JP2005202122A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which even an intermediate transfer member having rubber elasticity can be very effectively cleaned. <P>SOLUTION: The image forming apparatus comprises: image forming stations (image forming sections) Pa-Pd provided with traveling photosensitive drums (image carriers) 1a-1d and developing units (developing devices) 23a-23d which supply toners to surfaces of the photosensitive drums 1a-1d; an intermediate transfer belt (intermediate transfer member) 81 onto which toner images formed in the image forming stations Pa-Pd are transferred and compositzed; and a cleaning means to remove residual toners on the intermediate transfer belt 81 after transferring a toner image composited on the intermediate transfer belt 81 onto a recording material P. The intermediate transfer belt 81 includes a rubber elasticity layer, the cleaning means comprises a rotatable fur brush (brushy member) 20A, and vibration of ≥20 Hz is applied to the fur brush 20A. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic system.

  Conventionally, a toner image is formed on an image carrier, which is a drum-shaped or belt-shaped photosensitive member, the toner image is transferred onto a drum-shaped or belt-shaped intermediate transfer belt, and the toner on the intermediate transfer belt is further transferred. An image forming apparatus that employs a system for transferring an image onto a transfer sheet is widely known.

  In addition, with the recent colorization, a tandem (4-drum) system that has a plurality of image forming portions that form toner images on an image carrier and forms toner images of a plurality of colors on an intermediate transfer member at a time is adopted. An electrophotographic image forming apparatus has been widely recognized.

  Such an image forming apparatus will be described with reference to FIG.

  FIG. 4 is a cross-sectional view of the image forming apparatus. An endless intermediate transfer belt 81 that runs in the direction of arrow X is disposed in the main body of the image forming apparatus. The material P is conveyed to the left in FIG. 4 through the registration roller 213.

  Above the intermediate transfer belt 81, four image forming stations Pa, Pb, Pc, Pd having substantially the same configuration are arranged in series. Here, the configuration of the image forming station Pa will be described as an example.

  The image forming station Pa is provided with a drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1a rotatably arranged. Around the photosensitive drum 1a, a primary charger 22a and a developing device are provided. Process equipment such as a vessel 23a is arranged. The other image forming stations Pb, Pc, and Pd have the same configuration as the image forming station Pa. As shown in the figure, primary chargers 22b, 22c are provided around the photosensitive drums 1b, 1c, 1d, respectively. , 22d, developing devices 23b, 23c, 23d and the like are arranged in the same manner. These image forming stations Pa, Pb, Pc, and Pd are different in that toner images of magenta, cyan, yellow, and black are formed.

  Here, it is assumed that magenta toner, cyan toner, yellow toner, and black toner are stored in the developing units 23a, 23b, 23c, and 23d disposed in the image forming stations Pa, Pb, Pc, and Pd, respectively.

  By the way, as the developing method of the electrostatic latent image with toner, there are generally known methods roughly classified into the following four types a) to d).

a) Non-magnetic toner is coated on the sleeve with a blade or the like, and the magnetic toner is coated by magnetic force and conveyed, and developed in a non-contact state with respect to the photoreceptor (one-component non-contact development method).
b) A method in which the toner coated as described above is developed in contact with the photoreceptor (one-component contact development method).
c) A method in which toner particles mixed with a magnetic carrier are used as a developer, which is conveyed by magnetic force, and developed in contact with a photoreceptor (two-component contact development method).
d) A method in which the two-component developer is developed in a non-contact state (two-component non-contact development method).
Among the above developing methods, the two-component contact developing method c) is often used from the viewpoint of high image quality and high stability. In this conventional example, this two-component contact development method is adopted for the color toner.

  Thus, an image signal based on the magenta component color of the original is projected onto the photosensitive drum 1a of the image forming station Pa via a polygon mirror (not shown), and an electrostatic latent image is formed on the photosensitive drum 1a. Then, magenta toner is supplied from the developing unit 23a to the electrostatic latent image, and the electrostatic latent image is visualized as a magenta toner image. When the magenta toner image arrives at a transfer portion where the photosensitive drum 1a and the intermediate transfer belt 81 come into contact with the rotation of the photosensitive drum 1a, the first transfer bias applied by the first transfer member 241a causes The magenta toner image is transferred onto the intermediate transfer belt 81. When the intermediate transfer belt 81 carrying the magenta toner image is transported to the image forming station Pb, the cyan toner formed on the photosensitive drum 1b in the image forming station Pb by the same method as described above. The image is transferred onto the magenta toner image on the intermediate transfer belt 81.

  Similarly, as the toner image on the intermediate transfer belt 81 advances to the image forming stations Pc and Pd, the yellow toner image and the black toner image are superimposed and transferred onto the above-described toner image at the respective transfer portions. By the time, the recording material P taken out from the paper feed cassette 60 reaches the transfer portion, and the four color toner images are transferred onto the recording material P by the transfer bias applied to the transfer member 40. Thereafter, the recording material P onto which the four color toner images have been transferred is conveyed to the fixing unit 250 where the toner image is fixed by heat and pressure. Then, the recording material P on which the toner image is fixed is discharged to a paper discharge tray 251. When a double-sided image is automatically formed, the recording material P passes through a recording material reversing path (not shown), and is a double-sided cassette. And is fed during double-sided image formation.

  An intermediate transfer belt cleaning member 216 is disposed at a downstream position of the transfer portion of the intermediate transfer belt 81, and toner and the like attached to the intermediate transfer belt 81 are removed by the intermediate transfer belt cleaning member 216.

  Incidentally, the intermediate transfer belt 81 has a single layer having rubber elasticity, or at least one layer has a laminated structure including an elastic layer having rubber elasticity. By providing the elastic layer on the belt itself in this way, good transfer can be performed even if there are slight irregularities on the surface of the recording material.

Japanese Patent Laid-Open No. 11-344851 JP 2001-312159 A

  Incidentally, in the case of the intermediate transfer member having the elastic layer as described above, it is very difficult to clean the toner adhering to the surface. Conventionally, as a cleaning member, blade cleaning with a rubber blade is often used because it is inexpensive and has good cleaning performance. However, when the intermediate transfer member has rubber elasticity, the behavior of the blade tip becomes unstable. Thus, there is a problem that the performance is remarkably deteriorated.

  In addition, as a cleaning device using a cleaning member other than a rubber blade, a fur brush device that cleans the surface of an object to be cleaned by rotating brushed hair around a cylinder, or a magnetic brush using magnetic fine particles There are devices, etc., and the cleaning member used in these devices is not necessarily inferior in performance even if the member to be cleaned has an elastic layer, but since the cleaning performance is inferior to the blade method in the first place, It is difficult to exhibit sufficient cleaning performance by itself.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of cleaning very effectively even for an intermediate transfer member having rubber elasticity. .

  In order to achieve the above object, an invention according to claim 1 is directed to an image forming unit including a traveling image carrier, a developing device that supplies toner to the surface of the image carrier, and a toner image formed by the image forming unit. An image forming apparatus having a belt-like intermediate transfer member to be transferred and synthesized, and a cleaning unit for cleaning a transfer residual toner on the intermediate transfer member after transferring a toner image synthesized on the intermediate transfer member to a recording material The intermediate transfer member includes a rubber elastic layer, and the cleaning unit includes a rotatable brush-like member, and vibrations of 20 Hz or more are applied to the brush-like member.

  The invention according to claim 2 is the invention according to claim 1, wherein a plurality of the brush-like members are provided, and the vibration is applied to at least one brush-like member.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a plurality of the brush-like members are provided, and the vibration is selectively applied to the brush-like member by switching.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the vibration is a vibration of 20000 Hz or more.

  According to a fifth aspect of the present invention, in the toner according to any one of the first to third aspects, the toner has shape factors SF-1 and SF-2 values of 100 ≦ SF-1 ≦ 160 and 100 ≦. SF-2 ≦ 140.

  According to the present invention, by applying high-frequency vibration, particularly vibration of 20 Hz or more, desirably ultrasonic vibration of 20000 Hz or more, to the brush-like member, the cleaning ability of the brush-like member can be dramatically improved.

  That is, when a high frequency of 20000 Hz or more is applied to the brush-like member, the brush tip hardly vibrates, but an ultrasonic wave is emitted from the brush tip, and the surface of the intermediate transfer member as the member to be cleaned and the toner attached to the surface. This is effective in making the toner easy to clean.

  Normally, if the intermediate transfer member is vibrated, the image is often adversely affected. However, the vibration is very high frequency, and the intermediate transfer member, which is the member to be cleaned, has rubber elasticity, resulting in local vibration. No adverse effect on the image occurs.

  Also, by providing a plurality of brush-like members and applying ultrasonic vibration to the upstream brush-like member, the toner on the intermediate transfer member can be easily cleaned, and the remaining toner is completely removed by the downstream brush-like member. If there is a large amount of residual toner, the upstream brush-like member first roughly cleans the intermediate transfer member, and then the remaining toner is subjected to ultrasonic vibration applied to the downstream brush. You may make it remove with a shape member.

  As described above, by using the brush-like member to which ultrasonic vibration is applied as the cleaning means, it is possible to clean the intermediate transfer member having rubber elasticity very effectively.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
In the image forming apparatus according to the present embodiment, toner produced by a polymerization method is used as a developer. In general, a toner produced by a polymerization method has a very high sphericity, and it is relatively easy to maintain a transfer efficiency of 98% or more. By adopting the intermediate transfer method as the transfer method, it is possible to maintain high transfer efficiency relatively stably under any conditions.

  By the way, if the sphericity of the toner is poor, the amount of toner remaining after transfer increases. With respect to the sphericity of the toner, when the value of the shape factor SF-1 measured by the image analyzer is 100 ≦ SF-1 ≦ 160 and the value of SF-2 is 100 ≦ SF-2 ≦ 140, the transfer is sufficient. It has been found that it is possible to demonstrate efficiency.

  Here, SF-1 and SF-2 indicating the shape factor of the toner are defined as follows. That is, for example, using FE-SEM (S-800) manufactured by Hitachi, 100 toner images of 2 μm or larger magnified 1000 times are randomly sampled, and the image information is analyzed through an interface, for example, image analysis manufactured by Nicole. Analysis is performed by introducing the apparatus (Luzex III), and values obtained by calculation from the following equations are defined as shape factors SF-1 and SF-2.

SF-1 = ((MXLIG) ² / (AREA)) × (π / 4) × 100
SF-2 = ((PEREME) ² / (AREA)) × (1 / 4π) × 100
(Where MXLNG is the absolute maximum length of the particle, PERIME is the perimeter of the particle, and AREA is the projected area of the particle)
The shape factor SF-1 indicates the degree of roundness of the toner particles, and the shape factor SF-2 indicates the degree of unevenness of the toner particles. The closer these values are to 100, the closer to the true sphere.

  When the toner shape factor SF-1 exceeds 160, the toner moves away from the spherical shape and approaches an indeterminate shape, the toner is easily crushed in the developing device, the particle size distribution is fluctuated, the charge amount distribution is likely to be broad, And inversion fog are likely to occur.

  Thus, a toner with high sphericity can be produced by the following polymerization method.

  That is, a method for obtaining a spherical toner by atomizing a molten mixture into air using a disk or a multi-fluid nozzle described in JP-B-56-13945, JP-A-59-53856, Direct toner production using a suspension polymerization method described in Japanese Utility Model Publication No. 59-61842 or the like, or using a water-based organic solvent that is soluble in the monomer and insoluble in the polymer. It is possible to produce a toner using an emulsion polymerization method typified by a dispersion polymerization method for producing a toner or a soap-free polymerization method for producing a toner by direct polymerization in the presence of a water-soluble polar polymerization initiator.

  Of the above production methods, the suspension polymerization method is particularly preferred. A seed polymerization method in which a monomer is further adsorbed to the obtained polymer particles and then polymerized using a polymerization initiator can also be suitably used in the present invention.

  Furthermore, it is also preferable to add polar resins such as a copolymer of styrene and (meth) acrylic acid, a maleic acid copolymer, and a saturated polyester resin.

  By using such a toner, it is possible to maintain the transfer efficiency in a very high state and extremely reduce the transfer residual toner.

  An image forming apparatus using the toner and the intermediate transfer belt as described above is shown in FIG.

  FIG. 1 is a sectional view of an image forming apparatus according to the present invention. In the following description, portions not particularly shown are the same as those of the conventional image forming apparatus shown in FIG.

  As shown in FIG. 1, above the intermediate transfer belt 81, four image forming stations Pa, Pb, Pc, Pd having substantially the same configuration are arranged in series, and the respective photosensitive drums 1a, 1a, Magenta, cyan, yellow, and black toner images are formed on 1b, 1c, and 1d, and the toner images are transferred onto the intermediate transfer belt 81 from the respective photosensitive drums 1a, 1b, 1c, and 1d. Are synthesized. The toner image synthesized in this way is transferred onto the recording material P, and then the toner or the like adhering to the intermediate transfer belt 81 is a fur brush disposed at a position downstream of the transfer portion of the intermediate transfer belt 81. Removed by 20A.

Here, the intermediate transfer belt 81 employs a belt material in which carbon, which is an electronic conductive material, is dispersed. Thus, by dispersing carbon in the belt, the surface resistivity of the belt is set to 10 ^11.2 to 10 ^12.4 Ω / □, and the volume resistivity is set to 10 ⁹ to 10 ¹¹ Ω · cm. .

  This belt has a laminated structure, and a member having rubber elasticity such as chloroprene rubber or urethane rubber is used at the center thereof. By providing the elastic layer on the belt itself in this way, good transfer can be performed even if there are slight irregularities on the surface of the recording material. In other words, good transfer can be performed even with paper having a rough surface, recording materials such as embossed paper and Japanese paper.

  By combining the elastic intermediate transfer belt 81 and the above-described spherical toner, a very high transfer efficiency can always be maintained. Therefore, the intermediate transfer belt cleaning member 216 only needs to remove a small amount of residual toner.

  However, in the case of an intermediate transfer member having such an elastic layer, it is very difficult to clean the toner adhering to the surface. Conventionally, as a cleaning means, blade cleaning with a rubber blade is often used because it is inexpensive and has good cleaning performance. However, when the intermediate transfer member has rubber elasticity, the behavior of the rubber blade tip Becomes unstable, and there is a problem that the performance is remarkably deteriorated.

  Further, although the amount of transfer residual toner is small for the reasons described above, the adhesion between the intermediate transfer member and the transfer residual toner is strong, and cleaning becomes difficult.

  Therefore, in the present embodiment, a cleaning member is provided in which the cleaning capability is dramatically improved by applying high-frequency vibrations to the fur brush.

That is, in the present embodiment, the fur brush 20A is disposed in contact with the intermediate transfer belt 81 as shown in FIG. The fur brush 20 </ b> A includes a cored bar 24 having an outer diameter of 10 mm and a fur brush part 25 planted on the cored bar 24. Here, the fur brush portion 25 is formed by implanting conductive fibers having a bristle length of 3 mm and a resistance value of 1 × 10 ⁶ Ω at a density of 100,000 pieces / inch ² .

  The fur brush 20 </ b> A is disposed substantially parallel to the intermediate transfer belt 81 with the fur brush portion 25 contacting the surface of the intermediate transfer belt 81. In this case, the fur brush 20 </ b> A was adjusted and disposed so that the contact nip width N of the fur brush portion 25 formed on the intermediate transfer belt 81 was about 7 mm.

  The core metal 24 of the fur brush 20A has a contact nip width N of 100 mm / sec with respect to the rotational peripheral speed of the intermediate transfer belt 81 in the clockwise direction indicated by an arrow that is opposite to the rotation direction of the intermediate transfer belt 81 (counter direction). It was rotated at 200 mm / sec, twice.

  A vibration oscillator 26 for applying a high frequency of 20000 Hz or more is provided inside the metal core 24, and the vibration of the vibration oscillator 26 is controlled by a vibration control circuit 27.

  When a high frequency is applied to the fur brush portion 25 of the fur brush 20A by the vibration oscillator 26, the brush tip hardly vibrates, but an ultrasonic wave is emitted from the brush tip, and the surface of the intermediate transfer belt 81 which is a member to be cleaned. Further, vibration can be applied to the toner adhering to the surface, and the adhesion force between the intermediate transfer belt 81 and the toner can be reduced. Normally, a fur brush is inferior in cleaning ability to blade cleaning, and therefore it is not usually used for cleaning an image carrier that carries a toner image, but a fur brush alone is not used. In addition to a system with little residual toner, cleaning with a fur brush alone was made possible by applying vibrations of sonic vibration (20 Hz or more) to the brush. In general, if vibration is applied to the intermediate transfer member, the image may be adversely affected. However, vibration is very high and the intermediate transfer member, which is a member to be cleaned, has rubber elasticity. Becomes local, and no adverse effect on the image occurs.

  In particular, when a high frequency (ultrasonic vibration) of 20000 Hz or more is applied to the fur brush, the brush tip hardly vibrates, but an ultrasonic wave is emitted from the brush tip, and the surface of the intermediate transfer belt 81 as a member to be cleaned and the surface thereof. Vibration is applied to the adhered toner, and the surface of the intermediate transfer belt 81 is easily cleaned. Further, since the brush tip hardly vibrates, no mechanical pressing force or scratches are generated on the intermediate transfer belt 81, and it is optimal for the surface layer of the toner that is easily filmed or the intermediate transfer belt 81 that is easily damaged.

The high-frequency vibration oscillator 26 provided inside the fur brush is good when a piezoelectric element is used. For example, it is preferable to use ceramics such as a solid solution of a ferroelectric lead titanate PbTiO ₃ called PZT and an antiferroelectric lead zirconate PbZrO _3. Etc. may be used.

<Embodiment 2>
Next, a second embodiment of the present invention will be described.

  In the present embodiment, an example in which two fur brushes 20A and 20B are used is shown.

  FIG. 3A shows a form in which vibrations equal to or higher than sonic vibrations are applied to the fur brush 20B on the upstream side (lower side in the figure). This is effective when the adhesion force between the intermediate transfer belt 81 and the toner is very strong (for example, when the charge amount of the transfer residual toner is very large). In other words, a configuration is adopted in which the adhesion force between the intermediate transfer belt 81 and the toner is weakened by the upstream fur brush 20B, and the toner is scraped off by the downstream (upper side in the drawing) fur brush 20A. In FIG. 3, 26 is a vibration oscillator and 27 is a vibration control circuit.

  FIG. 3B shows a mode in which ultrasonic vibration is applied to the fur brush 20A on the downstream side. This is effective when the amount of toner scraped off by the fur brush is large. When the amount of toner is large, it becomes difficult to vibrate all of the toner by ultrasonic vibration. Therefore, most of the toner is scraped off in advance by the upstream fur brush 20B, and the toner remaining on the intermediate transfer belt 81 is cleaned cleanly by the downstream fur brush 20A to which ultrasonic vibration is applied. It is a thing.

  Of course, ultrasonic vibrations may be applied to both fur brushes 20A and 20B, but a sufficient performance increase cannot be obtained for a large apparatus and cost. Rather, as shown in FIG. 3C, a changeover switch SW is provided so that ultrasonic vibration can be selectively applied to the upstream fur brush 20B and the downstream fur brush 20A, and switched according to the amount of toner. It is more effective to use it while switching with the switch SW.

  That is, when the amount of toner to be cleaned is small, such as normal transfer residual toner, ultrasonic vibration is applied to the upstream fur brush 20B so that the image control (registration control) can be performed during a return operation after a paper jam. When the amount of toner to be cleaned is very large, such as when an image is formed on the intermediate transfer belt 81 for image density control, etc., ultrasonic vibration is applied to the fur brush 20A on the downstream side. It is effective to adopt a cleaning structure.

  In the present embodiment, the case where two fur brushes are used has been described, but it is needless to say that three or more fur brushes may be used.

  INDUSTRIAL APPLICABILITY The present invention is highly applicable to an image forming apparatus having a cleaning unit for cleaning a transfer residual toner on an intermediate transfer member after a toner image synthesized on a belt-shaped intermediate transfer member is transferred to a recording material. .

1 is a cross-sectional view of an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a partial detail view showing a configuration of a fur brush of the image forming apparatus according to Embodiment 1 of the present invention. (A)-(c) is a partial detail figure which shows the structure of the fur brush of the image forming apparatus which concerns on Embodiment 2 of this invention, and its usage form. It is sectional drawing of the conventional image forming apparatus.

Explanation of symbols

1a to 1d Photosensitive drum (image carrier)
20A, 20B Fur brush (brush-like member: cleaning means)
22a-22d Primary charger 23a-23d Developer (developer)
24 Core Bar 25 Fur Brush Unit 26 Vibration Oscillator 27 Vibration Control Circuit 81 Intermediate Transfer Belt (Intermediate Transfer Body)
P Recording material Pa to Pd Image forming station (image forming unit)
SW selector switch

Claims (5)

An image forming unit including a traveling image carrier, a developing device that supplies toner to the surface of the image carrier, a belt-like intermediate transfer member that transfers and synthesizes a toner image formed by the image forming unit, and the intermediate In an image forming apparatus having a cleaning unit for cleaning a transfer residual toner on an intermediate transfer body after transferring a toner image synthesized on a transfer body to a recording material,
An image forming apparatus characterized in that the intermediate transfer member includes a rubber elastic layer, the cleaning means is composed of a rotatable brush-like member, and vibrations of 20 Hz or more are applied to the brush-like member.   The image forming apparatus according to claim 1, wherein a plurality of the brush-like members are provided, and the vibration is applied to at least one brush-like member.   The image forming apparatus according to claim 1, wherein a plurality of the brush-like members are provided, and the vibration is selectively applied to the brush-like members by switching.   The image forming apparatus according to claim 1, wherein the vibration is vibration of 20000 Hz or more.   5. The toner according to claim 1, wherein the shape factors SF- 1 and SF- 2 have a value of 100 ≦ SF-1 ≦ 160 and 100 ≦ SF-2 ≦ 140. Image forming apparatus.

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