JPH0934271A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely discharge residual charge on the surface of the transfer body by impressing a voltage which is the same in polarity and higher in voltage in comparison with a voltage impressed on the conductive layer of a transfer body on a discharging brush. SOLUTION: After a transfer paper is peeled from a transfer drum 11 by a peeling pawl 14 when a transfer operation is ended, a roller type conductive brush (discharging brush) 40 is moved so as to come into contact with the transfer drum 11, and a discharging operation is executed. When the discharging operation starts, the charge remaining on the surface of the transfer drum 11 runs away to the ground through the brush 40 grounded through a power source part 41. The voltage is impressed on the conductive layer 26 of the transfer drum 11 by a power source part 32. And also, the voltage is impressed on the brush 40 by the power source part 41. The voltage whose polarity is the same as that of the voltage impressed on the conductive layer 26 of the transfer drum 11 and which is higher than the voltage impressed on the layer 26 is impressed on the brush 40.

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 laser fax machine, a laser printer, a copying machine and the like, and more particularly to an image forming apparatus equipped with a discharging means for a transfer drum of the apparatus.

[0002]

2. Description of the Related Art Conventionally, a toner is attached to an electrostatic latent image formed on a photosensitive drum and developed, and this toner image is
2. Description of the Related Art There is an image forming apparatus that performs transfer to a transfer paper wound around a transfer drum.

Such an image forming apparatus is shown in FIG.
As shown in FIG. 5, a cylinder 101 having a dielectric layer 101a
Inside, corona chargers 102 and 104 are separately arranged. The corona charger 102 applies a charge for adsorbing the transfer paper P to the dielectric layer 101a. Further, the corona charger 104 transfers the toner image formed on the surface of the photosensitive drum 103 to the transfer paper P. Therefore, this image forming apparatus has two corona chargers 102 and 104.
According to this, adsorption and transfer are performed separately.

However, in the above-mentioned image forming apparatus, since the cylinder 101, which is the transfer drum, has a single-layer structure of only the dielectric layer 101a, the corona chargers 102 and 104 are disposed inside the cylinder 101 as described above. There is a need to. Therefore, the downsizing of the cylinder 101 is limited, and there is a problem that the device cannot be downsized.

As another image forming apparatus, FIG.
As shown in FIG. 3, a cylinder 201 having a two-layer structure of an outer semiconductive layer 201a and an inner base material 201b, and a grip mechanism 202 for holding the transferred transfer paper P along the cylinder 201. There are some with. In this image forming apparatus, the transferred transfer paper P is used for the grip mechanism 20.
After the end portion of the cylinder 201 is grasped by 2 and is made to follow the surface of the cylinder 201, a voltage is applied to the base material 201b of the inner layer of the cylinder 201 by the power supply unit 203 to charge the surface of the cylinder 201, and the toner of the photosensitive drum 103 It is designed to transfer images.

In the image forming apparatus described above, the cylinder 201, which is the transfer drum, has a two-layer structure, so that the cylinder 201 for transferring the toner image onto the transfer paper P is charged by one power supply unit 2.
It is possible to do this by using No. 03, so that two chargers are unnecessary.

However, since the image forming apparatus is provided with the grip mechanism 202, the overall structure of the image forming apparatus becomes complicated. In addition, the outer semiconductive layer 20
In order to fix 1a and the base material 201b of the inner layer to form the cylinder 201, it is necessary to fix them with metal fittings and then screw them together, or to fix them with double-sided tape or the like. As a result, the number of parts of the entire device increases, which causes a problem of increasing the cost of the product.

Therefore, as an image forming apparatus that solves each of the above problems, for example, Japanese Patent Laid-Open No. 2-74975 discloses:
Disclosed is a transfer roller in which conductive rubber and a dielectric film are laminated on a grounded metal roll, and a corona charger driven by a unipolar power source is provided near the transfer paper peeling position on the transfer drum. Has been done.

In the above image forming apparatus, the transfer paper is attracted to the transfer drum by inducing the electric charge in the dielectric film by the corona charger, and when the transfer paper is attracted, the charge is further induced on the surface of the transfer paper. The toner image is transferred to the transfer paper. Therefore, according to the image forming apparatus, one charging device charges the surface of the transfer drum, adsorbs the transfer paper, and transfers the toner image, so that only one charging device is required and the transfer drum can be downsized. can do. Further, the grip mechanism 202 for holding the transfer paper is not required,
Transfer paper can be adsorbed with a simple structure.

However, in the above-mentioned transfer drum, since the transfer paper is adsorbed by the static electricity, charges may remain on the transfer drum, and the residual charges may cause toner to adhere to the surface of the transfer drum. As a result, with the toner,
The back side of the transfer paper will become dirty. Further, due to the above-mentioned residual charge, the transfer paper is not adsorbed to the transfer drum poorly. As a result, the transfer paper is not reliably held on the transfer drum, and the toner image cannot be transferred well to the transfer paper. Was causing the problem.

Therefore, in Japanese Patent Laid-Open No. 6-51645, a cleaning means using a conductive brush for scraping the toner around the transfer drum and a transfer means for transferring the residual charge on the transfer drum to the conductive brush are removed. A transfer device for an image forming apparatus has been proposed which includes a charge removing unit that applies a voltage having a polarity opposite to the surface potential of the drum. by this,
Since the charge removal and cleaning of the transfer drum can be performed, the transfer paper can be adsorbed to the transfer drum favorably, and the back surface of the transfer paper can be prevented from being soiled.

[0012]

However, in the transfer device of the image forming apparatus disclosed in Japanese Unexamined Patent Publication No. 6-51645, the transfer is performed by frictional contact between the brush and the transfer drum during cleaning by using the conductive brush. The drum is prevented from being charged, and the transfer drum is discharged. When performing this charge removal, a voltage having a polarity opposite to the surface potential of the transfer drum is applied to the conductive brush, but the configuration for performing good charge removal is not sufficiently considered,
The surface potential cannot be surely removed. Therefore, there are still problems that the back surface of the transfer paper is stained with the toner and that the transfer paper is not adsorbed to the transfer drum due to the residual charge.

[0013]

In order to solve the above-mentioned problems, an image forming apparatus according to the present invention comprises an image carrier on which a toner image is formed, and a dielectric layer from the surface layer side to the inner layer side. A body layer, a semiconductive layer, and a conductive layer are sequentially stacked, and the transfer paper is conveyed while being attracted to the surface and brought into contact with the image carrier to transfer the toner image formed on the image carrier. A transfer member for transferring to the paper, a voltage for attracting the transfer paper, and a first voltage applying unit for applying a voltage for transferring the toner image to the transfer paper to a conductor layer of the transfer member; A grounded electrode member that is provided on the opposite side of the transfer paper from the carrier and is in contact with the surface of the transfer body via the transfer paper, and rotates while contacting the dielectric layer of the transfer body, A roller type static eliminator brush for neutralizing the dielectric layer; It is characterized in that it comprises a second voltage applying means for applying a voltage higher than the voltage of the same polarity and the voltage applied to the body layer.

According to the structure of claim 1, in the static elimination brush,
Since a voltage having the same polarity as the voltage applied to the conductor layer of the transfer body and a voltage higher than this voltage is applied, the residual charge on the surface of the transfer body can be surely removed by the charge removal brush.
This static elimination principle will be described below. Considering from the principle of the capacitor, when the polarized electrodes are made conductive, a current is generated and the transfer body is discharged. However, in the charge removal of the transfer body,
If the transfer body and the charge removal brush are discharged at the same voltage, the charge cannot be completely removed. Therefore, if a voltage higher than that of the transfer body is applied to the charge eliminating brush, the polarized and charged charges can be attracted to the charge eliminating brush to completely eliminate the charge.

As a result, due to the residual charge, the toner adheres to the surface of the transfer member and stains the back of the transfer paper.
Alternatively, it is possible to prevent a situation in which the transfer image of the transfer paper is poorly adsorbed to the transfer body and the toner image is not transferred to the transfer sheet, and an electric charge that is advantageous for adhering the next transfer paper to the transfer body is applied to the transfer body surface. Can be supplied.

An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect of the invention, wherein the static eliminating brush has an axial direction orthogonal to the moving direction of the transfer body surface. It is characterized by being arranged in a tilted state.

According to the structure of claim 2, the contact area of the charge removing means with respect to the transfer means is increased, and the charge removing effect of the transfer means is improved without increasing the diameter of the charge removing means.

As a result, it is possible to prevent an increase in the size of the image forming apparatus and an increase in cost for improving the charge removal effect of the transfer unit.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. This image forming apparatus
As shown in FIG. 2, a sheet feeding unit 1 that accommodates and supplies a transfer sheet as a recording sheet on which an image with toner is formed, a transfer unit 2 that transfers a toner image onto the transfer sheet, and a developing unit 3 that forms a toner image. And a fixing unit 4 for fusing and fixing the toner image transferred onto the transfer paper.

The paper feeding unit 1 is detachably arranged at the bottom of the main body, and is provided on the front side of the main body, and a paper feeding cassette 5 for accommodating the transfer paper and supplying it to the transfer unit 2. A manual sheet feeding section 6 for manually feeding the transfer sheets one by one is provided. Further, in the paper feed unit 1, a pickup roller 7 that feeds the transfer papers one by one from the uppermost portion of the paper feed cassette 5, a PF roller 8 that conveys the transfer papers fed by the pickup roller 7, and a manual feed unit 6 The manual feed roller 9 that conveys the transferred transfer paper and the above P
A pre-curl roller 10 is provided to curl the transfer paper conveyed by the F roller 8 and the manual feed roller 9.

The paper feed cassette 5 is provided with a sending member 5a biased upward by a spring or the like, and the transfer paper is stacked on the sending member 5a. As a result, the uppermost part of the transfer paper in the paper feed cassette 5 contacts the pickup roller 7, and the PF roller 8 is fed one by one by the rotation of the pickup roller 7 in the arrow direction.
And is conveyed to the pre-curl roller 10. On the other hand, the transfer paper supplied from the manual paper supply unit 6 is also conveyed to the pre-curl roller 10 by the manual paper feed roller 9. still,
The pre-curl roller 10 curls the transferred transfer paper as described above, so that the transfer paper is easily attracted to the surface of the cylindrical transfer drum 11 provided in the transfer unit 2. Is.

The transfer section 2 is provided with a transfer drum 11 as the transfer means. Around the transfer drum 11, a ground roller 12 serving as a grounded electrode member, a guide member 13 for guiding the transfer paper so as not to fall from the transfer drum 11, and a transfer paper adsorbed on the transfer drum 11 are forcibly forced. A roller-type conductive brush 40, which is a charge removing unit that removes the residual charges of the peeling claw 14 and the transfer drum 11 that are peeled off, is provided. The details of the structure of the transfer drum 11 will be described later. In addition, the peeling claw 14
The roller-type conductive brush 40 can be driven by a driving unit (not shown) so as to come into contact with the surface of the transfer drum 11.

Further, in the developing section 3, the transfer drum 11 is
A photosensitive drum 15 is provided as an image carrier that is pressed against the photosensitive drum. The photoconductor drum 15 has a grounded conductive aluminum base pipe 15a, and an OPC film 15b is applied to the surface thereof. Around the photoconductor drum 15, developing devices 16, 17, 18 and 19 containing yellow, magenta, cyan and black toners are radially arranged. Further, a charger 20 for charging the surface of the photosensitive drum 15 and a cleaning blade 21 for scraping and removing the residual toner on the surface of the photosensitive drum 15 are provided. A toner image is formed on the surface of the photoconductor drum 15 for each of the toners described above when a full-color image is formed. That is, charging, exposure, development and transfer are repeated for each color on the photosensitive drum 15. Therefore, in the case of color copying, a toner image of one color is transferred to the transfer paper every one rotation of the transfer drum 11 electrostatically attracted to the transfer drum 11, and a maximum of four rotations cause one transfer. To get one color image. The photoconductor drum 15 and the transfer drum 11 are pressed against each other so that a pressure of 8 kg is applied at the transfer site in view of transfer efficiency and image quality.

In the fixing unit 4, a fixing roller 23 that fuses the toner image at a predetermined temperature and pressure to fix the toner image on the transfer paper.
And a fixing guide 22 that guides the transfer paper separated from the transfer drum 11 by the separation claw 14 after the transfer of the toner image to the fixing roller 23. A discharge roller 24 is provided on the downstream side of the transfer paper conveyance of the fixing unit 4 so that the transfer paper after fixing is discharged from the main body of the apparatus onto a discharge tray 25.

Now, the structure of the transfer drum 11 will be described. As shown in FIG. 7, the transfer drum 11 has a cylindrical conductor layer 26 made of aluminum as a base material, and an outer surface of the conductor layer 26 is made of an elastic semi-conductor layer 27 made of urethane foam. Is provided. Further, a dielectric layer 28 made of polyvinylidene fluoride is provided on the outer surface of the semiconductive layer 27. A power supply unit 32 as a voltage applying unit is connected to the conductor layer 26 so that a stable voltage is maintained over the entire circumference of the conductor layer 26.

The above layers are not adhered by an adhesive or the like, but are provided at both ends of a sheet-like semiconductive layer 27 and dielectric layer 28, for example, as shown in FIG. The bosses 30a provided on the sheet pressing plate 30 are fitted into the plurality of through holes 29 penetrating each layer.
Further, the boss 30a is fitted into the opening 26a provided on the upper surface of the conductor layer 26 to fix the semi-conductor layer 27 and the dielectric layer 28 to the conductor layer 26.

In the fixing method described above, the semiconductive layer 27 and the dielectric layer 28 can apply tension to the inside of the conductive layer 26 by the sheet pressing plate 30. This prevents floating and loosening of each layer. Further, since each of the above layers is only fixed by the sheet pressing plate 30, each of the layers can be easily replaced.

As another fixing method, as shown in FIG. 9, the sheet pressing member 31 having 31a at both ends and a fixing member 31b at the center is used to remove the semiconductive layer 27 and the dielectric layer 28 from the semiconductive layer 27 and the dielectric layer 28. There is a sheet for fixing the sheet to the conductor layer 26. In this fixing method, the bosses 31a of the sheet pressing member 31 are fitted into the fitting holes 26b provided at both ends of the opening 26a of the conductor layer 26, and the sheet pressing member 31 is fixed to the opening 26a. The member 31b is inserted and fixed to the conductor layer 26.

Here, the suction operation of the transfer paper and the transfer operation of the toner image by the transfer drum 11 will be described below with reference to FIGS. 10 and 11. The transfer drum 11
It is assumed that a positive voltage is applied to the conductor layer 26 from the power source section 32. First, the suction operation of the transfer paper P will be described. As shown in FIG. 10, the transfer paper P conveyed to the transfer drum 11 is transferred to the dielectric layer 28 by the ground roller 12.
The charges pressed against the surface and accumulated in the semiconductive layer 27 are transferred to the dielectric layer 28, and positive charges are induced on the surface of the dielectric layer 28. As a result, negative charges are induced inside the transfer paper P, that is, on the contact surface side with the dielectric layer 28. Therefore, the transfer paper P is electrostatically attracted to the transfer drum 11.
The attracting force does not become non-uniform as long as the applied voltage is stable, and the transfer paper P is stably transferred to the transfer drum 11.
Can be adsorbed on.

As described above, since the charging is carried out not by the air discharge but by the contact, the conductive layer 26 is formed.
Voltage to be applied is low. From various experimental results, it is known that the applied voltage is preferably +3 kV or less, and more preferably +2 kV, the charging is favorably performed. Further, the transfer paper P attracted to the transfer drum 11 is
With the outer side being positively charged, the toner image is conveyed to the transfer point X of the toner image as the transfer drum 11 rotates in the direction of the arrow.

Next, the transfer operation of the toner image on the transfer paper P will be described. As shown in FIG. 11, the photosensitive drum 15 has toner having a negative charge adsorbed on its surface.
Therefore, when the transfer paper P whose surface is positively charged is conveyed to the transfer point X, the toner is adsorbed and transferred onto the surface of the transfer paper P. The transfer drum 11 and the photosensitive drum 15 are pressed against each other at the transfer point X so as to have a predetermined nip width. Therefore, the nip width affects the transfer efficiency, that is, the image.

Table 1 shows the relationship between the nip width and the image quality.

[0033]

[Table 1]

From Table 1, it is possible to improve the image quality if the nip width is in the range of 2 to 7 mm, especially 3 to 6
It can be seen that the range of mm is more preferable.

The semiconductive layer 27 has a volume resistance value of 10 ⁸ Ω · cm, a layer thickness of 2 to 5 mm, and a hardness of Asker C of 25 to 50. This is set in this embodiment because the transfer drum 11 and the photosensitive drum 15 are pressed against each other at a pressure of 2 kg.

That is, if the material of the semiconductive layer 27 changes,
Since the pressure contact force between the transfer drum 11 and the photoconductor drum 15 changes, the thickness, hardness, etc. of the semiconductive layer 27 are changed according to the material of the semiconductive layer 27 so as to obtain a desired image quality. ing. Therefore, in the present embodiment, the semi-conductor layer 27 having the above-mentioned layer thickness and hardness provides an appropriate nip width range.

The above-mentioned Asker C is a standard in the Japan Rubber Association, and a hardness measuring needle having a spherical tip is pressed against the surface of the sample by the force of the spring, and the resistance of the sample and the spring The hardness is expressed by the depth (pushing depth) with which the needle pushes the sample when the force and the force are balanced. According to the Asker C standard, the hardness of the sample is set to 0 degree so that the pushing depth of the needle when a load of 55 g is applied to the spring is equal to the maximum displacement of the needle,
The hardness of the sample is set to 100 degrees so that the depth of pushing of the needle is 0 when a load of 855 g is applied to the spring.

The volume resistance value of the semiconductive layer 27 is 0Ω.
If it is cm, the ground roller 12 arranged at the suction start point of the transfer paper P causes a voltage drop before the transfer paper P reaches the transfer point X. In order to prevent this voltage drop, the semiconductive layer 27 has a predetermined volume resistance value, and the semiconductive layer 27 acts as a capacitor to prevent the voltage drop.

Table 2 shows the relationship between the volume resistance value and the image quality.

[0040]

[Table 2]

From Table 2, the volume resistance value of the semiconductive layer 27 is in the range of 10 ⁵ to 10 ⁸ Ω · cm, and transfer can be performed efficiently without retransfer or transfer failure.
It is understood that it is more preferable if it is in the range of 10 ⁶ to 10 ⁷ Ω · cm. Therefore, if the volume resistance value of the semiconductive layer 27 is 10 ⁸ Ω · cm as in the present embodiment, good transfer can be performed and good image quality can be obtained.

The dielectric layer 28 is generally required to have a high dielectric constant and a charge retention property. Therefore, the dielectric layer 28 is made of vinylidene fluoride as described above, and its dielectric constant is set in the range of 8-12. Therefore, from the equation of c = ε · s / t (c is the charge amount, ε is the dielectric constant, s is the area, and t is the thickness), the dielectric layer 28
Is calculated.

From the above, if the permittivity ε is small, the charge amount c becomes small from the above equation, and the transfer efficiency becomes good. Further, since the charge amount c is small, the adsorption force is also small. Further, if the thickness t is small, the charge amount c becomes large according to the above formula, the transfer efficiency becomes poor, and the charge amount c becomes large, so that the attraction force becomes large.

From the above, it is necessary to properly set the dielectric constant ε and the layer thickness t. Therefore, the dielectric layer 28
Has a dielectric constant of 8 to 12 and a layer thickness of 100 to 300 μm.
In the range of m, the suction force and the transfer efficiency of the transfer paper P become appropriate.

As shown in FIG. 12, the width of the dielectric layer 28 of the transfer drum 11 is larger than the width of the photoconductor tube (aluminum tube 15a) forming the photoconductor drum 15, and
The photoconductor tube width is larger than the effective transfer width, and the effective transfer width is larger than the effective image width (application width of the OPC film 15b).

As shown in FIG. 13, when the layers of the transfer drum 11 are formed such that the conductor layer 26> semiconductor layer 27> dielectric layer 28, the semiconductor layer 27 is exposed. There is a possibility that the aluminum drum 15a of the body drum 15 that is grounded may come into contact. That is, when a positive voltage is applied to the conductor layer 26 by the power supply unit 32, positive charges are induced in the conductor layer 26, and the positive charges move to the surface of the semiconductor layer 27. At this time, if the grounded aluminum tube 15a of the photoconductor drum 15 and the semiconductive layer 27 come into contact with each other, all the electric charges charged in the semiconductive layer 27 are transferred to the aluminum tube 15a. It becomes impossible to induce positive charges on the surface of the dielectric layer 28. Therefore, the transfer drum 11 cannot adsorb the negatively charged toner adsorbed on the OPC film 15b, and a transfer failure occurs.

Therefore, each layer of the transfer drum 11 is as shown in FIG.
As shown in FIG. 7, the conductor layer 26 and the dielectric layer 28 have the same width, and the semi-conductor layer 27 has a width smaller than each of the above widths, so that the semi-conductor layer 27 is grounded. It is possible to prevent contact with the aluminum base tube 15a and prevent leakage of charges. As a result, the transfer drum 11
Can adsorb negatively charged toner adsorbed on the OPC film 15b, and transfer defects can be eliminated.

The diameter of the transfer drum 11 is such that one transfer sheet can be wound without overlapping, that is, the maximum width or length of the transfer sheet P that can be used in the image forming apparatus. Has been done. As a result, the image forming apparatus can stably wind the transfer paper P around the transfer drum 11, and as a result, transfer efficiency can be improved and image quality can be improved.

Here, the image forming process in the image forming apparatus having the above configuration will be described with reference to FIGS. 2, 10 and 1.
1 will be described below. As shown in FIG. 2, in the case of automatic sheet feeding, the transfer sheet P is sequentially picked up from the top by the sheet feeding cassette 5 provided at the bottom of the main body.
The sheet of paper P is sent to the PF roller 8 one by one, and the transfer paper P passing through the PF roller 8 is curled by the pre-curl roller 10 along the shape of the transfer drum 11. On the other hand, in the case of manual paper feeding, the transfer papers P are fed one by one from the manual paper feeding section 6 provided on the front surface of the main body, and are conveyed to the pre-curl roller 10 by the manual paper feeding roller 9. Then, the transfer paper P is curled by the pre-curl roller 10 along the shape of the transfer drum 11.

Next, as shown in FIG. 10, the transfer paper P is conveyed between the transfer drum 11 and the ground roller 12, and the electric charge accumulated in the semiconductive layer 27 of the transfer drum 11 becomes semiconductive. It is induced on the surface of the transfer paper P via the surface of the body layer 27 and the inner surface of the transfer paper P. Thereby, the transfer paper P is electrostatically attracted to the surface of the transfer drum 11. Then, the transfer paper P
11 is conveyed to a transfer point X, which is a pressure contact portion between the transfer drum 11 and the photoconductor drum 15, as shown in FIG. At this position, the toner image is transferred onto the transfer paper P by the charge of the toner formed on the photosensitive drum 15 and the charge on the surface of the transfer paper P.

At this time, the photosensitive drum 15 is charged, exposed, developed and transferred for each color. Therefore, the transfer paper P remains attracted to the transfer drum 11,
It rotates on the transfer drum 11, and one color is transferred every one rotation, and one full-color image is obtained by a maximum of four rotations. However, when obtaining a black-and-white image or a mono-color image, the transfer drum 11 may be rotated once.

Further, when all the toner images are transferred onto the transfer paper P, the transfer paper P is forced from the surface of the transfer drum 11 by the peeling claw 14 which is provided on the circumference of the transfer drum 11 so as to be separable from and in contact with the transfer paper P. Are peeled off and guided to the fixing guide 22. After that, the toner image on the transfer paper P is guided by the fixing guide 22 to the fixing roller 23,
Is fused and fixed on the transfer paper P by the temperature and pressure. Then, the fixed transfer paper P is discharged onto the discharge tray 25 by the discharge roller 24.

As described above, the transfer drum 11 is
The conductive layer 26 made of aluminum, the semiconductive layer 27 made of urethane foam, and the dielectric layer 28 made of polyvinylidene fluoride are formed from the inside. As a result, when a voltage is applied to the conductor layer 26, charges are sequentially induced from the conductor layer 26, and charges are accumulated in the semi-conductor layer 27. Then, when the transfer paper P is conveyed between the transfer drum 11 and the ground roller 12, the electric charge accumulated in the semiconductive layer 27 is moved to the transfer paper P, and the transfer paper P is transferred to the transfer drum 11. It is designed to be electrostatically attracted to.

Although cylindrical aluminum is used as the conductor layer 26, other conductors may be used. Although the semiconductive layer 27 is formed of urethane foam, an elastic body such as silicon may be used as another semiconductive material. The dielectric layer 28 is made of polyvinylidene fluoride, but a resin such as polyethylene terephthalate may be used as another dielectric.

Next, the configuration for performing the cleaning and charge removal operations on the transfer drum 11 will be described below. In order to perform the cleaning and static elimination operations, the present image forming apparatus, as shown in FIGS. 1, 3 and 4,
Roller type conductive brush 40, power supply unit 41, gear 42, motor 43, motor control unit 44 and motor drive power supply 45.
It has. The power supply unit 41 is for applying a voltage for destaticizing the transfer drum 11 to the roller-type conductive brush 40. The gear 42 transmits the driving force generated by the motor 43 to the roller-type conductive brush 40. The motor 43 is a roller-type conductive brush 40.
Generates a driving force for rotating. The motor control unit 44 controls the voltage of the motor drive power supply 45 and appropriately sets the rotation speed of the motor 43. The motor drive power supply 45 is connected to the motor 4 via the motor control unit 44.
3 is applied with a voltage.

Even after the transfer operation is completed and the transfer paper P is separated from the transfer drum 11 by the separation claw 14, the transfer drum 11 is still rotating. At this time, as shown in FIG.
The roller-type conductive brush 40 is moved so as to come into contact with the transfer drum 11 by a driving unit (not shown), and the charge removing operation is performed.

Table 3 shows the amount of crossing between the transfer drum 11 and the roller-type conductive brush 40 and the effect of static elimination on the transfer drum 11 corresponding to this amount of crossing. The crossing amount is the amount of the roller-type conductive brush 40 biting into the transfer drum 11.

[0058]

[Table 3]

From Table 3, in order to obtain the static elimination effect of the transfer drum 11, the roller type conductive brush 40 and the transfer drum 1 are used.
1 should be in contact with each other, and in particular, the crossing amount is 0.5 to
It can be seen that the range of 3.0 mm is more preferable.

A voltage is applied to the transfer drum 11 by the power supply section 32. In addition, the roller-type conductive brush 4
A voltage is applied to 0 by the power supply unit 41. When the charge removal operation is started, the residual charge on the surface of the transfer drum 11 and the roller-type conductive brush 40 escapes to the ground through the roller-type conductive brush 40 that is grounded via the power supply unit 41. Here, the voltage applied to the roller-type conductive brush 40 with respect to the transfer drum 11 and the transfer drum 11
Table 4 shows the results of the examination of the relationship with the static elimination effect.

[0061]

[Table 4]

The negative voltage in Table 4 indicates that the voltage applied to the transfer drum 11 by the power supply section 32 is higher than the voltage applied to the roller-type conductive brush 40.

From Table 4, the voltage applied to the roller-type conductive brush 40 is 0 to 1 more than the voltage applied to the transfer drum 11.
It can be seen that if the voltage is increased by 500 V, there is a static elimination effect. It is also preferable that the voltage is increased in the range of 500 to 1000V. This is for the following reason. Considering from the principle of the capacitor, when the polarized electrodes are made conductive, a current is generated and the transfer body is discharged. However, in the charge removal of the transfer body, if the transfer body and the charge removal brush are discharged at the same voltage, the charge cannot be completely removed. Therefore, by applying a high voltage to the charge eliminating brush from the transfer drum, the electric charges that are polarized and charged are attracted to the charge eliminating brush to completely eliminate the charge.

Transfer drum 11 and roller-type conductive brush 4
For example, 0 means that the transfer drum 1 is rotating at the same speed.
The residual electric charge of 1 is removed via the roller-type conductive brush 40. Further, the static elimination effect of the transfer drum 11 can be improved by providing the roller-type conductive brush 40 and the transfer drum 11 with a relative speed. here,
Table 5 shows the relationship between the speed difference of the roller-type conductive brush 40 with respect to the transfer drum 11 and the charge removal effect of the transfer drum 11.

[0065]

[Table 5]

From Table 5, regardless of the relative speed between the roller-type conductive brush 40 and the transfer drum 11, the transfer drum 11
It can be seen that there is an effect of removing the residual electric charge of 1., and it is particularly preferable that the relative speed difference is slowed by 50% or more or 40% or more. Further, although not shown in Table 5, the rotation speed of the transfer drum 11 is 20
When the roller-type conductive brush 40 is rotated at 0% or more faster, not only the charge removal effect but also the cleaning effect is improved.

Further, the static elimination effect changes depending on the contact amount of the brush in contact with the transfer drum 11, that is, the brush density. Table 6 shows the relationship between the brush density and the charge removal effect of the transfer drum 11 in the roller-type conductive brush 40.

[0068]

[Table 6]

From Table 6, if the roller-type conductive brush 40 has a brush density of 15,000 lines / cm ² or more, it is possible to obtain the effect of eliminating the residual charge of the transfer drum 11, and in particular, the brush density is 20000 lines / cm ^2. If it is more than cm ² ,
It turns out that it is more preferable.

The roller type conductive brush 40 presses the tip of the brush against the transfer drum 11. Therefore, the static elimination effect of the transfer drum 11 differs depending on the resistance value of the brush. The resistance value of this brush is such that the brush portion of the roller-type conductive brush 40 bites into the metal roller by 1.0 m.
m, the metal roller is rotated at a speed of 90 rpm, and the roller-type conductive brush 40 is rotated at 100 rpm.
It is rotated at a speed of, and a voltage of 100 V is applied to the brush portion for measurement.

Table 7 shows the relationship between the brush resistance value and the static elimination effect of the transfer drum 11.

[0072]

[Table 7]

From Table 7, if the brush resistance value is 40 kΩ or less, the charge eliminating effect of the transfer drum 11 can be obtained,
In particular, it is found that it is more preferable to set it to 36 kΩ or less. As the material of the brush, for example, a conductive material such as stainless fiber, carbon fiber, copper-dyed acrylic fiber, ST conductive non-woven fabric is used.

Next, the operation of removing the residual toner on the transfer drum 11, that is, the cleaning operation will be described. The cleaning operation is performed at the same time as the above static elimination operation. As shown in FIG. 1, in the roller-type conductive brush 40, a brush portion (not shown) abuts the surface of the transfer drum 11. Therefore, the residual toner adhering to the transfer drum 11 can be scraped off by the brush portion.
The toner adhering to the brush portion is blown off by a flicker bar (not shown) or the like, and is collected by a filter (not shown) by vacuum air from a blower or the like (not shown).

The above static elimination and cleaning operations are performed every time the transfer operation is completed, and are continued until the transfer drum 11 makes one revolution. After the above static elimination operation is completed, the roller-type conductive brush 40 is separated from the transfer drum 11. Further, since the roller-type conductive brush 40 has both the function of removing charge from the transfer drum 11 and the function of cleaning, the number of parts is small and the cost of the finished product can be reduced.

The roller type conductive brush 40 is shown in FIG.
As shown in, it is preferable to dispose the rotation axis of the roller-type conductive brush 40 in a state of being inclined with respect to the state in which it is orthogonal to the moving direction of the surface of the transfer drum 11. That is, when the rotation axis shown in b of FIG. 6B and the movement direction are not orthogonal to each other,
From the orthogonal case shown in a of FIG.
As shown in (c) and (d), the cross-sectional area of the roller-type conductive brush 40 when viewed from the traveling direction of the transfer drum surface (the direction of the arrow in the figure) becomes large, and the transfer of the roller-type conductive brush 40 is performed. It can be seen that the outer diameter seen from the traveling direction of the drum surface (the direction of the arrow in the figure) is large. As a result, the contact area of the roller-type conductive brush 40 with respect to the transfer drum 11 is increased, so that the static elimination effect is improved without increasing the diameter of the roller-type conductive brush 40.

[0077]

According to the image forming apparatus of the present invention, an image carrier on which a toner image is formed, a dielectric layer, a semiconductive layer and a conductive layer are sequentially arranged from the surface layer side to the inner layer side. By adhering the transfer papers that are stacked and adsorbed on the surface and contacting the image carrier, the transfer body that transfers the toner image formed on the image carrier to the transfer paper and the transfer paper are adsorbed. And a first voltage applying means for applying a voltage for transferring the toner image to the transfer paper to the conductive layer of the transfer body, and a direction opposite to the transfer paper conveyance direction from the image carrier. A grounded electrode member that is provided and is in contact with the surface of the transfer body via a transfer paper, and a roller-type charge eliminator that rotates while contacting with the dielectric layer of the transfer body to eliminate the charge on the dielectric layer. The same polarity as the voltage applied to the brush and the dielectric layer and this voltage Remote it is configured to and a second voltage applying means for applying a high voltage.

As a result, a voltage having the same polarity as the voltage applied to the conductor layer of the transfer member and a voltage higher than this voltage is applied to the charge removal brush, so that the charge removal brush reliably removes the residual charge on the surface of the transfer member. can do. This static elimination principle will be described below. Considering from the principle of the capacitor, when the polarized electrodes are made conductive, a current is generated and the transfer body is discharged. However, in the charge removal of the transfer body, if the transfer body and the charge removal brush are discharged at the same voltage, the charge cannot be completely removed. Therefore, if a voltage higher than that of the transfer body is applied to the charge eliminating brush, the polarized and charged charges can be attracted to the charge eliminating brush to completely eliminate the charge. As a result, due to the residual charge, the toner adheres to the surface of the transfer body and stains the back of the transfer paper, or the transfer paper is not attracted to the transfer body, resulting in poor transfer of the toner image to the transfer paper. It is possible to prevent such a situation from occurring and to supply an electric charge, which is advantageous for adsorbing the next transfer paper to the transfer body, to the surface of the transfer body.

An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect of the present invention, in which the static elimination brush has an axial direction orthogonal to a moving direction of the transfer body surface. It is arranged in a tilted state.

As a result, the contact area of the static elimination means with respect to the transfer means is increased, and the static elimination effect of the transfer means is improved without increasing the diameter of the static elimination means. Therefore, there is an effect that it is possible to prevent an increase in the size of the image forming apparatus and an increase in cost for improving the charge removal effect of the transfer unit.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of a static eliminator of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic overall configuration diagram showing an image forming apparatus provided with the static eliminator shown in FIG.

FIG. 3 is a schematic explanatory diagram showing a configuration of a rotation driving device of the static eliminator shown in FIG.

FIG. 4 is a schematic block diagram showing a control means of the rotation drive device shown in FIG.

FIG. 5 is an explanatory diagram showing an arrangement state of the roller-type conductive brush shown in FIG. 1 with respect to a transfer drum.

6A is a perspective view for explaining the effectiveness of the roller-type conductive brush shown in FIG. 5 depending on the arrangement direction;
The same figure (b) is the same plan view, the same figure (c) is the front view of the virtual cross section a shown in the same figure (a), and the same figure (d) is the same figure (a).
It is a front view of the virtual cross section b shown in FIG.

FIG. 7 is a schematic diagram showing a configuration near a transfer drum shown in FIG.

FIG. 8 is an exploded perspective view of the transfer drum shown in FIG.

9 is a vertical cross-sectional view showing another example of the structure of the transfer drum shown in FIG.

FIG. 10 shows a charging state of the transfer drum shown in FIG.
FIG. 6 is an explanatory diagram showing an initial state in which a transfer sheet is conveyed to a transfer drum.

FIG. 11 shows a charging state of the transfer drum shown in FIG.
FIG. 6 is an explanatory diagram showing a state in which a transfer sheet is conveyed to a transfer position of a transfer drum.

12 is an explanatory diagram showing a relationship among an effective image width, an effective transfer width, a photoconductor tube width, and a dielectric width of the transfer drum shown in FIG.

13 is a diagram showing charge transfer between the transfer drum and the photosensitive drum shown in FIG. 2, showing charge transfer when the width of each layer of the transfer drum is such that conductor layer <semiconductor layer <conductor layer. It is a figure.

FIG. 14 shows charge transfer between the transfer drum and the photoconductor drum shown in FIG. 2, in which the width of each layer of the transfer drum is smaller than the semiconductive layer <
It is explanatory drawing which shows a charge transfer when it becomes a dielectric material layer = conductor layer.

FIG. 15 is a schematic configuration diagram showing the vicinity of a transfer drum of a conventional image forming apparatus.

FIG. 16 is a schematic configuration diagram showing the vicinity of a transfer drum of another conventional image forming apparatus.

[Explanation of symbols]

 11 Transfer Drum (Transfer) 12 Ground Roller (Electrode Member) 15 Photosensitive Drum (Image Carrier) 26 Conductor Layer 27 Semiconducting Layer 28 Dielectric Layer 32 Power Supply Section (First Voltage Applying Means) 40 Roller Type Conduction Sex brush (static elimination brush) 41 power supply section (second voltage applying means)

Claims (2)

[Claims] 1. An image carrier on which a toner image is formed, and a dielectric layer, a semiconductive layer and a conductive layer are sequentially laminated from the surface layer side to the inner layer side, and while adhering the transfer paper to the surface. A transfer member that transfers the toner image formed on the image carrier to the transfer paper by transporting and bringing the toner image into contact with the image carrier, a voltage for attracting the transfer paper, and the toner image. A first voltage applying means for applying a voltage for transferring to the conductor layer of the transfer body, and a transfer sheet provided on the surface opposite to the transfer paper transport direction from the image carrier. A grounded electrode member that contacts via a roller; a roller-type charge removal brush that rotates while contacting the dielectric layer of the transfer body to remove the charge from the dielectric layer; and a voltage applied to the dielectric layer. A second power source that applies a voltage of the same polarity as the voltage but higher than this voltage. An image forming apparatus characterized by comprising a applying means. 2. The image according to claim 1, wherein the static elimination brush is arranged such that an axial direction thereof is inclined with respect to a state orthogonal to a moving direction of the transfer body surface. Forming equipment.