JP2007140023A - Image forming apparatus and scattered toner collecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus where scattered toner is collected with simple constitution and restrained from being discharged to the outside, and a scattered toner collecting method. <P>SOLUTION: A scattered toner collecting roller 4 is changeably connected to a power source 5 and a ground. When collecting the scattered toner, bias voltage is applied to the scattered toner collecting roller 4 from the power source 5, and also re-electrification voltage set to low voltage and high voltage is intermittently applied to a photoreceptor drum 2 by an electrifying means, so that the scattered toner collected by the scattered toner collecting roller 4 is discharged to the photoreceptor drum 2. The scattered toner 14 discharged to the photoreceptor drum 2 is collected by a developing means 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a scattered toner collecting method that collects scattered toner with a simple configuration and reduces discharge to the outside.

  In general, an electrophotographic toner image forming unit includes a photosensitive member as an image bearing member having a photosensitive layer on an outer peripheral surface, a charging unit that uniformly charges the outer peripheral surface of the photosensitive member, and a uniform charging unit using the charging unit. An exposure unit that selectively exposes the outer peripheral surface charged to form an electrostatic latent image, and a toner as a developer is applied to the electrostatic latent image formed by the exposure unit to form a visible image ( Developing means for forming a toner image).

  In such an image forming apparatus, the toner may be scattered from the developing unit and contaminate the inside and outside of the image forming apparatus due to the stirring and conveyance of the toner by the developing unit. For this reason, as described in Patent Document 1 and Patent Document 2, a scattered toner collecting roller for collecting scattered toner is provided in the vicinity of the developing unit so that the toner is not scattered from the developing unit. The toner collected by the scattered toner collecting roller is scraped off by the blade.

JP-A-10-339998 Japanese Patent Laid-Open No. 10-3220

  In the prior art described in Patent Document 1 and Patent Document 2, a dedicated toner scraping blade is provided on the scattered toner collecting roller. In this type of image forming apparatus, a cleaning blade for scraping off the remaining toner is provided in order to prevent the image quality from being deteriorated by the toner remaining on the photosensitive member as the image carrier. Therefore, a blade for scraping off unnecessary toner is provided on each of the photosensitive member and the scattered toner collecting roller, and a plurality of blades are required. For this reason, there existed a problem that a structure became complicated and cost increased.

  SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide an image forming apparatus and a scattered toner collecting method that collect scattered toner with a simple configuration and reduce discharge to the outside. It is to provide.

  An image forming apparatus according to the present invention that achieves the above object includes a charging unit, an exposure unit, a developing unit, a transfer unit, and a scattered toner collecting roller that is switched and connected to a power source and a ground. An image forming apparatus including an image forming unit, wherein a bias voltage is applied to the scattered toner collecting roller from the power source when the scattered toner cleaning mode after image formation is set by the control unit, and the photosensitive A recharging voltage is intermittently applied to the photosensitive drum by the charging means, the scattered toner collected by the scattered toner collecting roller is discharged to the photosensitive drum, a bias voltage is applied to the developing means, The scattered toner discharged to the photosensitive drum is collected by the developing means. According to such a configuration, the positive and negative scattered toner adhering to the scattered toner collecting roller is discharged to the photosensitive drum by electrical control. Thereafter, the toner is recovered from the photosensitive drum to the developing unit. For this reason, a toner scraping blade is not required for the scattered toner collecting roller, the configuration is simplified, and the cost can be reduced. Further, since the scattered toner is collected by the developing unit without using a cleaning blade, the collected toner is not deteriorated, and the image quality can be improved when performing image formation again. Furthermore, since the recharge voltage is intermittently applied to the photosensitive drum when the scattered toner is discharged from the scattered toner collecting roller, the photosensitive drum is subjected to divided exposure. For this reason, since the scattered toner is discharged from the scattered toner collecting roller to the photosensitive drum thinly and loosely, the scattered toner can be collected smoothly and efficiently by the developing means without applying an excessive burden.

  The image forming apparatus of the present invention is characterized in that the recharging voltage intermittently applied to the photosensitive drum is set to a different voltage between a low voltage and a high voltage. According to such a configuration, the positive and negative polarity scattered toner can be uniformly discharged from the scattered toner collecting roller to the photosensitive drum.

  In the image forming apparatus of the present invention, the image carrier and the developing unit are disposed in contact with each other to perform contact development processing. According to such a configuration, in the contact developing type image forming apparatus, the scattered toner can be effectively collected by the developing unit.

  In the image forming apparatus of the present invention, the image forming apparatus is a color image forming apparatus, and the scattered toner for each color is individually collected. According to such a configuration, in a color image forming apparatus using multiple colors such as three colors or four colors, scattered toner can be collected in each color while avoiding color mixing.

  The scattered toner collecting method of the present invention is provided with an image forming station provided with respective image forming units including a charging unit, an exposing unit, a developing unit, a transfer unit, and a scattered toner collecting roller around a photosensitive drum. A step in which the peripheral speed of the photosensitive drum and the peripheral speed of the scattered toner collecting roller are set to different values, and the transfer medium passes through the image forming station to form an image, and the scattered toner after image formation. In the cleaning mode, a bias voltage is applied to the scattered toner collecting roller, and a recharge voltage is intermittently applied to the photosensitive drum, and the scattered toner collected by the scattered toner collecting roller is applied to the photosensitive drum. And a step of collecting the scattered toner discharged to the photosensitive drum by the developing means. According to such a configuration, the scattered toner can be accurately collected in the developing unit by electrical control using an existing apparatus. Further, the scattered toner that is gradually and gradually discharged from the scattered toner collecting roller to the photosensitive drum can be effectively collected by the developing means.

  In the scattered toner recovery method of the present invention, the intermittent recharging voltage applied to the photosensitive drum includes a preceding low voltage application period and a subsequent high voltage application period. . According to such a configuration, scattered toner having both positive and negative polarities can be efficiently discharged onto the photosensitive drum. In addition, since the low voltage application period is included before the recharging voltage is applied, the scattered toner is smoothly discharged from the scattered toner collecting roller to the photosensitive drum without being subjected to sudden electrical stress. Is done.

According to the present invention, the following special effects can be obtained. (1) The scattered toner of positive and negative polarity adhering to the scattered toner collecting roller is discharged to the photosensitive drum by electrical control, and is collected from the photosensitive drum to the developing means. For this reason, a toner scraping blade is not required for the scattered toner collecting roller, the configuration is simplified, and the cost can be reduced. (2) Since the scattered toner is collected by the developing means without using a cleaning blade, the collected toner is not deteriorated, and the image quality can be improved when performing image formation again. (3)
Since the scattered toner is discharged from the scattered toner collecting roller to the photosensitive drum thinly and loosely, the scattered toner can be collected smoothly and efficiently by the developing means without applying an excessive burden. (4) Since the collected scattered toner can be reused for image formation, it is possible to effectively use toner resources. (5) Since the scattered toner is collected inside the apparatus to reduce the discharge of the scattered toner to the outside, an environment-friendly image forming apparatus and a scattered toner collecting method can be provided.

  Next, an embodiment of the present invention will be described with reference to the explanatory diagrams shown in FIGS. FIG. 2 partially illustrates the image forming apparatus 1 and is an explanatory diagram of a process of collecting the scattered toner with the scattered toner collection roller. In FIG. 2, 2 is a photosensitive drum (image carrier), 4 is a scattered toner collecting roller electrically connected to a power source 5 and a switch 6, and 7 is provided in the developing device 3 and is electrically connected to the power source 9. A developing roller 8 is connected to the toner supply roller 8. Reference numeral 11 denotes scattered toner scattered around the developing device 3 and the photosensitive drum 2. The black circle is a negatively charged toner having a negative polarity, and the white circle is a positively charged toner having a positive polarity. The switch 6 is released from the power source 5 and the scattered toner collecting roller 4 is connected to the ground. At this time, the negatively charged toner and the positive and negative polarity toners of the positively charged toner are attracted to the scattered toner collecting roller 4. The example in FIG. 2 is a contact-type image forming apparatus in which development is performed in a state where the photosensitive drum 2 and the developing roller 7 are in contact with each other. In order to facilitate understanding of the state of the scattered toner 11, The developing roller 7 is shown separated.

  FIG. 3 is an explanatory diagram of a process of discharging (discharging) the toner collected by the scattered toner collecting roller 4 in FIG. 2 to the photosensitive drum 2. At this time, the charging means (not shown) switches the potential of the photosensitive drum 2 between the high potential Va (−900 V) and the low potential Vb (−500 V) on the basis of 0 V (exposure potential). . Va and Vb correspond to recharging voltages applied to the photosensitive drum 2 when the cleaning mode is set by the control unit after image formation. Further, the switch 6 is connected to the power source 5, and a bias voltage of, for example, (DC−200 V + AC 2 kV) is applied to the scattered toner collecting roller 4. Details of the voltage control of the photosensitive drum 2 and the voltage control of the scattered toner collecting roller 4 will be described later with reference to the timing chart of FIG. Here, since the recharge voltage of the high potential and the low potential is intermittently applied to the photosensitive drum 2, the photosensitive drum 2 is subjected to divided exposure.

  When the potential of the photosensitive drum 2 is Va, positively charged toner indicated by white circles collected by the scattered toner collecting roller 4 is discharged to the photosensitive drum 2. That is, since the photosensitive drum 2 has a negative potential, positively charged toner having a potential opposite to that of the photosensitive drum 2 is discharged to the photosensitive drum 2. When the potential of the photosensitive drum 2 is Vb, negatively charged toner indicated by a black circle is discharged to the photosensitive drum 2. Reference numeral 12 denotes scattered toner discharged to the photosensitive drum 2. Since the photosensitive drum 2 and the developing roller 7 rotate in contact with each other, a part of the scattered toner 12 adheres to the developing roller 7 as the collected toner 13.

  In this example, both the photosensitive drum 2 and the scattered toner collecting roller 4 are formed as rotating bodies. With such a configuration, the scattered toner collection roller 4 rolls on the circumferential surface of the photosensitive drum 2 functioning as an image carrier. Therefore, the scattered toner adhering to the surface of the scattered toner collecting roller 4 can be efficiently discharged to the image carrier.

  FIG. 1 is an explanatory diagram of a process for collecting the scattered toner discharged to the photosensitive drum 2 by the developing roller 7. In FIG. 1, reference numeral 10 denotes charging means using, for example, a corona charger. The scattered toner collection roller 4 is opened from the power source 5 by switching a switch. A charge voltage Vc of DC-500V is applied to the photosensitive drum 2 again, so that the polarity of residual toner after printing and scattered toner adhering to the photosensitive drum 2 is made negative. Further, a bias voltage of about DC-200V is applied to the developing roller 7, for example. For this reason, the scattered toner having the negative polarity and the same polarity can be effectively collected from the photosensitive drum 2 to the developing roller 7. Reference numeral 13 denotes scattered toner collected on the developing roller 7. Note that unnecessary toner remaining on the photosensitive drum 2 after printing can also be collected.

  In the present invention, the scattered toner 12 discharged to the photosensitive drum 2 as shown in FIG. The collected scattered toner 13 is accommodated in a toner collecting case (not shown) and can be reused during image formation. Thus, since the scattered toner 14 is collected and reused, the toner resources can be effectively used.

FIG. 4 is a timing chart showing the processing process of the present invention over time. In this image forming apparatus, the applied voltage values are shown roughly.
A period from time ta to tb indicates a change in the photoreceptor (OPC) potential due to exposure during image formation. The initial potential is −500 V, the exposure potential is 0 V, and when the exposure potential is 0 V, an image is formed on the photosensitive drum.

  A period from time tc to td is a period for applying a developing bias, and a developing bias of about direct current (DC) −200 V is applied to the developing roller 7. At this time, a developing process is performed and scattered toner is generated. The image formation end time tb of the photosensitive drum 2 and the development end time td of the developing roller 7 are set to the same time.

  During the period from time te to tf, the scattered toner collecting roller 4 is biased off (GND), and the scattered toner is collected by the scattered toner collecting roller 4. A cleaning mode is set by a control device (not shown) after the time tb has elapsed, and a cleaning process after the image forming process (discharge of scattered toner from the scattered toner collecting roller 4 to the photosensitive drum 2 and development from the photosensitive drum 2). (Recovery to roller)

The period from time tb to tg is a period in which the photoreceptor (OPC) potential is 0V.
A bias voltage of DC−200 V + AC 2 kV is applied to the scattered toner collecting roller 4 at times tj to tl following this period. The period from time tj to tk is a period in which the photosensitive drum 2 is rotated one or more times. During this period, negatively charged toner is discharged to the photosensitive drum 2. The period from time tk to tl is a period in which the photosensitive drum 2 is rotated one or more times, and the reversely charged toner is discharged to the photosensitive drum 2 during this period. Accordingly, the negatively charged (negative polarity) toner and the reversely charged (positive polarity) toner adhering over the entire circumference of the scattered toner collecting roller 4 are dispersed and discharged on the surface of the photosensitive drum 2.

  The period from time tg to th is a period in which the photosensitive drum (OPC) is recharged and a low potential of −500 V is applied with reference to 0 V (exposure potential). This period is a period during which the negatively charged toner is collected on the photosensitive drum 2. The period from time th to ti is a period in which the photosensitive member (OPC) potential is recharged and a high potential of −900 V is applied with reference to 0 V (exposure potential). This period is a period for collecting the reversely charged toner on the photosensitive drum 2. Here, both the low potential voltage applied during the period of time tg to th and the high potential voltage applied during the period of time th to ti are intermittently applied to the photosensitive drum. For this reason, the photosensitive drum is subjected to divided exposure. For this reason, since the scattered toner is discharged from the scattered toner collecting roller to the photosensitive drum thinly and sparsely, the subsequent collection of the scattered toner by the developing means can be performed smoothly and efficiently without imposing an excessive burden. . In addition, since the low voltage application period is included before the recharging voltage is applied, the scattered toner is smoothly discharged from the scattered toner collecting roller to the photosensitive drum without being subjected to sudden electrical stress. Is done.

In this way, after discharging scattered toner of positive and negative polarity to the photosensitive drum 2,
In the period from time tm to tn, the charging voltage Vc of DC-500V is applied to the photosensitive drum 2 again, and the polarity of the unnecessary toner adhering to the photosensitive drum 2 is made negative. Next, a bias voltage of about −200 V DC is applied to the developing roller 7 during the period from time tp to tr. In this way, in the period from time tp to tr, the scattered toner is collected by the developing roller 7 as described with reference to FIG. In this example, the polarity of the unnecessary toner adhering to the photosensitive drum 2 is made negative so that it can be smoothly collected by the developing roller 7. In the example of FIG. 4, the scattered toner cleaning mode is set by the control device so that the photosensitive drum 2 is recharged, the bias voltage is applied to the scattered toner collecting roller 4, and the polarity of the toner adhering to the photosensitive drum 2 is made uniform. The charging voltage application and the developing roller bias voltage application are controlled in sequence.

  In the embodiment of the present invention, the positive and negative scattered toner adhering to the scattered toner collecting roller 4 is discharged to the photosensitive drum 2 by electrical control, and the scattered toner is collected by the developing roller 7. . For this reason, a toner scraping blade is not required for the scattered toner collecting roller 4, and the configuration is simplified and the cost can be reduced.

  Further, since the mechanical pressing force by the blade is not applied to the scattered toner collecting roller 4, deformation and damage of the scattered toner collecting roller 4 can be prevented. Since the collected scattered toner can be reused for image formation, it is possible to effectively use toner resources. As described above, in the embodiment of the present invention, the scattered toner is collected inside the apparatus, and the discharge of the scattered toner to the outside is reduced, and an environment-friendly image forming apparatus can be obtained.

  The image forming apparatus according to the present invention is intended for a configuration in which image forming units of a charging unit, an exposure unit, a developing unit, and a transfer unit are arranged around an image carrier. This image forming apparatus may be of a monochrome format or a color image forming system. In the case of a color image forming system, for example, it is configured as a tandem image forming apparatus. In this case, a scattered toner collecting roller is provided in each color image forming unit, and the scattered toner is discharged from the scattered toner collecting roller to the photosensitive drum. Then, the scattered toner is scraped off from the photosensitive drum of each color with a cleaning blade. According to such a configuration, in a color image forming apparatus using multiple colors such as three colors or four colors, scattered toner can be collected in each color while avoiding color mixing. Next, a tandem image forming apparatus will be described with reference to a longitudinal sectional view of FIG.

  The tandem color printer (image forming apparatus) exposes four photoconductors as shown in the cross-sectional view of FIG. 5 with four line heads to form four color images at the same time, thereby forming one endless intermediate transfer belt ( Intermediate transfer medium). In this image forming apparatus, exposure apparatuses 101K, 101C, 101M, and 101Y having the same configuration are placed at the exposure positions of four corresponding photosensitive drums (image carriers) 41K, 41C, 41M, and 41Y. Each is arranged. The exposure apparatuses 101K, 101C, 101M, and 101Y are composed of line heads using light emitting elements such as LEDs or organic EL elements as light sources. A scanning optical system that scans with laser light may be used as the exposure apparatus.

  The image forming apparatus is provided with a driving roller 51, a driven roller 52, and a tension roller 53. The intermediate roller is tensioned by the tension roller 53 and is circulated and driven in the direction indicated by the arrow (counterclockwise). A transfer belt (intermediate transfer medium) 50 is provided. Photosensitive members 41K, 41C, 41M, and 41Y having photosensitive layers are arranged on the outer peripheral surface as four image carriers arranged at predetermined intervals with respect to the intermediate transfer belt 50.

  K, C, M, and Y added after the reference sign mean black, cyan, magenta, and yellow, respectively, and indicate that the photoconductors are black, cyan, magenta, and yellow, respectively. The same applies to other members. The photoreceptors 41K, 41C, 41M, and 41Y are rotationally driven in the direction indicated by the arrow (clockwise) in synchronization with the driving of the intermediate transfer belt 50. Around each photoconductor 41 (K, C, M, Y), charging means (corona charger) 42 (K) for uniformly charging the outer peripheral surface of the photoconductor 41 (K, C, M, Y), respectively. , C, M, Y) and the outer peripheral surface uniformly charged by the charging means 42 (K, C, M, Y) are synchronized with the rotation of the photoconductor 41 (K, C, M, Y). An exposure apparatus (line head) 101 (K, C, M, Y) that sequentially scans lines is provided.

  In addition, a developing device 44 (K, C, and Y) that forms a visible image (toner image) by adding toner as a developer to the electrostatic latent image formed by the exposure device 101 (K, C, M, and Y). M, Y) and a primary transfer roller 45 (K, Y) as transfer means for sequentially transferring the toner image developed by the developing device 44 (K, C, M, Y) to the intermediate transfer belt 50 as a primary transfer target. C, M, Y) and a cleaning device 46 (K, C, M, Y) as a cleaning means for removing the toner remaining on the surface of the photoreceptor 41 (K, C, M, Y) after being transferred. ).

  The developing device 44 (K, C, M, Y) uses, for example, a non-magnetic one-component toner as a developer, and the one-component developer is conveyed to the developing roller by a supply roller, for example, and adheres to the surface of the developing roller. The film thickness of the developed developer is regulated by a regulating blade, and the developing roller is brought into contact with or pressed against the photoreceptor 41 (K, C, M, Y), whereby the photoreceptor 41 (K, C, M, Y) The toner image is developed by attaching a developer according to the potential level.

  The black, cyan, magenta, and yellow toner images formed by the four-color single-color toner image forming station are intermediated by the primary transfer bias applied to the primary transfer roller 45 (K, C, M, Y). Primary transfer is sequentially performed on the transfer belt 50, and is sequentially superimposed on the intermediate transfer belt 50 to form a full color. The full-color toner image is secondarily transferred to the recording medium P such as paper by the secondary transfer roller 66, and is fixed on the recording medium P by passing through the fixing roller pair 61 that is a fixing unit. The sheet 62 is discharged onto a sheet discharge tray 68 formed at the upper part of the apparatus.

  In FIG. 5, 63 is a paper feed cassette in which a large number of recording media P are stacked and held, 64 is a pickup roller for feeding recording media P from the paper feed cassette 63 one by one, and 65 is a secondary transfer roller. 66, a pair of gate rollers for defining the supply timing of the recording medium P to the secondary transfer portion 66; a secondary transfer roller 66 as a secondary transfer means for forming a secondary transfer portion with the intermediate transfer belt 50; Is a cleaning blade as a cleaning means for removing the toner remaining on the surface of the intermediate transfer belt 50 after the secondary transfer.

  As described above, the image forming apparatus and the scattered toner collecting method of the present invention have been described based on the principle and the embodiments. However, the present invention is not limited to these embodiments and can be variously modified.

It is a schematic explanatory view showing an embodiment of the present invention. It is a schematic explanatory view showing an embodiment of the present invention. It is a schematic explanatory view showing an embodiment of the present invention. It is a timing chart which shows embodiment of this invention. 1 is a schematic cross-sectional view showing an overall configuration of one embodiment of an image forming apparatus using an electrophotographic process applied to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Photosensitive drum (image carrier), 3 ... Developing device, 4 ... Scattering toner collection roller, 5 ... Power supply of scattering toner collection roller,
6 ... switch of power supply 5, 7 ... developing roller, 8 ... toner supply roller, 9 ... power supply of developing roller, 10 ... charging means (corona charger), 11 ... scattering Toner, 12 ... discharged toner, 13 ... recovered toner

Claims (6)

An image forming apparatus in which a charging unit, an exposure unit, a developing unit, a transfer unit, and a scattering toner collecting roller that is switched and connected to a power source and a ground are disposed around a photosensitive drum. ,
When the scattering toner cleaning mode after image formation is set by the control means, a bias voltage is applied from the power source to the scattering toner collecting roller, and a recharging voltage is intermittently applied to the photosensitive drum by the charging means. The scattered toner collected by the scattered toner collecting roller is discharged to the photosensitive drum, a bias voltage is applied to the developing means, and the scattered toner discharged to the photosensitive drum is discharged by the developing means. An image forming apparatus that collects the image.     The image forming apparatus according to claim 1, wherein the recharging voltage intermittently applied to the photosensitive drum is set to a different voltage between a low voltage and a high voltage. The image forming apparatus according to claim 1, wherein the photosensitive drum and the developing unit are disposed in contact with each other to perform contact development processing. The image forming apparatus according to claim 1, wherein the image forming apparatus is a color image forming apparatus and individually collects scattered toner for each color. An image forming station in which image forming units including a charging unit, an exposure unit, a developing unit, a transfer unit, and a scattered toner collecting roller are arranged around the photosensitive drum is provided. A process of forming an image by passing through;
In the scattered toner cleaning mode after image formation,
A step of applying a bias voltage to the scattered toner collecting roller, a step of applying an intermittent recharging voltage to the photosensitive drum, and a step of discharging the scattered toner collected by the scattered toner collecting roller to the photosensitive drum; And a step of collecting the scattered toner discharged to the photosensitive drum by the developing means. 6. The scattered toner recovery method according to claim 5, wherein the intermittent recharging voltage applied to the photosensitive drum includes a preceding low voltage application period and a subsequent high voltage application period. .

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