JP3137962B2 - Cleaning equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brush cleaning apparatus in an image forming apparatus of a reversal developing type in an image forming apparatus such as a copying machine, a facsimile, a printer, and the like. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brush cleaning device in an image forming apparatus of a reversal development type which suppresses toner fusion to a body surface and abrasion of a photoreceptor.

[0002]

2. Description of the Related Art Images formed on photoreceptors (electrostatic latent images)
The toner adhered and developed on the photoconductor is electrostatically transferred to a transfer material such as paper by a transfer process, but all of the toner adhered to the photoconductor cannot be transferred. Remains. These toners remaining on the photoreceptor surface are
When the photoreceptor is carried over to the next development step, the photoreceptor is charged by the charging device.The remaining portion of the toner on the photoreceptor is shielded by the toner, so the charging device charges the photoreceptor. Is insufficient, and the image formed next becomes an image defect. In addition, when the process proceeds to the next development step without cleaning the paper dust and the like other than the toner,
In some cases, the toner may enter the developing device in the developing area and cause problems such as defective image formation and failure of the developing device.

Therefore, a conventional image forming apparatus is provided with a cleaning device in order to remove the toner and other deposits remaining on the photosensitive member. Various cleaning methods such as magnetic brush cleaning, electrostatic brush cleaning, brush cleaning, magnetic roller cleaning, and blade cleaning have been proposed so far. A combination of blade cleaning is generally used.

[0004]

However, in the above-mentioned combined use of brush cleaning and blade cleaning, the surface of the photoreceptor is sharply rubbed with the cleaning blade, thereby causing image deterioration. Further, rubbing heat is generated at the contact portion between the cleaning blade and the photoconductor, and the heat causes the residual toner on the photoconductor surface to fuse to the photoconductor, thereby causing a so-called black spot on an image.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a cleaning device which suppresses toner fusion and photoreceptor abrasion on the photoreceptor surface while maintaining good cleaning performance. Aim.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, an electrostatic latent image on the surface of a photoreceptor is developed with a toner by a reversal developing method, and the toner is transferred to a transfer material. after transfer to the toner remaining on the photoreceptor surface, the cleaning device that removes by contacting the brush with the photosensitive member surface, the resistance of the brush 10 ³ to 10 ⁸
Ω · cm range and brush density of 30,000-100,000 brushes /
² and the brush has a polarity opposite to the charging polarity of the toner, and is 100 to 300 V in absolute value.
An AC voltage having a frequency of 100 to 2,000 Hz and a peak-to-peak voltage of 400 to 700 V is superimposed on the DC voltage, and the brush is applied in a direction opposite to the rotation direction of the photoconductor at a contact portion with the photoconductor. The cleaning device is configured to rotate the cleaning device.

According to the above construction, the toner remaining on the photoreceptor surface is removed by rotating the brush.
While maintaining good cleaning performance, it is possible to suppress fusion of the toner to the surface of the photoconductor and scraping of the photoconductor.

Further, since the amount of the brush penetrating into the photosensitive member is in the range of 0.9 to 1.9 mm (claim 2), the cleaning property can be maintained and the durability of the brush is improved. is there.

Furthermore, since the tip of the brush is rounded (claim 3), the scraping of the photoreceptor can be suppressed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies on a cleaning apparatus which suppresses the fusion of toner to the photoreceptor surface and the abrasion of the photoreceptor while maintaining good cleaning performance. In the electrophotographic process employed, it has been found that the cleaning blade, which is a direct cause of toner fusion to the photoreceptor surface and abrasion of the photoreceptor, can be removed. That is, in the reversal developing method, toner is transferred from the developing roller to the electrostatic latent image portion on the photoreceptor surface by a repulsive force generated by a potential difference between a developing bias potential applied to the developing roller and the surface potential of the electrostatic latent image portion on the photoreceptor surface. Since the toner moves and adheres, the electric attraction between the toner and the photoreceptor is weaker than in the regular development method, and even if the cleaning blade is removed, good cleaning performance can be maintained if the brush usage conditions are selected. I found it. Even when the cleaning blade and the brush are used in combination, the pressing force of the cleaning blade against the surface of the photoconductor can be reduced, so that fusion of the toner to the surface of the photoconductor and shaving of the photoconductor can be prevented.

Then, as a result of various examinations on the use conditions of the brush, it was found that the polarity is opposite to the charging polarity of the toner, expressed as an absolute value, a direct bias voltage of 100 to 300 V as a shift bias, and a frequency of 100 to 2,000 Hz. It has been found that good cleaning performance is exhibited by superimposing and applying an AC voltage having a peak-to-peak voltage of 400 to 700 V. In other words, the voltage to be applied to the brush should originally be a DC voltage having the polarity opposite to the charging polarity of the toner, but the toner remaining on the photoreceptor surface contains the toner charging polarity applied in the transfer process. There is also a toner having the same polarity as the transfer voltage due to the transfer voltage having the opposite polarity to the transfer voltage, and the toner having the same polarity as the transfer voltage cannot be collected only by applying the DC voltage. Therefore, although the function of the operation is not yet clear, when a voltage obtained by superimposing the predetermined AC voltage on the DC voltage is applied to the brush, the toner remaining on the surface of the photoreceptor including the toner having the same polarity as the transfer voltage is improved. Was found to be able to be recovered. At this time, the DC voltage applied to the brush has a polarity opposite to the charging polarity of the toner, and needs to be in the range of 100 to 300 V as an absolute value.

Tables 1 to 13 show various settings of the frequency of the AC voltage applied to the brush, the electric resistance of the brush, and the brush density, and variously change the shift bias (DC) and the peak-to-peak voltage (AC) applied to the brush. This is an example. Note that × in the data is × when the toner is placed on a blank portion (non-image portion) and the image becomes black due to image quality or when the image density is low. And If the cleaning is not performed properly, the toner not recovered from the photoreceptor is directly transferred to the transfer material after the next image is formed, and an image such as a black streak appears on a blank portion (non-image portion). Further, when the toner that has not been collected is an image portion, the portion of the photoconductor is not charged due to the presence of the toner at the time of the next image formation, and the necessary toner is not developed. turn into.

As shown in Tables 1 to 7, when the DC voltage applied as the shift bias is lower than 100 V, the residual toner on the surface of the photoreceptor cannot be effectively recovered. The toner charged in the opposite polarity to the DC voltage cannot be effectively collected, resulting in poor cleaning.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

[0018]

[Table 5]

[0019]

[Table 6]

[0020]

[Table 7]

The applied AC voltage has a frequency of 100.
2,000Hz, peak-to-peak voltage 400-700V
Must be in the range

This is because, as shown in Table 8, when the frequency of the AC voltage is lower than 100 Hz, image unevenness corresponding to the frequency occurs, resulting in an image defect.

[0023]

[Table 8]

Further, as shown in Table 9, if the frequency of the AC voltage is higher than 2,000 Hz, the residual toner cannot be effectively collected, resulting in an image defect.

[0025]

[Table 9]

On the other hand, as shown in Tables 1 to 9, when the peak-to-peak voltage of the AC voltage is lower than 400 V, the toner having the opposite polarity to the voltage cannot be effectively collected. Fogging occurs. At this time,
The electric resistance value of the brush is in the range of 10 ³ to 10 ⁸ Ω · cm, and the brush density of the brush is 30,000 to 100,000 /
It must be in the inch range.

The reason is that the brush resistance is 10 ³ Ω · c
If it is lower than m, discharge to the photoconductor is likely to occur as shown in Table 10, and the photosensitive layer is easily broken, resulting in a problem of image failure.

[0028]

[Table 10]

On the other hand, if the resistance of the brush is higher than 10 ⁸ Ω · cm, as shown in Table 11, the applied voltage drops and sufficient cleaning properties cannot be obtained, resulting in an image defect.

[0030]

[Table 11]

By setting the brush density of the brush to a high density such as in the range of 30,000 to 100,000 brushes / inch, the frequency of contact with the residual toner is increased and the cleaning property is improved. Further, hair falling can be prevented by interference between adjacent fibers.

If the brush density is lower than 30,000 / inch ² as shown in Table 12, the number of brushes in contact with the photoreceptor is too small to obtain a cleaning effect, resulting in an image defect.

[0033]

[Table 12]

If the number of brushes exceeds 100,000 / inch ² as shown in Table 13, the number of brushes in contact with the photosensitive member is too large, the frictional force increases, and the brushes do not rotate. On the other hand, if the number of brushes is too large, there is no space for holding the collected toner in the brush, the toner cannot be completely collected from the photoconductor, a cleaning effect cannot be obtained, and an image defect occurs.

[0035]

[Table 13]

Incidentally, it is desirable that the brush penetrates into the photoreceptor in the range of 0.9 to 1.9 mm. If the bite amount is smaller than 0.9 mm, the durability of the brush is improved, but the frequency of contact with the residual toner is reduced, and the cleaning property may be reduced. On the other hand, if the bite amount is larger than 1.9 mm, the frequency of contact with the residual toner increases, but there are problems such as an increase in the rotational torque of the brush, a fall of the brush, and a decrease in durability.

The electric resistance of the brush was measured using a brush electric resistance measuring device shown in FIG. 3 under the conditions of a brush rotation speed of 100 mm / s and a brush biting amount of 1 ± 0.2 mm. This is a value obtained by measuring the electric resistance after seconds. The brush bite amount is a value of the brush bite depth of the photoreceptor, for example, in the case of a combination of a brush having a cylindrical outer periphery and a photoreceptor drum, the radius of the brush and the photoreceptor drum This value is obtained by subtracting the distance from the center of the brush to the center of the photosensitive drum from the sum of the radius and the radius.

In the present invention, it is also important that the brush is rotated in a direction opposite to the rotation direction of the photoconductor at a contact portion with the photoconductor. With this configuration, the brush can be reliably brought into contact with the residual toner on the surface of the photoconductor, and the cleaning performance is improved.

FIG. 1 is a diagram showing an embodiment of an image forming apparatus using the cleaning device of the present invention, which will be described below with reference to FIG.

In the image forming apparatus, a charging device 2 for charging the photosensitive member 1 to a uniform potential is arranged around the photosensitive member 1 in order from the upstream side in the rotation direction of the photosensitive member, and the photosensitive member 1 is exposed to light. An exposure device 3 for forming an electrostatic latent image on the surface, a developing device 4 for forming the latent image into a toner image by a reversal development method,
A transfer device 5 for transferring the toner image onto a transfer material (not shown) and a cleaning device 6 for removing residual toner from the photoreceptor 1 after transfer are arranged.

FIG. 2 is a diagram showing a main part of a cleaning apparatus according to the present invention, which will be described below with reference to FIG.

The cleaning device 6 of the present invention comprises the photosensitive member 1
, A transport spiral 63 for transporting the residual toner removed and recovered from the surface of the photoreceptor 1 by the brush 62, and a direct current to the brush 62 via the drive shaft 61. It has a DC power supply 65 and an AC power supply 64 for superimposing and applying an AC current.

An electric attraction force by applying a voltage obtained by superimposing an alternating current to a direct current to the brush 62 and the brush 6
The toner remaining on the surface of the photoreceptor 1 is removed from the surface of the photoreceptor 1 and collected in the cleaning device 6 by the physical force of the rotation of the photoreceptor 1 against the photoreceptor 1. The collected residual toner is conveyed to a collection box (not shown) by rotation of the conveying spiral 63.

As the brush 62 used in the present invention, a conductive brush can be used. As the conductive brush, fibers of a conductive organic material or inorganic material can be used, the thickness of the fibers is in the range of 3 to 6 denier, and the fiber length is 2
It is preferably in the range of ７7 mm. In addition, it is preferable to round the tip of the brush 62 (the portion that is in sliding contact with the surface of the photoconductor 1) in order to suppress the shaving of the photoconductor 1.

As the conductive fiber of the organic material, synthetic or regenerated fiber in which conductive agent particles are dispersed can be used. For example, polyamide fiber such as nylon 6, nylon 6-6, polyester fiber such as polyethylene terephthalate, acrylic fiber, Examples thereof include polyvinyl alcohol fiber, polyvinyl chloride fiber, rayon, and acetate. In order to impart conductivity to the fiber, a method such as compounding of a conductive agent or metal treatment of the fiber surface can be used.
As the conductive fiber of the inorganic material, carbon fiber can be preferably used, but metal fiber such as stainless steel and brass can also be used.

The peripheral speed of the brush 62 is not particularly limited. For example, by rotating the brush 62 in a direction opposite to the photoconductor 1 at a contact portion with the photoconductor 1, relative speeds 1 to 3 with respect to the peripheral speed of the photoconductor 1
It is rotated at a speed in the range of 1.5 times, preferably 1.5 times to 2.5 times.

The cleaning apparatus of the present invention is applicable to cleaning of a photosensitive member in various electrophotographic methods of an image forming apparatus such as a copying machine, a facsimile, a laser printer, and the like. There is no particular limitation on the photoreceptor to which the cleaning device of the present invention can be used.
Conventionally known photoreceptors such as a silicon photoreceptor, a selenium photoreceptor, and an organic photoreceptor having a single layer or a laminated structure can be used. Further, in the above-described embodiment, an example in which only the brush is used without using the cleaning blade is exemplified. However, it is also possible to use the cleaning blade and the brush together. Can reduce the pressing force on the
It is possible to prevent the toner from being fused to the photoreceptor surface and the shaving of the photoreceptor.

[0048]

EXAMPLE 1 The cleaning device shown in FIG. 2 was mounted on a copying machine (a modified "Creage 7325" manufactured by Mita Kogyo Co., Ltd.) and charged.
When exposure, development and fixing were performed, good cleaning performance was exhibited, and no fusion of the toner to the surface of the photoconductor and scraping of the photoconductor were observed. The members and conditions of the cleaning device are as follows. (Brush) Material: Conductive polyester Resistance: 10 ⁸ Ω · cm Density: 60,000 lines / inch ² (Cleaning conditions) Applied DC voltage: -200 V Applied AC voltage frequency: 1000 Hz Applied AC voltage: 500 V Brush peripheral speed: 100 mm / S Photoreceptor peripheral speed: 127 mm / s

[0049]

As described above, according to the first aspect of the present invention,
According to the method, after developing the electrostatic latent image on the photoreceptor surface with a toner by a reversal developing method, and transferring the toner to a transfer material,
In a cleaning device for removing the toner remaining on the surface of the photoreceptor by bringing a brush into contact with the surface of the photoreceptor, the resistance of the brush is in the range of 10 ³ to 10 ⁸ Ω · cm, and the brush density is in the range of 30,000 to 10 in the range of million units / inch ^2, the brush is expressed in and the absolute value a charging polarity opposite the polarity of the toner to a DC voltage of 100-300 V, frequency in 100～2,000Hz, peak-to-peak voltage 400
An AC voltage of about 700 V is superimposed and applied, and the brush is rotated in a direction opposite to the rotation direction of the photoconductor at a contact portion with the photoconductor.

According to the above configuration, the toner remaining on the photoreceptor surface is removed by rotating the brush.
While maintaining good cleaning performance, it is possible to suppress fusion of the toner to the surface of the photoconductor and abrasion of the photoconductor.

Further, since the amount of penetration of the brush into the photoreceptor is in the range of 0.9 to 1.9 mm (claim 2), the cleaning property can be maintained and the durability of the brush can be improved. It is possible.

Further, since the brush tip is rounded (claim 3), it is possible to prevent the photosensitive member from being scraped.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of an image forming apparatus using a cleaning device of the present invention.

FIG. 2 is a main part configuration diagram of the cleaning device of the present invention.

FIG. 3 is a configuration diagram of a brush electric resistance value measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 4 Developing device 6 Cleaning device 61 Drive shaft 62 Brush 63 Conveying spiral 64 AC power supply 65 DC power supply

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-239183 (JP, A) JP-A-63-27874 (JP, A) JP-A-10-63162 (JP, A) JP-A-9-99 90840 (JP, A) Hikaru 2-138772 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) G03G 21/10-21/12

Claims (3)

(57) [Claims] 1. An electrostatic latent image on a photoreceptor surface is developed with a toner by a reversal development method, and after the toner is transferred to a transfer material, a toner remaining on the photoreceptor surface is brushed on the photoreceptor surface. In the cleaning device, the brush has a resistance in a range of 10 ³ to 10 ⁸ Ω · cm, a brush density in a range of 30,000 to 100,000 brushes / inch ² , and the brush has a toner. The polarity is opposite to the charging polarity of DC and is expressed as an absolute value.
The peak-to-peak voltage is 400 to 700 at 00 to 2,000 Hz.
A cleaning device, wherein a V AC voltage is applied in a superimposed manner, and a brush is rotated in a direction opposite to a rotation direction of the photoconductor at a contact portion with the photoconductor. 2. The cleaning device according to claim 1, wherein an amount of the brush penetrating the photosensitive member is in a range of 0.9 to 1.9 mm. 3. The cleaning device according to claim 1, wherein a tip of the brush is rounded.