JPH0333780A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a distinct image without the occurrence of blur on a back side or jitter by using a web member as a means for cleaning an elastic transfer roller. CONSTITUTION:The device is provided with an image carrier, an elastic transfer member for transferring the image formed on the image carrier to a transfer material and the web member 12 for cleaning the elastic transfer member. Namely, the web member 12 keeps contacting with the elastic transfer member, for example, the elastic transfer roller 3 and relatively acts with the elastic transfer roller 3 so as to clean the surface of the elastic transfer roller. In such case, the web member 12 is laid on two or three rollers 13 and made to relatively act with the elastic transfer roller 3 with the rotation of the roller 13. Thus, the cleaning of the transfer member 5 is completely performed and the distinct image is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image forming apparatus, and particularly to an image forming apparatus provided with means for cleaning an elastic transfer member.

(Prior Art) Currently, in image forming apparatuses using electrophotography, corona charge is mainly used as a method for transferring an image formed on an image carrier such as a photoreceptor to a transfer material such as paper. A corona transfer method using However, with this corona transfer method, images may scatter, or transfer defects may occur if the transfer material absorbs moisture in a humid environment.
There were problems such as the need for an expensive power source to generate high voltage.

In order to solve these problems, a method has been proposed in which a transfer roller is pressed against an image carrier, a bias voltage is applied, and an image is transferred by pressure and electrostatic force. According to this method, there is no image scattering, environmental stability is good, and good transfer can be performed without damaging the R carrier.

(Problem to be Solved by the Invention) However, in the method of transferring images using pressure and electrostatic force, floating toner and paper dust adhere to the surface of the transfer roller due to long-time transfer, resulting in insufficient transfer. Another disadvantage is that the surface of the transfer material becomes dirty due to the toner adhering to the surface of the transfer roller.

A method using a cleaning blade has been proposed to remove floating toner and paper dust adhering to the surface of the transfer roller (Japanese Patent Laid-Open No. 48-68239), but this method
The transfer roller cannot be cleaned sufficiently unless the linear pressure of the cleaning blade is increased.
If the linear pressure is increased, the friction coefficient between the cleaning blade and the transfer roller increases, resulting in jitter in the image. Further, when a transfer roller with low hardness is used, sufficient leaning cannot be performed due to the elasticity of the transfer roller. Furthermore, when the particle size of the toner is small, cleaning is difficult.

The present invention has been made under the above circumstances, and an object of the present invention is to provide an image forming apparatus capable of sufficiently cleaning a transfer member.

[Structure of the Invention] (Means for Solving the Problem) According to the present invention, an image carrier, an elastic transfer member for transferring an image formed on the second image carrier to a transfer material, and an elastic An image forming apparatus is provided that includes a web member for cleaning a transfer member.

Further, according to the present invention, an image carrier, an elastic transfer member for transferring an image formed on the image carrier to a transfer material under non-heating conditions, and a member that is in sliding contact with the elastic transfer member. An imaging device is provided which includes a flexible fibrous web member for removing powder remaining on the surface thereof.

The web member used in the image forming apparatus of the present invention moves relative to the elastic transfer roller while maintaining contact with the elastic transfer member, such as the elastic transfer roller.
The surface of the elastic transfer roller can be cleaned. In this case, the web member can be applied to two or three rollers and caused to move relative to the elastic transfer roller by rotation of the rollers or by winding from one roller to another.

Further, in the present invention, it is also possible to use both cleaning using a web material and cleaning using a conventional cleaning blade.

(Function) Due to long-term transfer, floating toner and paper powder adhere to the surface of the transfer roller due to physical adhesion force, resulting in insufficient transfer, and the toner adhering to the surface of the transfer roller may damage the surface of the transfer material. There is a phenomenon where the surface becomes dirty. Further, when the width of the transfer material is narrower than the width of the transfer roller, toner adheres to the transfer roller in a portion wider than the width of the transfer material, and a similar phenomenon occurs.

In the image forming apparatus of the present invention, a web member is provided in contact with the elastic transfer member, and the relative movement between the two cleans the adhesive adhered to the surface of the elastic transfer member. At this time, Coulomb force due to friction, magnetic force, physical adhesion force, mechanical impact force, etc. act between the toner adhering to the surface of the elastic transfer member and the web member, and the toner is transferred from the surface of the elastic transfer member to the web member. It can be collected in

(Example) Hereinafter, specific examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an image forming apparatus using an electrophotographic method according to an embodiment of the present invention.

In FIG. 1, a photoreceptor drum 1 is an OPC drum formed by coating an organic photoreceptor on the surface of an aluminum tube. The surface potential of the photosensitive drum 1 is charged to about 600 V by a scorotron charger (not shown). Image exposure is performed on the charged surface of the photoreceptor drum 1 by an LED array (not shown), thereby forming an electrostatic latent image on the surface of the photoreceptor drum 1. This electrostatic latent image is developed by a two-component developer 2, and a toner image 4 is formed on the surface of the photoreceptor drum 1. In this case, the polarity of the toner is negative, so reversal development is performed.

A transfer material 5 is supplied and conveyed from a cassette (not shown) and inserted between the photosensitive drum 1 and the transfer roller 3.

No bias is applied to the transfer roller 3 until the transfer material enters between the photosensitive drum 1 and the transfer roller 3. This is because if a transfer bias is applied from the leading edge of the transfer material 5, the transfer material will wrap around the photoreceptor drum after transfer, and it will be necessary to take a peeling means to peel off the transfer material 5. The equipment becomes complicated and expensive. Therefore, in this embodiment, when the leading edge of the transfer material 5 enters between the photosensitive drum 1 and the transfer roller 3 by 3 mm, the bias is turned on. However, in this method, a tip peeling margin is formed at the tip of the transfer material 5, where an image cannot be formed. Therefore, methods such as applying a transfer bias from the tip of the transfer material 5 and peeling off the transfer material using an AC corona charger, or gradually increasing the transfer bias voltage may be used.

The polarity of the bias applied to the transfer roller 3 is opposite to the polarity of the toner, and in this embodiment, the polarity is +700 to 2.
000V is applied. Further, the transfer roller 3 is pressed against the photosensitive drum 1 with a predetermined pressure.

The transfer roller 3 has a structure as shown in FIG. In FIG. 2, 7 is a resistive layer, 8 is a conductive layer, 9 is an elastic layer, and 10 is a metal shaft.

The resistive layer 7 may be made of a flexible material such as a resin such as polyester, polyethylene, or vinyl chloride, or rubber in which conductive fine metal particles such as conductive carbon, copper, or nickel are dispersed, or a conductive polymer resin. A resistive sheet with excellent properties can be used. The volume resistance value of the resistive layer 7 is '10
8~10I6Ω・mark is preferable, 109~10I2Ω・
Preparation is particularly preferred.

The volume resistivity value can be easily controlled by changing the mixing ratio of the conductive fine particles to the resin or rubber. The volume resistance value of the resistive layer 7 is determined by external pressure and/or
Alternatively, it is desirable that the temperature and humidity do not change or the changes are small in response to changes in environmental conditions such as temperature and humidity.

Since the resin sheet structure shown in FIG. 2 does not have an air chamber inside, the resistance value is more stable against humidity than the foam structure. Because the transfer roller has such characteristics, even if transfer materials 5 of different thicknesses, such as paper, envelopes, and postcards, come between the photoreceptor drum 1 and the transfer roller 3 that are in pressure contact, various Electrical toner transfer conditions can be maintained constant regardless of temperature and humidity conditions.

Preferably, the surface of the resistive layer 7 is smooth.

When unnecessary toner accumulates on the surface of the resistive layer 7, the transfer material 5
However, the smoother the surface of the resistive layer 7, the easier it is to remove this toner. Further, the thickness of the resistive layer 7 is preferably as thin as possible in order not to impair the flexibility of the elastic layer 9, and is preferably in the range of 0.02 to 2 mm.

As the conductive layer 8, a conductive resin such as a resin such as polyester in which conductive fine particles such as conductive carbon are dispersed, a thin metal sheet, or a conductive adhesive can be used. is necessary. The volume resistivity of the conductive layer 8 must be lower than that of the resistive layer 7, 10'Ω
・A value below the mark is preferable. The thickness of the conductive layer 8 is preferably as thin as possible so as not to impair its flexibility. The transfer roller 3 is used in pressure contact with the photoreceptor drum. During the pressure contact, the elastic layer 9 deforms flexibly, and when the pressure-contact carp is released, it needs to quickly return to its original shape, and is stable against repetition. be operational and necessary. That is, the material of the elastic layer 9 is preferably one that has excellent creep resistance and plastic deformation resistance.

As such a material, an elastic body that can be compressed and deformed, such as a foamed rubber sponge, foamed polyethylene, or foamed urethane, can be used. The foam structure is continuous foam (open cells).
Although any structure such as a closed-cell structure or a closed-cell structure can be used, an open-cell structure is preferably used because its shape is stable regardless of the ambient temperature. Any flexibility can be obtained for the elastic layer 9 by changing the constituent materials, foamed structure, degree of foaming, etc. Note that the function of the elastic layer 9 is maintained by making the sum of the thicknesses of the resistive layer 7 and the conductive layer 8 1/10 or less of the thickness of the elastic layer 9.

In the transfer nip formed by the photoreceptor drum 1 and the transfer roller 3 described above, the toner image 4 on the photoreceptor drum 1 is transferred to the transfer material 5 by electrostatic force or mechanical force. Thereafter, the toner remaining on the surface of the photosensitive drum 1 is removed by a cleaner (not shown), and then the static electricity is removed by a static elimination lamp, thus completing one cycle of the process.

The shaft 10 and the conductive layer 7 are electrically connected by applying a conductive substance 11 to both ends of the roller.

In the image forming apparatus shown in FIG. 2, the transfer roller 3 does not have a drive system and rotates as the photosensitive drum 1 rotates. After passing through the transfer nip, the transfer material 5 is naturally peeled off due to its own weight, and is led to a fixing device (not shown) by a conveyance bell 6, where the toner image is fixed.

When the transfer material 5 is not present in the transfer nip, no transfer bias is applied, but when toner adheres to the transfer roller 3 due to physical adhesion force, or when the width of the transfer material 5 is narrower than the width of the transfer roller 3, Toner adheres to a portion of the transfer roller 3 that is wider than the width of the transfer material 5.

In order to prevent such adhesion of toner to the transfer roller 3, a web type cleaning unit 14 is provided. The web-type cleaning unit 14 includes three rollers 13 and a web member 12 wound around them. As the transfer roller 3 rotates, the roller 13 rotates in a direction opposite to the rotation direction of the transfer roller 3,
Thereby, the web member 12 moves in a direction opposite to the rotational direction of the transfer roller 3 and cleans the surface of the transfer roller 3. Note that the web member 12 may be moved in the same direction as the rotational direction of the transfer roller 3, but in that case, the moving speed of the web member 12 is set to 1.5 of the circumferential speed of the transfer roller 3.
If it is not doubled, it will be difficult to lean effectively.

The web member that can be used in the present invention may be made of any material as long as it can slide into contact with the elastic transfer roller and remove toner from the surface of the elastic transfer roller.
Felt-like nonwoven fabric (manufactured by Nippon Balleen Co., Ltd.), press felt, needle felt, nonwoven paper felt, porous felt, etc. can be preferably used. Particularly, in order to remove small particle diameter toner having an average particle diameter of 8 μm or less, it is preferable to use a fiber made of ultrafine fibers of ld (denier) or less, such as (manufactured by Toshisha Co., Ltd.). In this example, a felt-like nonwoven fabric (manufactured by Nihon Balleen Co., Ltd.) was used.

Examples and comparative examples in which the cleaning unit, which is a feature of the present invention, was variously modified in the image forming apparatus described above and a continuous copying test were conducted will be described below.

Example 1 Using the image forming apparatus shown in FIG. 1, the roller 13 of the cleaning unit 14 is rotated in the opposite direction to the rotation direction of the transfer roller 3, thereby cleaning the surface of the transfer roller 3 with the web member 12. When an image was formed, a very clear image with high density, little fog, and no jitter was obtained.

Further, when images having a width (A4) shorter than the transfer roller width (A3) were continuously copied, back staining did not occur until 10,000 copies were made.

Embodiment 2 The image forming apparatus used in this embodiment is equipped with a winding type cleaning unit 17 as shown in FIG. This winding type cleaning unit 17 has two rollers 1
6a, 16b and the web member 15 wound around them
It consists of

As the transfer roller 3 rotates, the web member 15
It is wound up from the roller 16a to the roller 16b, moves in the opposite direction to the rotational direction of the transfer roller 3, and cleans the surface of the transfer roller 3.

Images obtained using this image forming apparatus also have the same characteristics as in the examples.
High density, low fog, no jitter,
It was a very clear image.

In addition, when the back stain was examined in the same manner as in Example 1, 2
Back staining did not occur until 0,000 copies were made.

Example 3 As shown in FIG. 4, the image forming apparatus used in this example has the retractable cleaning unit 17 used in Example 2.
and a cleaning blade 18.

Similar to Example 1, the images obtained using this image forming apparatus were very clear images with high density, little fog, and no jitter.

Note that the blade linear pressure of the cleaning blade 18 is 8g.
Since /cI11 is quite small, the coefficient of friction between the transfer roller 3 and the cleaning blade 18 is small, so the cleaning blade 18 smoothly cleans the surface of the transfer roller, but some cleaning residue remains. However, this cleaning residue was completely cleaned by the web member of the take-up cleaning unit 19, and the final image did not have back stains even after 4,000 copies were made. Further, no jitter caused by the cleaning blade 18 occurred, and the image was extremely good.

Example 4 As shown in FIG. 5, the image forming apparatus used in this example includes a cleaning unit 20 that is a combination of the cleaning unit 14 used in Example 1 and a cleaning blade 18.

Similar to Example 1, the images obtained using this image forming apparatus were very clear images with high density, little fog, and no jitter.

Comparative Example 1 The image forming apparatus used in this example is the same as the image forming apparatus shown in FIG. 4, except that the take-up cleaning unit 17 is removed, and is equipped with a cleaning unit consisting only of a cleaning blade 18. Using this image forming apparatus, images were formed in the same manner as in Example 1 while cleaning the transfer roller only with the cleaning blade 18. In the area where the linear pressure of the blade was less than 10 g/am, 100 sheets were printed continuously. After copying, back staining occurred due to poor cleaning of the transfer roll 3.

Further, in a region where the blade linear pressure was 10 g/am or more, the cleaning blade 18 slightly vibrated with the surface of the transfer roller 3, causing jitter on the image. The degree of this jitter became worse as the blade line pressure increased.

Comparative Example 2 The image forming apparatus used in this example is the same as the image forming apparatus shown in FIG. 4, except that the winding type cleaning unit 17 and cleaning blade 18 are removed, and the image forming apparatus is not equipped with a cleaning unit.

When an image was formed using this image forming apparatus in the same manner as in Example 1 without cleaning the transfer roller, staining occurred on the back side after copying 10 sheets.

The results of the above examples and comparative examples are shown in Clothing 1 below.

Although various examples of the present invention are shown in the table above, the present invention is not limited to these examples in any way. The image forming apparatus of the present invention includes a web member for cleaning the elastic transfer roller, but the web member is not limited to those shown in the embodiments and can be modified in various ways. Furthermore, various known means and methods can be employed as the developing means, developing method, fixing/fixing means, and fixing/fixing method.

[Effects of the Invention] As described above, according to the present invention, in an image forming apparatus equipped with an elastic transfer roller for transferring an image formed on an image carrier to a transfer material, the elastic transfer roller is cleaned. By using a web member as a means for this purpose, it is possible to obtain clear images without back stains or jitter.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view showing a transfer roller used in the image forming apparatus of the present invention, and FIGS. FIG. 3 is a schematic diagram showing an image forming apparatus according to another embodiment. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 3... Transfer roller, 5... Transfer material, 12°15°... Web member, 14°17°0... Cleaning unit, 8... Cleaning blade.

Claims (2)

[Claims] (1) An image forming apparatus including an image carrier, an elastic transfer member for transferring an image formed on the image carrier to a transfer material, and a web member for cleaning the elastic transfer member. (2) An image carrier, an elastic transfer member for transferring the image formed on the image carrier to a transfer material under non-heating conditions, and relative movement while being brought into elastic contact with the elastic transfer member. An image forming apparatus comprising: a flexible fibrous web member for removing powder remaining on the surface thereof.