JP3575729B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a copying machine, a laser printer, and other image forming apparatuses that employ an electrophotographic system, an electrostatic recording system, or the like, and in particular, after an image formed on an image carrier is once transferred to an intermediate transfer belt. The present invention relates to an improvement in an image forming apparatus of a type that performs batch transfer to a recording material.
[0002]
[Prior art]
Conventionally, as an intermediate transfer type image forming apparatus of this type, a primary transfer of each color component toner image formed on a photoreceptor or the like is sequentially performed on an intermediate transfer belt, and a multicolor toner image on the intermediate transfer belt is transferred to a secondary transfer device ( A batch transfer device is known (see Japanese Patent Application Laid-Open No. 2-213879).
In this type of image forming apparatus, a secondary transfer device includes a transfer roll pressed against the front side of the intermediate transfer belt, and a transfer roll of the intermediate transfer belt on the back side of the intermediate transfer belt facing the transfer roll. Is provided, and by forming a transfer electric field between the transfer roll and the backup roll, the multicolor toner image on the intermediate transfer belt is collectively transferred to the paper side.
Then, the collectively transferred sheets are separated by a sheet guide disposed immediately after the secondary transfer device, and the transport direction is controlled, so that the sheet is transported by a transport belt or the like disposed downstream of the secondary transfer device. A method is usually adopted in which the sheet is guided to a device and then sent to a fixing device.
Here, as a sheet transport device disposed downstream of the secondary transfer device, for example, a method of transporting a sheet on which an unfixed toner image has been loaded, in which a belt is conveyed by suction and suction by a fan, is well known. (See, for example, JP-A-3-293253).
[0003]
[Problems to be solved by the invention]
However, in the conventional image forming apparatus of this type, there is a technical problem in that a peeling failure of a sheet as a recording material from the intermediate transfer belt and a transport failure of the sheet after the peeling are likely to occur.
First, the sheet peeling failure will be described. The sheet as the recording material is charged because it passes through the nip area between the transfer roll and the intermediate transfer belt, and is easily attracted to the intermediate transfer belt side. For this reason, even if the leading edge of the sheet is peeled off from the intermediate transfer belt, the state of conveyance of the sheet after the nip area is, depending on the type of sheet, adsorbed on the intermediate transfer belt again without following the sheet guide. Is easy to occur.
In recent years, the frequency of use of special papers such as coated papers having a coating layer applied to the paper surface has increased, and with these special papers, the releasability tends to be further deteriorated, and the paper can be peeled from the intermediate transfer belt. However, there is a technical problem that troubles such as paper jams are more likely to occur.
[0004]
Further, there is a method of using a peeling claw as a peeling device when peeling a sheet from the intermediate transfer belt. However, when this peeling claw is used, the intermediate transfer belt as an image carrier is easily damaged, and the image quality is deteriorated. The technical problem of influencing is likely to occur.
Furthermore, there is a method of providing a peeling corotron after the secondary transfer. However, the peeling performance is not stable depending on the environment or paper, and further, as shown in JP-A-2-213879, the conductor is peeled near the transfer portion discharge side.plateHowever, it is difficult to stably obtain the electrostatic force that contributes to the separation of the paper, and the peelability of the paper from the intermediate transfer belt varies depending on the type of the paper.
[0005]
In a low-humidity environment, even if the paper can be peeled off, the paper is attracted to the paper guide that controls the transport direction of the paper, so that the paper is easily caught and the paper can be peeled and transported stably. Can not.
[0006]
Next, a description will be given of the sheet conveyance failure. For example, in a suction belt conveyance system using suction of a fan as disclosed in Japanese Patent Application Laid-Open No. 3-293253, the sheet suction by the fan is sufficiently performed as in the case of sheet separation. It is difficult to control the behavior of the paper in the non-existent area, and it is not possible to suppress the peeling failure immediately after the transfer of the paper. Also, depending on the type and thickness of the paper, the required fan suction force is different, and it is difficult to keep the paper conveyance posture constant, and complicated control such as appropriately changing the suction area with a shutter or the like is required. You will need it.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above technical problems, and always maintains good releasability of a recording material from an intermediate transfer belt, and stabilizes conveyance of the recording material to a fixing device. It is an object of the present invention to provide an image forming apparatus capable of performing the above.
[0008]
[Means for Solving the Problems]
That is, as shown in FIG. 1, the basic configuration of the present invention is such that one or a plurality of image carriers 1 on which each color component image is formed and carried, and each color component image on the image carrier 1 is transferred intermediately. In an image forming apparatus including an intermediate transfer belt 2 carried thereon and a collective transfer device 3 for collectively transferring each color component image on the intermediate transfer belt 2 to a recording material 4, a plurality of collective transfer devices 3 are used. The rolls 5a and 5b and the volume resistivity 10 rotatably stretched around the rolls 5a and 5b⁶-10^TenΩcm semi-conductive belt 6, and a roll (5 a) of the plurality of rolls 5 a, 5 b positioned on the upstream side in the transport direction of the recording material (4) is stretched as a transfer roll 7 via a belt 6. A backup member 8 is disposed on the back side of the intermediate transfer belt 2 facing the transfer roller 7 while being pressed against the intermediate transfer belt 2, and a transfer electric field for batch transfer is formed between the transfer roller 7 and the backup member 8. Transfer bias applying means 9 to be provided,Grounding at least one of the plurality of rolls (5a, 5b),The recording material conveying surface (6a) of the belt (6) is provided only on the downstream side of the transfer roll (7) in the conveying direction of the recording material (4).
[0009]
In such a technical means, as an image forming method of the image forming apparatus which is an object of the present application, an electrophotographic method, an electrostatic recording method or the like may be appropriately selected, and in order to form each color component image, One image carrier 1 may be used, or a plurality of image carriers 1 may be used.
[0010]
Further, in the batch transfer device 3, although two rolls 5a and 5b are shown in FIG. 1, the present invention is not limited to this mode, and three or more rolls 5a, 5b. You can place them. Further, the belt 6 may be any belt as long as it is stretched over the rolls 5a and 5b, and is not necessarily one, and may be divided into a plurality of belts. Further, the recording material conveying surface 6a of the belt 6 does not necessarily have to be linear, but may be bent.
The volume resistivity of the belt 6 is such that the charged charges can be retained to the extent necessary for electrostatically adsorbing the recording material 4 and the charged charges can be removed after a predetermined time has passed without providing a charge removing device. , 10⁶-10¹⁰Ωcm is selected.
[0011]
Further, the backup member 8 of the collective transfer device 3 is disposed on the back side of the intermediate transfer belt 2 so as to face the transfer roll 7 and can movably hold the intermediate transfer belt 2 with the transfer roll 7. Any form may be used, regardless of whether it is movable or fixed, and the form is not limited to a roll shape, but may be a plate shape or a block shape as appropriate, but the moving operation of the intermediate transfer belt 2 is not impaired as much as possible. From the viewpoint, it is preferable to reduce the contact area with the intermediate transfer belt 2, and under this requirement, it is preferable that at least the facing surface side of the transfer roll 7 has a curved surface shape. From the viewpoint of reducing the number of components, it is preferable that the backup member 8 also serves as one of the transfer rolls of the intermediate transfer belt 2.
[0012]
Furthermore, for the type in which the intermediate transfer belt 2 rotates once to form a color image, the transfer roll 7 may be kept in contact with the intermediate transfer belt 2 at all times. For the type in which the intermediate transfer belt 2 rotates a plurality of times, the transfer roll 7 is separated from the intermediate transfer belt 2 until the image before the final color image passes, from the viewpoint of not damaging the image on the intermediate transfer belt 2. Is preferred.
[0013]
As for the transfer bias applying means 9, if a transfer bias is applied between the transfer roll 7 and the backup member 8, the transfer bias is applied to either the transfer roll 7 or the backup member 8, and the other is grounded. Alternatively, transfer biases having different polarities may be applied to each other.
[0014]
Regarding the hardness relationship between the backup member 8 and the transfer roll 7, if both have high hardness, the transfer nip area constituted by the backup member 8, the intermediate transfer belt 2, and the transfer roll 7 will not transfer. In order to secure a predetermined nip width, the nip load per unit area increases, and the color material (for example, toner) at the center of the image aggregates in the transfer nip area, so that the transfer may occur. The image cannot be left on the intermediate transfer belt 2 and an image quality trouble at the central portion of the image called a holographic character occurs.
Therefore, from the viewpoint of effectively avoiding the holographic character described above, at least either the backup member 8 or the transfer roll 7 is made to have low hardness, the nip width of the transfer nip area is widened, and the nip load per unit area is reduced. It is preferable to make it.
In particular, in a mode in which a roll that stretches the intermediate transfer belt 2 is also used as the backup member 8, a relatively hard roll is used as the roll that stretches the intermediate transfer belt 2 in order to suppress fluctuations in the rotation speed of the intermediate transfer belt 2. , And it is necessary to use a hard roll for the backup member (backup roll) 8. Therefore, in this embodiment, it is preferable that the hardness of the transfer roll 7 is set lower than that of the backup member 8..
Further, by forming a transfer nip area between the transfer roll 7 and the backup member 8 that cuts into the transfer roll 7, peeling of the recording material from the intermediate transfer belt 2 along the elastic deformation trajectory of the transfer roll 7. This is preferable in that the properties can be kept good.
[0015]
The layout of the recording material transport surface 6a of the belt 6 of the collective transfer device 3 may be appropriately selected, but the recording material transport surface 6a of the belt 6 is located at a position close to the intermediate transfer belt 2 and the backup member 8. Immediately after the transfer nip portion, transfer of a coloring material (for example, toner) due to peeling discharge occurs, and image unevenness occurs.
Therefore, from the viewpoint of effectively avoiding image quality deterioration (image unevenness due to retransfer) due to peeling discharge, the recording material conveying surface 6a of the belt 6 of the collective transfer device 3 includes the central axis of the transfer roll 7 and the backup member 8 Among the perpendiculars perpendicular to the axis center line connecting the center of curvature of the transfer roller 7 and the backup member 8, it is preferable to be disposed at least below a reference line passing through the transfer nip area exit of the transfer roll 7 and the backup member 8.
However, if the recording material transport surface 6a of the belt 6 of the batch transfer device 3 is disposed at an extremely large angle below the reference line, the rate of occurrence of defective peeling of the recording material 4 increases. It is preferable that the recording material conveying surface 6a of the belt 6 of the collective transfer device 3 be disposed below the reference line in a range of 0 ° to 15 °, for example, in a range that does not lead to the separation failure of the recording material 4.
[0016]
Further, as a prior art similar to the invention of the present application, for example, Japanese Patent Application Laid-Open No. 8-106219 discloses a transfer / transportation of a medium-resistance element which is detachably opposed to a flat portion of an intermediate transfer belt having a transfer / transport function. A system with a belt is also known.
However, in this method, since the transfer is performed by the belt-to-belt contact surface in the flat portion of the intermediate transfer belt and the transfer conveyance belt, not only is the influence of the meandering of both belts, but also image quality defects such as image shift occur. When a high-resistance recording material is conveyed, discharge occurs before transfer in a minute area near the belt-to-belt contact surface, causing image omission, and further, immediately after the transfer nip area to prevent peeling failure. There is a technical problem that a static elimination device such as a peeling corotron is required near the transfer conveyance belt.
On the other hand, in the present invention, since the transfer nip area is formed between the transfer roll 7 and the backup member 8 by using the semiconductive belt 6, the belt is hardly affected by meandering between the belts. In addition, there is no need to use a static elimination device in order to prevent image omission due to discharge before transfer or defective peeling.
Therefore, the present invention is completely irrelevant to the prior art described in JP-A-8-106219.
[0017]
Next, the operation of the above technical means will be described.
In FIG. 1, each color component image formed on one or a plurality of image carriers 1 is sequentially transferred to an intermediate transfer belt 2 and conveyed to a collective transfer portion.
A collective transfer device 3 is provided at the collective transfer portion, and a transfer bias is applied to a transfer roll 7 and a backup member 8 of the collective transfer device 3 by transfer bias applying means 9 to form a predetermined transfer electric field. Therefore, the multicolor image on the intermediate transfer belt 2 is collectively transferred to the recording material 4 side in a transfer nip area between the intermediate transfer belt 2 and the semiconductive belt 6.
At this time, since an electrostatic attraction force for adsorbing and holding the recording material 4 is generated on the semiconductive belt 6 by the action of the transfer electric field, the recording material 4 is surely separated from the intermediate transfer belt 2 and then transferred to the semiconductive belt 6. The recording material 4 is guided along the downstream side in the conveyance direction while being stably held by the flexible belt 6.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
◎ Embodiment 1
FIG. 2 is an overall configuration diagram of a color image forming apparatus (for example, a color copying apparatus) to which the present invention is applied.
Note that the present invention is not limited to such an image forming apparatus, and it is needless to say that the present invention can be applied to a monochrome image forming apparatus and the like.
In FIG. 2, an image forming apparatus includes a document reading device 10 that reads a document 12 on a platen 11 and, for example, four color components (black, yellow, magenta, and cyan in this embodiment) image (toner Image forming units 20 (20a to 20d) for forming images, an intermediate transfer belt 30 for sequentially transferring (primary transfer) each color component image formed by each image forming unit 20, and holding the intermediate transfer belt 30 on the intermediate transfer belt 30. A batch transfer device 50 for batch-transferring (secondary transfer) the transferred superimposed image onto a sheet (recording material) 100; a fixing device 70 for fixing the batch-transferred image onto the sheet 100; And a paper transport system 80 for supplying the same.
[0019]
In the present embodiment, the document reading device 10 includes, for example, a light source 13 that is disposed below the platen 11 and irradiates light to the surface of the document 12 and a CCD or the like that converts reflected light from the surface of the document 12 into an electric signal. The photoelectric conversion element 14, an appropriate number of mirrors 15 that form a path for guiding the reflected light from the original 12 to the photoelectric conversion element 14, and the reflected light from the original 12 on the imaging surface of the photoelectric conversion element 14. And an imaging lens 16 for imaging.
[0020]
Each of the image forming units 20 (20a to 20d) has a photosensitive drum 21. A charging device 22, such as a corotron, to which the photosensitive drum 21 is charged is provided around each of the photosensitive drums 21. A laser scanning device in which an electrostatic latent image (mainly an electrostatic latent image based on image data read by the photoelectric conversion element 14 or image data captured from another recording medium) is written on the photosensitive drum 21 Exposure device 23, developing device 24 in which the electrostatic latent image written on photoconductor drum 21 is developed with each color component toner, transfer roll for transferring the toner image on photoconductor drum 21 to intermediate transfer belt 30 And a drum cleaner 26 for removing residual toner on the photosensitive drum 21.
[0021]
Further, the intermediate transfer belt 30 is made of, for example, kneaded vinyl chloride or polyimide with carbon, and has a volume resistivity of 10%.⁹-10¹²It is formed of a film-shaped endless belt of about Ωcm, and is stretched over a plurality of (four in the present embodiment) support rolls 31 to 34 in the direction in which the photosensitive drums 21 are arranged between the support rolls 31 and 32. A straight line portion 30a extending substantially linearly along with the support roll 34, and the support roll 34 is most distantly arranged below the straight line portion 30a, and the angle formed by the support rolls 32, 33, 34 is an acute angle. The support roll 33 is disposed outside a straight line connecting the support rolls 32 and 34.
In the present embodiment, as shown in FIG. 2, the support roll 31 is used as a drive roll driven by a belt drive motor (not shown), the support roll 32 is used as a driven roll, The support roll 33 is used as a correction roll for regulating meandering in a direction substantially perpendicular to the moving direction of the intermediate transfer belt 30 (steering roll: provided to be tiltable around one axial end as a fulcrum). It is used as a backup roll of the collective transfer device 50.
Further, a belt cleaner 35 for removing residual toner on the intermediate transfer belt 30 after the secondary transfer is retractably provided on the surface of the intermediate transfer belt 30 facing the support roll 31.
[0022]
Further, in the present embodiment, as shown in FIG. 3, for example, as shown in FIG. 3, the batch transfer device 50 has a volume resistivity of, for example, 10 which is stretched over a plurality of (for example, two) rolls 51 and 52.⁶-10¹⁰The transfer belt 53 has a semi-conductive transfer belt 53 of Ωcm. For example, one of the rolls 51 is used as a transfer roll and pressed against the intermediate transfer belt 30 via the transfer belt 53. A backup roll 34, which is also used as a stretching roll of the intermediate transfer belt 30, is disposed on the back side, and the transfer belt 53 is disposed toward the fixing nip area of the fixing device 70 along the sheet 100 conveyance direction. is there.
In the present embodiment, a predetermined transfer bias 55 is applied to the backup roll 34 via a conductive power supply roll 54, while the transfer roll 51 is grounded, and the transfer roll 51 and the backup roll A predetermined transfer electric field is formed between the lines. Note that the roll 52 is grounded.
[0023]
Next, a basic image forming process of the image forming apparatus according to the present embodiment will be described.
Now, when image data of each color component image (black, yellow, magenta, cyan) read by the document reading device 10 is sent to the exposure device 23 of each image forming unit 20 (20a to 20d), each image forming unit On the photosensitive drum 21 of the unit 20, an electrostatic latent image for each color component is formed, and an unfixed toner image of each color is formed by the developing device 24 containing the corresponding color toner.
Then, the unfixed toner image of each color component is applied to the base material of the intermediate transfer belt 30 by the primary transfer device 25 at the primary transfer site where the respective photosensitive drums 21 and the intermediate transfer belt 30 are in contact with each other. By applying a polarity voltage, primary transfer is performed in such a manner that the primary transfer is sequentially performed on the surface of the intermediate transfer belt 30.
The unfixed toner image primary-transferred onto the intermediate transfer belt 30 in this manner is conveyed to a secondary transfer portion facing the conveyance path of the paper 100 as a recording material as the intermediate transfer belt 30 rotates. .
[0024]
At the secondary transfer portion, the collective transfer device 50 presses the transfer roll 51 onto the backup roll 34 disposed in the space inside the intermediate transfer belt 30 via the semiconductive transfer belt 53 and the intermediate transfer belt 30, and The paper 100 transported from the paper tray 82 (paper transport system 80) by the feed roller 81 (paper transport system 80) at a predetermined timing passes through a predetermined number of transport rolls 83 (paper transport system 80) and is transferred to the transfer belt 53 and the intermediate transfer. It is sandwiched between the belt 30.
Here, when a voltage having the same polarity as the charged polarity of the toner is applied to the backup roll 34 (a voltage having a polarity opposite to the charged polarity of the toner may be applied to the transfer roll 51), the backup roll 34 and the transfer roll 51 are transferred. The unfixed toner image held on the intermediate transfer belt 30 is electrostatically transferred to the sheet 100 at the secondary transfer portion by the transfer electric field formed between the intermediate transfer belt 30.
Then, the transferred paper 100 is peeled off from the intermediate transfer belt 30 by the electric field of the transfer belt 53 arranged on the downstream side in the paper transport direction, is held on the transport surface of the transfer belt 53, and is transported. The sheet is peeled off from the transfer belt 53 by a placed paper peeling member (not shown), and fed to the fixing device 70 to fix the unfixed toner image.
On the other hand, the belt cleaner 35 removes residual toner from the intermediate transfer belt 30 on which the transfer of the unfixed toner image onto the sheet 100 has been completed.
[0025]
Here, various ideas adopted for the collective transfer device 50 in the present embodiment will be described.
First, in the present embodiment, as shown in FIGS. 2 and 3, the collective transfer device 50 can move the transfer roll 51 so as to be able to advance and retreat with a belt advance / retreat mechanism 56 using the other roll 52 as a rotation axis. It has become.
For this reason, for example, if the transfer roll 51 is pressed against the intermediate transfer belt 30 via the transfer belt 53 only at the time of the secondary transfer, and separated from the intermediate transfer belt 30 at other times, the intermediate transfer belt It is possible to minimize the driving load of the 30.
[0026]
In the present embodiment, the transfer belt 53 of the collective transfer device 50 includes an intermediate transfer belt driving system 37 (Drive motorFor example, the transfer roller 51 is forcibly driven by a drive transmission system including a pulley, a belt, and the like, and is driven and rotated. The transfer roller 51 is adjusted so as not to generate a speed difference with the intermediate transfer belt 30. ing.
For this reason, when a speed difference occurs between the two, there is a concern that the peeling operation of the paper 100 is impaired by the difference in the transport speed of the front and back surfaces of the paper 100, but such a concern is effectively avoided. become.
Incidentally, as long as the transfer belt 53 and the intermediate transfer belt 30 of the collective transfer device 50 are driven synchronously, the transfer belt 53 may be driven and rotated by an independent drive system. is there.
[0027]
Further, as the rolls 31 to 34 on which the intermediate transfer belt 30 is stretched, hard rolls are used in order to suppress the rotation speed fluctuation of the intermediate transfer belt 30. Therefore, a relatively hard roll is also used for the backup roll 34. It is necessary to use.
Under such circumstances, in the present embodiment, in order to maintain a predetermined transfer nip width for performing transfer and to prevent generation of a hollow character, as shown in FIG. To make the transfer roll 51 relatively low in hardness, lower the nip load per unit area, and elastically deform the transfer roll 51 side,Dig intoThe transfer nip area N is formed.
As a result, the rotation speed fluctuation of the intermediate transfer belt 30 is suppressed, the image quality trouble does not occur, and the transfer roller 51 side is softened. It is ripped and easily peeled off from the intermediate transfer belt 30.
[0028]
Further, in the present embodiment, the sheet conveying surface 53a of the transfer belt 53 of the batch transfer device 50 connects the center axis of the transfer roll 51 and the center axis (center of curvature) of the backup roll 34, as shown in FIG. Of the perpendiculars perpendicular to the axis center line, a reference line M passing through the exit of the transfer nip area N between the transfer roll 51 and the backup roll 34 falls downward in the range of θ ゜ (0 to 15 ゜ in the present embodiment). Are located.
Here, the relationship between the angle of the transfer belt 53 when the perpendicular of the axis of the transfer roll 51 and the backup roll 34 is 0 degree (the direction below the perpendicular is minus) and the peeling failure rate, and the transfer FIG. 5 shows the relationship between the belt 53 angle and the image unevenness occurrence level.
[0029]
As a result of analyzing the results of FIG. 5, when the angle of the transfer belt 53 is more positive than 0 °, the paper 100 immediately after the transfer nip area is discharged in the direction of the intermediate transfer belt 30, so that the influence of the intermediate transfer belt 30 is strong. Assuming that the sheet adsorbing force of the intermediate transfer belt 30 is P1 and the force of the sheet 100 to separate from the intermediate transfer belt 30 due to the waist is P2, P1> P2. The level of occurrence of image unevenness also deteriorates due to the retransfer.
On the other hand, when the angle is 0 ° or less on the minus side, image unevenness hardly occurs, and when -10 ° to -15 °, peeling failure hardly occurs.
[0030]
However, on the minus side exceeding -15 °, the force P2 for separating from the transfer belt 53 caused by the stiffness of the sheet 100 is larger than the sheet suction force P1 of the transfer belt 53, and the occurrence rate of peeling failure increases. Therefore, it can be said that the optimal angle of the transfer belt 53 is -10 ° to -15 °.
By giving such an angle to the transfer belt 53, the paper 100 peeled after passing through the transfer nip area is discharged along the transfer belt 53 without being attracted to the intermediate transfer belt 30 at the maximum, and causes peeling failure. Nothing. Further, retransfer due to peeling discharge does not occur, and the image quality is not affected.
[0031]
Furthermore, in the present embodiment, as for the transfer belt 53 of the collective transfer device 50, the transfer distance of one transfer belt 53 is at least that the sheet 100 is transferred without being affected by the intermediate transfer belt 30. The intermediate transfer belt 30 must be disposed so as to extend to a position where the intermediate transfer belt 30 can be removed and not to be re-adsorbed after the intermediate transfer belt 30 has been separated.
Preferably, the transfer distance of one transfer belt 53 is equal to or longer than the maximum sheet length (for example, JIS standard A3 size), so that when the sheet 100 enters the fixing nip area of the fixing device 70, the secondary transfer section, It is preferable that the sheet 100 be stably conveyed to the fixing device 70 without being nipped by both of the fixing devices 70 at the same time, without being affected by the secondary transfer, the speed difference of the fixing device 70, and the like.
[0032]
◎ Embodiment 2
FIG. 6 is an explanatory diagram illustrating a main part of the image forming apparatus according to the second embodiment.
In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment, but is different from the first embodiment in that the transfer distance of the transfer belt 53 of the collective transfer device 50 is set to the maximum sheet length L or more. Further, the transfer belt 53 is divided into a plurality of, for example, two transfer belts 53 (1) and 53 (2) on the transfer path to the fixing device 70, and the paper transfer surface 53a is disposed on the same surface. Things.
In the present embodiment, the transport belt 53 (1) on the upstream side of the batch transfer device 50 is stretched over a pair of rolls 51 and 52 including the transfer roll 51, and the transport belt 53 (2) on the downstream side is The transport belts 53 (1), 53 (2) are wound around a pair of rolls 57, 58, and are driven and rotated separately and independently by a belt drive system (not shown).
Note that components similar to those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted.
[0033]
In the present embodiment, when the paper 100 is carried into the fixing device 70, the speed of the transfer belt 53 is set to a fixing processing speed, for example, a speed at which the carrying speed of the paper 100 is slightly higher than the rotation speed of the fixing roll 71. Is preferred.
With this configuration, for example, when the normal speed (transfer processing speed) of the transfer belt 53 is lower than the fixing process speed, after the transfer is completed, when the rear end of the sheet 100 exits the transfer nip area, the transfer belt 53 , The paper 100 can be conveyed to the fixing device 70, and the conveyance of the paper 100 to the fixing device 70 is performed smoothly.
When the fixing processing speed is lower than the transfer processing speed, as shown in FIGS. 7A and 7B, the entire length of the sheet 100 is placed on the transfer belt 53 (53 (1), 53 (2)). If the speed of the transfer belt 53 is reduced from the transfer speed (indicated by a thick arrow line in the drawing) to the fixing processing speed (indicated by a thin arrow line in the drawing) at the time of riding, without forming a loop, The sheet 100 is transported to the fixing device 70 without fail.
In particular, in the present embodiment, the transfer nip-side transfer belt 53 (1) is returned to the transfer processing speed when the sheet 100 comes off from the transfer belt 53 (1) on the transfer nip area side (upstream side). For example, as shown in FIG. 7C, the paper 100 is transported to the fixing device 70 while the transport speed of the transport belt 53 (2) on the fixing device side (downstream side) is maintained at the fixing processing speed, and at the same time, the next Since the transfer process can be performed on the sheet 100 ', the productivity is improved accordingly.
[0034]
◎ Embodiment 3
FIG. 8 shows an image forming apparatus according to a third embodiment of the present invention.
In the figure, the image forming apparatus has one photoconductor drum 101 and an intermediate transfer belt 110 arranged in contact with the photoconductor drum 101, unlike the first and second embodiments. A charging device 102 for charging the photosensitive drum 101, an exposure device 103 for writing an electrostatic latent image for each color component, and a plurality of developing units containing toners for each color component are mounted and intermittently face the photosensitive drum 101. A primary transfer device 105 such as a rotary developing device 104 that arranges and visualizes an electrostatic latent image with a corresponding toner, a transfer roll that transfers each color component toner image on the photosensitive drum 101 to the intermediate transfer belt 110 And a drum cleaner 106 for removing the residual toner on the photosensitive drum 101.
The intermediate transfer belt 110 is stretched around, for example, three rolls 111 to 113, and a batch transfer device 120 having substantially the same configuration as that of the first embodiment is provided at a location corresponding to the rolls 113.
Reference numeral 114 denotes a belt cleaner that removes residual toner on the intermediate transfer belt 110.
[0035]
The batch transfer apparatus 120 has a volume resistivity of, for example, 10 stretched over a plurality (for example, two) of rolls 121 and 122.⁶-10¹⁰The transfer belt 123 has a semi-conductive transfer belt 123 of Ωcm. For example, one of the rolls 121 is used as a transfer roll and pressed against the intermediate transfer belt 110 via the transfer belt 123. A backup roll 113, which is also used as a stretching roll for the intermediate transfer belt 110, is disposed on the back side, and a transfer bias (not shown) for forming a transfer electric field for batch transfer between the transfer roll 121 and the backup roll 113. ) Is applied, and the transfer belt 123 is arranged toward the fixing nip area of the fixing device 130 along the transport direction of the sheet 100.
[0036]
Therefore, according to the present embodiment, after the respective color component toner images are sequentially formed on the photosensitive drum 101 and sequentially primary-transferred to the intermediate transfer belt 110, the multi-color image on the intermediate transfer belt 110 is An image forming process of collectively transferring the toner images onto the sheet 100 is performed. Note that the behavior of the sheet 100 after the batch transfer is substantially the same as in the first embodiment.
In particular, in the present embodiment, the toner image formed on the photosensitive drum 101 is secondarily transferred after being sequentially superimposed on the intermediate transfer belt 110 at the same position, so that the final color is not fixed. Until the toner image is primarily transferred to the intermediate transfer belt 110, the transfer belt 123 and the transfer roll 121 of the collective transfer device 120 are held apart from the intermediate transfer belt 110 about the roll 122 on the downstream side in the transport direction of the transfer belt 123 as a rotation axis. It is necessary to.
When the entire unfixed toner image on the intermediate transfer belt 110 has passed the secondary transfer position, the transfer belt 123 is pressed against the backup roll 113 via the intermediate transfer belt 110 at the same speed as the rotation speed of the intermediate transfer belt 110. Then, a secondary transfer process is performed.
[0037]
【The invention's effect】
As described above, according to the present invention, a batch transfer device is provided between a plurality of rolls.Of a given volume resistivityStretch a semi-conductive belt,Located upstream in the recording material transport directionThe roll functions as a transfer roll for forming a transfer electric field between the backup member and the backup member.And, the recording material transport surface of the belt is configured only on the downstream side of the transfer roll with respect to the transport direction of the recording material,The transfer, recording material peeling, and recording material adsorption / conveyance functions are provided, and the recording material is conveyed continuously from transfer to fixing. Therefore, the transfer operation is stabilized while simplifying the device configuration. In addition to the above, it is possible to stabilize the behavior of the recording material immediately after the transfer and to make the conveyance state of the recording material uniform without being affected by the type of the recording material.
Further, since the recording material immediately after the transfer is conveyed by the belt, there is no need to provide a guide member such as a recording material guide immediately after the transfer, and even in a low humidity environment, the situation where the recording material is caught by the guide member can be effectively avoided. .
For this reason,While stabilizing the transfer operation with a simple configuration,It is possible to always maintain good releasability of the recording material from the intermediate transfer belt without being affected by the type of the recording material, and to stabilize the conveyance of the recording material to the fixing device.
[0038]
In the present invention, if the backup member is made relatively hard and the transfer roll is made to have a lower hardness than the backup member so as to form the transfer nip area, for example, the tension roll of the intermediate transfer belt can be formed. Even when used as a backup member, fluctuations in the rotation speed of the intermediate transfer belt can be suppressed, and the situation that affects image quality due to fluctuations in the rotation speed can be effectively avoided. Nip load can be reduced, so that the transfer operation can be performed stably while effectively avoiding the image quality trouble of the central part of the image called the holographic character..
Further, since a transfer nip area that cuts into the transfer roll is formed between the transfer roll and the backup member, the releasability of the recording material from the intermediate transfer belt along the elastic deformation locus of the transfer roll is kept good. be able to.
[0039]
Further, in the present invention, among the perpendiculars perpendicular to an axis center line connecting the central axis of the transfer roll and the center of curvature of the backup member, a batch transfer is performed with respect to a reference line passing through a transfer nip area exit between the transfer roll and the backup member. By arranging the recording material conveying surface of the belt of the apparatus at least below, it is possible to effectively avoid image quality deterioration (image unevenness due to retransfer) due to peeling discharge.
In particular, if the recording material conveying surface of the belt of the batch transfer device is disposed below the reference line within a range of 0 ° to 15 °, image quality deterioration due to peeling discharge can be achieved while avoiding poor peeling of the recording material. (Image unevenness due to retransfer) can be effectively avoided.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a configuration of an image forming apparatus according to the present invention.
FIG. 2 is an explanatory diagram illustrating an outline of the image forming apparatus according to the first embodiment;
FIG. 3 is an explanatory diagram showing details of a batch transfer device used in the first embodiment;
FIG. 4 is an explanatory diagram showing an optimal layout example of a recording material conveying surface of a belt of the collective transfer device used in the first embodiment.
FIG. 5 is a graph showing a relationship between a transfer belt angle and a peeling defect occurrence rate / image unevenness occurrence level in the first embodiment.
FIG. 6 is an explanatory diagram illustrating a main part of an image forming apparatus according to a second embodiment;
FIGS. 7A to 7C are explanatory views showing an operation example of the collective transfer device of FIG. 6;
FIG. 8 is an explanatory diagram illustrating an outline of an image forming apparatus according to a third embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Intermediate transfer belt, 3 ... Batch transfer device, 4 ... Recording material, 5a, 5b ... Roll, 6 ... Belt, 6a ... Recording material conveyance surface, 7 ... Transfer roll, 8 ... Backup member, 9: transfer bias applying means, 21 (21a to 21d): photosensitive drum, 30: intermediate transfer belt, 34: backup roll, 50: batch transfer device, 51: transfer roll (roll), 52: roll, 53, 53 (1), 53 (2): transfer belt, 54: power supply roll, 55: transfer bias, 101: photosensitive drum, 110: intermediate transfer belt, 113: backup roll, 120: batch transfer device, 121: transfer roll ( Roll), 122 ... Roll, 123 ... Transfer belt

Claims (3)

One or a plurality of image carriers (1) on which each color component image is formed and carried; an intermediate transfer belt (2) on which each color component image on the image carrier (1) is intermediately transferred and carried; An image forming apparatus comprising: a collective transfer device (3) for collectively transferring each color component image on the transfer belt (2) to a recording material (4);
The batch transfer device (3) includes a plurality of rolls (5a, 5b) and a semiconductive belt (6) rotatably stretched around the rolls (5a, 5b) and having a volume resistivity of 10 ⁶ to 10 ¹⁰ Ωcm. )
Of the plurality of rolls (5a, 5b), the roll (5a) located on the upstream side in the transport direction of the recording material (4) is used as a transfer roll (7) via a belt (6) stretched over the intermediate transfer belt (2). ), And a backup member (8) is disposed on the back side of the intermediate transfer belt (2) facing the transfer roll (7).
A transfer bias applying unit (9) for forming a transfer electric field for batch transfer is provided between the transfer roll (7) and the backup member (8 ), and at least one of the plurality of rolls (5a, 5b) is grounded. Providing a recording material transport surface (6a) of the belt (6) only on the downstream side of the transfer roll (7) with respect to the transport direction of the recording material (4);
Further, forming the transfer nip region biting into the transfer roll (7) side between the rather low than the hardness, and the transfer roller (7) and the backup member (8) of the hardness of the backup member (8) of the transfer roll (7) An image forming apparatus, comprising: The image forming apparatus according to claim 1,
Further, the recording material transporting surface (6a) of the belt (6) has a transfer roll (7) of a perpendicular line perpendicular to an axial center line connecting the center axis of the transfer roll (7) and the center of curvature of the backup member (8). ) And a backup member (8), the image forming apparatus is disposed at least below a reference line passing through a nip area outlet. The image forming apparatus according to claim 2,
The recording material conveying surface (6a) of the belt (6) of the batch transfer device (3) is a perpendicular line perpendicular to an axis center line connecting the center axis of the transfer roll (7) and the center of curvature of the backup member (8). An image forming apparatus which is disposed below a reference line passing through a nip area exit between a transfer roll (7) and a backup member (8) within a range of 0 to 15 °.

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