JP2011180245A - Charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charger that can move a charging brush following a photoreceptor and can suppress the generation of a brush line and a wound line on an image. <P>SOLUTION: The charger 30 includes a charging brush 31 for charging the photoreceptor drum 1 of an electrophotographic apparatus. The charging brush 31 is formed of an electrostatic-bristle attached brush in a form of a roll which is moved following the photoreceptor drum 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a charging device including a charging brush for charging a photosensitive member of an electrophotographic apparatus.

  2. Description of the Related Art Conventionally, a contact charging device in an electrophotographic apparatus using a roll brush is known.

  For example, as shown in FIG. 6, the contact charging device 100 disclosed in Patent Document 1 has a charging brush 102 formed of a roll-shaped brush that charges the photoreceptor 101.

  Here, in the charging brush 102 made of the above-mentioned roll-shaped brush, depending on the length and hardness of the bristle, the bristle jumps when it leaves the photosensitive member 101. Therefore, as shown in FIG. In some cases, short white marbling-like vertical streaks, called so-called brush streaks, are generated that are dispersed over the entire image obtained by transfer by the photoconductor 101.

  Therefore, in the contact charging device 100 disclosed in Patent Document 1, a drive mechanism 104 is provided on the shaft 103 of the charging brush 102, as shown in FIG. The peripheral speed ratio between the charging brush 102 and the drum-shaped photoconductor 101 is set to 1 or less. Specifically, when the peripheral speed of the photoconductor 101 is 25 mm / sec, the charging brush 102 is driven by the drive mechanism 104 so that the peripheral speed is 25 mm / sec or less.

  As a result, the momentum of the charging brush 102 when the brush bristles move away from the photoconductor 101 is reduced, so that the generation of brush stripes is reduced.

JP-A-8-101559 (released on April 16, 1996) JP-A-6-130732 (published on May 13, 1994)

  By the way, in the above-described conventional charging device, the driving mechanism 104 is provided and the charging brush 102 is rotationally driven. However, since the driving mechanism 104 inherently increases the number of parts, it is preferable that it does not exist. Therefore, it is preferable that the charging brush 102 is driven, that is, rotated with respect to the photosensitive member 101.

  However, in the contact charging device 100 of Patent Document 1, when the peripheral speed ratio between the roll-shaped charging brush 102 and the drum-shaped photoconductor 101 that is equivalent to the case where the drive mechanism 104 does not exist is 1, It is said that the brushed stripes are slightly charged and not enough.

  For example, Patent Document 2 discloses a technique for driving the charging brush with respect to the photosensitive member. However, in Patent Document 2, the technique for moving the charging brush with respect to the photosensitive member generates a brushed line. Not good.

  Here, in the prior art, the brushed streaks occur because the conventional charging brush is made of a fabric brush such as a pile weave brush. If the pile length of the fabric brush is increased, the frictional force cannot be obtained and the follower is not driven. On the other hand, if the pile length of the dough brush is shortened in order to facilitate the follow-up, it becomes easy to generate the brush streak.

  In addition, the conventional charging brush has another problem that charging spots on the winding lines are generated due to the cloth brush such as a pile weave brush.

  That is, in the fabric brush, since the ribbon-shaped fabric is wound into a spiral shape to form a brush, as shown in FIG. 8, there is a problem that streaky charged spots are generated along the winding of the fabric. .

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to enable charging of a charging brush to a photosensitive member and to suppress the generation of burr and winding lines in an image. To provide an apparatus.

  In order to solve the above problems, the charging device of the present invention is a charging device including a charging brush for charging a photoconductor of an electrophotographic apparatus, wherein the charging brush is a roll-shaped driven by the photoconductor. It consists of an electrostatic flocking brush. The driven means that the roll-shaped charging brush comes into contact with the photosensitive member and rotates reversely at the same peripheral speed as that of the photosensitive member as the photosensitive member rotates. .

  According to said invention, the roll-shaped charging brush of a charging device consists of a roll-shaped electrostatic flocking brush, and is driven by a photoreceptor. This eliminates the need for a driving device for rotationally driving the charging brush. As a result, by causing the charging brush to follow the photoconductor, damage to the photoconductor by the charging brush can be reduced, the amount of photoconductor film scraping can be suppressed, and a longer life of the photoconductor can be expected. Further, the charging device can be miniaturized, and the cost can be reduced.

  Here, since the conventional charging brush is made of a fabric brush such as a pile weave brush, when the charging brush is driven by the photoconductor, charging spots such as brush stripes and winding stripes are generated in the printed image. .

  However, in the present invention, the charging brush is composed of a roll-shaped electrostatic flocking brush driven by a photoreceptor. As a result, the electrostatic flocking brush has an appropriate length, hardness, and density of the bristles, compared to a fabric brush such as a conventional pile weaving brush, so that it is possible to suppress electrification spots on the brush muscles. . In addition, the roll-shaped electrostatic flocking brush implants hair by flying the bristles electrostatically on a cylindrical base material coated with an adhesive. For this reason, since a ribbon-like cloth is not wound in a spiral shape to form a brush, streaky charged spots along the winding of the cloth do not occur.

  Therefore, it is possible to provide a charging device that enables the charging brush to follow the photosensitive member and that can suppress the generation of brush lines and winding lines in the image.

In the charging device of the present invention, the charging brush is an electrostatic flocking brush having a bristle having a fiber thickness of 3.3 dtex or less, a length of 1.0 mm or less, and a density of 50,000 / inch ² or more. It is preferable that

  Thereby, it is possible to obtain the optimum length, hardness, and density of the bristle that is driven by the photoconductor and suppresses the generation of the brush lines and the winding lines in the image.

Specifically, the charging brush composed of the electrostatic flocking brush having the above characteristics has a length of 1.0 mm or less, so that a frictional force that can be driven with respect to the photosensitive member can be obtained and driven. It becomes. Further, even if the brush hair is as short as 1.0 mm or less, it is composed of an electrostatic flocking brush having a fiber thickness of 3.3 dtex or less and a density of 50,000 pieces / inch ² or more. As a result, there are no occurrences of brush streaks in the printed image.

  In the charging device of the present invention, the charging brush is rotated in a direction opposite to the photoconductor, and the brush bristles of the charging brush have a brush root at a brush root with respect to the rotation direction of the charging brush. It is preferable that the hair is planted obliquely so that it precedes the original.

  That is, when the brush bristles of the charging brush are in perpendicular contact with the photosensitive member, a buckling force acts on the brush bristles. As a result, when the bristle is bent and a so-called bedding is attached, the contact pressure due to the elasticity of the bristle is lost.

  In this regard, in the present invention, the brush bristles of the charging brush are planted with slanted hair so that the tip of the bristles precedes the root of the brush hair with respect to the rotation direction of the charging brush. For this reason, buckling force does not act and it can always maintain fixed elasticity and contact pressure.

  In the charging device of the present invention, two charging brushes may be provided for charging the photosensitive member.

  Thereby, for example, it is possible to charge the two charging brushes with a potential difference. As a result, the surface potential of the photoconductor can be applied with the first charging brush, and the surface potential of the photoconductor can be set to an appropriate value with the second charging brush. Can be set well.

  The two charging brushes can be provided in this way because the charging brush is driven by the photosensitive member, and as a result, a driving device is not required and a space can be reduced. This is because the charging brush is made of an electrostatic flocking brush and the charging brush can be reduced in diameter.

  As described above, in the charging device of the present invention, the charging brush is composed of a roll-shaped electrostatic flocking brush driven by a photoreceptor.

  Therefore, there is an effect that it is possible to provide a charging device that can follow the charging brush to the photosensitive member and can suppress the generation of the brush stripes and the winding stripes in the image.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a configuration of a charging device according to an embodiment of a charging device in the present invention. FIG. 2 is an overall configuration diagram illustrating an image forming unit of an electrophotographic apparatus including the charging device. It is a block diagram which shows other embodiment of the charging device in this invention. It is a top view which shows the image produced with the electrophotographic apparatus provided with the said charging device. It is a graph which shows the time-dependent change of the film thickness in the photosensitive drum of the electrophotographic apparatus provided with the said charging device. It is a front view which shows the structure of the conventional charging device. It is a top view which shows the marbling-like reinforcement in the image produced with the electrophotographic apparatus provided with the said conventional charging device. It is a top view which shows the winding trace which runs diagonally in the image produced with the electrophotographic apparatus provided with the said conventional charging device.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

  FIG. 2 is a front view schematically showing the structure of the image forming unit in the electrophotographic apparatus provided with the charging device of the present embodiment. The electrophotographic apparatus outputs data read by a scanner provided in the electrophotographic apparatus or data from an external device (for example, an image processing apparatus such as a personal computer) connected to the electrophotographic apparatus as an image. Is.

  As shown in FIG. 2, the image forming unit 40 includes a photosensitive drum 1 as a photosensitive member, a charging device 30, an exposure device 3, a developing device 10, a transfer roll 4, a conveyance belt 5, and a cleaning device. The charging device 30, the exposure device 3, the developing device 10, the transfer roll 4, the transport belt 5, and the cleaning device 20 are arranged in this order around the photosensitive drum 1 in the rotation direction. It has become the composition.

  The photosensitive drum 1 is an electrostatic latent image carrier in an electrophotographic apparatus and has a cylindrical shape.

  The charging device 30 is for making physical contact with the photosensitive drum 1 to uniformly charge the surface of the photosensitive drum 1 to a predetermined potential. The charging device 30 includes a charging brush 31, and the charging brush 31 is installed adjacent to and opposite to the photosensitive drum 1 with the rotation axes thereof being parallel to each other. The charging device 30 will be described in detail later.

  The exposure device 3 exposes the surface of the photosensitive drum 1 charged by the charging device 30 with a laser beam or the like based on data from an image processing apparatus such as a personal computer, for example, so that the surface of the photosensitive drum 1 is statically exposed. This is for forming an electrostatic latent image. As the exposure apparatus 3, for example, a semiconductor laser or a light emitting diode can be used.

  The developing device 10 supplies a developer to the surface of the photosensitive drum 1, and develops, that is, develops the electrostatic latent image formed on the surface of the photosensitive drum 1 as a developer image. In the developing device 10 of the present embodiment, for example, a developer made of non-magnetic one-component toner is used, and a so-called non-magnetic one-component developing system is adopted. In the present invention, not only the non-magnetic single component toner but also all developers can be targeted.

  The conveyance belt 5 is for conveying a recording medium 6 such as PPC (Plain Paper Copy) paper to the photosensitive drum 1 after a developer image is formed on the surface of the photosensitive drum 1.

  The transfer roll 4 is for transferring the developer image on the surface of the photosensitive drum 1 to a recording medium 6 as a transfer material. The surface direction of the sheet metal and the surface direction of the recording medium 6 are parallel to each other. It is installed so as to be adjacent to the photosensitive drum 1 with the conveyance belt 5 interposed therebetween. The recording medium 6 is, for example, paper, OHP, or the like. The transfer roll 4 is made of, for example, a urethane rubber roll.

  The cleaning device 20 includes a cleaning brush 21, a solid lubricant supply device 22, and a cleaning blade 23, and is for removing developer and paper dust remaining on the surface of the photosensitive drum 1. .

  The operation of forming an image in the electrophotographic apparatus having the above configuration will be described below with reference to FIG.

  The surface of the photosensitive drum 1 is uniformly charged by the charging device 30. The photosensitive drum 1 whose surface is charged is exposed based on data by the exposure device 3, and an electrostatic latent image is formed on the surface of the photosensitive drum 1. Then, the developer is supplied to the surface of the photosensitive drum 1 by the developing roller 11 through the developer supply roll 12 of the developing device 10, and the electrostatic latent image on the surface of the photosensitive drum 1 is developed and visualized. It becomes. Subsequently, the recording medium 6 is conveyed to the photosensitive drum 1 by the conveyance belt 5, and the developer image on the surface of the photosensitive drum 1 is transferred to the recording medium 6 by the transfer roll 4. Then, residual toner, paper dust, and the like are removed from the photosensitive drum 1 after the transfer by the cleaning brush 21 and the cleaning blade 23. Image formation is performed in such a cycle.

  Next, the details of the charging device 30 of the present embodiment will be described.

  As shown in FIG. 1, the charging device 30 according to the present embodiment includes a charging brush 31 formed of a roll-shaped brush, a shaft 32 that is a rotating shaft, and a voltage application device 33 connected to the shaft 32. The charging brush 31 is disposed so as to be adjacent to and opposed to the photosensitive drum 1 with the shaft 32 that is the rotating shaft of the charging brush 31 and the rotating shaft direction of the photosensitive drum 1 being parallel to each other.

  Here, in the charging device 30 according to the present embodiment, the charging brush 31 is driven by the photosensitive drum 1, that is, is rotated around. For this reason, the shaft 32 is rotatably supported on a wall surface (not shown), and a drive mechanism for rotationally driving the shaft 32 is not provided. Specifically, the charging brush 31 is rotated only by contacting the photosensitive drum 1. For example, when the photosensitive drum 1 rotates clockwise at a peripheral speed of 100 mm / sec, the charging brush 31 is charged. The brush 31 rotates counterclockwise at a peripheral speed of 100 mm / sec.

  As shown in FIG. 1, the charging brush 31 is formed by raising brush hairs 31b on a columnar base material 31a. Specifically, the brush hairs 31b are coated with an adhesive on the base material 31a. The brush bristles 31b are electrostatically implanted. This electrostatic flocking is, for example, by placing a large number of finely cut brush hairs 31b charged to negative polarity and applying positive polarity to the base material 31a, thereby making each brush hair 31b electrostatically charged. The technique of flocking to the base material 31a coated with an adhesive.

  By the way, as described above, the charging brush 31 in the charging device 30 of the present embodiment is driven by the photosensitive drum 1. For this reason, a driving device for rotationally driving the charging brush 31 becomes unnecessary. As a result, by causing the charging brush 31 to follow the photosensitive drum 1, damage to the photosensitive drum 1 due to the charging brush 31 can be reduced, the amount of photoconductor film scraping can be suppressed, and the height of the photosensitive drum 1 can be reduced. Life expectancy can be expected. Further, the charging device 30 can be downsized, and the cost can be reduced.

  Here, since the conventional charging brush is made of a fabric brush such as a pile weave brush, when the charging brush is driven by the photosensitive drum 1, charging spots such as brush stripes and winding stripes occur in the printed image. It was.

  However, in the present embodiment, the charging brush 31 is a roll-shaped electrostatic flocking brush that is driven by the photosensitive drum 1. As a result, the electrostatic flocking brush has an appropriate length, hardness, and density of the bristles, compared to a fabric brush such as a conventional pile weaving brush, so that it is possible to suppress electrification spots on the brush muscles. . In addition, the roll-shaped electrostatic flocking brush implants hair by electrostatically flying the bristles onto a cylindrical base material 31a coated with an adhesive. For this reason, since a ribbon-like cloth is not wound in a spiral shape to form a brush, streaky charged spots along the winding of the cloth do not occur.

  Furthermore, since the charging brush 31 is an electrostatic flocking brush, the charging brush 31 has a small diameter, which also allows the charging device 30 to be reduced in size and cost. Further, by causing the charging brush 31 to follow the photosensitive drum 1, the ratio of injection charging can be increased and discharge products can be suppressed, and the life of the photosensitive drum 1 can also be increased.

  Therefore, it is possible to provide the charging device 30 that enables the charging brush 31 to follow the photosensitive drum 1 and that can suppress the generation of brush lines and winding lines in the image.

Further, in the charging device 30 of the present embodiment, the charging brush 31 has a bristle having a fiber thickness of 3.3 dtex or less, a length of 1.0 mm or less, and a density of 50,000 / inch ² or more. It preferably consists of an electrostatic flocking brush.

  Accordingly, it is possible to obtain the optimum length, hardness, and density of the brush hair 31b that is driven by the photosensitive drum 1 and that suppresses the generation of the brush stripes and the winding stripes in the image.

  Specifically, since the charging brush 31 made of the electrostatic flocking brush having the above characteristics is 1.0 mm or less in length, a frictional force that can be driven with respect to the photosensitive drum 1 is obtained. Follow-up is possible.

Further, even if the brush bristles 31b have a length of 1.0 mm or less, the electrostatic flocking brush having a fiber thickness of 3.3 dtex or less and a density of 50,000 pieces / inch ² or more. As a result, there is no occurrence of brush streaks in the printed image.

  Here, when the bristles 31b of the charging brush 31 are in perpendicular contact with the photosensitive drum 1, a buckling force acts on the bristles 31b. As a result, when the bristles 31b are bent and become a so-called sleeping bed, the contact pressure due to the elasticity of the bristles 31b is lost.

  Therefore, in the present embodiment, the bristles 31b of the charging brush 31 are planted with slanted hair so that the tip of the bristles precedes the root of the brush hair with respect to the rotation direction of the charging brush 31. For this reason, buckling force does not act and it can always maintain fixed elasticity and contact pressure.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIG. Configurations other than those described in the present embodiment are the same as those in the first embodiment. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are given the same reference numerals, and explanation thereof is omitted.

  As shown in FIG. 3, the charging device 30 ′ of the present embodiment is provided with two charging brushes 31 for charging the photosensitive drum 1 in addition to the configuration of the charging device 30 of the first embodiment. It has been.

  Thereby, for example, the voltage application device 33 is provided on the charging brush 31 on the downstream side in the rotation direction of the photosensitive drum 1, and the voltage application device 34 is provided on the charging brush 31 on the upstream side in the rotation direction of the photosensitive drum 1. As a result, the two charging brushes 31 can be charged with a potential difference. As a result, the first upstream charging brush 31 imparts a high surface potential to the photosensitive drum 1, and the second downstream charging brush 31 sets the surface potential of the photosensitive drum 1 to an appropriate value. The surface potential of the photosensitive drum 1 can be set with high accuracy.

  The two charging brushes 31 and 31 can be provided in this way because the charging brush 31 is driven by the photosensitive drum 1 and, as a result, a driving device is not required and a space can be reduced. This is because the charging brush 31 is made of an electrostatic flocking brush and the charging brush 31 can be reduced in diameter.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments can be appropriately combined. Such embodiments are also included in the technical scope of the present invention.

  In order to confirm the effect of the charging device 30 of the present embodiment, various performance evaluation experiments were performed.

[Example 1]
First, using the charging brush 31 of the charging device 30 of the present embodiment, an evaluation test was performed on the followability to the photosensitive drum 1 and the image quality.

As a test body, as shown in Table 1, about the fiber thickness of the charging brush 31, what used the fineness of 2.3 decitex (dtex)-6.1 decitex (dtex) was used. The fiber length was 0.5 mm to 1.5 mm. Furthermore, the flocking density was 45,000 / inch ^{2 to} 150,000 / inch ² . In addition, decitex (dtex) is defined as “when the weight of a 10,000 m long fiber (yarn) is N grams, the fiber (yarn) is N decitex (dtex)”. This is a unit representing the thickness of the thread. One dtex is equivalent to the conventional 0.9 denier (D).

  As test conditions, the electrophotographic apparatus used an A4 color tandem machine, the peripheral speed of the photosensitive drum 1 was 100 mm / sec, and a 2N spring load was applied to both ends of the charging brush 31. The brush application voltage was a DC voltage of −1 kv. Further, the outer diameter of the brush shaft was 8.5 mm, and the evaluation image was a 1 on / 1 off image at 600 dpi. The 1 on / 1 off image means an image printed at every other dot at 600 dpi in the vertical and horizontal directions.

  As a result, as shown in Table 1, the test number No. 1 and test number no. When the fiber thickness indicated by 2 was 6.1 dtex and 4.1 dtex, it was not possible to follow, and scoring was also observed in the image quality.

On the other hand, test No. 3-Test No. In the case of the fiber thickness indicated by 12 of 2.3 dtex to 3.3 dtex, it can be driven, and there is no scoring in the image quality, as shown in FIG. It was good. However, test no. 7-Test No. When the fiber thickness indicated by 8 is 3.3 dtex, the fiber length is 1.2 mm to 1.5 mm, and the flocking density is 50,000 / inch ² , the follower is It was not smooth, and some brush streaks appeared in the image quality.

Furthermore, the test number No. When the fiber thickness indicated by 9 is 3.3 dtex, the fiber length is 1.0 mm, and the flocking density is 45,000 / inch ² , the follow-up was possible. However, some brushed lines appeared in the image quality.

As a result, the charging brush 31 having a bristle 31b with a fiber thickness of 3.3 dtex or less, a length of 1.0 mm or less, and a density of 50,000 / inch ² or more can be driven and has good image quality. Was confirmed.

[Example 2]
Next, a test was performed on the change with time of the film thickness of the photosensitive drum 1.

  The test conditions were as shown in Table 2.

That is, in the examples, the test specimen is a bristle 31b of an electrostatic flocking brush made of polyamide material, having a fiber thickness of 2.3 dtex, a length of the bristle 31b of 0.8 mm, and a density of 150. The charging brush 31 of 1,000 / inch ² was obtained.

  Further, the electrophotographic apparatus uses an A4 color tandem machine, the peripheral speed difference from the photosensitive drum 1 is 0 mm / sec (= driven), and a 2N spring load is applied to both ends of the charging brush 31 as a brush holding method. The amount of biting of the charging brush 31 into the photosensitive drum 1 was about 0.1 mm.

On the other hand, in the conventional example, the test specimen is a bristle of a pile woven brush made of a polyamide material, the fiber thickness is 2.3 dtex, the length of the bristle is 2 mm, and the density is 240,000 / inch. No. ² charging brush.

  The electrophotographic apparatus uses an A4 color tandem machine, and the peripheral speed difference from the photosensitive drum 1 is twice the peripheral speed of the charging brush in the same rotational direction as the peripheral speed of the photosensitive drum 1. . Furthermore, it fixed with the bearing at the both ends of the charging brush. The amount of biting of the charging brush 31 into the photosensitive drum 1 was about 0.5 mm.

  As a result, as shown in FIG. 5, in the conventional example, the film thickness of the photosensitive drum 1 after 20,000 prints has decreased is reduced by about 5 μm, whereas in the example, the print number 20,000 is reduced. The film thickness of the photosensitive drum 1 after the passage of the sheets decreased by 1 μm or less.

  As a result, it has been clarified that the charging brush 31 of this embodiment has a small decrease in the film thickness of the photosensitive drum 1.

  The present invention relates to a charging device including a charging brush for charging a photosensitive member of an electrophotographic apparatus, and is applicable to a charging device and an electrophotographic apparatus including the charging device.

1 Photoconductor drum (photoconductor)
20 Cleaning device 30 Charging device 30 'Charging device 31 Charging brush 31a Base material 31b Brush hair 32 Shaft 33 Voltage application device 34 Voltage application device 40 Image forming unit

Claims (4)

In a charging device provided with a charging brush for charging a photoreceptor of an electrophotographic apparatus,
The charging device, wherein the charging brush comprises a roll-shaped electrostatic flocking brush driven by the photoconductor. The charging brush is characterized in that the bristle is composed of an electrostatic flocking brush having a fiber thickness of 3.3 dtex or less, a length of 1.0 mm or less, and a density of 50,000 / inch ² or more. The charging device according to claim 1. The charging brush is rotated in the opposite direction to the photoreceptor,
3. The brush bristles of the charging brush are planted by beveling so that the tip of the bristles precedes the root of the brush hair with respect to the rotation direction of the charging brush. Charging device.   4. The charging device according to claim 1, wherein two charging brushes are provided for charging the photosensitive member.