JP2010044331A - Electrophotographic type image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which simultaneously eliminates a moth-eaten image, image irregularities and transfer dust, by applying an adhesion force by pressure in a secondary transfer nip and reducing the adhesion force through vibration, in a part of the secondary transfer nip or, preferably, at the center thereof. <P>SOLUTION: The electrophotographic type image forming apparatus includes: an endless belt-like image carrier 31, on which toner images of a plurality of colors are placed and which is turned; a turnable secondary transfer roller 36, which brings a body to be transferred P into close contact with the image carrier 31; and a turning opposing roller 32, which is arranged in the inner peripheral surface of the image carrier 31 and faces the second transfer roller 36. The electrophotographic image forming apparatus further includes: a plurality of high-frequency oscillating members 210 and 211, which are arranged in such a manner that the circle of the opposing roller 32 is divided; and a drive bias circuit 310, which is engaged with only a certain part of the high-frequency oscillation members 210 and 211, from the end of the opposing roller 32 and drives only a part of the high-frequency oscillating members 210 and 211, which are engaged with the inside of a nip area, formed by the image carrier 31 and the secondary transfer roller 36. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transfer technique (transfer control of charged powder) of an image forming apparatus using electrophotographic technology such as a color laser printer and a color MFP, and more particularly to an electrophotographic image forming apparatus to which this transfer technique is applied. is there.

In an electrophotographic color image forming apparatus that uses an intermediate transfer member, the qualitative change in the toner material causes an increase in the adhesion force to the intermediate transfer member and the cohesive force of the toner itself, and the transfer force of the transfer electric field is effective. May no longer work. In this case, an image defect may occur.
In this state, it is “worm-eating” that the toner cannot be transferred at a high pressure portion, and “bottom” is that the transfer itself is inhibited by the concave surface of the transferred material with poor smoothness. It is.
This is because when a CMYK divided color toner image is created, the toner image developed on the photosensitive member is transferred to the intermediate transfer member and held, and passes through the transfer portion of another color. This is because the image is easily pressed and aggregated.
As countermeasures, various techniques have been proposed to reduce the adhesion between the toner and between the toner and the image carrier by vibrating the toner image with a small amplitude before transfer (for example, Patent Documents). 1 to 4).
Patent Document 1 discloses a technique in which a roller that comes into contact with a belt from the inside is vibrated during cleaning, is removed by a foreign matter removing roller, and the entire roller is vibrated. Patent Document 2 discloses a technique in which a blade facing member is used as a vibration means in belt cleaning. Further, Patent Document 3 discloses a technique for applying ultrasonic waves to the back surface of the belt between the secondary transfer charger and the separation charger.

FIG. 14 is a schematic view showing a configuration in the conventional market in the transfer technology. This configuration is actually installed in an ultra-large machine called iGen3 developed by Xerox Corporation. In the drawing, an acoustic transfer auxiliary member 37 is disposed on the inner side of the intermediate transfer belt 31 facing the transfer paper P to be conveyed, and a transfer auxiliary blade is disposed on the opposite surface side of the transfer paper P in the vicinity of the copying auxiliary member 37. 38 is arranged.
The technique related to FIG. 14 is described in Patent Document 4. In this technique, a back surface vibration of 60 kHz is applied to the back surface of the belt between the secondary transfer charger and the separation charger. Here, the vibration area is in a state where vibration is performed before separation before the transfer area.
In the secondary transfer part of the iGen-3 machine, the transfer electric field is given by corotron. It is known that this machine separates after vibration and the transfer margin for non-smooth paper is very wide.
In addition, a separation charger is arranged downstream of the transfer charger. After being subjected to vibration, the close contact action itself does not occur when the close contact is incomplete. Therefore, it is considered that dust is likely to be generated on this machine (the actual image sample has a lot of dust).
In addition, there is a machine that improves the cleaning performance by blade vibration using a small particle toner cleaning device using a conductive blade, although it is not transfer.

FIG. 15 is a schematic view showing a secondary transfer portion of the prior art. In FIG. 15, the transfer sheet P, which is a transfer target, is guided onto the intermediate transfer member 31 supported by the support rollers 32 and 33, which is guided by the entrance guides 70 and 71 at the entry position and on which the toner image T is placed. .
The opposing roller 32 of the secondary transfer roller, which is a support roller, forms a nip with the secondary transfer roller 36.
The bias power supply 81 gives a negative bias (−) to the counter roller 32, and reference numeral 82 denotes a static elimination bias power supply that applies a static elimination bias to the static elimination electrode. In this conventional example, only an electric field is applied.
JP 2007-47587 A JP 2007-248631 A Japanese Patent Laid-Open No. 08-123217 US Pat. No. 5,081,500

However, in Patent Documents 1 and 2, fine adjustment is not possible depending on the position at which the transfer bias is applied to the belt that is the counterpart of the vibrating roller.
Further, in Patent Document 3, the vibration unit is located between the separation charger and the transfer charger, and is in a state of performing vibration before separation. The transfer area is upstream of the excitation part width. In the secondary transfer portion, the bias application space is a corotron, and the vibration means is provided with a horn connected to the vibrator slightly downstream from the center of the transfer.
In addition, a separation charger is arranged downstream of the transfer charger. After receiving the vibration, the close contact action itself does not occur when the close contact is incomplete. Therefore, it is considered that dust is easily generated in this machine.
The technology that reduces the adhesion between the toner and between the toner and the image carrier by vibrating the toner image with a very small amplitude before transfer works even for toner with low adhesion. May worsen the scattering (= Chile) around. It is good to adjust the excitation force, but it is difficult to deal with each condition uniformly. Further, when the vibration position is far from the secondary transfer, the amount of dust increases. For example, unfortunately, the iGen-3 machine is not good. In order to prevent this, for example, a constant speed difference is applied between the transfer object and the image carrier, so that image agglomeration is broken in the process of causing the lateral displacement force, or the normal adhesion state is cut off by a shearing force. This is an easy method. However, since this method mediates the transferred object, it cannot be used depending on the thickness and hardness of the transferred object. In general, it is best to apply vibration.

According to the examination of how to apply the minute vibration by the present inventor, it has been found that it is optimal to vibrate a part of the region where the secondary transfer roller and the intermediate transfer member are in contact with each other. Specifically, when the transfer paper starts to be sandwiched between the secondary transfer roller and the opposing roller, no vibration is applied.
Thereafter, a minute vibration is applied, and the toner whose adhesion is lowered moves the shortest distance. Thereafter, when the vibration is removed, the contact state is restored again, and the transferred toner is pressed onto the transfer paper P. Thus, it has been found desirable to apply the vibration force only during a part of the close contact period.
However, such close contact and vibration methods are difficult to realize. For example, a commercially available Langevin type vibrator is almost the same size as a member such as a counter roller, and it is difficult to make it close to the nip. Further, even if an attempt is made to bring the member closer to the transfer nip by adding a member to the vibrator, vibration propagation is likely to be irregular, and it is difficult to impart vibrations of equal amplitude.
Accordingly, an object of the present invention is to apply the adhesive force by pressure in the secondary transfer nip in consideration of the above-described situation, and to apply the adhesive force by vibration at a part of this secondary transfer nip, preferably at the center. It is an object of the present invention to provide an image forming apparatus that eliminates insect erosion, blurring, and transfer dust simultaneously by performing reduction.

In order to solve the above-described problems, the invention described in claim 1 is directed to an endless belt-like image carrier that rotates by placing toner images of a plurality of colors, and a circuit that closely contacts a transfer target to the image carrier. In the electrophotographic image forming apparatus, comprising: a secondary transfer roller that moves; and a counter roller that rotates opposite to the secondary transfer roller and is disposed on an inner peripheral surface of the image carrier. A plurality of high-frequency vibration members arranged by dividing the circumference of the roller, and a drive bias circuit that engages with only a part of the high-frequency vibration member from an end of the opposing roller, and the image An electrophotographic image forming apparatus that drives only a part of the high-frequency vibration member engaged in a nip region formed by the carrier and the secondary transfer roller is characterized.
According to a second aspect of the present invention, there is provided a rotation angle detection sensor for detecting a rotation angle opposite to the opposite roller, an input circuit, rigidity information of the transferred material input and stored in advance, and the opposite roller. 2. The electrophotographic system according to claim 1, further comprising: an arithmetic circuit that calculates rotation angle information; and a control circuit that controls to drive only a part of the vibrator based on a calculation result by the arithmetic circuit. The image forming apparatus is characterized.
According to a third aspect of the present invention, the two output terminals of the vibrator driving power source are connected via a coupling capacitor, and the outputs from the transfer bias and transfer roller cleaning transfer power sources The electrophotographic image forming apparatus according to claim 1, further comprising a filter that is connected via a container and bypasses the same frequency as the output frequency of the vibrator power supply.

According to the present invention, as shown in FIG. 13, the transfer paper can be transferred with a high quality image with good worm-eating, blurring and dust. By giving a small amplitude vibration in the nip, it is possible to improve the blur and insect bite.
This effect is an effect of vibration, and for reducing dust, the pressure on the image carrier and the pressure on the transfer paper are effective. As a result, a high-quality image can be obtained on the transfer paper. Can be transferred. In this case, a minute vibrating body is disposed on the entire circumference of the opposed roller. Further, only a part of the minute vibrating body is vibrated.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a schematic configuration of a full-color image forming apparatus according to an embodiment of the present invention. The full-color image forming apparatus according to the present embodiment is an image forming station to which image forming apparatuses 10Y (yellow), 10C (cyan), 10M (magenta), and 10K (black) for four colors, which are image carrier units, correspond. And an optical unit 20, an intermediate transfer body unit 30, a paper feed unit 40, a fixing unit 50, and the like as exposure means capable of irradiating laser light.
Each of the image forming apparatuses 10Y, 10C, 10M, and 10K has the same structure, and the photosensitive drums 12Y, 12C, 12M, and 12K as image carriers, and the photosensitive drums 12Y, 12C, and 12C as process means that operate on the photosensitive drums. Charging devices 13Y, 13C, 13M, 13K for charging 12M, 12K, and cleaning devices 14Y, 14C, 14M, 14K for removing developer remaining on the photosensitive drums 1212Y, 12C, 12M, 12KY, 12C, 12M, 12K Are integrally configured.
Further, the developing devices 15Y, 15C, 15M, and 15K for developing the latent images formed on the photosensitive drums 12Y, 12C, 12M, and 12K are connected to this. Further, each of the image forming apparatuses 10Y, 10C, 10M, and 10K is configured to be detachable from the image forming apparatus main body in the opening / closing direction of the openable / closable face plate (to be described later).

The intermediate transfer unit 30 includes a transfer belt 31 as a transfer medium (intermediate transfer member), three rollers 32, 33, and 34 that rotatably support the transfer belt 31, and photosensitive drums 12Y, 12C, 12M, and 12K. The primary transfer rollers 35Y, 35C, 35M, and 35K that transfer the toner image formed on the transfer belt 31 and the toner image transferred onto the transfer belt 31 are further transferred onto a transfer sheet P that is a recording transfer target. A secondary transfer roller 36 is provided.
The paper feed knit 40 includes a paper feed roller 43, a registration roller 44, and the like that transfer the transfer paper P, which is a recording medium, from the paper feed cassette 41 to the secondary transfer region. The fixing unit 50 includes a fixing roller 51 and a pressure roller 52, and performs fixing by applying heat and pressure to the toner image on the transfer paper P.
In the above configuration, first, in the first color yellow image forming device 10Y, the photosensitive drum 12Y is uniformly charged by the charging device 13Y, and then the latent image is developed by the developing device 1Y5 by the laser light emitted from the optical unit 20. Development is performed to form a toner image.
The toner image formed on the photosensitive drum 12Y is transferred onto the transfer belt 31 by the action of the primary transfer roller 35Y. The photosensitive drum 12Y after the primary transfer is cleaned by the cleaning device 14Y to prepare for the next image formation.
The residual toner collected by the cleaning device 14Y is set in the take-out direction of the image forming device 10Y (the rotation axis direction of the photosensitive drum 12Y), but is stored in a waste toner collection bottle (not shown). It is detachable from the main body of the image forming apparatus so that it can be replaced when the waste toner collecting bottle is full.

In FIG. 1, reference numeral 9 denotes a toner bottle for replenishing toner. From the left in the figure, toners of yellow (Y), cyan (C), magenta (M), and black (Bk) are filled. Depending on the non-conveying path, the developing devices 15Y, 15C, 15M, and 15Bk of the respective colors are replenished in the longitudinal direction of the developing devices 15Y, 15C, 15M, and 15K by a predetermined replenishment amount.
A similar image forming process is performed in each of the image forming apparatuses 10C, 10M, and 10K for C, M, and K to form toner images of each color, and sequentially superimpose and transfer the toner images to the previously formed toner images. .
On the other hand, the transfer paper P is conveyed to the secondary transfer area by the paper feed cassette 41, and the toner image formed on the transfer belt 31 is transferred to the transfer paper P by the action of the secondary transfer roller 36. The transfer sheet P onto which the toner image has been transferred is conveyed to the fixing unit 50, where the toner image is fixed at the nip portion between the fixing roller 51 and the pressure roller 52 of the fixing unit 50, and is discharged onto the discharge tray 56 by the discharge roller 55. To be discharged.

FIG. 2 is a schematic view showing a secondary transfer portion constituting the present invention. Next, the secondary transfer unit 100 constituting the present invention will be described with reference to FIG. The secondary transfer roller 36 is a medium resistance roller.
The medium resistance region is a volume resistivity of 10 ⁵ to 10 ⁷ Ω · m when the secondary transfer roller 36 is pressed against a metal plate by 1 kg on one side and a bias of 1 kV is applied between the axis and the metal plate. This indicates that it is 10 ⁵ to 10 ⁶ Ω · m if desired.
As the material of the secondary transfer roller 36, the shaft 36a is made of ordinary free-cutting steel or stainless steel, and the rubber portion 36b is mainly made of urethane, EPDM, or the like by applying a conductive agent, carbon black, or the like for bias application. Is adjusted. The surface hardness is adjusted to 15 to 70 degrees asuka C15.
Furthermore, there is an example in which the surface layer is coated with a resin such as Teflon (registered trademark). The shaft 36a is made by turning or extruding free-cutting steel in the same manner as an ordinary roller shaft. This may be cut out from the material or encapsulated in a metal tube.
The bias power supply 81 applies a repulsive bias of (−) to the counter roller 32, and is adjusted so that several kV is obtained at (−) several 10 μA. Although not related to the present invention, the static elimination electrode is designed to neutralize and separate the surplus charges on the back surface of the transferred body by the static elimination bias power source 82.
The intermediate transfer member 31 is a single layer belt or an elastic belt. This material and manufacturing method will be described later. Here, the opposing roller 32 is a special roller, and is designed so that only necessary portions can be selected and excited.
The transfer paper P, which is a transfer target, conveyed from the paper supply unit 40 in FIG. 1 is guided by the entrance guides 70 and 71 at the entry position and guided onto the intermediate transfer body 31 on which the toner image T is placed.

In this embodiment,
Transfer paper contact length: A = (contact start position when transfer paper enters) − (transfer paper separation occurrence position)
Nip width: B = (Entry discharge start position in transfer nip) − (Discharge stop position)
* This contact width is the width of transfer electric field formation.
Vibration application length: C = (position where vibration is started) − (position where vibration is stopped)
It becomes.
Here, a method for defining the contact length A will be described. The entry position of the transfer paper slightly changes depending on the rigidity of the transfer paper, the rigidity of the entrance guide, the direction of the transfer paper guide, and the like. The separation position varies depending on the magnitude of the transfer current and the presence / absence of static elimination only at the entry position.
Therefore, it is limited to a certain paper (for example, Type 6200 A4T made by Ricoh), and a halftone is passed. In the middle of this, the machine is stopped, and the transfer paper and the untransferred portion of the image carrier are pulled out, and the transfer roller is newly brought into contact to apply a transfer bias. As a result, the halftone image is transferred onto the transfer paper, and this dimension is measured with a ruler.
Next, a detailed method for defining the nip width B will be described. First, a uniform halftone image of a uniform color toner such as magenta or cyan is formed on the image carrier, and the machine is stopped before transferring to a transfer sheet. Thereafter, only the contact / separation circuit of the transfer roller is operated to bring the transfer roller into contact with a predetermined pressure.
At this time, the transfer roller is slightly rotated. In the image forming apparatus according to the embodiment, since the transfer roller falls on the non-stretching portion of the transfer belt, the image carrier is wound around the transfer roller. Here, when the transfer bias is applied for a short time, the halftone is transferred to the transfer roller. This dimension is measured and defined as the mechanical nip width. Subsequently, the vibration application length C is defined. This corresponds to the division width of the vibrator.

FIG. 3 is a partial cross-sectional view showing the intermediate transfer member according to the embodiment of the present invention. As shown in FIG. 3, the intermediate transfer member 31 is divided into a base layer 91, an elastic layer 92, and a surface layer 93, and is made to be an endless belt. Here, the base layer 91 is configured to have a thickness of 40 to 120 μm, the elastic layer 92 has a thickness of 120 to 220 μm, and the surface layer 93 has a thickness of 0.1 to 3 μm.
The raw materials or materials for the base layer, the elastic layer, and the surface layer constituting the intermediate transfer member are described in detail in JP-A-2007-108794 and the like, so the details are omitted here. However, simply speaking, there are various materials such as PI (polyimide resin), PVdF (polyvinylidene fluoride), PC (polycarbonate resin), ETFE, PPS, PSU, etc. . Here, in order to reduce the deformation of the circumference as much as possible when the intermediate transfer member 31 is suspended, a PI (polyimide) resin having a high elastic modulus is used.
The polyamic acid is heated to 200 ° C. or higher, or a dehydration / cyclization (imidization) reaction proceeds using a catalyst to obtain a polyimide. When a catalyst is used, an amine compound is often used, and a carboxylic acid anhydride may be used in combination as a dehydrating agent for quickly removing water generated by imidization.

Many of polyimides having a structure used industrially are dissolved in an organic solvent in the case of a polyamic acid structure, and are not dissolved in a polyimide. Therefore, when it is used for molding or coating, it is used in a polyamic acid solution, and the solution is dried to obtain a desired film, molded product or coating film, and then imidized to obtain a polyimide.
When used as a film, it is almost always used as an insulating base material for electronic circuit materials. It is manufactured by extruding a polyamic acid solution onto a metal belt and a drum, drying it, and finally imidizing at a temperature of 300 to 500 ° C. or higher.
Imidization may be performed thermally or an imidizing agent may be used. However, in order to improve the physical properties of the film even when imidization is completed at a low temperature using an imidizing agent, a final 300 is necessary. It is necessary to heat-treat at a high temperature of −500 ° C. or higher.
Raw materials or materials used for the elastic layer 92 are polyolefins such as polyethylene and polypropylene, vinyl polymers such as polystyrene, polyacrylic acid ester and polyvinyl acetate, condensation polymers such as polyester, phenol resin, polyurethane and polyimide, Furthermore, it is a natural polymer (rubber). In the present invention, chloroprene rubber or urethane rubber is used.

The organic polymer porous body is produced by a combination of various polymer raw materials and a pore forming technique, and exhibits a characteristic function depending on the pore diameter, porosity, strength, hardness, surface property, shape and the like. Examples of the production method include a phase separation method, an extraction method, a chemical treatment method, a stretching method, an irradiation etching method, a fusion method, a foaming method, a surface treatment, and a composite method. Examples of the foaming method include a mechanical foaming method, a physical foaming method, a chemical foaming method, and a heating foaming method.
There are various types of raw materials or materials used for the surface layer 93, such as silicon, fluorine, urethane, and PMMA. In the present invention, a silicon system is used. As for the material of the surface layer 93, in the present invention, it is necessary to cause deformation on the surface due to the movement of the solid body of the elastic layer, so that a thick and hard material cannot be used.
Here, it is 5 μm or less, and preferably 1.5 μm or less. Separately, the surface of the porous porous body may be treated by grafting, plasma treatment, etc., and then the surface layer may be applied.
As described above, since the intermediate transfer member 31 includes a solid material in a porous cavity, characteristics such as mechanical strain and rigidity change. On the other hand, the porosity affects the bulk density, pore volume, and the like. For this reason, after manufacture, a creep test or a stress relaxation test that shows the rigidity under pressure and viscoelastic behavior is performed to obtain a manufacturing index.
Further, resistance is also important for use in electrophotographic apparatus, and the volume resistivity ρv is from 10 ⁷ to 10 ¹¹ Ω · cm, and preferably from 10 ⁸ to 10 ¹⁰ Ω · cm. With particles. Here, it is molded so that the surface hardness is 60 degrees or less as desired in the micro hardness form.

FIG. 4 is a partial schematic perspective view for explaining the novel counter roller of the present invention. FIG. 5 is a cross-sectional view taken along line 5-5 ′ of FIG. The counter roller 32 of FIG. 2 will be described as a new counter roller 200 of the present invention with reference to FIGS. First, when showing the end portion of the facing roller 200, the base material 201 of the roller is made of a pipe material. There is a cheap method, but cutting is better because of high processing accuracy.
This surface is provided with an adhesive layer and is covered with an insulating material 202. The thickness of the coating layer which is the insulating material 202 is formed to 5 to 100 μm. Subsequently, a piezoelectric laminated ceramic 210 is bonded to the surface of the roller portion 201 on the coating layer 202 made of an insulating material. The ceramic 210 is 1 mm to 2 mm in the circumferential direction, and the thickness direction is the same displacement direction in the axial direction at this time. Here, an example of small piece ceramics is shown in 210, and a long strip-shaped ceramic is shown in 211.
Subsequently, as will be described later with reference to FIG. 6, the piezoelectric laminated ceramics 210 and 211 are combined so that the vibration directions thereof are different from each other. Of course, there is also a method in which a piezoelectric film instead of piezoelectric ceramic is attached in a long length. These are determined by cost.
The ceramic layer is coated with an insulating resin and a medium resistance tree. Note that the measurement conditions and specified range of the medium resistance layer are the same as those of the secondary transfer roller 36 (FIG. 2).

The end surface 203 of the roller part 201 is connected to each piezoelectric laminated ceramic 210. These are similarly connected in the axial direction. These are printed in advance on the insulating material 202 with conductive ink or the like. A film is formed so as to be insulated between the connections. It is necessary to coat the terminal surface with a material having a certain degree of insulation.
The conductive portion 240 extends the connection to the outside. Here, wear becomes a problem, but it is better to make the terminal slightly softer. The conductive portion 240 may be composed of a carbon electrode and a leaf spring made of phosphor bronze coated on the tip.
The spring constant is adjusted so that the contact pressure is the best to make the contact pressure about several tens of gf. Even if it is too light, contact will become unstable, and if it is heavy, the life will be reduced this time, so choose it to be in the middle.
As described above, according to the present invention, an electrophotographic image forming apparatus includes an intermediate transfer member 31 that is an endless belt-like image carrier that rotates by placing toner images of a plurality of colors, and a transfer target. A rotating secondary transfer roller 36 for bringing a transfer sheet P into close contact with the intermediate transfer member 31, and a rotating counter roller disposed on the inner peripheral surface of the intermediate transfer member 31 so as to face the secondary transfer roller 36. 32.
Also, a plurality of high-frequency vibration members 210 or 211 (FIG. 4) arranged by dividing the circumference of the opposing roller 32, and only a part of the high-frequency vibration members 210 or 211 from the end of the counter roller 32 Only a part of the high-frequency vibration member 210 or 211 that engages in a nip region formed by the intermediate transfer member 31 and the secondary transfer roller 36. Is configured to be driven.
As described above, the present invention applies vibration in the transfer nip to the transfer system to the transfer paper P (FIG. 2) using the secondary transfer roller 36. Specifically, the configuration of the opposing roller 32 is devised. A method is proposed in which the counter roller 32 is caused to vibrate with a minute amplitude in the radial direction (perpendicular to the axis).

FIG. 6 is a schematic cross-sectional view illustrating connection of a plurality of piezoelectric element cross sections near the roller surface layer. Next, in FIG. 6, it will be seen how a plurality of piezoelectric element cross sections are connected near the roller surface layer.
Piezoelectric laminated ceramic is a laminated material having a height of 3 mm, with a minimum of 30 layers and a gap between layers of 100 μm or less. Since the displacement is originally only about 5 μm, 30 layers can vibrate about several 150 μm. Of course, the required displacement value is adjusted by the movement of the toner. In terms of cost, fewer layers are better.
Here, since the electrodes are shared with the adjacent ceramics, the electrodes overlap in opposite directions. As a result, the direction of displacement is opposite to that of the adjacent ceramic. Of course, if each power supply is controlled individually, finer control can be achieved.

FIG. 7 is a schematic view showing a layer structure model of piezoelectric ceramics. The laminated type of piezoelectric ceramics is obtained by laminating several tens to several hundreds of piezoelectric ceramic thin plates, and each one is laminated and fixed alternately so that the polarization in the thickness direction is reversed.
As an example, in a commercial product, a 110 μm thin layer is sandwiched between electrodes, and 200 to 300 layers are laminated. The lead-out of the electrodes connects the polarizations + and-in parallel.
As a result, the direction of polarization of all piezoelectric ceramics becomes the same as the direction of the applied voltage, and is displaced in the stacking direction by the piezoelectric longitudinal effect. By reducing the thickness of one sheet, the voltage can be lowered, and by stacking, the total displacement can be obtained. This method is used in a field where characteristics such as a large generated force and a high response speed are utilized although the absolute value of the displacement amount is small.
Here, the ceramic layer is described, but in principle there are piezoelectric materials and performance, but there are materials that are easy to make. For example, it may be made of polyvinylidene fluoride (PVdF). Can be determined by cost.

FIG. 8 is a schematic view showing the manufacturing process of the piezoelectric ceramic. FIG. 8 simply shows the manufacturing process of the piezoelectric ceramics cited from the explanation on the company homepage for reference, and no particular explanation is added.
In the production of piezoelectric ceramics, a sheet forming method is suitable for the present invention. In the last step, an electrode is added, but this needs to be made thin. Expensive materials use rare earths such as palladium, but technologies using silver and the like have also been developed. The PVdF manufacturing process can be referred to materials such as the Society of Polymer Science.
FIG. 9 is a schematic diagram for explaining the actual operation of the electrode. FIG. 9 shows an example in which the electrode added in the last step of manufacturing the piezoelectric ceramic is actually operated. In the figure, the intermediate transfer member 31, the opposing roller 32, and the transfer paper P are shown.
Here, basically, a large number of power supplies 220 are prepared, and the displacement direction is changed for each electrode pitch. Here, the power source 220 is a DC power source, but its specification is a constant voltage of 0 to 500V. Here, the load is several thousand pF to several 10000 pF.
Therefore, it is necessary to select a power source that has a current limiter and the like and that does not cause an abnormality from a pseudo short circuit of the voltage within an appropriate output current range. The voltage varies depending on the thinness or withstand voltage of each layer in the ceramic laminated state and the output resistance of the power supply itself.

FIG. 10 is a schematic circuit diagram for explaining the operation of the ceramic incorporated in the counter roller of the image forming apparatus. In FIG. 10, the constant voltage power supply 301 is for transfer bias and the constant voltage power supply 302 is for cleaning the transfer roller, and the output can be switched by a switch 303. The output is output to the terminal row 203 via the buffer resistor 304 (10 MΩ).
Here, the PWM type high current output low voltage power supply 310 for driving the piezoelectric element outputs a pulse wave of 1 to 10 kHz at about several tens to several hundreds volts. The DC component is cut by the high-voltage condenser 311 (about 1 μF), the load fluctuation is reduced by the stabilizing resistor 312 (several tens to several hundreds kΩ), and the same is output to the terminal array 203.
What is important here is a notch filter 313 that grounds and eliminates noise from the drive power supply. As a result, the fluctuation of the transfer voltage is suppressed within 100 V here. Transfer performance hardly changes. In the figure, the broken line indicates the direction of current.
In the image forming apparatus according to the present invention, both output terminals of the vibrator driving power supply 310 are connected via a coupling capacitor 311 and a transfer power supply (FIGS. 10, 301 and 302, 301 is a transfer bias, 302 Output for cleaning the transfer roller) is connected via a resistor 304, and a filter 313 having the same frequency as the output frequency of the vibrator power supply 310 is grounded.

The transfer bias power supply output of the image forming apparatus described above is a high voltage (0.8 to 7 kVDC) and a minimum current (10 to 30 μA). On the other hand, the vibration drive power output is AC (frequency 10 to 100 kHz), large current (several tens to several thousand mA), and low voltage (10 to 200 VAC). Further, a recent transfer system is a repulsive transfer (= a system in which a (−) high voltage is applied to the opposite roller).
Accordingly, two power outputs must be applied to the opposing roller 32 at the same time. That is, considering that the conductive layer is provided on the surface layer of the transfer roller on the smaller side, the number of vibration inclusions increases, and the propagation efficiency decreases.
Therefore, it is necessary to mix two types of power outputs, DC and AC. However, depending on the specifications of the element, the AC component is a high current-low voltage, but the transfer bias is a low current-high voltage DC component. These biases are configured to prevent mutual interference.
Here, an example in which a frequency-fixed piezoelectric element is used as the vibrator will be described. Since it has the indicated circuit, the drive power supply and the transfer power supply are different between AC and DC. As a result, transfer bias and vibration can be applied simultaneously.
Accordingly, it is possible to realize labor saving such as downsizing in the vicinity of the secondary transfer portion and drawing of the bias. In addition, since the application timing of the excitation bias is almost the same as the application timing of the transfer bias, the circuit can be easily omitted.

FIG. 11 is a schematic diagram exaggerating the locus and nip width of a transfer sheet that varies depending on the thickness of the transfer sheet. 11 has the same configuration as that of FIG. 2 except for the exaggerated transfer paper trajectory and nip width. Therefore, the same parts as those in FIG. Omitted.
In FIG. 11, here, it is shown that the transfer paper P, which is a transfer target, has a different locus and nip width between the transfer paper P having a thick transfer paper and the normal transfer paper. In the case of thick transfer paper, the start point and end point of the transfer nip are greatly shifted.
This is remarkable when the secondary transfer roller 36 is a foaming roller and no pressure is applied, and when the entrance guide 70 has low rigidity. Therefore, in such a transfer sheet, the vibration start point and vibration end point must be shifted slightly.
FIG. 12 is a schematic diagram showing a circuit configuration for detecting the rotation angle of the opposing roller in real time by a reflection sensor. In FIG. 12, the rotation angle of the opposing roller 32 is detected in real time by the reflection sensor 400, and a detection signal is input to the input circuit 401 via the buffer 401a.
The arithmetic circuit 403 determines the shift amount of the vibration area based on the rigidity data of the transfer paper that has been put in advance. Subsequently, the terminal of the excitation unit is shifted from the output device 402. In this case, the distribution is performed using an electrical switch, but it is needless to say that the distribution may be performed using a mechanical switch.
In addition to the output circuit 402, the LED current control to the reflection sensor 400, the basic output of the vibrator drive power supply (used by amplification with a high-voltage / high-current amplifier in the figure), the transfer bias to the opposing roller 32, and The cleaning bias can be switched, and the configuration is most versatile.

As described above, in the image forming apparatus of the present invention, the sensor 400 that detects the rotation angle facing the counter roller 32, the input circuit 401 that inputs the detection signal from the sensor 400, and the transfer paper P that is input and stored in advance. An arithmetic circuit 403 that calculates the rigidity information of the opposite roller and the counter roller rotation angle information, and a control circuit (output circuit) 402 that controls to drive only a part of the vibrator based on the calculation result. Provided.
When the vibrator drive is switched mechanically, the nip formation state changes depending on the type of transfer paper. For example, when the transfer paper has high rigidity, the nip region and the nip width generally change. Naturally, the start timing and end timing of vibration are also different. Therefore, this configuration is useful because it is possible to finely control the excitation range when it is necessary to finely adjust the vibration application position and it is necessary to perform switching in software.
As described above, the type of transfer paper and the rigidity of the transfer medium are manually input (automatic detection is desirable, but not limited in the present invention) to estimate the contact state of the transfer paper, and the sensor 400 or the like is used to detect the opposing roller 32. By providing the control circuit 402 that detects the current rotation angle and changes the vibrator drive timing based on the calculation information, it is possible to output high-quality image regardless of the type of transfer paper.

FIG. 13 is a table showing the evaluation results when the embodiment of the present invention is mounted on an image forming apparatus. In FIG. 13, this is an example of determining an image. Here, the conventional machine is shown under conditions (no vibration).
When it is judged by dust and (worm eater / bottle), there are many places depending on the properties of the original toner without vibration. For this reason, dust that adheres easily is ○, but insect bite / bottle is X. When vibration is applied away from the transfer nip, dust becomes x, but both bug eaters and bossiness are improved.
However, it cannot be said that this has improved from the trade-off state. Subsequently, in the method of applying vibration in the transfer nip, dust is improved to ○ to Δ, but it is still insufficient. Finally, as in the present invention, when the vibration application range in the transfer nip is narrowed, no dust is generated. In addition, insect eaters and botsocks are also complete.

1 is a schematic diagram illustrating a schematic configuration of a full-color image forming apparatus according to an embodiment of the present invention. It is the schematic which shows the secondary transfer part which comprises this invention. FIG. 3 is a partial cross-sectional view illustrating an intermediate transfer member according to an embodiment of the present invention. It is a partial schematic perspective view explaining the novel opposing roller of this invention. FIG. 5 is a cross-sectional view taken along line 5-5 'of FIG. It is a schematic sectional drawing explaining the connection of the some piezoelectric element cross section near roller surface layer. It is the schematic which shows the layer structure model of piezoelectric ceramics. It is the schematic which shows the manufacturing process of piezoelectric ceramics. It is the schematic explaining the actual operation | movement of an electrode. It is a schematic circuit diagram explaining the operation of the ceramics incorporated in the opposing roller of the image forming apparatus. It is the schematic which exaggerates and shows the locus | trajectory and nip width | variety of a transfer paper which change with thickness of a transfer paper. It is the schematic which shows the circuit structure which detects the rotation angle of a counter roller in real time with a reflection sensor. It is a figure which shows the evaluation result at the time of mounting embodiment of this invention in an image forming apparatus as a table | surface. It is the schematic which shows the structure in a conventional market in a transfer technique. It is the schematic which shows the secondary transfer part of a prior art.

Explanation of symbols

A Image forming device P Transfer paper (transfer object)
31 Endless belt-shaped image carrier (intermediate transfer member)
32 Counter roller 36 Secondary transfer roller 210 High-frequency vibration member 211 High-frequency vibration member 301 Power supply for transfer (for transfer bias)
302 Power supply for transfer (for cleaning transfer roller)
304 Resistor 310 Drive bias circuit (vibrator power supply)
311 Drive bias circuit (coupling capacitor)
312 Driving bias circuit (stabilizing resistor)
313 Filter 400 Rotation angle detection sensor (reflection sensor)
401 input circuit 402 control circuit 403 arithmetic circuit

Claims (3)

An endless belt-shaped image bearing member that rotates by placing toner images of a plurality of colors, a rotating secondary transfer roller that closely contacts a transfer target to the image bearing member, and the secondary transfer roller, In an electrophotographic image forming apparatus having a counter roller that rotates and disposed on an inner peripheral surface of the image carrier,
A plurality of high-frequency vibration members arranged by dividing the circumference of the counter roller, and a drive bias circuit that engages with only a part of the high-frequency vibration member from an end of the counter roller, An electrophotographic image forming apparatus, wherein only a part of a high-frequency vibration member engaged in a nip region formed by the image carrier and the secondary transfer roller is driven.   A rotation angle detection sensor that detects a rotation angle that faces the counter roller, an input circuit, a calculation circuit that calculates rigidity information of the transferred object that has been input and stored in advance, and rotation angle information of the counter roller; 2. The electrophotographic image forming apparatus according to claim 1, further comprising: a control circuit that controls to drive only a part of the vibrator based on a calculation result of the calculation circuit.   Two output terminals of the vibrator driving power source are connected via a coupling capacitor, and outputs from the transfer bias and transfer roller cleaning transfer power sources are connected via a resistor, and the vibrator 2. The electrophotographic image forming apparatus according to claim 1, further comprising a filter that bypasses the same frequency as the output frequency of the power source.

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