JP3018617B2 - Multiple transfer device in image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-transfer device such as a transfer drum for adsorbing and transporting a transfer material such as copy paper in a color electrophotographic apparatus, and more particularly to a transfer device opposite to a suction surface of a transfer material carrier. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-transfer device for transferring a toner image by transferring and charging a surface, and preventing a voltage applied to a transfer charger from excessively increasing during multiple transfer.

[0002]

2. Description of the Related Art The operation of a conventional transfer drum of a color electrophotographic apparatus will be briefly described with reference to FIG. Around the photosensitive drum 1, a main charger (not shown), an exposure device,
A toner developing device for four colors of black, magenta, cyan, and yellow, a cleaning device, and the like are arranged, an electrostatic latent image of a color-separated image is sequentially formed, and a toner image developed with toner of a corresponding color is The image is sequentially transferred onto the copy paper P adsorbed on the peripheral surface of the transfer drum 2. The transfer drum 2 has a drum shape made of an insulating film such as an acrylic resin.
As shown, a deflector roll 3, a suction corotron 4, a transfer corotron 5, a peeling claw 6, a static elimination corotron 7, a cleaning means 8, and the like are arranged around and inside thereof. The deflector roll 3 is made of a conductive material, is grounded, and is configured to be in contact with the transfer drum 2. The cleaning means 8 is composed of a fur brush or the like, and is configured to be in contact with and separated from the transfer drum 2. The peeling claw 6 is also configured to be separated from and connected to the transfer drum 2. The attraction corotron 4 charges the charge (+ in the illustrated case) having a polarity opposite to the polarity (− in the illustrated case) of the toner transferred onto the inner surface of the transfer drum 2, and transfers the transferred transfer paper P to the transfer drum 2. To be adsorbed on the
The deflector roll 3 is brought into contact with the transfer drum 2,
At the same time as the sheet P is held down, a charge having a polarity opposite to the charge (− in the case shown) charged by the suction corotron 4 is injected into the surface of the sheet P. At the transfer position from the photosensitive drum 1, the inner surface of the transfer drum 2 that has absorbed the paper P is further charged by the transfer corotron 5 with a charge having a polarity (+ in the illustrated example) opposite to the polarity of the toner, and the surface of the photosensitive drum 1 is charged. The toner image is transferred onto the sheet P that has been attracted to the transfer drum 2. And
The next color toner image is similarly transferred. However, during this time, the suction corotron 4 does not operate, and the deflector roll 3, the peeling claw 6, and the cleaning unit 8 are separated from the transfer drum 2. When the toner image of the last color is transferred, the peeling claw 6 comes into contact with the transfer drum 2 to peel off the paper P adsorbed on the transfer drum 2, and the peeled paper P is discharged by the paper discharging corotron 9. Then, it is sent to a fixing device (not shown). The inner and outer surfaces of the transfer drum 2 from which the paper P has been peeled are removed by the two opposite charge removing corotrons 7 to which the alternating current is applied. Thereafter, the cleaning means 8 comes into contact with the transfer drum 2 and the toner on the surface thereof,
Paper dust and the like are cleaned.

[0003]

By the way, in the case of multiple transfer, as the number of transfers proceeds to the second, third, and fourth colors, the transfer corotron is superimposed on the previous transferred toner image for efficient transfer. The potential charged by 5 must be increased. In particular, when transferring to an OHP film, transferring in a low-humidity environment, or copying at a high process speed, the leakage current of the paper is reduced. The potential rise is large, and the voltage to be applied to the transfer corotron 5 rises excessively. If the voltage to be applied to the transfer corotron 5 rises beyond a certain level, the leak current in the transfer corotron 5 increases, making it difficult to efficiently perform transfer charging and to obtain desired transfer characteristics.

Conventionally, in order to avoid such an increase in the charging voltage due to the transfer corotron, the transfer surface and the inside of the transfer drum are neutralized every transfer (Japanese Patent Laid-Open No. 61-1339).
No. 60, JP-A-1-257885), an extra charge removing corotron is required, and the control becomes complicated.

The present invention has been made in view of such a situation, and an object of the present invention is to transfer and charge a toner image on a surface opposite to a suction surface of a transfer material carrier of a color electrophotographic apparatus or the like to multiplex a toner image. An object of the present invention is to prevent a voltage applied to a transfer charger from excessively increasing during multiple transfer by using a simple configuration in a multiple transfer device that transfers data to a second transfer device.

[0006]

A multiple transfer device in an image forming apparatus according to the present invention, which achieves the above object, has at least a transfer for superimposing and superimposing a toner image obtained by visualizing an electrostatic latent image. A transfer material carrier made of a sheet-like dielectric material that adsorbs the material and transports the material to the transfer position; and a transfer potential applying unit that applies a transfer potential to the surface of the transfer material carrier opposite to the suction surface at the transfer position. In the multiple transfer device in the image forming apparatus, the transfer potential is applied to at least the surface opposite to the attraction surface of the transfer material carrier before transfer upstream of the attraction potential applying means for attracting the transfer material to the transfer material carrier. A pre-potential applying means for applying a potential of the opposite polarity is provided. A multiple transfer device in another image forming apparatus of the present invention is a sheet that at least adsorbs a transfer material for superimposing and superimposing a toner image obtained by visualizing an electrostatic latent image and conveys the sheet to a transfer position. Transfer device in an image forming apparatus, comprising: a transfer material carrier made of a dielectric material in a shape of a sheet; and a transfer potential applying means for applying a transfer potential to a surface of the transfer material carrier opposite to an adsorption surface at a transfer position. At least upstream of the position, a pre-potential applying means for applying a potential having a polarity opposite to the transfer potential is provided on at least a surface opposite to the suction surface of the transfer material carrier before transfer, and the pre-potential applying means is a transfer material carrier discharging means. It is characterized in that it is configured to also serve as.

In these cases, it is preferable that the pre-potential applying means can adjust the applied potential. Note that a transfer drum is a typical transfer material carrier.

[0008]

In the present invention, at least a surface of the transfer material carrier opposite to the attraction surface of the transfer material carrier before the transfer has a polarity opposite to that of the transfer potential upstream of the attraction potential applying means for attracting the transfer material to the transfer material carrier. A pre-potential applying means for applying an electric potential, or
A pre-potential applying means for applying a potential having a polarity opposite to the transfer potential to at least the surface opposite to the adsorption surface of the transfer material carrier before the transfer, upstream of the transfer position, so that the pre-potential applying device also serves as the transfer material carrier discharging means. Since the configured pre-potential applying means is provided, the potential of the transfer material carrier after transfer is suppressed by that much, and the voltage applied to the transfer potential applying means during multiple transfer excessively increases. As a result, a leak current in the transfer potential applying means is reduced, efficient transfer charging can be performed, and desired transfer characteristics can be obtained. further,
The transfer potential applying means can be small.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the multiple transfer apparatus of the present invention is applied to a color electrophotographic apparatus using a transfer drum will be described.
This will be described with reference to the drawings.

In the present invention, as shown in FIG. 1, the arrangement of the conventional multiple transfer device is most simply changed without any modification, and only the polarity of the voltage applied to the neutralizing corotron is devised.

That is, similarly to the conventional case shown in FIG. 4, in the multiple transfer apparatus, the black, magenta, cyan and yellow toner images formed on the photosensitive drum 1 are attracted to the peripheral surface of the transfer drum 2. The images are sequentially transferred onto the copy sheet P.
The transfer drum 2 has a drum shape made of an insulating film such as an acrylic resin, and has a deflector roll 3, a suction corotron 4, a transfer corotron 5, a peeling claw 6, a static elimination corotron 7, around and inside thereof as shown in the figure. Means 8 and the like are arranged. The attraction corotron 4 charges the charge (+ in the illustrated case) having a polarity opposite to the polarity (− in the illustrated case) of the toner transferred onto the inner surface of the transfer drum 2, and transfers the transferred transfer paper P to the transfer drum 2. To be absorbed. At this time, the deflector roll 3 is brought into contact with the transfer drum 2 to hold down the paper P, and at the same time, charges the paper P with a polarity opposite to the charge (− in the figure) charged by the suction corotron 4.
Inject on the surface. At the transfer position from the photosensitive drum 1, the inner surface of the transfer drum 2 that has absorbed the paper P is further charged by the transfer corotron 5 with a charge having a polarity (+ in the illustrated example) opposite to the polarity of the toner, and the surface of the photosensitive drum 1 is charged. The toner image is transferred onto the sheet P that has been attracted to the transfer drum 2. Then, the toner image of the next color is similarly transferred, but the voltage applied to the transfer corotron 5 is set higher than the previous applied voltage. During this time, the suction corotron 4 does not operate, and the deflector roll 3, the peeling claw 6, and the cleaning unit 8 are separated from the transfer drum 2. When the toner image of the last color is transferred, the peeling claw 6 comes into contact with the transfer drum 2 to peel off the paper P adsorbed on the transfer drum 2, and on the peeled paper P, the paper discharging corotron 9 is used. The charge is removed and sent to a fixing device (not shown).

In the case of the present invention, the transfer drum 2 from which the paper P has been peeled off does not simply remove the charge on the inner and outer surfaces thereof by the charge removing corotron 7 as in the prior art. Performs charging to the opposite polarity. For this purpose, as shown in FIG. 1, an AC voltage with a bias of the same polarity (+ in the drawing) applied to the transfer corotron 5 is applied to the outer corotron 71 of the neutralizing corotron 7, and the inner corotron of the neutralizing corotron 7 is applied. 72
Is applied with an AC voltage having a bias of a polarity opposite to that of the transfer corotron 5 (in the case shown). As described above, if the inner surface of the transfer drum 2 is charged in advance to a polarity opposite to the charging potential of the transfer corotron 5 before charging by the adsorption corotron 4, even if multiple transfer is performed, the toner image of the last color Since the transfer charging potential for the transfer can be reduced by that amount, the voltage to be applied to the transfer corotron 5 is reduced, and therefore, the leakage current in the transfer corotron 5 is eliminated or reduced. Transfer characteristics are obtained.

Specifically, before and after the adsorption of plain paper, after the first transfer, after the second transfer, after the third transfer, and after the fourth transfer,
When the potential of the inner surface of the transfer drum 2 in the cycle before the transfer and before the suction is examined, the result is as shown in FIG. The dotted line in the figure indicates the case of the conventional example. After the paper P is peeled off, the charge is removed by the charge removing corotron 7 to zero potential and then charged by the adsorption corotron 4 and the transfer corotron 5, but the potential of the inner surface of the transfer drum 2 increases as the number of transfers increases. Rises to +2100 V after the fourth transfer. On the other hand, the solid line in the figure shows the case where the charge is removed by the charge removing corotron 7 and charged to -1500 V according to the present invention. In this case, the potential increases only up to +700 V after the fourth transfer. FIG. 3 is a view similar to that in the case of transfer to an OHP film. In the case of the conventional example indicated by the dotted line, the voltage rises to +5400 V after the fourth transfer. Rises only up to +4400 V after the fourth transfer. In particular, as is clear from the latter example, according to the present invention, the leak current in the neutralizing corotron 7 is reduced, efficient transfer is possible, and the transfer corotron 5 can be downsized. In the above embodiment, the charge having the polarity opposite to the charge polarity of the transfer corotron 5 is performed simultaneously with the charge elimination by the charge elimination corotron 7. However, the charge elimination and the charge may be performed by another means. In this case, DC charging corotrons are arranged inside and outside the transfer drum downstream of the static elimination corotron 7 in the conventional example of FIG. 4 so that the inner charging corotron performs negative charging and the outer charging corotron performs positive charging. Good. Further, in the case of a copying machine in which single-color copying or two-color copying can be selected as a copying mode, the charging voltage before adsorption can be adjusted according to mode switching. In this case, the smaller the number of colors to be superimposed, the smaller the absolute value of the pre-charge potential. The transfer material carrier is not limited to a transfer drum, and a plurality of photosensitive drums are arranged in tandem, and a color electrophotographic apparatus of a type in which a color toner image is sequentially transferred to a copy sheet adsorbed on a transfer belt. It can be applied to a transfer belt.

Although the multiple transfer apparatus of the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications are possible.

[0015]

According to the multiple transfer apparatus in the image forming apparatus of the present invention described above, at least the transfer material carrier before transfer is adsorbed upstream of the adsorption potential applying means for adsorbing the transfer material to the transfer material carrier. A pre-potential applying means for applying a potential having a polarity opposite to the transfer potential to the surface opposite to the surface, or
A pre-potential applying means for applying a potential having a polarity opposite to the transfer potential to at least the surface opposite to the adsorption surface of the transfer material carrier before the transfer, upstream of the transfer position, so that the pre-potential applying device also serves as the transfer material carrier discharging means. Since the configured pre-potential applying means is provided, the potential of the transfer material carrier after transfer is suppressed by that much, and the voltage applied to the transfer potential applying means during multiple transfer excessively increases. As a result, a leak current in the transfer potential applying means is reduced, efficient transfer charging can be performed, and desired transfer characteristics can be obtained. further,
The transfer potential applying means can be small.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a multiple transfer device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating the state of the potential on the inner surface of a transfer drum in a cycle before, after suction, after each transfer, and before suction of plain paper.

FIG. 3 is a view similar to FIG. 2 showing a film for OHP.

FIG. 4 is a view similar to FIG. 1 for explaining the operation of the conventional multiple transfer device of the color electrophotographic apparatus.

[Explanation of symbols]

P: copy paper, 1: photosensitive drum, 2: transfer drum, 3 ...
Deflector roll, 4 ... adsorption corotron, 5 ... transfer corotron, 6 ... peeling claw, 7 ... static elimination corotron, 8 ... cleaning means, 9 ... paper static elimination corotron, 71 ... outer static elimination corotron, 72 ... inner static elimination corotron

Claims (4)

(57) [Claims] 1. A transfer material carrier made of a sheet-shaped dielectric material, which at least absorbs a transfer material for superimposing and superimposing a toner image obtained by visualizing an electrostatic latent image and conveys it to a transfer position. When, in the multiple transfer device in a transfer material carrying member of the suction surface opposite the image forming apparatus comprising a transfer potential applying means for applying a transfer potential on the surface of the transfer position, rolling
With adsorption potential for adsorbing copying material to the transfer material carrier
Multiple transfer in the image forming apparatus characterized in that a pre-potential applying means for applying a transfer potential and opposite polarity of the potential on the surface opposite to the suction surface of the at least the pre-transfer of the transfer material bearing member upstream of the given means apparatus. 2. A toner in which at least an electrostatic latent image is visualized.
-Adsorption of transfer material for superimposing and transferring multiple images
Transfer consisting of a sheet-like dielectric that is transported to the transfer position
The transfer material carrier and the transfer material support at the transfer position.
Transfer potential applying means for applying a transfer potential to the opposite surface
In a multiple transfer device in an image forming apparatus comprising
Adsorption of the transfer material carrier at least before the transfer position upstream of the transfer position
A process for applying a potential having a polarity opposite to the transfer potential to the surface opposite to the surface.
A multi-transfer device in an image forming apparatus, further comprising a re-potential applying unit , wherein the pre-potential applying unit also serves as a transfer material carrier discharging unit. 3. The pre-potential applying means is capable of adjusting an applied potential.
A multiple transfer device in the image forming apparatus described in the above. 4. The multi-transfer device according to claim 1, wherein the transfer material carrier comprises a transfer drum.