JP2008209844A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact, long-life and inexpensive image-forming apparatus capable of forming a record image of high image quality without affecting the formation of a toner image on a photoreceptor by a seam part of a transfer belt. <P>SOLUTION: A means for detecting the position of the seam on an intermediate transfer belt is disposed in a non-image area of the edge of an intermediate transfer belt 100 in its rotating direction. Based on the result of the detection, an area from the point immediately before the contact of the seam with the photoreceptor drum to the point beyond one rotation of the photoreceptor after the contact is assigned as a non-image area. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or the like that employs an image forming method such as an electrophotographic method, an electrostatic recording method, an ionography method, or a magnetic recording method, and particularly forms an image on a transfer belt. The present invention relates to an image forming apparatus.

    Conventionally, as an image forming apparatus for forming an image by transferring a toner image formed on a photosensitive drum onto an endless transfer belt, one shown in FIG. 11 is known (Patent Document 1).

  FIG. 11 is a schematic diagram showing a tandem color image forming apparatus in which four photosensitive drums 50 (50Y to 50K) are arranged in series along the rotation path of the intermediate transfer belt 100. FIG. In this apparatus, toner images of yellow Y, magenta M, cyan C, and black BK are sequentially formed on the photosensitive drums 50 with a predetermined time difference, and the toner images are overlapped on the intermediate transfer belt 100 to be multiplexed. A transfer toner image is formed, and the toner images of a plurality of colors are retransferred to the recording material 60. Finally, the recording material 60 is inserted into the fixing device 70 to obtain a color image.

  The photoconductor drum 50 is formed by applying and forming a photoconductor made of an organic photoconductor (OPC) on the outer peripheral surface of an aluminum cylinder having a diameter of 24 mm, and is driven to rotate in the direction of the arrow by a driving means (not shown). The photoreceptor drum 50 may be one using a photoreceptor such as a-Si, CdS, or Se.

  The surface of the photosensitive drum 50 is uniformly charged to approximately −600 V on the photosensitive drum 50 by the charging roller 51 by applying a DC voltage of −1200 V to the charging roller 51 (51Y to 51K).

  The image forming apparatus is provided with a laser diode, an exposure device (not shown) including a polygon mirror, a lens and a folding mirror that are rotationally driven by a high-speed motor. For example, from a laser diode modulated by a signal according to yellow image information Is irradiated onto the surface of the charged photosensitive drum 50Y, the potential of the irradiated portion is attenuated to about -50V, and an electrostatic latent image corresponding to image information is formed on the surface of the photosensitive drum 50Y. The

  This electrostatic latent image moves to the developing position as the photosensitive drum 50Y rotates, and is developed by the developing roller 40Y positioned there, and visualized as a yellow toner image. The yellow toner image formed on the photoreceptor drum 50Y is transferred to the intermediate transfer belt 100 by applying a DC primary transfer voltage of +600 V to the primary transfer roller 101Y from a primary transfer power source (not shown) at a transfer portion facing the intermediate transfer belt 100. Transferred to the surface of the belt 100.

  By repeating the same process as above for three colors of magenta, cyan, and black, a color image in which toner images of four colors of yellow, magenta, cyan, and black are superimposed and transferred to the intermediate transfer belt 100 is formed. The four color toner images on the intermediate transfer belt 100 are applied with a secondary transfer voltage from a secondary transfer power source (not shown) to the secondary transfer roller 102 on the surface of the recording material 60 conveyed to the intermediate transfer belt 100. Are collectively transferred. The recording material 60 is fed from a cassette 61 or a multi-tray. In this example, the recording material 60 is plain paper, but may be an OHP sheet.

  The recording material 60 onto which the four color toner images have been transferred is conveyed to a fixing device 70 where the toner is melted and fixed by heating and pressing to complete a full color image, and then discharged to a face-down tray (not shown). .

  The photoreceptor drum 50 is cleaned and removed by the cleaning device 52 such as a blade from the primary transfer residual toner remaining on the surface. The intermediate transfer belt 100 is cleaned and removed by the cleaning device 103 such as a fur brush or a blade after the secondary transfer residual toner remaining on the surface.

  Here, the intermediate transfer belt 100 is made of a dielectric resin having a thickness of 30 to 300 μm in which resistance is adjusted by mixing carbon or the like into a resin such as polycarbonate resin, polyurethane resin, polyethylene terephthalate resin, or polyethersulfane resin. It is a film.

  The endless intermediate transfer belt 100 as described above can be manufactured seamlessly so-called seamlessly. However, in recent years, an intermediate transfer belt that has been processed into an endless shape by joining both ends of the endless belt using a technique such as ultrasonic welding in view of difficulty in molding, difficulty in packaging during transportation, cost, etc. The use is increasing.

  However, these endless intermediate transfer belts that have been joined have a seam portion that is a seam, and this seam portion is welded with the belt end overlapping, so that the thickness increases compared to other portions. ing. In addition, a phenomenon such as paper powder or toner easily entering a stepped portion generated by increasing the thickness tends to occur.

  For this reason, the resistance value of the seam portion of the intermediate transfer belt 100 is greatly different from that of other portions. When the seam portion having a greatly different resistance value comes into contact with the photosensitive drum 50, the contacted photosensitive drum 50. There has been a problem that a special potential history is formed only in the upper region.

  When the next toner image is formed on the area on the photosensitive drum 50 that is in contact with the seam portion, a toner image having a desired density cannot be obtained for the area, and the seam portion is added to the formed recorded image. This causes a problem that the horizontal horizontal stripes corresponding to the above occur.

  Up until now, horizontal streaks due to potential history on the photosensitive drum have been inconspicuous due to a lot of jitter and toner scattering due to uneven rotation of the drive, etc. With the technical progress, the image quality has been remarkably improved, and the horizontal stripes due to the potential history on the photosensitive drum 50 are beginning to be noticeable.

  In view of this, the conventional technology for solving this problem is that, with respect to the photosensitive drum after the transfer of the toner image, the electrostatic latent image history in the previous cycle is erased prior to the next toner image formation cycle. And a static eliminator such as a static elimination lamp 30 (30Y to 30K).

  Further, in order to more effectively erase the history of the electrostatic latent image, it has a detecting means for detecting the position of the seam portion existing on the intermediate transfer belt 100, and based on the detection result by the detecting means, The voltage applied to the static elimination corotron and the static elimination lamp is changed so that the seam portion corresponds to the portion in contact with the photosensitive drum, and the potential on the photosensitive drum is controlled to be uniform.

In other words, in order to erase the history of the electrostatic latent image generated on the photosensitive drum 50 by areas having different electrostatic characteristics on the intermediate transfer belt 100, potential unevenness correcting means for correcting the surface potential of the photosensitive drum is provided. ing.
Japanese Patent No. 3365154

  By the way, in the image forming apparatus configured as described above, it is necessary to dispose the potential unevenness correcting means such as the static eliminating corotron and the static eliminating lamp between the transfer position on the photosensitive drum and the cleaning device. Therefore, it is necessary to secure a space for arranging the potential unevenness means. In order to secure the space, it is necessary to increase the diameter of the photosensitive drum. As a result, there is a problem that the entire image forming apparatus is increased in size.

  In addition, in order to arrange the potential unevenness correction means such as the static elimination corotron and the static elimination lamp, not only the correction means but also a power source and a harness for applying a voltage to the correction means are required, and the entire apparatus is expensive. There is also a problem.

  Further, since the potential unevenness correcting means is disposed in the vicinity of the above-described cleaning device, the toner on the photosensitive drum scraped off by the cleaning device easily adheres to the potential unevenness correcting means, and is desired as time passes. There is also a problem that the neutralization effect cannot be obtained.

  Further, since the potential unevenness correcting means is arranged at a certain distance from the photosensitive drum, it is difficult to correct the surface potential of only the portion where the seam portion is in contact with the photosensitive drum. There are also problems such as potential unevenness remaining on the photosensitive drum, and the effect of removing static electricity acting more strongly than desired to shorten the life of the photosensitive drum. For example, when an optical static eliminator is used as the potential unevenness correcting means, there is a problem that light deterioration (exposure) is likely to occur on the photosensitive drum, and the lifetime of the photosensitive drum becomes shorter than a desired lifetime.

  The present invention has been made in view of the above points, and corrects the surface potential for erasing the history of the electrostatic latent image generated on the photosensitive drum by using regions having different electrostatic characteristics on the intermediate transfer belt. It is an object of the present invention to provide an image forming apparatus that forms an inexpensive and good image without providing potential unevenness correcting means.

In order to solve this problem, a first image forming apparatus of the present invention includes an image carrier that carries a toner image, a charging unit that charges the image carrier, and a toner image on the image carrier that is transferred. A transfer belt having different regions with different electrostatic characteristics, a transfer means for transferring the toner image on the image carrier onto the transfer belt, and a detection means for detecting a predetermined portion of the transfer belt. In the image forming apparatus in which the toner image on the transfer belt is transferred to a recording material, the image carrier and the image carrier in the image carrier based on the detection result of the predetermined portion of the transfer belt by the detection unit. A contact portion that contacts the dissimilar region of the transfer belt, and a potential uneven portion that is formed continuously on the downstream side in the rotation direction of the image carrier with respect to the contact portion and is generated on the image carrier by the contact. At least As both parts are non-image areas, the timing for forming a toner image to the image bearing member is being controlled.
In addition, the second image forming apparatus of the present invention has an electrostatic property on which an image carrier that carries a toner image, a charging unit that charges the image carrier, and a toner image on the image carrier is transferred. A transfer belt having different regions, a transfer means for transferring a toner image on the image carrier onto the transfer belt, and a detection means for detecting a predetermined portion of the transfer belt, In the image forming apparatus in which the toner image is transferred to the recording material, the image carrier and the different areas of the transfer belt in the image carrier are determined based on the detection result of the predetermined portion of the transfer belt by the detection unit. At least both portions of the contact unevenness portion that is formed continuously on the downstream side in the rotation direction of the image carrier with respect to the contact portion, and that is generated on the image carrier by the contact. means After passing through the charging area formed between the charging to the image bearing member is controlled to be started by said charging means, characterized in that.
Further, the third image forming apparatus of the present invention has an image bearing member that carries a toner image, a charging unit that charges the image carrier, and electrostatic characteristics to which the toner image on the image carrier is transferred. A transfer belt having different regions, a transfer means for transferring a toner image on the image carrier onto the transfer belt, and a detection means for detecting a predetermined portion of the transfer belt, In the image forming apparatus in which the toner image is transferred to the recording material, the image carrier and the different areas of the transfer belt in the image carrier are determined based on the detection result of the predetermined portion of the transfer belt by the detection unit. A timing at which a toner image is formed on the image carrier so that one rotation of the image carrier is a non-image area over the downstream side in the rotation direction of the image carrier relative to the contact portion. Is controlled That, characterized in that.
According to a fourth image forming apparatus of the present invention, there is provided an image carrier that carries a toner image, a transfer belt having different regions with different electrostatic characteristics to which the toner image on the image carrier is transferred, and the image An image having transfer means for transferring the toner image on the carrier onto the transfer belt, and detection means for detecting a predetermined portion of the transfer belt, wherein the toner image on the transfer belt is transferred to a recording material In the forming apparatus, based on the detection result of the predetermined portion of the transfer belt by the detection unit, the image carrier includes the dissimilar region on the transfer belt and extends downstream from the dissimilar region in the traveling direction of the transfer belt. The timing for forming a toner image on the image carrier is set so as to avoid a range corresponding to the length of one rotation of the body.
The fifth image forming apparatus of the present invention includes an image carrier that carries a toner image, a transfer belt having different regions with different electrostatic characteristics to which the toner image on the image carrier is transferred, and the transfer Detecting means for detecting a predetermined portion of the belt, and in an image forming apparatus in which the toner image on the transfer belt is transferred to a recording material, based on the detection result of the predetermined portion of the transfer belt by the detecting means. In order to avoid a range corresponding to the length of one rotation of the image carrier over the downstream side in the traveling direction of the transfer belt with respect to the different region, including the different region in the transfer belt, A process speed of the image forming apparatus is set.
Further, the sixth image forming apparatus of the present invention includes an image carrier that carries a toner image, a transfer belt having different regions with different electrostatic characteristics to which the toner image on the image carrier is transferred, and the transfer Detecting means for detecting a predetermined portion of the belt, and in an image forming apparatus in which the toner image on the transfer belt is transferred to a recording material, based on the detection result of the predetermined portion of the transfer belt by the detecting means. In order to avoid a range corresponding to the length of one rotation of the image carrier over the downstream side in the traveling direction of the transfer belt with respect to the different region, including the different region in the transfer belt, The length of the transfer belt is set.
In the first to sixth image forming apparatuses described above, the different regions of the transfer belt are, as a specific example, a seam portion of the transfer belt formed in an endless manner.
In the first to sixth image forming apparatuses described above, an area upstream of the transfer belt in the moving direction with respect to the different area of the transfer belt (an area upstream in the rotation direction of the contact portion between the image carrier and the different area) is defined. It may be included.

  According to the present invention, the history portion is made a non-image area without erasing the history of the electrostatic latent image generated on the photosensitive drum by the different types of areas having different electrostatic characteristics on the intermediate transfer belt. An object of the present invention is to provide an image forming apparatus having a small and inexpensive configuration without adding parts.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the component and equivalent part which have the same structure or function, and the description is not repeated.
(Embodiment 1)
An image forming apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram of an image forming apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the image forming apparatus includes an intermediate transfer belt (corresponding to a transfer belt) 100 that intermediately transfers a toner image formed on a photosensitive drum (corresponding to an image carrier) 50. As shown in FIG. 2, as a recognition display indicating a position of a seam portion (corresponding to a different region) of the intermediate transfer belt 100, a predetermined portion of the non-image area at the end along the rotation direction of the transfer belt 100 is penetrated. A hole 110 is formed. A light-passing through-hole sensor (corresponding to detection means) 111 is disposed at one position of the intermediate transfer belt 100 with the end of the intermediate transfer belt 100 interposed therebetween, and detects the through-hole 110. Since the length from the through hole 110 to the seam portion 120 is set to a predetermined length Y, when the position of the through hole 110 is detected, the position on the intermediate transfer belt 100 where the seam portion 120 exists is grasped. can do.

  The through hole 110 may have a notch shape, or may be detected by a light reflection plate or a light reflection type reflected light detection sensor instead of the through hole 110 and the through hole sensor 111.

  As shown in FIG. 1 and FIG. 2, an intermediate transfer belt 100 is formed by ultrasonic welding both ends of a dielectric film having a thickness of 100 μm, and ultrasonic welding is performed at one place on the circumference thereof. There is a seam portion (joint) 120 formed by. The intermediate transfer belt 100 is wound around four rolls including a driving roller 104 and an edge guide roll 105, and is given a predetermined tension by an edge guide roll 105 biased by a spring (not shown).

  As a method of joining the intermediate transfer belt 100, a conductive adhesive or seal may be used instead of ultrasonic welding.

Next, a schematic enlarged view of the seam portion 120 is shown in FIG. 3, and the seam portion where the end portions of the belt are joined together using ultrasonic welding will be described.
The seam portion 120 constitutes a heterogeneous region having different electrostatic characteristics from other regions of the intermediate transfer belt 100.
As shown in FIG. 3A, since the seam portion 120 of the intermediate transfer belt 100 is ultrasonically welded with the intermediate transfer belt ends overlapped, the convex portion as shown in FIG. Since it is formed, the thickness t ′ of the seam portion is thicker than the thickness t = 100 μm of other portions. Further, since the seam portion 120 has a convex shape, paper dust and toner of the recording material 60 are easily collected at a step portion between the convex portion of the seam portion 120 and another flat portion. Therefore, in the seam portion 120, the resistance value in the thickness direction of the intermediate transfer belt 100 tends to be higher than other portions.

  On the other hand, a positive charge for transferring the toner image on the photosensitive drum 50 to the intermediate transfer belt 100 exists on the back side of the intermediate transfer belt 100. When a portion other than the seam portion 120 of the intermediate transfer belt 100 passes through a transfer portion where a primary transfer roller (corresponding to a transfer unit) 101 is disposed and comes into contact with the photosensitive drum 50, Since the positive charge flows into the negatively charged photosensitive drum 50 and the surface of the photosensitive drum 50 is neutralized, as shown in FIG. 4A, the surface of the photosensitive drum 50 that has passed the primary transfer position. The potential is a value close to substantially zero.

  However, when the seam portion 120 passes through the transfer portion on which the primary transfer roller 101 is disposed and comes into contact with the photosensitive drum 50, the positive charge on the back surface side of the intermediate transfer belt 100 passes through the high resistance seam portion 120. It becomes difficult to flow into the drum 50, and a positive charge is not injected into a part of the photosensitive drum 50 that is used for negative charging, and a residual negative charging region is generated. It becomes a uniform state.

  As a result, the surface potential on the photosensitive drum 50 that has passed through the primary transfer portion remains negatively charged only in the region in contact with the seam portion 120 as shown in FIG. 4B. If negative charges remain on the surface of the photosensitive drum 50 as described above, if negative charges are again applied to the photosensitive drum 50 by the charging roller (corresponding to the charging means) 51, as shown in FIG. In addition, the negative charging potential is higher than the set value, and the negative charging potential is increased only in the region in contact with the seam portion 120. For this reason, even when the laser beam from the laser diode modulated by the signal according to the image information is irradiated onto the photosensitive drum 50, as shown in FIG. And the non-uniform electrostatic latent image is formed on the surface of the photosensitive drum 50. In other words, the potential after irradiation on the photosensitive drum 50 cannot be attenuated only in the portion in contact with the seam portion 120, the negative potential becomes high, and a negatively charged toner image is formed on the photosensitive drum 50 in that region. As a result, white horizontal streaks occur and the quality of the color image is significantly impaired.

  In order to solve this problem, the conventional technique shown in Japanese Patent Application Laid-Open No. H10-228561 makes the potential on the photosensitive drum 50 non-uniform after the transfer as described above uniform, as shown in FIG. The potential unevenness correcting means 30 such as the above is provided, but the cost increases due to the addition of parts, and a space for arranging the parts around the photoreceptor is required, and the diameter of the photoreceptor drum 50 must be increased. As a result, the entire image forming apparatus is increased in size.

  Further, since the potential unevenness correcting means is arranged at a certain distance from the photosensitive drum, the potential unevenness is corrected over a wide range, and the potential unevenness is corrected over a wider range than the portion where the seam portion is in contact. Make corrections. Therefore, even if the potential is changed to a portion other than the seam portion, and the negative charge is again applied to the photosensitive drum 50 by the charging roller 51, the surface potential of the photosensitive drum is not uniform, and a non-uniform toner image. There is also a problem that is formed.

  In the present embodiment, as shown in FIGS. 5, 6, and 7, each of the seam portions 120 existing on the intermediate transfer belt 100 is based on the detection result of the through-hole sensor 111 that can grasp the position of the seam portion 120. The timing of contact with the photosensitive drum can be calculated, and a potential unevenness region (potential unevenness portion) on the photosensitive drum 50 generated by the contact between the seam portion 120 and the photosensitive drum 50 passes through the charging roller 51. The timing to perform can also be calculated. Therefore, a predetermined voltage is applied to the charging roller 51 after the contact portion on the photosensitive drum 50 and the potential unevenness region pass through a charging region formed between the photosensitive drum and the charging roller 51, A printing operation is started.

  After the through hole sensor 111 detects the through hole 110, the belt travels a distance of (L−L ′), and then the seam portion 120 and the yellow photosensitive drum 50 </ b> Y come into contact with each other. Here, L represents the distance from the through hole sensor to the yellow photosensitive drum 50Y with respect to the traveling direction of the intermediate transfer belt 100, and L ′ represents the traveling direction of the intermediate transfer belt 100. The distance from the through-hole 110 to the seam part 120 is shown.

  Note that L> L ′ is preferable because the travel distance of the intermediate transfer belt 100 becomes shorter.

  Next, after the seam portion 120 comes into contact with the yellow photosensitive drum 50Y, the circumferential length on the yellow photosensitive drum 50Y from the transfer roller 101Y to the charging roller 51Y with respect to the rotation direction of the photosensitive drum 50. After the yellow photosensitive drum 50Y is rotated by L ″, a predetermined voltage is applied to the charging roller 50Y, and laser light is irradiated onto the surface of the yellow photosensitive drum 50Y to form an electrostatic latent image. Is done. For magenta, cyan, and black, printing is started sequentially after a predetermined time from the start of the yellow printing operation. In the case of continuous printing, after printing an image for one sheet, the through-hole sensor 111 detects the through-hole 110 again, and printing is performed after the photosensitive drum 50 is rotated by (L−L ′) + L ″. Start operation.

The timing for starting the yellow printing operation is set to be performed after (L−L ′) + L ″ rotation of the photosensitive drum 50Y as described above, so that it is generated by the seam unit 120 and the seam unit 120. The potential unevenness portion on the photosensitive drum 50 can be made into a non-image region, and a good color image can be formed on the recording material 60 without generating white horizontal stripes.
(Embodiment 2)
Next, an image forming apparatus according to Embodiment 2 of the present invention will be described with reference to FIGS.

  In the first embodiment, if a means for applying a predetermined voltage in contact with the photosensitive drum 50 such as a roller or a brush is used as a means used in the charging process, the transfer roller to the charging roller section is used. Since an accurate value of the distance L ″ can be grasped, a predetermined voltage is applied to the charging roller 51 after the potential unevenness region on the photosensitive drum 50 by the seam portion which is a different region accurately passes through the charging roller 51. Is possible.

  However, when a non-contact means such as corotron or scorotron is used as a charging process means, the exact distance of L ″ cannot be grasped, so the timing of applying a predetermined voltage to the charging roller 51 There is a problem that it is difficult to determine.

  Therefore, in this embodiment, the timing at which the seam portion 120 existing on the intermediate transfer belt 100 contacts each photosensitive drum is calculated based on the detection result of the through-hole sensor 111 that can grasp the position of the seam portion 120. The non-image area is formed immediately before the seam portion 120 and the photosensitive drum 50 are in contact with each other and after the seam portion 120 and the photosensitive drum 50 are in contact with each other until the photosensitive drum 50 exceeds one turn. The process speed is set.

  In other words, in order not to generate white horizontal stripes due to potential unevenness on the photosensitive drum 50 generated by the seam portion, the interval from the contact between the photosensitive drum 50 and the seam portion 120 to the region where the photosensitive drum 50 exceeds one round is provided. Set the process speed to be a non-image area.

Specifically, when the diameter a of the photoconductor is 24 mm, the distance L from the through-hole sensor to the photoconductor 50 is 50 mm, and the distance L ′ from the through-hole sensor to the seam portion 120 is 45 mm, the non-image region X is Since X> (a × π) + (L−L ′),
Since X> (24 × π) + (50−45), the area exceeding 80.4 mm needs to be a non-image area as a result of calculation.

  Next, FIG. 9 shows a timing chart of this embodiment. In this embodiment, the through-hole sensor 111 that detects the position of the belt detects the through-hole 110 on the belt, and then the circumference of the photoreceptor (a × π) and the distance from the seam portion to the photoreceptor. The belt is caused to travel by a distance obtained by adding (LL ′), and then yellow printing is started. After a predetermined time from the start of yellow printing, magenta, cyan, and black toner images are sequentially formed.

Therefore, in this image forming apparatus, in order to output N sheets of A4 vertical size paper per minute, the process speed V (mm / sec) is set to V> (A4 paper vertical length + non-image area X) × (1 minute). Can be expressed as N) / 60,
The process speed is set such that the relationship V> [paper length + (a × π) + (L−L ′)] × N / 60 is established.
To explain using the specific example described above, since the non-image area needs to have a distance exceeding 80.4 mm, the relationship between the process speed V (mm / sec) and the number of sheets output per minute is as follows. ,
V> (297 + 80.4) × (number of printed sheets per minute N) / 60
By designing the image forming apparatus in a relationship of V> N × 6.29, the seam portion 120 and the potential uneven portion on the photosensitive drum 50 generated by the seam portion 120 can be made into a non-image area, and the recording material A good color image can be formed without generating white horizontal stripes on 60.

  Note that it is more preferable that L ′ / L fall within the range of 0.8 <L ′ / L <1 because the non-image area can be set as narrow as possible.

  As a result, it is possible to obtain a good image quality without generating white horizontal stripes without providing a potential unevenness correcting means such as a static elimination corotron or a static elimination lamp that corrects potential unevenness, and it can be configured with a minimum number of parts and thus an inexpensive configuration. The image forming apparatus can be provided.

Further, even when a corotron, scorotron or the like is used as a means for the charging process without being restricted by a roller, a brush or the like, a good image quality can be obtained without generating a horizontal stripe.
(Embodiment 3)
An image forming apparatus according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 10 is a schematic diagram of an image forming apparatus according to Embodiment 3 of the present invention.

  The present embodiment is an invention characterized in that the belt length is set such that a seam portion which is a heterogeneous region and a potential unevenness portion on the photosensitive drum become a non-image region.

  In order to reduce the size of the entire image forming apparatus, it is effective to make the length of the intermediate transfer belt located at the center of the apparatus as short as possible. Therefore, in the conventional image forming apparatus, the length of the intermediate transfer belt is determined without considering the size of paper that can be printed by the image forming apparatus. In other words, the length of the intermediate transfer belt is set to be as short as possible depending on the arrangement of the photosensitive drum and the developing roller, the conveyance path of the recording material, the size of the photosensitive drum, and the like.

  However, when the length of the intermediate transfer belt is set by the method described above, depending on the size of the recording material, it may be difficult to make the potential unevenness portion on the seam portion and the photosensitive drum a non-image region. appear. That is, as shown in FIG. 12, if the length of the intermediate transfer belt is set shorter than the total length of the recording material and the required non-image area, the toner image is formed on the potential unevenness portion on the photosensitive drum. As a result, lateral white streaks appear.

  Therefore, in the present embodiment, the length of the intermediate transfer belt is set to the minimum non-image area (a × π) + (L−L ′) where no horizontal white stripes are generated. It is characterized in that it is set to be longer than the specified length.

By designing the length of the intermediate transfer belt as described above, it is possible to set the seam portion and the non-image area on the photosensitive drum, which is caused by the seam portion. As a result, it is possible to obtain a good image quality without generating white and horizontal stripes without providing a potential unevenness correcting means such as a static elimination corotron or a static elimination lamp for correcting potential unevenness, and it is inexpensive because it can be configured with a minimum number of parts. In the above embodiment, the seam portion in the endless intermediate transfer belt is illustrated as an example of the heterogeneous region. However, the configuration has different electrostatic characteristics from other regions. If so, the dissimilar region is not limited to the seam portion, and for example, it may be applicable to a transfer belt having a structure in which the thickness of the belt in the moving direction is different.
Further, in the above embodiment, the position of the seam portion which is a different region is determined by detecting the through hole provided in the intermediate transfer belt using a sensor. The structure which detects itself directly with a sensor may be sufficient.
In the above embodiment, in order to achieve the effect more reliably, the upstream region (= L−L ′) of the intermediate transfer belt on the upstream side in the moving direction relative to the different region of the intermediate transfer belt (= L−L ′) The non-image area is controlled or configured so as to include the area immediately upstream in the rotation direction of the contact portion with the seam portion of the intermediate transfer belt), but is not limited thereto, and the non-image area is the photosensitive drum. As long as it includes at least the contact portion between the contact portion and the seam portion of the intermediate transfer belt and the potential unevenness portion continuous with the contact portion.
Further, in each of the above embodiments, the present invention uses a tandem type color image forming apparatus in which four photosensitive drums 50 (50Y to 50K) are arranged in series along the rotation path of the intermediate transfer belt 100. In the present invention, a monochrome image forming apparatus using an intermediate transfer belt and a revolver type color which forms a color image on the intermediate transfer belt 100 while rotating a plurality of photosensitive drums 50 sequentially. Even an image forming apparatus is applicable as long as it is an image forming apparatus using an intermediate transfer belt.

  In the above embodiment, the case where only one through-hole sensor 111 for detecting the through-hole 110 is provided has been described. However, the case where a plurality of through-hole sensors 111 are provided is more preferable. The position of the through hole 110 can be detected quickly, and the image forming operation can be started early. That is, even if the intermediate transfer belt 100 stops at a position that is not assumed due to a paper jam or the like, the position of the through hole can be detected at an early stage, so that the image forming time can be shortened.

  The image forming apparatus according to the present invention can form a uniform toner image without using the potential unevenness correcting means even when an intermediate transfer belt having a seam portion is used. It is useful as an image forming apparatus such as a black-and-white and color copying machine, printer, facsimile, etc. that employs an image forming system such as a system, ionography, and magnetic recording system.

1 is a schematic cross-sectional view showing the appearance of an image forming apparatus according to Embodiment 1 of the present invention. 1 is a schematic diagram showing the configuration of an intermediate transfer belt according to Embodiment 1 of the present invention. (A) Schematic diagram before ultrasonically welding the end of the intermediate transfer belt (b) Schematic diagram of the seam portion of the intermediate transfer belt subjected to ultrasonic welding (A) Photosensitive drum surface potential state before and after transfer portion insertion (b) Photosensitive drum surface potential state after contact of the intermediate transfer belt seam portion (c) Seam portion contacted with the drum FIG. 4D is a diagram showing the surface potential state of the photosensitive drum when a negative charge is applied to the exposed portion by the charging roller. (D) When the portion where the seam portion is in contact with the drum is irradiated with a laser beam to form an electrostatic latent image. Of the surface potential of the photosensitive drum 1 is a schematic cross-sectional view of a yellow portion of an image forming apparatus according to Embodiment 1 of the present invention. 1 is a timing chart of an image forming apparatus according to Embodiment 1 of the present invention. Flowchart of Image Forming Unit According to Embodiment 1 of the Present Invention Schematic sectional view of the yellow portion of the image forming apparatus according to Embodiment 2 of the present invention. Timing chart of image forming apparatus according to embodiment 2 of the present invention Schematic showing the configuration of an intermediate transfer belt according to Embodiment 3 of the present invention. Schematic sectional view showing the appearance of an image forming apparatus according to the prior art

Explanation of symbols

30 Static elimination lamp (potential unevenness correction means)
DESCRIPTION OF SYMBOLS 40 Developing roller 50 Photosensitive drum 51 Charging roller 52 Cleaning device 60 Recording material 61 Cassette 70 Fixing device 100 Intermediate transfer belt 101 Primary transfer roller 102 Secondary transfer roller 110 Through-hole 111 Through-hole sensor 120 Seam part

Claims (8)

An image carrier for carrying a toner image;
Charging means for charging the image carrier;
A transfer belt having different regions with different electrostatic characteristics to which a toner image on the image carrier is transferred;
Transfer means for transferring the toner image on the image carrier onto the transfer belt;
Detecting means for detecting a predetermined portion of the transfer belt,
In the image forming apparatus in which the toner image on the transfer belt is transferred to a recording material,
Based on the detection result of the predetermined portion of the transfer belt by the detection means,
A contact portion of the image carrier that contacts the image carrier and the dissimilar region of the transfer belt; and the contact portion that is continuously formed downstream of the contact portion in the rotation direction of the image carrier. The image forming apparatus is characterized in that the timing of forming a toner image on the image carrier is controlled so that at least both of the potential unevenness portions generated on the image carrier become non-image areas. An image carrier for carrying a toner image;
Charging means for charging the image carrier;
A transfer belt having different regions with different electrostatic characteristics to which a toner image on the image carrier is transferred;
Transfer means for transferring the toner image on the image carrier onto the transfer belt;
Detecting means for detecting a predetermined portion of the transfer belt,
In the image forming apparatus in which the toner image on the transfer belt is transferred to a recording material,
Based on the detection result of the predetermined portion of the transfer belt by the detection means,
A contact portion of the image carrier that contacts the image carrier and the dissimilar region of the transfer belt; and the contact portion that is continuously formed downstream of the contact portion in the rotation direction of the image carrier. So that charging of the image carrier by the charging unit is started after at least both portions of the potential unevenness portion generated on the image carrier pass through a charging region formed with the charging unit. To control,
An image forming apparatus. An image carrier for carrying a toner image;
Charging means for charging the image carrier;
A transfer belt having different regions with different electrostatic characteristics to which a toner image on the image carrier is transferred;
Transfer means for transferring the toner image on the image carrier onto the transfer belt;
Detecting means for detecting a predetermined portion of the transfer belt,
In the image forming apparatus in which the toner image on the transfer belt is transferred to a recording material,
Based on the detection result of the predetermined portion of the transfer belt by the detection means,
The image carrier includes a contact portion where the image carrier and the dissimilar region of the transfer belt are in contact with each other, and one rotation of the image carrier over the downstream side in the rotation direction of the image carrier with respect to the contact portion. To be a non-image area,
The timing for forming a toner image on the image carrier is controlled.
An image forming apparatus. An image carrier for carrying a toner image;
A transfer belt having different regions with different electrostatic characteristics to which a toner image on the image carrier is transferred;
Transfer means for transferring the toner image on the image carrier onto the transfer belt;
Detecting means for detecting a predetermined portion of the transfer belt,
In the image forming apparatus in which the toner image on the transfer belt is transferred to a recording material,
Based on the detection result of the predetermined portion of the transfer belt by the detection means,
In the transfer belt, including the different region, so as to avoid a range corresponding to the length of one rotation of the image carrier across the downstream direction of the transfer belt with respect to the different region,
Timing for forming a toner image on the image carrier is set.
An image forming apparatus. An image carrier for carrying a toner image;
A transfer belt having different regions with different electrostatic characteristics to which a toner image on the image carrier is transferred;
Detecting means for detecting a predetermined portion of the transfer belt,
In the image forming apparatus in which the toner image on the transfer belt is transferred to a recording material,
Based on the detection result of the predetermined portion of the transfer belt by the detection means,
The transfer belt includes the heterogeneous region, and a range corresponding to the length of one rotation of the image carrier over the downstream side of the transfer belt with respect to the heterogeneous region can be avoided. The process speed of the image forming apparatus is set,
An image forming apparatus. An image carrier for carrying a toner image;
A transfer belt having different regions with different electrostatic characteristics to which a toner image on the image carrier is transferred;
Detecting means for detecting a predetermined portion of the transfer belt,
In the image forming apparatus in which the toner image on the transfer belt is transferred to a recording material,
Based on the detection result of the predetermined portion of the transfer belt by the detection means,
The transfer belt includes the heterogeneous region, and a range corresponding to the length of one rotation of the image carrier over the downstream side of the transfer belt with respect to the heterogeneous region can be avoided. The transfer belt length is set,
An image forming apparatus. 7. The image forming apparatus according to claim 1, wherein the different region of the transfer belt is a seam portion of the transfer belt formed in an endless shape. The image forming apparatus according to claim 1, wherein the different region of the transfer belt has a higher electrical resistance value than other regions.

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