JP3253849B2 - Image forming device - Google Patents

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 such as a copying machine or a so-called laser printer for forming an image using a latent image formed on a photoreceptor by a laser. The present invention relates to an image forming apparatus for forming an image on a paper.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus for forming an image using a latent image formed on a photoreceptor by a light beam,
As a method of realizing a color image, generally four colors (yellow, cyan, magenta, and black) are sequentially formed on the intermediate transfer member.
A method of superimposing and transferring each of the toner images from the photoreceptor drum, and performing a batch transfer to a recording medium; and a method of holding the recording medium on a transfer body and sequentially printing the four color toner images directly on the recording medium. The method can be broadly divided into a method of superimposing and transferring from a photosensitive drum. However, in the former case, the transfer is performed twice from the photosensitive drum to the intermediate transfer member and from the intermediate transfer member to the recording medium. Therefore, when the transfer efficiency is low and the quality of the image and the speed of image formation are emphasized, Often employ the latter image forming method.

An image forming apparatus 70 according to the latter method includes, as shown in FIG. 12, a corona charger 72 for adsorbing a recording paper 78 as a recording medium inside a transfer drum 71 formed only of an insulating layer. A corona charger 74 for transferring the toner image formed on the surface of the photosensitive drum 73 to the recording paper 78 is separately provided, and the suction of the recording paper 78 and the transfer of the toner image to the recording paper 78 are performed separately. It is done separately.

However, the image forming apparatus 70 as described above
In the case, when the insulating layer of the transfer drum 71 is thick, the electric power required to generate a potential difference required for transfer and adsorption increases, and thus, conventionally, a single-layer structure of only a thin insulating layer is used. From the viewpoint of durability, there was a problem in durability. Also, in handling during replacement work, the insulator layer is easily damaged, and there is a problem in workability. In the above configuration, even if the thickness of the insulator layer is the same, the strength can be improved by reducing the outer diameter. However, in addition to the corona chargers 72 and 74, a corona charger for separation and static elimination is provided around the periphery. Since it is necessary to dispose the cleaning unit 75 and the cleaning unit 77, it is difficult to reduce the size of the transfer drum 71.

For example, US Pat. No. 5,276,490, "BURIED ELEC
TRODE DRUM FOR AN ELECTROPHOTOGRAPHIC PRINT ENGIN
E "uses a transfer drum having a configuration in which a plurality of electrodes extending in the axial direction are juxtaposed between an insulating support member and a resistive layer covering the surface thereof. The charging device provided around the drum can be simplified, but the transfer drum has difficulty in forming electrodes formed in the axial direction, and has a problem in mass productivity.

Japanese Patent Application Laid-Open No. 4-287070 discloses an "intermediate transfer drum for a color image forming apparatus" which discloses an intermediate transfer drum having a three-layer structure of a metal drum, a conductive sponge, and a dielectric film from the inside. Have been. In the above invention, the transfer from the photosensitive drum to the intermediate transfer drum and the transfer from the intermediate transfer drum to the recording paper are performed by a high-voltage power supply connected to the metal drum of the intermediate transfer drum. Then, the image forming apparatus 80 configured to directly transfer the image from the photosensitive drum to the recording paper is
As shown in FIG.

In the image forming apparatus 80 shown in FIG. 1, a transfer drum 84 has a three-layer structure of a metal drum 81, a conductive sponge 82, and a dielectric film 83 from the inside.
Then, by applying a voltage having a polarity opposite to that of the toner to the metal drum 81 of the transfer drum 84, adsorption of the recording paper 87 and transfer of the toner image are performed. In the above, the conveyed recording paper 87 is charged at a suction position P between the ground roller 85 and the transfer drum 84 that are grounded, and is electrostatically attracted to the transfer drum 84. Then, the attracted recording paper 87 is sent to a transfer position Q between the photosensitive drum 86 and the transfer drum 84, and the toner image on the photosensitive drum 86 is transferred to the recording paper 87.

In the above image forming apparatus, the metal drum 8
One recording medium 87 can be attracted to the transfer drum 84 and transferred from the photosensitive drum 86 to the recording paper 87 on the transfer drum 84 by one high-voltage power supply 88 connected to 1.

[0009]

However, when trying to realize the optimum image forming conditions on the recording paper, the potential difference required at the suction position P and the transfer position Q, that is, the potential difference between the transfer and the recording paper, The required potential difference is not always the same as in the case of adsorption. Of course, it differs depending on the thickness and material of the recording paper. Therefore, it is impossible to satisfy both at the same time by applying the same voltage.

However, in the above-described conventional configuration, the metal drum 81 is used, and the suction and the transfer are performed by one power supply. Therefore, when trying to realize a potential difference suitable for the suction and a potential difference suitable for the transfer, for example, , Two high-voltage power supplies connected to the metal drum 81 are prepared and switched,
Since the distance between the suction position P and the transfer position Q needs to be longer than the length of the recording paper of the maximum size that can be handled by the image forming apparatus, the outer diameter of the transfer drum 84 must be increased. . Further, even during continuous copying, the next recording paper cannot be attracted until the transfer to the immediately preceding recording paper is completed. Therefore, it is necessary to increase the distance between recording papers, and the copy speed decreases. There is also a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to make it possible to perform suction and transfer independently and in parallel so that suction and transfer at optimal voltage values can be performed. It is another object of the present invention to provide an image forming apparatus which does not increase the size and does not cause a reduction in copy speed.

[0012]

[Summary of the image forming apparatus according to a first aspect of the invention, in order to solve the above problems, the photosensitive member the toner image formed on the drum a drum-shaped recording medium holding member on 2. Description of the Related Art In an image forming apparatus that forms an image by transferring an image onto a recording medium that has been electrostatically attracted, the image forming apparatus is located at an opposing position across a recording medium holding member of a photoconductor drum, and transfers toner from the photoconductor drum to a recording medium. to a first electrode to form an electric field between the photosensitive drum provided at a position facing the third electrode provided on the outside of the record medium holding member, the recording medium holding member by a potential difference between the third electrode A second electrode for applying a charge for electrostatic attraction to the recording medium is provided so as to be in contact with the inside of the recording medium holding member, and the recording medium holding member is provided with at least an inner holding member main body. That Together they are configured from the side of the insulating layer, the volume resistivity of the composition of the holding member main body 10 ⁴ to 10 ⁸ [Omega] cm
Near between it is, and, between the holding member main body and the insulator layer
In addition, it exhibits rubber-like elasticity and has a volume resistivity of 10 ⁴ to 10
^An elastic body layer having a composition between ⁸ Ωcm is provided . With the above configuration, the transfer performed between the photosensitive drum and the first electrode and the suction performed between the second electrode and the third electrode can be performed independently without being affected by each other. become.

Further, according to the above configuration, the elastic layer is deformed at the time of pressing the photosensitive drum or the like for transferring the image onto the recording medium on the recording paper holding member, so that the adhesion to the recording medium is improved. Transfer efficiency can be improved.

According to a second aspect of the present invention, in order to solve the above-mentioned problem, in addition to the configuration of the first aspect , the outer surface of the third electrode has at least rubber-like elasticity. And the elastic body has a hardness smaller than that of the elastic body layer. According to the above configuration, the recording medium can be bent along the shape of the recording medium holding member, and the adhesion of the recording medium to the recording medium holding member can be improved.

According to a third aspect of the present invention, in order to solve the above-mentioned problems, in addition to the configuration according to the first or second aspect , the image forming apparatus is further provided with a potential difference required for transfer and electrostatic attraction. When a voltage is applied to the first electrode and the second electrode, the first electrode is inscribed in the recording medium holding member.
A ground electrode is provided between the electrode and the second electrode. Further, the image form according to the invention of claim 4 is provided.
In order to solve the above-mentioned problem, the forming device
Drum-shaped recording medium holding member for toner image formed thereon
Performs image formation by transferring to a recording medium electrostatically adsorbed on top
In an image forming apparatus, a recording medium holding unit of a photosensitive drum
At the opposite position with the material in between, and
Between the photoconductor drum and the
A first electrode for forming an electric field, and
The third electrode is provided at a position opposed to the third electrode, and the third electrode and
Electrostatic adsorption on the recording medium holding member due to the potential difference
And a second electrode for applying the electric charge of
One provided inside the recording medium holding member so as to be inscribed therein
On the other hand, the recording medium holding member has at least an inner holding portion.
It consists of a material body and an insulator layer on the outside,
The volume resistivity of the composition of the holding member body is between 10 ^{4 and} 10 ⁸ Ωcm
And provides the potential difference necessary for transfer and electrostatic attraction.
Preferably, a voltage is applied to the first electrode and the second electrode.
The first time so as to inscribe the recording medium holding member.
A ground electrode is provided between the electrode and the second electrode
It is characterized by. According to the above configuration, even when different voltages are applied to the first electrode and the second electrode by the ground electrode, the respective electrodes are not affected by each other's voltage, so that the appropriate transfer voltage and suction voltage can be maintained. Can be easily performed.

According to a fifth aspect of the present invention, there is provided an image forming apparatus according to the first, second, third, or fourth aspect.
In addition to the configuration described in the above, the third electrode is provided so as to be able to be separated from and attached to the recording medium holding member, and the third electrode is provided at a position on the recording medium holding member where the recording medium is not held.
The electrode is brought into contact with the recording medium holding member and the second
It is characterized in that a voltage having the same polarity as that at the time of electrostatic attraction is applied between the electrode and the third electrode. In addition, according to claim 6
An image forming apparatus according to the present invention is provided to solve the above-described problems.
Then, the toner image formed on the photosensitive drum is
Transfer to the recording medium electrostatically adsorbed on the recording medium holding member
Image forming apparatus for forming an image by
Is located at the opposite position with the recording medium holding member
To transfer the toner from the ram to the recording medium.
A first electrode for forming an electric field with the body drum, and a recording medium
Provided at a position facing a third electrode provided outside the holding member
And a static potential is applied to the recording medium holding member by a potential difference from the third electrode.
A second electrode for applying a charge for electroadsorption to the recording medium;
However, all of them are inscribed inside the recording medium holding member.
While the recording medium holding member is less
Both are composed of the inner holding member body and the outer insulator layer
And the volume resistivity of the composition of the holding member body is 10
⁴ to 10 ⁸ Ωcm, and the third electrode is a recording medium.
The recording medium is provided so as to be detachable from the body holding member.
In the position where the recording medium is not held on the body holding member
And bringing the third electrode into contact with the recording medium holding member.
And the same polarity between the second electrode and the third electrode as when electrostatically attracted.
Is applied. According to the above configuration, even if the toner adheres to the third electrode, the toner adheres to the recording medium holding material side due to the electric field formed between the second electrode and the third electrode. Becomes possible.

According to a seventh aspect of the present invention, in order to solve the above-mentioned problem, in addition to the configuration of any one of the first to sixth aspects, the image forming apparatus further comprises a plurality of colors around the photosensitive drum. A developing device is provided to perform image formation by performing development on a photosensitive drum and transfer to a recording medium for each color, and in the recording medium holding member, for each of the transfer, It is characterized in that the tip of the moving direction is sucked. An image according to the invention of claim 8
In order to solve the above problems, the forming apparatus
The drum-shaped recording medium holding unit
Transfer to a recording medium electrostatically adsorbed on a recording material to form an image.
In an image forming apparatus, a recording medium is held on a photosensitive drum.
At the opposite position with the member in between, and
Between the photosensitive drum to transfer toner to the body
A first electrode for forming an electric field with the recording medium holding member;
A third electrode provided at a position facing the third electrode provided at
Electrostatic adsorption on the recording medium holding member due to the potential difference between
And a second electrode for applying a charge to the recording medium
Provided so as to be inscribed inside the recording medium holding member
On the other hand, the recording medium holding member is
It is composed of a member body and an insulator layer
In addition, the volume resistivity of the composition of the holding member body is 10 ⁴ to 10 ⁸ Ωcm
Multi-color development between the photoreceptor drums
A device is provided to develop the photoreceptor drum for each color.
And transfer to a recording medium to form an image
In the recording medium holding member, for each transfer,
Features to adsorb the leading end of the recording medium in the moving direction
And With the above configuration, the suction of the leading end portion of the recording medium is performed for each transfer, so that even if the recording medium is hard to be suctioned or a hard recording medium, the suction force is not reduced and a stable suction state can be maintained. it can.

According to a ninth aspect of the present invention, in order to solve the above-mentioned problem, in addition to the configuration according to any one of the first to eighth aspects, a plurality of colors are provided around the photosensitive drum. The developing device is provided to perform image development by performing development on a photosensitive drum and transfer to a recording medium for each color, and a developing device that is located at an opposing position across a recording medium holding member of the photosensitive drum. The one electrode is movable in a direction parallel to a moving direction of the recording medium with respect to a contact position between the photosensitive drum and the recording medium holding member while being in contact with the recording medium holding member. . Also, in claim 10
An image forming apparatus according to the present invention is provided to solve the above problems.
Then, the toner image formed on the photosensitive drum is
Transfer to the recording medium electrostatically adsorbed on the recording medium holding member
Image forming apparatus for forming an image by
Is located at the opposite position with the recording medium holding member
To transfer the toner from the ram to the recording medium.
A first electrode for forming an electric field with the body drum, and a recording medium
Provided at a position facing a third electrode provided outside the holding member
And a static potential is applied to the recording medium holding member by a potential difference from the third electrode.
A second electrode for applying a charge for electroadsorption to the recording medium;
However, all of them are inscribed inside the recording medium holding member.
While the recording medium holding member is less
Both are composed of the inner holding member body and the outer insulator layer
And the volume resistivity of the composition of the holding member body is 10
^{Between 4 and} 10 ⁸ Ωcm and around the photosensitive drum
A multi-color developing device is provided.
The image is formed by developing on the ram and transferring to the recording medium.
While holding the recording medium holding member of the photosensitive drum.
The first electrode at the opposing position is inscribed in the recording medium holding member.
Contact position between the photosensitive drum and the recording medium holding member
Can move in the direction parallel to the direction of movement of the recording medium
It is characterized by that. According to the above configuration, the applied voltage at the transfer position can be adjusted according to the toner of each color without changing the applied voltage itself applied to the first electrode.

An image forming apparatus according to an eleventh aspect of the present invention comprises:
In order to solve the above problem, in addition to the configuration according to any one of claims 1 to 6, a plurality of photosensitive drums for developing different colors are provided, and a recording medium holding of each photosensitive drum is provided. A first electrode is provided at a position facing the member. Also, billing
An image forming apparatus according to the invention of Item 12 solves the above problem.
The toner image formed on the photoreceptor drum.
Recording medium electrostatically adsorbed on a ram-shaped recording medium holding member
In an image forming apparatus that transfers an image to an
At a position opposing the recording medium holding member of the body drum,
To transfer the toner from the photosensitive drum to the recording medium
A first electrode for forming an electric field between the photosensitive drum and the photosensitive drum;
Opposing position of a third electrode provided outside the recording medium holding member
And the recording medium is held by the potential difference from the third electrode.
A method of applying a charge to a recording medium for electrostatically adsorbing to a member
The two electrodes are both inside the recording medium holding member.
The recording medium holding member is provided so as to be in contact with the recording medium holding member.
But at least the inner holding member body and the outer insulator
And the volume of the composition of the holding member body
The resistivity is between 10 ^{4 and} 10 ⁸ Ωcm, and
With multiple photoreceptor drums to develop different colors
The opposing positions of each photosensitive drum with the recording medium holding member
A first electrode is provided in the device.
According to the above configuration, even when a plurality of colors are developed to form a color image, it is possible to perform the adsorption and the transfer of each color with optimal voltage values without reducing the speed of image formation.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment includes a sheet feeding unit 2 that stocks and supplies a recording sheet 6 (recording medium) on which an image is formed by toner, and a recording sheet 6 on which a toner image is formed. And a developing unit 4 for forming a toner image, and a fixing unit 5 for fusing and fixing the toner image transferred to the recording paper 6. Paper feed unit 2
A paper cassette 10 which is detachably provided at the lowermost stage of the main body, stocks the recording paper 6 and supplies it to the transfer section 3
And a manual paper feed unit 11 for manually feeding the recording paper 6 one by one from the front side of the main body of the image forming apparatus 1.

The paper feed unit 2 includes the paper feed cassette 1
Pickup roller 1 that feeds one by one from the top of 0
2 and a pre-feed roller (PF roller) 13 for conveying the recording paper 6 sent out by the pickup roller 12
And the manual feed roller 14 for transporting the recording paper 6 from the manual paper feed unit 11, and the recording paper 6 transported by the PF roller 13 and the manual feed roller 14 are temporarily stopped before the transfer unit 3 for timing. Registration roller 15
Are provided.

A delivery member 10a urged upward by a spring or the like is provided in the paper supply cassette 10, and the recording paper 6 is placed on the delivery member 10a. By the urging force, the paper feed cassette 1
The recording paper 6 at the uppermost part of the recording paper 6 comes into contact with the pickup roller 12, and is sent out to the PF roller 13 one by one as the pickup roller 12 rotates in the direction of the arrow, and is conveyed to the registration roller 15. On the other hand, the recording paper 6 supplied from the manual paper feed unit 11 is also conveyed to the registration roller 15 by the manual paper feed roller 14.

The transfer section 3 is provided with a transfer drum 16 having a flange made of an insulating member on both sides.
The transfer drum 16 is rotatably fixed in a state insulated from the main body frame by being attached to the main body of the image forming apparatus 1 via a bearing attached to the flange.

Around the transfer drum 16, a suction roller 17 for bringing the recording paper 6 into close contact with the transfer drum 16, a guide member 18 for guiding the recording paper 6 so as not to fall off the transfer drum 16, and a transfer drum 16 are attached to the transfer drum 16. A peeling claw 19 for forcibly peeling off the recording paper 6 is provided. In addition, the peeling claw 19 is provided so as to be able to freely contact and separate from the surface of the transfer drum 16. Also, on the inner surface of the transfer drum 16,
A transfer applying roller 20 for applying a transfer voltage to the transfer position X and a suction grounding roller 21 grounded at the suction position Y are arranged in contact with each other. The transfer applying roller 20 and the suction ground roller 21 in contact with the inner surface of the transfer drum 16 are covered with an elastic body for contact stability. In addition, since the transfer drum 16 attracts the recording paper 6 by the static electricity on the surface, a static eliminator 16a around the transfer drum 16 further removes electric charges charged on the surface of the transfer drum 16. A cleaning device 16b for removing toner and the like attached to the surface of the transfer drum 16 is provided. The structure of the transfer drum 16 will be described later in detail.

The developing section 4 is provided with a photosensitive drum 22 which is in pressure contact with the transfer drum 16. The photosensitive drum 22 is made of a grounded conductive aluminum tube, and has an OPC (Organic Photoconductive) on its surface.
Conductor) film is formed. Around the photosensitive drum 22, developing units 23, 2 storing yellow, magenta, cyan, and black toners, respectively.
4, 25, and 26 are arranged radially, and a charger 27 for charging the surface of the photosensitive drum 22, an inter-image eraser (not shown), and a cleaning device 28 for removing residual toner on the surface of the photosensitive drum 22 are provided. A toner image is formed on the photosensitive drum 22 for each color toner.

That is, in the photosensitive drum 22, 1
The charge, exposure, development, and transfer are repeated for each color. In the case of color transfer, one color of the recording paper 6 adsorbed on the transfer drum 16 is applied every time the transfer drum 16 makes one rotation. Toner images are transferred to the recording paper 6, and a maximum of 4
One color image is obtained by rotation. The light beam for exposing the surface of the photosensitive drum 22 is irradiated between the charger 27 and the developing unit 4.

In the fixing section 5, a fixing roller 29 for fusing the toner image at a predetermined temperature and pressure to fix it on the recording paper 6 is separated from the transfer drum 16 by a peeling claw 19 after the transfer of the toner image. The recording paper 6 is transferred to the fixing roller 29.
And a fixing guide 30 that guides the fixing device. A discharge roller 31 is provided downstream of the fixing unit 5 in the direction of conveyance of the recording paper 6, and discharges the fixed recording paper 6 from the apparatus main body onto a discharge tray 32.

Next, the structure of the transfer drum 16 will be described with reference to FIG. The transfer drum 16 is shown in FIG.
As shown in the figure, a drum body 40 made of a resin having a volume resistivity between a so-called conductor and an insulator (hereinafter referred to as a semiconductive resin) is filled with a conductive additive as a base material. Used, on the outer surface of this drum body 40,
Similarly, an elastic layer 41 made of urethane foam, silicon, or the like, which is filled with a conductive additive and has a volume resistivity between the conductor and the insulator, is provided. Further, the elastic layer 4
An insulator layer 42 made of polyvinylidene fluoride is provided on the outer surface of the substrate 1.

In this embodiment, the transfer drum 16
As shown in FIG. 2, the drum body 40 and the elastic layer 4
Although a three-layer structure having a single-layer structure and an insulator layer 42 is used, the present invention is not limited to the above. The insulator layer 42 is provided as the outermost layer, and the inner layer is constituted only by the drum body 40. Is also good.

As described above, by using the drum main body 40 made of a semiconductive resin for the inner layer, the adsorption and the transfer can be performed in parallel at different voltage values. However, regarding the drum body 40, in order to eliminate interference between transfer and adsorption, the volume resistivity of the semiconductive resin is 10 ⁴ to 10 ⁸ Ωcm.
It is necessary that the thickness be in the range of 1 to 30 mm in terms of securing rigidity and functionally. Also,
For the same reason as described above, the elastic layer 41 also has a volume resistivity of
It is necessary to be in the range of 10 ⁴ to 10 ⁸ Ωcm, and at the same time, the thickness is 1 to 10 mm to obtain a sufficient nip width.
Is preferably within the range.

On the other hand, for the insulating layer 42, the transfer drum 16 and the suction roller 17 or the photosensitive drum 22
It is necessary to have an appropriate charge holding power between the two. In general, the charge holding power, that is, the capacitance, is c = ε × s / d when the relative permittivity is ε, the area of the insulator layer is s, and the layer thickness is d. expressed.

From the above equation, it can be said that the smaller the thickness is, the larger the capacitance c can be. However, in consideration of the uniform layer thickness and the mass productivity and durability, the layer thickness d is 50
It is preferably about μm to 300 μm.

In the above equation, if the relative dielectric constant ε is small, the capacitance c is small, so that the transfer efficiency is improved, while the attraction force is small, and if the relative dielectric constant ε is large, the capacitance c is small. , The transfer efficiency is reduced, but the suction force is increased. Also, the magnitude of the layer thickness d gives the opposite result to the magnitude of the relative permittivity ε. That is, an appropriate range of the relative permittivity still exists for the above range of the layer thickness d.

At this time, if the resistance of the insulator layer 42 is too low, the toner on the photosensitive drum 22 moves between the photosensitive drum 22 and the transfer drum 16 based on the current component flowing when the toner moves to the recording paper 6 side. In the meantime, the current component flowing by the circuit contact that satisfies Ohm's law flows preferentially, so that the toner transferred to the recording paper 6 returns to the transfer drum 16 and re-transfer occurs, and conversely, the resistance is too high. And a current component flowing when the toner on the photosensitive drum 22 moves toward the recording paper 6 and a current component flowing due to a circuit contact between the photosensitive drum 22 and the transfer drum 16 that satisfies Ohm's law. Since it is difficult for both to flow, the amount of toner that cannot move to the recording paper 6 increases, and transfer failure occurs. Therefore, there is an appropriate volume resistivity with respect to the layer thickness.

It has been experimentally found that the insulating layer 42 preferably has a relative dielectric constant in the range of 8 to 12 and a volume resistivity of 10 ¹² to 10 ¹⁷ Ωcm. For example, the relative dielectric constant and the volume resistivity of the above-mentioned polyvinylidene fluoride satisfy the above conditions. Also,
If it satisfies the above range, it can be used as the insulator layer 42, and other examples include polyethylene terephthalate.

Next, the structure of the suction roller 17 will be described. Note that the following description will be made on the assumption that a negative polarity toner is used, but the same concept can be applied to a positive polarity toner. The suction roller 17 provided below the transfer drum 16 is applied with the same polarity as the toner, that is, a negative voltage by the high voltage power supply 17a shown in FIG. As a result, the recording paper 6 is
When passing through a suction position Y between the transfer drum 7 and the transfer drum 16, it is positively charged and electrostatically attracted onto the transfer drum 16.
The hardness of the surface of the suction roller 17 is determined by the transfer drum 16.
Is covered with an elastic body having a hardness smaller than the hardness of the elastic body layer 41. Accordingly, when the recording paper 6 passes through the suction position Y, the recording paper 6 is curled along the transfer drum 16 and the nip width can be increased, so that the suction time becomes longer. As a result, the adsorptivity can be improved.

After the application of the suction voltage to the entire surface of the recording paper 6 is completed, the suction roller 17 is separated from the transfer drum 16. This is to prevent the toner image electrostatically attached to the surface of the recording paper 6 from being disturbed when the recording paper 6 that has been attracted onto the transfer drum 16 and rotated once is pressed again against the attracting roller 17. It is.

The operation of separating the suction roller 17 from the transfer drum 16 is performed mechanically, for example, by disposing solenoids as driving means at both ends of the rotation center of the suction roller. Thus, a stable nip width at the suction position X and an appropriate separation amount of the suction roller 17 can be obtained.

Here, the operation of attracting and transferring the recording paper 6 by the transfer drum 16 will be described below with reference to FIGS. First, in the suction step of the recording paper 6, the recording paper 6 conveyed to the suction position Y between the suction roller 17 and the transfer drum 16 is conveyed while being pressed against the surface of the insulating layer 42 by the suction roller 17. At this time, the recording paper 6
Is given a curl along the transfer drum 16.

On the other hand, the charging in the adsorption step includes Paschen discharge and charge injection. A positive charge is induced on the surface of the insulator layer 42 by the negative suction voltage applied to the suction roller 17, and an electric field is generated from the transfer drum 16 toward the suction roller 17 as shown in FIG. Then, the transfer drum 16 and the suction roller 17 rotate, and the insulating layer 42
As the electric field strength increases, the so-called Paschen discharge occurs in the region (I) from the transfer drum 16 side to the suction roller 17 side.

Further, after the discharge, in the region (II),
Charge injection occurs from the suction roller 17 side to the transfer drum 16 side, and positive charges are accumulated on the surface of the transfer drum 16. That is, by the Paschen discharge and the charge injection, positive charges are accumulated inside the recording paper 6, that is, on the side of the contact surface with the insulator layer 42. Thus, the recording paper 6 is electrostatically attracted to the transfer drum 16. Then, the recording paper 6 attracted to the transfer drum 16 is transported to a transfer position X between the transfer drum 16 and the photosensitive drum 22 as the transfer drum 16 rotates in the direction of the arrow.

Next, in the transfer step of the recording paper 6, a toner image is formed on the surface of the photoreceptor drum 22 by a toner of negative polarity. When the recording paper 6 passes through the transfer position X, a reverse voltage to the toner, that is, a positive voltage is applied to the transfer applying roller 20 from the high-voltage power supply 20a shown in FIG. Is formed, and the toner image of the negative polarity toner is transferred to the recording paper 6 on the transfer drum 16. The transfer drum 16 and the photosensitive drum 22 are moved at the transfer position X.
It is pressed so as to have a predetermined nip width.

As described above, since the recording paper 6 is attracted and transferred by contacting instead of adsorbing and transferring the recording paper 6 by the conventional charge injection by air discharge, the voltage can be reduced, and the voltage can be easily controlled. Low driving energy is required. Further, as in the conventional case, the transfer drum 1 is
Since the surface of the transfer drum 16 can be stably charged as compared with the case where charge is induced on the surface of the recording paper 6, the adsorption and transfer of the recording paper 6 can be stably performed. Further, since the transfer drum 16 is charged by contact charging, even if the surface of the transfer drum 16 is scratched,
Since the electric field region does not change, the electric field balance is not disrupted at the flaws on the surface of the transfer drum 16. As a result, transfer defects such as white spots do not occur at the flaws, so that transfer efficiency can be improved.

Here, a method of cleaning unnecessary toner adhered on the suction roller 17 will be described below. In general, when the suction roller 17 is used for a long time, unnecessary toner adheres to the surface of the suction roller 17 and toner stain occurs on the surface of the recording paper 6, so that it is impossible to obtain a proper transfer image. Therefore, by utilizing the fact that a suction voltage of the same polarity as that of the toner is applied to the suction roller 17, when the recording paper 6 does not pass through the suction position Y, the suction roller 17 is brought into close contact with the transfer drum 16, and By applying a voltage having the same polarity as that of the toner, unnecessary toner attached to the attraction roller 17 is moved onto the transfer drum 16. At this time, the applied voltage may be a voltage value different from that at the time of suction.

In addition, the timing at which the suction roller 17 is brought into close contact with the transfer drum 16 is set immediately after the rear end of the recording paper 6 on which the toner image of the third color has been superimposed and transferred has passed the suction position Y. Can be lengthened. Further, at the time of continuous copying, it can also serve as a close contact operation of the suction roller 17 for sucking the next recording paper 6.

Next, a method for re-adsorbing the recording paper 6 will be described below. If the recording paper 6 such as a thick paper is used, there is a possibility that the adsorption to the transfer drum 16 may become insufficient depending on the bending rigidity of the thick paper. In this case, the recording paper 6 floats from the transfer drum 16 to cause a transfer failure. Likely to be. Therefore, in order to stabilize the adsorbability, the leading end portion (non-image area) of the recording paper 6 for the second and subsequent colors is re-adsorbed before transfer.

That is, in the color image formation, the recording paper 6 is rotated at least twice while being attracted to the transfer drum 16, so that when the first color toner image is transferred, it passes through the attracting position Y again. , Suction roller 1 in advance
7 is brought into close contact with the transfer drum 16 and only the leading end (non-image area) of the recording paper 6 is pressed at the suction position Y, and at the same time, a suction voltage is applied to cause re-suction. If the timing at which the suction roller 17 is brought into close contact with the transfer drum 16 is set at the rear end (non-image area) of the recording paper 6, the rear end (non-image area) can be re-adsorbed. Can be stabilized. As described above, by performing the re-suction, the image formed on the recording paper 6 is less likely to be displaced, and a clear image can be obtained.

On the premise of the above operation, the image forming process in the image forming apparatus 1 will be described below. First, as shown in FIG. 1, in the case of automatic paper feeding, the recording paper 6 is sent out to the PF roller 13 one by one by the pickup roller 12 in order from the uppermost part by the paper feeding cassette 10 provided at the bottom of the main body. The recording paper 6 that has passed through the PF roller 13 is conveyed by the registration roller 15 to the suction unit in accordance with the image forming timing. On the other hand, in the case of manual paper feeding, the recording paper 6 is fed out one by one from a manual paper feeding unit 11 provided on the front of the main body, and is conveyed to a registration roller 15 by a manual feeding roller 14.

Then, the recording paper 6 is conveyed by the registration roller 15 to the suction section in accordance with the image forming timing. Next, the recording paper 6 conveyed from the registration roller 15 in accordance with the image forming timing is conveyed to the suction position Y between the transfer drum 16 and the suction roller 17, and
Is charged by the voltage applied to the. Further, electric charges are induced in the insulator layer 42 via the recording paper 6, whereby the recording paper 6 is electrostatically attracted onto the transfer drum 16.

Thereafter, the recording paper 6 attracted to the transfer drum 16 is conveyed to a transfer position X which is a pressure contact portion between the transfer drum and the photosensitive drum 22. At this time, the transfer application roller 20 has a polarity opposite to that of the toner. A voltage is applied, and the toner image is transferred to the recording paper 6 by a potential difference between the electric charge of the toner formed on the photosensitive drum 22 and the electric charge on the surface of the recording paper 6. At this time, the photosensitive drum 22 is charged for each color,
Exposure, development, and transfer are performed. Therefore, the recording paper 6 rotates on the transfer drum 16 while being attracted to the transfer drum 16, and one-color transfer is performed every rotation.
One full-color image is obtained with a maximum of four rotations. However, when a black-and-white image or a monocolor image is obtained, the rotation of the transfer drum 16 may be one time.

The transfer applying roller 20 can be moved in an arc shape with respect to the center of the transfer drum 16 (in the direction of the arrow in the figure) while being in contact with the transfer drum 16 by driving means (not shown). The transfer is performed by changing the position in accordance with the electrical characteristics of the image. The amount of movement of the transfer applying roller 20 at this time is such that an electric field formed between the transfer drum 16 and the photosensitive drum 22 at the transfer position X has an appropriate value according to the transfer characteristics with respect to the applied voltage of the toner of each color. It is set to be. This makes it possible to transfer the toner of each color with uniform transfer efficiency without changing the transfer voltage applied to the transfer applying roller 20.

When all the toner images have been transferred onto the recording paper 6, the recording paper 6 is forcibly moved from the surface of the transfer drum 16 by a separation claw 19 provided on the circumference of the transfer drum 16 so as to be detachable from and separated from the transfer drum 16. And is guided to the fixing guide 30. Thereafter, the toner image on the recording paper 6 is guided to the fixing roller 29 by the fixing
Is fused and fixed on the recording paper 6 by the temperature and pressure. Then, the recording paper 6 after fixing is discharged onto a discharge tray 32 by a discharge roller 31.

The timing of the suction of the recording paper 6, transfer of the toner image, and cleaning of the suction roller 17 will be described below with reference to FIGS. 3, 5 to 8. In FIGS. 5 to 8, A denotes the suction roller 1.
7 shows the timing of separation and contact, and B and E show the application timings of the attracting voltage and the transfer voltage, respectively. Also,
C and D indicate the presence or absence of recording paper at the suction position and the transfer position, respectively. When the suction roller 17 is in contact, when a voltage is being applied, and when the recording paper 6 is passing through, ON is indicated.

Here, as shown in FIG.
6, the distance between the transfer position X and the suction position Y is L
s and the length of the recording paper 6 is Lp, the following two timing charts can be considered depending on the relationship between the distance Ls and the length Lp.

First, when Ls <Lp, the timing chart shown in FIG. 5 is obtained. In this case, before the trailing end of the recording paper 6 passes through the suction position Y, the leading end of the recording paper 6 passes through the transfer position X and the transfer starts, so that both the suction position Y and the transfer position X A simultaneous application section in which a voltage is applied occurs. On the other hand, when Ls ≧ Lp, as shown in FIG.
Since the transfer of the recording paper 6 always starts after the suction of the recording paper 6 ends, the above-described simultaneous application section does not exist.
Also, regardless of the relationship between Ls and Lp, if the distance between the recording papers 6 is reduced so as not to lower the copy speed during continuous copying, suction of the next recording paper 6 starts during transfer of the final toner image. , And a simultaneous application section of suction and transfer occurs.

In the image forming apparatus of the present embodiment, even if the above-mentioned simultaneous application section in which the above-mentioned suction and transfer are performed simultaneously exists, the suction and transfer are individually performed. Since an appropriate voltage can be applied, the conveyance of the recording paper 6 is performed smoothly, an efficient image forming operation is performed, and a high-quality image can be obtained.

In FIGS. 5 and 6, the timing at which the suction roller 17 is brought into close contact with the transfer drum 16 is determined immediately after the rear end of the recording paper 6 onto which the three color toner images have been transferred passes the suction position Y. It has become. As a result, the cleaning time of the suction roller 17, that is, the cleaning section indicated by, can be maximized.

The timing when the re-suction is performed as described above is, for example, as shown in FIG. 7, between the rear end and the front end of the suctioned recording paper 6 as shown in FIG.
Is provided in close contact with the transfer drum 16 to provide a re-adsorption period in which only the leading end (non-image area) of the recording paper 6 is re-adsorbed.
Alternatively, as shown in FIG. 8, the suction roller 17 is moved from the rear end (non-image area) of the sucked recording paper 6 to the front end (non-image area) of the recording paper 6 accompanying the transfer of the next color. In addition to the above-mentioned re-adsorption period, a re-adsorption period is provided in which the leading end portion (non-image area) of the recording paper 6 is re-adsorbed in close contact with the transfer drum 16.

By providing the re-adsorption period as described above, the floating of the recording paper 6 can be reliably prevented. This is particularly effective when the recording paper 6 has a certain thickness.
7 and 8 are timing charts when Ls <Lp, but the same can be said for Ls ≧ Lp.

Embodiment 2 The following will describe another embodiment of the present invention with reference to FIG. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Other components are
This is the same as the image forming apparatus 1 of the first embodiment.

The image forming apparatus of the present embodiment is provided with a suction applying roller 43 as shown in FIG. 9, instead of the suction ground roller 21 of the first embodiment shown in FIG. That is, contrary to the first embodiment, the high-voltage power supply 43a is connected to the suction applying roller 43 and the suction roller 17 is grounded so that the suction voltage can be applied from the inside of the transfer drum 16. Further, a ground roller 44 grounded between the transfer applying roller 20 and the attraction applying roller 43 is provided in order to eliminate mutual interference caused by applying both the transfer and the attraction voltage from inside. The suction applying roller 43 and the ground roller 44 are covered with an elastic body similarly to the transfer applying roller 20 and the suction ground roller 21 described in the first embodiment, and stabilize the contact state with the inner surface of the transfer drum 16. ing. In the present embodiment, at the time of suction, a positive polarity voltage is applied to the suction applying roller 43 side,
The recording paper 6 is charged by the potential difference between the suction roller 17 and the grounded suction roller 17 to perform electrostatic suction.

As described above, the suction voltage is applied to the transfer drum 16.
By applying voltage from the inner surface, the transfer position X and the suction position Y
Are applied with the same polarity, it is possible to share the voltage supply mechanism to the high voltage power supplies 17a and 20a, thereby simplifying the configuration. In addition, since it is not necessary to perform the separation / contact operation of the suction applying roller 43 for applying a high pressure,
Stable high voltage application becomes possible.

[Embodiment 3] The following will describe still another embodiment of the present invention with reference to FIG. 10 and FIG. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the image forming apparatus of this embodiment, four photosensitive drums 22 for forming toner images of respective colors are provided around the transfer drum 16 as shown in FIG. Around the drum 22, a charger 27, an exposing unit, any of the developing units 23 to 26, and a cleaning device 28 are provided for image formation.

Further, a transfer applying roller 20 is in contact with the inner surface of the transfer drum 16 at a transfer position X with each photosensitive drum 22. A ground roller (not shown) is provided between the transfer applying rollers 20 to eliminate the influence between the respective transfer.

The image forming process in the image forming apparatus having the above configuration will be described below. First, before the recording paper 6 is sent out onto the transport path, the suction roller 17 is insulated from the inner surface of the transfer drum 16 and a voltage of the same polarity as that during suction is applied to the suction roller 17 by the high-voltage power supply 17a using the suction ground roller 21 grounded as a counter electrode. To move the unnecessary toner adhered to the suction roller 17 onto the transfer drum 16.

Thereafter, the recording paper 6 conveyed on the conveyance path and sent to the suction position Y of the transfer drum 16 and the suction roller 17 is charged at the suction position Y and is transferred to the transfer drum 16.
Is electrostatically attracted. Then, in parallel with the suction of the recording paper 6 onto the transfer drum 16, a latent image corresponding to each color signal is sequentially formed on each photosensitive drum 22. The latent image is formed by uniformly charging the surface of each photosensitive drum 22 by a charger 27 corresponding to the surface of the photosensitive drum 22 and exposing the photosensitive drum 22 to light by an exposure unit. The latent image formed on each photosensitive drum 22 is
The toner image is developed by any one of the developing units 23 to 26 to form a toner image of each color.

By applying a voltage value to each of the transfer application rollers 20 inscribed in the transfer drum 16, these toner images are sequentially superimposed and transferred on the recording paper 6 on the transfer drum 16. The recording paper 6 on which the last toner image has been transferred is peeled off from the transfer drum 16 by the peeling claw 19, is taken to the fixing unit 5, and the toner image is fused to the recording paper 6.
Note that, in the present embodiment, a separation / contact mechanism for the suction roller 17 is unnecessary. Further, according to the above configuration, since the transfer of the toner images of the respective colors can be performed at the respective optimum transfer voltages, the density of each color can be individually adjusted, and a high-quality color image with high reproducibility can be obtained. Moreover, the speed of image formation is equivalent to that of monocopy.

Here, the suction, transfer and suction rollers 17
The cleaning timing is as shown in FIG. In FIG. 11, B indicates the application timing of the suction voltage, and C indicates the presence or absence of the recording paper at the suction position. F, G, H, and I are yellow,
The transfer timing of cyan, magenta, and black is shown. When the suction voltage is applied, the recording paper 6
Are shown as ON when passing through and when performing transfer.

In the above configuration, since a mechanism for separating and connecting the suction roller 17 is not required, the cleaning of the suction roller 17 can be performed by applying a voltage having the same polarity as that during suction, except when suction is being performed. In addition, there are sections where the transfer of the toner images of each color is performed at the same time, and sections where the adsorption and the transfer are performed simultaneously. In each of the above embodiments, the control of the suction and the transfer is performed by the voltage control, but may be performed by the current control.

[0071]

According to the first aspect of the present invention, there is provided an image forming apparatus comprising:
As described above, the toner image formed on the photosensitive drum is
In an image forming apparatus that transfers an image onto a recording medium electrostatically adsorbed on a drum-shaped recording medium holding member to form an image, the image forming apparatus is located at a position opposing the recording medium holding member of the photosensitive drum, and performs recording from the photosensitive drum. a first electrode generating an electric field between the photosensitive drum to effect the transfer of the toner to the medium, provided the position facing the third electrode provided on the outside of the record medium holding member, the third electrode And a second electrode for applying an electric charge to the recording medium for electrostatically attracting the recording medium holding member due to a potential difference between the recording medium holding member and the recording medium holding member. but while being composed of at least the inside of the holding member main body and the outside of the insulation layer, Ri near between the volume resistivity of the composition of the holding member main body 10 ⁴ to 10 ⁸ [Omega] cm, and the holding
It is assumed that rubber-like elasticity is exhibited between the member body and the insulator layer.
In particular , the composition has a volume resistivity between 10 ^{4 and} 10 ⁸ Ωcm.
That the elastic body layer is configured that provided. Therefore, the transfer performed between the photosensitive drum and the first electrode and the adsorption performed between the second electrode and the third electrode can be performed independently without being affected by each other. There is an effect that the control of the voltage value to be applied to each electrode, that is, an appropriate suction voltage or an appropriate transfer voltage can be easily performed.

Further , since the volume resistivity of the elastic layer is in the same range as the volume resistivity of the holding member, the above-mentioned effect is not obstructed, and the photosensitive drum for transferring to the recording paper on the recording paper holding member is not affected. When the elastic layer is deformed at the time of pressure contact, for example, the adhesion to the recording paper is improved and the transfer efficiency can be improved.

According to a second aspect of the present invention, as described above, in addition to the configuration of the first aspect , in addition to the third aspect,
The outer surface of the electrode is covered with at least an elastic body having rubber-like elasticity, and the hardness of the elastic body is smaller than the hardness of the elastic body layer. Therefore, in addition to the effect of the configuration of claim 1 , the recording medium can be bent along the shape of the recording medium holding member, and the adhesion of the recording medium to the recording medium holding member is improved. As a result, there is an effect that the floating of the recording paper is prevented, and accurate image transfer is performed.

According to a third aspect of the present invention, as described above, in addition to the configuration of the first or second aspect ,
When a voltage is applied to the first electrode and the second electrode so as to provide a potential difference required for transfer and electrostatic attraction, a voltage is applied between the first electrode and the second electrode so as to be inscribed in the recording medium holding member. This is a configuration in which a ground electrode is provided. Also,
The image forming apparatus according to the fourth aspect of the present invention, as described above,
Drum-shaped recording of the toner image formed on the photosensitive drum
The image is transferred to the recording medium electrostatically attracted to the
In an image forming apparatus for forming an image, a photosensitive drum
The photoconductor drum is located at a position facing the recording medium holding member.
Photoreceptor drum to transfer toner from
A first electrode for forming an electric field with the ram, and a recording medium holding device
A third electrode provided outside the member at a position facing the third electrode;
The recording medium holding member is electrostatically charged due to a potential difference from the third electrode.
A second electrode for applying a charge for adsorption to the recording medium;
However, all of them are inscribed inside the recording medium holding member.
While the recording medium holding member is less
Both are composed of the inner holding member body and the outer insulator layer
And the volume resistivity of the composition of the holding member body is 10
^{Between 4 and} 10 ⁸ Ωcm and suitable for transfer and electrostatic attraction
The first and second electrodes to provide a necessary potential difference;
When a voltage is applied to the recording medium holding member,
So that a ground electrode is provided between the first electrode and the second electrode.
Configuration. Therefore, with the ground electrode,
Even when different voltages are applied to the first electrode and the second electrode, each electrode is not affected by each other's voltage.
There is an effect that it is possible to maintain appropriate transfer voltage and suction voltage.

According to a fifth aspect of the present invention, as described above, in addition to the configuration of the first, second, third or fourth aspect, the third electrode is separated from the recording medium holding member. The third electrode is brought into contact with the recording medium holding member at a position where the recording medium is not held on the recording medium holding member, and the static electricity is provided between the second electrode and the third electrode. In this configuration, a voltage having the same polarity as that at the time of electroadsorption is applied. An image forming apparatus according to a sixth aspect of the present invention includes:
As described above, the toner image formed on the photosensitive drum is
Recording medium electrostatically adsorbed on drum-shaped recording medium holding member
In an image forming apparatus that transfers an image to a body to form an image,
At the opposing position with the recording medium holding member of the optical drum
Transfer the toner from the photosensitive drum to the recording medium.
Electrode for forming an electric field with the photoreceptor drum for
And a third electrode pair provided outside the recording medium holding member.
Recording medium is provided at a position
A charge is applied to the recording medium for electrostatic attraction to the holding member.
And a second electrode, both inside the recording medium holding member.
The recording medium holding unit is provided so as to be inscribed in
The material is at least the inner holding member body and the outer insulation
A body composed of a body layer and having a composition of the holding member body.
The product resistivity is between 10 ^{4 and} 10 ⁸ Ωcm, and the third
An electrode is provided so as to be detachable from the recording medium holding member.
And the recording medium on the recording medium holding member is not held.
The third electrode on the recording medium holding member
And electrostatic adsorption between the second and third electrodes.
In this configuration, a voltage having the same polarity as that at the time is applied. Therefore, even if toner adheres to the third electrode, the second electrode and the third
The toner adheres to the recording medium holding material side by the electric field formed between the electrodes, and the third electrode can be cleaned, so that the recording medium is not stained by the contamination of the third electrode. .

According to a seventh aspect of the present invention, as described above, in addition to the configuration described in any one of the first to sixth aspects, a plurality of color developing devices are provided around the photosensitive drum. The image formation is performed by performing development on a photosensitive drum and transfer to a recording medium for each color, and, in the recording medium holding member, a leading end in the moving direction of the recording medium for each transfer. This is a configuration for performing adsorption. Ma
The image forming apparatus according to the invention of claim 8 is configured as described above.
Then, the toner image formed on the photosensitive drum is
Transfer to the recording medium electrostatically adsorbed on the recording medium holding member
Image forming apparatus for forming an image by
Is located at the opposite position with the recording medium holding member
To transfer the toner from the ram to the recording medium.
A first electrode for forming an electric field with the body drum, and a recording medium
Provided at a position facing a third electrode provided outside the holding member
And a static potential is applied to the recording medium holding member by a potential difference from the third electrode.
A second electrode for applying a charge for electroadsorption to the recording medium;
However, all of them are inscribed inside the recording medium holding member.
While the recording medium holding member is less
Both are composed of the inner holding member body and the outer insulator layer
And the volume resistivity of the composition of the holding member body is 10
^{Between 4 and} 10 ⁸ Ωcm and around the photosensitive drum
A multi-color developing device is provided.
The image is formed by developing on the ram and transferring to the recording medium.
The recording medium holding member,
Suction of the leading end in the moving direction of the recording medium is performed for each transfer
Configuration. Therefore, even for a recording medium having relatively high rigidity, a voltage for suction is applied for each transfer,
The value of the electrostatic force acting on the recording medium is less likely to decrease,
Since the stable suction state is maintained, a clear image can be obtained without shifting the transfer position of each color on the recording medium.

According to a ninth aspect of the present invention, as described above, in addition to the configuration of any one of the first to eighth aspects, a developing device for a plurality of colors is provided around the photosensitive drum. A first electrode is provided, which performs image development by performing development on the photosensitive drum and transfer to a recording medium for each color, and a first electrode at a position facing the recording medium holding member of the photosensitive drum. The recording medium can be moved in a direction parallel to the moving direction of the recording medium with respect to the contact position between the photosensitive drum and the recording medium holding member while being in contact with the recording medium holding member. An image forming apparatus according to the invention of claim 10.
Indicates the toner formed on the photosensitive drum as described above.
An image in which an image is electrostatically attracted onto a drum-shaped recording medium holding member.
An image forming apparatus that transfers an image to a recording medium to form an image
Position opposite the recording medium holding member of the photosensitive drum.
Transfer the toner from the photosensitive drum to the recording medium.
First, an electric field is formed between the photosensitive drum and the photosensitive drum.
An electrode and a third electrode provided outside the recording medium holding member
Is recorded at the position opposite to the third electrode and the potential difference from the third electrode.
The charge for electrostatically attracting the medium holding member is applied to the recording medium.
And a second electrode to be applied,
While it is provided so as to be inscribed inside,
The holding member has at least an inner holding member body and an outer holding member body.
The composition of the holding member body, which is composed of an insulator layer
Has a volume resistivity between 10 ^{4 and} 10 ⁸ Ωcm, and
A multi-color developing device is provided around the body drum,
For each color, development on the photosensitive drum and transfer to the recording medium
To form an image, and the recording medium of the photosensitive drum.
The first electrode located at a position facing the body holding member is a recording medium.
While keeping in contact with the body holding member,
The direction of movement of the recording medium and the
This is a configuration that can be moved in the row direction. That is, even if the same applied voltage is applied due to the resistance of the recording medium holding member, the electric field formed between the recording member and the photosensitive drum changes depending on the position of the first electrode. Further, the transfer characteristics of each toner with respect to the applied voltage are different. therefore,
If the electric field is adjusted by making the first electrode movable, there is an effect that transfer can be performed by forming an electric field suitable for each toner without changing the applied voltage.

An image forming apparatus according to claim 11 is
As described above, in addition to the configuration according to any one of claims 1 to 6, a plurality of photosensitive drums for developing different colors are provided, and the recording medium holding member of each photosensitive drum is sandwiched. This is a configuration in which a first electrode is provided at a facing position. An image form according to the twelfth aspect of the present invention.
The forming device is formed on the photosensitive drum as described above.
The toner image is electrostatically attracted onto a drum-shaped recording medium holding member.
Image forming apparatus that transfers images to a recording medium
And oppose each other with the recording medium holding member of the photosensitive drum
Transfer of toner from photoreceptor drum to recording medium
An electric field between the photoconductor drum and the
A first electrode and a third electrode provided outside the recording medium holding member;
Provided at a position facing the electrode, and by a potential difference from the third electrode
The charge for electrostatically attracting the recording medium holding member is transferred to the recording medium.
The second electrode applied to the body, the recording medium holding portion
The recording medium is provided so as to be inscribed inside the material.
The body holding member has at least an inner holding member body and an outer holding member body.
Of the holding member body
The volume resistivity of the composition is between 10 ^{4 and} 10 ⁸ Ωcm, and
Multiple photosensitive drums for developing different colors are provided.
While holding the recording medium holding member of each photosensitive drum.
This is a configuration in which the first electrode is provided at the opposite position.
That is, since the first electrodes are provided for the respective photosensitive drums, the voltages can be individually controlled. Therefore, even when a plurality of colors are developed to form a color image, it is possible to perform adsorption and transfer at optimum voltage values without lowering the speed of image formation.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a transfer drum shown in FIG.

FIG. 3 is a schematic diagram illustrating only a main part of the image forming apparatus illustrated in FIG. 1;

FIG. 4 is a schematic diagram of a transfer drum and a suction roller used for describing Paschen discharge.

5 is a timing chart showing timings of suction and transfer in the image forming apparatus of FIG. 3, in which the length of the recording paper in the traveling direction is longer than the distance between the suction position and the transfer position on the transfer drum. is there.

6 is a timing chart showing timings of suction and transfer in the image forming apparatus of FIG. 3, in a case where the length of the recording paper in the traveling direction is shorter than the distance between the suction position and the transfer position on the transfer drum. is there.

FIG. 7 is a timing chart showing timing when re-adsorption is performed only on the leading end of the recording paper in FIG.

FIG. 8 is a timing chart showing the timing when the leading and trailing ends of the recording paper are re-adsorbed in FIG.

FIG. 9 is a schematic view showing another embodiment of the present invention.

FIG. 10 is a schematic diagram showing still another embodiment of the present invention.

11 is a timing chart showing timings of suction and transfer in the image forming apparatus of FIG. 10;

FIG. 12 is a schematic diagram illustrating a configuration example of a conventional image forming apparatus.

FIG. 13 is a schematic diagram illustrating another configuration example of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 6 Recording paper (recording medium) 16 Transfer drum (recording medium holding member) 17 Adsorption roller (third electrode) 20 Transfer application roller (first electrode) 21 Adsorption ground roller (second electrode) 22 Photosensitive drum Reference Signs List 40 drum main body (holding member main body) 41 elastic layer 42 insulating layer 43 suction applying roller (second electrode) 44 ground roller (ground electrode)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Atsushi Ide 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Inventor Kazuyuki Onishi 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56) References JP-A-6-230692 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/16

Claims (12)

(57) [Claims] 1. A de toner image formed on the photosensitive drum
In an image forming apparatus that forms an image by transferring an image onto a recording medium electrostatically adsorbed on a ram-shaped recording medium holding member, the image forming apparatus is located at a position facing the photosensitive drum with the recording medium holding member interposed therebetween, and performs recording from the photosensitive drum. a first electrode generating an electric field between the photosensitive drum to effect the transfer of the toner to the medium, provided the position facing the third electrode provided on the outside of the record medium holding member, the third electrode And a second electrode for applying an electric charge to the recording medium for electrostatically attracting the recording medium holding member due to a potential difference between the recording medium holding member and the recording medium holding member. but while being composed of at least the inside of the holding member main body and the outside of the insulation layer, Ri near between the volume resistivity of the composition of the holding member main body 10 ⁴ to 10 ⁸ [Omega] cm, and the holding
It is assumed that rubber-like elasticity is exhibited between the member body and the insulator layer.
In particular , the composition has a volume resistivity between 10 ^{4 and} 10 ⁸ Ωcm.
An image forming apparatus comprising Rukoto elastic layer provided that. 2. An outer surface of the third electrode is at least rubber-like.
Covered with an elastic body exhibiting elasticity,
The image forming apparatus according to claim 1, wherein the hardness of the body is smaller than the hardness of the elastic layer . 3. An electric potential difference required for transfer and electrostatic attraction is provided.
Preferably, a voltage is applied to the first and second electrodes.
Sometimes, the first electronic device is inscribed in the recording medium holding member.
The image forming apparatus according to claim 1 or 2, characterized in that the ground electrode is provided between the electrode and the second electrode. 4. A toner image formed on a photosensitive drum.
Recording medium electrostatically adsorbed on a ram-shaped recording medium holding member
In an image forming apparatus that forms an image by transferring an image onto a recording medium holding member of a photosensitive drum,
Transfer the toner from the photosensitive drum to the recording medium.
Electrode for forming an electric field with the photoreceptor drum for
And a third electrode pair provided outside the recording medium holding member.
Et provided countercurrent position is, the recording medium by a potential difference between the third electrode
A charge is applied to the recording medium for electrostatic attraction to the holding member.
And a second electrode, both inside the recording medium holding member.
The recording medium holding unit is provided so as to be inscribed in
The material is at least the inner holding member body and the outer insulation
A body composed of a body layer and having a composition of the holding member body.
When a voltage is applied to the first electrode and the second electrode so that the product resistivity is between 10 ^{4 and} 10 ⁸ Ωcm and a potential difference required for transfer and electrostatic attraction is applied, the recording medium holding member An image forming apparatus, wherein a ground electrode is provided between the first electrode and the second electrode so as to be inscribed in the image forming apparatus. 5. The recording medium holding member according to claim 5, wherein the third electrode is provided so as to be detachable from the recording medium holding member, and the third electrode is placed on the recording medium holding member at a position where the recording medium is not held. And the second electrode and the third
5. The image forming apparatus according to claim 1, wherein a voltage having the same polarity as that at the time of electrostatic attraction is applied to the electrodes. 6. A toner image formed on a photosensitive drum.
Recording medium electrostatically adsorbed on a ram-shaped recording medium holding member
In an image forming apparatus that forms an image by transferring an image onto a recording medium holding member of a photosensitive drum,
Transfer the toner from the photosensitive drum to the recording medium.
Electrode for forming an electric field with the photoreceptor drum for
And a third electrode pair provided outside the recording medium holding member.
Recording medium is provided at a position
A charge is applied to the recording medium for electrostatic attraction to the holding member.
And a second electrode, both inside the recording medium holding member.
The recording medium holding unit is provided so as to be inscribed in
The material is at least the inner holding member body and the outer insulation
A body composed of a body layer and having a composition of the holding member body.
The product resistivity is between 10 ^{4 and} 10 ⁸ Ωcm, and the third
An electrode is provided so as to be detachable from the recording medium holding member.
And the recording medium on the recording medium holding member is not held.
The third electrode on the recording medium holding member
And electrostatic adsorption between the second and third electrodes.
An image forming apparatus comprising Rukoto voltage of the same polarity as the time is applied. 7. A multi-color developing device is provided around the photosensitive drum.
Development and recording on the photosensitive drum for each color
Transfer to a medium to form an image,
In the recording medium holding member, the recording medium
The image forming apparatus according to any one of claims 1 to 6 to perform the adsorption of the moving direction tip characterized Rukoto of. 8. A toner image formed on a photosensitive drum.
Recording medium electrostatically adsorbed on a ram-shaped recording medium holding member
In an image forming apparatus that forms an image by transferring an image onto a recording medium holding member of a photosensitive drum,
Transfer the toner from the photosensitive drum to the recording medium.
Electrode for forming an electric field with the photoreceptor drum for
And a third electrode pair provided outside the recording medium holding member.
Recording medium is provided at a position
A charge is applied to the recording medium for electrostatic attraction to the holding member.
And a second electrode, both inside the recording medium holding member.
The recording medium holding unit is provided so as to be inscribed in
The material is at least the inner holding member body and the outer insulation
A body composed of a body layer and having a composition of the holding member body.
The product resistivity is between 10 ^{4 and} 10 ⁸ Ωcm and the photoconductor
A multi-color developing device is provided around the ram,
Development on the photosensitive drum and transfer to the recording medium
To form an image on the recording medium holding member.
For each transfer, the suction at the leading end of the recording medium in the moving direction is performed.
An image forming apparatus comprising Rukoto to perform the wear. 9. A multi-color developing device is provided around a photosensitive drum.
Development and recording on the photosensitive drum for each color
The image is formed by transferring the image to a medium.
The second drum is located at a position opposite to the recording medium holding member of the body drum.
While one electrode is in contact with the recording medium holding member,
The recording medium is moved relative to the contact position between the ram and the recording medium holding member.
That it can move in the direction parallel to the body
The image according to any one of claims 1 to 8, characterized in that:
Image forming device. 10. A toner image formed on a photosensitive drum.
Recording medium electrostatically adsorbed on drum-shaped recording medium holding member
In an image forming apparatus that forms an image by transferring the image onto a body, the image forming apparatus is located at an opposing position with the recording medium holding member of the photosensitive drum therebetween.
Transfer the toner from the photosensitive drum to the recording medium.
Electrode for forming an electric field with the photoreceptor drum for
And a third electrode pair provided outside the recording medium holding member.
Recording medium is provided at a position
A charge is applied to the recording medium for electrostatic attraction to the holding member.
And a second electrode, both inside the recording medium holding member.
The recording medium holding unit is provided so as to be inscribed in
The material is at least the inner holding member body and the outer insulation
A body composed of a body layer and having a composition of the holding member body.
The product resistivity is between 10 ^{4 and} 10 ⁸ Ωcm and the photoconductor
A multi-color developing device is provided around the ram,
Development on the photosensitive drum and transfer to the recording medium
To form an image and store the recording medium on the photosensitive drum.
The first electrode located at a position facing the holding member sandwiches the recording medium.
While keeping in contact with the holding member, the photosensitive drum and the recording medium
Parallel to the direction of movement of the recording medium
Image forming apparatus characterized by being movable in
Place. 11. A photosensitive drum for developing different colors.
And a recording medium for each photosensitive drum.
The first electrode is provided at a position facing the body holding member.
The method according to any one of claims 1 to 6, wherein
The image forming apparatus as described in the above. 12. A toner image formed on a photosensitive drum.
Recording medium electrostatically adsorbed on drum-shaped recording medium holding member
In an image forming apparatus that forms an image by transferring the image onto a body, the image forming apparatus is located at an opposing position with the recording medium holding member of the photosensitive drum therebetween.
Transfer the toner from the photosensitive drum to the recording medium.
Electrode for forming an electric field with the photoreceptor drum for
And a third electrode pair provided outside the recording medium holding member.
Recording medium is provided at a position
A charge is applied to the recording medium for electrostatic attraction to the holding member.
And a second electrode, both inside the recording medium holding member.
The recording medium holding unit is provided so as to be inscribed in
The material is at least the inner holding member body and the outer insulation
A body composed of a body layer and having a composition of the holding member body.
The product resistivity is between 10 ^{4 and} 10 ⁸ Ωcm, and
If there are multiple photoconductor drums that develop different colors,
In the opposite direction, the recording medium holding member of each photosensitive drum is sandwiched
Image characterized in that a first electrode is provided at a position
Forming equipment.