JP4470579B2 - Intermediate transfer apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an intermediate transfer device and an image forming apparatus.

  In an image forming apparatus that primarily transfers a toner image onto an intermediate transfer belt and then secondary transfer this toner image onto a recording medium such as paper, the toner remaining on the toner carrying surface of the intermediate transfer belt (so-called transfer residual toner) is removed. There is a need to.

  For example, Patent Document 1 discloses a cleaning device that can remove residual toner after transfer by applying both (+) and (−) polarities to a cleaning brush that contacts an intermediate transfer member. An image forming apparatus having the same is described.

However, this configuration requires two power supplies corresponding to each of the two cleaning brushes in order to remove the toner, which may increase costs and increase the size of the apparatus.
Japanese Patent Laid-Open No. 2003-66735

  SUMMARY OF THE INVENTION In consideration of the above-described facts, an object of the present invention is to provide an intermediate transfer device that can effectively remove transfer residual toner from an intermediate transfer belt with a low-cost and compact configuration, and an image forming apparatus including such an intermediate transfer device. And

In the invention according to claim 1, formed in an endless shape, and the intermediate transcription belt cyclable supported by Rutotomoni, surface is the toner carrying surface for carrying the toner by a plurality of belt supporting means, said belt support Bias applying means for applying a bias voltage to the toner on the toner carrying surface of the intermediate transfer belt disposed opposite to at least one of the means via the intermediate transfer belt, and power supply means for supplying the bias voltage to the bias applying means And a rotary cleaning member that is disposed in the vicinity of the bias applying unit and downstream of the bias applying unit in the circulation direction of the intermediate transfer belt, and is rotatable along the circulation direction of the intermediate transfer belt. the rotary cleaning member is directly grounded, among a plurality of said belt supporting means, said biasing means and the opposite distribution And a belt supporting means is characterized by being grounded through a voltage maintaining means.

In this intermediate transfer device, a potential difference is generated between the bias applying means and the opposite belt supporting means by the bias voltage supplied to the bias applying means by the power supply means (the belt supporting means has a lower potential than the bias applying means). ) Further, since the rotary cleaning member arranged near the bias applying unit and downstream of the bias applying unit in the circulation direction of the intermediate transfer belt is grounded, it is interposed between the belt supporting unit and the rotary cleaning member. A potential difference also occurs. Moreover, among the plurality of belt support means, the belt support means arranged to face the bias applying means is grounded via the voltage maintaining means, so that the potential is stabilized. Therefore, the toner on the toner carrying surface of the intermediate transfer belt is charged with the same polarity as the bias applying means, and thereafter is adsorbed by the rotary cleaning member and removed from the toner carrying surface of the intermediate transfer belt. The toner can be removed from the intermediate transfer belt and cleaned by only a single power supply means, and a plurality of conventional power supplies are not required, so that the cost is reduced and the intermediate transfer device can be downsized.

In addition, since the rotary cleaning member removes toner while rotating along the circulation direction of the intermediate transfer belt , even if the intermediate transfer belt has elasticity, an excessive load is not applied.

  According to a second aspect of the present invention, in the first aspect of the present invention, the bias applying unit is formed in a sheet shape and contacts the intermediate transfer belt along the same direction as the circulation direction of the intermediate transfer belt. The sheet-like bias applying means is arranged in the above.

Accordingly, the sheet-like bias applying means contacts along the circulation direction of the intermediate transfer belt. For this reason, even the intermediate transfer belt having elasticity can reduce the load against the circulation.

  According to a third aspect of the invention, in the first aspect of the invention, the bias applying means is formed in a brush shape so as to contact the intermediate transfer belt along the same direction as the circulation direction of the intermediate transfer belt. And a brush-like bias applying means arranged in the above.

Therefore, the brush-like bias applying means contacts along the circulation direction of the intermediate transfer belt. For this reason, even the intermediate transfer belt having elasticity can reduce the load against the circulation.

  In addition, since a large number of flocks constituting the brush come into contact with the toner carrying surface of the intermediate transfer belt, the contact property is improved.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the cleaning member presses the intermediate transfer belt with a deflection amount smaller than the thickness of the intermediate transfer belt. It arrange | positions so that it may do.

In this way, by bending the intermediate transfer belt and bringing the cleaning surface into contact with the toner carrying surface, a wider contact area can be obtained and cleaning can be performed effectively. In addition, since the amount of bending is less than the thickness of the intermediate transfer device, and the intermediate transfer belt is not excessively bent, the degree of expansion and contraction can be reduced even with an intermediate transfer belt having elasticity. . In addition, it is possible to prevent image deterioration caused by bending of the intermediate transfer belt.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the rotary cleaning member is a metal cleaning roll made of metal, and the toner scraping scrapes off the toner in contact with the surface of the metal cleaning roll. It has the member .
In this way, by rotating the metal cleaning roll while being in contact with the toner carrying surface of the intermediate transfer belt , it is not necessary to strongly press even the intermediate transfer belt having elasticity, so that the influence on the intermediate transfer belt is reduced. it can. In addition, since the toner scraping member comes into contact with the surface of the metal cleaning roll and scrapes off the toner, the surface of the metal cleaning roll is always refreshed, and the toner removing ability can be maintained high.

  According to a sixth aspect of the present invention, in the first aspect of the present invention, the intermediate transfer belt is disposed downstream in the intermediate transfer belt circulation direction with respect to the belt supporting unit in which the bias applying unit is disposed oppositely. A second belt supporting means for supporting the transfer belt from the side opposite to the toner carrying surface; a second bias applied to the toner on the toner carrying surface of the intermediate transfer belt arranged opposite to the second belt supporting means and the intermediate transfer belt; It has 2nd bias application means which applies a voltage, and 2nd power supply means which supplies said 2nd bias voltage to said 2nd bias application means, It is characterized by the above-mentioned.

Therefore, on the downstream side of the bias applying means, the second bias voltage supplied to the second bias applying means by the second power supply means is also between the second bias applying means and the opposing second belt supporting means. A potential difference occurs (the second belt support means has a lower potential than the second bias application means). Accordingly, the toner on the intermediate transfer belt that could not be removed by the upstream rotary cleaning member can be charged by the second bias applying unit.

  According to a seventh aspect of the invention, in the sixth aspect of the invention, the second bias applying means is formed in a brush shape and contacts the intermediate transfer belt along the same direction as the circulation direction of the intermediate transfer belt. It is the 2nd brush-like bias application means arrange | positioned so that it may be characterized by the above-mentioned.

Therefore, the second brush-like bias applying means contacts along the circulation direction of the intermediate transfer belt. For this reason, even the intermediate transfer belt having elasticity can reduce the load against the circulation.

  In addition, since a large number of flocks constituting the brush come into contact with the toner carrying surface of the intermediate transfer belt, the contact property is improved.

  The invention according to claim 8 is the rotary metal roll according to claim 6, wherein the second bias applying means is made of metal and is rotatable along the circulation direction of the intermediate transfer belt, It is characterized by being.

In this way, the rotating metal roll is rotated while being in contact with the toner carrying surface of the intermediate transfer belt , so that even if the intermediate transfer belt has elasticity, it is not necessary to press strongly, so the influence on the intermediate transfer belt is affected. Can be small.

  According to a ninth aspect of the present invention, in the invention according to any one of the sixth to eighth aspects, the second belt support means is electrically connected to a belt support means in which the bias applying means is disposed oppositely. The rotary cleaning member is directly grounded.

  Therefore, an electrical path is formed which is grounded from the second bias applying means through the second belt supporting means and the belt supporting means voltage maintaining means. A bias is supplied to the voltage maintaining means connected to the belt supporting means by the second bias applying means, and the potential of the belt supporting means can be stabilized, so that the degree of freedom in setting the bias voltage in the bias applying means is increased. For this reason, for example, the sticking force to the intermediate transfer belt and the charge amount of the toner on the toner carrying surface can be set more appropriately.

  According to a tenth aspect of the present invention, in the invention according to any one of the sixth to eighth aspects, the second belt support means is electrically connected to a belt support means in which the bias applying means is disposed oppositely. Insulated and directly grounded.

  Therefore, since the second belt supporting unit and the second bias applying unit are independent circuits, the bias voltage of the second bias applying unit can be set low.

  According to an eleventh aspect of the present invention, in the tenth aspect, the second bias voltage has a polarity opposite to that of the bias voltage.

  Thereby, the residual toner can be removed again by the second bias applying means.

  The invention according to claim 12 is the invention according to claim 9 or 10, characterized in that the second bias voltage has the same polarity as the bias voltage.

  Accordingly, the residual toner on the intermediate transfer belt can be removed using, for example, an image carrier that contacts the intermediate transfer belt.

  In any of the eleventh and twelfth aspects, the toner can be more reliably removed from the toner carrying surface of the intermediate transfer belt.

  According to a thirteenth aspect of the present invention, in the invention according to any one of the sixth to twelfth aspects, the belt supporting means in which the bias applying means is arranged oppositely and the second belt supporting means are The intermediate transfer belt is arranged at an interval that forms a short side in a state where the intermediate transfer belt is supported.

Thereby, the intermediate transfer device can be reduced in size. Further, even an intermediate transfer belt having elasticity can effectively remove toner from the toner carrying surface.

  According to a fourteenth aspect of the present invention, there is provided an intermediate transfer device according to any one of the first to thirteenth aspects, a primary transfer portion that primarily transfers a toner image to the intermediate transfer device, and the intermediate transfer device. And a secondary transfer portion for secondary transfer of the toner image to the recording medium.

  In this image forming apparatus, the image is primarily transferred from the primary transfer unit to the intermediate transfer device, and this image is secondarily transferred to the recording medium by the secondary transfer unit, thereby forming a desired image on the recording medium. It has the intermediate transfer device according to any one of claims 1 to 13, and does not require a plurality of conventional power supplies for removing toner from the toner carrying surface of the intermediate transfer belt. Therefore, the cost is reduced and the image forming apparatus can be downsized.

  Since the present invention has the above-described configuration, the transfer residual toner can be effectively removed from the intermediate transfer belt with a low-cost and small-sized configuration.

  Hereinafter, a color printer to which a known electrophotographic process is applied will be described with reference to the drawings as an example to which the intermediate transfer apparatus and the image forming apparatus according to the present invention are applied. The image forming apparatus to which the present invention is applied is not limited to a color printer described below, and may be an image forming apparatus such as a copying machine, a facsimile machine, or a multifunction machine.

  Embodiments of the present invention will be described with reference to the drawings. In the following description, detailed descriptions of those not directly related to the essence of the present invention are omitted.

  FIG. 1 shows an outline of an intermediate transfer device 62 (details will be described later) according to an embodiment of the present invention and a color printer 10 in which the intermediate transfer device 62 is mounted on the color printer main body 12.

  The color printer 10 includes a color printer main body 12, and an open / close cover 16 that is rotatable about a rotation fulcrum 14 is provided on the upper portion of the color printer main body 12. In addition, a paper feeding unit 18 is disposed below the color printer main body 12.

  The paper feed unit 18 has a paper feed cassette 22 in which the recording paper P is stored. A feed roll 24 that feeds recording paper P from the paper feed cassette 22 and a retard roll 26 that scoops the supplied recording paper P one by one are arranged in the upper part near the rear end of the paper feed cassette 22.

  The conveyance path 28 is a path for the recording paper P from the feed roll 24 to the discharge port 30. The conveyance path 28 is in the vicinity of the back side (right side in FIG. 1) of the color printer main body 12 and is formed substantially vertically from the paper feeding unit 18 to the fixing device 90. A secondary transfer roll 80 and a secondary transfer backup roll 72 are arranged on the upstream side of the fixing device 90 in the conveyance path 28, and a resist roll 32 is arranged on the upstream side of the secondary transfer roll 80 and the secondary transfer backup roll 72. Has been. In addition, a discharge roll 34 is disposed in the vicinity of the discharge port 30 of the conveyance path 28.

  Accordingly, the recording paper P sent out from the paper feeding cassette 22 of the paper feeding unit 18 by the feed roll 24 is turned by the retard roll 26 and only the uppermost recording paper P is guided to the transport path 28, and is fed by the registration roll 32. At this time, the toner image is transferred between the secondary transfer roll 80 and the intermediate transfer belt 64 (secondary transfer backup roll 72) at a timing, and the transferred toner image is transferred by the fixing device 90. The toner is fixed and discharged from a discharge port 30 to a discharge portion 36 provided on the upper part of the opening / closing cover 16 by a discharge roll 34. The discharge portion 36 has a low discharge port portion and is inclined so as to gradually increase toward the front direction (left direction in FIG. 1).

  The color printer main body 12 is provided with a rotary developing device 38 at a substantially central portion. The rotary developing device 38 includes developing units 42a to 42d that respectively form toner images of four colors of yellow, yellow, magenta, cyan, and black in the developing unit main body 40. It rotates counterclockwise (counterclockwise in FIG. 1) about the rotary developing device center 44. Each of the developing units 42a to 42d has developing rolls 46a to 46d, and is pressed in the normal direction of the developing unit main body 40 by elastic bodies 48a to 48d such as coil springs.

  The rotary developing device 38 is arranged so that the photosensitive drum 50 rotating about the rotation support shaft 49 is in contact with each other, and the developing rolls 46a to 46d are not in contact with the photosensitive drum 50, respectively. A part of the outer periphery of the developing device protrudes from the outer periphery of the developing device main body 40 in the radial direction by about 2 mm. Further, a tracking roll (not shown) having a diameter slightly larger than the diameter of the developing rolls 46a to 46d is provided at both ends of each of the developing rolls 46a to 46d so as to rotate coaxially with the developing rolls 46a to 46d. Yes. In other words, the developing devices 42 a to 42 d are arranged on the outer periphery of the developing device main body 40 at intervals of 90 ° with the rotary developing device center 44 as the center, and the tracking rolls of the developing rollers 46 a to 46 d are disposed at both ends of the photosensitive drum 50. The latent image on the photosensitive drum 50 is developed with toner of each color while abutting against a provided flange (not shown) and forming a predetermined gap between the developing rolls 46a to 46d and the photosensitive drum 50. To do.

  A charging roll 52 is provided below the photosensitive drum 50, and a charging bias is applied to the charging roll 52 to uniformly charge the photosensitive drum 50. A photosensitive drum cleaner 54 is provided so as to hang from the rotation spindle 49 of the photosensitive drum 50, and the photosensitive drum 50 and the photosensitive drum cleaner 54 are integrated. The photoreceptor drum cleaner 54 includes a cleaning blade 56 that scrapes waste toner remaining on the photoreceptor drum 50 after primary transfer, and a toner collection case 58 that collects waste toner scraped by the cleaning blade 56.

  Note that a rib or the like is formed on the back side (right side in FIG. 1) of the toner recovery case 58, and the recording paper P is curved to form a part of the transport path 28.

  On the lower back side of the rotary developing device 38, an exposure device 60 for writing a latent image on the photosensitive drum 50 charged by the charging roll 52 with a light beam such as a laser beam is disposed. Further, the toner image visualized by the rotary developing device 38 is primarily transferred above the rotary developing device 38 at the primary transfer position, and the secondary transfer position (the nip between the secondary transfer roll 80 and the secondary transfer backup roll 72) is transferred. An intermediate transfer device 62 is provided.

  The intermediate transfer device 62 includes an intermediate transfer belt 64, a primary transfer roll 66, a wrap-in roll 68, a wrap-out roll 70, a secondary transfer backup roll 72, a cleaning backup roll 74, a brush backup roll 76, and the like.

In the present embodiment, the intermediate transfer belt 64 has elasticity and is stretched substantially flat so as to have a long side and a short side above the rotary developing device 38. The long sides on the upper and lower sides of the intermediate transfer belt 64 are stretched so as to be substantially parallel to the discharge portion 36 provided on the upper portion of the color printer main body 12.

  The intermediate transfer belt 64 is positioned between a wrap-in roll 68 disposed upstream of the primary transfer roll 66 below the long side of the intermediate transfer belt 64 and a wrap-out roll 70 disposed downstream of the primary transfer roll 66. Thus, the photosensitive drum 50 has a primary transfer portion (photosensitive drum wrap region) that contacts the photosensitive drum 50 in a wrap shape, is wound around the photosensitive drum 50 by a predetermined range, and is driven by the rotation of the photosensitive drum 50. As described above, the toner image on the photosensitive drum 50 is superimposed on the toner transfer surface 64H (outer surface) in the order of yellow, magenta, cyan, and black by the primary transfer roll 66 on the intermediate transfer belt 64. The transferred and primary transferred toner image is conveyed toward the secondary transfer roll 80. Note that the wrap-in roll 68 and the wrap-out roll 70 are separated from the photosensitive drum 50.

  As described above, the intermediate transfer belt 64 is stretched by five rolls of the wrap-in roll 68, the wrap-out roll 70, the secondary transfer backup roll 72, the cleaning backup roll 74, and the brush backup roll 76, and the primary transfer roll 66, the toner image on the photosensitive drum 50 is transferred. These rolls are formed in a cylindrical shape or a columnar shape so as to support the intermediate transfer belt 64 in a circulatory manner.

As described above, the interval between the cleaning backup roll 74 and the brush backup roll 76 is arranged such that the intermediate transfer belt 64 has a short side when the intermediate transfer belt 64 is stretched substantially flat so as to have a long side and a short side. ing. For this reason, the intermediate transfer device 62 is reduced in size as compared with the configuration in which the interval between the cleaning backup roll 74 and the brush backup roll 76 is wide. Moreover, the reliably maintain the contact state at the time of contact with the cleaning roller 83 as described later, be an intermediate transfer belt 64 having elasticity as in this embodiment, from the toner carrier surface 64H, reliably The toner can be removed.

  Further, a flat portion (short side) is formed on the back side (right side surface in FIG. 1) of the intermediate transfer belt 64 by a wrap-out roll 70 and a secondary transfer backup roll 72, and this flat portion is the secondary transfer portion. It faces the transport unit 28.

  In the secondary transfer portion, the wrap-out roll 70 is disposed so that the intermediate transfer belt 64 and the conveyance path 28 are at an angle of about 12 °.

  The cleaning backup roll 74 assists the cleaning roll 83 described later by suction and removal of waste toner remaining on the intermediate transfer belt 64 after the secondary transfer, and the brush backup roll 76 is applied to the intermediate transfer belt 64 after the secondary transfer. It assists the brush roll 86 to scrape the remaining waste toner.

  A reflective photosensor 78 is provided above the long side of the intermediate transfer belt 64 by being fixed to the back surface (inside) of the open / close cover 16. The reflective photosensor 78 reads a toner patch formed on the intermediate transfer belt 64, detects the position of the intermediate transfer belt 64 in the rotational direction, and detects the density of the toner image.

  A secondary transfer roll 80 is opposed to the secondary transfer backup roll 72 of the intermediate transfer device 62 with the conveyance path 28 interposed therebetween. That is, the secondary transfer position in the secondary transfer portion is between the secondary transfer roll 80 and the secondary transfer backup roll 72, and the secondary transfer roll 80 is intermediate with the assistance of the secondary transfer backup roll 72. The toner image primarily transferred to the transfer belt 64 is secondarily transferred to the recording paper P at the secondary transfer position. Here, the secondary transfer roll 80 is rotated while the intermediate transfer belt 64 rotates three times, that is, while the toner images of three colors of yellow, magenta, and cyan are primarily transferred and conveyed on the intermediate transfer belt. It is separated from the intermediate transfer belt 64, and comes into contact with the intermediate transfer belt 64 when a black toner image is transferred.

  In addition, a predetermined potential difference is generated between the secondary transfer roll 80 and the secondary transfer backup roll 72, and when the secondary transfer roll 80 is set to a high voltage, the secondary transfer backup roll 72 is connected to the ground (GND).

  An intermediate transfer belt cleaner 82 is provided at the end of the intermediate transfer belt 64 on the side opposite to the photosensitive drum 50. The intermediate transfer belt cleaner 82 includes a conductive sheet 81, a cleaning roll 83, a brush roll 86, a toner collection case 88, and a rotation support shaft 89, and swings about the rotation support shaft 89. By this swing, the intermediate transfer belt cleaner 82 is separated from the contact position (see FIG. 2) where the conductive sheet 81, the cleaning roll 83, and the brush roll 86 are in contact with the intermediate transfer belt 64, and away from the intermediate transfer belt 64. Move between positions (see FIG. 3).

  The conductive sheet 81 is an example of a bias applying unit in the present invention, and is configured by a sheet having elasticity and conductivity as shown in FIG. One end of the conductive sheet 81 is fixed to the casing of the intermediate transfer device 62, and the other end is wound around the cleaning backup roll 74 elastically at a predetermined contact pressure along the circulation direction of the intermediate transfer belt 64. This portion is in contact with the toner carrying surface 64H of the intermediate transfer belt 64. This contact pressure is set so that the conductive sheet 81 can be reliably brought into contact with the intermediate transfer belt 64 and does not cause excessive resistance (load) to the circulation of the intermediate transfer belt 64.

  As shown in FIG. 5, a bias power supply 85 is connected to the conductive sheet 81, and a predetermined bias voltage (for example, 1700 V, see FIG. 7) is applied. When the conductive sheet 81 comes into contact with the toner carrying surface 64H of the intermediate transfer belt 64, the toner on the toner carrying surface 64H is charged and the amount of charge is controlled.

  The cleaning roll 83 is made of metal and is formed in a columnar shape or a cylindrical shape, and is rotated at a peripheral speed substantially equal to the circulation speed of the intermediate transfer belt 64 by a rotation driving source (not shown). Further, the cleaning roll 83 is grounded (grounded) by a ground wire 87, and the potential is maintained at 0V. Accordingly, the outer peripheral surface (cleaning surface 83C) of the cleaning roll 83 electrostatically adsorbs the toner whose charge is controlled on the toner carrying surface 64H of the intermediate transfer belt 64 and removes (cleans) the toner from the toner carrying surface 64H.

  In the present embodiment, the cleaning backup roll 74 is grounded via the voltage maintaining element 98. The voltage maintaining element 98 accumulates charges inside until the potential of the cleaning backup roll 74 reaches a predetermined value and contributes to an increase in the potential of the cleaning backup roll 74, but releases the charge when the cleaning backup roll 74 reaches a predetermined potential. . Thereby, the cleaning backup roll 74 is stably maintained at a predetermined potential (for example, 700 V). Examples of the voltage maintaining element 98 having such an action include a varistor and a Zener diode.

  In this embodiment, as shown in FIG. 4, the intermediate transfer belt 64 when the cleaning roller 83 pushes in the intermediate transfer belt 64 with the intermediate transfer belt cleaner 82 swinging to the contact position. The amount of bending B1 is shorter than the thickness T1 of the intermediate transfer belt 64 itself. Since the intermediate transfer belt 64 is not excessively bent, the degree of expansion / contraction of the intermediate transfer belt 64 can be further reduced.

  As shown in FIG. 6, a scraper 84 is disposed corresponding to the cleaning roll 83. The scraper 84 is formed in a thin plate shape with a metal such as stainless steel, for example, and is disposed so that the cleaning portion 84 </ b> C at the tip faces the outer peripheral surface in a direction opposite to the rotation direction of the cleaning roll 83. The scraper 84 scrapes off the waste toner adhering to the outer peripheral surface of the cleaning roll 83 and cleans it.

The brush roll 86 further scrapes off the waste toner remaining after cleaning by the cleaning roll 83. The toner collection case 88 collects the waste toner cleaned by the cleaning roll 83 and the brush roll 86.

  The brush roll 86 is made of a brush such as acrylic that has been subjected to a conductive treatment. While the intermediate transfer belt 64 conveys the toner image, the cleaning roll 83 and the brush roll 86 are separated from the intermediate transfer belt 64, and these are integrated with the intermediate transfer belt 64 at a predetermined timing. It is supposed to touch. Similarly to the cleaning roll 83, the brush roll 86 is rotated at a peripheral speed substantially equal to the circulation speed of the intermediate transfer belt 64 by a rotation drive source (not shown).

  The intermediate transfer device 62, the photosensitive drum 50, the charging roll 52, the photosensitive drum cleaner 54, and the intermediate transfer belt cleaner 82 are integrated to form a part of the image forming unit 96.

  A fixing device 90 is disposed above the secondary transfer position. The fixing device 90 includes a heating roll 92 and a pressure roll 94, and fixes the toner image secondarily transferred to the recording paper P by the secondary transfer roll 80 and the secondary transfer backup roll 72 to the recording paper P. It is conveyed toward the discharge roll 34. The discharge roll 34 discharges the recording paper P from the discharge port 30 to a discharge unit 36 provided at the upper part of the opening / closing cover 16.

  Next, the operation of the above embodiment will be described.

  During image formation and when toner (regular toner) used for image formation does not exist on the toner carrying surface 64H of the intermediate transfer belt 64 (for example, immediately after the intermediate transfer belt 64 is circulated) The intermediate transfer belt cleaner 82 is set to the contact position, and the conductive sheet 81, the cleaning roll 83, and the brush roll 86 are brought into contact with the toner carrying surface 64H of the intermediate transfer belt 64.

  On the other hand, when the regular toner exists on the toner carrying surface 64H of the intermediate transfer belt 64 at the time of image formation, the intermediate transfer belt cleaner 82 is set to the separation position as shown in FIG. The conductive sheet 81, the cleaning roll 83, and the brush roll 86 are separated from the toner carrying surface 64H of the intermediate transfer belt 64. Accordingly, the toner carrying surface 64H of the intermediate transfer belt 64 can be reliably cleaned only when it is necessary to clean the toner, and the toner can be prevented from being inadvertently removed when cleaning is unnecessary.

  When the image forming signal is sent, the driving force is transmitted to the driving gear of the photosensitive drum 50 by a driving mechanism (not shown), and the photosensitive drum 50 rotates.

  The photosensitive drum 50 is uniformly charged by the charging roll 52, and a light beam is emitted from the exposure device 60 to the charged photosensitive drum 50 based on the image signal. The light beam from the exposure device 60 exposes the surface of the photosensitive drum 50 to form a latent image. The latent image on the photosensitive drum 50 formed by the exposure device 60 is developed with yellow, magenta, cyan, and black toner images by the rotary developing device 38 and is primarily transferred onto the intermediate transfer belt 64. In the primary transfer, waste toner remaining on the photosensitive drum 50 is scraped off and collected by the photosensitive drum cleaner 54.

  On the other hand, the recording paper P stored in the paper feed cassette 22 by a paper feed signal or the like is sent out by the feed roll 24, turned by the retard roll 26, led to the transport path 28, and temporarily stopped by the registration roll 32, It is guided between the secondary transfer roll 80 and the secondary transfer backup roll 72 with timing. When the recording paper P is guided between the secondary transfer roll 80 and the secondary transfer backup roll 72, the toner image primarily transferred to the intermediate transfer belt 64 is transferred to the secondary transfer roll 80, the secondary transfer backup roll 72, and the like. Is secondarily transferred onto the recording paper P.

  The recording paper P to which the toner image has been transferred is guided to the fixing device 90 and the toner image is fixed by the thermal pressure from the heating roll 92. The recording paper P on which the toner image is fixed is discharged from the discharge port 30 to the discharge unit 36 by the discharge roll 34.

After the secondary transfer, waste toner remaining on the toner carrying surface 64H of the intermediate transfer belt 64 is removed and collected by the intermediate transfer belt cleaner 82. That is, the waste toner on the toner carrying surface 64H is first charged to a predetermined charge amount by the conductive sheet 81, and the cleaning surface 83C of the cleaning roll 83 is charged on the toner carrying surface 64H of the intermediate transfer belt 64. The toner is electrostatically adsorbed and removed (cleaned) from the toner carrying surface 64H. At this time, since the cleaning roll 83 rotates at a circumferential speed substantially equal to the circulation speed of the intermediate transfer belt 64, the force in the circulation direction acting on the intermediate transfer belt 64 from the cleaning roll 83 is reduced. Be an intermediate transfer belt 64 having elasticity as in this embodiment, the load is reduced to give, you can reduce the expansion and contraction of the intermediate transfer belt 64.

  Here, in the present embodiment, as shown in FIG. 5, a bias power supply 85 is connected to the conductive sheet 81, and a cleaning backup roll 74 disposed opposite to the conductive sheet 81 with the intermediate transfer belt 64 interposed therebetween. The voltage maintenance element 98 is grounded. Further, the cleaning roll 83 which is downstream of the conductive sheet 81 and faces the cleaning backup roll 74 via the intermediate transfer belt 64 is directly grounded. Therefore, the cleaning backup roll 74 functions as a common counter electrode for the conductive sheet 81 and the cleaning roll 83 and is maintained at a predetermined potential. Then, as shown in FIG. 7, due to the potential difference (1 kV in the example of FIG. 7) between the conductive sheet 81 and the cleaning backup roll 74, the transfer remaining on the toner carrying surface 64H of the intermediate transfer belt 64 after the transfer. The remaining toner is charged and the polarity is controlled so as to have a predetermined polarity. Further, due to the potential difference (700 V in the example of FIG. 7) between the cleaning backup roll 74 and the cleaning roll 83, the toner on the toner carrying surface 64H having the same polarity is adsorbed to the cleaning roll 83.

  As described above, in this embodiment, the cleaning backup roll 74 is grounded via the voltage maintaining element 98, so that the potential can be maintained at a predetermined value, and the toner can be reliably collected by the cleaning roll 83. It becomes.

  In addition, a plurality of power sources are not required to maintain the voltage, and only one bias power source 85 is sufficient, so that the cost is reduced and the intermediate transfer device 12 and the color printer 10 can be downsized.

In this embodiment, the amount B1 of bending of the intermediate transfer belt 64 due to the pressing of the cleaning roll 83 is made shorter than the thickness T1 of the intermediate transfer belt 64 itself so that the intermediate transfer belt 64 is not excessively bent. Thus, the degree of expansion and contraction of the intermediate transfer belt 64 is further suppressed. In addition, the cleaning roller 83 removes the toner on the toner carrying surface 64H while rotating along the circulation direction of the intermediate transfer belt 64. Therefore, even the intermediate transfer belt 64 having elasticity gives an excessive load. Absent.

  FIG. 8 is an enlarged view of the intermediate transfer device 102 according to the second embodiment of the present invention in the vicinity of the intermediate transfer belt cleaner.

  In the second embodiment, the brush backup roll 76 is electrically connected to the cleaning backup roll 74 through the connection line 106 and is grounded via the voltage maintaining element 98.

  A second bias power source 104 is connected to the brush roll 86, and the brush roll 86 is the second bias applying means in the present invention. Further, the brush backup roll 76 is the second belt support means in the present invention.

  The polarity of the voltage (second bias voltage) acting on the toner on the toner carrying surface 64H from the brush roll 86 is the same polarity as the voltage acting on the toner from the conductive sheet 81 (first bias voltage).

  Therefore, in the second embodiment, an electrical path that is grounded from the brush roll 86 through the brush backup roll 76, the cleaning backup roll 74, and the voltage maintaining element 98 is configured.

  A predetermined potential difference is also stably maintained between the brush roll 86 and the brush backup roll 76. For this reason, the toner on the toner carrying surface 64H that could not be removed by the cleaning roll 83 is again charged with the same polarity. Then, the toner can be transferred again to the photosensitive drum 50 and removed from the toner carrying surface 64H.

Further, since the potential of the cleaning backup roll 74 can be stabilized, the degree of freedom in setting the first bias voltage in the conductive sheet 81 is increased. For example, the sticking force to the intermediate transfer belt 64, the charge amount of the toner on the toner carrying surface 64H, and the like can be set to more appropriate values.

It can be adsorbed again by the potential difference between the brush roll 86 and the brush backup roll 76 and removed from the toner carrying surface 64H, and a higher cleaning effect can be obtained.

  In the second embodiment, as shown in FIG. 9, the polarity of the second bias voltage that acts on the toner on the toner carrying surface 64H from the brush roll 86 is the same as the first bias voltage that acts on the toner from the conductive sheet 81. The polarity may be the same. If the polarity is the same, the toner on the toner carrying surface 64H that could not be removed by the cleaning roll 83 is again charged to the same polarity. Then, the toner can be transferred again to the photosensitive drum 50 and removed from the toner carrying surface 64H.

  In FIG. 9, the intermediate transfer device 122 according to the third embodiment of the present invention is shown enlarged in the vicinity of the intermediate transfer belt cleaner as in FIG.

  The third embodiment is different from the second embodiment in that the cleaning backup roll 74 and the brush backup roll 76 are insulated, and the brush backup roll 76 is directly grounded by the ground wire 124. Therefore, the potential of the brush backup roll 76 is always maintained at 0V. The polarity of the second bias voltage that acts on the toner on the toner carrying surface 64H from the brush roll 86 is the same as the polarity of the first bias voltage that acts on the toner from the conductive sheet 81.

  Also in the third embodiment having such a configuration, similarly to the second embodiment shown in FIG. 8, the toner on the toner carrying surface 64H that could not be removed by the cleaning roll 83 is again charged to the same polarity, Further, the toner can be transferred again to the photosensitive drum 50 and removed from the toner carrying surface 64H.

  Further, in the third embodiment, an independent circuit is configured by the brush backup roll 76 and the brush roll 86 as compared with the second embodiment, so the voltage of the brush roll 86 (second bias voltage) is It can be set smaller than in the second embodiment. In particular, the second bias power source 104 is preferably a constant current type power source, but in this case, the voltage also changes as the electrical resistance of the intermediate transfer belt 64 increases. A high voltage and stable power source is required, resulting in high costs. On the other hand, in the third embodiment, since the second bias power supply 104 having a lower voltage than that of the second embodiment can be used, it can be configured at a low cost.

  In the second embodiment and the third embodiment, the second bias applying unit is not limited to the brush roll 86 described above. For example, the second roll applying unit is configured to rotate the metal roll in the same direction as the circulation direction of the intermediate transfer belt 64 (rotary type). Metal roll).

  In the third embodiment, as in the modification shown in FIG. 10, the polarity of the second bias voltage that acts on the toner on the toner carrying surface 64H from the brush roll 86 is the same as the polarity that acts on the toner from the conductive sheet 81. The toner on the toner carrying surface 64H that has a polarity opposite to 1 bias voltage and could not be removed by the cleaning roll 83 may be adsorbed again by the brush roll 86 and removed from the toner carrying surface 64H.

  In the above description, the conductive sheet 81 is taken as an example of the bias applying means of the present invention. However, if the toner on the toner carrying surface 64H of the intermediate transfer belt 64 can be stably charged at a predetermined potential, The configuration is not particularly limited. For example, the conductive brush 132 shown in FIG. 11 may be used so that the tips of the flocks 134 of the conductive brush 132 are in contact with the intermediate transfer belt 64 in the circulation direction. When the conductive brush 132 is used, the tips of the numerous flocks 134 come into contact with the toner carrying surface 64H, so that the toner can be charged more evenly.

Similarly, the configuration (material and shape) of the toner scraping member of the present invention is not limited as long as the toner on the outer peripheral surface of the cleaning roll 83 can be reliably removed. For example, a resin plate member such as the urethane blade 142 shown in FIG. 12 is used, and the tip of the scraper 84 is arranged so as to face the outer peripheral surface in the direction opposite to the rotation direction of the cleaning roll 83, similarly to the scraper 84. May be. Further, as shown in FIG. 13, the pad 146 may be pressed against the outer peripheral surface of the cleaning roll 83 and the toner on the outer peripheral surface of the cleaning roll 83 may be scraped off.

  The medium on which the image is formed by the color printer 10 of the present invention is not limited to the recording paper P, and may be, for example, an OHP sheet.

1 is a cross-sectional view schematically showing an intermediate transfer device according to an embodiment of the present invention and a color printer using the intermediate transfer device. FIG. 3 is an enlarged cross-sectional view illustrating the vicinity of an intermediate transfer belt cleaner of the intermediate transfer device according to the first embodiment of the present invention at a position where the intermediate transfer belt is in contact with the intermediate transfer belt cleaner. FIG. 3 is an enlarged cross-sectional view showing the vicinity of an intermediate transfer belt cleaner of the intermediate transfer device according to the first embodiment of the present invention at a position away from the intermediate transfer belt. FIG. 4 is an enlarged cross-sectional view showing the vicinity of a cleaning roll of the intermediate transfer device according to the first embodiment of the present invention at a position where the intermediate transfer belt is in contact with the intermediate transfer belt. FIG. 3 is an explanatory view schematically showing the vicinity of an intermediate transfer belt cleaner of the intermediate transfer device according to the first embodiment of the present invention. FIG. 3 is an explanatory diagram showing an intermediate transfer belt cleaner of the intermediate transfer device according to the first embodiment of the present invention including a cleaning roll and a scraper. FIG. 3 is an explanatory diagram showing potentials of a conductive sheet, a cleaning backup roll, and a cleaning roll in the intermediate transfer belt cleaner according to the first embodiment of the present invention. FIG. 10 is an explanatory diagram schematically showing the vicinity of an intermediate transfer belt cleaner of an intermediate transfer device according to a second embodiment of the present invention. FIG. 10 is an explanatory view schematically showing the vicinity of an intermediate transfer belt cleaner of an intermediate transfer apparatus according to a modification of the third embodiment of the present invention. FIG. 10 is an explanatory view schematically showing the vicinity of an intermediate transfer belt cleaner of an intermediate transfer apparatus according to a modification of the third embodiment of the present invention. It is explanatory drawing which shows the example using the electroconductive brush as an example of the bias application means based on this invention. It is explanatory drawing which shows the example using the urethane blade as an example of the toner scraping member which concerns on this invention. It is explanatory drawing which shows the example by which the pad was used as an example of the toner scraping member which concerns on this invention.

Explanation of symbols

10 Color printer (image forming device)
12 Color printer main body 14 Rotation fulcrum 16 Opening / closing cover 18 Paper feed unit 20 Paper feed unit main body 22 Paper feed cassette 24 Feed roll 26 Retard roll 28 Transport section 28 Transport path 30 Discharge port 32 Registration roll 34 Discharge roll 36 Discharge section 38 Rotary Developing device 40 Developing device main body 42a Developing device 44 Rotary developing device center 46a Developing roller 48a Elastic body 49 Rotating spindle 50 Photosensitive drum 50 Anti-photosensitive drum 52 Charging roll 54 Photosensitive drum cleaner 56 Cleaning blade 58 Toner recovery case 60 Exposure device 62 Intermediate transfer device 64 Intermediate transfer belt 64H Toner carrying surface 66 Primary transfer roll 68 Wrap-in roll 70 Wrap-out roll 72 Secondary transfer backup roll 74 Cleaning backup roll (belt support means)
76 Brush backup roll (second belt support means)
78 Reflective type photo sensor 80 Secondary transfer roll 81 Charge control sheet (sheet bias applying means)
82 Intermediate Transfer Belt Cleaner 83 Cleaning Roll (Rotary Cleaning Member)
83C Cleaning surface (cleaning part)
84 Scraper (toner scraping member)
84C Cleaning unit 86 Brush roll 88 Toner recovery case 89 Rotating spindle 90 Fixing device 92 Heating roll 94 Pressure roll 96 Image forming unit 98 Voltage maintaining element (voltage maintaining means)
132 Conductive brush (brush-like bias applying means)
142 Urethane blade (toner scraping member)
146 Pad (toner scraping member)
P Recording paper

Claims (14)

Is formed in an endless shape, and the intermediate transcription belt Rutotomoni circulated rotatably supported by a plurality of belt supporting means, the surface is the toner carrying surface for carrying the toner,
Bias applying means for applying a bias voltage to the toner on the toner carrying surface of the intermediate transfer belt disposed opposite to at least one of the belt supporting means via the intermediate transfer belt;
Power supply means for supplying the bias voltage to the bias applying means;
A rotary cleaning member disposed in the vicinity of the bias applying unit and downstream of the bias applying unit in the circulation direction of the intermediate transfer belt, and rotatable along the circulation direction of the intermediate transfer belt;
With
The rotary cleaning member is directly grounded;
An intermediate transfer apparatus , wherein among the plurality of belt support means, a belt support means arranged to face the bias applying means is grounded via a voltage maintaining means.   The bias applying means is a sheet-like bias applying means formed in a sheet shape and disposed so as to contact the intermediate transfer belt along the same direction as the circulation direction of the intermediate transfer belt. Item 4. The intermediate transfer device according to Item 1.   The bias applying means is a brush-like bias applying means formed in a brush shape and disposed so as to contact the intermediate transfer belt along the same direction as the circulation direction of the intermediate transfer belt. Item 4. The intermediate transfer device according to Item 1.   The said cleaning member is arrange | positioned so that an intermediate transfer belt may be pressed with the amount of bending smaller than the thickness of the said intermediate transfer belt, The Claim 1 characterized by the above-mentioned. Intermediate transfer device. The rotary cleaning member is a metal cleaning roll made of metal;
A toner scraping member that scrapes the toner in contact with the surface of the metal cleaning roll;
The intermediate transfer apparatus according to claim 4, further comprising: A second belt support means for supporting the intermediate transfer belt from the opposite side of the toner carrying surface on the downstream side in the circulating direction of the intermediate transfer belt with respect to the belt support means on which the bias applying means is arranged oppositely;
Second bias applying means for applying a second bias voltage to the toner on the toner carrying surface of the intermediate transfer belt that is opposed to the second belt supporting means and the intermediate transfer belt;
Second power supply means for supplying the second bias voltage to the second bias applying means;
The intermediate transfer device according to claim 1, comprising:   The second bias applying means is a second brush-like bias applying means that is formed in a brush shape and is disposed so as to contact the intermediate transfer belt along the same direction as the circulation direction of the intermediate transfer belt. The intermediate transfer device according to claim 6.   The intermediate transfer apparatus according to claim 6, wherein the second bias applying unit is a rotating metal roll made of metal and rotatable along a circulation direction of the intermediate transfer belt. The second belt support means is electrically connected to the belt support means in which the bias applying means is disposed oppositely;
9. The intermediate transfer device according to claim 6, wherein the rotary cleaning member is directly grounded.   The said 2nd belt support means is electrically insulated from the belt support means by which the said bias application means is opposingly arranged, and is directly earth | grounded, The said any one of Claims 6-8 characterized by the above-mentioned. The intermediate transfer apparatus according to item 1.   The intermediate transfer device according to claim 10, wherein the second bias voltage has a polarity opposite to that of the bias voltage.   The intermediate transfer device according to claim 9 or 10, wherein the second bias voltage has the same polarity as the bias voltage.   The belt support means and the second belt support means in which the bias applying means is arranged to face each other are arranged at an interval constituting a short side in a state where the intermediate transfer belt is supported. Item 12. The intermediate transfer device according to any one of Items 6 to 11. The intermediate transfer device according to any one of claims 1 to 13,
A primary transfer unit that primarily transfers a toner image to the intermediate transfer device;
A secondary transfer portion for secondary transfer of the toner image of the intermediate transfer device to a recording medium;
An image forming apparatus comprising:

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