JP2001051549A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent image flowing and also to reduce the wear of an image carrier and a cleaning blade by removing NOx. SOLUTION: In this electrophotographic image forming device, the surface of the image carrier is coated with a lubricant consisting of fluorine polytetrafluoroethylene by using a brush roller 23. In such a case, a loop shaped brush (a) and a straight bristle brush (b) are provided coexistent in the periphery direction of the roller 23. It does not matter whether the roller 23 is rotated in the same direction as the image carrier or in a reverse direction to the image carrier at its contact part with the image carrier. The roller 23 is arranged on a more upstream position than the cleaning blade and on a more downstream position than a transfer device, arranged on a more downstream position than the cleaning blade and on a more upstream position than the electrifying device, or arranged on a more downstream position than an electrifying device and on a more upstream position than a developing device in the rotating direction of the image carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transferring an image formed on an image carrier such as a photoreceptor by using an electrophotographic method such as a copying machine, a printer, a facsimile, or a multifunction machine using a laser. The present invention also relates to an image forming apparatus that performs recording on a recording material such as paper. In particular, the present invention relates to an electrophotographic image forming apparatus of a type in which a lubricant is applied to the surface of an image carrier using a brush roller in order to improve cleaning performance.

[0002]

2. Description of the Related Art Conventionally, this type of image forming apparatus includes:
For example, as described in JP-A-6-318018, a brush roller provided with a mixture of a loop-shaped brush and a straight-haired brush in the axial direction is used to abut a separation claw for separating a recording material. Abut a loop-shaped brush on the area,
There is a type in which a toner filming layer formed on an image carrier by pressing a separation claw against the image carrier is effectively removed while minimizing abrasion of the image carrier.

Further, as described in, for example, Japanese Patent Application Laid-Open No. 7-181860, a brush roller provided in a cleaning device is used to prevent toner contamination on a non-image portion on an image bearing member, and stable for a long period of time. There are those that obtain high-quality images.

[0004]

However, in the former case, since the cleaning blade and the loop-shaped brush both come into contact with each other at the portion where the separation claw for separating the recording material comes into contact, the image is polished by both. There was a problem that the life of the carrier was shortened.

In the latter case, when a brush roller having a brush having a straight hair shape is used, the coefficient of friction cannot be controlled, and when the brush roller is used at the lowest position, image flow occurs.
When a brush roller having a loop-shaped brush is used, there is a problem that the friction coefficient does not decrease and the wear of the image carrier increases.

Accordingly, an object of the present invention is to solve such a problem and to prevent NOx forming the toner filming layer to prevent image flow, while reducing wear of the image carrier and the cleaning blade. is there.

[0007]

Accordingly, the present invention provides
In an electrophotographic image forming apparatus in which a lubricant is applied to the surface of an image carrier using a brush roller, a loop-shaped brush and a straight-haired brush are mixedly provided in a circumferential direction of the brush roller. , Characterized in that.

[0008] The brush roller may rotate in the same direction as the image carrier or in the opposite direction at the contact portion with the image carrier.

The brush roller is disposed, for example, at a position upstream of the cleaning blade and downstream of the transfer device, or at a position downstream of the cleaning blade and upstream of the charging device in the rotation direction of the image carrier. Or, it is located downstream of the charging device and upstream of the developing device.

As a lubricant, for example, fluorine polytetrafluoroethylene is used.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a main part of an image forming apparatus according to the present invention.

The image forming apparatus shown in FIG.
This is an image forming apparatus of the type (negative / positive: toner adheres to a place with a low potential). First, a series of processes of image formation will be described by taking this N / P type image forming apparatus as an example.

First, when a print button of an operation unit (not shown) is pressed, a static elimination lamp 11 and a charging device 1 shown in FIG.
Charging roller 13, developing roller 15 of developing device 14,
A predetermined voltage or current is sequentially applied to the transfer roller 17 and the separation electrode 18 of the transfer device 16 at a predetermined timing, and almost simultaneously therewith, the photosensitive drum (image carrier) 1
0, charging roller 13, developing roller 15, transfer roller 1
7. The left screw 19 and the right screw 20 provided in the developing device 14, the toner discharge screw 22 and the brush roller 23 provided in the cleaning device 21 start rotating in a predetermined direction.

As a result, the photosensitive drum 10 is neutralized by the neutralizing lamp 11, and the charging roller 13 rotating in contact therewith.
, The surface is uniformly charged to -950 V, and a latent image is formed with the laser beam L (black solid potential is -150 V). The latent image is developed by a magnetic brush formed by the developing roller 15 to form a toner image. The developing bias at this time is -600V.

The toner image is transferred to the photosensitive drum 1
0 and the transfer roller 17 on a recording material such as a sheet, which is fed from a paper feed mechanism (not shown) and supplied by the upper registration roller 24 and the lower registration roller 25 in synchronization with the leading edge of the image. Transfer (+10 μA applied).

The recording material is separated from the photosensitive drum 1 by the separation electrode 18.
And is discharged outside through a fixing device (not shown).

On the other hand, the toner remaining on the photosensitive drum 10 after the transfer by the transfer roller 17 is transferred to the cleaning device 21 by the rotation of the photosensitive drum 10, and is removed from the photosensitive drum 10 by the cleaning blade 27. .

Here, in the cleaning device 21, the lubricant 30 is also applied onto the photosensitive drum 10. When applying the lubricant 30, the brush roller 23 scrapes the lubricant 30 when the photoconductor drum 10 and the brush roller 23 start to rotate, and applies the lubricant 30 to the photoconductor drum 10 with the brush roller 23.
The lubricating material 30 is fluorine polytetrafluoroethylene (PTFE) whose charging series is higher in the “-charging series”,
When rubbed, it is charged to “−polarity”.

The lubricant 30 transferred onto the photosensitive drum 10
Is hardly scraped off by the cleaning blade 27 and passes through the charging roller 13 which is in pressure contact. At this time, the “−polarity” voltage (−1.
Since 6 kV) is applied, the lubricant 30 on the photosensitive drum 10 is charged to “−polarity” as described above, and therefore passes without adhering to the charging roller 13.

Further, when the photosensitive drum 10 reaches the developing area, the potential on the surface of the photosensitive drum 10 is "-950 V" and the developing bias is "-600 V", so there is a potential difference of "350 V". Is partially collected by the developing device 14. This amount is about 35% of the amount of the lubricant 30 applied on the photosensitive drum 10.

Subsequently, when the toner reaches the transfer device 16, approximately 44% is recovered because a constant current of "+10 μA" is applied to the transfer roller 15. Then, the photosensitive drum 10
Above, about 21% of the lubricant 30 reaches the cleaning device 21 and is applied again by the brush roller 23. By repeating this process, the friction coefficient falls to a friction coefficient suitable for the contact condition of the brush roller 23.

The coefficient of friction of the surface of the photosensitive drum 10 becomes constant when the amount of the lubricant 30 applied and the amount of recovery in the developing device 14 and the transfer device 16 are balanced. In order to obtain a desired coefficient of friction, the recovery amounts of the developing device 14 and the transfer device 16 are the same, so that the contact conditions may be changed.

That is, if the friction coefficient is desired to be increased, the bite amount is reduced, or if the linear speed ratio of the brush roller 23 to the photosensitive drum 10 is reduced and the friction coefficient is reduced, the bite amount is increased. Alternatively, the linear velocity ratio of the brush roller 23 to the photosensitive drum 10 may be increased.

Under a predetermined condition, the friction coefficient of the surface of the photosensitive drum 10 decreases with time, and in order to stabilize at the predetermined friction coefficient, the amount of the lubricant 30 remaining on the photosensitive drum 10 after the transfer is sequentially reduced. When the friction coefficient increases and the friction coefficient becomes stable, the applied amount and the recovered amount must be the same.

The lubricant 30 on the photoreceptor drum 10 is collected at two places, that is, the developing device 14 and the transfer device 16. Of these, the developing device 14 only recovers at the initial stage, and the lubricant 30 is contained in the developer. When mixed, the lubricant 30 mixed in the developer by rubbing with the magnetic brush is applied on the photosensitive drum 10 again.

As time passes, the lubricant 30 in the developer
Gradually increases, and the collected amount and the re-applied amount become the same, so that the developing device 14 does not substantially collect. Therefore, after the friction coefficient is stabilized, the transfer is performed only by the transfer device 16, and the amount of application and the amount recovered by the transfer device 16 become the same.

As described above, in order for the friction coefficient to be in a stable state, the amount of the lubricant 30 remaining on the photosensitive drum 10 after the transfer is sequentially increased, and the amount of the lubricant 30 is kept constant when the friction coefficient is in a stable state. The recovery amount must be the same, "when the application amount is constant and the recovery amount increases", "when the recovery amount is constant and the coating amount decreases", "the coating amount decreases,
When the amount of collection increases ".

As the amount of recovery is reduced with time, the recoating in the developing device 14 is performed, and the amount of recovery increases. "When the amount of application is constant and the amount of recovery increases,""the amount of application decreases and the amount of recovery increases. If not. Therefore, it is "a case where the collection amount is constant and the application amount is small".

The purpose of reducing the coefficient of friction by applying the lubricant 30 to the photosensitive drum 10 is to reduce the relative coefficient of friction between the cleaning blade 27 and the photosensitive drum 10 so that the cleaning blade 27 does not scrape the photosensitive drum 10. In other words, the wear of the cleaning blade 27 and the photosensitive drum 10 is eliminated, and the life of the cleaning blade 27 and the photosensitive drum 10 is extended.

As shown in FIG. 2, the amount of wear of the photosensitive drum 10 decreases as the coefficient of friction decreases. Therefore, in order to extend the life of the photosensitive drum 10,
The lower the coefficient of friction, the better. The solid line in FIG. 2 indicates a linear velocity of “114 mm / se
c ", A4 horizontal feed 1 to 2 (repetition of continuous image formation of two sheets), using a brush having a 15 mm straight hair shape, and when the amount of bite into the photosensitive drum 10 is" 1.5 mm ", 200K sheets after that 4 shows the relationship between the coefficient of friction and the wear amount of the photoconductor.

However, when the coefficient of friction decreases, the surface of the photosensitive drum 10 is not abraded, and in the region of wear (4 μm or less) as indicated by the dashed line in FIG. Due to the accumulation of NOx, NOx on the surface of the photosensitive drum 10 absorbs moisture at high temperature and high humidity to reduce the resistance, so that an original latent image cannot be formed.

FIGS. 3 and 4 use a φ15 mm straight-hair brush, and the amount of bite into the photosensitive drum 10 is “1.5
mm ", when rotated in the opposite direction to the photosensitive drum 10,
And the relationship between the initial number of sheets and the coefficient of friction when rotating in the same direction.

In the case of a brush having a straight hair shape, the friction coefficient changes depending on the number of rotations, but in the long term, the friction coefficient shown in FIG.
m straight hair brush, 400 rpm, rotation in the same direction as the photoreceptor drum 10, biting amount is "1.5 mm"), and the coefficient of friction varies greatly. The variation width of the friction coefficient over time is about “± 0.05”, and even if the friction coefficient is controlled to be equal to or higher than the friction coefficient at which no image flow occurs in the figure, “0.25”
~ 0.35 ". At this time, the maximum friction coefficient “0.3
Assuming that it becomes constant at 5 ”, about 12 μm
The amount of wear.

The amount of wear of the φ30 photosensitive drum 10 in the absence of the lubricating material 30 is about 20 μm / 200K, so that the effect is about 40%, but not sufficient. Of course, if the friction coefficient changes between "0.25 and 0.35" over time, the amount of wear will decrease a little, but if the friction coefficient changes as shown in FIG. The amount of toner attached changes and the image density on the recording material changes.

Therefore, as shown in FIG. 2, it is preferable that the coefficient of friction is reduced to a maximum of "0.15" or less to reduce fluctuations. However, in this region, the photosensitive drum 10 is not polished by the blade 27, so that an image flow occurs as described above.

On the other hand, FIGS. 7 and 8 show a case where a loop-shaped brush having a diameter of 15 mm is used, and when the bite amount into the photosensitive drum 10 is "1.5 mm", the photosensitive drum 10 is rotated in the opposite direction. FIG. 6 shows the relationship between the friction coefficient and the initial number of sheets when rotating in the same direction. As you can see from the figure, when using a loop-shaped brush,
Even if the rotational speed is changed, the friction coefficient hardly changes and does not decrease. This is because the loop-shaped brush is
This is because the lubricant 30 on the zero surface is polished.

When the coefficient of friction is less than "0.15" and the lubricant 30
In order to make the supply of the toner and the polishing of the photosensitive drum 10 compatible, the brush roller 23 may be a mixture of a loop-shaped brush a and a straight-shaped brush b as shown in FIG. That is, the lubricant 30 is supplied by the brush b having a straight hair shape, and a small amount of the photoconductor drum 10 is polished by the brush a having a loop shape.

FIG. 10 uses the brush roller of FIG.
30 photoconductor drum 10 with a linear velocity of “114 mm / sec”, A4 horizontal feed 1 to 2 (repetition of continuous image formation of two sheets), the amount of biting into photoconductor drum 10 is “1.5 mm”, the same as photoconductor drum 10 The figure shows changes in the number of sheets and the coefficient of friction when 200K sheets of image are formed under the condition of rotation speed of 400 rpm in the directional rotation.

In the brush roller 23 in which the loop-shaped brush a and the straight-shaped brush b are mixed, the friction coefficient is "0.1
5 and less long-term fluctuations.
The abrasion amount (5 μm) indicated by the mark was made possible, and the image flow in a high-temperature and high-humidity environment was also eliminated.

The coefficient of friction of the surface of the photosensitive drum 10 is measured by a method generally called an Euler belt method (A3 Mechanics / Mechanical Mechanics P35 (1986), Basic Edition, Mechanical Engineering Handbook of the Japan Society of Mechanical Engineers), and FIG. And a value calculated by μ = ln (F / 100) / (π / 2).

As described above, in the present invention, the lubricant 30 is applied to the surface of the photosensitive drum 10 using the brush roller 23.
In the electrophotographic image forming apparatus for applying the brush, a brush a having a loop shape and a brush b having a straight hair are provided in the circumferential direction of the brush roller 23.

The brush roller 23 may rotate in the same direction as the photosensitive drum 10 or in the opposite direction at the contact portion with the photosensitive drum 10.

In the above-described example, the brush roller 23 is arranged at a position upstream of the cleaning blade 27 and downstream of the transfer device 16 in the rotation direction of the photosensitive drum 10. However, the brush roller 23 may be disposed at a position downstream of the cleaning blade 27 and upstream of the charging device 12 in the rotation direction of the photosensitive drum 10 as shown in FIG. In the rotation direction of the photosensitive drum 10, the charging device 1
2 and may be arranged at a position upstream of the developing device 14. In FIGS. 12 and 13, reference numeral 28 denotes a cleaning brush.

[0044]

As described above, according to the present invention, since the lubricant is applied, the cleaning blade is prevented from being caught or chattered, the transfer efficiency is improved, and the use of a small particle size toner or a spherical toner is possible. It can be.

Further, according to the present invention, a loop-shaped brush and a straight-shaped brush are mixed in the circumferential direction of the brush roller.
By removing x, it is possible to prevent image flow, and it is possible to reduce wear of the image carrier and the cleaning blade as compared with the case of using only a loop-shaped brush.

According to the fourth aspect of the present invention, since the brush roller is disposed at a position upstream of the cleaning blade and downstream of the transfer device in the rotation direction of the image carrier, the space around the image carrier is reduced. Can be smaller.

According to the fifth and sixth aspects of the invention, the brush roller is disposed at a position downstream of the cleaning blade and upstream of the charging device in the rotation direction of the image carrier, or at a position downstream of the charging device. However, since the toner is arranged at a position upstream of the developing device, the toner is not adversely affected by the transfer residual toner, the friction coefficient does not vary, and the friction coefficient can be stabilized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of an image forming apparatus according to the present invention.

FIG. 2 is a graph showing a relationship between a photoconductor surface friction coefficient and a photoconductor wear amount.

FIG. 3 is a graph showing the relationship between the number of copies and the photoreceptor surface friction coefficient when a brush with a straight hair shape is used and the brush roller rotates in the opposite direction to the photoreceptor drum.

FIG. 4 is a graph showing the relationship between the number of copies and the photoconductor surface friction coefficient when a brush having a straight hair shape is used and the brush roller rotates in the same direction as the photoconductor drum.

FIG. 5 is a graph showing the relationship between the number of copies and the photoconductor surface friction coefficient when a straight-hair brush is used.

FIG. 6 is a graph showing a relationship between a coefficient of friction and an image density.

FIG. 7 is a graph showing the relationship between the number of copies and the photoconductor surface friction coefficient when a brush roller is rotated in the opposite direction to the photoconductor drum using a loop-shaped brush.

FIG. 8 is a graph showing the relationship between the number of copies and the photoreceptor surface friction coefficient when the brush roller rotates in the same direction as the photoreceptor drum using a loop-shaped brush.

FIG. 9 is a side view illustrating a configuration of a brush roller.

FIG. 10 is a graph showing the relationship between the number of copies and the photoreceptor surface friction coefficient when using a brush roller in which a straight-shaped brush and a loop-shaped brush are mixed.

FIG. 11 is a front view of a measuring device for measuring a coefficient of friction of a photosensitive drum surface.

FIG. 12 is a schematic configuration diagram of a main part of another image forming apparatus according to the present invention.

FIG. 13 is a schematic diagram illustrating a main part of still another image forming apparatus according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum (image carrier) 12 charging device 14 developing device 16 transfer device 21 cleaning device 23 brush roller 27 cleaning blade 30 lubricant a loop-shaped brush b straight-hair shaped brush

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C10N 40:06 50:08

Claims (7)

[Claims] 1. An electrophotographic image forming apparatus for applying a lubricant to the surface of an image carrier using a brush roller, wherein a loop-shaped brush and a straight-haired brush are mixed in the circumferential direction of the brush roller. An image forming apparatus provided as an image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the brush roller is rotated in the same direction as the image carrier at a contact portion with the image carrier. 3. The image forming apparatus according to claim 1, wherein the brush roller is rotated in a direction opposite to the image carrier at a contact portion with the image carrier. 4. The image according to claim 1, wherein the brush roller is disposed at a position upstream of a cleaning blade and downstream of a transfer device in a rotation direction of the image carrier. Forming equipment. 5. The image according to claim 1, wherein the brush roller is disposed at a position downstream of a cleaning blade and upstream of a charging device in a rotation direction of the image carrier. Forming equipment. 6. The image according to claim 1, wherein the brush roller is arranged at a position downstream of the charging device and upstream of the developing device in the rotation direction of the image carrier. Forming equipment. 7. The method according to claim 1, wherein said lubricant is made of fluorine polytetrafluoroethylene.
7. The image forming apparatus according to 5 or 6.