JP4604649B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms a toner image on a toner image carrier and transfers the toner image onto a transfer target to form an image. More specifically, the present invention relates to an image forming apparatus including a temporary collection member that temporarily collects transfer residual toner on a toner image carrier and then discharges the toner.

  In an electrophotographic image forming apparatus, a toner image is formed on a toner image carrier by following the steps of charging, exposure, and development. This toner image is transferred onto a transfer medium and further fixed to form an image. Here, some toner remains on the image carrier after the transfer (this is referred to as transfer residual toner). This untransferred toner becomes an obstacle to charging and exposure. Further, the transfer residual toner is unevenly distributed according to the pattern of the toner image before transfer. For this reason, the untransferred toner becomes a noise generation factor for the next formed image.

For this reason, there is a conventional one provided with a cleaner as disclosed in Patent Document 1, for example, at a position after the transfer and before charging. However, when a cleaner is provided, the collected transfer residual toner becomes waste toner. For this reason, it is disadvantageous from the viewpoint of environmental conservation. Therefore, a cleanerless image forming apparatus as in Patent Document 2 has been proposed. In the cleanerless image forming apparatus, the transfer residual toner is collected by the developing device. Here, in order to reliably collect the transfer residual toner in the developing unit, it is necessary to control the charge amount of the transfer residual toner. For this reason, the image forming apparatus disclosed in Patent Document 2 is provided with a temporary collection member (brush roll) that temporarily collects transfer residual toner and returns it to the image carrier at a position before charging after transfer. An appropriate voltage is applied to the temporary recovery member. As a result, the transfer residual toner is returned to the image carrier after the charge amount is adjusted.
JP 2001-255799 A JP 2002-372878 A

  However, the above conventional cleanerless image forming apparatus has the following problems. If the collected toner is discharged as it is just by adjusting the charge, the original toner pattern is inherited as it is. That is, the toner is returned to the image carrier again while being patterned. For this reason, there is a possibility that the vignetting and exposure vignetting may occur in the portion where the toner remains concentrated. This is a serious problem particularly when a patterned image is formed.

  The present invention has been made to solve the problems of the conventional image forming apparatus described above. That is, an object of the present invention is to provide an image forming apparatus capable of appropriately dispersing the transfer residual toner collected on the temporary collection member and returning it to the image carrier.

In order to solve this problem, an image forming apparatus of the present invention includes a toner image carrier that receives electrostatic latent image writing, and a charging charger that charges the surface of the toner image carrier prior to electrostatic latent image writing. And a developing device for developing the electrostatic latent image on the toner image carrier with toner to form a toner image, and transferring the toner image on the toner image carrier onto the transfer member to form an image an apparatus, as well as against the position before transfer after charging the toner image bearing member while rotating around its axis, the charging polarity of the transfer residual toner on the toner image bearing member is reversed from the original charge polarity The conductive temporary recovery member to which the first bias voltage for recovering the reversely charged toner is applied contacts with the toner image carrier on the temporary recovery member at a location other than the contact location , and reverse charging on the temporary recovery member is performed. Book with toner And a distribution member of the second bias voltage to return to the charging polarity of the conductive applied, the temporary collection member is configured to temporarily collect the oppositely charged toner on the toner image bearing member originally by distribution member The discharge surface is discharged onto the toner image carrier, and the contact surface of the scattering member that comes into contact with the temporary collection member is arranged in a flat or columnar shape with columnar or conical projections on the flat base. The scattering member is a member that disperses the toner collected on the temporary collection member when the protrusion comes into contact with the temporary collection member, and on the toner image carrier after passing through the temporary collection member. transfer residual toner is cleanerless construction der shall be collected in the developing device.

In this image forming apparatus, the transfer residual toner on the toner image carrier after transfer reaches the contact point between the toner image carrier and the temporary collection member, and is temporarily collected by the temporary collection member there. The transfer residual toner on the temporary recovery member passes through a contact section between the temporary recovery member and the scattering member as the temporary recovery member rotates. At this time, the temporary recovery member is subjected to a contact pressure that varies depending on the contact of the scattering member with the contact surface as described above . Therefore, the transfer residual toner recovered by the temporary recovery member is moved and dispersed in response to an impact caused by the deformation of the temporary recovery member. The untransferred toner reaches the contact portion between the toner image carrier and the temporary recovery member as the temporary recovery member further rotates. The untransferred toner is then returned to the toner image carrier. Here, since the transfer residual toner is dispersed in the temporary collection member, it is returned to the toner image carrier in a dispersed state. Therefore, the image forming apparatus can appropriately disperse the transfer residual toner collected on the temporary collection member and return it to the image carrier.

Furthermore, in the present invention, it is desirable to provide a vibration mechanism that vibrates the scattering member.
By doing so, the contact surface of the scattering member is vibrated, so that the contact state with the temporary recovery member changes. Therefore, the contact pressure that the temporary recovery member receives from the scattering member is further changed.

Further, in the present invention, it is desirable to have a vibration power source for applying an oscillating voltage to the diffuser Rashi member.
In this way, an oscillating electric field is generated between the scattering member and the temporary recovery member. As a result, the transfer residual toner recovered by the temporary recovery member is electrically vibrated. Therefore, it is more efficiently distributed.

  According to the present invention, there is provided an image forming apparatus capable of appropriately dispersing the transfer residual toner collected on the temporary collection member and returning it to the image carrier.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. The image forming apparatus according to the present embodiment is schematically configured as shown in FIG. The image forming apparatus according to this embodiment is a tandem type full-color image forming apparatus. That is, the image forming apparatus of this embodiment has a transfer belt 6. The transfer belt 6 is installed on rollers 61 and 62, and is rotated counterclockwise in the drawing. Along the transfer belt 6, image forming portions 1K, 1C, 1M, and 1Y of black, cyan, magenta, and yellow are arranged. As a result, the toner images of the respective colors are superimposed on the transfer belt 6. A secondary transfer roller 8 is provided opposite to the roller 61. As a result, the superimposed toner image on the transfer belt 6 is transferred onto the paper 9. A cleaning blade 10 for removing residual toner on the transfer belt 6 is provided.

  Each of the image forming units 1K, 1C, 1M, and 1Y is structurally the same. That is, each of the image forming units 1K, 1C, 1M, and 1Y has a photosensitive drum 2. A charging charger 3, a developing device 4, and a toner charging device 5 are provided around the charging device. The developing device 4 uses negative toner. A primary transfer roller 7 is provided at a position facing the photosensitive drum 2 with the transfer belt 6 interposed therebetween. The rotation direction of the photosensitive drum 2 is the forward direction with respect to the rotation of the transfer belt 6, that is, clockwise in the drawing. Therefore, the toner charging device 5 is positioned downstream of the primary transfer roller 7 and upstream of the charging charger 3 with respect to the rotation direction of the photosensitive drum 2. An exposure position E is provided downstream of the charging charger 3 and upstream of the developing device 4.

  The toner charging device 5 will be further described with reference to FIG. The toner charging device 5 includes a brush roller 51, an electrode 52, and a case 53. The brush roller 51 is formed by implanting a large number of conductive needle-like shapes in the axial center. The brush roller 51 is flexible and has a cylindrical outer shape as a whole. The brush roller 51 is in contact with a position on the photosensitive drum 2 downstream of the primary transfer roller 7 and upstream of the charging charger 3. The brush roller 51 rotates around its axis during operation. The rotation direction can be set to either the forward direction or the counter direction with respect to the rotation of the photosensitive drum 2. In the following description, it is assumed that the counter is set to rotate in the counter direction unless otherwise specified. A bias voltage V <b> 1 is applied to the brush roller 51.

  The electrode 52 is disposed in the case 53 together with the brush roller 51. Here, the electrode 52 is a conductive member such as a metal, and the surface facing the brush roller 51 is uneven. In this embodiment, as shown in FIG. 3, a cylindrical protrusion 52b is provided all over one surface of a square flat base 52a. The base 52a is arranged with its longitudinal direction parallel to the axial direction of the photosensitive drum 2, and has a length at least equal to the width of the image forming area. Each of the protrusions 52b has a columnar shape with the same size, and is fixed so as to be perpendicular to one surface of the base 52a. For example, protrusions 52b having a diameter of 1 mm and a length of 2 mm are arranged on one surface of a base 52a of 300 mm × 20 mm at intervals of 2 mm in the vertical and horizontal directions. A bias voltage V <b> 2 is applied to the electrode 52. The shape of the protrusion 52b is not limited to a cylinder, but may be a prism, a cone, a pyramid, or the like. Furthermore, the arrangement of the protrusions 52b is not limited to this and is arbitrary. For example, any arrangement such as an orthogonal arrangement or an oblique arrangement may be used.

  A setting example of the bias voltage V1 and the bias voltage V2 will be described. This bias setting requires the following. First, it is required that the transfer residual toner on the photosensitive drum 2, in particular, one whose charging polarity is reversed (hereinafter referred to as “reversely charged toner”) can be collected by the brush roller 51. This is required for the bias voltage V1. Further, it is required to return the charging polarity of the reversely charged toner collected by the brush roller 51 to the original charging polarity. This is required for the bias voltage V2. Further, it is required that the toner on the brush roller 51 does not move to the electrode 52. This is obtained with respect to the relationship between the bias voltage V1 and the bias voltage V2. Further, it is required that the toner whose charging polarity is adjusted on the brush roller 51 is discharged onto the photosensitive drum 2. This is required for the bias voltage V1.

Here, the bias setting according to the following conditions was adopted. First, the bias voltage V1 of the brush roller 51 is a superposition of AC and DC and is as follows.
DC component Vdc = −100 V (vs voltage of photosensitive drum 2)
AC component Vpp = 300V
Frequency f = 100Hz
Waveform: Rectangular wave (duty 50%)
That is, V1 = Vdc + Vpp. On the other hand, the bias voltage V2 of the electrode 52 is DC, and is −500 V (vs. the voltage of the photosensitive drum 2).

  Next, the operation of the image forming apparatus of this embodiment will be described. In the image forming apparatus of this embodiment, toner images of respective colors are created on the respective photosensitive drums 2 by the respective image forming units 1K, 1C, 1M, and 1Y. These toner images are transferred onto the transfer belt 6 by the primary transfer rollers 7 of the image forming units 1K, 1C, 1M, and 1Y. As a result, four color toner images are superimposed on the transfer belt 6. The superimposed toner image thus formed is transferred onto the paper 9 by the secondary transfer roller 8. The sheet 9 that has received the transfer of the superimposed toner image is subsequently fixed. As a result, a color image is formed on the sheet 9.

  In each of the image forming units 1K, 1C, 1M, and 1Y, a toner image is created as follows. First, the charging layer 3 charges the photosensitive layer on the surface of the photosensitive drum 2 to a predetermined potential. An electrostatic latent image is written at the exposure position E on the photosensitive layer charged to a predetermined potential. The developing unit 4 develops the electrostatic latent image. As a result, a toner image is formed. The formed toner image is transferred onto the transfer belt 6 by the primary transfer roller 7.

  Here, a certain amount of toner remains on the surface of the photosensitive drum 2 even after passing the transfer position by the primary transfer roller 7. The transfer residual toner is subjected to the following processing by the toner charging device 5. The transfer residual toner reaches the contact position between the photosensitive drum 2 and the brush roller 51 by the rotation of the photosensitive drum 2. Then, the transfer residual toner is collected by the brush roller 51. Here, the bias voltage V1 between the photosensitive drum 2 and the brush roller 51 is set as described above. As a result, an electric field is applied to this position in a direction that attracts the reversely charged toner on the photosensitive drum 2 to the brush roller 51. For this reason, it is mainly reversely charged toner among the residual transfer toner that is collected by the brush roller 51.

  The transfer residual toner collected by the brush roller 51 reaches the contact portion between the brush roller 51 and the electrode 52 by the rotation of the brush roller 51. Therefore, the charging state is adjusted by the bias voltage V2 of the electrode 52. Specifically, the charging polarity of the reversely charged toner is returned to the original charging polarity. In this way, most of the reversely charged toner is charged and adjusted by the rotation of the brush roller 51 until it passes through the contact portion between the brush roller 51 and the electrode 52. Then, the toner on the brush roller 51 whose charge has been adjusted reaches the contact position between the photosensitive drum 2 and the brush roller 51 again by the rotation of the brush roller 51. Then, the toner is discharged from the brush roller 51 onto the photosensitive drum 2. This is because the electric field as described above is applied to this position. For this reason, the charge-adjusted toner is attracted from the brush roller 51 onto the photosensitive drum 2.

  In this way, the toner charging device 5 performs charging adjustment on the transfer residual toner on the photosensitive drum 2 at a position after the transfer and before the charging. That is, there is almost no reversely charged toner on the photosensitive drum 2 after passing through the toner charging device 5. For this reason, the transfer residual toner on the photosensitive drum 2 is in the same charged state as when it is subjected to development by the developing device 4. In this situation, the untransferred toner on the photosensitive drum 2 goes to the charging position by the charging charger 3 and thereafter. Therefore, the transfer residual toner does not interfere with charging and exposure. Further, at the time of development, it is collected by the developing device 4 particularly in the white portion. This is because charging is adjusted. For this reason, the untransferred toner does not cause image noise.

  From the above, the collection of the transfer residual toner by the brush roller 51 is temporary. Therefore, toner does not accumulate on the brush roller 51. Therefore, the toner charging device 5 is not a so-called cleaner. That is, each of the image forming units 1K, 1C, 1M, and 1Y of the image forming apparatus of the present embodiment employs a cleanerless process.

  Here, the image forming apparatus of this embodiment has a particular advantage depending on the shape of the electrode 52. As described above, the electrode 52 is provided with irregularities on the surface facing the brush roller 51. For this reason, compared with the case where the contact surface with respect to the brush roller 51 is a smooth surface, there are the following advantages.

  That is, the bristles of the brush roller 51 are bent and stretched by coming into contact with the protrusions 52 b of the electrode 52. For this reason, the toner collected and adhered to the brush roller 51 is scattered. In particular, in the case of a patterned toner image, there is a portion where the toner remains concentrated. The toner in such a part is particularly easily moved. Therefore, the original toner image pattern is eliminated by passing through the toner charging device 5. That is, a good scattering is made.

  Further, the electrode contacting the brush roller 51 in the case 53 may be as shown in FIG. 4 or FIG. FIG. 4 shows an electrode 54 which is formed in a corrugated plate shape as a whole. FIG. 5 shows an electrode 55 that is formed in a jagged shape as a whole. In any case, the direction of the wave is not limited to that shown in the figure, and may be any of vertical, horizontal, and diagonal directions. Further, the direction of the wave may change in the plate surface. Even when the electrode having such a shape is used, the brush tip of the brush roller 51 is bent and stretched, so that good scattering can be achieved.

  Further, a drive device may be attached to these electrodes 52, 54, and 55 to vibrate. FIG. 6 shows an example of a vibration device. A gear 2 a for rotationally driving is originally attached to one end of the photosensitive drum 2. Therefore, this rotational motion is converted into a reciprocating motion of the electrodes 52, 54, and 55 using a cam 56 with a gear. In the illustrated example, a spring 57 is further provided to smooth the vibration of the electrodes 52, 54 and 55. As a result, the electrodes 52, 54, and 55 are reciprocated in parallel with the axial direction of the photosensitive drum 2. Accordingly, the scattering effect is further increased. In addition to the driving device for the photosensitive drum 2, a unique driving device for vibrating the electrodes 52, 54, and 55 may be provided.

  The same effect can be obtained by superimposing an oscillating electric field such as an alternating current on the bias voltage V2 applied to the electrodes 52, 54, and 55. This is because vibration force acts on the toner adhering to the brush roller 51. The oscillating electric field to be superimposed is, for example, a rectangular wave having a frequency f = 100 Hz and Vpp = 300V. However, in the image forming apparatus of this embodiment, since the vibration voltage is also applied to the brush roller 51, the electrode itself may vibrate due to the mutual electric repulsive force.

  As described in detail above, in each of the image forming units 1K, 1C, 1M, and 1Y of the image forming apparatus according to the present embodiment, the charging residual toner on the photosensitive drum 2 is charged by the toner charging device 5 and the charging charger 3 is adjusted. A cleanerless process is used to send to the following. The toner charging device 5 is provided with electrodes 52, 54, and 55 that come into contact with the brush roller 51 on the surface provided with a plurality of irregularities. As a result, the hair tips of the brush roller 51 are bent and stretched, and the adhering toner is satisfactorily scattered. In this way, an image forming apparatus that can appropriately disperse the transfer residual toner collected on the brush roller 51 and return it to the photosensitive drum 2 is realized. In addition, the charge of the transfer residual toner can be appropriately adjusted.

  Further, there is a form in which the electrodes 52, 54, and 55 are vibrated using a driving force or an oscillating electric field applied to the photosensitive drum 2. According to this, a better scattering effect can be obtained.

  In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, in this embodiment, as shown in FIG. 1, a tandem full-color image forming apparatus is targeted. However, the present invention is not limited to this, and can also be applied to a monochrome machine. The target image forming apparatus may be a copying machine, a printer, a fax machine, or a multifunction machine. In this embodiment, the brush roller is used as the temporary recovery member. However, the present invention is not limited to this, and a sponge roller or a rubber roller may be used as long as it is conductive.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. 1 is a configuration diagram illustrating a structure of an image forming unit in an image forming apparatus according to an embodiment. It is explanatory drawing which shows the example of the shape of an electrode. It is explanatory drawing which shows another example of the shape of an electrode. It is explanatory drawing which shows another example of the shape of an electrode. It is a schematic block diagram which shows the structure for vibrating an electrode.

Explanation of symbols

2 Photosensitive drum (toner image carrier)
5 Toner Charging Device 51 Brush Roller (Temporary Recovery Member)
52, 54, 55 Electrode (scattering member)
56 Cam (vibration mechanism)
V2 Bias voltage (vibration power supply)

Claims (3)

A toner image carrier that receives electrostatic latent image writing, a charger that charges the surface of the toner image carrier prior to electrostatic latent image writing, and the electrostatic latent image on the toner image carrier is developed with toner. A developing device for forming a toner image, and transferring the toner image on the toner image carrier onto a transfer target to form an image.
While contact to the position before the post-transfer charging in the toner image bearing member while rotating around its axis, the reverse charged toner charge polarity is reversed from the original charge polarity of the transfer residual toner on the toner image carrier A conductive temporary recovery member to which a first bias voltage for recovering is applied ;
Conduction to which a second bias voltage is applied to make contact with the toner image carrier other than the contact position with the toner image carrier on the temporary recovery member and return the toner recovered on the temporary recovery member to the original charging polarity. Having a sex dispersal member,
The temporary collection member temporarily collects the reversely charged toner on the toner image carrier, returns to the original charged polarity by the scattering member, and discharges it onto the toner image carrier.
Wherein said contact surface in contact with the temporary collection member scraping member, Ri surface der arranged in tabular orthogonal sequence or oblique mating column columnar or conical projections on the base portion,
The scattering member disperses the toner collected on the temporary collection member by the protrusion coming into contact with the temporary collection member,
An image forming apparatus comprising a cleanerless structure der Rukoto transfer residual toner on the toner image bearing member is collected in the developing device after passing through the temporary collection member. The image forming apparatus according to claim 1,
An image forming apparatus comprising a vibration mechanism that vibrates the scattering member. The image forming apparatus according to claim 1 ,
An image forming apparatus comprising: a vibration source for applying an oscillating voltage before Symbol distribution member.

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