JP2014170115A - Power supply device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device capable of supplying power stably at a low cost.SOLUTION: In a power supply device, brush yarn 151 supplies power to an intermediate transfer belt 1, while a conductive brush 15a is in contact with the intermediate transfer belt 1, and relative displacement occurs between the brush yarn 151 and the intermediate transfer belt 1. The power supply device has an electrode plate 15b that includes an intrusion part A that intrudes into the inside of a base fabric 152 or protrudes penetrating through the base fabric 152 to have the base fabric 152 caught thereon, and has the base fabric 152 fixed thereto; and a protruding direction of the intrusion part A has a component in a direction reverse to a direction of movement in which the intermediate transfer belt 1 is displaced relative to the conductive brush 15a.

Description

  The present invention relates to a power supply apparatus and an image forming apparatus.

In an electrophotographic image forming apparatus, a latent image is formed on a photosensitive member, the latent image is developed with toner, and electrostatically transferred to form an image on a recording material. In such an image forming apparatus, a power supply device (unit) that supplies a voltage to a charging unit that charges the photoreceptor and a transfer unit that transfers toner is required. Further, it is necessary to provide a power supply device that supplies a voltage to the cleaning means that electrostatically collects excess toner or charges the toner.
These power supply devices include a non-contact power supply device installed to maintain a gap distance from the power-supplied member by using a discharge wire and a discharge needle as a power supply member, and a roller, brush, or sheet in contact with the power-supplied member. There is a contact power supply device that is configured as described above.

Japanese Patent Laid-Open No. 04-345186

When trying to realize the image forming apparatus as described above, there is a concern that the following problems will occur.
In a non-contact power supply device, since there is a tendency to generate a large amount of ion flow in a gap, there is a concern that a problem that ozone odor or the like is likely to occur occurs. In addition, the power supply device using rollers is likely to be expensive, and there is a concern that the power supply device using sheets may cause a problem that power supply failure occurs when there is a foreign object between the power supply members. The power supply device using a brush is highly resistant to foreign matter and can be reduced in cost by using a brush only in the vicinity of the contact portion. There is a concern that a problem may occur.
When a high voltage is supplied by power feeding, an attractive force is generated between the power-supplied member due to an electrostatic action, and therefore a stronger method for fixing the brush is required.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a power supply apparatus that can stably supply power at low cost.

In order to achieve the above object, the present invention provides:
Having a brush-like power supply member formed by fixing a plurality of conductive fibers to a base fabric;
In the power supply device in which the brush-like power supply member is in contact with the power-supplied member and relative movement occurs between the conductive fiber and the power-supplied member, the conductive fiber supplies power to the power-supplied member.
A fixing member that includes a projecting portion that penetrates into the base fabric or protrudes through the base fabric so that the base fabric is hooked;
The protruding direction of the protruding portion has a component in a direction opposite to the moving direction in which the power-supplied member moves relative to the brush-shaped power supply member.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the electric power feeder which can supply electric power stably at low cost.

Sectional drawing which shows schematic structure of the image forming apparatus of Example 1. FIG. 1 is a diagram for explaining a schematic configuration of a primary transfer apparatus according to Embodiment 1. FIG. The figure for demonstrating the electrically conductive brush of Example 1. FIG. Schematic which shows the fixed state of the electrically conductive brush of Example 1. FIG. 1 is a schematic perspective view showing the relationship between a primary transfer device and an intermediate transfer belt in Embodiment 1. FIG. Schematic showing the relationship between the primary transfer device of Example 1 and an intermediate transfer belt The figure which shows the result of having measured the frictional force of the intermediate transfer belt of Example 1, and a conductive brush. The figure for demonstrating the primary transfer apparatus of a comparative example The figure which shows the result of having compared Example 1 and the comparative example Schematic perspective view showing an electrode plate of Example 2 Schematic perspective view showing a comparative example of Example 2 Sectional drawing which shows schematic structure of the image forming apparatus of Example 3. FIG. Sectional drawing which shows schematic structure of the image forming apparatus of Example 4. FIG. Sectional drawing which shows schematic structure of the image forming apparatus of the modification of Example 4. FIG. The figure for demonstrating the charging brush roller of the modification of Example 4. FIG.

DETAILED DESCRIPTION Exemplary embodiments for carrying out the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.
The present invention has a power supply unit that supplies a high voltage to a power-supplied member that contacts with a relative speed, and a function of forming an image on a recording material such as a sheet while including the power supply unit. For example, the present invention relates to an image forming apparatus such as a copying machine or a printer.

Hereinafter, the image forming apparatus of Example 1 will be described.
[Configuration of Image Forming Apparatus]
FIG. 1 is a cross-sectional view illustrating a schematic configuration of the image forming apparatus according to the present exemplary embodiment.
In this embodiment, an image forming apparatus will be described using an intermediate transfer type 4-pass full-color printer as shown below.
First, toner images (developer images) are sequentially formed on the photosensitive drum 11 as a photosensitive member by developing devices 14a to 14d accommodated in the developing rotary 14, and each toner image is transferred to an intermediate transfer member (image carrier). Are formed so as to be superimposed on the intermediate transfer belt 1 (primary transfer). Then, the toner image on the intermediate transfer belt 1 is collectively transferred to the recording material P (secondary transfer). Here, the intermediate transfer belt 1 is an endless belt that is rotatably arranged.

The image forming apparatus of the present embodiment has four colors of yellow (Y), magenta (M), cyan (C), and black (Bk) in the developing devices 14a to 14d, respectively, and is not fixed on the recording material P. A fixing device (fixing device) 3 for fixing the toner image to the fixed image is provided.
In this embodiment, a mode in which the image forming speed (rotational peripheral speed of the photosensitive drum 11) is set to 120 mm / s will be described.

The photosensitive drum 11 is installed so as to be rotatable in the direction of the arrow R1 shown in the drawing, and a charging roller 12b for uniformly charging the surface is disposed on the outer peripheral surface of the photosensitive drum 11. The charging device 12 includes a charging power source 12a that supplies a charging voltage to the charging roller 12b and a charging roller 12b.
On the downstream side of the charging roller 12b in the rotation direction of the photosensitive drum 11, a laser exposure unit 13 is disposed as an exposure unit for irradiating the surface of the photosensitive drum 11 with laser light modulated by a printer engine control unit (not shown). ing.
Further, on the downstream side of the laser irradiation position in the rotation direction of the photosensitive drum 11, a developing rotary 14 that accommodates developing devices 14a to 14d that develops electrostatic latent images on the surface of the photosensitive drum 11 formed by laser exposure is disposed. Has been.

  A primary transfer device 16 serving as a power supply unit (power supply device) that forms a primary transfer portion together with the photosensitive drum 11 is disposed at a position (transfer position) facing the photosensitive drum 11 via the intermediate transfer belt 1. Yes. The primary transfer device 16 is provided with a brush unit 15 which will be described later, which is a feature of the present embodiment. The brush unit 15 is connected to a primary transfer power supply 16a for supplying a primary transfer voltage and current. . Here, the intermediate transfer belt 1 corresponds to a power-supplied member that is fed by a power feeding unit.

The intermediate transfer belt 1 is stretched around three rollers, that is, a driving roller 1a, a tension roller 1b, and a secondary transfer counter roller 1c, and is disposed so as to contact the photosensitive drum 11.
The intermediate transfer belt 1 is rotationally driven in the direction of the arrow R3 shown in FIG. 1 when the driving roller 1a rotates in the direction of the arrow R2 shown in FIG. A drum cleaner 17 is disposed on the downstream side of the primary transfer device 16 in the rotation direction of the photosensitive drum 11. Further, a cleaning device (belt cleaner) 4 for removing toner remaining on the intermediate transfer belt 1 is disposed on the surface of the intermediate transfer belt 1 so as to come into contact therewith.

Next, the schematic configuration of each member will be described.
The photosensitive drum 11 is obtained by laminating a conductive support base, a charge generation layer, and a charge transport layer on the surface of an aluminum cylinder having a thickness of 1 mm and a diameter of 30 mm. It corresponds to 5000 sheets.
As the intermediate transfer belt 1, a seamless belt body made of an ion conductive resin and having a volume resistivity of 8 × 10 ⁹ Ω · cm (normal temperature and humidity environment) and a film thickness of 70 μm is used. The drive roller 1a is a 20 mm diameter aluminum cylinder coated with 100 μm thick urethane rubber, and can obtain a good gripping force with the back surface of the intermediate transfer belt 1. The tension roller 1b is an iron roller having a diameter of 15 mm and applies a tension tension of 30 N to the intermediate transfer belt 1. The secondary transfer counter roller 1c is configured by covering an aluminum cylinder having a diameter of 20 mm with a conductive EPDM rubber having a thickness of 0.5 mm.
The primary transfer device will be described later.

The image forming operation of the image forming apparatus configured as described above will be described using yellow image formation as an example.
The photosensitive drum 11 is configured by forming a photoconductive layer on the surface of an aluminum cylinder. Then, the photosensitive drum 11 is in the process of rotating the direction of arrow R1 shown in FIG. 1, the charging roller 12b, which is supplied with from the charging voltage (-1100 V) charging power source 12a, about a uniform _{V D} potential surface Charged to -550V.

Next, the image information sent from the personal computer (not shown) is converted into a signal corresponding to the laser exposure amount, and the laser exposure device 13 performs image exposure in response to this. As a result, the potential of the portion to the toner image is formed on the potential difference decays from V _D potential of the background portion is formed, an electrostatic latent image corresponding to a yellow image component of the original image on the surface of the photosensitive drum 11 is formed Is done. Maximum amount of light given moiety potential attenuation to about -120V is _{V L} potential.

In the developing device 14a, a voltage (developing voltage) between the _VD potential and _VL is supplied from the developing power source 18 to the toner supply unit, so that the negatively charged yellow toner is electrostatically latent on the photosensitive drum. It moves selectively only to the part where the image is formed. By such a developing operation, the electrostatic latent image on the photosensitive drum 11 is visualized as a yellow toner image.
The obtained yellow toner image is primarily transferred onto the intermediate transfer belt 1 by the primary transfer voltage (+100 to +2000 V) supplied from the primary transfer device 16. The primary transfer residual toner adhering to the surface of the photosensitive drum 11 after the primary transfer is removed by the drum cleaner 17 and used for the next image formation.

  When the yellow image formation is completed, the developing rotary 14 rotates and the magenta developing device 14b, which is the next developing color, comes into contact with the photosensitive drum 11, and image formation is performed on the photosensitive drum 11 as in the previous yellow. These image formations are performed by controlling the timing so that each color appropriately overlaps the intermediate transfer belt 1 by primary transfer.

By repeating the above process, toner images are sequentially transferred to the intermediate transfer belt 1 in the order of yellow, magenta, cyan, and black, and a full-color image is formed on the intermediate transfer belt 1.
Then, at the stage where the black toner image is transferred, the secondary transfer roller 2 and the cleaning device 4 are in the middle immediately after the rear end of the image on the intermediate transfer belt 1 passes the contact position of the secondary transfer roller 2. Abutted on the transfer belt 1. At the timing when the leading edge of the full color toner image on the intermediate transfer belt 1 reaches the secondary transfer roller 2, the recording material P is inserted into the secondary transfer portion (nip portion) formed by the secondary transfer roller 2 and the intermediate transfer belt 1. The
A secondary transfer voltage is supplied from the secondary transfer power source 21 to the secondary transfer roller 2, whereby the toner images on the intermediate transfer belt 1 are secondarily transferred onto the recording material P all at once.

The secondary transfer residual toner adhering to the surface of the intermediate transfer belt 1 after the secondary transfer is removed by the cleaning device 4 and the secondary transfer roller 2 and the cleaning device 4 are completed as soon as the secondary transfer process to the recording material P is completed. Are separated from the intermediate transfer belt 1 to prepare for the next image formation.
The unfixed toner image formed (supported) on the recording material P by passing through the secondary transfer portion is heated and pressurized by the fixing device 3 to become a fixed image.

[Regarding the primary transfer device 16]
FIG. 2 is a diagram for explaining a schematic configuration of the primary transfer device 16.
The primary transfer device 16 includes a brush unit 15 having a conductive brush 15a as a brush-like power supply member having a flexible form, and a pressurizing mechanism thereof. The brush unit 15 mainly includes a conductive brush 15a formed by fixing conductive fibers to a base cloth, an electrode plate 15b that supplies power thereto, a pedestal 15c that supports them, and a pressure plate 15d. Here, the electrode plate 15b and the pedestal 15c constitute a fixing member.
In this embodiment, the dimension W of the conductive brush 15a in the direction (hereinafter referred to as the short direction) installed in parallel to the moving direction (rotational direction, transport direction) of the intermediate transfer belt 1 is W = 7 mm. The dimension L of the conductive brush 15a in the direction perpendicular to the moving direction of the intermediate transfer belt 1 (the direction orthogonal to the moving direction of the intermediate transfer belt 1, hereinafter referred to as the longitudinal direction) is L = 230 mm.
By setting W = 7 mm, a nip portion having a sufficient width can be formed between the intermediate transfer belt 1 and by setting L = 230 mm, the width is sufficient even for the width of an A4 size recording material. Image formation can be performed. The fiber length h of the conductive brush 15a is 5 mm.
The conductive brush 15a of the present embodiment has a configuration in which the dimension W in the short direction is longer than the fiber length h. This is because if the fiber length h of the conductive brush 15a is long, the nip position may be shifted when the conductive brush 15a is inclined due to the movement of the intermediate transfer belt 1.

FIG. 3 is a diagram for explaining the conductive brush 15a of the present embodiment.
As the conductive brush 15a, conductive fibers are arranged at a predetermined density, and a pile fabric type or an electrostatic flocking type can be used. As shown in FIG. 3, the pile woven brush is made (manufactured) by weaving a conductive pile yarn that becomes a brush yarn 151 as a conductive fiber into a gap between a base fabric 152 made of a warp yarn 1501 and a weft yarn 1502. It is. In order to enable electrical connection between the brush threads 151, the base cloth 152 is impregnated with a conductive resin or a conductive adhesive in a later step, or the base cloth 152 itself is made of conductive fibers. There are ways to combine them.
Moreover, the brush by electrostatic flocking is a method in which a short fiber is adsorbed on a base cloth to which an adhesive has been applied in advance by using an electrostatic attraction (electrostatic adsorption) force in a high-voltage electrostatic field and vertically cast.

Examples of the conductive fiber include nylon or polyester in which carbon powder is dispersed, and the single yarn thickness is 2 to 15 T (tex), the diameter is 10 to 40 μm, and the dry strength is 1 to 3 cN / T. Those within range are suitable for woven fabrics. The fiber resistivity ρfiber is preferably in the range of 10 to 10 ⁸ Ωcm. The resistivity ρfiber is measured by the following method. A bundle of 50 fibers is made, a metal probe is brought into contact with the surface of the bundle at an interval of about 1 cm, a resistance value Rfiber is measured under an applied voltage of 100 V using a high resistance meter, Advantest R8340A, and the resistivity is calculated by the following equation. ρfiber is calculated.
ρfiber = Rfiber × (fiber diameter / 2) ² × 3.14 × 50

In this example, in the brush that is not in contact, the direction in which the fibers extend from the base fabric surface is referred to as the raising direction. The fiber length in the raising direction from the base fabric (substrate) of each fiber can be 1 to 5 mm, and the arrangement density on the base fabric (substrate) can be 5000 to 50000 pieces / cm ² .
The primary transfer device 16 in this embodiment uses a conductive brush 15a in which a pile woven fabric is constituted by brush yarns 151 and a base cloth 152 having the following specifications, and the base cloth 152 is impregnated with a conductive resin and back-coated. Yes.

<Brush thread specifications>
・ Material: Nylon fiber with carbon powder dispersed ・ Single yarn thickness: 7T
・ Fiber diameter: 28μm
・ Pile thread thickness: 170T
・ Resistivity: 10 ⁶ Ωcm
・ Fiber length: 5mm
Array density: 10850 / cm ²
<Specifications of base yarn>
・ Material: Polyester fiber ・ Single thread thickness: 7T
・ Fiber diameter: 28μm
・ Thread thickness: 270T
・ Resistivity: 10 ¹³ Ωcm or more

As shown in FIG. 2, the tip of the electrode plate 15 b is formed in a sharp shape as the intrusion portion A, and the electrode plate 15 c extends from the through hole H provided substantially at the center in the longitudinal direction and upstream in the short direction of the pedestal 15 c. 15b of intrusion part A is comprised so that it may protrude.
The protruding amount of the intrusion portion A needs to be lower than the brush length when the brush thread 151 is pressed against the intermediate transfer belt 1, and is set to 0.5 to 0.9 mm in this embodiment. Thereby, even when the brush thread 151 is pressed against the intermediate transfer belt 1, the intrusion portion A does not contact the intermediate transfer belt 1. Here, the intrusion portion A corresponds to a protruding portion that protrudes so that the base fabric 152 is caught. The intrusion part A may enter the inside of the base cloth 152 so that the base cloth 152 is caught, or may penetrate the base cloth 152.

FIG. 4 is a schematic view showing a fixed state of the conductive brush 15a of the present embodiment. FIG. 5 is a schematic perspective view showing the relationship between the primary transfer device 16 and the intermediate transfer belt 1 of the present embodiment in a state where the intermediate transfer belt 1 is partially broken. In FIG. 4, for convenience of explanation, the brush thread 151 around the intrusion portion A is omitted.
The base fabric 152 is placed on the base 15c and the electrode plate 15b combined as described above, and the conductive brush 15a is fixed by being fixed with an adhesive. At this time, as shown in FIG. 4, since the intruding portion A of the electrode plate 15b has entered the base cloth 152, the electrical connection between the electrode plate 15b and the brush thread 151 is ensured through the back coat. Secured.
The brush unit 15 having the conductive brush 15a, the electrode plate 15b, and the pedestal 15c in this way is urged by the urging means 19 as shown in FIGS. The intermediate transfer belt 1 is disposed so as to contact the back surface (inner peripheral surface). At this time, the conductive brush 15 a contacts the back surface of the intermediate transfer belt 1 at a position facing the photosensitive drum 11. In this embodiment, the pressing force (biasing force) of the urging means 19 is set to 2N.

By contacting the back surface of the intermediate transfer belt 1, the brush thread 151 of the conductive brush 15a is deformed, and the position where the restoring force and the pressure applied by the urging means 19 are balanced is the position in the pressing direction of the brush unit. In this manner, a primary transfer portion (nip portion) is formed by the photosensitive drum 11, the intermediate transfer belt 1, and the primary transfer device 16.
Thus, in the primary transfer device 16, the brush yarn 151 is in the intermediate transfer belt while the conductive brush 15 a is in contact with the intermediate transfer belt 1 and relative movement occurs between the brush yarn 151 and the intermediate transfer belt 1. 1 is configured to supply power. (The primary transfer device 16 is used so that the brush thread 151 of the conductive brush 15a moves (relatively moves) while being in contact with the intermediate transfer belt 1, and supplies power to the intermediate transfer belt 1.)

[About deformation of base fabric]
In the present embodiment, as described above, the base fabric 152 is made of a relatively thick thread, and further, the back coat is applied to increase the rigidity and to be strong against deformation (Gurley stiffness: 5.5 mN). However, since it is a woven fabric, there is a concern of deformation during use. The force to be deformed is mainly a force acting on the conductive brush 15a described below (hereinafter referred to as frictional force).

By pressing the conductive brush 15a against the intermediate transfer belt 1, friction occurs between the conductive brush 15a and the intermediate transfer belt 1 when the intermediate transfer belt 1 moves, and the intermediate transfer belt 1 moves downstream in the moving direction. In addition, a frictional force is generated to shift the conductive brush 15a together with the base cloth 152. Further, the conductive brush 15a is a power supply member, and when a high voltage is applied, the electrostatic adsorption force between the conductive brush 15a and the intermediate transfer belt 1 increases, and this frictional force tends to further increase.
FIG. 6 is a schematic view showing the relationship between the primary transfer device 16 and the intermediate transfer belt 1 of the present embodiment in a state where the intermediate transfer belt 1 is partially broken. Also in FIG. 6, the brush thread 151 around the intrusion A is omitted for convenience of explanation.
In this embodiment, as shown in FIG. 6, the intruding portion A of the electrode plate 15b is intruded in the direction opposite to the moving direction of the intermediate transfer belt 1 (upstream in the moving direction of the intermediate transfer belt 1). The frictional force acts to penetrate the intrusion portion A deeper. Here, the intrusion portion A will be described in more detail. The intrusion direction of the intrusion portion A (the protruding direction of the tip) may be any component as long as it has a component opposite to the moving direction of the intermediate transfer belt 1. More preferably, it is parallel to the moving direction of the transfer belt 1.

FIG. 7 shows the result of measuring the frictional force acting between the intermediate transfer belt 1 and the conductive brush 15a when the intermediate transfer belt 1 is moved at a conveyance speed of 120 mm / s.
When the pressure applied to the intermediate transfer belt 1 of the conductive brush 15a is set to 1N or 2N, the force for driving the intermediate transfer belt 1 when a voltage of 0V, 500V, or 1000V is applied to the conductive brush 15a. The friction force was calculated.
When the applied pressure is increased, the frictional force increases accordingly, and the increase in the frictional force is confirmed by increasing the applied voltage. It is considered that the frictional force increased by this pressurization and voltage application causes the base fabric 152 to be deformed.

FIG. 8A is a diagram for explaining a primary transfer apparatus in which a conductive brush 15a is directly fixed to an electrode plate 15b with a conductive adhesive as a comparative example. In addition, in the structural member shown to Fig.8 (a), the same code | symbol as a present Example is attached | subjected for convenience of explanation.
The flow stop step S provided in the downstream portion of the pedestal 15c in the moving direction of the intermediate transfer belt 1 is effective in preventing the entire conductive brush 15a from slipping off the pedestal 15c. However, as the intermediate transfer belt 1 moves, a large frictional force is generated in the power supply member as described above. Therefore, as shown in FIG. 8B, in the moving direction of the intermediate transfer belt 1, the upstream side of the conductive brush 15a. There is a concern that a phenomenon may occur in which the portion is moved downstream.

When such a phenomenon occurs, the conductive brush 15a is displaced from the proper transfer position, so that not only the transfer efficiency is reduced and abnormal discharge occurs, but also the conductive brush and the 15a electrode plate 15b are good. There is a possibility that improper contact is not obtained and transfer failure occurs.
Therefore, in this embodiment, as described above, the tip of the electrode plate 15b is inserted into the upstream side in the moving direction of the intermediate transfer belt 1 (the short direction of the base fabric 152) to prevent this deformation. Yes.

[Comparison experiment]
The result of comparison with the present embodiment shown in FIG. 2 will be described using the configuration shown in FIG. 8 as a comparative example. FIG. 9 shows that an image forming apparatus using a primary transfer device of each configuration is used to pass an image with a pattern of 4% image ratio in three environments: a high temperature and high humidity environment, a normal temperature and normal humidity environment, and a low temperature and low humidity environment. The transition of the primary transfer residual ratio in the case of evaluation is shown. The primary transfer residual ratio is a ratio of density (optical density, OD value) before and after the primary transfer on the photosensitive drum 11, and the larger the value, the lower the transfer efficiency. Here, the high temperature and high humidity environment, the normal temperature and normal humidity environment, and the low temperature and low humidity environment refer to environments of 15 ° C./10%, 23 ° C./50%, and 30 ° C./80%, respectively.

In the configuration of the present embodiment, the transfer efficiency does not decrease even when the number of sheets to be passed increases, whereas in the comparative example, the transfer efficiency decreases as the sheet passes. This indicates that the base cloth 152 of the conductive brush 15a used in the primary transfer device is shifted downstream due to deformation and the ability as a power supply member is reduced.
Furthermore, when the primary transfer device of the comparative example that has passed 50,000 sheets is replaced with the one of this example, the primary transfer residual ratio is greatly improved, and the configuration of this example is effective against the deformation of the base fabric 152. It turns out that it is excellent.

In a high-temperature and high-humidity environment, the resistance of the intermediate transfer belt 1 and the charge amount of the toner decrease. Therefore, in order to obtain high transfer efficiency, the primary transfer voltage is set low. Tend to be. On the other hand, in the conventional example that relies only on the rigidity of the pressure-sensitive adhesive or the base fabric, some deformation occurs, and it is considered that the transfer efficiency is lowered.
On the other hand, in a low-temperature and low-humidity environment, since the resistance of the member is high, it is necessary to apply a high primary transfer voltage of +1000 to +2000 V, and the electrostatic attraction force increases and the frictional force related to the deformation of the base fabric. Will increase. As a result, it is considered that the base fabric is greatly deformed as shown in FIG.

In the present embodiment, the electrode plate 15b is configured to invade with a component in the direction opposite to the direction (displacement direction) of the force applied to the base fabric 152 by the frictional force with respect to the base fabric 152.
According to this configuration, when the force by which the base cloth 152 moves in the direction of displacement increases due to the application of a high voltage, the reaction force by the electrode plate 15b increases to suppress deformation, and the contact pressure between the base cloth 152 and the electrode plate 15b. As a result, the effect of obtaining better electrical contact can be obtained.
This effect maintains the position and electrical contact of the conductive brush 15a, which is a power supply member, even when paper passing is repeated, and more stable transfer efficiency can be obtained as shown in FIG. Therefore, it is possible to provide a power supply unit that can stably supply power at low cost and an image forming apparatus that can form a uniform and high-quality image.

Example 2 will be described below. In the present embodiment, constituent parts different from those in the first embodiment will be described, and description of constituent parts similar to those in the first embodiment will be omitted.
FIG. 10 is a schematic perspective view showing the electrode plate 15b of the present embodiment.
In the present embodiment, in contrast to the structure of the first embodiment, the structure of the conductive brush 15a of the primary transfer device 16 and the electrode plate 15b have an intrusion portion A in the longitudinal direction as shown in FIG. It is different in that it is arranged multiple times.
In this embodiment, the brush yarn 151 and the base fabric 152 are formed using the same yarn as described below. By using the base fabric 152 as a conductive yarn, it is possible to obtain good electrical contact between the pile yarn and the electrode plate 15b without applying a conductive adhesive or the like.

<Brush thread specifications>
・ Material: Nylon fiber with carbon powder dispersed ・ Single yarn thickness: 7T
・ Fiber diameter: 28μm
・ Thickness of pile yarn: 150T
・ Resistivity: 10 ⁶ Ωcm
・ Fiber length: 5mm
Array density: 10850 / cm ²
<Specifications of base yarn>
・ Material: Nylon fiber with carbon powder dispersed ・ Single yarn thickness: 7T
・ Fiber diameter: 28μm
・ Thread thickness: 150T
・ Resistivity: 10 ⁶ Ωcm

On the other hand, when the above-mentioned same thread is used for the brush thread and the base cloth thread, the softness that is not convenient as the brush thread 151 causes the rigidity of the base cloth 152 to decrease.
In this embodiment, the conductive brush 15a is fixed at the plurality of intrusion portions A using the electrode plate 15b shown in FIG. 10 in which a plurality of intrusion portions A are formed by cutting and raising a part of the sheet metal. The plurality of intrusion portions A of the electrode plate 15b penetrate the base cloth 152 in the longitudinal direction, respectively, and the base cloth 152 having low rigidity can be reliably positioned in the same manner as in the first embodiment by suppressing deformation. And electrical contact can be obtained.

For comparison, a description will be given of a case where paper passing is repeated with a configuration in which the conductive brush 15a is simply attached to the base 15c with an adhesive using the electrode plate 15f having no intrusion portion A.
FIG. 11 shows this comparative example as in FIG. In addition, in the structural member shown in FIG. 11, the same code | symbol as a present Example is attached | subjected for convenience of explanation.
If the sheet passing is repeated using the electrode plate 15f that does not have the intrusion portion A and the conductive brush 15a is simply attached to the pedestal 15c with an adhesive, as shown in FIG. The brush 15a may be carried downstream. This tendency becomes remarkable when a high voltage is applied and the electrostatic attraction force increases.
When the state shown in FIG. 11 is reached, the position of the conductive brush 15a is changed and transfer is not performed normally, or the conductive brush 15a is peeled off from the electrode plate 15f, and the conductive brush 15a has a sufficient function as a power supply member. It will not work.

In contrast, in the present embodiment, the plurality of intrusion portions A fix the base fabric 152, thereby ensuring the accuracy of the shape and position of the conductive brush 15a. Furthermore, by utilizing the increase in frictional force due to the application of a high voltage as the penetration force of the penetration portion A with respect to the base cloth 152, it is possible to increase the contact pressure between the base cloth 152 and the electrode plate 15b to obtain good electrical contact. it can.
Thereby, even when paper passing is repeated, the position and electrical contact of the conductive brush 15a can be maintained.
Furthermore, in the present embodiment, there is an advantage that voltage can be uniformly supplied from the intrusion portion A to the conductive brush 15a by the plurality of intrusion portions A being distributed over the longitudinal direction.

Example 3 will be described below. In the present embodiment, constituent parts different from those in the first and second embodiments will be described, and description of constituent parts similar to those in the first embodiment will be omitted.
FIG. 12 is a cross-sectional view illustrating a schematic configuration of the image forming apparatus according to the present exemplary embodiment.
In this embodiment, as shown in FIG. 12, the brush unit 15 having the conductive brush 15 a used in the primary transfer device 16 of Embodiment 2 is used for the electrostatic cleaning device 4 of the intermediate transfer belt 1. Here, the electrostatic cleaning device 4 corresponds to a charging device that charges toner formed on the surface of the intermediate transfer belt 1.
The conductive brush 15a of the present embodiment is composed of the following thread.

<Brush thread specifications>
・ Material: Nylon fiber with carbon powder dispersed ・ Single yarn thickness: 7T
・ Fiber diameter: 28μm
・ Thickness of pile yarn: 150T
・ Resistivity: 10 ¹¹ Ωcm
・ Fiber length: 5mm
Array density: 10850 / cm ²
<Specifications of base yarn>
・ Material: Nylon fiber with carbon powder dispersed ・ Single yarn thickness: 7T
・ Fiber diameter: 28μm
・ Thread thickness: 150T
・ Resistivity: 10 ¹¹ Ωcm

Next, the electrostatic cleaning operation will be described.
[Regarding electrostatic cleaning]
The removal of the residual toner remaining on the intermediate transfer belt 1 of the present embodiment is based on the primary transfer unit using the charged polarity of the residual toner and electrostatic removal by the electrostatic cleaning device 4.
The charged state of the residual toner remaining on the intermediate transfer belt 1 after the secondary transfer is often in a state where both positive and negative polarities are mixed, and the ratio varies depending on the secondary transfer conditions. This is presumably because the discharge state due to the secondary transfer voltage with respect to the negative polarity toner before the secondary transfer varies depending on the environment in which the image forming apparatus is used (installed) and the recording material.

For these residual toners, the electrostatic cleaning device 4 performs a normal operation performed in parallel during the image forming process and a refresh operation performed after the end of the image forming process, thereby remaining on the intermediate transfer belt 1. Remove (clean) toner.
In the normal operation, the residual toner is recharged and collected by the positive high voltage supplied to the conductive brush 15a of the electrostatic cleaning device 4. In the refresh operation, the toner accumulated by the collection of the normal operation is returned to the intermediate transfer belt 1. In this embodiment, the toner (residual toner) on the intermediate transfer belt 1 corresponds to a power-supplied member.

In normal operation, a voltage of +2000 to +4000 V is supplied from the recharging power supply 4a to the brush unit 15 of the electrostatic cleaning device 4. As a result, a charge of reverse polarity is supplied to the toner remaining on the intermediate transfer belt 1, and at the same time, a recovery action is exerted on the toner that is not reversed, so that the toner that is not reversed is electrostatically charged. It is taken into the cleaning device 4.
Therefore, most of the toner that has passed through the electrostatic cleaning device 4 during normal operation is a reversal toner whose charge polarity is reversed. These reversal toners are returned from the intermediate transfer belt 1 to the photosensitive drum 11 by the primary transfer voltage at the time of image formation, and are removed from the intermediate transfer belt 1. In this embodiment, a primary transfer portion is formed by the primary transfer roller 16 b of the primary transfer device 16, the intermediate transfer belt 1, and the photosensitive drum 11.

On the other hand, the toner collected in the electrostatic cleaning device 4 during the normal operation is returned to the intermediate transfer belt 1 by a refresh operation performed after a series of image forming steps is completed, and the photosensitive drum 11 in the primary transfer unit. It is removed by reverse transcription (moving).
At that time, a negative polarity voltage of −1000 to −2000 V is supplied to the conductive brush 15 a of the electrostatic cleaning device 4, whereby the negatively collected toner is returned onto the intermediate transfer belt 1 by electrostatic repulsion. It is. Further, the negative transfer (reverse polarity) high voltage is also applied to the primary transfer device 16, whereby the toner on the intermediate transfer belt 1 is returned to the photosensitive drum 11.
The toner returned to the photosensitive drum 11 is finally collected by the drum cleaner 17 to complete the cleaning process.

By performing the operation as described above, the residual toner on the intermediate transfer belt 1 can be continuously cleaned and finally collected and collected by the drum cleaner 17.
The conductive brush 15a used in this embodiment has an advantage that it can maintain the recharging action even when the residual toner is collected by the gap between the brush yarns in that it has a collecting action in the cleaning operation. There is.

As described above, the voltage applied to the conductive brush 15a during the normal operation of the present embodiment is applied to the conductive brush 15a used in the primary transfer device as in the second embodiment in order to enable discharge of the toner. Is set higher than the voltage to be Therefore, in this embodiment, compared with the second embodiment, the electrostatic attractive force acting between the intermediate transfer belt 1 and the conductive brush 15a is increased, and a higher frictional force is generated.
Also in the present embodiment, the position of the conductive brush 15a can be maintained by the effect of the intrusion portion A of the electrode plate 15b shown in FIG. 10, and the electrical contact between the electrode plate 15b and the conductive brush 15a can be secured. The above charging (discharging) and recovery action can be obtained more stably.

Example 4 will be described below. In the present embodiment, constituent parts different from those in the first to third embodiments will be described, and the description of the same constituent parts as those in the first to third embodiments will be omitted.
FIG. 13 is a cross-sectional view illustrating a schematic configuration of the image forming apparatus according to the present exemplary embodiment.
In this embodiment, as shown in FIG. 13, a brush unit 15 having a conductive brush 15 a used in the primary transfer device 16 of Embodiment 2 is used for the charging device 12 of the photosensitive drum 11. The conductive brush 15a is fixed in the same configuration as the electrode plate 15b shown in FIG. In this embodiment, the photosensitive drum 11 corresponds to a power supplied member.

When the brush unit 15 (conductive brush 15a) is used in the charging device 12, even when dirt is present on the photosensitive drum 11, dirt can be accumulated due to the gaps in the brush thread, so that the charging ability is immediately reduced. There is a feature that there is no problem of doing. On the other hand, the conductive brush 15a is also a member that discharges by providing a potential difference with the photosensitive drum 11. When the potential difference is formed, a large frictional force is generated as in the above-described embodiment.
According to the configuration of the present embodiment, even when a frictional force is generated, the position of the conductive brush 15a can be maintained, and electrical contact between the electrode plate 15b and the conductive brush 15a can be ensured, The above charging (discharging) can be obtained more stably.

[Modification]
Below, the modification of a present Example is demonstrated.
FIG. 14 is a cross-sectional view illustrating a schematic configuration of a modified image forming apparatus.
When a brush-like member is used as a charging member for charging the photosensitive drum 11, uneven brush sweeping may be a problem. This phenomenon is a problem when the required image resolution is high with respect to the brush density, and tends to be particularly noticeable in a halftone image or the like.

This modification is for suppressing the occurrence of this phenomenon, and is characterized in that the brush-like power supply member is formed into a rotating body to form a charging brush roller 22 as shown in FIG. . In this modification, the brush thread 151 is formed so as to extend from the outer peripheral surface of the charging brush roller 22 main body (rotary body main body) toward the outer diameter direction.
The charging brush roller 22 is driven at the peripheral speed of the photosensitive drum 11 in the direction opposite to the rotation direction of the photosensitive drum 11 (in the direction of the arrow R3) to increase the peripheral speed difference, thereby allowing the photosensitive drum 11 and the brush to contact each other. Have a lot. By adopting such a configuration, it is possible to increase the frequency of brush sweep unevenness and make it inconspicuous even in a halftone image.

FIG. 15 is a view for explaining the charging brush roller 22 of this modification. Also in FIG. 15, for convenience of explanation, the brush thread 151 around a part of the intrusion portion A is omitted.
The charging brush roller 22 is configured such that a plurality of cut and raised portions B are provided on the cored bar 22b, and the conductive brush 22a is provided so as to cover the periphery thereof via an adhesive layer.
The difference in peripheral speed between the charging brush roller 22 and the photosensitive drum 11 generates a frictional force, and this frictional force acts in a direction in which the cut-and-raised portion B enters the base cloth of the conductive brush 22a. With this action, even if the charging brush roller 22 is used repeatedly, good electrical contact between the cored bar 22b and the conductive brush 22a can be maintained.
As described above, also in this modification, it is possible to maintain a stable charging ability while achieving high image quality.

  15a ... conductive brush, 15b ... electrode plate, 15c ... pedestal, 151 ... brush thread, 152 ... base cloth, A ... intrusion part

Claims (11)

Having a brush-like power supply member formed by fixing a plurality of conductive fibers to a base fabric;
In the power supply device in which the brush-like power supply member is in contact with the power-supplied member and relative movement occurs between the conductive fiber and the power-supplied member, the conductive fiber supplies power to the power-supplied member.
A fixing member that includes a projecting portion that penetrates into the base fabric or protrudes through the base fabric so that the base fabric is hooked;
The power feeding apparatus according to claim 1, wherein a projecting direction of the projecting portion has a component in a direction opposite to a moving direction in which the power-supplied member moves relative to the brush-shaped power feeding member. The conductive fiber has a predetermined length in the moving direction and a direction orthogonal to the moving direction, and contacts the power-supplied member.
The power feeding device according to claim 1, wherein a plurality of the projecting portions are arranged along the orthogonal direction.   The power feeding device according to claim 1, wherein discharge is performed from the brush-shaped power feeding member to the power-supplied member. In an image forming apparatus having a charging device for charging a photoconductor,
An image forming apparatus comprising the power supply device according to claim 1, wherein the power supply device supplies power to the photoconductor as the power-supplied member. The brush-like power supply member is a rotating body,
The image forming apparatus according to claim 4, wherein the conductive fibers are formed so as to extend in an outer diameter direction from an outer peripheral surface of the rotating body main body. In an image forming apparatus having a transfer device for transferring a toner image formed on the surface of a photoreceptor to an intermediate transfer member,
An image forming apparatus comprising: the power feeding device according to claim 1 that feeds power to the intermediate transfer member as the transfer device. In an image forming apparatus having a charging device for charging toner formed on the surface of an intermediate transfer member,
4. The image forming apparatus according to claim 1, wherein the charging device includes the power feeding device according to claim 1 that feeds power to the toner as the power-supplied member. 5.   The image forming apparatus according to claim 6, wherein the intermediate transfer member is an endless intermediate transfer belt that rotates and the brush-shaped power feeding member contacts an inner peripheral surface of the intermediate transfer belt. apparatus.   The said brush-shaped electric power feeding member is produced by weaving a conductive pile yarn as the plurality of conductive fibers in the gap between the base fabrics, according to any one of claims 1 to 8. Image forming apparatus.   9. The image forming apparatus according to claim 1, wherein the brush-shaped power supply member is formed by adsorbing the plurality of conductive fibers to the base cloth by electrostatic adsorption. 10. The image forming apparatus according to claim 1, wherein a protruding direction of the protruding portion is parallel to a moving direction of the power-supplied member.

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