JPH10254295A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing an image omission on an image carrier, a void on an intermediate transfer body or transfer paper, and an abnormal image like dust, by controlling the statical friction coefficient of the surface of the image carrier. SOLUTION: In this image forming device of a system, where a toner image is formed on the surface of a photoreceptor 1 by one-component contact development, transferred to the surface of an intermediate transfer belt 15, and further transferred to transfer paper, the statical friction coefficient μs of the surface of the photoreceptor 1 is set to 0.2 to 0.4. The contact pressure of the developing rollers of respective yellow, magenta and cyan developing units Y, M and C of a multicolor developing device 8 to the photoreceptor 1 is set to <=300kPa. Furthermore, the surface of the photoreceptor 1 is coated with lubricant so as to control and maintain the statical friction coefficient μs at a target value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate transfer type image forming apparatus using a one-component contact developing system, and more particularly to an improved image carrier.

[0002]

2. Description of the Related Art In the case of an intermediate transfer type image forming apparatus using a one-component contact developing system, for example, a color image forming apparatus,
Toner images of different colors are respectively formed on the surface of the image carrier, the toner images are superimposed and transferred at the same position on the intermediate transfer body, and the toner image on the intermediate transfer body is further transferred to transfer paper. .

In an image forming apparatus using such an intermediate transfer member, transfer defects such as a blank portion of a character portion (eating of insects) and toner dust easily occur, and an abnormal image tends to occur. This is because the toner image is transferred twice from the image carrier to the intermediate transfer member and from the intermediate transfer member to the transfer paper.

As a means for preventing such an abnormal image, a method for managing the static friction coefficient μs of the image carrier has been proposed in Japanese Patent Laid-Open No. Hei 6-332324. This technology manages the static friction coefficient μs such that image carrier <intermediate transfer member <transfer paper. Also, Japanese Patent Application Laid-Open
Japanese Patent Application Publication No. 154778 proposes a technique for applying a low coefficient of friction substance to the surface of a photoreceptor.

[0005]

However, in the case of one-component contact development, if the static friction coefficient μs of the image carrier becomes too low, the image formed on the image carrier has missing images (dots, characters, lines, etc.). Is partially removed). In the one-component contact development, a thin toner layer is formed on a developing roller, brought into contact with an image carrier, and the toner on the developing roller is moved to the surface of the image carrier by an electric field or an adhesive force to the surface of the image carrier. In the case of contact development, since the developing roller is brought into direct contact with the image carrier, if the static friction coefficient μs on the surface of the image carrier is too small, the toner image formed on the image carrier is scraped off by the developing roller. It will be easier. This is because the higher the contact pressure of the developing roller in contact with the image carrier (the larger the amount of the developing roller biting into the image carrier), the more remarkable.

Therefore, the present invention manages the coefficient of static friction μs of the surface of an image carrier to eliminate an image on the image carrier, a void on an intermediate transfer member or transfer paper, and an abnormal image such as dust. It is an object of the present invention to provide an image forming apparatus.

[0007]

According to a first aspect of the present invention, there is provided an image forming apparatus which forms a toner image on the surface of an image carrier by one-component contact development, and forms the toner image on the image carrier. An image forming apparatus having an intermediate transfer body transferred to the surface and transferring a toner image on the intermediate transfer body to transfer paper,
The static friction coefficient of the surface of the image carrier is set to 0.2 to 0.4.

According to a second aspect of the present invention, the contact pressure of the developing roller to the image carrier is set to 300 KPa or less.

According to a third aspect of the present invention, a lubricant is applied to the surface of the image carrier.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments and examples of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic center sectional view of a multicolor image forming apparatus according to an embodiment of the present invention. In this apparatus, the belt-shaped photosensitive member 1 is supported by rotating rollers 2 and 3 and rotated in the direction of arrow A. On the outer periphery of the photoreceptor 1, a charging device 4, a static elimination lamp 5, and a cleaning blade 6 for the photoreceptor are provided. At the downstream position of the charging device 4, there is an optical writing unit that irradiates the laser light L emitted from the laser writing unit 7.

A multicolor developing device 8 provided with a plurality of developing units so as to be switchable is disposed at a position downstream of the optical writing unit. The multicolor developing device 8 includes a yellow developing unit Y, a magenta developing unit M, and a cyan developing unit C for each color of toner to be stored. A black developing unit 9 containing a black toner is provided above the multicolor developing device 8. One of these developing units is
It moves to a developable position in synchronization with the development timing of the corresponding color. The multicolor developing device 8 has a mechanism for selecting a developing unit by a rotation of 120 degrees on the circumference, and when the developing unit operates, the black developing unit 9 moves to a position away from the photoconductor 1. . The movement is controlled by the rotation of the cam 10.

In the laser writing unit 7, light from a laser light source (not shown) is scanned by a polygon mirror 12 that is driven to rotate by a motor 11,
The latent image corresponding to the written information is formed on the charged photoconductor 1 via the photoconductor 3 via the mirror 3 and the like. The latent image on the photoconductor 1 is developed by the developing device 7, and a visible image by toner is formed and held on the surface of the photoconductor 1.

The upper portion of the photoconductor 1 is in contact with the intermediate transfer belt 15. The intermediate transfer belt 15 includes a rotating roller 16,
17 is supported rotatably in the direction of arrow B. Photoconductor 1
The upper toner image is transferred onto the surface of the intermediate transfer belt 15 by the bias unit 18 on the back side of the intermediate transfer belt 15.

The photoreceptor 1 is cleaned for each color, and a toner image of a predetermined color is sequentially formed on the photoreceptor 1. Each time the intermediate transfer belt 15 rotates, the intermediate transfer belt 15 is rotated.
The image is transferred to the same position on the upper side to form a color toner image in which several colors are overlapped on the intermediate transfer belt 15. The color toner image obtained by overlapping several colors on the intermediate transfer belt is transferred to a recording medium such as paper or plastic.

At the time of transfer to paper, the paper cassette 19
The paper stored in the paper feed roller 20 and the transport roller pair 2
1. The paper and the image are conveyed to the nip between the intermediate transfer belt 15 and the transfer roller 23 via the registration roller pair 22 at a timing such that the positions of the paper and the image become normal. The paper, on which the toner images of several colors on the intermediate transfer belt 15 are collectively transferred, is sent to a fixing device 24 by a transfer roller 23, and the toner image on the paper is fixed. The sheet is discharged to the upper sheet discharge stack 27.

An intermediate transfer belt cleaning device 28 is provided at the position of the roller 16, and a cleaning blade 29 thereof can be freely moved toward and away from the intermediate transfer belt 15. In the step of receiving the toner image from the photoreceptor 1, the cleaning blade 29 separates from the intermediate transfer belt 15, contacts the image after transferring the image from the intermediate transfer belt 15 to the sheet, and scrapes the residual toner after the image is transferred to the sheet. Take. As described above, there are cleaning blades for the photoconductor 1 and for the intermediate transfer belt 15. The waste toner scraped by these cleaning blades is collected in a collection container 30.
And the collection container 30 is appropriately replaced.

Photoconductor 1, charging device 4, intermediate transfer belt 1
5. The cleaning device 28, the conveyance guide 31 forming the paper conveyance path, and the like are integrally incorporated as shown by the reference numeral 32 in the drawing to form a unit as a process cartridge so that they can be replaced when the service life expires. In addition to replacing the process cartridge 32, the multi-color developing device 8, the black developing device 9, and the like are also replaced at the end of their service life. However, in order to facilitate the replacement and the handling of jammed paper, the front frame of the image forming apparatus main body is used. Reference numeral 33 is rotatable and openable with the support shaft 34 as a center of rotation, as shown in FIG.

In the drawing, reference numeral 35 denotes an electric device / control device, and reference numeral 36 denotes a fan. The fan 36 exhausts air to prevent the internal temperature from rising excessively. In the figure, reference numeral 37 denotes another relatively small-sized paper feeder.

FIG. 3 is a sectional view showing the structure of a yellow developing unit Y, a magenta developing unit M, and a cyan developing unit C which constitute the multicolor developing device 8. Each of these units is a one-component contact developing device, and includes a developing roller 40, a toner replenishing roller 41, a blade 4
2, first and second transport screws 43 and 44.

FIG. 4 shows a state in which an image is missing on the photosensitive member 1 when the contact pressure between the photosensitive member 1 and the developing roller 40 of each of the above-mentioned units constituting the multicolor developing device 8 is changed. I have. ○ indicates no image omission, and × indicates image omission. When the coefficient of static friction μs on the surface of the photoconductor 1 was 0.18, image slippage occurred on the photoconductor 1 regardless of the contact pressure of the developing roller 40. The amount of biting of the developing roller 40 into the photoreceptor 1 at a contact pressure of 200 kPa is 0.18 mm, and if it is further reduced, development failure may occur. Therefore,
It is understood that the coefficient of static friction μs on the surface of the photoconductor 1 needs to be at least 0.2 or more. Further, the abnormal image area is enlarged as the contact pressure is increased. As will be described later, it can be said that when the static friction coefficient μs on the surface of the photoreceptor 1 is 0.4 or more, hollowing out on the intermediate transfer belt 15 is very likely to occur. 2 to 0.4 is preferred. Also, in this case, if the contact pressure is set to 300 kPa or less, the image omission on the photoreceptor 1 and the area on the intermediate transfer belt 15 where there is no omission are always satisfied.

The contact pressure varies depending on the amount of bite as shown in FIG. The hardness of the developing roller 40 used is JISA
Is 53 °. When the hardness is softened to 17 °, the contact pressure becomes about half and the nip width becomes about twice. Image omission is largely affected by contact pressure, but hardly affected by nip width.

FIG. 6 shows the static friction coefficient μs of the surface of the photosensitive member 1.
FIG. 6 shows a state in which a hollow image is generated on the intermediate transfer belt 15 by a combination of the static friction coefficient μs of the surface of the intermediate transfer belt 15.は indicates no voids, △ indicates slight occurrences, and × indicates many occurrences. Static friction coefficient μs of the surface of the intermediate transfer belt 15
Is about 0.3 when the lubricant is sufficiently applied. From this, the coefficient of static friction μs of the surface of the photoreceptor 1 is set to 0.
When the number is 4 or more, it can be seen that a hollow image is very easily generated on the intermediate transfer belt 15. Further, the static friction coefficient μs of the transfer paper was 0.5 to 0.6 in the present measurement method, so that the static friction coefficient μs of the intermediate transfer belt 15 was 0.5
Otherwise, transfer failure is likely to occur during secondary transfer. The static friction coefficient μs was measured using HEIDON Tribogear Muse T, manufactured by Shinto Kagaku Co., Ltd.
YPE: 94I was used. A resin fiber is stuck on the probe measurement surface to increase the coefficient of friction and not to damage the measurement object.

The coefficient of static friction μs of the photosensitive member 1 and the intermediate transfer belt 15 may be controlled by using a lubricant. FIG.
FIG. 3 is a cross-sectional view illustrating a configuration example of an apparatus that applies a lubricant 51 to the photoreceptor 1 using a brush 50 as a mediation applying member.
The lubricant 51 is held by a lubricant holding member 52 and pressed against the brush 50 by a pressure spring (not shown). The application of a lubricant to the intermediate transfer belt 15 is also possible.

By using a lubricant, the coefficient of static friction μs
Can be easily set in the relationship of photoconductor <intermediate transfer belt <transfer paper. Examples of solid lubricants (dry solid hydrophobic lubricants) include, for example, zinc stearate, barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, Calcium stearate, cadmium stearate, magnesium stearate, zinc oleate, manganese oleate, iron oleate, cobalt oleate, lead oleate, magnesium oleate, copper oleate, palmitic acid, zinc zinc palmitate, copper palmitate , Magnesium palmitate, aluminum palmitate,
Fatty acids such as calcium palmitate, lead caprylate, lead caproate, zinc linolenate, cobalt linolenate, calcium linolenate, and cadmium licolinolenate, metal salts of these fatty acids, candelilla wax,
And waxes such as carnauba wax, rice wax, wood wax, oba oil, beeswax, and lanolin.

[0025]

According to the first aspect of the present invention, as described above, the static friction coefficient μs of the surface of the image bearing member is set to 0.2 to 0.4, so that the image on the image bearing member is controlled. Missing,
There is an effect that abnormal images such as missing characters on the intermediate transfer member are eliminated and a stable image can be maintained for a long time.

According to the second aspect of the present invention, as described above, the contact pressure between the image bearing member and the developing roller is reduced by 30%.
By setting the pressure to 0 kPa or less, as in the first aspect, there is an effect that abnormal images such as missing characters on the intermediate transfer member are eliminated and a stable image can be maintained for a long period of time.

As described above, the image forming apparatus according to the third aspect of the present invention uses a lubricant to provide a static friction coefficient μ with a low cost and a simple configuration in addition to the above-mentioned common effects.
There is an effect that s can be easily maintained at the target value.

[Brief description of the drawings]

FIG. 1 is a schematic center sectional view of a multicolor image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a state where the process cartridge of FIG. 1 is rotated and opened.

FIG. 3 is a cross-sectional view illustrating a structure of each color developing unit included in the multicolor developing device 8;

FIG. 4 is a diagram illustrating a state in which an image is missing on the photoconductor when a contact pressure between the photoconductor and a developing roller of each of the above-described units constituting the multicolor developing device is changed.

FIG. 5 is a diagram showing a state in which a contact pressure changes according to a bite amount.

FIG. 6 is a view showing a state in which a hollow image occurs on the intermediate transfer belt due to a combination of respective static friction coefficients of the surface of the photoconductor and the surface of the intermediate transfer belt.

FIG. 7 is a cross-sectional view illustrating a configuration example of an apparatus that applies a lubricant to a photoconductor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 4 charging device 7 laser writing unit 8 multicolor developing device 9 black developing unit 15 intermediate transfer belt 19 paper feed cassette 20 paper feed roller 22 registration roller pair 24 fixing device 27 paper discharge stack unit 28 cleaning device for intermediate transfer belt REFERENCE SIGNS LIST 30 Collection container 32 Process cartridge 40 Developing roller 41 Toner replenishing roller 42 Blade 43, 44 Conveying screw 50 Brush 51 Lubricant 52 Lubricant holding member Y Yellow developing unit M Magenta developing unit C Cyan developing unit

Claims (3)

[Claims] An intermediate transfer member for forming a toner image on the surface of the image carrier by one-component contact development and transferring the toner image on the image carrier to the surface; and a toner image on the intermediate transfer member. Wherein the static friction coefficient of the surface of the image carrier is 0.2 to 0.4. 2. The image forming apparatus according to claim 1, wherein a contact pressure of the developing roller with the image carrier is set to 300 KPa or less. 3. The image forming apparatus according to claim 1, wherein a lubricant is applied to the surface of the image carrier.