JP2011048132A - Image transfer method, image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image transfer system using ultrasonic vibration generating means, the image transfer system maintaining the durability of the ultrasonic vibration generation means, even with a lapse of time, and prolong the life of components, thereby maintaining optimum image quality. <P>SOLUTION: In the image transfer method of transferring a toner image carried on an image carrier 2 to a recording medium P at a transfer part, there are provided: a surface roughness detecting means 18 for detecting the surface roughness of the recording medium P; and the plurality of ultrasonic vibration generation means (first ultrasonic vibration generation means (16a, 17a) and second ultrasonic vibration generating means (16b, 17b)) disposed at the inside of the image carrier 2 in the transfer part. The driving or attaching/detaching operation of each of the plurality of ultrasonic vibration generating means is switched in accordance with the detection value detected by the surface roughness detecting means 18 to transfer the toner image. Consequently, the working time of each of the ultrasonic vibration generation means is shortened, and also, the durability of the ultrasonic vibration generation means can be maintained even with the lapse of time. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image transfer technique used in an image forming apparatus, and more particularly, to an image transfer method characterized by assisting toner transfer in a transfer unit that transfers a toner image from an image carrier to a recording medium, and the image transfer The present invention relates to an image forming method using the method and an image forming apparatus.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine of these, a toner image formed on a photosensitive member or an intermediate transfer member is transferred to a recording medium to form an image. If you are trying to transfer a solid image to embossed paper with large irregularities on the surface, more specifically leather paper with a leather-like pattern on the surface, especially toner in the groove Transfer defects may occur. Hereinafter, the transfer performance in such a case will be referred to as “uneven transfer capability”, and the insufficient transfer performance will be referred to as “uneven transfer failure”.

In an image forming apparatus using an intermediate transfer member, a toner image developed on a photosensitive member is first transferred onto the intermediate transfer member by the action of a transfer electric field (primary transfer process), and then by the action of a reverse transfer electric field. A method of transferring from an intermediate transfer member onto a recording medium such as paper (secondary transfer step) is generally known.
In the primary transfer process, each color toner is sequentially transferred from the photosensitive member to the intermediate transfer member at each color image forming station. In the case of a single color image, the transfer electric field acts only once, but in the case of a multicolor image, the toner at the most upstream image forming station is on the intermediate transfer member, and the downstream toner is the upstream toner. Will be transcribed on top. Furthermore, since the transfer electric field is applied to the toner at the most upstream image forming station every time it passes through the downstream image forming station, the non-electrostatic adhesion between the toner and the intermediate transfer member gradually increases. In addition, since the photosensitive member and the intermediate transfer member are in close contact with each other in the toner layer due to the transfer electric field, a stronger aggregating force acts between the toners than in the case of a single color image.

  In the secondary transfer process, the intermediate transfer member and a recording medium such as paper are generally sandwiched between a pair of roller members, and a transfer electric field from the intermediate transfer member to the recording medium is applied to the recording medium. The toner is transferred to At this time, if the recording medium is in close contact with the surface of the intermediate transfer member, the toner, and the paper surface, as in the case of paper with high smoothness, the toner transferability is maintained well. In the case of embossed paper having a gap, a gap is formed between the toner and the paper surface at the concave portion, so that the toner transferability tends to deteriorate. In the case of such an embossed paper, when a multicolor image is transferred, the toner in the downstream image forming station is transferred in the primary transfer process, but the toner in the upstream image forming station is transferred to the intermediate transfer member as described above. As a result, the toner transferability is deteriorated and the original color is not reproduced in the concave portion of the paper.

  This phenomenon is caused by the fact that additive fine particles adhering to the toner surface over time tend to be detached or buried from the toner surface due to friction between the toner and the carrier. Since the adhesion force and the toner cohesion force become stronger, the toner transferability tends to deteriorate.

  In order to solve the above problems, an image forming apparatus configured to use ultrasonic vibration for toner transfer (for example, Japanese Patent Laid-Open No. 52-126230) or a transfer to a secondary transfer unit. There has been proposed an image forming apparatus (for example, Japanese Patent Laid-Open No. 4-234077) having a structure in which a charger and an ultrasonic vibrator are provided to assist toner transfer.

In the configuration using ultrasonic vibration to assist toner transfer, ultrasonic vibration is applied to the paper transfer part for paper with uneven surface such as embossed paper, and transfer rate for paper with large surface unevenness. It is effective for improvement. However, for paper with a smooth surface, problems such as “transfer dust” occur when the vibration speed is excessive.
In addition, in a configuration in which ultrasonic vibration is applied to the paper transfer unit on a paper with an uneven surface such as embossed paper, if the drive voltage is increased too much to increase the vibration speed of the ultrasonic vibrator, the ultrasonic wave Due to the heat generation of the vibrator itself, the characteristics are deteriorated, and problems such as failure to maintain sufficient ultrasonic vibration occur.

  In the present invention, when an image is formed on the embossed paper as described above as a recording medium, both the embossed paper having various irregularities and various image patterns such as a multicolor image are further time-lapsed. In addition, an image transfer method, an image forming method, and an image forming apparatus capable of maintaining good image quality can be provided. To provide an image transfer method, an image forming method, and an image forming apparatus capable of maintaining the durability of an ultrasonic vibration generating unit and extending the life of components and thereby maintaining an optimum image quality. With the goal.

In order to achieve the above object, the present invention employs the following solutions.
According to a first aspect of the present invention, there is provided an image transfer method in which a toner image carried by an image carrier is transferred to a recording medium by a transfer unit, a surface roughness detecting means for detecting a surface roughness of the recording medium, A plurality of ultrasonic vibration generating means disposed inside the image carrier of the transfer unit, and switching the driving of the plurality of ultrasonic vibration generating means according to the detection value of the surface roughness detecting means, The toner image is transferred (claim 1).
According to a second solving means of the present invention, in the image transfer method of the first solving means, the plurality of ultrasonic vibration generating means are provided so as to be able to contact and separate from the image carrier, and the surface roughness detecting means. According to the detected value, the plurality of ultrasonic vibration generating means are brought into contact with or separated from the image carrier (claim 2).
According to a third solving means of the present invention, in the image transfer method of the first or second solving means, the ultrasonic vibration generating means includes an ultrasonic vibrator for generating ultrasonic vibration, and an inner side of the image carrier. And a horn that transmits vibrations from the ultrasonic transducer in contact with the ultrasonic transducer (claim 3).
According to a fourth solving means of the present invention, in the image transfer method according to any one of the first to third solving means, the plurality of ultrasonic vibration generating means have different frequency characteristics. (Claim 4).

  According to a fifth aspect of the present invention, there is provided an image forming method in which a toner image carried by an image carrier is transferred to a recording medium by a transfer unit, and an image is formed on the recording medium. The image transfer method of one solution is used (claim 5).

  In the above image transfer method or image forming method according to the present invention, the image carrier is a direct transfer that forms a toner image on a photoconductor and transfers the toner image carried on the photoconductor to a recording medium. In this method, it is a photoconductor. In the intermediate transfer method, the toner image formed on the photoconductor is primarily transferred to an intermediate transfer member, and then the toner image carried on the intermediate transfer member is secondarily transferred to a recording medium. is there.

According to a sixth aspect of the present invention, there is provided an image forming apparatus having a transfer unit that transfers a toner image carried by an image carrier to a recording medium, and a surface roughness detecting unit that detects the surface roughness of the recording medium; A plurality of ultrasonic vibration generating means arranged inside the image carrier of the transfer unit, and switching the driving of the plurality of ultrasonic vibration generating means according to the detection value of the surface roughness detecting means Thus, the toner image is transferred (claim 6).
According to a seventh solving means of the present invention, in the image forming apparatus according to the sixth solving means, the plurality of ultrasonic vibration generating means are provided so as to be able to come in contact with and separate from the image carrier. According to a detection value of the height detection means, a mode in which the plurality of ultrasonic vibration generating means are brought into contact with or separated from the image carrier is switched (claim 7).
According to an eighth solving means of the present invention, in the image forming apparatus according to the sixth or seventh solving means, the ultrasonic vibration generating means includes an ultrasonic vibrator for generating ultrasonic vibration, and an inner side of the image carrier. And a horn that transmits vibrations from the ultrasonic transducer in contact with the ultrasonic transducer (claim 8).
According to a ninth solving means of the present invention, in the image forming apparatus according to any one of the sixth to eighth solving means, the plurality of ultrasonic vibration generating means have different frequency characteristics. (Claim 9).

  According to a tenth solving means of the present invention, in the image forming apparatus according to any one of the sixth to ninth solving means, a photoconductor, an image forming means for forming a toner image on the photoconductor, and the photoconductor An endless belt-shaped intermediate transfer body to which a toner image is primarily transferred from the toner image, and a secondary transfer portion for transferring the toner image from the intermediate transfer body to a recording medium, and the image carrier is the intermediate transfer body, A plurality of ultrasonic vibration generating means are juxtaposed in the moving direction of the intermediate transfer body inside the intermediate transfer body of the secondary transfer portion (claim 10).

  According to an eleventh solution of the present invention, in the image forming apparatus according to any one of the sixth to ninth solutions, an endless belt-shaped photoconductor, and an image forming unit that forms a toner image on the photoconductor. A transfer portion for transferring a toner image from the photoconductor to a recording medium, the image carrier being the photoconductor, and a plurality of superconductors in a moving direction of the photoconductor inside the photoconductor of the transfer portion. Sound wave vibration generating means are provided in parallel (claim 11).

In the present invention, a plurality of ultrasonic vibration generating means (ultrasonic vibrator and horn) are arranged inside the image bearing member (photosensitive member or intermediate transfer member) of the transfer portion, and according to the detection value of the surface roughness detecting means. By switching the driving of a plurality of ultrasonic vibration generating means, or by switching the contact or separation of the plurality of ultrasonic vibration generating means with respect to the image carrier, one ultrasonic vibration generating means can be switched simultaneously with output switching. Since the operation time can be shortened, the durability of the ultrasonic vibration generating means can be maintained over time and the optimum image quality can be maintained.
In the present invention, since the plurality of ultrasonic generation means have different frequency characteristics, even when the plurality of ultrasonic vibration generation means are used in contact with the image carrier, a plurality of ultrasonic vibration generations are performed. Since the vibration characteristics of the means with respect to the recording medium are not canceled in the opposite phase, the optimum image quality can always be maintained over time.

1 is an overall schematic configuration diagram illustrating a configuration example of an image forming apparatus according to the present invention. 1 is a schematic configuration diagram of an essential part of an image forming apparatus in which ultrasonic vibration generating means is provided in a transfer unit according to the present invention. It is a schematic perspective view which shows an example of the ultrasonic transducer | vibrator and horn which are used with the image forming apparatus of this invention. It is a schematic perspective view which shows another example of the ultrasonic transducer | vibrator and horn which are used with the image forming apparatus of this invention. FIG. 2 is a diagram illustrating an embodiment of the present invention, and is a schematic configuration diagram of a main part of an image forming apparatus provided with a plurality of ultrasonic vibration generating units in a transfer unit. FIG. 10 is a diagram illustrating another embodiment of the present invention, and is a schematic configuration diagram of an essential part of an image forming apparatus in which a plurality of ultrasonic vibration generating units are provided in a transfer unit so as to be able to contact and separate. FIG. 7 is a schematic configuration diagram of an essential part showing an operation example of the image forming apparatus shown in FIG. 6.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the configuration and operation outline of a tandem type color copier as an example of an image forming apparatus according to the present invention will be described with reference to FIG.
In FIG. 1, a color copying machine 1 includes an image forming unit 1A located at the center of the apparatus main body, a paper feeding unit 1B located below the image forming unit 1A, and a document transport located above the image forming unit 1A. 1C and a scanner unit 1D.
The color copying machine 1 shown in FIG. 1 has a communication function, and is used as a printer, facsimile, scanner, etc. by connecting to a LAN (local area network) or a communication line (telephone line, optical line). It has a function as a multifunction machine.

  In FIG. 1, when a document is placed on the document table 1C1 of the document transport unit 1C and a start key on an operation panel (not shown) is pressed, the document is transported onto the contact glass 1D1 by the document transport unit 1C. The document image is read, converted into image information by an image processing unit (not shown), and sent to the image forming unit 1A.

  An intermediate transfer belt 2 as an intermediate transfer body having a transfer surface extending in the horizontal direction is disposed in the image forming unit 1A. The upper surface of the intermediate transfer belt 2 has a color complementary to the color separation color. A configuration for forming an image is provided. That is, the photoreceptors 3Y, 3M, and 3C as latent image carriers that can carry images of toners of complementary colors (for example, yellow (Y), magenta (M), cyan (C), and black (B)). 3B are juxtaposed along the transfer surface of the intermediate transfer belt 2.

  Each of the photoconductors 3Y, 3M, 3C, and 3B is composed of a drum that can rotate in the same direction (counterclockwise direction). Taking the yellow (Y) photoconductor 3Y as an example, A charging device 4Y that executes image forming processing in the rotation process, an exposure unit for the light beam 5Y from the writing device 5 as a light writing means, a developing device 6Y, a primary transfer device 7Y, and a cleaning device 8Y. Each color image forming station is configured. Although the reference numerals are omitted in FIG. 1, for example, as shown in FIG. 2, the configuration around the other photoconductors 3M, 3C, and 3B is the same (the alphabets attached to the respective reference numerals are photosensitive As with the body 3, it corresponds to the color of the toner).

  The image forming station for each color may use a process cartridge in which at least one of the photosensitive member 3, the charging device 4, the developing device 6, and the cleaning device 8 is integrally stored in the cartridge. Is detachable from the main body of the image forming apparatus, so that replacement and maintenance are facilitated.

  Each developing device 6 contains color toner of each color. The intermediate transfer belt 2 is configured to be able to move in the same direction at a position facing the photoreceptors 3Y, 3M, 3C, and 3B by being wound around the driving roller 2B, the driven roller 2A, and the transfer counter roller 2C. . A cleaning device 10 for cleaning the surface of the intermediate transfer belt 2 is provided at a position facing the driven roller 2A. A tension roller 14 is provided to adjust the tension of the intermediate transfer belt 2.

  Here, a yellow (Y) image forming station will be described as an example. The surface of the photoreceptor 3Y is uniformly charged by the charging device 4Y, and the surface of the photoreceptor 3Y is formed on the photoreceptor 3Y based on image information from the scanner unit 1D. An electrostatic latent image is formed. The electrostatic latent image is visualized as a toner image by a developing device 6Y containing yellow toner, and the toner image is primarily transferred onto the intermediate transfer belt 2 by a primary transfer device 7Y to which a predetermined bias is applied. The Similar image formation is performed on the photoreceptors 3M, 3C, and 3B of the other color image forming stations only by different toner colors, and the toner images of the respective colors are sequentially transferred and superimposed on the intermediate transfer belt 2. . After the transfer, the toner remaining on the photoreceptors 3Y, 3M, 3C, and 3B is removed by the cleaning devices 8Y, 8M, 8C, and 8B, and after the transfer, the photoreceptors 3Y, 3M, 3C, and The potential of 3B is initialized and prepared for the next imaging step.

  The paper feed unit 1B separates and feeds the multi-stage paper feed trays 1B1 on which the paper P as a recording medium is stacked and the paper P in the paper feed tray 1B1 one by one from the top. After the roller, the conveyance roller pair 1B2 that conveys the fed paper P, and the paper P is temporarily stopped and the oblique shift is corrected, the leading edge of the image on the intermediate transfer belt 21 and a predetermined position in the conveyance direction are The registration roller pair 1B3 is sent out toward the nip at the coincidence timing. Further, a manual paper feed tray 1A1 and a paper feed roller 1A2 are provided on the side surface of the image forming unit 1A. During manual paper feed, a recording medium (various types of paper, various papers) placed on the manual paper feed tray 1A1 is provided. OHP sheet or the like) is fed toward the registration roller pair 1B3 by the sheet feeding roller 1A2. A double-sided conveyance unit RP that reverses the paper P on which an image is formed on one side and re-feeds the paper toward the registration roller pair 1B3 is installed below the image forming unit 1A.

  A sensor (not shown) for detecting the reflectance of the recording medium surface is provided upstream (or downstream) of the registration roller pair 1B3. If the sensor output is different from the sensor output in the previous process, the intermediate transfer belt 2 or the transfer counter roller 2C Switch. In addition, in the configuration in which a plurality of ultrasonic vibration generating means for assisting toner transfer is provided in the secondary transfer unit as in the embodiments described later, the driving of the plurality of ultrasonic vibration generating means and the contact / separation according to the sensor output are performed. Switch operation.

  A toner image T (hereinafter also simply referred to as toner) that is primarily transferred from the photoreceptors 3Y, 3M, 3C, and 3B onto the intermediate transfer belt 2 is biased (direct current (DC) bias) by a secondary transfer bias applying unit (not shown). (Including those in which an alternating current (AC), a pulse or the like is superimposed thereon) is applied to the transfer counter roller 2C, and the sheet P is applied to the secondary transfer device 20 via the intermediate transfer belt 2 by the action of an electric field. Secondary transfer. Thereafter, the sheet P on which the toner image T is secondarily transferred on the surface is firmly fixed on the surface by the action of heat and pressure in the fixing device 11, and is discharged to the discharge tray 13 through the discharge roller 12. .

  In the present embodiment, the primary transfer unit includes a primary transfer bias roller as a primary transfer device 7 (color symbols are omitted (other members are the same)) from the back surface of the intermediate transfer belt 2 and a bearing and a compression spring (not shown). Thus, the photosensitive member 3 is pressed by a predetermined pressure through the intermediate transfer belt 2. The position of the primary transfer bias roller 7 that contacts the intermediate transfer belt 2 needs to be set to contact a position that is offset by 1 to 2 mm downstream from the center position of the photoreceptor 3. In order to prevent “pre-transfer”, the primary transfer bias roller 7 rotates with the intermediate transfer belt 2.

The primary transfer bias roller 7 used in the present embodiment is configured in such a manner that a rubber material having a medium resistance electric characteristic is wound around a metal core. As a specific configuration example, it is composed of a foam rubber having a medium resistance, and its volume resistivity is in the range of 10 ⁶ to 10 ¹⁰ Ω · cm, preferably 10 ⁷ to 10 ⁹ Ω · cm. The material is not limited to foam rubber, and medium resistance solid rubber can be used as well.

Further, a transfer counter roller (hereinafter also referred to as a repulsive roller) 2C used in the present embodiment is configured in a form in which a rubber material having an electric characteristic of medium resistance is wound around a metal core. As a specific configuration example, it is composed of a medium-resistance solid rubber, and its volume resistivity is in the range of 10 ⁶ to 10 ¹⁰ Ω · cm, preferably 10 ⁷ to 10 ⁹ Ω · cm.

When the secondary transfer device 20 used in the present embodiment is configured by, for example, a secondary transfer roller, the secondary transfer roller is configured by a medium-resistance foamed rubber, and its volume resistivity is 10 ⁶ to 10. ^{The range is 10} Ω · cm, preferably 10 ⁷ to 10 ⁹ Ω · cm. Further, as shown in the embodiments described later, when a plurality of ultrasonic vibration generating means are provided for toner transfer assistance, the secondary transfer device 20 uses a medium resistance belt stretched around a plurality of rollers. It is done.

In the primary transfer process, the primary transfer bias is applied to the primary transfer bias roller 7 using a constant current power source having a polarity of (+), and the current setting value is in the range of approximately 20 to 40 μA.
On the other hand, the secondary transfer bias is applied to the transfer counter roller (repulsive roller) 2C using a constant current power source having a polarity of (−), and the current setting value is in the range of about 20 to 50 μA. When the secondary transfer device 20 is a secondary transfer roller or a secondary transfer belt, the secondary transfer roller or the secondary transfer belt is electrically grounded (ground potential).

  More specifically, in the secondary transfer process of the present invention, a constant current power source to which a bias having the same polarity as that of the toner is applied to the transfer counter roller (repulsive roller) 2C. The set value is in the range of approximately 20-40 μA. Then, a secondary transfer electric field is applied in a direction in which the toner on the intermediate transfer belt 2 is pushed out to the recording medium (paper) side with the secondary transfer device (secondary transfer roller or secondary transfer belt) 20 connected to the ground facing. Applied.

As a specific example of the intermediate transfer belt 2 used in the present embodiment, PI (polyimide), PAI (polyamideimide), PC (polycarbonate), ETFE (ethylene-tetrafluoroethylene) are used as a single layer belt. ), PVDF (polyvinylidene fluoride), PPS (polyphenylene sulfide), etc., and carbon dispersion or medium resistance resin whose resistance is adjusted by blending an ionic conductive agent. The volume resistivity is in the range of 10 ⁶ to 10 ¹⁰ Ω · cm, preferably 10 ⁸ to 10 ¹⁰ Ω · cm. The surface resistivity is in the range of 10 ⁶ to 10 ¹² Ω / □, preferably 10 ⁸ to 10 ¹² Ω / □. Further, the thickness is in the range of 50 to 100 μm, and the Young's modulus (longitudinal elastic modulus) is preferably 3000 MPa or more, and sufficient mechanical strength is required to withstand the forces such as elongation, bending, wrinkling, and undulation generated by driving. .

  Other embodiments of the intermediate transfer belt 2 include PI (polyimide), PAI (polyamideimide), PC (polycarbonate), ETFE (ethylene-tetrafluoroethylene), PVDF (polyvinylidene fluoride), PPS (polyphenylene sulfide). A surface layer with a slightly higher resistance than the volume resistivity of the belt layer itself is provided only on the surface side of the belt with a single layer structure of medium resistance resin whose resistance is adjusted by carbon dispersion in the material such as An intermediate transfer belt having the above-described configuration may be used, and the surface layer thickness is preferably about 1 to 10 μm. When an intermediate transfer belt having such a high resistance surface layer is used, there is an effect of improving abnormal images such as “white spots”. Here, abnormal images such as “white spots” mean that the amount of moisture in the paper after passing through fixing once, particularly when an intermediate transfer belt of a type in which carbon is dispersed in a resin and resistance control is used. This phenomenon occurs in the secondary transfer process, etc., to the paper whose resistance has been increased and the resistance has been increased, and due to the dispersion of the carbon dispersion state, a transfer current can flow in a concentrated manner, and the toner in that portion is repelled. It is a phenomenon that goes white. Therefore, it is known that by providing a high resistance layer on the surface like the above intermediate transfer belt, the local concentration of the transfer current is alleviated, so that the abnormal image “white spot” can be improved.

Further embodiments of the intermediate transfer belt 2 include PI (polyimide), PAI (polyamideimide), PC (polycarbonate), ETFE (ethylene-tetrafluoroethylene), PVDF (polyvinylidene fluoride), PPS (polyphenylene). On the base layer 50-100 μm composed of carbon dispersion in a material such as sulfide) or medium resistance resin whose resistance is adjusted by blending an ionic conductive agent, on the rubber material such as urethane, NBR, CR, etc. An elastic layer made of a material whose resistance is adjusted by blending an ionic conductive agent is provided in an amount of 100 to 500 μm, and the surface layer is made of fluorine rubber or resin having a thickness of about 1 to 10 μm (or a hybrid material thereof). A three-layer belt with coating may be used. The same effect even when using sex intermediate transfer belt obtained. By using such an elastic intermediate transfer belt, the elastic layer follows the concave portion even in a transfer material such as a paper having a low density of paper fibers of the recording medium or a so-called embossed paper having an uneven surface of 20 to 30 μm on the surface. Therefore, a solid filling improvement effect that the toner transfer property to the concave portion is improved is known.
The intermediate transfer belt 2 in the present invention can be used by appropriately combining the above-described embodiments.

In the image forming apparatus 1 configured as described above, if the recording medium P is in close contact with the surface of the intermediate transfer belt 2 and the surface of the toner and the paper as in paper with high smoothness, the toner transferability is good. However, in the case of embossed paper having a large unevenness on the surface, a gap is formed between the toner and the paper surface at the recessed portion, so that the toner transferability tends to deteriorate. In the case of such an embossed paper, when a multicolor image is transferred, the toner of the downstream image forming station is transferred in the primary transfer process, but the toner of the upstream image forming station is transferred to the intermediate transfer belt as described above. As a result, the toner transferability is deteriorated and the original color cannot be reproduced in the concave portion of the paper.
Therefore, in the present invention, even when the recording medium P is a paper having an uneven surface such as embossed paper, the transfer rate is obtained by applying ultrasonic vibration to the paper by the ultrasonic vibration generating means at the transfer unit. We are trying to improve.

Hereinafter, specific examples of the configuration and operation of the transfer unit to the recording medium, which is a feature of the present invention, will be described in detail.
First, as a configuration example of the paper transfer unit according to the present invention, specific configurations and operations of the secondary transfer unit and the ultrasonic vibration generating means will be described with reference to FIGS.
FIG. 2 is a schematic configuration diagram of an essential part of an image forming apparatus in which an ultrasonic vibration generating unit is provided in a transfer unit according to the present invention. In the secondary transfer unit shown in FIG. Accordingly, an optimum transfer image is obtained by switching the vibration output of the ultrasonic vibration generating means. 3 and 4 are schematic perspective views showing an example of ultrasonic vibration generating means (ultrasonic vibrator and horn) used in the image forming apparatus of the present invention.

First, the configuration of the ultrasonic vibration generating means will be described.
The ultrasonic vibration generating means includes an ultrasonic vibrator 16 that generates ultrasonic vibration, and a horn 17 that contacts the inside of the intermediate transfer belt 2 and transmits the vibration from the ultrasonic vibrator 16.
Various types of ultrasonic transducers 16 are commercially available, and Langevin type transducers, disc type transducers, flat plate type transducers and the like are common.
The Langevin type vibrator is formed by laminating two piezo discs having the same thickness so that vibration directions are opposite to each other, and covering both ends with metal cylinders. At this time, the resonance condition is that the entire length is λ / 2 (half wavelength). Bolt-clamped Langevin elements are particularly characterized by frequency selectivity and structural robustness. It is a general-purpose material for industrial use and is used in washing machines and welding machines.

  The disc-type vibrator is generally used in a high frequency region, and for example, is often used mainly for beauty appliances with a vibration frequency of 1 MHz to 10 MHz. Two disk-shaped ultrasonic vibrators are stacked and bonded together, and in such a high frequency band, a gel is used as a vibration medium in order to efficiently propagate vibrations.

  In the present invention, a configuration example is shown in which the ultrasonic transducer 16 has a flat plate shape that is long in the same direction as the axial direction of the roller of the secondary transfer portion. This shape has characteristics that it is effective in reducing the size of the device because it is thin and has a space margin when incorporated in the device, and that uniform vibration characteristics can be obtained over the entire width of the horn 17.

  The flat plate type ultrasonic transducer 16 is composed of a single layer ceramic element or a laminate of two or more ceramic elements. The ceramic element used in the present invention has a vibration characteristic having a vibration frequency of about 20 to 200 kHz and an amplitude of about 0.1 to 10 μm (pp). When a plurality of ceramic elements are used, they are pasted with an adhesive.

  As shown in FIG. 3, the horn 17 is made of aluminum die cast, has an exponential curve shape whose cross-sectional shape becomes narrower toward the vibration tip, and amplifies the vibration of the ultrasonic transducer 16 toward the tip. ing. The contact surface with the intermediate transfer belt 2 is mirror-finished, and the leading edge is rounded. Further, as shown in FIG. 4, the horn 17 is provided with slits 22 as necessary to make the amplitude fluctuation uniform in the width direction. The technology related to this horn shape is disclosed in, for example, Patent Document 3 (US Pat. No. 4,363,992) and is considered to be a known technology.

  The ultrasonic transducer 16 is driven by an AC bias as shown in FIG. 2, and a driving circuit is provided with a tracking circuit that stabilizes the frequency and amplitude so that the resonance frequency is achieved by a control circuit / CPU (not shown). To use.

  In FIG. 2, before the paper P as a recording medium enters the secondary transfer process, the surface roughness detection sensor 18 as the surface roughness detection means measures the uneven shape on the surface of the paper P. The surface roughness detection sensor 18 may be provided at an appropriate position as long as it is in the region from the paper feeding unit 1B to the secondary transfer unit. As an embodiment of the surface roughness detection sensor 18, an optical non-contact type sensor is desirable because it affects the paper transportability in the case of a contact type sensor. Among them, the laser displacement sensor is optimal because it is generally highly accurate and hardly affected by paper conveyance.

  In the present invention, the surface roughness of the paper P is detected by the surface roughness detection sensor 18 in synchronization with the conveyance of the paper P, and the data is fed back to the control circuit (not shown) of the ultrasonic transducer 16 to optimize it. The output is controlled so as to have a proper output characteristic.

  As an example of a general paper type of embossed paper used in the market, there is a brand called “Rezak paper 66”. A concave groove is formed on the surface of the paper, and there are varieties ranging from 100 kg paper to 260 kg paper. The continuous groove of 100 kg paper has a maximum depth of about 50 μm, and the continuous weight of 260 kg paper has a maximum depth of about 150 μm. The deeper the groove, the worse the transferability.

  The intermediate transfer belt 2 has a flat nip region formed by a repulsive roller 2C and a driven roller 2D in the secondary transfer portion, and the ultrasonic vibration generating means (the ultrasonic vibrator 16 and the horn 17) is the intermediate transfer belt 2. The tip of the horn 17 is disposed inside the flat nip region. Further, a secondary transfer bias similar to that described above is applied to the repulsive roller 2C from a constant current power source.

  On the other hand, a secondary transfer device 20 is disposed below the sheet P, and in the configuration example of FIG. 2, the secondary transfer device 20 serves as a secondary transfer belt (here, it also serves as paper conveyance). A transfer / conveying belt 19 is provided on the inside of which a driving roller 20A, a driven roller 20B, and a tension roller 20C are provided to drive the transfer / conveying belt 19. Further, at a position facing the intermediate transfer belt 2 inside the transfer conveyance belt 19, an opposing roller 20D that is grounded is disposed in contact with the back surface of the belt.

  The paper P is nipped by a flat nip portion formed by the intermediate transfer belt 2 and the transfer conveyance belt 19 and enters the secondary transfer portion. Since the secondary transfer electric field is generated between the repulsive roller 2C and the counter roller 20D, the secondary transfer process of the toner T is performed between the rollers, and at the same time, the ultrasonic vibrator 16 and the horn 17 of the ultrasonic vibration generating means. In this region, the auxiliary effect of toner transfer is most exhibited. The sheet P on which the toner has been transferred is separated from the intermediate transfer belt 2 and the transfer conveying belt 19 by the curvature of the driven roller 2D and the driving roller 20A, and the separation / discharge means (not shown), and the fixing device 11 shown in FIG. The fixing process is performed, and the print output is completed.

In this configuration example, the output of the ultrasonic vibrator 16 of the ultrasonic vibration generating unit is controlled to be switched according to the depth of the concave groove of the paper P, and the detected concave groove depth is
(1) groove depth less than 50 μm,
(2) Groove depth of 50 μm or more and less than 100 μm,
(3) Groove depth of 100 μm or more and less than 150 μm,
(4) Groove depth of 150 μm or more,
In accordance with these four stages, the drive bias is switched so that the vibration amplitude or vibration speed suitable for each of them is obtained. As a specific example, each vibration output is set to have an amplitude of 1 μm (pp), 2 μm (pp), 3 μm (p -P) 4 μm (pp).

As described above, in the present invention, when the recording medium (paper) P is a paper having an uneven surface such as an embossed paper, an ultrasonic vibration generating means (ultrasonic vibrator) The transfer rate is improved by applying ultrasonic vibration by the 16 and the horn 17).
However, if the drive voltage is increased too much in order to increase the vibration speed of the ultrasonic vibration generating means (ultrasonic vibrator 16 + horn 17), the characteristics deteriorate due to heat generation of the ultrasonic vibrator itself constituting the ultrasonic vibration generating means. As a result, problems such as the inability to maintain sufficient ultrasonic vibration occur.

  Therefore, in the present invention, a plurality of ultrasonic vibration generating means are used, and the driving of the plurality of ultrasonic vibration generating means is switched, or the contact or separation of the plurality of ultrasonic vibration generating means with respect to the image carrier is switched. By doing so, the durability of the ultrasonic wave generation means is maintained over time, thereby maintaining the optimum image quality.

  More specifically, in the present invention, a plurality of ultrasonic vibration generating means are arranged in parallel in the moving direction of the intermediate transfer belt 2 inside the intermediate transfer belt (image carrier) 2 of the secondary transfer portion, and the surface roughening is performed. The toner image is transferred by switching the driving of the plurality of ultrasonic vibration generating means or switching the contact or separation mode of the plurality of ultrasonic vibration generating means according to the detection value of the height detection sensor 18. .

  FIG. 5 is a diagram showing an embodiment of the present invention, and is a schematic configuration diagram of an essential part of an image forming apparatus provided with a plurality of ultrasonic vibration generating means in a secondary transfer portion. Specifically, in the configuration example of FIG. 5, a plurality of ultrasonic vibration generating means (in FIG. 5, the first ultrasonic vibration is generated inside the intermediate transfer belt 2 of the secondary transfer portion in the moving direction of the intermediate transfer belt 2). Means (ultrasonic transducer 16a and horn 17a) and second ultrasonic vibration generating means (ultrasonic transducer 16b and horn 17b)) are arranged in parallel, and the other configurations are the same as those in FIG. . In the example of FIG. 5, two ultrasonic vibration generating means are provided, but the number is not limited to two, and three or more may be provided in parallel.

  In the configuration example of FIG. 2 described above, the output of one ultrasonic transducer 16 is switched according to the groove depth of the paper P detected by the surface roughness detection sensor 18, but in the configuration example of FIG. , Intermediate transfer of a plurality of ultrasonic vibration generating means (first ultrasonic vibration generating means (ultrasonic transducer 16a and horn 17a), second ultrasonic vibration generating means (ultrasonic transducer 16b and horn 17b)) Greater vibration can be obtained by contacting the belt 2 between the repulsive roller 2 </ b> C and the counter roller 20 </ b> D, which is an area where the secondary transfer electric field is effective, on the inner side (back side) of the belt 2. As an example, the groove depth detection region (1) to (2) described above is driven by switching the output of the ultrasonic transducer 16a of the first ultrasonic vibration generating means, and (3) to (3) For the concave groove depth detection region of 4), by driving the ultrasonic vibrator 16a of the first ultrasonic vibration generating means and the ultrasonic vibrator 16b of the second ultrasonic vibration generating means, Greater vibrations can be obtained to further improve the transfer rate. Other actions and operations are the same as those in FIG.

  In this way, since the operation time of one ultrasonic transducer can be shortened by switching the driving of the ultrasonic transducers 16a and 16b of the plurality of ultrasonic vibration generating means, the ultrasonic transducer can be maintained over time. It is possible to maintain the durability and the optimum image quality.

Next, FIGS. 6 and 7 are diagrams showing another embodiment of the present invention, and a schematic configuration of a main part of an image forming apparatus in which a plurality of ultrasonic vibration generating means are provided in a secondary transfer portion so as to be able to contact and separate. FIG.
In the embodiment shown in FIGS. 6 and 7, a plurality of ultrasonic vibration generating means (for example, first ultrasonic vibration generating means (ultrasonic transducer 16a) in the moving direction of the intermediate transfer belt 2 inside the intermediate transfer belt 21 are used. Horn 17a) and second ultrasonic vibration generating means (ultrasonic transducer 16b and horn 17b)), and first ultrasonic vibration generating means (ultrasonic transducer 16a and horn 17a) Surface roughness detection for detecting the surface roughness of the recording medium (paper) P by providing second ultrasonic vibration generating means (ultrasonic transducer 16b and horn 17b) so as to be able to contact and separate from the intermediate transfer belt 21. Two ultrasonic vibration generating means (first ultrasonic vibration generating means (ultrasonic vibrator 16a and horn 17a) and second ultrasonic vibration generating means (ultrasonic vibrator 16b) according to the detection value of the sensor 18. And horn 17b)) in the middle Contact with shooting belt 21, or is obtained by a structure for switching the mode to separate.
6 and FIG. 7, two ultrasonic vibration generating means are provided, but the number is not limited to two, and three or more may be provided in parallel.
Further, the contacting / separating operation of each ultrasonic vibration generating means can be performed by providing a vertically movable mechanism on a support member that supports both longitudinal sides of the ultrasonic vibration generating means. For example, the ultrasonic vibration generating means The support member is supported by a spring member such as a spring so that it can move up and down, and a mechanism that moves up and down using a cam, a link, etc. driven by a motor or solenoid, or a mechanism that moves up and down using a rack and pinion mechanism Any known one can be used as appropriate.

  In the configuration example of FIG. 5, a plurality of ultrasonic vibration generating means (first ultrasonic vibration generating means (ultrasonic transducer 16a and horn 17a) and second ultrasonic vibration generating means (ultrasonic transducer 16b and The horn 17b)) is brought into contact between the repulsive roller 2C and the counter roller 20D, which is an area where the secondary transfer electric field is effective, on the back side of the intermediate transfer belt 21, but in this case, the horn 17b)) There is a possibility that problems such as deterioration of the vibration characteristics of the ultrasonic transducers 16a and 16b or wear of the horns 17a and 17b due to contact with the intermediate transfer belt 2 may occur.

  Therefore, in the embodiments shown in FIGS. 6 and 7, a plurality of ultrasonic vibration generating means (first ultrasonic vibration generating means (ultrasonic transducer 16a and horn 17a) and second ultrasonic vibration generation are provided. One of the means (ultrasonic vibrator 16b and horn 17b) (first ultrasonic vibration generating means (ultrasonic vibrator 16a and horn 17a) in FIG. 6) is driven in contact with the intermediate transfer belt 2. The other ultrasonic vibration generating means (second ultrasonic vibration generating means (ultrasonic transducer 16b and horn 17b)) is separated from the intermediate transfer belt 2 and stops driving, and the mode is changed at a predetermined time. As shown in FIG. 7, the second ultrasonic vibration generating means (ultrasonic transducer 16b and horn 17b) is driven in contact with the intermediate transfer belt 2 to drive the first ultrasonic vibration generating means (ultrasonic wave). Sonic transducer 16a and horn 17a To the stop to drive away from the intermediate transfer belt 2, and so on, by switching the modes of the drive and contact and separation operation, but can solve the problem of aging of the ultrasonic vibration generating means.

That is, in this embodiment, control is performed so that different ultrasonic transducers 16 are brought into contact with each other according to the depth of the groove of the paper P, and the detected groove depth of the paper is
(1) Groove depth less than 100 μm,
(2) Groove depth of 100 μm or more,
The different ultrasonic vibration generating means (first ultrasonic vibration generating means (ultrasonic transducer 16a and horn 17a) and second ultrasonic vibration generating means (ultrasonic vibration) suitable for each of the two stages The child 16b and the horn 17b)) are switched, and as a specific example, the first superstructure is detected as shown in FIG. The sonic vibration generating means (ultrasonic transducer 16a and horn 17a) are brought into contact with each other so that the vibration output has an amplitude of 1 to 2 [mu] m (pp). As shown in FIG. 2, the second ultrasonic vibration generating means (ultrasonic transducer 16b and horn 17b) is brought into contact with each other so that the vibration output has an amplitude of 3 to 4 μm (pp).

  In this way, by using a plurality of ultrasonic vibration generating means by switching between contact or separation, the operating time of one ultrasonic vibration generating means (ultrasonic vibrator) can be shortened simultaneously with output switching. In this case, it is possible to maintain the durability of the ultrasonic transducer and maintain the optimum image quality.

In the present invention, a plurality of ultrasonic vibration generating means (first ultrasonic vibration generating means (ultrasonic transducer 16a and horn 17a) and The second ultrasonic vibration generating means (the ultrasonic transducer 16b and the horn 17b) can be driven by simultaneously contacting the back surface of the intermediate transfer belt 2, but in such a case, the same frequency band is used. If a phase difference occurs when driven, vibrations may be canceled in the opposite phase. That is, when a plurality of ultrasonic vibration generating means are used in contact with the back surface of the intermediate transfer belt 2 at the same time, if the ultrasonic vibration elements 16a and 16b have the same resonance frequency, the vibration characteristics for the paper P are In some cases, the phase is canceled in the opposite phase, and the transfer efficiency is reduced.
Therefore, when a plurality of ultrasonic vibration generating means are used at the same time, it is desirable that the resonance frequencies of the ultrasonic transducers 16a and 16b of the plurality of ultrasonic vibration generating means have different characteristics.

  Thus, since the ultrasonic transducers 16a and 16b of the plurality of ultrasonic vibration generating means have different frequency characteristics, the plurality of ultrasonic vibration generating means are simultaneously brought into contact with the back surface of the intermediate transfer belt 2. Even when used, the vibration characteristics of the plurality of ultrasonic vibration generating means with respect to the paper P are not canceled out of phase, so that the optimum image quality can always be maintained over time.

As described above, the configuration and the transfer method of the secondary transfer unit that transfers the toner image from the intermediate transfer belt to the recording medium (paper) have been described as examples of the present invention. However, the present invention is particularly limited to the secondary transfer unit. In addition, the present invention can be similarly applied to a paper transfer unit in an image forming system using an image carrier such as a belt-like photoreceptor (photoreceptor belt).
That is, the present invention can be similarly applied to an image forming apparatus that directly transfers a toner image formed on a photosensitive belt, which is an image carrier, through a process of charging, exposure, and development to a recording medium (paper). As a specific example, if the intermediate transfer belt 2 shown in FIG. 6 is replaced with a photosensitive belt, and a charging device, an optical writing device, and a developing device are arranged in place of the image forming stations of the respective colors, the direct transfer type image is obtained. In the paper transfer unit, a plurality of ultrasonic vibration generating means (ultrasonic vibrator and horn) are arranged in parallel in the paper transfer portion, and the surface roughness detection sensor 18 is provided in the same manner as in the above embodiment. The same effect can be obtained by controlling the driving and contacting / separating operations of a plurality of ultrasonic vibration generating means (ultrasonic transducers and horns) according to the detection result.

  As described above, the present invention is characterized by assisting toner transfer in a transfer section that transfers a toner image from an image carrier (photosensitive body or intermediate transfer body) to a recording medium such as paper. As another application field, it can be applied to a welding machine using ultrasonic vibration and toner cleaning assistance using ultrasonic vibration in an image forming apparatus.

1: Color copier (image forming device)
DESCRIPTION OF SYMBOLS 1A: Image formation part 1B: Paper feed part 1B1: Paper feed tray 1B2: Pair of conveyance rollers 1B3: Pair of registration rollers 1C: Document conveyance part 1D: Scanner part 2: Intermediate transfer belt (intermediate transfer body (image carrier))
2A: driven roller 2B: driving roller 2C: repulsive roller 2D: driven roller 3Y, 3M, 3C, 3B: photoconductor 4Y, 4M, 4C, 4B: charging device 5: writing device 6Y, 6M, 6C, 6B: developing device 7Y, 7M, 7C, 7B: Primary transfer device 8Y, 8M, 8C, 8B: Photoconductor cleaning device 9A: Conveyor belt 9B: Driven roller 9C: Conveyance drive roller 10: Intermediate transfer belt cleaning device 11: Fixing device 12 : Discharge roller 13: discharge tray 14: tension roller 15: pair of registration rollers 16 (16a, 16b): ultrasonic vibrator (ultrasonic vibration generating means)
17 (17a, 17b): Horn (Ultrasonic vibration generating means)
18: Surface roughness detection sensor (surface roughness detection means)
19: transfer conveyor belt 20: secondary transfer device 20A: drive roller 20B: driven roller 20C: tension roller 20D: counter roller 22: slit P: paper (recording medium)
T: Toner

JP-A 52-126230 JP-A-4-234077 US4363632

Claims (11)

In an image transfer method for transferring a toner image carried by an image carrier to a recording medium at a transfer unit,
Surface roughness detection means for detecting the surface roughness of the recording medium;
A plurality of ultrasonic vibration generating means disposed inside the image carrier of the transfer unit,
An image transfer method, wherein a toner image is transferred by switching driving of the plurality of ultrasonic vibration generating means according to a detection value of the surface roughness detecting means. The image transfer method according to claim 1,
The plurality of ultrasonic vibration generating means are provided so as to be able to come into contact with and separate from the image carrier, and the plurality of ultrasonic vibration generating means are attached to the image carrier according to the detection value of the surface roughness detecting means. An image transfer method, characterized in that the image transfer method is characterized in that the image is transferred to or separated from the image transfer. The image transfer method according to claim 1 or 2,
The ultrasonic vibration generating means includes an ultrasonic vibrator that generates ultrasonic vibration, and a horn that contacts the inside of the image carrier and transmits the vibration from the ultrasonic vibrator. Image transfer method. In the image transfer method according to any one of claims 1 to 3,
The image transfer method, wherein the plurality of ultrasonic vibration generating means have different frequency characteristics. In an image forming method in which a toner image carried by an image carrier is transferred to a recording medium by a transfer unit, and an image is formed on the recording medium.
An image forming method using the image transfer method according to claim 1. In an image forming apparatus having a transfer unit for transferring a toner image carried by an image carrier to a recording medium,
Surface roughness detection means for detecting the surface roughness of the recording medium;
A plurality of ultrasonic vibration generating means disposed inside the image carrier of the transfer unit,
An image forming apparatus, wherein toner images are transferred by switching driving of the plurality of ultrasonic vibration generating means according to a detection value of the surface roughness detecting means. The image forming apparatus according to claim 6.
The plurality of ultrasonic vibration generating means are provided so as to be able to come into contact with and separate from the image carrier, and the plurality of ultrasonic vibration generating means are selected according to the detection value of the surface roughness detecting means. An image forming apparatus, wherein a mode for contacting or separating the image carrier is switched. The image forming apparatus according to claim 6 or 7,
The ultrasonic vibration generating means includes an ultrasonic vibrator that generates ultrasonic vibration, and a horn that contacts the inside of the image carrier and transmits the vibration from the ultrasonic vibrator. Image forming apparatus. The image forming apparatus according to any one of claims 6 to 8,
The image forming apparatus, wherein the plurality of ultrasonic vibration generating means have different frequency characteristics. The image forming apparatus according to any one of claims 6 to 9,
A photoreceptor, image forming means for forming a toner image on the photoreceptor, an endless belt-shaped intermediate transfer body on which the toner image is primarily transferred from the photoreceptor, and a toner image from the intermediate transfer body to a recording medium; Having a secondary transfer part to transfer,
The image carrying member is the intermediate transfer member, and a plurality of ultrasonic vibration generating means are arranged in parallel in the moving direction of the intermediate transfer member inside the intermediate transfer member of the secondary transfer unit. Forming equipment. The image forming apparatus according to any one of claims 6 to 9,
An endless belt-shaped photoreceptor, image forming means for forming a toner image on the photoreceptor, and a transfer unit for transferring the toner image from the photoreceptor to a recording medium,
The image carrier is the photoreceptor;
An image forming apparatus comprising a plurality of ultrasonic vibration generating means arranged in parallel in the moving direction of the photoconductor inside the photoconductor of the transfer section.

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