between the winding margin d of the ribbon-shaped brush body 21 and the distance s between the piles of the rotary brush 20 is set so as to satisfy the condition of 0.7 s <d <1.5 s. The image noise corresponding to the winding margin of No. does not occur, or the occurrence thereof is sufficiently suppressed, so that a good image can be obtained.

Next, using a dot image sample of 1 on-1 off at a density of 300 dpi, the interrelationship between the winding margin d and the pile distance s was varied within the range of 0.7 s <d <1.5 s. Experiments in which the image noise was visually evaluated for each of the formed images by changing the
8), and an experiment in which the winding margin d is selected from the range other than the above range, image formation is performed in the same manner, and the image noise of each of the formed images is visually evaluated (Comparative Examples 1 to 6).
Will be described. The relative speed ratio of the peripheral speed of the rotary brush 20 to the peripheral speed of the photosensitive drum 1 is 1 to 4 in all cases.
Selected from a range of.

The evaluation result of the image noise is “◯” when no winding noise is recognized, and “Δ” when the winding noise is recognized but is at an acceptable level when the closer inspection is performed,
The following table shows ranks marked with "x" when the level of noise was clearly unacceptable. Relative Velocity Ratio s dd / s Noise Evaluation Experimental Example 1 2 0.7 0.6 0.86 ○ Experimental Example 2 2 0.7 0.8 1.14 ○ Experimental Example 3 2 0.7 1 1.43 △ Experimental Example 4 3 1 0.8 0.8 ○ Experimental Example 5 3 1 1.2 1.2 ○ Experimental Example 6 3 1 1.4 1.4 △ Experimental Example 7 4 1.2 1 0.83 △ Experimental Example 8 4 1.2 1.5 1.25 ○ Comparative Experimental Example 1 2 0.7 1.5 2.14 × Comparative Experimental Example 2 2 1 2 2 × Comparative Experimental Example 3 3 1.2 0.6 0.5 × Comparative Experimental Example 4 3 1.2 2 0.67 × Comparative Experimental Example 5 4 1 0.6 0.6 × Comparative Experimental Example 6 4 1 1.7 1.7 × Also, the image noise evaluation rank "○" in the above table was 4.
FIG. 6 shows a graph in which the value of the image noise level is plotted against d / s by digitizing 5, “Δ” into 3, and “x” into 1.5. From the above results, the level at which the winding margin d and the pile-to-pile distance s are 0.7 is that the noise is not recognized or is acceptable even if the noise is recognized.
It can be seen that the image is formed using a rotating brush that satisfies s <d <1.5s.

[0028]

According to the present invention, contact charging having a rotating charging brush in which a ribbon-shaped brush body having a large number of piles of conductive brush bristles planted on a base member is helically wound around a core rod roller. An electrostatic latent image is formed on the electrostatic latent image carrier whose surface is charged by a device to form an electrostatic latent image, the latent image is developed by a developing device to be visualized, and the visible image is transferred to a transfer material. An image forming apparatus for causing the developing device to remove the developer remaining on the electrostatic latent image bearing member after the transfer, and a ribbon-shaped brush body in a rotating brush of the charging device, which has been conventionally generated. It is possible to provide an image forming apparatus in which the image noise corresponding to the winding margin around the core rod roller does not occur, or the occurrence of the image noise is sufficiently suppressed, so that a good image can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a printer which is an embodiment of the present invention.

FIG. 2 is a diagram showing an outline of a structural example of a ribbon-shaped brush body in one embodiment of the present invention.

FIG. 3 illustrates a method for forming the ribbon-shaped brush body shown in FIG. 2 into a rotary brush.

FIG. 4 is a diagram showing how to determine a distance between piles of a ribbon-shaped brush body.

FIG. 5 is an enlarged schematic cross-sectional view of a part of a ribbon-shaped brush body on a rotating brush.

FIG. 6 is a graph in which the value of the image noise level is plotted against the value of the ratio of the winding margin d to the distance s between the piles.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoconductor drum (electrostatic latent image carrier) 2 Contact charging device 20 Rotating brush 200 Power supply 21 Ribbon-shaped brush body P pile 22 Conductive core rod roller B1 Base cloth L Pile on both side edges of ribbon-shaped brush body 21 Mutual spacing of P n Number of pile rows woven in the ribbon-shaped brush body 21 s Distance between piles d Winding margin

Claims (1)

[Claims] 1. A surface is charged by a contact charging device having a rotating charging brush in which a ribbon-shaped brush body having a large number of piles of conductive brush bristles planted on a base member is spirally wound around a core rod roller. The electrostatic latent image bearing member thus formed is imagewise exposed to form an electrostatic latent image, the latent image is developed by a developing device to be visualized, and the visible image is transferred to a transfer material. In an image forming apparatus that causes the developing device to remove the developer remaining on the electrostatic latent image carrier, the winding margin d of the ribbon brush body of the rotating brush to the core rod roller and the distance s between piles are An image forming apparatus satisfying the condition of 0.7 × s <d <1.5 × s.