JP3665785B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, or a printer. More specifically, the present invention relates to a toner composed of toners of different colors, which are formed by developing latent images on the surfaces of a plurality of latent image carriers. The present invention relates to an image forming apparatus for sequentially transferring an image onto a recording material conveyed by a transfer belt to form an image.
[0002]
[Prior art]
Conventionally, as an image forming apparatus of this type, a latent image is formed on the surface of a latent image carrier made of, for example, a photosensitive drum by a known image forming process, and the latent image is developed with a developing device to form a toner image. An image forming apparatus for forming an image by transferring the toner image to a recording material, comprising a plurality of latent image carriers and developing devices, each of which forms a toner image composed of toner of different colors, It is known that each toner image is sequentially transferred onto a recording material conveyed by a transfer belt and superimposed on the surface of the recording material to form a color image.
[0003]
[Problems to be solved by the invention]
In this apparatus, the transfer belt is in contact with each latent image carrier. For this reason, toner of a certain color on the surface of the latent image carrier used for forming the latent image adheres to the transfer belt, and the toner is conveyed to the surface of the latent image carrier used for forming an image of another color by the transfer belt. , It may adhere to the surface of the carrier. When toner of a color on the surface of the latent image carrier adheres in this way, the toner is transported into a developing device used for developing other colors and mixed into other color toner stored in the developing device. May end up. In this case, the mixed toner is used for toner image formation together with the toner of the color originally used for image formation, and there is a problem that color mixing may occur in the image.
[0004]
However, when the image forming apparatus is operating normally, the amount of toner adhering to the transfer belt from the latent image carrier is negligible, so color mixing often does not cause much problem. However, when a conveyance failure of the recording material occurs in the image forming apparatus, a large amount of toner on the surface of the recording material may adhere to the transfer belt. This is because the latent image carrier on which the toner image is formed and the transfer belt are in contact with each other even though the recording material does not reach the transfer position due to conveyance failure. In this case, a large amount of toner adhering to the transfer belt is transported by the transfer belt and mixed into toner stored in a developing device used for developing other colors, which has a considerable adverse effect on the image. It will be.
[0005]
In particular, in a wet image forming apparatus that uses a two-component developer composed of toner and carrier as a developer, or a one-component developer composed of toner as a developer, the developer as a developer has fluidity and adhesiveness. Therefore, the toner is likely to be mixed into other developing devices, and the image quality is likely to be deteriorated due to the color mixture.
[0006]
In addition, as a specific case where the conveyance failure occurs, not only the case where the recording material is jammed in the conveyance path (so-called jam), but the conveyance is not performed further, but the recording material conveyance and the latent image formation are synchronized. There are cases where deviations occur. In the latter case, although the recording material does not reach the transfer position, or the toner image of the latent image carrier is formed even though the recording material has already passed the transfer position. The transfer belt comes into contact with the toner, and the toner adheres to the transfer belt.
[0007]
Here, it seems that such an adverse effect can be prevented by providing a cleaning device for removing the toner adhering to the transfer belt, and removing the toner adhering to the surface of the transfer belt by this cleaning device. However, the capacity of such a cleaning device is naturally limited. When a large amount of toner adheres to the transfer belt, it is difficult to completely remove the toner from the transfer belt simply by providing a cleaning device. It is difficult to prevent completely.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to use a toner of a certain color, which is apt to be generated in a conventional image forming apparatus when forming a color image, as another color. It is an object of the present invention to provide an image forming apparatus capable of preventing a decrease in image quality due to color mixing caused by mixing with toner of the toner and always forming a color image having a correct hue..
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, an image forming apparatus according to claim 1 includes a plurality of latent image carriers, and latent image forming positions determined for each latent image carrier on the surfaces of the plurality of latent image carriers. A latent image forming means for forming a latent image, a plurality of developing devices for converting the plurality of latent images formed on the plurality of latent image carriers into toner images of different colors, and a recording material as the latent image. A latent image carrier at each transfer position where the transfer belt and the latent image carrier are close to each other; a transfer belt that sequentially conveys the carrier to the carrier; a transfer belt driving unit that rotationally drives the transfer belt; A plurality of transfer devices that transfer the toner images formed on the recording material to the recording material, a recording material detection sensor that detects the recording material being conveyed, and the latent image carrier and the transfer belt abutting each other. Contact and separation means for separating and separatingAndWhen the recording material detection sensor does not detect the recording material at a timing when the recording material detection sensor is to detect the recording material that is being conveyed, the contact-separating unit includes the latent image carrier and the latent image carrier. Control means for separating the transfer beltThe recording material detection sensor is upstream of the transfer position in the latent image carrier positioned upstream in the conveyance direction of the recording material and the moving speed of the surface of the latent image carrier The distance from the transfer position to the sensor becomes longer than the distance multiplied by the time required for the contact / separation means to separate the transfer belt from the latent image carrier after the sensor detects a conveyance failure. It is characterized by being provided in such a position.
  Claims2The image forming apparatus ofA plurality of latent image carriers, latent image forming means for forming latent images on the surfaces of the plurality of latent image carriers at a latent image forming position determined for each latent image carrier; A plurality of developing devices for converting a plurality of latent images formed on the image carrier into toner images of different colors, a transfer belt for sequentially conveying a recording material to each of the latent image carriers, and a rotation of the transfer belt A plurality of transfer belt driving means for driving, a plurality of toner images formed on each of the latent image carriers at a transfer position where the transfer belt and each of the latent image carriers are close to each other. An image forming apparatus comprising: a transfer device; a recording material detection sensor that detects a recording material being conveyed; and a contact / separation unit that contacts and separates each of the latent image carriers and the transfer belt. The recording material detection sensor being conveyed When the recording material is not detected at the timing when the recording material is to be detected, the contact / separation means has a control means for separating the latent image carrier and the transfer belt, and the plurality of latent images Transfer on the latent image carrier for detecting the recording material to start latent image formation by the latent image forming means for the latent image carrier located in the uppermost stream in the conveying direction of the recording material among the carrier. The distance from the transfer position is longer than the distance from the transfer position on the latent image carrier to the latent image formation position on the image carrier, upstream of the transport direction. And a latent image forming sensor provided at a different position, wherein the recording material detection sensor is provided downstream of the latent image forming sensor in the conveying direction of the recording material.
  Claims3The image forming apparatus includes a plurality of latent image carriers and a latent image forming unit that forms latent images on the surfaces of the plurality of latent image carriers at a latent image forming position determined for each latent image carrier. A plurality of developing devices for converting the plurality of latent images formed on the plurality of latent image carriers into toner images of different colors, and a transfer belt for sequentially conveying a recording material to each of the latent image carriers. The toner image formed on each of the latent image carriers is recorded on the transfer belt driving means for rotating the transfer belt, and at each transfer position where the transfer belt and each of the latent image carriers are close to each other. A plurality of transfer devices that transfer to the material; a sensor that detects a conveyance failure of the recording material; and a contact / separation unit that contacts and separates each of the latent image carriers and the transfer belt.AndAn image forming apparatus provided with the sensor provided in a region between the latent image carriers, and when the sensor detects a conveyance failure of the recording material, the contact / separation unit holds the latent image carrier. Control means for separating the body and the transfer belt is provided.
  Claims4The image forming apparatus of claim3The image forming apparatus according to claim 1, wherein the sensor is provided in the immediate vicinity of the latent image carrier positioned upstream in the conveyance direction of the recording material, of both the latent image carriers provided in an area between the sensors. To do.
[0010]
  In the image forming apparatus according to claim 1, when the recording material detection sensor does not detect the recording material at a timing when the recording material should be detected, it is considered that there is a conveyance failure upstream from the sensor, and the control unit Causes the abutment / separation means to separate the latent image carrier from the transfer belt. Therefore, the toner on the transfer belt is caused by the contact between the latent image carrier on which the toner image is formed and the transfer belt even though the recording material does not reach the transfer position due to conveyance failure. Is prevented from sticking. Further, in an image forming apparatus provided with a cleaning device that removes toner adhering to the transfer belt, an excessive burden of forcing the cleaning device to remove toner exceeding its capacity is not imposed.
  further,If the recording material detection sensor does not detect the recording material at the timing when the recording material should be detected, it is assumed that there is a conveyance failure of the recording paper, and the latent image carrier and the transfer belt are separated from each other. Therefore, the toner adheres to the transfer belt due to the latent image carrier on which the toner image is formed and the transfer belt being in contact with each other even though the recording material has not reached the transfer position. Is prevented.
  Here, if the image forming apparatus can immediately separate the transfer belt from the latent image carrier at the moment when the recording material detection sensor detects the conveyance failure of the recording material, the sensor is brought close to the transfer position. Even if it is provided, adhesion of toner to the transfer belt can be prevented. That is, in such a case, when the toner image formed on the image carrier reaches the transfer position to be transferred to the leading end of the recording material that should normally be conveyed normally, the transfer belt carries the latent image. Thus, the toner is prevented from adhering to the transfer belt because it is separated from the body. However, it usually takes a certain time (hereinafter referred to as the separation time) for the contact / separation means to separate the transfer belt from the latent image carrier after the recording material detection sensor detects the conveyance failure. In such a case, if the recording material detection sensor is provided in the immediate vicinity of the transfer position, the portion of the latent image carrier on which the toner image is formed reaches the transfer position while the separation time elapses, and the transfer belt Toner will adhere.
  Therefore, the claim1In this image forming apparatus, the recording material detection sensor is provided at a position separated from the transfer position by a certain distance or more to prevent the toner from adhering to the conveyance belt from the latent image carrier while the separation time elapses. ing. That is, the claim1In the image forming apparatus, the moving speed of the surface of the latent image carrier, which is the distance that the tip of the toner image of the latent image carrier moves while the separation time elapses, is greater than the distance obtained by multiplying the separation time by the moving time. The sensor is provided at a position where the distance from the transfer position to the recording material detection sensor is long, and the transfer belt is separated from the latent image carrier until the leading end reaches the transfer position. . This more reliably prevents toner from adhering to the transfer belt from latent image carrying.
  In addition, the claim concerned2In the image forming apparatus ofWhen the recording material detection sensor does not detect the recording material at the timing when the recording material should be detected, it is assumed that there is a conveyance failure upstream from the sensor, and the control means detects the latent image carrier and the contact / separation means. Separate the transfer belt. Therefore, the toner on the transfer belt is caused by the contact between the latent image carrier on which the toner image is formed and the transfer belt even though the recording material does not reach the transfer position due to conveyance failure. Is prevented from sticking. Further, in an image forming apparatus provided with a cleaning device that removes toner adhering to the transfer belt, an excessive burden of forcing the cleaning device to remove toner exceeding its capacity is not imposed.
further,Even if a recording paper conveyance failure occurs downstream of the latent image forming sensor in the recording material conveyance direction, if the position where the conveyance failure occurs is upstream of the recording material detection sensor, the recording material detection sensor conveys the recording paper. It is detected that there is a defect, and the transfer belt is separated from the latent image carrier, thereby preventing toner from adhering to the transfer belt. As described above, the latent image forming sensor must be provided at a position where the distance from the sensor to the transfer position is longer than the distance from the transfer position to the latent image forming position. Therefore, the latent image forming sensor must be provided at a position having a certain distance from the transfer position, and when only the latent image forming sensor is used, the recording material is transported downstream of the latent image forming sensor. Therefore, it is impossible to prevent the toner from adhering to the transfer belt due to the conveyance failure. Therefore, the claim2In this image forming apparatus, the latent image forming sensor and the recording material detection sensor are used in combination to prevent the toner from adhering to the transfer belt due to the conveyance failure of the recording material that occurs downstream from the latent image forming sensor. -ing
  Here, if the transfer belt is separated from the latent image carrier when a recording material conveyance failure occurs using only the recording material detection sensor, toner adhesion to the transfer belt can be prevented. However, when such a configuration is adopted, even when a conveyance failure occurs upstream from the latent image forming sensor, a latent image is formed on the surface of the latent image carrier, and the latent image is formed to form a toner image. Will be. Therefore, in this case, an excessive burden is imposed on the cleaning device that removes the toner from the surface of the latent image carrier. In contrast, the claims2In this image forming apparatus, when a conveyance failure of the recording material occurs upstream of the latent image forming sensor, the latent image is not formed on the latent image carrier and the toner image is not formed. It does not impose an excessive burden on the device.
  In addition, the claim concerned3In this image forming apparatus, when the sensor detects a conveyance failure of the recording material generated in the region between the latent image carriers, the control unit causes the contact image separating unit to separate the latent image carrier and the transfer belt. Therefore, the toner adhering to the transfer belt, which occurs when the transfer belt is driven to rotate while the transfer belt and the latent image carrier are in contact with each other in spite of the conveyance failure of the recording material, is generated. Can be prevented or reduced.
  In particular the claims concerned4In the image forming apparatus, a sensor is provided in a region between the sensors, in the vicinity of the latent image carrier positioned upstream in the conveyance direction of the recording material, that is, in the conveyance direction of the recording material in the region. In this case, a sensor is provided at a position corresponding to the most upstream portion, and a conveyance failure of the recording material is detected at an earlier timing than in the case where the sensor is provided downstream from the position. Accordingly, the timing of the transfer belt from the latent image carrier based on the detection is also advanced, and the amount of toner attached to the transfer belt can be minimized.
  Claims4In this image forming apparatus, the distance between the sensor and the moving speed of the surface of the latent image carrier is multiplied by the time required for the transfer belt to be separated from the latent image carrier after the sensor detects the conveyance failure. A position where the distance from the transfer position to the sensor in the latent image carrier located downstream in the conveyance direction of the recording material (hereinafter referred to as the downstream latent image carrier) is increased among the latent image carriers provided in the region. If a sensor is provided in the toner, it is possible to prevent toner from adhering to the downstream side latent image carrier.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
Hereinafter, a first embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus will be described. FIG. 1 is a front view showing a schematic configuration of a copying machine according to this embodiment.
[0028]
In this apparatus, as a recording material that is electrostatically adsorbed and conveyed by the transfer belt 1 in the vicinity of a conveyance unit 4 including a transfer belt 1, a driving roller 2 as a transfer belt driving means, a driven roller 3, and the like. A yellow toner image forming unit Y, a magenta toner image forming unit M, a cyan toner image forming unit C, and a black toner image forming unit B that sequentially form toner images on the recording paper 5 are provided.
[0029]
  The configuration of each toner image forming unit Y, M, C, B will be described. FIG. 2 is a front view showing a schematic configuration of the yellow toner image forming portion Y. Since the configurations of the toner image forming units Y, M, C, and B are common, the description is given only for the yellow toner image forming unit Y, and the other toner image forming units are illustrated in FIG. Parts corresponding to those in Y are given M, C, and B after the numbers given to those in the yellow toner image forming unit, and the description thereof is omitted. In order to form a yellow toner image on the surface of the recording paper 5 by an electrophotographic process around the photosensitive drum 30Y as a latent image carrier of the yellow toner image forming portion Y, a charging device 31Y, an exposure device 32Y, and a developing device A device 33Y, a transfer device 34Y, a charge eliminating device 35Y, and a cleaning device 36Y are arranged.Have.
[0030]
Here, the developing device 33Y is a wet developing device that uses a two-component developer composed of toner and carrier or a one-component developer composed of toner as a developer, and supplies the developer to the surface of the photoreceptor drum 30Y. The developing roller 37Y includes a reverse roller 38Y that removes excess developer on the surface of the photosensitive drum 30Y, a developer supply port 40Y that supplies the developer to the case 39Y, and the like. In addition, the transfer device 34Y generates an electric field in such a direction that the recording paper 5 interposed between the photosensitive drum 30Y and the transfer belt 1 electrostatically attracts the toner image formed on the surface of the photosensitive drum 30Y. It consists of a transfer charger that applies a charge to the transfer belt 1 in order to generate it.
[0031]
  A first conveyance guide plate 6 for supplying recording paper 5 as a recording material to a transfer belt 1 from a paper feeding device (not shown) is provided upstream of the yellow toner image forming portion Y in the rotation direction of the transfer belt 1. ing. On the other hand, a separation charge for separating the recording paper 5 from the transfer belt 1 is provided downstream of the black toner image forming portion B in the rotation direction of the transfer belt 1.7Is provided. The separation charger 7 removes the charge from the transfer belt 1 and the recording paper 5 and weakens the electrical adsorption force between the transfer belt 1 and the recording paper 5, thereby separating the recording paper 5 from the surface of the transfer belt 2 by its rigidity. Let Further, a second conveyance guide plate 8 for guiding the recording paper 5 separated from the surface of the transfer belt 1 to a fixing device (not shown) is provided in the vicinity of the separation unit.
[0032]
  Separate charge7A transfer belt cleaning device 10 is provided downstream of the transfer belt 1 in the rotation direction as a cleaning means for removing developer, dust and the like attached to the surface of the transfer belt 1. The transfer belt cleaning device 10 is provided in contact with the transfer belt 1 and rotates in the opposite direction to the transfer belt 1 to remove toner from the surface of the transfer belt 1 by frictional force. As shown by an arrow a, the fan 12 is configured to generate an air flow toward the surface of the blotter roller 11, evaporate the developer attached to the surface of the blotter roller 11, and dry the surface. Note that the surface of the blotter roller 11 is preferably made of synthetic leather having a lubrication property and a rough surface so that the toner can be wiped off. The blotter roller 11 and the fan 12 are driven by a motor (not shown) as a cleaning unit driving unit.
[0033]
In order to detect a conveyance failure of the recording paper 5, a first sensor 50 is provided in the vicinity of the first conveyance guide plate 6, and a second sensor 51 is provided in the vicinity of the second conveyance guide guide plate 8. .
[0034]
In addition, this apparatus includes contact / separation means for bringing the photosensitive drums 30Y, 30M, 30C, and 30B into contact with and separating from the transfer belt 1. The abutting / separating means includes a first arm 61 rotatably provided on the apparatus main body by a shaft 60, a second arm 63 rotatably provided on the apparatus main body by a shaft 62, and both arms 61 and 63. It consists of the link mechanism comprised from the connection member 64 to connect. At the connecting portion between the first arm 61 and the connecting member 64, a first pressing member 65 for pressing the transfer belt 1 in the direction of each of the photosensitive drums 30Y, 30M, 30C, and 30B is provided. The connecting portions are provided with second pressing members 66 for pressing the transfer belt 1 in the directions of the photosensitive drums 30Y, 30M, 30C, and 30B.
[0035]
These pressing members 65 and 66 are separated from the photosensitive drums 30Y, 30M, 30C, and 30B by a spring 67 that is a biasing means provided on the first arm 61 unless a force is applied from the outside. Be energized by. In addition, a solenoid 68 as a drive source for bringing the pressing members 65 and 66 into contact with the photosensitive drums 30Y, 30M, 30C, and 30B against the bias by the spring 67 is provided on the second arm 63. It has been. That is, the contact / separation means is in a state in which the transfer belt 1 and each of the photosensitive drums 30Y, 30M, 30C, and 30B are separated when the solenoid 68 is OFF, and the transfer belt 1 and each of the photosensitive drums 30Y, 30M, 30C, and 30B when the solenoid 68 is ON. The photoconductors 30Y, 30M, 30C, and 30B are in contact with each other.
[0036]
The operation of this apparatus configured as described above will be described separately for normal image formation and when a conveyance failure of the recording paper 5 occurs.
[0037]
First, an operation during normal image formation will be described. In forming an image, first, the solenoid 68 is turned ON so that the transfer belt 1 and each of the photosensitive drums 30Y, 30M, 30C, and 30B are in contact with each other by the first pressing member 65 and the second pressing member 66. . In this state, a sheet feeding device (not shown) supplies the recording paper 5 to the first conveyance guide plate 6, and the first conveyance guide plate 6 conveys the recording paper 5 to the surface of the transfer belt 1. The transfer belt 1 attracts the recording paper 5 conveyed by the first conveyance guide plate 6 to the surface thereof by the electric charge applied by the transfer device 34Y. Here, the transfer belt 1 is rotated in the direction of the arrow b by the rotational force transmitted from the driving roller 2, and the transfer paper 5 is transferred to the respective photosensitive drums 30 </ b> Y provided in the toner image forming portions Y, M, C, and B It is transported at the same speed as the peripheral speed of 30M, 30C, 30B.
[0038]
  On the surface of the photosensitive drum 30Y that rotates at the same speed as the transfer belt 1, each device disposed around the photosensitive drum forms a yellow toner image. That is, the charging device 31Y uniformly charges the surface of the photosensitive drum 30Y, the exposure device 32Y forms an electrostatic latent image on the surface of the photosensitive drum 30Y, and the developing device 33Y supplies yellow toner to the electrostatic latent image. Finally, a yellow toner image is formed. The transfer device 34Y transfers the yellow toner image onto the surface of the recording paper 5 conveyed by the transfer belt 1 to the nip portion NY formed by the transfer belt 1 and the photosensitive drum 30Y. That is, the transfer device 34Y applies a charge to the transfer belt 1 to generate an electric field in the vicinity of the nip portion N, and the yellow toner image on the surface of the photosensitive drum 36Y is electrostatically moved in the direction of the transfer paper 5. Thus, the yellow toner image is transferred onto the transfer paper 5. And the static elimination apparatus 35YIs the photosensitive drum 36YRemove residual charge on the surfaceSet 36Y removes the yellow toner remaining on the surface of the photosensitive drum 36Y.
[0039]
The recording belt 5 having the yellow toner image attached to the surface by the above operation is transferred onto the recording belt 5 by the transfer belt 1 and the nip portion NM formed by the transfer belt 1 and the magenta toner image forming portion M, and the transfer belt 1 and the cyan toner image. The sheet is sequentially conveyed to the nip NC formed by the forming portion C and the nip NB formed by the transfer belt 1 and the black toner image forming portion B. In the nip portion NM, the magenta toner image forming portion M forms a magenta toner image, in the nip portion NC, the cyan toner image forming portion forms a cyan toner image, and in the nip portion NB, the black toner image forming portion B forms a black toner image. Are sequentially transferred onto the transfer paper 5 and the toner images are superimposed on the surface of the transfer paper 5. The operation of forming the toner image by each of the toner image forming units M, C, and B and the operation of transferring the toner image to the recording paper 5 are the same as the operation of the yellow toner image forming unit Y.
[0040]
  With the above operation, the recording paper 5 in which the four color toner images are superimposed is separated.Charger7 separates from the surface of the transfer belt 1. Ie separationCharger7 removes a part of the charges electrostatically adsorbing the recording paper 5 distributed on the transfer belt 1 and weakens the electrostatic attraction between the transfer belt 1 and the recording paper 5. The recording paper is separated from the surface of the transfer belt 1 due to the weakness of the electrostatic adsorption force and the rigidity of the recording paper 5. Then, the recording paper 5 separated from the surface of the transfer belt 1 is conveyed to a fixing device (not shown) by the second conveyance guide plate 8, and the fixing device fixes the toner image on the recording paper. The recording paper 5 that has been fixed is discharged to the outside of the apparatus by a mechanism (not shown).
[0041]
  When the above copying operation is completed, the solenoid 68 is turned off, the first pressing member 65 and the second pressing member 66 are separated from the transfer belt 1 by the spring 67, and the transfer belt 1 and the photosensitive drums 30Y, 30M, 30C and 30B are separated. Further, in this state, the transfer belt 1 is rotated by the driving roller 2, and the blotter roller 11 and the fan 12 are rotated by a motor (not shown), thereby removing the toner adhering to the surface of the transfer belt 1. As described above, after the copying operation is completed, the transfer belt 1 is separated from each of the photosensitive drums 30Y, 30M, 30C, and 30B, so that the toner remaining on the surface of the photosensitive drum is prevented from adhering to the transfer belt. Can do. That is, if the transfer belt 1 and the photosensitive drum are brought into contact with each other when the copying operation is completed, the toner on the surface of the photosensitive drum flows down along the surface of the photosensitive drum and adheres to the surface of the transfer belt 1. become. For example, in this embodiment, the transfer belt 1 is stretched between the driven roller 3 and the drive roller 2, and the respective photosensitive drums 30Y, 30M, 30C, and 30B are provided in the vicinity of the lateral direction.NoTherefore, toner in a region (A region in FIG. 2) from the uppermost end of each photosensitive drum to a position closest to the transfer belt 1 flows down along the surface of the photosensitive drum and adheres to the transfer belt. turn into. So, to avoid such a situation, copyActionWhen completed, the transfer belt 1 is operated to be separated from the photosensitive drums 30Y, 30M, 30C, and 30B as described above.
[0042]
Further, as described above, when the copying operation is completed, that is, when the image forming operation is completed, the toner attached to the surface of the transfer belt 1 is removed by the transfer belt cleaning device 10, so that it adheres to the surface of the transfer belt 1 when the copying is completed. The toner that has been mixed into the developing devices of other colors at the next copying does not cause color mixing and deteriorate image quality.
[0043]
Since the solenoid 68 is not turned on until the next copy is made, the transfer belt 1 and the photosensitive drums 30Y, 30M, 30C, and 30B are kept separated until the next copy is made. Will be. Therefore, it is possible to prevent the toner remaining on the surface of the photosensitive drum from adhering to the transfer belt before the next copy is made.
[0044]
Next, an operation when a conveyance failure of the recording paper 5 occurs will be described. When the first sensor 50 or the second sensor 51 detects that the conveyance failure of the recording paper 5 has occurred, the control means (not shown) turns off the solenoid 68 and the transfer belt 1 and the photosensitive drums 30Y and 30M. , 30C, 30B are separated. In this state, the transfer belt 1 is rotated by the driving roller 2, and the blotter roller 11 and the fan 12 are rotated by a motor (not shown) to remove the toner on the surface of the transfer belt. As described above, when the conveyance failure of the recording paper 5 occurs, the transfer belt 1 and the photosensitive drums 30Y, 30M, 30C, and 30B are separated from each other. In addition, it is possible to prevent a large amount of toner from adhering to the transfer belt 1 when the transfer belt 1 is rotated while the photosensitive drums 30Y, 30M, 30C, and 30B are in contact with each other.
[0045]
Even if the transfer belt 1 and the photosensitive drums 30Y, 30M, 30C, and 30B are separated from each other, some toner may adhere to the transfer belt 1 when the conveyance is poor. Also in this case, as described above, the drive roller2, The transfer belt 1 is rotated, and the blotter roller 11 and the fan 12 are rotated by a motor (not shown).RemovalLeft.
[0046]
When the first sensor 50 or the second sensor 51 detects a conveyance failure of the recording paper 5, it is desirable to operate the separation charger 7 in combination with the above operation. When the separation charger 7 is operated, the recording paper 5 in the copying machine is conveyed to the vicinity of the separation charger 7 by the rotation of the transfer belt 1, separated from the transfer belt 1 by the separation charger 7, and discharged outside the copying machine. Therefore, the trouble of removing the recording paper 5 in the copying machine from the copying machine can be saved.
[0047]
[Embodiment 2]
Hereinafter, the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus.2The embodiment will be described. The present embodiment is the same as the first embodiment except that various sensors are added to the first embodiment, and thus the description of the configuration and operation of the common parts is omitted. Figure3FIG. 1 is a front view showing a schematic configuration of a copier according to this embodiment.4FIG. 3 is an explanatory view showing a main part of the copying machine. Figure3And figure4In FIG. 4, illustration of some members is omitted.
[0048]
Figure3And figure4As shown in FIG. 3, the copying machine is a sensor for forming a latent image at a position upstream of the transfer position C of the photosensitive drum 30Y that is the photosensitive drum positioned at the most upstream in the conveyance direction of the recording paper 5. 100 (hereinafter referred to as sensor 100) is provided. The sensor 100 is provided to determine the timing for starting the formation of electrostatic latent images by the exposure devices 32Y, 32M, 32C, and 32B for the photosensitive drums 30Y, 30M, 30C, and 30B. That is, when a latent image formation on the photosensitive drum 30Y by the exposure device 32Y is described as an example, when the leading edge of the recording paper reaches the transfer position C based on the detection of the recording paper 5 by the sensor 100, Formation of an electrostatic latent image by the exposure device 30Y is started so that the toner image to be transferred to the leading end of the photosensitive drum 30Y reaches the transfer position C. Similarly, latent images are formed on the photosensitive drums 30M, 30C, and 30B by the exposure devices 32M, 32C, and 32B.
[0049]
Thereby, when the sensor 100 does not detect the recording paper 5, that is, when the jamming of the recording paper 100 occurs upstream of the sensor 100, a toner image is formed on each of the photosensitive drums 30Y, 30M, 30C, and 30B. It will not be done. Therefore, even though the recording paper 5 is not conveyed, the portions where the respective photosensitive drums 30Y, 30M, 30C, and 30B toner images are formed reach the respective transfer positions, and the toner adheres to the transfer belt 1. This situation is avoided.
[0050]
Also figure4As shown in FIG. 4, when the exposure apparatus 32Y defines a latent image forming position where an electrostatic latent image is formed on the photosensitive drum 30Y as B, and the position where the sensor 100 is provided as a position D, the sensor 100 detects the transfer position C and the latent image. The distance between the transfer position C and the position D along the transfer belt 1 is longer than the arc length BC formed on the surface of the photosensitive drum 30Y with the image forming position B. Then, the formation of a latent image by the exposure device 32Y is started when the recording paper 1 reaches the position F, which is the position of the length BC in the conveyance direction of the recording paper 1 from the transfer position C. As a result, when the leading end portion of the toner image formed on the photosensitive drum 30Y reaches the transfer position C, a situation may occur in which the leading end portion of the recording paper 5 has already passed the transfer position C. Disappear.
[0051]
  The copying machine also includes a recording material detection sensor 101 (hereinafter referred to as sensor 101) that detects the recording paper 5 being conveyed by the transfer belt 1. The sensor 101 is used to control the driving of the contact / separation means including the first pressing member 65, the second pressing member 66, and the like. That is, if the sensor 101 is not detected at the timing when the recording paper 5 should be detected, the conveyance failure of the recording paper 5 has occurred upstream of the sensor 101.WhenAccordingly, the transfer belt 1 is separated from each of the photosensitive drums 30Y, 30M, 30C, and 30B. This prevents toner from adhering to the transfer belt 1 from each photosensitive drum due to a conveyance failure of the recording paper 1.
[0052]
Further, the sensor 101 is upstream in the transfer position C of the photosensitive drum 30Y, which is the photosensitive drum positioned at the most upstream in the conveyance direction of the recording paper 5, and the line of the photosensitive drum 30Y. The distance from the sensor 101 to the transfer position C becomes longer than the distance multiplied by the time required for the contact / separation means to separate the transfer belt 1 from the photosensitive drum after the sensor 101 detects the conveyance failure at a high speed. It is provided in such a position. As a result, when a conveyance failure of the recording paper 5 occurs, the transfer belt 1 is separated from the photosensitive drum 30Y before the leading end of the toner image formed on the photosensitive drum 30Y reaches the transfer position C. Thus, toner adhesion to the transfer belt 1 is prevented.
[0053]
  Further, in this copying machine, as shown in FIG. 4, a sensor 101 is provided downstream of the sensor 100 in the conveyance direction of the recording paper 5. Therefore, the sensor-Even when the conveyance failure of the recording paper 5 occurs at a position downstream of 100, if the position is upstream of the sensor 101, the transfer belt 1 is separated from the photosensitive drum 30Y.
[0054]
[Embodiment3]
Hereinafter, the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus.3The embodiment will be described. In the present embodiment, the first2Embodiment except that a new sensor is added to the embodiment2Therefore, the description of the configuration and operation of the common part is omitted. Figure5FIG. 1 is a front view showing a schematic configuration of a copying machine according to this embodiment. Figure5In FIG. 4, illustration of some members is omitted.
[0055]
  As shown in FIG.bodyAn area between the drums, that is, an area between the photosensitive drum 30Y and the photosensitive drum 30M, an area between the photosensitive drum 30M and the photosensitive drum 30C, and the photosensitive drum 30C and the photosensitive drum 30B. A sensor 102 is provided in each of the areas in order to detect a conveyance failure of the recording paper 5. When any of these sensors 102 detects that a conveyance failure has occurred in the recording paper 5, the contact / separation means including the first pressing member 65, the second pressing member 66, etc. is activated, and the transfer belt 1 is The photosensitive drums 30Y, 30M, 30C, and 30B are separated from each other. As a result, it is possible to prevent the toner from adhering to the transfer belt 1 from each photosensitive drum due to poor conveyance of the recording paper 1 in the area between the photosensitive members.
[0056]
Each of these sensors 102 is provided in the immediate vicinity of the photosensitive drum on the upstream side in the conveyance direction of the recording paper 5. Therefore, it is possible to detect the conveyance failure of the recording paper 5 at an earlier timing as compared with the case where the sensor 102 is provided downstream of the position, and thereby the photosensitive drums 30Y and 30M of the transfer belt 1 are detected. , 30C and 30B are also separated at an early timing..
【The invention's effect】
[0057]
  As described above, when the recording material is transported well, the control unit causes the latent image forming unit to start forming a latent image on the latent image carrier, and the latent image forming sensor does not detect the recording material. That is, when a conveyance failure of the recording material occurs, formation of a latent image on the latent image carrier is not started. ThisWhen the recording material is poorly conveyed, the latent image is not formed on the latent image carrier, and the latent image carrier on which the toner image is formed is brought into contact with the transfer belt. This prevents the toner from adhering to the transfer belt. Therefore, the toner adhering to the transfer belt is not mixed with other color toners, and the image quality is not deteriorated due to the mixing.
[0058]
  Also,For latent image formationBased on the signal from the sensor, when the distance between the leading edge of the recording paper and the transfer position becomes equal to the distance between the latent image formation position and the transfer position on the most upstream latent image carrier, the latent image forming means performs latent image formation. By starting the image formation, the toner image can be satisfactorily transferred from the leading end portion of the recording material, and a good image can be formed.
[0059]
  further,RecordEven though the rear end of the recording material has already passed the transfer portion, the toner image transfer operation is not performed at the transfer position. Therefore, the toner is prevented from adhering to the transfer belt, and the image quality is not deteriorated due to the toner adhering to the transfer belt being mixed into other color toners.
[0060]
  According to the first aspect of the present invention, when the recording material detection sensor does not detect the recording material at the timing when the recording material should be detected, the latent image carrier is separated from the transfer belt, and the transfer at the time of the conveyance failure is performed. Since the toner is prevented from adhering to the belt, the toner adhering to the transfer belt is not mixed with other color toners, and the image quality is not deteriorated due to the mixing. In addition, when the present invention is applied to an image forming apparatus provided with a cleaning device that removes toner adhering to the transfer belt, an excessive burden of forcing the cleaning device to remove toner exceeding its capacity is not imposed. .
Further, the leading end portion of the toner image on the latent image carrier passes while the time from the detection of the conveyance failure by the recording material detection sensor to the separation of the transfer belt from the latent image carrier (hereinafter referred to as the separation time) elapses. The sensor is provided at a position where the distance from the transfer position to the recording material detection sensor is longer than the distance obtained by multiplying the moving speed of the surface of the latent image carrier, which is the moving distance, by the separation time. Until the transfer position reaches the transfer position, the transfer belt is separated from the latent image carrier. This more reliably prevents the toner from adhering to the transfer belt from the latent image carrier, and the toner adhering to the transfer belt is mixed into other color toners, resulting in a decrease in image quality due to this mixing. Is more reliably prevented.
[0062]
  Claim2According to the invention ofWhen the recording material detection sensor does not detect the recording material at the timing when the recording material should be detected, the latent image carrier is separated from the transfer belt, and toner adhesion to the transfer belt at the time of the conveyance failure is prevented. The toner adhering to the transfer belt is not mixed with other color toners, and the image quality is not deteriorated due to the mixing. Further, when the present invention is applied to an image forming apparatus provided with a cleaning device that removes toner adhering to the transfer belt, an excessive burden of forcing the cleaning device to remove toner exceeding its capacity is not imposed. .
further,Even if a recording paper conveyance failure occurs downstream of the latent image forming sensor in the recording material conveyance direction, if the position where the conveyance failure occurs is upstream of the recording material detection sensor, the recording material detection sensor conveys the recording paper. It is detected that there is a defect, and the transfer belt is separated from the latent image carrier, thereby preventing toner from adhering to the transfer belt. Therefore, even if a recording material conveyance failure occurs at such a position, toner adhesion to the transfer belt is prevented, and the toner adhering to the transfer belt is mixed into toner of other colors, resulting from this mixing. A reduction in image quality can be prevented more reliably.
[0063]
  Claims2According to the invention, even when a conveyance failure occurs upstream of the latent image forming sensor as in the case of preventing toner adhesion to the conveyance belt using only the recording material detection sensor, the latent image carrier is provided. A situation in which a toner image is formed on the surface of the latent image carrier is avoided, and an excessive burden is not imposed on the cleaning device that removes the toner from the surface of the latent image carrier.
[0064]
  Claim3According to this invention, when the sensor detects a conveyance failure of the recording material generated in the area between the latent image carriers, the transfer belt and the latent image carrier are separated from each other. Therefore, a large amount of toner is prevented or reduced from adhering to the transfer belt, and deterioration in image quality due to the toner adhering to the transfer belt mixed into other color toners is prevented or reduced. The degree is reduced.
[0065]
  Claim4According to the invention, since the sensor is provided in the immediate vicinity of the latent image carrier positioned upstream in the conveyance direction of the recording material among the latent image carriers provided in the area between the sensors, the sensor is provided downstream of this position. Compared to the case where the transfer belt is provided, the timing at which the transfer belt is separated from the latent image carrier is also earlier, and the amount of toner adhering to the transfer belt can be minimized. As a result, the degree of deterioration in image quality due to the toner adhering to the transfer belt being mixed into other color toners is further reduced.
[Brief description of the drawings]
FIG. 1 is a front view illustrating a schematic configuration of a copying machine according to a first embodiment.
FIG. 2 is a front view showing a yellow toner image forming unit of the copier.
[Fig. 3]FIG. 6 is a front view illustrating a schematic configuration of a copier according to a second embodiment.
[Fig. 4]FIG. 3 is an explanatory diagram showing a main part of the copier.
[Figure 5]FIG. 9 is a front view illustrating a schematic configuration of a copying machine according to a third embodiment.
[Explanation of symbols]
1 Transfer belt
2 Drive roller
3 Followed roller
4 Transport unit
5 Recording paper (recording material)
6 First transport guide plate
7 Separate charger
8 Second transport guide plate
10 Transfer belt cleaning device
11 Blotter roller
12 fans
30 Photosensitive drum (latent image carrier)
31 Charging device
32 Exposure equipment
33 Developer
34 Transfer device
35 Static eliminator
36 Cleaning device
37 Development roller
38 Reverse Roller
39 cases
40 Developer supply port
50 First sensor
51 Second sensor
60 axes
61 First arm
62 axes
63 Second arm
64 connecting members
65 First pressing member
66 Second pressing member
67 Spring
68 SolenoiDo
100 Sensor for latent image formation
101 Recording material detection sensor
102 sensors
Y Yellow toner image forming part
M Magenta toner image forming section
C Cyan toner image forming unit
B Black toner image forming part

Claims (4)

A plurality of latent image carriers;
Latent image forming means for forming a latent image on the surface of the plurality of latent image carriers at a latent image forming position determined for each latent image carrier;
A plurality of developing devices for forming the plurality of latent images formed on the plurality of latent image carriers, respectively, with toner images of different colors;
A transfer belt for sequentially conveying the recording material to each of the latent image carriers;
Transfer belt driving means for rotating the transfer belt;
A plurality of transfer devices for transferring a toner image formed on each of the latent image carriers to the recording material at each transfer position where the transfer belt and each of the latent image carriers are close to each other;
A recording material detection sensor for detecting the recording material being conveyed;
An image forming apparatus provided with a contact / separation means for contacting and separating each of the latent image carriers and the transfer belt,
Control means for separating the latent image carrier and the transfer belt from the contact / separation means when the recording material detection sensor does not detect the recording material at a timing to detect the recording material being conveyed. have a,
The recording material detection sensor is
Upstream of the transfer position in the latent image carrier located in the uppermost stream in the conveyance direction of the recording material,
And,
More than the distance obtained by multiplying the moving speed of the surface of the latent image carrier by the time required for the contact / separation means to separate the transfer belt from the latent image carrier after the sensor detects a conveyance failure. An image forming apparatus provided at a position where a distance to a transfer position is long . A plurality of latent image carriers;
Latent image forming means for forming a latent image on the surface of the plurality of latent image carriers at a latent image forming position determined for each latent image carrier;
A plurality of developing devices for forming the plurality of latent images formed on the plurality of latent image carriers, respectively, with toner images of different colors;
A transfer belt for sequentially conveying the recording material to each of the latent image carriers;
Transfer belt driving means for rotating the transfer belt;
A plurality of transfer devices for transferring a toner image formed on each of the latent image carriers to the recording material at each transfer position where the transfer belt and each of the latent image carriers are close to each other;
A recording material detection sensor for detecting the recording material being conveyed;
An image forming apparatus provided with a contact / separation means for contacting and separating each of the latent image carriers and the transfer belt,
Control means for separating the latent image carrier and the transfer belt from the contact / separation means when the recording material detection sensor does not detect the recording material at a timing to detect the recording material being conveyed. Have
Detecting the recording material in order to start latent image formation by the latent image forming means for the latent image carrier positioned upstream in the transport direction of the recording material among the plurality of latent image carriers. More upstream from the transfer position than the transfer position on the image carrier, and more than the distance from the transfer position on the latent image carrier to the latent image formation position on the image carrier. It has a latent image forming sensor provided at a position where the distance becomes long,
An image forming apparatus, wherein the recording material detection sensor is provided downstream of the latent image forming sensor in the conveyance direction of the recording material. A plurality of latent image carriers;
Latent image forming means for forming a latent image on the surface of the plurality of latent image carriers at a latent image forming position determined for each latent image carrier;
A plurality of developing devices for forming the plurality of latent images formed on the plurality of latent image carriers, respectively, with toner images of different colors;
A transfer belt for sequentially conveying the recording material to each of the latent image carriers;
Transfer belt driving means for rotating the transfer belt;
A plurality of transfer devices for transferring a toner image formed on each of the latent image carriers to the recording material at each transfer position where the transfer belt and each of the latent image carriers are close to each other; A sensor that detects a conveyance failure;
An image forming apparatus provided with a contact / separation means for contacting and separating each of the latent image carriers and the transfer belt,
Providing the sensor in a region between the latent image carriers,
And,
An image forming apparatus comprising: a control unit configured to separate the latent image carrier and the transfer belt from the contact / separation unit when the sensor detects a conveyance failure of the recording material. 4. The image forming apparatus according to claim 3 , wherein the sensor is provided in the immediate vicinity of the latent image carrier positioned upstream in the conveyance direction of the recording material among the latent image carriers provided in the area between them. An image forming apparatus.

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