JP2002091200A - Image forming device and developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image forming device from causing transfer failure due to a wrinkle in a transfer material. SOLUTION: The image forming device has at least image carriers 1 and transfer rollers 7 which are disposed opposite the corresponding image carriers 1 holding a carrying path of the transfer material 13 between them and transfer toner images formed on the surfaces of the corresponding image carriers 1 to the surface of the transfer material 13. The transfer material 13 is carried so as to be wrapped around the transfer rollers 7. Position where the toner images are transferred from the corresponding image carriers 1 to the transfer material are within wrapped areas L1, L3, L5, and L7 where the transfer material 13 is wrapped around the transfer roller 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus using a belt-shaped transfer material and a developing device suitable for the image forming apparatus.

[0002]

2. Description of the Related Art FIG. 10 is a schematic configuration diagram of a conventional image forming apparatus using electrophotography. As shown in FIG. 10, the image forming unit 15 of the conventional image forming apparatus
Photosensitive drum 1 as an image carrier in proximity to the travel path 3
Around the photosensitive drum 1, a charging device 2, an exposure device 3, a developing device 4, a squeezing device 5, a set corona device 6, and the like are arranged along the rotation direction of the photosensitive drum 1 (indicated by an arrow in the drawing). A transfer roller 7, a cleaning device 8, and a charge removing device 9 are sequentially arranged. Of these, the transfer roller 7
Is such that the transfer paper 13 is sandwiched between the photosensitive drum 1 and
The photosensitive drum 1 is disposed on the opposite side of the traveling path of the transfer paper 13.

With the above-described configuration, in the conventional image forming unit 15, first, in the process of rotating the photosensitive drum 1, the surface (photosensitive surface) of the photosensitive drum 1 is positively (+) charged by the charging device 2, for example. Then, the surface of the photosensitive drum 1 is exposed by the exposure device 3, and the electrostatic latent image 1 is formed on the surface.
0 is formed. Further, the toner liquid (liquid developer) 11 in the liquid reservoir 4 a is applied to the surface of the photosensitive drum 1 by the developing roller 4 b of the developing device 4, and is applied to the electrostatic latent image 10 by the electric attraction force of the electrostatic latent image 10. A corresponding toner image 12 is formed. The toner liquid 11 is obtained by dispersing toner particles charged to a specific polarity in an insulating liquid. Here, the toner particles are positively (+) charged.

After the toner image 12 is formed by the developing device 4, the excess insulating liquid in the toner image 12 is removed by the squeezing device 5, and the set corona device 6 imparts a charge having the same polarity as the toner particles. The cohesion of the particles is increased. Then, when the toner image 12 comes into contact with the transfer paper 13 due to the further rotation of the photosensitive drum 1, the transfer roller 7 causes a charge having a polarity opposite to that of the toner particles of the toner image 12 [here, negative (−) ), The toner particles forming the toner image 12 are attracted to the transfer paper 13 from the surface of the photosensitive drum 1, and the toner image 12 is transferred to the surface of the transfer paper 13.
Thereafter, toner particles remaining on the surface of the photosensitive drum 1 are removed by the cleaning device 8, and electric charges remaining on the surface of the photosensitive drum 1 are removed by the charge removing device 9.

The image forming unit 15 is for monochrome printing, and its printing color is determined by the color of toner particles in the toner liquid 11. For this reason, when performing multi-color printing, a number of image forming units 15 corresponding to the number of printing colors are arranged along the traveling path of the transfer paper 13. For example, FIG. 11 is a schematic configuration diagram of a general wet-type printing press in a case where two-color printing and double-sided printing are performed on the belt-shaped transfer paper 13.

In the conventional printing press shown in FIG. 11, the traveling path of the transfer paper 13 is set to be substantially vertical in order to reduce the width of the apparatus, and four image forming units 15 are vertically arranged along the traveling path. I have. The lower two image forming units 15 are for printing on the back surface, and the upper two image forming units 1
5 is for printing on the surface. A plurality of transport rollers 16 are provided in the printing machine, and the transfer paper 13 is wound around the peripheral surface of the transport rollers 16. The transfer paper 13 is continuously fed out from a take-up roll 14,
While being guided along the traveling route by the transport rollers 16, first, the first two image forming units 15
The printing of the color and the second color is performed on the back surface. And the fixing device 1
8, the solvent is dried and removed from the paper surface of the transfer paper 13 and the toner image is melted and fixed on the paper surface.
The turn bar 19 reverses the transfer paper 13. The inverted transfer paper 13 is subsequently subjected to printing of a third color and a fourth color on the surface thereof by the upper two image forming units 15, and thereafter the final fixing device 20 removes the solvent by drying and removes the solvent onto the paper. The melting and fixing of the toner image is performed. The transfer paper 13 having both sides printed thereon is cut by the cutter 21 at the exit of the traveling path and discharged onto the tray 22.

[0007]

However, in the conventional printing press having the structure shown in FIG. 11, a tension in the running direction (longitudinal direction) acts on the transfer paper 13 between the transport rollers 16 and 16, so that this tension is not applied. There is a problem that paper wrinkles are easily generated on the surface of the transfer paper 13 by the action, and transfer failure due to the paper wrinkles is easily generated. This is transfer paper 1
At the transfer position where the toner image contacts the toner image 3, the convex portion of the paper wrinkle comes in contact with the toner image first and the solvent of the toner image is absorbed. It is considered that the amount of solvent necessary for the process is insufficient. In particular, when the transfer paper 13 is thin, wrinkles are likely to occur due to the application of the tension necessary for transporting the transfer paper 13, and transfer failures due to the paper wrinkles are likely to occur. Further, in the above-described conventional printing press, multicolor printing can be easily performed by adding the image forming unit 15, but this does not cause a problem when the number of printing colors increases as the number of printing colors decreases. Minor transfer failures are more noticeable as color variations.
Therefore, in order to enable multicolor printing with stable image quality, it is particularly important to prevent transfer unevenness due to paper wrinkles.

In order to increase the number of printing colors, it is a simple method to extend the traveling path of the transfer paper 13 in the structure shown in FIG. 11 in the vertical direction and add the image forming unit 15 vertically. If the number of additional forming units 15 is large, the vertical length of the printing press becomes too large, which causes problems in installation space, maintainability, and the like. Therefore, in order to increase the number of image forming units 15 without increasing the vertical length of the printing press, an apparatus configuration as shown in FIGS. 12 and 13 has been proposed. 12 and 13 both show an apparatus configuration for two-sided four-color printing. The printing press shown in FIG. 12 has a format in which the traveling path of the transfer paper 13 is simply folded at the top (U-turn pass), and the printing shown in FIG. Machine is transfer paper 1
This is a form (S-turn path) in which the traveling route of No. 3 is folded twice at the top and bottom. 12, the developing device 4 needs to be installed above the photosensitive drum 1 due to the structure of the image forming unit 15. However, the conventional developing device 4
As shown in FIG. 10, the location where the toner liquid stored in the liquid reservoir 4 a is supplied to the photosensitive drum 1 by the rotation of the developing roller 4 b is limited. It is practically difficult to install it on the upper part. On the other hand, in the form of FIG. 13, although there is no difficulty in installing the developing device 4, the amount of waste paper increases as the traveling path of the transfer paper 13 becomes longer.

The present invention has been made in view of the above problems, and has as its object to provide an image forming apparatus capable of preventing occurrence of transfer failure due to wrinkles of a transfer material. It is another object of the present invention to provide an image forming apparatus in which the traveling path of a transfer material is shortened to reduce the occurrence of waste paper. It is another object of the present invention to provide a developing device that enables a highly flexible arrangement with respect to an image carrier of an image forming apparatus.

[0010]

In order to achieve the above object, an image forming apparatus according to the present invention comprises an image carrier and a traveling path of a transfer material (sheet-like or band-like web) with respect to the image carrier. A transfer roller disposed between the transfer roller and a transfer roller for transferring the toner image formed on the surface of the image carrier to the surface of the transfer material, wherein the transfer material is wound around the peripheral surface of the transfer roller. The transfer device is configured to run while being rotated, and that the transfer position of the toner image from the image carrier to the transfer material is set within a winding area where the transfer material is wound around the transfer roller. Features. Note that the term "in the winding area" refers to a range from the start end to the end of the transfer material being wound around the transfer roller. Preferably, the transfer position is set inside the start end and the end.

Preferably, a plurality of image carriers are provided around the transfer roller so that each toner image is transferred from each image carrier to the surface of the transfer material in the winding area. Constitute. With such a configuration, it is possible to perform multicolor printing with a compact device structure while preventing wrinkles from occurring on the transfer material. Also, more preferably,
A pair of the transfer rollers is provided, and the transfer material runs while being wound in an S-shape between the pair of transfer rollers. With such a configuration, it is possible to perform double-sided multicolor printing with a compact device structure while preventing wrinkles from occurring on the transfer material. In this case, the diameter of the transfer roller is preferably equal to or greater than the diameter of the image carrier.

A conductive rotating member for rotating the transfer roller in contact with the transfer material and rotating with the travel of the transfer material;
It is also preferable that the image forming apparatus further includes a plurality of charge applying means provided inside the rotating member corresponding to each image carrier to apply a charge having a polarity opposite to that of the toner particles of the toner image to the transfer material. With such a configuration, the transfer condition can be set for each image carrier while sharing one transfer roller, and the image quality can be stabilized. Note that the charge applying means only has to have a function of arbitrarily adjusting the amount of charge to be applied, for example, a corona charger that applies charge without contacting the rotating member, or a rotating member. A conductive roller or the like that imparts electric charge by contact can be used.

As a developing means for supplying a toner liquid to the electrostatic latent image formed on the surface of the image carrier to form the toner image, the developing means is connected in series with a liquid storage container for storing the toner liquid. At least two or more rollers are arranged so as to be in contact with each other, and one end roller is disposed in the liquid container and the other end roller is disposed in contact with the image carrier.
It is preferable that the at least two or more rollers are rotated in predetermined directions to transfer and supply the toner liquid from the liquid reservoir to the image carrier. With such a configuration, the degree of freedom of the supply position of the toner liquid on the image carrier can be increased.
More preferably, the absolute value of the applied bias voltage is set smaller for a roller closer to the image carrier. With such a configuration, the toner particles can be sequentially moved and adhered to the roller side on the image carrier side, and the density of the toner liquid supplied to the image carrier can be prevented from becoming low to achieve a predetermined image density. Can be secured.

According to another aspect of the present invention, there is provided a developing device comprising: an image carrier; and a toner image formed on a surface of the image carrier disposed on the image carrier with a transfer material traveling path interposed therebetween. And a transfer roller for transferring the toner image onto the transfer material from the image carrier to the transfer material. Is set in a pressure contact area where the transfer material presses against the transfer roller. The term "in the pressure contact area" refers to a range from the start end to the end where the transfer material is pressed against the transfer roller. Preferably, the transfer position is set inside the start end and the end.

According to another aspect of the present invention, there is provided a developing device for an image forming apparatus including at least a liquid container for storing a toner liquid and a developing roller in contact with an image carrier. And at least two rollers arranged in series contact with each other, wherein one of the at least two rollers is disposed in the reservoir and the other roller is the developing roller. The toner liquid in the liquid reservoir is transferred to and supplied to the image carrier by rotating the at least two or more rollers in a predetermined direction, and the at least two or more rollers are rotated. It is characterized in that a bias voltage whose absolute value is set smaller as the roller is closer to the image carrier is applied to the roller.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a first embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a printing machine to which an image forming apparatus as a first embodiment of the present invention is applied, and FIG. FIG. 2 is a schematic diagram for explaining an operation and an effect of the image forming apparatus according to the first embodiment. 1 and 2, the same parts as those of the above-described conventional image forming apparatus are denoted by the same reference numerals.

The printing machine 30 shown in FIG. 1 is for one-sided four-color printing, and prints four colors according to the printing color along the traveling path of the transfer paper 13.
One image forming unit (image forming apparatus) 31 is provided. The transfer paper 13 is a belt-shaped continuous paper, and is continuously fed out from the take-up roll 14 and is transferred to each image forming unit 3.
After the printing in step 1, the solvent is dried and removed by the fixing device 20 and the toner image is fixed and fused on the paper surface. It has become. In the present embodiment, the transfer paper 13 includes the image forming units 3 in addition to the guide rollers 16.
The guide roller 1 is also guided by the transfer roller 7. That is, the transfer paper 13 is wound around a predetermined range on the peripheral surface of each transfer roller 7, and runs while being guided by the rotation of each transfer roller 7. In other words, the transfer paper 13 is pressed against the peripheral surface of each transfer roller 7 over a predetermined length in the running direction.

The position at which the photosensitive drum 1 as an image carrier is disposed is determined based on the transfer position of the toner image from the photosensitive drum 1 to the transfer sheet 13 in the area where the transfer sheet 13 is wound around the peripheral surface of the transfer roller 7 ( (Winding area).
That is, the photosensitive drum 1 is disposed on the side opposite to the transfer roller 7 with respect to the traveling path of the transfer paper 13, and sandwiches the transfer paper 13 between the photosensitive drum 1 and the transfer roller 7 in the above-mentioned winding area (pressing area). In. Around the photosensitive drum 1, similarly to a conventional image forming unit (see FIG. 10), a charging device 2, an exposing device 3, a developing device 4 , A squeeze device 5, a set corona device 6, a transfer roller 7, a cleaning device 8, and a static eliminator 9.

Next, the operation and effects of the image forming apparatus according to the first embodiment of the present invention configured as described above will be described with reference to FIG. As described above, the transfer sheet 13 travels while being guided by the guide roller 16 and the transfer roller 7. At this time, the transfer sheet 13 includes the guide roller 16.
Alternatively, an area wound around the transfer roller 7 (a wound area)
Between the guide roller 16 and the transfer roller 7, or between the transfer roller 7,
7 free areas are created. As shown in FIG. 2, in the free areas L2, L4, and L6 of the transfer sheet 13, vertical wrinkles 33 corresponding to the strength of the tension acting in the traveling direction of the transfer sheet 13 occur as in the related art. However, transfer paper 1
3 are wound around the transfer roller 7 in the winding regions L1, L3, L
In L5 and L7, since the transfer paper 13 is pressed against the peripheral surface of the transfer roller 7, the wrinkles are extended by the surface pressure received from the peripheral surface of the transfer roller 7, so that vertical wrinkles such as the free area do not occur. Each of the photosensitive drums 1 transfers the transfer paper 1 in the winding regions L1, L3, L5, L7 without such wrinkles.
Touch 3. Then, by applying a charge having a polarity opposite to that of the toner particles from the transfer roller 7, these winding regions L1,
In L3, L5, and L7, a toner image is transferred from the surface of each photosensitive drum 1 to the surface of the transfer paper 13.

Therefore, according to the present image forming apparatus, since the toner image is not transferred in the wrinkled area of the transfer paper 13 unlike the related art, the transfer of transfer unevenness or the like caused by the wrinkles of the transfer paper 13 is performed. No failure occurs. For this reason, even if the number of printing colors is increased, a change in the color tone due to transfer failure does not become conspicuous as in the related art, and multicolor printing with stable image quality can be performed.

FIGS. 1 and 2 show a case of four-color printing as an example, and the image forming unit 31 may be provided according to the number of printing colors. The arrangement positions (layouts) of the respective image forming units 31 shown in FIGS. 1 and 2 are merely examples, and the transfer paper 13 is configured to run while being wound around the peripheral surface of the transfer roller 7. The layout of each image forming unit 31 is not limited as long as the transfer position of the toner image from the drum 1 to the transfer sheet 13 is set within the winding area where the transfer sheet 13 is wound around the transfer roller 7.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a schematic configuration diagram of a printing machine to which the image forming apparatus according to the second embodiment of the present invention is applied, and FIG. 4 is a diagram illustrating the operation and effects of the image forming apparatus according to the second embodiment of the present invention. FIG.
In FIGS. 3 and 4, the same parts as those of the image forming apparatus of the first embodiment described above are denoted by the same reference numerals, and redundant description will be omitted.

The printing press 35 shown in FIG. 3 is for single-sided, four-color printing as in the first embodiment, and is provided with four image forming units 36 corresponding to the printing colors along the traveling path of the transfer paper 13. I have. The image forming unit 36 includes a photosensitive drum 1 as an image carrier and a photosensitive drum 1 as in the first embodiment.
A charging device 2, an exposing device 3, a developing device 4, a squeezing device 5, a set corona device 6, a transfer roller 37, a cleaning device 8, and a static eliminator 9 are arranged around the device. Each image forming unit 36 is characterized by sharing a single transfer roller 37. Here, the entire four image forming units 36 sharing the transfer roller 37 correspond to the image forming apparatus of the present invention.

The transfer roller 37 of this embodiment is formed to have a larger diameter than the photosensitive drum 1, and the transfer paper 13 is wound around a predetermined area on the peripheral surface. The transfer paper 13 travels along a predetermined travel route while being guided by the rotation of the guide roller 16 and the transfer roller 37.
The photosensitive drum 1 of each image forming unit 36 has a transfer roller 3
7, the transfer position of the toner image from each photosensitive drum 1 to the transfer paper 13 is set in a winding area where the transfer paper 13 is wound around the peripheral surface of the transfer roller 37, that is, The respective arrangement positions are adjusted so that the transfer paper 13 is within the range from the start end to the end where the transfer paper 13 is wound around the peripheral surface of the transfer roller 37 (in particular, inside the start end and the end).

Next, the operation and effects of the image forming apparatus according to the second embodiment of the present invention configured as described above will be described with reference to FIG. The transfer paper 13 is the transfer roller 3
7, the transfer sheet 13 has a winding area L9 wound around the transfer roller 37 as shown in FIG.
Thus, free areas L8 and L10 that do not contact the transfer roller 37 and the guide roller 16 are formed. In the winding area L9 of the transfer paper 13, the wrinkles are extended by the surface pressure received from the peripheral surface of the transfer roller 37 when the transfer paper 13 is pressed against the peripheral surface of the transfer roller 37, so that the free areas L8, L10
The vertical wrinkles 38 do not occur due to the tension acting in the traveling direction of the transfer paper 13 as described above. Each photosensitive drum 1
Is in contact with the transfer sheet 13 in the wrinkle-free winding area L9 as in the first embodiment, and is supplied with a charge having a polarity opposite to that of the toner particles from the transfer roller 37. At the time, the toner image is transferred from the surface of each photosensitive drum 1 to the surface of the transfer paper 13.

Therefore, according to the present image forming apparatus, as in the first embodiment, transfer defects such as transfer unevenness due to wrinkles of the transfer sheet 13 do not occur, and multicolor printing with stable image quality can be performed. Become. Further, since the winding area where the transfer paper 13 is wound around the transfer roller 37 can be made longer than in the first embodiment, the wrinkles of the transfer paper 13 can be more reliably extended to prevent the occurrence of transfer failure. Can be.

The embodiment in which the image forming apparatus of the present invention is applied to a printing machine for single-sided printing has been described above. However, the image forming apparatus of the present invention has a double-sided printing as in a third embodiment described below. It is also possible to apply to a printing press for printing. Hereinafter, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a schematic configuration diagram of a printing machine to which the image forming apparatus according to the third embodiment of the present invention is applied. In FIG. 5, the same parts as those of the image forming apparatuses of the first and second embodiments described above are denoted by the same reference numerals, and redundant description will be omitted.

The printing machine 40 according to the present embodiment is for two-sided four-color printing, and as shown in FIG. 5, a back-side image forming unit 41 and a front-side image forming unit 43 along the traveling path of the transfer paper 13. And four are arranged respectively. Each of the image forming units 41 and 43 has the same configuration as that of the second embodiment, and a single transfer roller 42 and a single transfer roller 42 are provided between the image forming units 41 and between the image forming units 43, respectively.
44 are shared. The two transfer rollers 42 and 44 are arranged at a predetermined distance from each other, and the transfer paper 13 is wound in an S-shape around the peripheral surfaces of the two transfer rollers 42 and 44. The photosensitive drums 1 of the image forming units 41 and 43 are disposed at predetermined intervals around transfer rollers 42 and 44, respectively.
A transfer position of the toner image from each photosensitive drum 1 to the transfer paper 13 is set in a winding area wound around the peripheral surfaces of the transfer rollers 2 and 44. Here, the whole of the four image forming units 41 sharing the transfer roller 42 and the four image forming units 43 sharing the transfer roller 44 correspond to the image forming apparatus of the present invention.

With the configuration described above, the transfer of the toner image from the front surface of each photosensitive drum 1 to the front and back surfaces of the transfer paper 13 is performed in the same manner as in the first and second embodiments. It is performed within the time domain. Therefore, according to the present image forming apparatus, similarly to the first and second embodiments, transfer defects such as transfer unevenness due to wrinkles of the transfer sheet 13 do not occur, and two-sided multicolor printing with stable image quality can be performed. Become. Further, according to the present image forming apparatus, by winding the transfer paper 13 in an S-shape around the peripheral surfaces of the two transfer rollers 42 and 44, the vertical length of the apparatus can be suppressed and the traveling of the transfer paper 13 can be performed. The path can be shortened to minimize the occurrence of waste paper. Further, according to the present image forming apparatus, when the number of print colors is increased, the diameter of the transfer rollers 42 and 44 may be increased and the photosensitive drum 1 may be additionally provided. It is limited to the increase in the diameter of 42 and 44, and the increase in the amount of waste paper is reduced.

In the image forming apparatuses of the second and third embodiments, the transfer rollers 37, 42, and 44 are shared between the image forming units 36, 41, and 43. , 41, 43, the transfer roller 3
It is difficult to adjust the transfer voltage or transfer current of 7, 42, 44. Therefore, for example, when the appropriate transfer voltage or transfer current differs for each printing color, the image forming apparatuses of the second and third embodiments may not be able to cope with the case.

Therefore, an image forming apparatus according to a fourth embodiment of the present invention described below has the advantages obtained by the image forming apparatuses according to the second and third embodiments, and further has an appropriate printing color for each printing color. Transfer voltage or transfer current can be applied. Here, FIG. 6 is a schematic configuration diagram of a printing machine to which the image forming apparatus according to the fourth embodiment of the present invention is applied. In addition,
6, the same parts as those of the image forming apparatuses according to the first to third embodiments described above are denoted by the same reference numerals,
Duplicate description will be omitted.

The printing press 45 shown in FIG.
This is a double-sided four-color printing press having the same configuration as the printing press according to the embodiment and including four image forming units 46 for the back surface and four image forming units 48 for the front surface.
However, each of the image forming units 4 is different from the third embodiment.
There is a difference in the configuration of the transfer rollers 47 and 49 shared between the image transfer units 6 and the image forming units 48, respectively. That is, in the present embodiment, each transfer roller 47, 49 has a function of adjusting the transfer voltage for each image forming unit 46, 48.

More specifically, the transfer roller 47 shared between the image forming units 46 for backside printing is a transfer sheet 1
The rotating member 50 includes a hollow rotating member 50 that rotates in contact with the transfer sheet 13 while the transfer sheet 13 is running, and a corona charger 51 disposed inside the rotating member 50 in a non-contact state with the rotating member 50. In the rotating member 50, at least a ring portion that contacts the transfer sheet 13 is formed of a conductive material (rubber or the like) having a large resistance value. The corona charger 51 is provided for each image forming unit 46 toward a contact position between the photosensitive drum 1 and the transfer paper 13. An external power supply capable of adjusting the voltage (transfer voltage) is connected to each corona charger 51, and is discharged from a central wire by application of a high voltage from the external power supply.
Is to be charged. When the electrode of the toner particles is positive (+), the voltage applied to the corona charger 51 is negative, and the corona charger 51 discharges a negative (−) charge having a polarity opposite to that of the toner particles.

On the other hand, each image forming unit 4 for front side printing
The transfer roller 49 shared by the transfer rollers 8 includes a conductive roller 52 disposed inside the rotating member 50 in contact with the rotating member 50. The conductive roller 52 is provided for each image forming unit 48 in correspondence with the contact position between the photosensitive drum 1 and the transfer paper 13. An external power supply capable of adjusting the voltage (transfer voltage) is connected to each of the conductive rollers 52, and is charged by application of a high voltage from the external power supply so that the charge is applied to the transfer paper 13 through the rotating member 50. Has become. When the electrode of the toner particles is positive (+), the voltage applied to the conductive roller 52 is negative, and the conductive roller 52 is charged with a negative (−) charge having a polarity opposite to that of the toner particles.

With this configuration, according to the present image forming apparatus, by adjusting the transfer voltage applied to each corona charger 51 or the transfer voltage applied to each conductive roller 52, Image forming units 46 and 4
The transfer condition can be set for each of the eight transfer conditions. Therefore,
Even if the proper conditions differ depending on the toner (print color), the image forming apparatus can realize the proper transfer conditions according to the characteristics of each toner, and stabilize the image quality even when the print color increases. Can be done. In FIG. 6, the corona charger 5 is attached to the transfer roller 47 for backside printing.
1, and the transfer roller 49 for surface printing includes the conductive roller 52. However, both transfer rollers 47 and 49 may include the same charge applying unit. The charge applying means is not limited to the corona charger 51 or the conductive roller 52, but may be any as long as it has a function of individually adjusting the transfer current or the transfer voltage.

Next, an image forming apparatus according to a fifth embodiment of the present invention will be described with reference to FIG. The fifth embodiment is particularly characterized in the configuration of the developing device constituting the image forming apparatus. Here, only the developing device which is a characteristic portion will be mainly described. FIG. 7 is a diagram for explaining the configuration of the developing device according to the present embodiment and its operational effects.
FIG. 7A is a schematic configuration diagram of a developing device according to the present embodiment, and FIG. 7B is a schematic configuration diagram of a conventional developing device as a comparative example.

In the conventional developing device 4 shown in FIG.
In order for the developing roller 4b to come into contact with the photosensitive drum 1 without interfering with the liquid container 4a, there is an upper limit on the installation position of the developing device 4 with respect to the photosensitive drum 1. For this reason, when the photosensitive drum 1 is positioned above the transfer roller 37 as shown in FIG. 7B, the space from the development by the developing device 4 to the transfer to the transfer paper 13 is reduced, and There is a concern that it may be difficult to install the squeeze device 5 and the set corona device 6 that should be located in the rotation direction of the photosensitive drum 1 with respect to the device 4. Therefore, in an image forming apparatus provided with the conventional developing device 4, the device layout is greatly restricted by the installable range of the developing device 4.

On the other hand, as shown in FIG. 7A, a developing device 55 according to the present embodiment includes a liquid container 56 for storing the toner liquid 11 and a photosensitive drum 1 from the liquid container 56.
And at least two (three in FIG. 7A) rollers 57, 58 and 59 for supplying the toner liquid 11 to the surface of the roller. The rollers 57, 58, 59 are arranged so as to be in series contact between the liquid reservoir 56 and the photosensitive drum 1. Numeral 58 rotates in the same direction as the photosensitive drum 1 at a predetermined speed, and transfers and supplies the toner liquid 11 from the liquid reservoir 56 to the photosensitive drum 1. That is, the roller 57 at the tip is the photosensitive drum 1
, A rear end roller 59 is a scooping roller for scooping up the toner liquid 11 from the liquid reservoir 56, and an intermediate roller 58 is a toner from the scooping roller 59 to the developing roller 57. Each functions as a delivery roller for delivering the liquid.

With this configuration, in the present developing device 55, at least two or more developing rollers 57, 58, 59
Are arranged in series, the upper limit position at which the liquid reservoir 56 and the developing roller 59 interfere with each other can be made higher than that of the conventional developing device 4. Further, since the liquid reservoir 56a can be installed at a position away from the photosensitive drum 1,
The possibility of interference with other devices such as the squeeze device 5 and the set corona device 6 is reduced. In other words, the developing device 55 has the degree of freedom of the installation position with respect to the photosensitive drum 1 and the
Extremely high compared to. Therefore, according to the image forming apparatus provided with the main developing device 55, the degree of freedom of the device layout can be extremely increased.

FIG. 7A shows a schematic configuration in the case where the present developing device 55 is applied to the image forming apparatus of the second embodiment.
It goes without saying that the present invention can be applied to any of the image forming apparatuses of the embodiments. Also, the number of rollers to be arranged may be at least two or more, and as shown in FIG.
It is not limited to one. However, the greater the number of rollers to be arranged, the higher the degree of freedom of arrangement of the developing device 55.

Next, an image forming apparatus according to a sixth embodiment of the present invention will be described with reference to FIG. The sixth embodiment has a feature in the configuration of the developing device as in the fifth embodiment, and particularly has a feature in that the toner supply characteristics of the developing device of the fifth embodiment are improved. FIG. 8 is a diagram for explaining the configuration of the developing device according to the present embodiment and its operational effects, and FIG. 8A is a schematic diagram for explaining the operation of the developing device according to the present embodiment. FIG. 8B is a schematic diagram for explaining the operation of the developing device as a comparative example.

As shown in FIG. 8A, a developing device 55 'according to the present embodiment includes a liquid storage container 56 for storing the toner liquid 11, similarly to the developing device of the fifth embodiment, and at least two or more. [Three rollers in FIG. 8A]
8, 59. The method of supplying the toner liquid 11 from the liquid reservoir 56 to the photosensitive drum 1 is the same as in the fifth embodiment, and a description thereof will be omitted. The present embodiment is characterized in that bias voltages of different magnitudes are applied to the rollers 57, 58, 59. More specifically, during development, a bias voltage having the same polarity as the charge of the toner particles 60 is generally applied to a toner liquid supply roller such as a developing roller. Bias voltages V ₁ , V ₂ ,
The absolute value of V ₃ is set smaller roller closer to the photosensitive drum 1 _{(i.e., | V 1 | <| V} 2 | <| V 3 |).

Hereinafter, the operation and effect of setting the bias voltage as described above will be described in the case where the bias voltages applied to the rollers 57, 58, 59 are set to be equal (that is, V
₁ = V ₂ = V ₃ ). Each roller 5
The transfer of the toner liquid 11 between 7, 58 and 59 is performed by a part of the toner liquid 11 adhering to the upstream roller being separated at the time of contact with the downstream roller and adhering to the downstream roller. For this reason, the liquid film of the toner liquid 11 formed on the roller gradually becomes thinner each time the film is transferred between the rollers. Therefore, when the concentration of the toner particles 60 in the toner liquid 11 is constant on each of the rollers 57, 58, and 59, the amount of the toner particles 60 is also transferred between the rollers as shown in FIG. When the number of rollers that transfer and supply the toner liquid 11 is large, there is a possibility that a sufficient amount of toner to be supplied to the photosensitive drum 1 may not be secured at the leading developing roller.

However, in the developing device 55 'according to this embodiment, since a potential difference is provided between the rollers, an electric field is generated between the rollers due to the potential difference. For this reason, the toner liquid 11 scooped up from the inside of the liquid reservoir 56 by the roller 59 is supplied to the gap between the rollers 58 and 59. The toner particles 60 move and adhere to the roller 58 side. This is because the toner particles 60 are positively (+) charged and the roller 58 has a lower potential than the roller 59. As a result, a liquid film of the concentrated toner liquid 11 is formed on the roller 58. The toner particles 60 in the concentrated toner liquid 11 move and adhere to the lower-potential roller 57 side due to the electric field between the subsequent rollers 57 and 58, and the further concentrated toner liquid 11 is transferred from the roller 57 to the photosensitive drum 1. Supplied to

As described above, according to the developing device 55 'of the present embodiment, the toner liquid 11 can be concentrated in the process of transferring between the rollers 57, 58, and 59.
A reduction in the supply amount of the toner particles 60 due to the thinning of the toner liquid 11 is suppressed, and a sufficient amount of the toner particles 60 are transferred to the photosensitive drum 1.
Can be supplied to Therefore, according to the image forming apparatus including the developing device 55 'of the present embodiment, the same effect as that of the fifth embodiment can be obtained, and sufficient image density can be ensured even when the number of rollers is increased. become.

The embodiments of the image forming apparatus and the developing apparatus of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention. Can be implemented. For example, in each of the above-described embodiments, the case where the image forming apparatus of the present invention is applied to a printing machine using a band-shaped transfer sheet has been described.

In the above embodiment, the transfer paper 13
Is wound around the peripheral surface of the transfer roller over the required angle range, but the transfer paper 13 may be simply pressed against the peripheral surface of the transfer roller with almost no angle. Even in this case,
Since the wrinkles of the transfer paper 13 are stretched in the area pressed against the peripheral surface of the transfer roller, transfer failure due to the wrinkles can be prevented.

The developing device 55 (55 ') according to the fifth and sixth embodiments is not only applied to the image forming apparatus of the present invention described in the first to fourth embodiments, but is shown in FIG. Thus, the present invention can be applied to a conventional image forming apparatus. Also in this case, there is an effect that the degree of freedom of arrangement with respect to the photosensitive drum 1 can be increased, and the degree of freedom of arrangement of the entire image forming apparatus can be increased. In particular, according to the developing device 55 'according to the sixth embodiment, there is an effect that a sufficient image density can be ensured regardless of the number of rollers.

[0049]

As described above in detail, according to the image forming apparatus of the present invention, wrinkles do not occur on the transfer material in the winding region where the transfer material is wound around the transfer roller, and the toner image is not wrinkled. Since the image is transferred onto the transfer material in the winding region where there is no transfer, there is an effect that transfer failure due to wrinkles of the transfer material is prevented. Therefore, even when used for multicolor printing, a change in color tone due to transfer failure does not become conspicuous, and multicolor printing with stable image quality can be performed.

Further, by arranging a plurality of image carriers around the transfer roller so that each toner image is transferred from each image carrier to the surface of the transfer material in the above-mentioned winding area, a large number of images can be obtained. In the case of performing color printing, there is an effect that the traveling path of the transfer material can be shortened to reduce the occurrence of waste paper. In particular, by arranging a pair of transfer rollers and by arranging the transfer material to run while being wound in an S-shape between the pair of transfer rollers, the traveling path of the transfer material when performing double-sided multicolor printing is improved. There is an effect that generation of waste paper can be reduced by shortening the length.

According to another image forming apparatus of the present invention, wrinkles do not occur in the transfer material in a pressure contact area where the transfer material presses against the transfer roller, and the toner image is transferred in a winding area without the wrinkles. Since the transfer is performed on the transfer material, there is an effect that transfer failure due to wrinkles of the transfer material is prevented. Therefore, even when used for multicolor printing, a change in color tone due to transfer failure does not become conspicuous, and multicolor printing with stable image quality can be performed.

Further, according to the developing device of the present invention, since the toner liquid is supplied from the liquid reservoir to the image carrier via at least two or more rollers, the image carrier is supplied to the image carrier. A highly flexible arrangement is possible,
By applying a bias voltage having a smaller absolute value to a roller closer to the image carrier, a sufficient amount of toner particles can be supplied to the image carrier to ensure image density regardless of the number of rollers. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a printing machine to which an image forming apparatus according to a first embodiment of the invention is applied.

FIG. 2 is a schematic diagram for explaining an operation and an effect of the image forming apparatus as the first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a printing machine to which an image forming apparatus according to a second embodiment of the invention is applied.

FIG. 4 is a schematic diagram for explaining an operation and an effect of an image forming apparatus as a second embodiment of the present invention.

FIG. 5 is a schematic diagram for explaining an operation and an effect of an image forming apparatus as a third embodiment of the present invention.

FIG. 6 is a schematic diagram for explaining an operation and an effect of an image forming apparatus as a fourth embodiment of the present invention.

FIGS. 7A and 7B are diagrams for explaining the configuration of a developing device according to a fifth embodiment of the present invention and the effects thereof, wherein FIG. 7A is a schematic configuration diagram of the developing device according to the present embodiment, and FIG. FIG. 5 is a schematic configuration diagram of a conventional developing device as a comparative example.

FIGS. 8A and 8B are diagrams for explaining a configuration of a developing device according to a sixth embodiment of the present invention and the effects thereof, and FIG. 8A is a diagram for explaining the operation of the developing device according to the present embodiment; FIG. 3B is a schematic diagram for explaining the operation of the developing device as a comparative example.

FIG. 9 is a schematic configuration diagram of a conventional type image forming apparatus to which the developing device of the present invention is applied.

FIG. 10 is a schematic configuration diagram of a conventional electrophotographic image forming apparatus.

FIG. 11 is a schematic configuration diagram of a conventional general two-sided two-color printing press.

FIG. 12 is an explanatory diagram for explaining a problem of the conventional image forming apparatus, and illustrates a double-sided surface 4 to which the conventional image forming apparatus is applied.
It is a schematic structure figure of a printing machine for color printing.

FIG. 13 is an explanatory diagram for explaining a problem of the conventional image forming apparatus, and illustrates a double-sided surface 4 to which the conventional image forming apparatus is applied.
It is a schematic structure figure of a printing machine for color printing.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photoconductor drum 2 charging device 3 exposure device 4,55,55 'developing device 5 squeeze device 6 set corona device 7,37,42,44,47,49 transfer roller 8 cleaning device 9 static eliminator 11 toner liquid 13 transfer paper Reference Signs List 50 Rotating member 51 Corona charger 52 Conductive roller 56 Liquid reservoir 57 Developing roller 58 Delivery roller 59 Scooping roller 60 Toner particles 31, 36, 41, 43, 46, 48 Image forming unit L1, L3, L5, L7, L9 Winding area (pressure contact area) L2, L4, L6, L8, L10 Free area

Continued on the front page (72) Inventor Norifumi Tasaka 5007 Itozakicho, Mihara-shi, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. F term in the Printing Machinery Division (reference) 2H028 BA03 BA06 2H030 AB02 AD05 BB27 BB44 BB46 2H032 AA05 BA16 BA19 2H073 AA02 BA02 BA13 CA22 CA33 2H074 AA03 AA41 BB02 BB08 BB43 CC28

Claims (8)

[Claims] 1. An image carrier, and a transfer roller disposed on the image carrier with a traveling path of a transfer material interposed therebetween to transfer a toner image formed on the surface of the image carrier to the surface of the transfer material. Wherein the transfer material is configured to travel while being wound around the peripheral surface of the transfer roller, and the transfer position of the toner image from the image carrier to the transfer material is determined by: An image forming apparatus, wherein a transfer material is set in a winding area wound around the transfer roller. 2. A plurality of image carriers are provided around the transfer roller, and each toner image is transferred from each image carrier to the surface of the transfer material in the winding area. The image forming apparatus according to claim 1, wherein: 3. The transfer roller according to claim 2, wherein a pair of the transfer rollers is provided, and the transfer material runs while being wound in an S-shape between the pair of transfer rollers. Image forming apparatus. 4. The transfer roller according to claim 1, wherein the transfer roller is a conductive rotating member that contacts the transfer material and rotates with the movement of the transfer material. 4. The image forming apparatus according to claim 2, further comprising a plurality of charge applying means for applying a charge having a polarity opposite to that of the toner particles of the toner image to the material. 5. A developing means for supplying a toner liquid to an electrostatic latent image formed on the surface of the image carrier to form the toner image, wherein the developing means comprises a liquid reservoir for storing the toner liquid. A container, having at least two or more rollers arranged to be in contact with each other in series, wherein one of the at least two or more rollers is disposed in the liquid reservoir and the other end is A roller is provided in contact with the image carrier, and the at least two or more rollers are each rotated in a predetermined direction to transfer and supply the toner liquid from the liquid reservoir to the image carrier. The image forming apparatus according to claim 2, wherein: 6. The image forming apparatus according to claim 5, wherein the absolute value of the bias voltage applied to the roller closer to the image carrier is set smaller. 7. An image carrier, and a transfer roller disposed on the image carrier with a traveling path of the transfer material interposed therebetween and transferring a toner image formed on the surface of the image carrier to the surface of the transfer material. Wherein the transfer material is configured to travel while being pressed against the peripheral surface of the transfer roller, and a transfer position of the toner image from the image carrier to the transfer material is determined by the transfer position. An image forming apparatus, wherein a material is set in a pressure contact area where the material is pressed against the transfer roller. 8. A developing device for an image forming apparatus, comprising at least a liquid reservoir for storing a toner liquid and a developing roller in contact with an image carrier, wherein at least two or more rollers arranged so as to be in series contact with each other. A roller at one end of the at least two or more rollers is disposed in the reservoir, and a roller at the other end is the developing roller, and the at least two or more rollers are moved in predetermined directions, respectively. By rotating, the toner liquid in the liquid reservoir is transferred to and supplied to the image carrier, and the at least two or more rollers have a smaller absolute value as the roller is closer to the image carrier. A developing device, wherein a set bias voltage is applied.