JP2002207397A - Paper feeder and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide filming and fusing of toner on a latent image carrier on the assumption that a charging device for superimposing an AC component on a DC component and a developing device of a one-component contact type are used. Provided is an image forming apparatus having a configuration capable of preventing occurrence of a defective image by preventing the image formation. SOLUTION: After the surface of the latent image carrier is uniformly charged by a charging device brought close to the surface, the electrostatic latent image formed on the latent image carrier is subjected to visible image processing by one-component contact development. In an image forming apparatus having a process of transferring a toner image onto recording paper, a static friction coefficient (μs) of the surface of the latent image carrier
Is set to 0.5.

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 a copying machine, a printer, a facsimile machine, and a printing machine, and more particularly, to a structure for preventing occurrence of a defective image on a latent image carrier. .

[0002]

2. Description of the Related Art In an image forming apparatus, after a latent image carrier is uniformly charged by a charging device, an image is written by a writing device or the like to form an electrostatic latent image corresponding to the image. The latent image is subjected to visible image processing by toner supplied from the developing device. The visible image is transferred to recording paper or the like by a transfer device, and then fixed by a fixing device. The untransferred toner may remain on the latent image carrier after the transfer, and the image forming apparatus is configured to remove the residual toner by a cleaning device.

Although most of the toner is removed by the cleaning device, a very small amount of the toner may not pass through the cleaning device without being removed. The latent image carrier that has not been completely cleaned is once again subjected to uniform charging by the charging device. However, depending on the configuration of the charging device, uniform charging may not be possible.

There are two types of charging devices: a corona charging type, which is a type not contacting the latent image carrier, and a contact charging type, in which a charging member is brought into direct contact with the surface of the latent image carrier. In the case of the corona charging type, relatively uniform charging is possible because it is hardly affected by the toner remaining on the latent image carrier,
There is a problem that a large amount of ozone is generated. The contact charging method has the advantage that the amount of ozone generated is small because air discharge is not performed.However, since it is in direct contact with the latent image carrier, a contact mark remains or the toner that has not been cleaned is charged. There is a problem that charging unevenness occurs due to adhesion to the surface of the device and fouling.

In order to solve the problem in the contact charging type in which the charging member is brought into direct contact with the latent image carrier, a small gap is formed between the surface of the latent image carrier and the surface of the charging member to form a non-contact relationship. There is a proximity charging type.

FIG. 4 shows a configuration used in this type. In the configuration shown in FIG. 4, a conductive elastic material such as hydrin rubber provided on the outer periphery of a metal core is provided on the peripheral surface of the latent image carrier A. A roller-shaped charging member B is disposed.
At both ends in the axial direction, an insulating tape or the like is wound so as to be in contact with the surface of the latent image carrier A and form a minute gap H between the surface of the latent image carrier A and the charging member B. This is a configuration in which a spacer ring portion B1 is provided. Charging member B is spring C
The latent image carrier A is urged toward the latent image carrier A by such an elastic member, so that the minute gap H can be maintained.

[0007] When the DC component is the only voltage component applied in order to ensure charging uniformity in the proximity charging system, charging is performed by discharging through a minute gap. The condition may be affected. For this reason, the surface state of the latent image carrier A and the charging member B opposed thereto, for example, the discharge distance affected by the gap distance between the latent image carrier surface and the charging member changes depending on the surface roughness. However, uneven charging and abnormal charging occur. Therefore, it is necessary to strictly control the assembling accuracy and the surface state of these opposing members, which leads to an increase in component costs and processing costs. There is known a method of superimposing a peak-to-peak (AC) voltage of twice or more of a charging voltage on a DC voltage in order to prevent an increase in component cost and processing cost.

[0008] In addition to the configuration using a single color toner, the image forming apparatus has a configuration that forms a multicolor image such as a full color image using a multicolor toner. In the case of forming a full-color image, an electrostatic latent image corresponding to the color-separated image is formed on the latent image carrier, and the electrostatic latent image is a toner of a color complementary to the color-separated color. , And the operation of temporarily transferring the visible image to the intermediate transfer member is repeated for each color, and the image superimposed on the intermediate transfer member is collectively transferred to recording paper or the like. One of the developing methods used when forming a multicolor image is a one-component contact method in which a one-component toner is used and the toner is brought into contact with the surface of the latent image carrier to adhere to the electrostatic latent image. .

[0009]

When the above-described charging method is used, particularly in a method in which an alternating current component is superimposed on a direct current component to charge the toner, the toner tends to remain on the surface of the latent image bearing member. Filming due to the converted toner is likely to occur.

The following points can be considered as a mechanism of occurrence of filming due to superimposed charging. At the time of discharge in the form of aerial discharge including the proximity charging type, a phenomenon is seen in which the collision of electrons generates active groups on the surface of the resin or the like at the collision and increases the adhesive force. In addition, a phenomenon in which functional groups having high reactivity or polarity are generated on the surface of a resin or the like due to the effect of ozone or ultraviolet light generated secondarily in addition to the collision of electrons, and the wettability and reactivity of the surface are enhanced. Therefore, the toner easily adheres to the surface of the latent image carrier due to the action of the adhesive force due to the wettability on the surface of the latent image carrier,
It can be inferred that filming occurs due to deposition and thinning of this.

Filming tends to cause image deletion in a high-temperature and high-humidity environment, and the coefficient of static friction (μs) on the surface of the latent image carrier
Therefore, when the cleaning is performed using the cleaning blade that contacts the surface of the latent image carrier, the blade is likely to be turned up, thereby shortening the life of the latent image carrier.

In image formation in which an intermediate transfer process is performed on an intermediate transfer member, since a two-stage transfer process is performed from the latent image carrier to the intermediate transfer member and from the intermediate transfer member to the recording paper, the character portion is not inserted ( Insect worms) and toner dust (a state in which toner adhering to the periphery of an image portion is scattered) occur, causing transfer failure, and a defective image can be obtained.

Conventionally, it has been proposed to manage the static friction coefficient (μs) of a latent image carrier for the purpose of solving problems at the time of image formation in which an intermediate transfer process is performed (for example, Japanese Patent Laid-Open No. 6-332324). No., JP-A-56-15477
No. 8). JP-A-6-332324 discloses that the static friction coefficient (μs) sets a relationship such that latent image carrier <intermediate transfer member <recording paper (transfer paper). Discloses a configuration in which a low friction coefficient material is applied to the surface of a latent image carrier.

However, when the one-component contact method is used, if the static friction coefficient (μs) of the latent image carrier is too low, the image formed on the image carrier has no image (dots, characters, lines, etc.). (A phenomenon in which a part of the data is missing).

In the one-component contact system, a thin toner layer is formed on the surface of a developing roller, and the thinned toner is brought into contact with the surface of the latent image carrier to form an electric field between the electrostatic latent image and the toner. And a method in which toner is transferred to an electrostatic latent image by an adhesive force to a latent image carrier. For this reason, in the development using the one-component contact type, since the developing roller is in direct contact with the surface of the latent image carrier, the static friction coefficient (μ
If s) is set too low, the toner image held on the surface of the latent image carrier is likely to be scraped off by the developing roller.

An object of the present invention is to provide a conventional image forming apparatus, in particular, a charging apparatus for superimposing an alternating current component on a direct current component and a developing device of a one-component contact type. An object of the present invention is to provide an image forming apparatus having a configuration capable of preventing the occurrence of a defective image by preventing the filming of the toner.

[0017]

According to the first aspect of the present invention,
After the surface of the latent image carrier is uniformly charged by a charging device capable of superimposing a DC component and an AC component, the electrostatic latent image formed on the latent image carrier is subjected to visible image processing by one-component contact development. In an image forming apparatus having a process of transferring an image to recording paper, the upper limit of the static friction coefficient (μs) of the surface of the latent image carrier is set to 0.5.

According to a second aspect of the present invention, the coefficient of static friction (μs) of the surface of the latent image carrier is set to 0.2 to 0.5.

According to a third aspect of the present invention, the charging device is provided with:
It is characterized in that it is arranged close to the surface of the latent image carrier.

The invention according to claim 4 is characterized in that a means for applying a lubricant to the surface of the latent image carrier is provided facing the surface.

The invention according to claim 5 is characterized in that the means for applying the lubricant includes an applying member which comes into contact with the surface of the latent image carrier.

According to a sixth aspect of the present invention, an intermediate transfer member is disposed to face the latent image carrier, and the toner image on the latent image carrier can be superimposedly transferred onto the intermediate transfer member. Is characterized in that the superimposed image can be collectively transferred to recording paper.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating a main configuration of an image forming apparatus that is an example for describing an embodiment of the present invention. In FIG. 1, an image forming apparatus 1 is a full-color copying machine capable of forming an image for each color separated into colors, and includes an endless belt-shaped photoconductor 2.
The photosensitive member 2 is hung on a driving roller 3, a driven roller 4, and a primary transfer opposing roller 5 located between the axes of these rollers, and can move in a direction indicated by an arrow F. The developing device 6 is provided in parallel with the extended portion between the driven roller 4 and the driven roller 4. In this embodiment, the photosensitive member 2
Is set to 178 mm / sec.

In FIG. 1, the developing device 6 includes colors (magenta, cyan, yellow,
(For convenience, the developing device is denoted by reference numeral 6, and the initials of each color (M for magenta, C for cyan, Y for yellow, and B for black) )). The developing device 6 using the one-component toner is provided with a developing sleeve (for convenience, the developing device is indicated by a reference numeral for each color) which is a developing member capable of carrying the one-component toner in a thin layer on the surface. ,
The one-component toner can be electrostatically attracted and adhered to the electrostatic latent image on the photoconductor 2 by making contact with the photoconductor 2.

A charging device 7 is provided in front of the developing device 6 in the moving direction of the photosensitive member 2, and writing light from a writing device (not shown) enters between the charging device 7 and the developing device 6 although not shown. It has become.

An intermediate transfer belt 8 is provided behind the developing device 6 in the moving direction of the photosensitive member 2 so as to face the primary transfer opposing roller 5. The intermediate transfer belt 8 is wound around a plurality of rollers 9 and moves in the same direction as the photosensitive member 2 at a position where the intermediate transfer belt 8 is opposed to and contacts the photosensitive member 2. A primary transfer roller 10 for electrostatically attracting and transferring the toner image on the photoconductor 2 is provided.

One of the rollers around which the intermediate transfer belt 8 is looped (indicated by reference numeral 9 'for convenience) is for transferring the toner image carried on the intermediate transfer belt 8 to the recording paper S. Secondary transfer rollers are arranged to face each other.

A cleaning device 11 is disposed behind the primary transfer position composed of the primary transfer opposing roller 5 and the primary transfer roller 10 in the moving direction of the photoconductor 2, and the cleaning device 11 is disposed on the photoconductor 2 for cleaning. The residual toner collected by the blade 11A is introduced into the waste toner bottle 12.

The charging device 7 used for uniform charging of the photoreceptor 2 employs the proximity charging type shown in FIG. 4, and the current value of the AC component applied so that the charging voltage can be set to -550 V is 1 .55 mA, and the frequency is 1.5 KHz.

In the image forming apparatus 1 having the above configuration, the photosensitive member 2
After being uniformly charged by the charging device 7, an electrostatic latent image is formed by writing light for each color separation color, and a visible image using a one-component toner having a complementary color relationship with the color separation color in the developing device 6. The process is performed, and the visible toner image is temporarily transferred to the intermediate transfer belt 8. This process is repeated for each color, is superimposed and transferred onto the intermediate transfer belt 8, and is then collectively transferred onto the recording paper S. The cleaning device 11 removes the remaining toner from the photoconductor 2 on which the toner image of each color has been transferred to the intermediate transfer belt 8, and the charging device 7 again performs uniform charging.

In the present embodiment, the coefficient of static friction (μs) on the surface of the photosensitive member 2 is set to 0.2 to 0.5, and a configuration for maintaining the coefficient of static friction (μs) is provided. I have. FIG. 2 is a schematic diagram for explaining an arrangement relationship between the photoconductor 2 and the cleaning device 11, and in FIG.
In front of the cleaning device 11 in the moving direction of
A lubricant applying means 13 is provided. In FIG.
The lubricant application unit 13 includes an application brush 13A that is an application member that comes into contact with the surface of the photoconductor 2. The coating brush 13A is planted on a surface of a base cloth wound and fixed on an outer peripheral surface of a central axis having an axial direction in a width direction of the photoconductor 2 which is a direction perpendicular to a moving direction of the photoconductor 2. 2 while contacting the surface of
That is, the photosensitive member 2 can be rotated in a direction opposite to the moving direction.

The application brush 13A is provided with a solid lubricant 13B at a position corresponding to the rotation direction before contacting the photoreceptor 2, so that the lubricant can be scraped little by little at the tip of the brush by contact. It has become.

As the lubricant in this embodiment, for example, a dry fixed hydrophobic lubricant is used. Representative examples are zinc stearate, barium stearate, lead stearate, iron stearate, nickel stearate, and stearic acid. Cobalt, copper stearate, strontium stearate, calcium stearate, cadmium stearate, magnesium stearate, zinc oleate, manganese oleate, iron oleate, cobalt oleate, lead oleate, magnesium oleate, copper oleate, partimine Acid, zinc cobalt palmitate, copper palmitate, magnesium palmitate, aluminum palmitate, calcium palmitate, lead caprylate, lead caproate, zinc linolenate, cobalt linolenate, calcium linolenate , And the like can be given a relatively higher fatty acids such as Rikorinoren cadmium. Natural waxes such as carnauba wax can also be used.

The grounds for setting the coefficient of static friction (μs) on the surface of the photosensitive member 2 in this embodiment to 0.2 to 0.5 are as follows. FIG. 3 shows the results of experiments in which various static friction coefficients (μs) on the surface of the photoconductor 2 were set, and the occurrence of image omission and filming at each coefficient was tested. In FIG. 3, regarding the image omission in the upper part, (○) indicates that there is no image omission, (△) indicates that some image omission has occurred,
(X) indicates that image omission is remarkable.

In FIG. 3, the result regarding the missing image is as follows.
When the coefficient of static friction (μs) was 0.2 or less, image omission occurred in the photoconductor 2. Therefore, as is clear from FIG. 3, the static friction coefficient (μs) is set to the lower limit of 0.2.
And preferably not less than this value.

Next, regarding filming, (（) in FIG. 3 indicates that filming did not occur (、).
Indicates that filming occurred slightly, and (x) indicates that filming was remarkable. In FIG. 3, when the static friction coefficient (μs) exceeds 0.5, filming occurred on the photosensitive member 2. Therefore, the coefficient of static friction (μs) on the surface of the photoreceptor 2 is 0.5 as the upper limit, and preferably less than 0.5.

Here, the reason why filming does not occur when the upper limit value is 0.5 is considered as follows. The adhesion by increasing the force is reduced by setting the coefficient of static friction of the surface.

Since the present embodiment has the above configuration,
In the course of movement of the photoconductor 2, a toner image corresponding to each color separation is formed on the photoconductor 2, and the toner image of that color is transferred to the intermediate transfer belt 8. After the photoreceptor 2 has completed the primary transfer process, the toner remaining on the surface is removed by the cleaning device 11, but the lubricant is applied by the lubricant applying device 13 in the previous stage. As a result, the lubricant applied to the surface of the photoconductor 2 is removed by the cleaning device 11.
Is uniformed. When passing through the cleaning device 11, the lubricant is applied to the surface of the photoreceptor and covers the surface layer.

The surface of the photoreceptor 2 is covered with a lubricant,
Since the static friction coefficient (μs) is maintained in the range of 0.2 to 0.5, filming hardly occurs even when the transfer to the intermediate transfer belt 8 is repeated. For this reason, filming and image omission on the intermediate transfer belt 8 are prevented at the stage before transfer. Therefore, the image which is collectively transferred from the intermediate transfer belt 8 onto which the toner images of each color are transferred to the recording paper does not partly lose.

In the charging device 7 for the photosensitive member 2, the occurrence of filming is suppressed by setting the static friction coefficient of the surface of the photosensitive member 2 to 0.2 to 0.5. Uniform charging can be obtained without charging unevenness over the entire surface of the photosensitive member.

In FIG. 1, reference numeral 14 denotes a neutralization lamp for the photosensitive member 2, reference numeral 15 denotes a cleaning blade for the charging roller of the charging device 7, and reference numeral 16 detects the image density on the photosensitive member 2. 3 shows a density sensor.

[0042]

According to the first and third aspects of the present invention,
Using a power failure device placed close to the latent image carrier, the DC component and the AC component are charged in a superimposed state, and the electrostatic latent image on the latent image carrier can be formed by one-component contact development. When visual image processing is assumed, the upper limit of the static friction coefficient (μs) of the surface of the latent image carrier is set to 0.5, so that the adhesive force on the surface of the latent image carrier is reduced. It is possible to prevent the toner from easily adhering to the surface of the latent image carrier after cleaning. As a result, it is possible to prevent filming from occurring at the time of image formation based on the above premise, and to prevent occurrence of charging failure and occurrence of an abnormal image.

According to the second aspect of the present invention, the static friction coefficient (μs) of the surface of the latent image carrier is set in the range of 0.2 to 0.5 to prevent the occurrence of poor charging and defective images at the upper limit. In addition to the above, the lower limit value can reliably prevent the toner image from being easily scraped off by the developing member. As a result, it is possible to form an image without causing image deletion or the like.

According to the fourth and fifth aspects of the present invention, since the lubricant applying means is in abutting contact with the latent image carrier, a change in the coefficient of static friction (μs) on the surface of the latent image carrier can be reduced. This makes it possible to continuously prevent the occurrence of abnormal images and poor charging while suppressing the occurrence of abnormal images.

According to the sixth aspect of the invention, when the intermediate transfer member is covered with the latent image carrier, the amount of filming increases as the number of transfers increases. Can be prevented by suppressing the occurrence of filming on the latent image carrier side.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining an arrangement relationship between a latent image carrier and a lubricant application device used in the image forming apparatus shown in FIG.

3 is a table showing experimental results regarding the static friction coefficient of the surface of a latent image carrier and the occurrence of image omission and filming using the lubricant applying apparatus shown in FIG. 2;

FIG. 4 is a front view for explaining a configuration of a charging device used in the image forming apparatus shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier as an image forming apparatus 2 Photoconductor as a latent image carrier 6 Developing device 7 Charging device 8 Intermediate transfer belt as an intermediate transfer member 11 Cleaning device 13 Lubricant application device 13A serving as a lubricant application unit 13A Coating brush as coating member 13B Solid lubricant

Claims (6)

[Claims] An image forming apparatus according to claim 1, wherein the surface of the latent image carrier is uniformly charged by a charging device capable of superimposing a DC component and an AC component, and then the electrostatic latent image formed on the latent image carrier is developed by one-component contact development. An image forming apparatus having a process of transferring a toner image subjected to visual image processing to recording paper, wherein an upper limit value of a static friction coefficient (μs) of the surface of the latent image carrier is set to 0.5. Image forming device. 2. The image forming apparatus according to claim 1, wherein the static friction coefficient (μs) of the surface of the latent image carrier is 0.2 to 0.2.
An image forming apparatus, wherein 0.5 is set. 3. An image forming apparatus according to claim 1, wherein said charging device is arranged close to a surface of said latent image carrier. 4. An image forming apparatus according to claim 1, wherein said latent image bearing member is provided with means for applying a lubricant to the surface thereof in opposition. 5. An image forming apparatus according to claim 4, wherein said lubricant applying means includes an applying member which comes into contact with the surface of said latent image carrier. 6. The image forming apparatus according to claim 1, wherein an intermediate transfer member is disposed to face the latent image carrier, and the toner image on the latent image carrier is transferred to the intermediate transfer member. Wherein the superimposed image on the intermediate transfer member can be collectively transferred onto recording paper.