JPH05333708A - Multiple image forming device - Google Patents

Abstract

PURPOSE:To obtain a color image of high quality where the color balance is regulated by solving the problem of transfer memory due to impression of transfer bias at the time of attraction which is often generated in a transfer body utilizing a solid drum and also keeping down unevenness in transfer efficiency generated when the transfer memory is resolved. CONSTITUTION:The voltage of transfer or attraction bias is controlled so that surface potential of the transfer material 1 when the transfer material 1 is carried to an image transfer part is constantly a fixed value during rotation for the first color in a part from leading tip of the transfer material 1 to (1) along the carried direction of the transfer material 1 and in a part which is attracted by attraction bias and transfer bias, that is, in a part from circumference length (1) to an end of the transfer material when the part which is attracted only by attraction bias of the transfer material 1 carried to the image transfer part, that is the circumference length is made to be (1) from an attraction roll 15 to the image transfer part of the transfer body 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer material carried on a movable transfer material carrier, which is a visible image formed on the image carrier by an electrophotographic process or an electrostatic recording process. The present invention relates to an image forming apparatus that transfers a plurality of times to obtain a multiple image.

[0002]

2. Description of the Related Art As such a color image forming apparatus, an electrophotographic color image forming apparatus as shown in FIG. 6 has been widely used. The following is a brief description.

In the electrophotographic color image forming apparatus of this example,
The electrophotographic photosensitive drum 4 serving as an image carrier is uniformly charged by a primary charger 14 such as a roller or a corona charger. Then, the electrostatic latent image of the first color formed on the image carrier by the exposure 16 based on the image signal of the first color from the exposure device including the light emitting element 13 such as a laser and an LED is subjected to, for example, yellow (Y) development. It is visualized by the developing device 2a containing the agent.

On the other hand, as will be understood by also referring to FIG. 7A, a drum frame (housing) 3a constituted by a cylindrical member arranged at both ends and a connecting member 3e for connecting both cylindrical members 3d. A transfer material which is a flexible sheet represented by, for example, polyethylene terephthalate (PET), polyvinylidene fluoride (PVdF), fluorinated ethylene propylene copolymer (FEP), or the like in the notch of the outer peripheral surface of The drum-shaped transfer body 3 configured by stretching the support body 3b is obtained, for example, by holding the leading end of the supplied transfer material 1 by a gripper 3c or the like as a transfer material holding means and then rotating it. The transfer material 1 is wound around the surface of the transfer body. At this time, the transfer material 1 is sandwiched between a suction member 15 such as a grounded suction roller and a flexible sheet 3b forming the surface of the transfer body, and at the same time, the flexible sheet 3b is charged by the suction charger 7. It is held on the surface of the transfer body 3 by the electrostatic attraction force due to the electric charges applied to the back surface. Then, the transfer material 1 is conveyed to the image transfer area at a position facing the photosensitive drum 4 by the rotation of the transfer body 3, and the visible image formed on the photosensitive drum 4 is transferred by the transfer charger 8. ..

After that, the residual developer remaining on the photosensitive drum 4 is removed by the cleaner 5, and is again uniformly charged by the primary charger 14, and the photosensitive drum 4 is exposed on the photosensitive drum 4 by the exposure device. An electrostatic latent image is formed based on the image signals of the colors. This electrostatic latent image is, for example, a developing device 2b containing a magenta (M) developer corresponding to the image signal of the second color.
To develop a visible image.

The visible image of the second color is again transferred by the transfer charger 8 onto the transfer material 1 on the transfer body 3 onto which the visible image of the first color has been transferred. The above process is carried out by using a developer such as cyan (C) as the third color and black (BK) as the fourth color, and a visible image of the third and fourth colors is formed on the photosensitive drum 4, and the second and third colors are formed. The image is transferred onto the transfer material 1 on the transfer body 3 in the same manner as the visible image.

The transfer material 1 on which the color visible images of each color are transferred as described above is conveyed by the rotation of the transfer body 3 to the separation charger 9 disposed inside and outside the transfer body 3 so as to face each other.
The electrostatic charging force between the transfer material 1 and the flexible sheet 3b is removed by the separation charging device 9, and the transfer material 3 is separated by the separation claw 11 while being discharged by the separation discharging charger 10.
The separated transfer material 1 is guided to the fixing device 6 by the transfer material conveying path and fixed by the fixing device 6.

After the transfer material 1 is separated, the transfer body 3 has a developer cleaner (not shown) that removes the developer adhering to the flexible sheet 3b forming the surface thereof, and the sheet 3 is opposed to the transfer sheet 3. The pair of sheet charge-eliminating chargers 12 provided to eliminate the charge and electrically initialize it.

As described above, the mode in which the drum-shaped transfer body having the cutout structure is used as the transfer body used in the case of forming a color image by the multiple transfer system has been described.
A method of applying a bias to the transfer body 3 having a structure in which the conductive drum casing 3a having no notch portion 3e ((A) of FIG. 7) as shown in (B) is covered with the flexible sheet 3b as described above. Also by the above, multiple transfer similar to that of the notch structure transfer drum can be performed. In this type of transfer body 3,
Since the inside of the transfer body 3 having the cutout structure can be simplified, the cost can be reduced, and the flexible sheet 3b is supported by the entire drum from the inside. There is an advantage that deformation and damage of a certain sheet can be reduced. Therefore, a color image forming apparatus using a conductive drum (hereinafter referred to as "solid drum") having no cutout portion is currently receiving attention.

The image forming method of the color image forming apparatus using the solid drum as the transfer body 3 is very similar to the color image forming apparatus using the cutout drum described above. Image formation of the color image forming apparatus will be described below with reference to FIG. 8. Among the image forming means shown in FIG. 8, the color image forming apparatus shown in FIG. For the items, detailed description will be omitted by making the names and reference numerals the same.

First, the transfer material 1 supplied from the transfer material conveying path is sandwiched between the transfer body 3 and the suction roller 15 by the suction roller 15 which comes in contact with and separates from the transfer body 3. At the same time, a DC voltage is applied to the drum casing 3a as a suction and transfer bias for the first color, and the transfer material 1 and the transfer member 3 are caused by the electric charge from the suction roller 15 induced thereby.
It is held by electrostatic attraction. At this time, the amount of charges injected into the transfer material 1 becomes smaller than the amount of charges when the electrostatic capacities of the transfer material 1 and the flexible sheet 3b are sufficiently charged with the same bias. This is because when the charge is injected into the transfer material 1 by the suction roller 15, the transfer body 3 carrying the transfer material 1 is rotating, so that the contact time with the suction roller 15 for injecting the charge is short and the charge injection is performed. Is insufficient, therefore
Because the charge injection is incomplete, the surface potential of the transfer material 1 that has passed through the attraction roller 15 indicates the bias polarity applied to the transfer body 3. Therefore, the polarity of the bias applied to the transfer body 3 is set on the image carrier 4. If the polarity is set so that the visible image can be easily transferred, good transfer can be performed by setting the size appropriately.

In this way, the transfer material 1 held by the transfer body 3 is conveyed to the image transfer portion by the rotation of the transfer body 3, and the first color visible image formed on the image carrier 4 is transferred. It Next, when transferring the visible image of the second color, the bias value described above is changed to correct the surface potential that has dropped due to the transfer material 1 on the transfer body 3 transferring the visible image of the first color. Such correction is similarly performed at the time of transferring the third and fourth colors, and the visible image formed on the image carrier 4 is transferred onto the transfer material 1 on the transfer body 3 in an overlapping manner.

The transfer material 1 which has completed the above-mentioned transfer process is destaticized by the separation charging device 9 to remove the electrostatic adsorption force between the transfer material 1 and the transfer body 3, and the transfer material 3 carrying it is separated and discharged. The charger 10 separates while suppressing the peeling discharge. Then, the visible image formed on the transfer material 1 is fixed by the fixing device 6 and becomes a permanent image.

The transfer process in the color image forming apparatus using the solid drum has been described above. The developing process in this color image forming apparatus is performed in the color image forming apparatus using the cutout drum shown in FIG. The process is the same.

[0015]

In the color image forming apparatus as described above, the image carrier 4 is in contact with the transfer body 3 which holds and conveys the transfer material 1, or the thickness of the transfer material 1 to be used. They are arranged with a minute interval (about 50 to 300 μm). This is because the developer that forms the visible image on the image carrier 4 is efficiently transferred to the transfer material 1. However, when the developer is not on the image carrier 4, When a potential difference of several hundreds to several KV is generated between the surface of the image carrier 4 and the surface of the image carrier 3, electric discharge or the like occurs due to the minute distance between the surface of the image carrier 4 and the surface of the image carrier 4, and Also, a phenomenon occurs in which charges of opposite polarities move on the transfer body 3. This movement of charges often occurs especially when a transfer bias is applied while the transfer material 1 is not held on the transfer body 3. For example, in the reversal development method using a negative toner, in the above-mentioned state, since the polarity of the transfer bias on the image carrier 4 is positive, the image carrier 4 is uniformly charged with a negative charge. As a result, many positive charges move. If the amount of the positive charge that has moved to the image carrier 4 is small, it is removed by the primary charger 14 that is located downstream of the transfer portion of the image carrier 4 in the rotational direction. When it exceeds the limit, the mobility of the photosensitive layer forming the surface of the image carrier 4 with respect to the positive charge is limited, so that it cannot be removed even if the bias applied to the primary charger 14 is increased.
The positive charge that cannot be removed by the primary charger 14 is
The surface potential on the image carrier 4 after the primary charging is disturbed, and it appears in an image formed as a so-called transfer memory at the time of the next image formation.

Particularly, in the above-described solid drum transfer body 3, since the transfer material 1 is also electrostatically attracted by the transfer bias of the first color, the transfer bias is applied at the notch drum (see FIG. 7). (In the case of (A)) is the transfer material 1
This is when the front end is conveyed to the image transfer portion, whereas in this solid drum, the transfer material 3 located upstream of the image transfer portion in the rotational direction of the transfer material 3 and the suction roller 15 are attracted by the transfer material. This is when the front end of the transfer material 1 is conveyed to the section. Therefore, in the transfer body 3 of the solid drum in which the transfer bias is applied to the entire surface of the transfer body 3, unlike the transfer body 3 using the cutout drum, the portion of the transfer body 3 indicated by L _tr in FIG. A potential difference of several KV is generated between the image carrier 4 and the surface of the transfer body 3 at the part of L _pho on the image carrier 4 corresponding to, and the transfer of charges from the transfer body on the image carrier as described above. There is a drawback that the memory that causes it is likely to occur.

In order to solve the above problems, as shown in FIG. 9, the attraction roller 15 is not grounded, and an attraction bias power source 18 for attracting the transfer material 1 is provided separately from the transfer bias power source 17. As in the case of the transfer member 3 provided on the suction roller 15, the transfer bias may be applied immediately before the leading end of the transfer material 1 rushes into the image transfer portion, as in the case of the transfer body 3 using the cutout drum. However, although this solves the transfer memory due to the transfer of electric charges described above, FIG.
As shown in (C), a new problem arises in that the surface potential of the transfer material 1 conveyed to the image transfer section is greatly different between the front end and the rear end of the transfer material 1. This is because, when the transfer material 1 is attracted, the potential of the transfer body 3, which is the opposite pole of the attraction roller 15, changes due to the application of the transfer bias during the step of attracting the transfer material 1. There is.

10A and 10B show the application timing of each bias, and FIG. 10C shows the change in the surface potential of the transfer material immediately before the transfer position. Further, the time t has the following relationship when the distance between the transfer material adsorbing portion and the image transfer portion on the peripheral surface of the transfer body is 1, the rotational angular velocity of the transfer body is ω, and the radius of the transfer body is r. ..

L = rωt In the above method, the length L _p of the transfer material 1 in the conveying direction is larger than the distance (l) between the transfer material adsorbing portion and the image transfer portion on the peripheral surface of the transfer material. When the front end of the transfer material 1 is conveyed to the image transfer portion, the transfer material 1 is still electrostatically adsorbed at its rear end portion by the transfer material adsorbing portion. That is, when the transfer bias is applied, the potential difference V _tr-abh between the output V _tr of the attraction bias power supply 18 and the output V _abh of the transfer bias power supply 17 is the difference δ before and after the application of the transfer bias.
The potential fluctuation of V _tr-abh occurs, and as a result, the charge amount Q injected into the transfer material 1 changes at the _front end and the rear end of the transfer material.

In general, as the polarity of the attraction bias, the developer is charged so that the attraction charge injected in the attraction process is not canceled by the charge (that is, the developer) injected every time an image is transferred. Have the same polarity. Therefore, when the transfer and attraction bias power supply circuit as in the conventional example is used, the transfer material 1 after the transfer bias is applied.
The amount of charge Q ₂ injected into the device is the amount of charge injected during adsorption when the transfer bias is not applied, because the difference δV _tr-abh between the output terminal potential difference V _tr-abh of the transfer bias and the adsorption bias is generated. It will increase from Q _l . That is, the surface potential of the portion A from the front end of the transfer material 1 to the same length (l) as the distance 1 on the peripheral surface of the transfer body along the conveying direction is V.
_A , similarly, when the surface potential of the portion B located downstream in the transport direction from the length (l) of the transfer material 1 is V _B , the difference δQ _{1-2 in the} amount of injected charges described above causes a difference in both surface potentials. δV _AB
Minutes will occur. As a result, the surface potential of the transfer body 3 at the time of transferring the first color can be different by about several hundreds to several KV between the front end and the rear end of the transfer material 1. This difference in surface potential is different from the front end of the transfer material 1. This causes a large change in the transfer efficiency at the rear end. Particularly in color images, the uniformity of contrast or the like is more likely to be a problem than in monochrome images, and the partial change in transfer efficiency as described above becomes a major cause of impairing color balance.

An object of the present invention is to solve a transfer memory by applying a transfer bias at the time of adsorption, which often occurs in a transfer body using a solid drum, and also to improve transfer efficiency unevenness which occurs when the transfer memory is solved. It is an object of the present invention to provide a multiplex image forming apparatus capable of suppressing multiple occurrences and obtaining high quality multiplex images.

Another object is to provide a high quality color image forming apparatus by suppressing unevenness of color toner when different color toners are used for this multiplex image.

Another object of the present invention is to provide a high-quality full-color image forming apparatus which suppresses unevenness of each color toner in an apparatus for forming a full-color image by using yellow, magenta and cyan toners as the color toners. ..

[0024]

SUMMARY OF THE INVENTION The present invention to achieve the above object is a multiple image forming apparatus for forming multiple images by superposing different toner images on a transfer material and forming an image.
A unit for forming a toner image on the image carrier, a transfer member that is arranged so as to face the image carrier and that moves in synchronization with the toner image on the image carrier while supporting the transfer material, and a transfer member that is transferred to the transfer member. A transfer material supplying means for supplying a material, a transfer bias power source for applying a bias voltage for transfer to the transfer material, and an adsorption member for pressing the transfer material on the transfer material to adsorb the transfer material on the transfer material. , A suction bias power source for applying a bias voltage to the suction member, and when the transfer bias power source is applied, in a direction in which a potential difference does not occur in the surface potential of the transfer member due to the influence of turning the suction bias power source on and off. The voltage of the suction bias power supply is switched in consideration of the timing of turning on / off the transfer bias power supply, or when the transfer bias power supply is applied, it is changed by the influence of turning on / off the power supply of the suction bias power supply. In a direction that does not cause a potential difference on the surface potential of the body, it is intended to switch the voltage of the transfer bias power source considering incoming-cut timing of attraction bias power supply.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color image forming apparatus according to the present invention will be described in detail below with reference to the drawings. FIG. 1 illustrates a mode in which the present invention is embodied in the electrophotographic color image forming apparatus described above with reference to FIGS. 8 and 9. However, a configuration and operation similar to those of the conventional example are shown. The same numbers are attached and detailed description is omitted. In this embodiment, the transfer body 3 is a solid drum having the same structure as that described with reference to FIG. That is, the transfer body 3 is a transfer body having a drum structure in which the outer peripheral surface of the cylindrical conductive drum housing 3a having no cutout portion is covered with the dielectric flexible sheet 3b. In some cases, the transfer body 3 may have a configuration in which a drum casing 3a having no cutout portion is covered with a flexible sheet 3b coated with a conductive substance as an electrode on the drum casing 3a side.

In the present embodiment, the attraction bias power supply 18 for applying the attraction bias to the attraction member 15 such as the attraction roller is different from the above-mentioned conventional example in that the reference electrode of the attraction bias power supply 18 is not grounded. , And is connected to the output terminal of the transfer bias power supply 17. The color image forming process in this embodiment will be described below.

First, the transfer material 1 supplied from the transfer material conveying path is transferred to the transfer body 3 and the suction roller 15 which comes into contact with and separates from the transfer body 3.
In the transfer material attracting portion which is in contact with the transfer material, it is sandwiched between the attracting roller 15 and the transfer body 3 and electrostatically attracted to the transfer body surface by the attracting roller 15 to which a suction bias is applied from the tip of the transfer material. At this time, the transfer bias is not applied to the transfer body 3, and the transfer body 3 is grounded via the circuit of the transfer bias power supply 17.

Subsequently, the transfer material 1 electrostatically attracted to the transfer body 3
Is conveyed to the image transfer portion by the rotation of the transfer body 3, and the surface potential thereof is up to a voltage (about 1 KV) at which the transfer of the first color can be favorably performed by the transfer bias of the first color applied immediately before the image transfer portion. To raise. Then, by applying the transfer bias, the visible image on the image carrier 4 is electrostatically transferred onto the transfer material 1. At this time, the suction bias power source 1 applying the suction bias to the suction roller 15
Since the output potential of the transfer bias power source 17 is used as the reference potential by switching the switch SW, the output voltage 8 of the adsorption bias is necessarily varied to the opposite polarity side with respect to the ground.

As a result, the potential difference V _tr-abh between the output terminals of the transfer bias power supply 17 and the suction bias power supply 18 does not fluctuate before and after the transfer bias of the first color is applied, and the transfer roller from the suction roller onto the transfer material causes transfer unevenness. Injection charge Q
Can always be constant. Therefore, the surface potential of the transfer material 1 that rushes into the image transfer portion is always kept constant, and it is possible to prevent transfer defects due to variations in the surface potential of the transfer material 1.

After that, as described in the conventional example, the transfer material 1 is transferred by superimposing the visible images of the second and third colors from the image carrier 4 and separated from the transfer body 3 by the separation charger 9.
It is fixed by the fixing device 6 to form a permanent image. The transfer bias at the time of transferring the second color and the third color is applied with a transfer bias higher than or equal to the transfer bias value of the first color so that the transfer of the second color and the third color can be performed favorably.

FIG. 2 shows changes in the output voltage of the transfer and attraction bias power supplies 17 and 18 in the image forming process of the present invention and changes in the surface potential of the transfer material 1 immediately before the image transfer portion.

Note that FIG. 2 is similar to FIG.
(A) and (B) show the application timing of each bias, while (C) shows the change in the surface potential of the transfer material immediately before the transfer position.

FIG. 3 is a schematic sectional view of a color image forming apparatus to which the second embodiment of the present invention is applied. In this embodiment, unlike the above-described embodiments, the attraction bias power source 18
Is grounded, and the adsorption bias power supply 18 is connected at a predetermined timing.
A bias power supply circuit that can change the value of the output voltage of the above when changing the image of the first color is used. In this embodiment, when the transfer bias is applied, the transfer before and after the transfer bias is applied and the potential difference V between the output terminals of the attraction bias power supplies 17 and 18 is V.
_The adsorption bias is changed by an amount corresponding to the difference δV _tr-abh of _tr-abh . That is, similar to the above-described embodiment, even when the transfer bias is applied, the attraction bias power supply is maintained so that the potential difference V _tr-abh between the output terminals of the transfer bias power supply 17 and the attraction bias power supply 18 is always kept constant. The output value of 18 is changed. Therefore, the transfer material 1 is always injected with a constant adsorption charge amount Q ₁ from the adsorption roller 15, and the transfer material 1 is conveyed to the image transfer portion regardless of whether or not the transfer bias is applied during the adsorption. The surface potential is constant at this time.

This embodiment differs from the above-mentioned embodiment in that
It is necessary to change the attraction bias at a predetermined timing t when transferring the first color image, but since the attraction bias power supply 18 is grounded, a more stable attraction bias can be supplied at a lower cost than the attraction bias power supply of the above-described embodiment. There are advantages.

In the image forming process of this embodiment,
The changes in the output voltage of the transfer and suction biases are the same as those in the above-described embodiment shown in FIG. 2, but the time t indicating the timing of changing the suction bias in the figure is the transfer from the suction roller contact position to the image transfer portion. When the distance on the body circumferential surface is 1, the radius of the transfer body 3 is r, and the rotational angular velocity of the transfer body 3 is ω,
It can be expressed by the following formula (1).

T = distance (l) / rω (1) FIG. 4 shows a color image forming apparatus to which the third embodiment of the present invention is applied. In this embodiment, unlike the above-described embodiments, the transfer bias power source 1 is used instead of the attraction bias power source 18.
The output value of the output signal 7 can be changed stepwise according to an external signal.

In this embodiment, when the peripheral length on the transfer body 3 from the suction roller 15 to the image transfer portion is 1 in the area A of the transfer material 1, the transfer direction of the transfer material 1 from the front end of the transfer material 1 Along with the surface potential V _A of the portion up to the perimeter l) and a portion B of the transfer material 1 (a distance 2 which is twice the perimeter l from the tip of the transfer material).
surface potential V _B of the surface potential V _B (up to 1) δV
The output voltage is changed so as to be superimposed on the transfer bias when the portion B of the transfer material 1 rushes into the above-mentioned image transfer portion by the rotation of the transfer member 3 by the amount _AB .

By the way, in the image forming process in the color image forming apparatus using this embodiment, since the transfer bias of the first color changes during the same transfer process, the surface potential difference δV _AB is also the length of the transfer material 1. L _P is the above-mentioned transfer body 3
When there is a relationship as shown in equation (2) with the above distance l,
It is controlled so as to change in n steps during the same image transfer.

L _P ≦ n × distance (l) (n is 1, 2, 3, 4, ...) (2) Further, in the present embodiment, the value of the transfer bias for the second and subsequent colors is also:
Unlike the above-described embodiment, like the transfer bias of the first color,
When the transfer bias of the first color changes by n steps, it changes by n steps during the same transfer process.

As a result, the transfer material 1 plunges into the image transfer portion.
The surface potential is constantly kept constant, and transfer defects due to variations in the surface potential of the transfer material 1 can be prevented. FIG. 5 shows a transfer / adsorption bias power source 1 in the image forming process of the present invention.
Change in output voltage of Nos. 7 and 18 and transfer material 1 immediately before image transfer section
The case where n = 2 in the above equation (2) of the change of the surface potential is shown.

Note that FIG. 5 is similar to FIG.
(A) and (B) show the timing of each bias,
(C) shows a change in the surface potential of the transfer material immediately before the transfer position.

Here, δV _BC is the surface potential V _C of the portion C of the transfer material 1 (the portion from the distance of 21 from the leading end of the transfer material to the rear end of the transfer material) and the surface potential V _B. Is the difference in the surface potential of the.

In the present embodiment, unlike the above-mentioned embodiment, it is necessary to change the transfer bias in multiple stages, but only by increasing the variable width and timing of the transfer bias power source, which originally changed the output value for each color. Therefore, for example, when using the transfer bias power supply as shown in FIG. 11, it is only necessary to change the control method of the output value of the transfer bias power supply, and it is not necessary to control the output value of the suction bias power supply, so that the device configuration is simple. It can be anything.

In the above embodiment, the suction member 1
As an example of No. 5, a roller which comes into contact with and separates from the transfer body 3 has been illustrated, but any other member which comes into contact with and separates from the transfer member 3 and presses it similarly, such as a brush or an elastic plate, may be used.

Further, the toner image transferred to the transfer material may be a multiple image of two color toners of red and black in addition to the yellow, magenta and cyan toners.

As described above, the multiple image forming apparatus according to the present invention uses the power supply circuit for controlling the transfer and the attraction bias so that the surface potential of the transfer material on the transfer body becomes constant. The surface potential of the transfer material when the transfer material is conveyed to the image transfer section is determined by the first part of the transfer material conveyed to the It is possible to keep a constant value during the rotation of the solid drum. Therefore, it is possible to suppress the unevenness of the transfer efficiency that occurs when solving the transfer memory in the transfer body using the solid drum, and it is possible to obtain a high quality multiplexed image. Can be obtained. Furthermore, if the transferred image is a full-color image, the effect is even greater.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a color image forming apparatus according to the present invention.

2A, 2B, and 2C are diagrams showing the output values of a transfer bias power supply and an attraction bias power supply, and the surface potential of a transfer material conveyed to an image transfer unit.

FIG. 3 is a schematic configuration diagram of another embodiment of the color image forming apparatus according to the present invention.

FIG. 4 is a schematic configuration diagram of still another embodiment of the color image forming apparatus according to the present invention.

5A, 5B, and 5C are diagrams showing the output values of a transfer bias power supply and an attraction bias power supply, and the surface potential of a transfer material conveyed to an image transfer unit.

FIG. 6 is a schematic configuration diagram of a conventional color image forming apparatus.

FIG. 7 is a perspective view of a transfer body.

FIG. 8 is a schematic configuration diagram of a conventional color image forming apparatus.

FIG. 9 is a schematic configuration diagram of a conventional color image forming apparatus.

10A, 10B, and 10C are diagrams showing the output values of the transfer bias power supply and the suction bias power supply and the surface potential of the transfer material conveyed to the image transfer unit in the conventional apparatus. is there.

FIG. 11 is a block diagram of a conventional transfer bias power supply.

[Explanation of symbols]

 1 Transfer Material 2 Developing Device 3 Transfer Body 4 Image Carrier 17 Transfer Bias Power Supply 18 Adsorption Bias Power Supply

Claims (2)

[Claims] 1. A multiple image forming apparatus for forming multiple images by superimposing different toner images on a transfer material, the image carrier, means for forming a toner image on the image carrier, and the image carrier. A transfer body which is arranged so as to face the body and which moves in synchronization with the toner image on the image carrier while supporting the transfer material; a transfer material supply means for supplying the transfer material to the transfer body; A transfer bias power source for applying a bias voltage to the transfer body, a suction member for pressing the transfer material onto the transfer body to attract the transfer material to the transfer body, and a suction bias power supply for applying a bias voltage to the suction member. When the transfer bias power supply is applied, the voltage of the suction bias power supply is set in a direction that does not cause a potential difference in the surface potential of the transfer body due to the influence of turning on / off the power supply of the suction bias.
The transfer bias power supply is switched in consideration of the on / off timing of the power supply. 2. A multiple image forming apparatus for forming different images by superposing different toner images on a transfer material, the image bearing member, means for forming a toner image on the image bearing member, and the image bearing member. A transfer body which is arranged so as to face the body and which moves in synchronization with the toner image on the image carrier while supporting the transfer material; a transfer material supply means for supplying the transfer material to the transfer body; A transfer bias power supply that applies a bias voltage for the transfer member, an adsorption member that presses the transfer material onto the transfer member to adsorb the transfer material to the transfer member, and an adsorption bias power supply that applies a bias voltage to the adsorption member. When the transfer bias power supply is applied, the voltage of the transfer bias power supply is turned on / off in a direction that does not cause a potential difference in the surface potential of the transfer body due to the effect of turning on / off the power supply of the suction bias. Ta It switched in consideration of the timing.