JP2831682B2 - Transfer device for image recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device for an image recording device of a superimposed transfer system.

2. Description of the Related Art As a full-color image recording apparatus using an electrophotographic method, a color separation image superimposing transfer system is generally used. As one of the recording apparatuses of this type, as shown in FIG.
Image information light obtained by color-separating a document into three colors of blue, green, and red is read on the four photosensitive drums 1A, 2A, 3A, and 4A, respectively, and image calculation processing is performed based on the intensity level of each color light. Optical writing is performed based on the write image data to be developed in each color of yellow, magenta, cyan, and black obtained by performing the above operation, and the obtained electrostatic latent image is provided on each of the photosensitive drums. , Magenta, cyan, black developer 1
B, 2B, 3B, and 4B are developed, and each color toner image formed on each photoconductor drum is transferred to a transfer belt 5 that rotates sequentially in contact with each photoconductor drum via a registration roller 7 from a paper feeding unit. The transfer belts 5 are sandwiched between transfer belts 5 at positions in contact with the respective photosensitive drums under the action of transfer chargers 1C, 2C, 3C, and 4C, which are electrically attracted and conveyed. There has been known a color image recording apparatus in which a full-color image is obtained by fixing and fixing by a fixing roller 8 after transfer is performed. In the example shown in the figure, each color-separated image information is optically color-separated by a document reading unit 9 provided at the upper part of the image forming apparatus main body, read by three CCDs 10, and subjected to arithmetic processing based on the output signals. Based on the color image data obtained by
Optical writing is performed by a laser writing device provided for A, 2A, 3A, and 4A.

The transfer belt 5 is made of a dielectric material such as a polyester film and is charged by the transfer chargers 1C, 2C, 3C, and 4C. The transfer belt 5 is initialized by removing charges from both sides by the charge removing charger 6, and prepares for the next image transfer.

Note that there is also known an image recording apparatus that uses a transfer belt as an intermediate transfer material, directly superimposes and transfers toner images of each color onto the intermediate transfer material, and then transfers the toner image to transfer paper fed in contact with the transfer belt at one time.

However, in a transfer device that uses a dielectric belt as a transfer sheet conveying means or an intermediate transfer material, in order to improve the adhesion between the dielectric belt or the transfer paper conveyed by the dielectric belt and the photoreceptor, the transfer belt needs to be moved from the back side of the transfer belt. A backup member for supporting the belt is required. As a backup member,
In order to reduce the transport load of the transfer belt 5 as much as possible, as shown in the figure, a roller 11 that is driven by the belt or driven at the same linear speed as the belt is employed. The roller is conventionally conventionally made of metal and grounded to provide cylindricity.

As described above, the transfer belt is charged by the transfer charge, and when the metal roller partially contacts as described above, for example, as described in JP-B-55-33072 and JP-A-56-97357. Image disorder is likely to occur. The reason is,
When the belt member suddenly approaches or comes into contact with the backup member, the electric field applied to the toner is rapidly disturbed by the electric field generated between the belt and the backup member, and an electric field particularly in the horizontal direction is easily generated, and the toner scatters in that direction. by. The same applies to the case where the belt suddenly separates from the backup member. Another cause is that as the belt moves away from the backup member, the potential between the belt and the backup member rises, causing peeling discharge, neutralizing the charge on the back side of the belt, and thus eliminating the force of restraining the toner. Another reason is that the toner easily moves.

The inventor of the present invention has proposed the following apparatus as a measure for preventing the above-described image disorder in view of the actual situation.

The apparatus will be described with reference to the image forming apparatus described with reference to FIG. 2 as an example. As shown in FIG. 3, between the position immediately after the transfer position on the most upstream side and the position where the transfer paper leaves the transfer belt 5. A conductive member, for example, an electric field stabilizer 12 made of metal is provided in the vicinity of the rear surface of the transfer belt 5 except for portions where the transfer chargers 1C, 2C, 3C, 4C and the backup roller 11 are provided.

The electric field stabilizer 12 prevents the transfer belt 5 from approaching the backup roller 11 and leaving the backup roller 11 from abruptly changing the electric field, so that the transfer belt 5 is conveyed on the transfer belt 5. The electric field applied to the toner on the transfer paper is stabilized, and image disturbance is reduced. Further, since the electric field stabilizer 12 is provided close to the back surface of the transfer belt 5, a potential rise between the belt 5 and the backup roller 11 or the electric field stabilizer 12 is small, and peeling discharge hardly occurs.ゝ

The electric field stabilizer 12 is maintained at a constant potential by being directly grounded or grounded via a resistor or a constant voltage element. The electric field stabilizer can be made of a conductive material other than metal.

As shown in FIG. 4, the electric field stabilizer 13 may have an arc-shaped cross section without the backup roller 11, and the protruding back may be brought into contact with the back surface of the transfer belt 5 so as to also serve as the backup roller. In this case, since the area in contact with the belt is small, the conveyance force of the belt is not reduced.

However, as a result of subsequent studies, in the above proposed device, discharge and disturbance of the electric field occasionally occur at the position of the scratches and irregularities generated by the electric field stabilizer for some reason or at the end of the electric field stabilizer. It was found that image disturbance could not be completely prevented.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a transfer device capable of more effectively preventing image disturbance in an image forming apparatus having the above configuration.

Means and Action for Solving the Problems In order to solve the above-mentioned problems, a first aspect of the present invention is to provide, in addition to an electric field stabilizing plate provided close to the back surface of the transfer belt, a front surface of the transfer belt on the transfer paper transport side. Also, a conductive member is provided between the photoreceptors with a certain gap from the surface of the transfer belt.

As described above, in addition to the electric field stabilizer on the back side of the belt, the conductive member is further disposed between the photoconductors on the front side of the belt, so that a discharge occurs between the belt and the electric field stabilizer on the back side of the belt. Even when the electric field is disturbed, the conductive member is provided on the upper side of the belt 4 in opposition to the toner on the transfer paper conveyed to the transfer belt, so that a vertical electric field is generated between the toner and the conductive member. Therefore, no force for moving the toner in the horizontal direction is generated. That is, since the electric field may be stabilized by any one of the conductive members on the front surface side and the back surface side of the belt, image disturbance can be prevented very well.

If a cleaning unit for the photoconductor is used as the conductive member disposed to face the transfer belt surface, it is not necessary to add a new member.

As another problem of the full-color copying apparatus, there is a problem of a transfer failure in which a thin line or an edge portion of a solid image, in particular, a portion having a large amount of toner adhesion, is missing in the copying process. It is known that adding an additive for improving the fluidity, for example, hydrophobic silica or the like, to the toner is effective as a countermeasure against the hollow phenomenon.

However, according to the first aspect of the present invention, when a conductive member is disposed at a predetermined gap from the front surface of the transfer belt on the front surface side of the transfer belt as well as on the back surface side of the transfer belt, the When a toner containing an additive such as silica or the like for preventing a hollow phenomenon is added, the toner scatters and adheres to the surface of the conductive member on the transfer belt surface side facing the toner image. Therefore, the state of resolution degradation due to the scattering of toner also appears on the image, or the toner attached to the conductive member accumulates and rubs against the toner image on the belt surface or transfer paper conveyed thereby,
There is a problem that image rubbing occurs.

In order to solve this problem, a second aspect of the present invention is directed to the above-described first aspect, further comprising a conductive belt provided on the back side of the photoreceptor in the width direction of the photoconductor in contact with the surface of the transfer belt. An insulating guide member for guiding the member to move while maintaining a predetermined distance from the member is provided.

The above toner scattering phenomenon is caused by the fact that the charge on the transfer paper including the toner image and the charge on the back of the belt are attracted to each other by the Coulomb force and are stable. In the case of contact with or very close to an object with the same low potential, the charge on the back surface of the belt is apparently neutralized, and the charge of the toner image becomes easier for the toner to move along a new electric field generated toward the upper surface. It is presumed that this occurs.

Therefore, according to the above configuration of the second invention, the transfer belt is moved by the insulating guide member while maintaining a predetermined distance from the conductive member provided on the back side thereof. Without contact or close proximity,
In addition, since the guide member is insulative, the toner on the back surface of the belt does not become neutralized, the toner is stably conveyed, the toner does not scatter, and the resolution caused by the toner is reduced. Deterioration and occurrence of image rubbing can be prevented.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a transfer belt 5 and photosensitive drums 1A and 2 of an embodiment in which the first invention is applied to the image forming apparatus described in FIG.
FIG. 3 is a diagram showing a configuration near A, 3A, and 4A. As shown in the figure, an electric field stabilizer 12 similar to that shown in FIG. 3 is provided near the rear surface of the upper running portion of the transfer belt 5, and a conductive material is also provided on the upper surface of the upper running portion of the transfer belt 5. For example, a metal electric field stabilizer 15
Are provided between adjacent photosensitive drums.
The electric field stabilizer 15 is provided at a predetermined distance from the surface of the transfer belt and at a predetermined distance so as not to hinder the transfer of the transfer paper carrying the toner image transferred on the transfer belt 5. This interval is, for example, 2
Approximately 3 mm. Both ends are bent obliquely upward. Of course, this interval is not limited to this,
Any distance may be used as long as the effect of the conductive member 15 is attained, but it is preferably larger than the distance from the conductive member immediately behind the belt to the belt.

Further, it was confirmed that the effect was not changed even if a thin insulating layer was provided on the surface of the upper conductive member 15 facing the belt 5. When the insulating layer is coated with, for example, ethylene tetrafluoride resin, even if toner or the like adheres, it can be easily wiped off and handling becomes easy.

Further, the conductive member 15 provided on the upper portion of the belt serves as a tray for the developer or toner that falls from the developing devices 1B, 2B, 3B, and 4B and the cleaning device. Contamination by these is prevented.

Incidentally, a cleaning unit is provided in contact with the photoconductor downstream of the transfer position in order to remove toner and paper dust remaining on the photoconductor after transfer. Therefore, when the housing of the cleaning unit is made of a conductive material, by appropriately designing its shape and arrangement, the cleaning unit can also be used as the conductive member disposed opposite to the transfer belt surface of the present invention. Can be. FIG. 1A is a view showing one example of this, in which at least the bottom of the housing of the cleaning unit 18 for each of the photosensitive drums 1A, 2A, 3A, 4A is made of a conductive material, and the surface of the transfer belt 5 It is shaped and arranged to extend along the transfer belt at intervals, for example, at intervals of about 2 to 3 mm, and also serves as the conductive member of the present invention.

As a result, it is not necessary to separately provide a dedicated conductive member, which is advantageous in terms of cost and arrangement.

The present invention is also applied to a transfer drum of an image forming apparatus that transfers a plurality of toner images formed on a single photoconductor onto a single transfer paper wound around a single transfer drum. be able to.

 FIG. 5 is a diagram showing one example.

Around the photoreceptor drum 20, a charging charger 21, an image writing optical system 22, four-color developing units 23M, 23C,
23Y and 23B, a transfer drum 24, and a cleaning device 25 are provided. The transfer drum is formed by stretching a dielectric sheet of polyethylene terephthalate or the like on a frame of aluminum or the like, and rotates in the same direction and at the same speed at the contact portion in synchronization with the photosensitive drum at the same diameter as the photosensitive drum. The transfer drum 24 has a paper feed unit 26
The transfer paper is fed, the leading end is clamped, and it is attracted and wound on a dielectric transfer drum, and four color toner images sequentially formed on the photosensitive drum 20 are superimposed on the same transfer paper by the transfer charger 27. After the transfer, the static elimination charger 28
, And is separated by the separation claw 29, and is fixed by the fixing device 30 to form a full-color copy. Transfer drum 24
The electric field stabilizers 31 and 32 are provided at predetermined intervals on the back side and the front side, respectively, in a range excluding each charger, sheet feeding position, and separation position.

Next, an embodiment of the second invention will be described with reference to the drawings.

FIG. 6 shows a transfer belt 5 and photosensitive drums 1A, 2A, 2B of an embodiment in which the second invention is applied to the image forming apparatus shown in FIG.
3A and 4A are views showing a configuration in the vicinity. In this example,
The backup roller made of metal according to the embodiment described with reference to FIG.
Instead of 11, a rubber roller 16 is provided. The rubber roller 16 is, as shown in detail in FIG.
16a is coated with a rubber layer having a thickness of, for example, 3 mm, and extends in parallel with the axis of the photosensitive drum. The transfer drum 5 is arranged such that the back surface of the belt maintains a predetermined distance from the back surface side electric field stabilizer 12. It serves as a guide to guide the paper to be transported. On the front side of the transfer belt 5, a front side electric field stabilizer 15 is provided at a predetermined distance from the front side. The electric field stabilizers 12, 15 are made of a conductive material such as metal and are grounded.

The electric field stabilizers 12, 15 are similar to the embodiment of the first invention in that the electric field prevents stable image disturbance. However, in the present embodiment, the transfer belt 5 further includes a rubber roller. The transfer belt 5 and the metal core 16a are conveyed by the roller 16 while maintaining a predetermined distance from the back surface side electric field stabilizing plate 12 without contacting or coming in close proximity to each other, and since the rubber roller 16 is an insulating material. The toner image is stably conveyed without the charge on the back surface of the transfer belt 5 being neutralized, and the occurrence of the toner scattering phenomenon is prevented.

The insulating backup member for guiding the transfer belt 5 is replaced with the rubber roller 16 of the above embodiment, as shown in FIG.
An electric field stabilizer 12 made of a conductive material such as a metal is extended without interruption between two adjacent transfer chargers, for example, 1C and 2C, and is arranged near the center thereof in parallel with the axial direction of the photosensitive drum. A guide member 17 made of an insulating material (e.g., a Kamaboko shape) that can guide the transfer belt 5 to be slid and conveyed while maintaining a predetermined distance from the electric field stabilizer 12 may be provided. Electric field stabilizers 12 and 15 are grounded.

The operation and effect of this device are the same as those of the embodiment described with reference to FIG. The guide member 17 of this shape has a greater degree of freedom in material selection as compared to the rubber roller described above, and is easier to process and lower in cost.

Table 1 shows the experimental results on the height t of the guide member 17, that is, the distance between the transfer belt 5 and the electric field stabilizer 12 and the effect of preventing toner scattering when the material of the guide member 17 is variously changed.

With toner scattering: × With toner scattering or ゝ: Without toner scattering: ○ From this table, it is sufficient if the distance between the transfer belt and the electric field stabilizer on the back side of the belt is at least 2.0 mm, and the guide member is formed. It is understood that the volume resistance of the insulating material to be used should be 10 ¹³ Ωcm or more.

In each of the embodiments described above, a system in which toner images of a plurality of colors are superimposed and transferred on transfer paper conveyed by a transfer belt has been described. However, a transfer belt is used as an intermediate transfer material, and a plurality of toner images are directly placed on the intermediate transfer material. The present invention is also applicable to a system in which the toner images are transferred in a superimposed manner and transferred onto transfer paper at a time. 5, a predetermined distance from the electric field stabilizer 31 on the back side of the transfer drum 24 is maintained.
FIG. 9 shows an example in which a guide member 33 for transporting is provided.

Effects As described above, according to the first aspect of the invention, the electric field in the transport area of the toner image transported by the transfer belt is stabilized, and a good transfer image can be obtained. Further, according to the second invention,
Even when the hollowing-out prevention additive is added to the toner, the scattering of the toner does not occur, and the deterioration of the resolving power and the rubbing of the image due to the scattering can be prevented.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an embodiment of the first invention, FIG. 1A is a side sectional view showing another embodiment of the first invention, and FIG. 2 is an example of an image forming apparatus to which the present invention is applied. 3 and 4 are side sectional views showing the structure of a transfer device proposed by the inventor of the present invention, and FIG. 5 is a single sectional view of the first invention. FIG. 6 is a side sectional view showing an embodiment applied to an image forming apparatus having a transfer drum, FIG. 6 is a side sectional view showing an embodiment of the second invention, FIG. 7 is an enlarged sectional view of a main part thereof, and FIG. FIG. 9 is an enlarged sectional view of a main part of another embodiment, and FIG. 9 is a side sectional view showing an embodiment applied to an image forming apparatus having a single photosensitive member and a single transfer drum according to the second invention. It is. 1A, 2A, 3A, 4A photoconductor drum 1C, 2C, 3C, 4C transfer charger 5 transfer belt 11 backup member 12,15 electric field stabilizer (conductive member) 16,17, 33 …… Insulating guide member 18 …… Cleaning unit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/16 G03G 15/01

Claims (3)

(57) [Claims] An image is formed by sequentially superimposing and transferring toner images formed on a plurality of photoconductors onto a transfer belt made of a dielectric material which rotates in contact with the photoconductors sequentially or on the same transfer paper conveyed by the transfer belt. In a transfer device of an image recording apparatus for performing recording, a conductive member is disposed close to the back surface of the transfer belt from immediately after the transfer position on the most upstream side to a transfer end position, and a transfer paper transfer side of the transfer belt is provided. A conductive member disposed between the photoconductors at a predetermined distance from the surface of the transfer belt. 2. The transfer device according to claim 1, wherein the conductive member disposed to face the transfer belt surface is a cleaning unit for the photoconductor. 3. The transfer device according to claim 1, further comprising: contacting the back surface of the transfer belt to maintain the transfer belt at a predetermined distance from the conductive member provided on the back surface side. A transfer member, which is provided in the width direction of the photosensitive member.