JP2009037053A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for suppressing accumulation of toner with time in a brush of a charging brush member. <P>SOLUTION: This image forming apparatus comprises a photoreceptor 3 as an image carrier for carrying a latent image on a surface, a development apparatus 40 as a developing means for developing the latent image on the photoreceptor 3 with toner, and a charging brush roller 8 as a charging brush member in contact with the surface of the photoreceptor 3 to charge the surface. A printer having the image forming apparatus comprises an ultrasonic oscillator 7 as an oscillation applying means for applying oscillation, and a sheet 6 as a brush beating member for beating the brush of the charging brush roller 8 by applying oscillation from the ultrasonic oscillator 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile, and more particularly to cleaning of a charging brush member that charges the surface of an image carrier.

  2. Description of the Related Art Conventionally, there has been known an image forming apparatus that forms an electrostatic latent image on an image carrier by charging the image carrier with a charging unit and selectively erasing or reducing the charge with an exposure unit. As this charging means, those using corona discharge have been the mainstream. However, the charging means using corona discharge has a problem of generating a large amount of ozone.

  Thus, many contact-type charging units that contact the image bearing member with the charging unit without using corona discharge have been proposed as charging units employed in the image forming apparatus. In this contact-type charging means, the above-mentioned problems are solved, but foreign matters remaining on the image carrier, for example, transfer residual toner that could not be cleaned, paper dust of the transfer material, and the like are likely to adhere. As described above, if transfer residual toner or the like adheres to the charging unit and becomes dirty, charging unevenness is caused, and an abnormal image such as density unevenness is generated.

  In particular, when a brush member is used as the charging unit, transfer residual toner or the like penetrates deep into the brush, and the transfer residual toner or the like gradually accumulates in the brush over a long period of time. As described above, when transfer residual toner or the like accumulates in the brush, the transfer residual toner or the like causes an uneven charging due to anxiety of the discharge between the brush and the image carrier, and thus an abnormal image such as a density unevenness occurs.

  Conventionally, there has been known an image forming apparatus that temporarily captures a transfer residual toner on an image carrier by a toner temporary capturing member (for example, Patent Document 1 and Patent Document 2). When this type of image forming apparatus employs a so-called cleanerless, first, a temporary capturing process is performed in which the transfer residual toner is temporarily captured from the surface of the image carrier to the toner temporary capturing member. Next, a return process for returning the toner from the toner temporary capturing member to the surface of the image carrier by changing the bias condition or the like is performed at a predetermined timing such as after the end of the print job. Then, the transfer residual toner is transferred from the surface of the image carrier to the developer carrier of the developing device (for example, a developing roller), the transfer residual toner is finally collected in the developing device, and the transfer residual toner is reused. Yes.

  Even in this type of image forming apparatus, toner may accumulate on the toner temporary capturing member over a long period of time, thereby generating an abnormal image. For example, when a brush member is used as the toner temporary capturing member, toner scraped from the surface of the image carrier by a brush composed of a plurality of raised hairs is taken in between the raised hairs in the brush. Then, most of the taken-in toner stays at the tip of the brush and then smoothly reversely transitions to the surface of the image carrier in the returning process. However, after being taken into the brush, the toner may penetrate deep into the brush due to the influence of the behavior of the brush. As described above, when toner gradually accumulates in the deep part of the brush over a long period of time, an abnormal image is generated due to various factors.

  For example, when the toner temporary capturing member and the charging member are combined, the toner accumulated in the brush makes the discharge between the brush and the image carrier unstable, causing uneven charging, and abnormalities such as uneven density. Generate an image.

  In Patent Document 3, in order to remove toner adhering to the charging brush roller, image formation is performed by cleaning the charging brush roller by bringing the brush member into contact with the charging brush roller and scraping the toner from the charging brush roller to the brush member. A device has been proposed.

JP 2003-295725 A JP 2004-170530 A JP 2004-251940 A

  However, in the image forming apparatus described in Patent Document 3, since the toner adhered to the charging brush roller is scraped off by the brush member, the scraped toner adheres to the brush member, and the toner accumulates in the brush member over time. . Therefore, the cleaning performance of the brush member is deteriorated, and there arises a problem that the charging brush roller cannot be kept clean over time.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of suppressing toner accumulation over time in a brush of a charging brush member.

In order to achieve the above object, an invention according to claim 1 includes an image carrier that carries a latent image on the surface, developing means for developing the latent image on the image carrier with toner, and a surface of the image carrier. In an image forming apparatus provided with a charging brush member that comes into contact with and charges the surface, a vibration applying unit that applies vibration, and a brush that strikes the brush of the charging brush member by applying vibration from the vibration applying unit And a hitting member.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the image forming apparatus further comprises a transfer unit that transfers the toner image of the image carrier to a transfer body, and the image carrier in an area after the transfer by the transfer unit. After the toner adhering to the surface of the toner is temporarily captured by the charging brush member, the captured toner is returned to the surface while vibrating the brush hitting member at a predetermined timing. .
According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect, the vibration applying means is when the charging brush member is not in contact with the surface of the image carrier including the image forming area. The brush striking member is vibrated.
According to a fourth aspect of the present invention, in the image forming apparatus of the first, second, or third aspect, the brush striking member is a sheet member, and the leading end of the sheet member bites into and contacts the charging brush member. It is a feature.
According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the amount of biting of the brush striking member with respect to the charging brush member is from 0.5 [mm] to 1.5 [mm]. It is a feature.
According to a sixth aspect of the invention, in the image forming apparatus of the first, second, third, fourth, or fifth aspect, the image forming apparatus further comprises a displacement means for displacing the brush hitting member in a thrust direction.
According to a seventh aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, or sixth aspect, the vibration applying means is an ultrasonic vibrator.
According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the amplitude of the ultrasonic transducer is not less than 0.1 [μm] and not more than 300 [μm].
According to a ninth aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, fifth, sixth, seventh, or eighth aspect, the image carrier is located more than the portion where the image carrier and the charging brush member are in contact with each other. The transfer residual toner charging means for charging the transfer residual toner is provided on the upstream side of the body surface movement direction.
According to a tenth aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, fifth, sixth, seventh, eighth, or ninth aspect, the brush fibers provided on the charging brush member are configured with slanted hairs. It is characterized by that.
According to an eleventh aspect of the present invention, in the image forming apparatus of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, or tenth aspect, the coefficient of friction of the image carrier is 0.3 or less. It is characterized by this.
According to a twelfth aspect of the present invention, in the image forming apparatus of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, or eleventh aspect, the contact angle of the image carrier with respect to water is 90 degrees. It is the above, It is characterized by the above.
According to a thirteenth aspect of the present invention, there is provided the image forming apparatus according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh or twelfth aspects. It has a voltage applying means for applying an AC voltage on which a DC voltage is superimposed.
According to a fourteenth aspect of the present invention, in the image forming apparatus according to the thirteenth aspect, the voltage applying unit changes the frequency of the AC voltage to be applied between charging of image formation and the predetermined timing. Is.
According to a fifteenth aspect of the invention, in the image forming apparatus of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, or fourteenth aspect, the charging brush member is charged. It is a brush roller, and the position where the hitting member is in contact with the charging brush roller is a downstream side of the charging brush roller rotation direction with respect to the contact point between the charging brush roller and the image carrier. .
According to a sixteenth aspect of the present invention, in the image forming apparatus of the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelve, thirteenth, fourteenth, or fifteenth aspect, The portion in contact with the charging brush member is comb-shaped.

  Here, the “image forming area” is an area on the surface of the image carrier where an image is formed through a process of forming a latent image and a process of developing the latent image.

  In the present invention, the brush of the charging brush member can be hit by applying vibration from the vibration applying means to the brush hitting member. Accordingly, the toner accumulated in the brush of the charging brush member can be knocked out from the brush by mechanically knocking out the toner by the brush hitting member. Further, the toner struck from the inside of the brush is collected at a location where the toner can be collected, for example, by a developing unit via the surface of the image carrier. Therefore, the charging brush member can be kept clean over time without being affected by the struck toner.

  As described above, according to the present invention, there is an excellent effect that it is possible to suppress toner accumulation with time in the brush of the charging brush member.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of an electrophotographic color laser printer (hereinafter simply referred to as a printer) will be described.
First, a basic configuration of the printer according to the present embodiment will be described. FIG. 2 is a schematic configuration diagram illustrating a main part of the printer according to the present embodiment. The printer includes four process units 1Y, M, C, and K for forming toner images of respective colors of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). An optical writing unit 50, a registration roller pair 54, a transfer unit 60, and the like are also provided. Subscripts Y, M, C, and K added to the end of each symbol indicate members for yellow, magenta, cyan, and black, respectively.

  The optical writing unit 50 serving as a latent image forming means includes a light source composed of four laser diodes corresponding to each color of Y, M, C, and K, a regular hexahedral polygon mirror, a polygon motor for rotationally driving this, and an fθ lens. , Lenses, reflection mirrors and the like. The laser light L emitted from the laser diode reaches any one of four photoconductors described later while being reflected by any one surface of the polygon mirror and deflected as the polygon mirror rotates. The surfaces of the four photoconductors Y, M, C, and K are optically scanned by the laser beams L emitted from the four laser diodes, respectively.

  The process units 1Y, 1M, 1C, and 1K have drum-shaped photoconductors 3Y, 3M, 3C, and 3K as latent image carriers, and developing devices 40Y, 4M, 4C, and 3K that individually correspond to these. ing. The photoreceptors 3Y, 3M, 3C, and 3K are obtained by coating an organic photosensitive layer on a base tube made of aluminum or the like, and are driven to rotate in a clockwise direction in the drawing at a predetermined linear velocity by a driving unit (not shown). Then, it is optically scanned in the dark by an optical writing unit 50 that emits a laser beam L modulated based on image information sent from a personal computer (not shown) or the like, and static for Y, M, C, and K. Carries an electrostatic latent image.

[Configuration example 1]
FIG. 1 is an enlarged configuration diagram showing a process unit 1K for K among the four process units 1Y, M, C, and K together with its peripheral configuration. In the figure, a process unit 1K for K holds a photosensitive member 3K, a charging brush roller 8K, a neutralizing lamp (not shown), a developing device 40K as developing means, etc. as a single unit in a common unit casing (holding body). Thus, it can be attached to and detached from the printer body.

  The photosensitive body 3K for K, which is a charged body and an image carrier, has a surface of a conductive substrate made of an aluminum base tube coated with a photosensitive layer made of a negatively charged organic photophotoconductive substance (OPC). The drum has a diameter of about 24 [mm] and is driven to rotate in the clockwise direction in the drawing at a predetermined linear velocity by a driving means (not shown).

  The charging brush roller 8K includes a metal rotating shaft member that is rotatably supported by a bearing (not shown), and a brush composed of a plurality of conductive raised brushes erected on the peripheral surface thereof. The brushes of the charging brush roller 8K are each cut to a predetermined length, and examples of the material include resin materials such as nylon, acrylic, and Teflon (registered trademark). The photosensitive member 3K is in contact with the photosensitive member 3K while being driven to rotate counterclockwise in the drawing by a driving means (not shown) around the rotation shaft member.

  A charging power source 104 is connected to the charging brush roller 8K, thereby applying a charging bias by superimposing an AC voltage and a negative polarity DC voltage. By this application, at the contact portion between the charging brush roller 8K and the photoconductor 3K, a discharge is generated between each brushed brush and the photoconductor 3K, and the photoconductor 3K is uniformly charged with a negative polarity.

  An electrostatic latent image for K (having a negative polarity and a lower potential than the background) is formed on the surface of the uniformly charged K photoconductor 3K by optical scanning by the optical writing unit 50 described above. The electrostatic latent image is developed into a K toner image by the K developing device 40K.

  The developing device 40K for K has a developing roller 42K that exposes a part of the peripheral surface from an opening provided in the casing 41K. The developing roller 42K rotates while carrying K toner (not shown) accommodated in the casing 4K on its peripheral surface. The K toner carried on the surface of the developing roller 42K is conveyed to a developing area where the developing roller 42K and the photosensitive member 3K face each other or come into contact with the rotation of the developing roller 42K.

  In this developing area, negative K toner is applied from the roller side to the latent image between the developing roller 42K to which the negative developing bias output from the developing power source 102 is applied and the electrostatic latent image on the photosensitive member 3K. The developing potential that causes electrostatic movement to the side acts. Further, a non-development potential for electrostatically moving negative K toner from the background portion side to the roller side acts between the developing roller 42K and the uniformly charged portion (background portion) of the photoreceptor 3Y. The K toner on the developing roller 42K is separated from the roller by the action of the developing potential and is transferred to the electrostatic latent image on the photoreceptor 3K. By this transition, the electrostatic latent image on the photoreceptor 3K is developed into a K toner image. The K toner is primarily transferred onto an intermediate transfer belt 61 of a transfer unit, which will be described later, with the rotation of the photoreceptor 3K.

  After passing through the primary transfer nip, a pre-charging blade 9K made of a conductive material such as metal is in contact with the surface of the photoreceptor 3K before entering the contact position with the charging brush roller 8K. A precharging bias composed of a negative polarity DC voltage having the same polarity as that of the toner is applied to the precharging blade 9K by a precharging power source 105. The photosensitive member 3K is charged to a negative polarity at the contact portion with the pre-charging blade 9K and before and after the contact portion. At this time, a small amount of the reversely charged toner (plus polarity toner) contained in the transfer residual toner is charged to the normal minus polarity by the charge injection from the precharge blade 9K.

  The pre-charging bias described above has a larger value on the negative side than the DC component of the charging bias applied to the charging brush roller 8K, and the surface potential of the photoconductor 3K after pre-charging is greater than the DC component of the charging bias. Is a large value on the negative side. When the surface of the photoconductor 3K after pre-charging moves to the entrance of the contact position with the charging brush roller 8K, the toner adhering to the photoconductor 3K is taken into the brush due to the potential difference between the photoconductor 3K and the brush. It is. Thereafter, when the surface of the photoreceptor 3K is uniformly charged by the charging brush roller 8K, the potential becomes smaller than the potential of the brush, but the toner remains in the brush without being transferred to the surface of the photoreceptor 3. This is because the adhesion force between the brush adhering to the brushed brush and the raised brush due to van der Waals force or mirror image force is greater than the electrostatic force due to the potential difference between the photoreceptor 3 and the brush. In this way, the temporary acquisition process is performed.

  Note that, by setting the surface friction coefficient of the photoconductor 3K to 0.3 or less, the toner separating property from the photoconductor 3K is improved, so that the toner recoverability from the photoconductor 3K to the charging brush roller 8K is improved. be able to.

  Further, by using a photoreceptor having a low surface energy such that the contact angle of the photoreceptor 3K with respect to water is 90 degrees or more as the photoreceptor 3K, the adhesion force of the toner to the photoreceptor 3K is reduced. This facilitates the separation of the toner from the photoreceptor 3K, so that the toner recoverability from the photoreceptor 3K to the charging brush roller 8K is improved.

  On the other hand, for example, after a print job or during a paper interval in the continuous print mode, the non-image area on the surface of the photoreceptor 3K that has not carried the toner image passes through the contact position with the charging brush roller 8K. Perform processing (cleaning mode). In the returning process, as shown in FIG. 3, the precharging bias applied from the precharging power source 105 to the precharging blade 9K is switched to a positive DC voltage. Then, the surface of the photoreceptor 3K is charged with a positive polarity. At this time, the direct current component of the bias applied to the charging brush roller 8K is switched to one having a negative polarity but a smaller value than that in the temporary capturing process. When the surface of the photosensitive member 3K charged to the positive polarity by the pre-charging blade 9K moves to the entrance of the contact position with the charging brush roller 8K, the toner in the brush is pulled to the positive polarity and transferred to the surface of the photosensitive member 3K. To do. Thereafter, even if the surface of the photoreceptor 3K is uniformly charged to about 0 [V] by the charging brush roller 8K, the toner on the surface of the photoreceptor 3K is repelled by the negative polarity of the DC component of the brush, Stay on the surface of the body 3K.

  In the return process, it is desirable to employ an AC voltage or an AC voltage on which a DC voltage is superimposed as the bias applied to the charging brush roller 8K. This is because the toner particles are vibrated by the switching of the bias polarity by alternating current, so that the toner particles can be more smoothly transferred to the surface of the photosensitive member 3K by urging the toner particles from the brush. Further, the frequency of the AC voltage in the returning process is optimized from the frequency of the AC voltage during charging for image formation to the cleaning condition of the charging brush roller 8K so that the toner can be efficiently discharged from the charging brush roller 8K. It is desirable to change to

  For example, at the time of charging for image formation (printing mode), a charging bias in which an AC voltage having a relatively high frequency is superimposed on a DC voltage is applied to uniformly charge the photoreceptor 3Y. When the photoreceptor 3Y having a linear speed of 100 [mm / sec] is uniformly charged to -500 [V], the DC voltage is -500 [V], the peak-to-peak voltage of the AC voltage is 1.0 [kV], and the duty ratio is 50 [V]. %] And a frequency of 300 [Hz] are applied to the charging brush roller 8K. The peripheral speed ratio of the charging brush roller 8K to the photosensitive member 3K is 0.1 to 4.0 in the forward direction of the photosensitive member rotation direction. Thereby, at the time of charging for image formation, the surface potential of the photoreceptor 3K becomes uniform by applying a charging bias of a DC voltage on which an AC voltage having a relatively high frequency as described above is superimposed.

  At the time of the return process, a large electric field is formed between the photosensitive member 3K and the charging brush roller 8K so that the toner attached to the charging brush roller 8K moves toward the photosensitive member 3Y. A charging bias different from that is applied. As a result, the toner adhering to the charging brush roller 8K is moved to the photosensitive member 3K side and electrostatically cleaned. For example, when the photosensitive member 3Y having a linear speed of 100 [mm / sec] is uniformly charged to -500 [V], the DC voltage is -500 [V], the peak-to-peak voltage of the AC voltage is 1.0 [kV], and the duty ratio. A charging bias superimposed with 50 [%] and a frequency of 20 [Hz] is applied to the charging brush roller 8K. The peripheral speed ratio of the charging brush roller 8K to the photosensitive member 3K is 0.1 to 4.0 in the forward direction of the photosensitive member rotation direction.

  At the time of the return processing, a DC voltage on which an AC voltage having a lower frequency than that at the time of charging for image formation is applied is applied so that the surface potential of the photosensitive member 3K is not uniform, and the shape corresponding to the waveform shape of the AC voltage is obtained. To be. By forming such a surface potential shape of the photoreceptor 3K, an electric field having the same magnitude as the peak-to-peak voltage of the AC voltage is formed due to the difference between the AC voltage of the charging bias and the surface potential. Therefore, the toner adhering to the charging brush roller 8K is easily moved to the photosensitive member 3K side by a large electric field, and the cleaning property of the charging brush roller 8K can be improved.

  The process unit 1K for K has been described so far, but the process units 1Y, 1M, and 1C for other colors have the same configuration as the process unit 1K for K, and thus description thereof is omitted.

  In FIG. 2 described above, a transfer unit 60 is disposed below the process units 1Y, 1M, 1C, and 1K for each color. The transfer unit 60 moves the endless intermediate transfer belt 61 endlessly in the counterclockwise direction in the drawing while being stretched by a plurality of stretching rollers. Specifically, the plurality of stretching rollers are a driven roller 62, a driving roller 63, four primary transfer bias rollers 66Y, M, C, K, and the like.

  The driven roller 62, the primary transfer bias rollers 66Y to 66K, and the drive roller 63 are all in contact with the back surface (loop inner peripheral surface) of the intermediate transfer belt 61. The four primary transfer bias rollers 66Y, 66M, 66C, and 66K are rollers in which a metal core is covered with an elastic body such as a sponge, and Y, M, C, and K photoconductors 3Y, The intermediate transfer belt 61 is sandwiched by being pressed toward M, C, and K. As a result, four primary transfer nips for Y, M, C, and K are formed in which the four photoconductors 3Y, M, C, and K and the intermediate transfer belt 61 are in contact with each other with a predetermined length in the belt moving direction. ing.

  A primary transfer bias that is constant current controlled by a transfer bias power source (not shown) is applied to the cores of the four primary transfer bias rollers 66Y, 66M, 66C, and 66K. As a result, transfer charges are applied to the back surface of the intermediate transfer belt 61 via the four primary transfer bias rollers 66Y, 66M, 66C, 66K, and the intermediate transfer belt 61 and the photoreceptors 3Y, M, A transfer electric field is formed between C and K. In this printer, the primary transfer bias rollers 66Y, 66M, 66C, and 66K are provided as the primary transfer means. However, a brush, a blade, or the like may be used instead of the rollers. A transfer charger or the like may be used.

  The Y, M, C, and K toner images formed on the photoreceptors 3Y, 3M, 3C, and 3K for each color are transferred onto the intermediate transfer belt 61 in a primary transfer nip for each color. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 61.

  A secondary transfer bias roller 67 is in contact with the driving roller 63 on the intermediate transfer belt 61 from the belt front surface side, thereby forming a secondary transfer nip. A secondary transfer bias is applied to the secondary transfer bias roller 67 by a voltage applying means including a power source and wiring (not shown). As a result, a secondary transfer electric field is formed between the secondary transfer bias roller 67 and the grounded secondary transfer nip back roller 64. The four-color toner image formed on the intermediate transfer belt 61 enters the secondary transfer nip as the belt moves endlessly.

  The printer includes a paper feed cassette (not shown), and accommodates a recording paper bundle in which a plurality of recording papers P are stacked therein. Then, the uppermost recording paper P is sent out to the paper feed path at a predetermined timing. The fed recording paper P is sandwiched in a registration nip of a registration roller pair 54 disposed at the end of the paper feed path.

  The registration roller pair 54 rotates both rollers in order to sandwich the recording paper P sent from the paper feed cassette into the registration nip. However, as soon as the leading edge of the recording paper P is sandwiched, both rollers rotate. Stop. Then, the recording paper P is fed toward the secondary transfer nip at a timing at which the recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 61. At the secondary transfer nip, the four-color toner images on the intermediate transfer belt 61 are collectively transferred onto the recording paper P by the action of the secondary transfer electric field and the nip pressure, and become a full-color image combined with the white color of the recording paper P. .

  The recording paper P on which the full-color image is formed in this manner is discharged from the secondary transfer nip, and then sent to a fixing device (not shown) to fix the full-color image.

  The secondary transfer residual toner adhering to the surface of the intermediate transfer belt 61 after passing through the secondary transfer nip is removed from the belt surface by the belt cleaning device 68.

  In the printer having the above-described basic configuration, the four process units 1Y, 1M, 1C, and 1K, the optical writing unit, and the like form an image forming unit that forms a toner image on the moving surface of the photoconductor as an image carrier. Is functioning as In addition, the charging brush roller 8K, the charging power source 104, and the like function as a temporary toner capturing unit that performs a temporary capturing process and a returning process.

  In the present embodiment, as shown in FIG. 1, the toner adhered to the brush of the charging brush roller 8K on the downstream side in the rotation direction of the charging brush roller from the contact point between the charging brush roller 8K of the charging brush roller 8K and the photosensitive member 3K. A sheet 6 is provided as a brush hitting member for hitting off. As a result, the charging brush roller 8K rotates, so that the brush of the charging brush roller 8 is struck by the sheet 6, and the toner adhering to the brush can be struck down. Further, by providing the sheet 6 on the downstream side in the rotation direction of the charging brush roller with respect to the contact point, the toner struck from the charging brush roller 8K by the sheet 6 as shown in FIG. 4 is collected again by the charging brush roller 8K. Can be suppressed.

  Further, as shown in FIG. 5, the sheet 6 is vibrated by the ultrasonic vibrator 7 during the return process (cleaning mode), and the vibration of the sheet 6 hits the brush to adhere to the charging brush roller 8K. The toner is easily separated from the brush. That is, when the sheet 6 is vibrated in this way, the sheet 6 vibrates more than when the sheet 6 does not vibrate, so that the brush is struck by the sheet 6, and as can be seen from the experimental results described later, the charging brush roller 8K. The toner can be struck efficiently. The amplitude of the ultrasonic transducer 7 is desirably 0.1 [μm] or more and 300 [μm] or less. This is because if the amplitude of the ultrasonic transducer 7 is too small, the effect of knocking out by vibration cannot be obtained, and if the amplitude is too large, the brush is damaged.

  Further, as shown in FIGS. 1 and 6, the leading edge of the sheet 6 is in contact with the circumference of the charging brush roller 8K (inside the brush), thereby promoting the knocking-off effect. It is desirable that the amount of biting of the sheet 6K with respect to the brush at this time is 0.5 mm to 1.5 mm. This is because if the amount of biting is too small, the effect obtained by vibrating the sheet 6 cannot be sufficiently obtained, and if the amount of biting is too large, the brush is elastically deformed.

[Modification 1]
In the first modification, as shown in FIGS. 7 and 8, the sheet 6 can be displaced in the thrust direction with respect to the charging brush roller 8K by a driving means (not shown). As a result, a thrusting force in the thrust direction is applied, and the toner can be further knocked down from the charging brush roller 8, so that the toner discharge performance in the returning process is improved.

[Modification 2]
In the second modification, the brush of the charging brush roller 8 has bevel hairs as shown in FIG. By making the brush slant in this way, the brush strikes the photoreceptor 3 from an oblique direction, so that the toner on the surface of the photoreceptor 3 can be easily collected.

[Modification 3]
In the third modification example, as shown in FIG. 10, the sheet 16 having a comb-shaped contact portion with the charging brush roller 8 is provided so as to contact the charging brush roller 8. As a result, the sheet 16 and the brush are intertwined with each other so that the toner can be effectively knocked off or scraped off from the brush, and the toner discharge performance from the charging brush roller 8 to the surface of the photosensitive member in the returning process is improved. be able to.

[Experiment]
Next, experiments conducted by the present inventors will be described.
In the printer testing machine shown in FIG. 11, the inventors set a monochrome half chart (halftone gradation image) on an A4 sheet to 5% image area ratio under the conditions of each experimental example described later. I printed it. Then, after printing up to 5000 sheets continuously, the degree of contamination of the charging brush roller 8 and the image density unevenness were evaluated. Specifically, as shown in Table 1, in the evaluation of the contamination of the charging brush roller 8, the evaluation was made in three stages: contamination (x), slight contamination (Δ), and no contamination (◯). Further, in the evaluation of the image density unevenness, the evaluation was made in three stages: unevenness (×), unevenness, but within an acceptable range (Δ) and no unevenness (◯).

The specific conditions of the testing machine at this time were one-component contact development for the developing device, a pulverized toner having a volume average particle size of 8.5 [μm] as the toner, and an externally added toner. The charging brush roller 8 forms a brush by standing a plurality of flocked fibers made of conductive fibers having a volume resistivity of about 10 ⁸ [Ω · cm] on a rotating shaft member having a diameter of 5 [mm]. A roller having a diameter of 11 [mm] was used.

  Then, a predetermined charging bias is applied by the charging power source 106 to cause a discharge between the charging brush roller 8 and the photosensitive member 3, so that the surface of the photosensitive member is uniformly charged to a predetermined charging potential. At the same time, the transfer residual toner adhering to the photoreceptor 3 is transferred to the brush of the charging brush roller 8 by the above-described synergistic action such as the charging bias, physical contact with the brush, and scraping, and is temporarily captured. Then, at the timing of the end of the print job or at the interval between sheets, the charging bias is switched to a value that makes it easy to reversely transfer the captured transfer residual toner onto the photoconductor 3, and the transfer residual toner captured on the brush is exposed to light. After being re-transferred onto the body 3, it is collected from the photoreceptor 3 into the developing device.

Further, the charging brush roller 8 has a surface resistance of 10 ⁸ [Ω · cm] and a thickness of 0.1 [mm] as a hitting member for hitting off toner adhering to the brush of the charging brush roller 8 unless otherwise specified. The PVDF sheet is in contact with the brush inside with a bite amount of 0.8 [mm]. The PVDF sheet is in contact with an ultrasonic vibrator 7 that vibrates at a frequency of 20 [kHz] and an amplitude of 10 [μm], and the ultrasonic vibrator 7 causes toner to be applied from the charging brush roller 8 to the surface of the photoreceptor. The PVDF sheet is vibrated during the reversion process for transferring.

  Further, the linear velocity of the photosensitive member 3 is preferably in the range of 50 to 300 [mm / s], and is set to 100 [mm / s] in this experiment. If the linear velocity of the photosensitive member 3 is higher than 300 [mm / s], it passes through the contact portion between the charging brush roller 4Y and the photosensitive member 3Y in a short time, and the toner moves well from the charging brush roller 4Y. I can't.

  Further, the peripheral speed ratio of the charging brush roller 8 to the photosensitive member 3 is preferably in the range of 0.1 to 4.0.

  The film thickness of the surface layer of the photoreceptor 3 is preferably in the range of 15 to 30 [μm], and in this experiment, it is set to 26 [μm]. If the film thickness of the photoconductor 3 is too thin, it becomes difficult for electric charges to be deposited on the surface of the photoconductor 3 and a sufficient surface potential cannot be obtained, and if it is too thick, the sensitivity becomes poor and a good electrostatic latent image cannot be formed.

  Table 2 shows the experimental conditions of each experimental example, and Table 3 shows the experimental results of each experimental example.

  From Table 3, as shown in Experimental Example 1, Experimental Example 2, and Experimental Example 3, when the PVDF sheet is vibrated by the ultrasonic vibrator 7, the charging brush roller 8 is not contaminated, and the charging brush roller 8 is formed by the PVDF sheet. It turns out that it was cleaned well. Further, this can suppress the deterioration of the charging performance of the charging brush roller 8 with the passage of time, and it can be seen that good image formation can be performed without causing uneven image density.

  When the PVDF sheet is not vibrated by the ultrasonic vibrator 7 as in Experimental Example 4, the toner attached to the brush of the charging brush roller 8 cannot be sufficiently struck by the PVDF sheet, and the toner is slightly contaminated with the toner. I understand that there is. Therefore, it can be seen that the charging performance of the charging brush roller 8 is deteriorated, and the image density unevenness occurs within the allowable range in actual use.

  In the case where the PVDF sheet is not brought into contact with the charging brush roller 8 as in Experimental Example 5, the electrostatic transfer of the electrostatic toner from the charging brush roller 8 to the photosensitive member surface in the returning process is sufficient. Thus, it can be seen that the toner cannot be discharged from the toner, and the toner is accumulated on the charging brush roller 8 over time, so that the toner is smeared on the brush. Therefore, it can be seen that the charging performance of the charging brush roller 8 is deteriorated, and the image density unevenness is unacceptable in actual use.

As described above, according to the present embodiment, the photosensitive member 3 that is an image carrier that bears a latent image on the surface, the developing device 40 that is a developing unit that develops the latent image on the photosensitive member 3 with toner, and the photosensitive member 3. In a printer which is an image forming apparatus provided with a charging brush roller 8 which is a charging brush member which comes into contact with and charges the surface, an ultrasonic vibrator 7 which is a vibration applying means for applying vibration, and an ultrasonic vibration It has a sheet 6 which is a brush hitting member that hits the brush of the charging brush roller 8 by applying vibration from the child 7. Accordingly, the toner accumulated in the brush of the charging brush roller 8 can be knocked out from the brush by mechanically knocking out the sheet 6. Further, the toner struck from the brush is collected at a location where the toner can be collected, for example, by a developing device via the surface of the photoreceptor 3. Therefore, the charging brush roller 8 can be kept clean over time without being affected by the struck toner. That is, toner can be prevented from accumulating in the brush of the charging brush roller 8 over time.
Further, according to the present embodiment, the image forming apparatus includes the primary transfer bias roller 66 that is a transfer unit that transfers the toner image of the photosensitive member 3 to the intermediate transfer belt 61 that is a transfer body. After the toner adhering to the surface of the photoconductor 3 in the region is temporarily captured by the charging brush roller 8, the captured toner is returned to the surface while vibrating the sheet 6 at a predetermined timing. As a result, the charging brush roller 38, which is a temporary toner capturing member, can be cleaned over time, and an abnormal image is generated by transferring the toner from the charging brush roller 38 to the photosensitive member 2 during the temporary capturing process. Generation | occurrence | production can be suppressed.
Further, according to the present embodiment, the ultrasonic vibrator 7 vibrates the sheet 6 at times other than when the charging brush roller 8 is in contact with the photoconductor including the image forming area. As a result, no image is formed on the photosensitive member 2 that is in contact with the charging brush roller 8 while the sheet 6 vibrates. It is possible to suppress the occurrence of an abnormal image due to unevenness or defective writing.
Further, according to the present embodiment, the brush striking member is the sheet 6 that is the sheet 6 member, and the leading end of the sheet 6 is bitten into contact with the charging brush roller 8. Thereby, it is possible to promote the knocking-off effect due to vibration as compared with the case where the sheet 6 is placed against the brush outer peripheral surface of the charging brush roller 8.
Further, according to the present embodiment, the amount of biting of the sheet 6 with respect to the charging brush roller 8 is not less than 0.5 [mm] and not more than 1.5 [mm]. Thereby, if the amount of biting is too small, the effect obtained by vibrating the sheet 6 cannot be sufficiently obtained, and if the amount of biting is too large, the occurrence of problems such as the elastic deformation of the brush is suppressed. Can do.
Further, according to the present embodiment, by having the driving means that is a displacement means for displacing the sheet 6 in the thrust direction, a thrusting force in the thrust direction is applied, and the toner can be further knocked off from the charging brush roller 8. Therefore, the toner discharge performance in the returning process is improved.
Further, according to the present embodiment, since the vibration applying means is the ultrasonic vibrator 7, a minute vibration can be easily applied.
Further, according to the present embodiment, the amplitude of the ultrasonic transducer 7 is not less than 0.1 [μm] and not more than 300 [μm]. As a result, it is possible to suppress the occurrence of problems such as that the effect of knocking out by vibration is not obtained due to the amplitude of the ultrasonic transducer 7 being too small, or the brush is damaged due to the amplitude being too large. it can.
In addition, according to the present embodiment, the pre-charging blade 9 that is a transfer residual toner charging unit that charges the transfer residual toner to the upstream side in the movement direction of the photosensitive member surface with respect to the portion where the photosensitive member 3 and the charging brush roller 8 contact each other Provided. As a result, the pre-charging blade 9 is charged so that the transfer residual toner can be easily recovered by the charging brush roller 8, and the recovery rate of the transfer residual toner of the charging brush roller 8 can be improved. Further, the amount of discharge during the return process can be increased.
In addition, according to the present embodiment, the brush which is the brush fiber provided on the charging brush roller 8 is configured with slanted hairs, so that the brush strikes the photoconductor 3 from an oblique direction so that it is on the surface of the photoconductor 3. The toner can be easily collected.
In addition, according to the present embodiment, since the coefficient of friction of the photosensitive member 3 is 0.3 or less, the toner separating property from the photosensitive member 3 is improved, so that the toner from the photosensitive member 3 to the charging brush roller 8 is improved. It is possible to improve the recoverability.
Further, according to the present embodiment, the adhesion force of the toner to the photoconductor 3 is reduced by using the low surface energy photoconductor such that the contact angle of the photoconductor 3 with respect to water is 90 degrees or more. As a result, the toner is easily separated from the photoconductor 3, so that the recoverability of the toner from the photoconductor 3 to the charging brush roller 8 is improved.
Further, according to the present embodiment, the charging brush roller 8 includes the charging power source 104 that is a voltage applying unit that applies an AC voltage or an AC voltage on which a DC voltage is superimposed. Accordingly, the toner is vibrated by the switching of the bias polarity by alternating current, thereby prompting the toner to be detached from the surface of the photosensitive member 3 during the temporary capturing process, so that the toner is more smoothly charged from the surface of the photosensitive member 3. It can be collected by the roller 8. Further, the toner can be transferred from the charging brush roller 8 to the surface of the photosensitive member 3 more smoothly by urging the toner from the brush of the charging brush roller 8 during the returning process.
Further, according to the present embodiment, the charging power source 104 changes the frequency of the AC voltage to be applied at the time of charging for image formation and at the predetermined timing. As a result, it is possible to efficiently discharge toner from the charging brush roller 8 to the photosensitive member 3 during the returning process.
Further, according to the present embodiment, the charging brush member is the charging brush roller 8, and the position where the sheet 6 contacts the charging brush roller 8 is higher than the contact portion between the charging brush roller 8 and the photoreceptor 3. It is the downstream side in the rotational direction. Thereby, it is possible to prevent the toner brushed off from the charging brush roller 8 by the sheet 6 from being collected again by the charging brush roller 8.
Further, according to the present embodiment, by using the sheet 16 having a comb shape as the brush hitting member, the sheet 16 and the brush are intertwined, and the toner is effectively hit from the brush. The toner can be removed, scraped off, and the like, and the discharging performance of the toner from the charging brush roller 8 to the surface of the photosensitive member in the returning process can be improved.

  In this embodiment, a printer that employs a cleanerless structure in which a charging unit that charges the photosensitive member and a temporary toner capturing unit that temporarily captures the transfer residual toner on the photosensitive member are shared by the same member, that is, a charging brush roller. However, the present invention is not limited to this. For example, an image forming apparatus that employs a cleanerless in which the charging unit and the toner temporary capturing unit are formed of separate members, or an image forming apparatus that does not employ a cleanerless having a cleaning device that cleans the photosensitive member may be used.

FIG. 3 is an enlarged configuration diagram illustrating a K process unit in the printer according to Configuration Example 1; 1 is a schematic configuration diagram of a printer according to an embodiment. The expanded block diagram which shows the process unit for K in return processing. FIG. 6 is a schematic diagram illustrating a location where toner that has been knocked down falls when a sheet is provided downstream of the contact location in the rotation direction of the charging brush roller. The control figure which showed the timing which performs a return process (cleaning mode). The schematic diagram which made the sheet | seat bite into the circumference (brush inside) of a charging brush roller, and was made to contact. FIG. 2 is a schematic configuration diagram of a printer configured to be able to displace a sheet biting into a charging brush roller in a thrust direction. FIG. 2 is a schematic configuration diagram of a printer configured to be able to displace a sheet in contact with a brush surface of a charging brush roller in a thrust direction. The schematic diagram of the charging brush roller by which the brush was comprised in the bevel. FIG. 3 is a schematic configuration diagram of a vicinity of a charging brush roller of a printer in which a contact portion with a charging brush roller 8K has a comb-like sheet. FIG. 3 is an enlarged configuration diagram illustrating a printer process unit used in an experiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Process unit 3 Photoconductor 6 Sheet 7 Ultrasonic vibrator 8 Charging brush roller 9 Pre-charging blade 40 Developing device 66 Primary transfer bias roller 102 Developing power source 104 Charging power source 105 Pre-charging power source 106 Charging power source

Claims (16)

An image carrier carrying a latent image on the surface;
Developing means for developing the latent image on the image carrier with toner;
In an image forming apparatus provided with a charging brush member that contacts the surface of the image carrier and charges the surface,
Vibration applying means for applying vibration;
An image forming apparatus comprising: a brush striking member that strikes a brush of the charging brush member by being imparted with vibration from the vibration imparting unit. The image forming apparatus according to claim 1.
Transfer means for transferring the toner image of the image carrier to a transfer body;
After the toner adhering to the surface of the image carrier in the area transferred by the transfer means is temporarily captured by the charging brush member, the toner captured while vibrating the brush hitting member at a predetermined timing is collected. An image forming apparatus, wherein the image forming apparatus is returned to the surface. The image forming apparatus according to claim 1 or 2,
The image forming apparatus, wherein the vibration applying means vibrates the brush hitting member when the charging brush member is not in contact with the surface of the image carrier including the image forming area. The image forming apparatus according to claim 1, 2 or 3.
The image forming apparatus according to claim 1, wherein the brush striking member is a sheet member, and a leading end of the sheet member is bitten into contact with the charging brush member. The image forming apparatus according to claim 4.
An image forming apparatus, wherein an amount of biting of the brush striking member with respect to the charging brush member is 0.5 [mm] or more and 1.5 [mm] or less. The image forming apparatus according to claim 1, 2, 3, 4, or 5.
An image forming apparatus comprising a displacement means for displacing the brush striking member in a thrust direction. The image forming apparatus according to claim 1, 2, 3, 4, 5 or 6.
The image forming apparatus, wherein the vibration applying means is an ultrasonic vibrator. The image forming apparatus according to claim 7.
An image forming apparatus, wherein an amplitude of the ultrasonic transducer is 0.1 [μm] or more and 300 [μm] or less. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7 or 8.
An image forming apparatus, comprising: a transfer residual toner charging unit configured to charge transfer residual toner upstream of a position where the image carrier and the charging brush member are in contact with each other in the moving direction of the image carrier surface. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9.
An image forming apparatus, wherein the brush fibers provided on the charging brush member are slanted. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.
An image forming apparatus, wherein the image bearing member has a friction coefficient of 0.3 or less. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.
An image forming apparatus, wherein the contact angle of the image carrier with water is 90 degrees or more. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12.
An image forming apparatus comprising: a voltage applying unit that applies an AC voltage or an AC voltage superimposed with a DC voltage to the charging brush member. The image forming apparatus according to claim 13.
The image forming apparatus, wherein the voltage applying means changes the frequency of the AC voltage to be applied between charging of image formation and the predetermined timing. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14.
The charging brush member is a charging brush roller, and the position where the hitting member contacts the charging brush roller is downstream of the charging brush roller rotation direction with respect to the contact point between the charging brush roller and the image carrier. An image forming apparatus. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15.
The image forming apparatus according to claim 1, wherein a portion of the brush striking member that contacts the charging brush member has a comb shape.

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