JP2016071287A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can cause a waste toner to reflow for reuse without reducing image quality with foreign substances included in the recovered waste toner and without unnecessarily consuming the toner.SOLUTION: There is provided an image forming apparatus (1) including a photoreceptor drum (32), a developing device (35) that includes a developing roller (35a) and a developer regulation member (35c) and develops an electrostatic latent image formed on the photoreceptor drum (32) to form a toner image, and a cleaner unit (37) that recovers a toner remaining on the photoreceptor drum (32), and causes a recovered waste toner to reflow in the developing device (35), where the developing device (35) includes a foreign substance recovery member 45 that recovers foreign substances mixed in the waste toner; the foreign substance recovery member 45 has four electrodes (D1, D2, D3, and D4), and the adjacent electrodes apply voltages at different timings.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a waste toner collecting unit that removes and collects toner remaining on a photosensitive drum.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses such as copying machines, printers, and facsimiles are known. When image formation is performed in such an image forming apparatus, generally, as shown in FIG. 16, a drum-shaped image carrier (hereinafter referred to as a photosensitive drum) 132 having a photosensitive layer formed on the surface thereof is provided. After rotating, the surface of the photosensitive drum 132 is charged by the charger 134, and then the surface of the charged photosensitive drum 132 is exposed according to image information by an exposure device (not shown). An electrostatic latent image is formed on the surface. A toner image is formed on the surface of the photosensitive drum 132 by supplying toner from the developing device 135 to the photosensitive drum 132 on which the electrostatic latent image is formed, thereby forming a visible image.

  Then, after the toner image formed on the surface of the photosensitive drum 132 is transferred to the recording medium P such as paper by the transfer device 136, the recording medium P on which the toner image is transferred is separated from the photosensitive drum 132, An image is formed by performing a fixing operation by heat and pressure with a fixing device (not shown).

  In such an image forming apparatus, generally, after the toner image is transferred to the recording medium P, the untransferred toner remains on the photosensitive drum. Therefore, a cleaner unit 137 for removing the residual toner is disposed, and the residual toner on the surface of the photosensitive drum 132 is removed by a cleaning blade 137a mounted on the cleaner unit 137 to clean the photosensitive drum 132. Then, after returning to the initial state, the next toner image is formed. By repeating such an operation, it is possible to perform image formation continuously.

  However, since the residual toner collected by the cleaner unit 137 is discarded as waste toner, and the discarded toner is not used for printing, there is a problem that the toner is wasted.

  Thus, as a countermeasure against the above problem, an image forming apparatus has been proposed in which the waste toner collected by the cleaner unit is returned to the developing device and the waste toner is used again for development (see Patent Document 1).

  In Patent Document 1, as a configuration of the developing device, an unnecessary object such as a defective charged toner or a foreign matter contained in the developer while the developer is guided from the developer regulating member to the developing area where the photosensitive drum and the developing roller face each other. It is characterized in that an unnecessary material collecting means for collecting the waste is provided.

  According to this technique, it is possible to realize a developing device that can efficiently collect defective charged toner by providing an unnecessary material collecting unit or arranging a wire to which a voltage is applied in the vicinity of the unnecessary material collecting unit.

The advantage of using waste toner again for development by the above technology is
(1) Since waste toner that was originally discarded is used for development, toner consumption can be reduced, thereby reducing the running cost of the apparatus.
(2) The waste toner once collected in the cleaner unit needs to be collected and discarded in a separate waste toner collection container. However, when the waste toner is returned to the developing tank and used again, the waste toner collection container It becomes unnecessary and the apparatus can be miniaturized.
(3) If waste toner is discarded as it is, problems such as environmental pollution occur, so it is necessary to perform special processing on waste toner and cannot be processed by ordinary users. There is a problem that it takes time and cost. Such problems can be eliminated when the waste toner is returned to the developing tank for use.

JP 2001-142300 A

  However, since the collected waste toner contains foreign matter such as paper dust and filler generated from a recording medium such as paper in addition to the waste toner, this foreign matter is used when the waste toner is returned to the developing device. Will enter the developing device. This foreign matter combines with the toner to generate poorly charged toner with low chargeability or reversely charged toner charged to reverse polarity, thereby causing fogging on the image or attaching foreign matter to the image, resulting in improved image quality. There was a problem of gradually decreasing.

  In the technique of Patent Document 1, when waste toner such as toner remaining on the surface of the photosensitive drum is returned to the developing device or the toner cartridge and used, large black fibrous dots (fogging) are formed on the white background portion of the print sample. There was a problem that it might be printed.

  This “fogging” is because paper dust is positively charged in the transfer section, and the collected residual toner and the positively charged paper dust mix with each other. A foreign material is formed.

  Paper dust and waste toner cluster-like foreign particles are positively charged, and while being developed in the development area, they are transferred from the developing roller to the photosensitive drum by an electric field on the white background of the print sample, and transferred and fixed. It is fixed on the recording medium through the process. Since the size of the cluster-like foreign matter is 100 to 500 (μm), what is fixed on the white background of the paper is in a state that can be confirmed by human eyes.

  The present invention has been made in view of the above-described conventional problems. When the waste toner is recycled and reused, the toner is removed without deteriorating the image quality due to foreign matters contained in the collected waste toner. An object of the present invention is to provide an image forming apparatus that can be used without being wasted.

An image forming apparatus according to the present invention for solving the above-described problems is as follows.
The present invention includes a photosensitive drum on which an electrostatic latent image is formed on the surface, a developing roller that supplies toner to the photosensitive drum, and a developer regulating member that regulates the amount of developer supplied to the developing roller. A developing device that develops an electrostatic latent image formed on the photosensitive drum to form a toner image, and a waste that collects toner remaining on the photosensitive drum after the toner image is transferred to a recording medium. In an image forming apparatus provided with toner recovery means (for example, a cleaner unit) and configured to return the recovered waste toner to the developing device, the developing device is configured to recover foreign matters mixed in the waste toner. The foreign material recovery member includes at least three electrodes, and the electrodes are applied with voltages at different timings between adjacent electrodes. It is.

  In the present invention, the foreign matter includes paper dust.

  In the present invention, the foreign material collecting member is formed in a long plate shape along the axial direction of the developing roller, and the developer is supplied onto the developing roller and the supply amount is regulated by the developer regulating member. It is preferable to provide it in contact with or in proximity to the surface.

  In the present invention, the foreign material recovery member includes a striped electrode pattern in which a plurality of rows of electrodes arranged in order are arranged in parallel along the axis of the developing roller, It is preferable to apply a three-phase or four-phase AC voltage.

  Further, according to the present invention, in the adjacent electrodes, the phase of the AC voltage applied to the electrode close to the developing roller is delayed from the phase of the AC voltage applied to the electrode far from the developing roller. It is preferable to generate a traveling wave electric field.

  In the present invention, it is preferable that the direction in which the foreign substance is conveyed by the traveling wave electric field is a gravitational direction.

  Moreover, it is preferable that this invention is equipped with the foreign material collection | recovery mode which collects a foreign material, and the foreign material conveyance mode which conveys a foreign material as an operation mode which drives the said foreign material collection | recovery member.

  In the present invention, it is preferable that the foreign material conveyance mode operates while the developing roller is stopped.

  In the invention, it is preferable that the developing device includes a collection container for collecting the foreign matter.

  In the present invention, it is preferable that the developer regulating member is provided on the upstream side of the collecting container in the rotation direction of the developing roller.

  According to the image forming apparatus of the present invention, the photosensitive drum on which an electrostatic latent image is formed on the surface, the developing roller that supplies toner to the photosensitive drum, and the amount of developer that is supplied to the developing roller are regulated. A developing device including a developer regulating member that develops an electrostatic latent image formed on the photosensitive drum to form a toner image; and a residual toner image on the photosensitive drum after the toner image is transferred to a recording medium. In the image forming apparatus provided with waste toner collecting means (for example, a cleaner unit) for collecting the collected toner and configured to return the collected waste toner to the developing device, the waste toner is configured as the developing device. A foreign matter collecting member that collects foreign matter mixed in the electrode, and the foreign matter collecting member has at least three electrodes, and a voltage is applied to the electrodes at different timings between adjacent electrodes. It is the foreign material collected member to generate a traveling wave magnetic field can be conveyed recovered and charged foreign matter or foreign matter plus waste toner cluster or the like. As a result, foreign matter adhering to the foreign matter collecting member and foreign matter and waste toner clusters can be cleaned, and thus the foreign matter and foreign matter and waste toner clusters in the developer can be stably removed by the cleaned foreign matter collecting member. Can do. Therefore, when the waste toner is recirculated and reused, the toner can be effectively used without wasteful consumption without deteriorating the image quality due to the foreign matter contained in the collected waste toner.

1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is an explanatory diagram illustrating a configuration for collecting waste toner of the image forming apparatus. FIG. 10 is an explanatory diagram illustrating a modified example of a configuration for collecting the waste toner. FIG. 4 is an explanatory diagram illustrating a configuration of a foreign matter collecting member and an electrode pattern provided in the developing device of the image forming apparatus. It is sectional drawing which shows the structure of the said foreign material collection | recovery member and the said electrode pattern. It is explanatory drawing which shows the connection structure of the edge part of the said electrode pattern. It is sectional drawing which shows the connection structure of the edge part of the said electrode pattern. It is explanatory drawing which shows the state which collects a foreign material from a developing roller with the said foreign material collection member. It is explanatory drawing which shows the timing which applies an electric current to the electrode of the said foreign material collection | recovery member. 6 is a table showing a result of verification in which paper dust collected in the image forming apparatus is conveyed by a foreign matter collecting member. 6 is a graph showing a state of occurrence of “fogging” of an image defect depending on whether or not the foreign material collecting member is cleaned in the image forming apparatus. 6 is a table showing the level of “fogging” depending on the degree of image quality defect in the image forming apparatus. It is explanatory drawing which shows the structure of the foreign material collection | recovery member with which the image development apparatus which concerns on 2nd Embodiment of this invention is equipped, and an electrode pattern. It is explanatory drawing which shows the timing which applies an electric current to the electrode of the said foreign material collection | recovery member. FIG. 10 is an explanatory diagram illustrating timing for applying a current to an electrode of a foreign matter collecting member provided in a developing device of an image forming apparatus according to a third embodiment of the present invention. FIG. 10 is an explanatory diagram illustrating a configuration around a photosensitive drum that performs image formation in a conventional image forming apparatus.

(First embodiment)
Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is an example of an embodiment for carrying out the invention, and is an explanatory diagram showing the overall configuration of the image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a configuration for collecting waste toner of the image forming apparatus. FIG. 3 is an explanatory diagram showing a modification of the configuration for collecting the waste toner.

  In the first embodiment, as shown in FIGS. 1 and 2, a photosensitive drum 32 having an electrostatic latent image formed on the surface, a developing roller 35a for supplying toner to the photosensitive drum 32, and a developing roller 35a. A developer regulating member 35c that regulates the amount of the developer to be developed, develops an electrostatic latent image formed on the photosensitive drum 32 to form a toner image, and transfers the toner image to a recording medium In the image forming apparatus 1 provided with a cleaner unit (waste toner collecting means) 37 for collecting the toner remaining on the subsequent photosensitive drum 32, the collected waste toner is returned to the developing device 35. The configuration of the apparatus 35 includes a foreign matter collecting member 45 that collects foreign matter mixed in the waste toner.

First, the overall configuration of the image forming apparatus 1 will be described.
The image forming apparatus 1 according to the first embodiment has a copier mode (copying mode), a printer mode, and a FAX mode as print modes, and an operation input from an operation unit (not shown) or an external host device such as a personal computer. A print mode corresponding to reception of a print job from is selected by a control unit (not shown).

  As shown in FIG. 1, the image forming apparatus 1 is roughly divided into a document reading unit 10 (document reading unit), a paper feeding unit 20 (paper feeding unit), a printing unit 30 (printing unit), and a paper discharge unit 40. The document reading unit 10 is disposed above the paper feeding unit 20, and the paper discharge unit 40 is disposed at an intermediate portion between the document reading unit 10 and the paper feeding unit 20.

Hereinafter, the copier mode will be described from the above processing modes.
After the user places a document on the platen glass 11 of the document reading unit 10 (scanner unit), the sheet (recording sheet) is placed on the sheet feeding cassette 21 of the sheet feeding unit 20 or an optional sheet feeding tray Xb provided on the side of the apparatus. ) And input the condition input keys (number of prints / printing magnification, etc.) on the operation panel (not shown) arranged on the exterior front of the device, and then operate the start key on the operation panel, copy operation Be started.

  When the start key is operated, a main drive motor (not shown) starts and each drive gear rotates. Thereafter, the paper feed roller 22 or 22 a rotates to feed (feed) the paper into the apparatus, and the fed paper reaches the registration roller 31. The registration roller 31 temporarily stops the paper so as to synchronize with the leading edge (image formation start portion) of the image formed on the photosensitive drum 32, and the leading edge of the paper is uniformly pressed against the registration roller 31. Thus, the leading edge position of the paper is corrected.

  Here, the photosensitive drum 32 is an image carrier on which a toner image is formed, is supported so as to be rotatable around an axis, and has a cylindrical shape, a cylindrical shape, or a thin film sheet shape (preferably a cylindrical shape) (not shown). And a photosensitive layer formed on the surface of the conductive substrate.

  As the photosensitive drum 32, those commonly used in this field can be used. For example, the photosensitive drum 32 includes an aluminum base tube which is a conductive substrate and an organic photosensitive layer which is a photosensitive layer formed on the surface of the aluminum base tube. A photosensitive drum connected to a GND (ground) potential can be used.

  The organic photosensitive layer may be formed by laminating a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material, and includes one charge generation material and a charge transport material. It may be formed by layers. The layer thickness of the organic photosensitive layer is not particularly limited, but is, for example, 20 μm. An underlayer may be provided between the organic photosensitive layer and the conductive substrate. Further, a protective layer may be provided on the surface of the organic photosensitive layer.

  The photosensitive drum 32 is rotated counterclockwise, for example, around the paper surface of FIG. 2 by a photosensitive drum driving gear (not shown) attached to the photosensitive drum 32 engaged with the main driving motor gear. It rotates at a speed of 163 mm / s.

  On the other hand, in the document reading unit 10, the copy lamp 12a (light source) is turned on, and the exposure starts when the copy lamp unit 12 moves in the direction of the arrow. Irradiation light applied to the original by the copy lamp 12a becomes reflected light (reflected light from the original) including image information of the original, and the reflected light is transmitted from the first mirror 12b provided in the copy lamp unit 12 to the second light. Reading is performed by inputting to the CCD 16 from the mirror 13, the third mirror 14, and the optical lens 15.

  The image information read in this manner is converted into an electrical signal by a CCD circuit provided in a control unit (not shown), and the image information signal is subjected to image processing under a set condition. , And sent as print data to the LSU unit 33.

  On the other hand, the rotating photosensitive drum 32 is charged by the charging unit 34 to a predetermined charging potential, for example, −600 V in this embodiment. The charging unit 34 uses a saw-tooth charger in the first embodiment, but a roller charger, a brush-type charger, a charger-type charger, or the like can also be used.

  Laser light from the LSU unit 33 is irradiated to the photosensitive drum 32 through a polygon mirror and various lenses (not shown), and an electrostatic latent image is formed on the photosensitive drum 32. In the case of the first embodiment, the potential of the part exposed according to this image information is −70V.

  The electrostatic latent image formed on the above-described photosensitive drum 32 is visualized with a developer containing toner and a carrier by the developing device 35 to form a toner image.

  As shown in FIG. 2, the developing device 35 is a developing unit provided facing the photosensitive drum 32, and the developing roller 35 a is provided rotatably on a rotation axis parallel to the rotation axis of the photosensitive drum 32. As shown in FIG. 3, the rotation direction is counterclockwise toward the paper surface.

  The developing roller 35a is a mag roller formed by arranging magnet members having different polarities approximately alternately in the circumferential direction. The developing roller 35a adsorbs the developer contained in the developing tank 35b by its magnetic force, and the adsorbed developer is regulated to a predetermined thickness by the developer regulating member 35c, and the developing roller 35a and the photoconductor The drum 32 is conveyed to the adjacent developing nip portion.

  A voltage is applied to the developing roller 35a by a high-voltage power supply (not shown). In the case of the first embodiment, the voltage is applied in the range of −450 (V) to −550 (V) V. The electrostatic latent image formed on the surface of the body drum 32 is visualized (developed) with toner at the development nip portion.

  However, during rotation before and after the process of visualizing, the bias applied to the developing roller 35a is about +50 (V). This is because if the portion where the photosensitive drum 32 is not charged by the charging unit 34 overlaps the above-described nip portion, the toner is transferred to the photosensitive drum 32 and is wasted if the same voltage as that for visualizing is applied. This is to prevent excessive toner consumption.

The developing tank 35b is a hollow container-like member made of, for example, a hard synthetic resin.
A two-component developer containing toner and carrier is accommodated in the developing tank 35b.
In addition to the developing roller 35a and the developer regulating member 35c, the developing tank 35b includes a stirring roller 35d, a toner concentration sensor 35e, a toner guide roller 35f, a foreign matter collecting member 45, and a foreign matter collecting container (collecting container) 46. Has been placed. Further, a toner hopper 43 for replenishing toner is connected to the developing tank 35b.

  The developer regulating member 35c is a thin plate member made of a stainless steel thin plate or the like, and is arranged in a cantilever manner on the inner wall of the developing tank 35b. The free end of the developer regulating member 35c is disposed with a predetermined interval with respect to the peripheral surface of the developing roller 35a.

  The stirring roller 35d is rotatably provided on a rotation shaft parallel to the rotation shaft of the developing roller 35a. The agitating roller 35d agitates the toner and carrier in the developing tank 35b and supplies the agitated toner and carrier to the developing roller 35a.

  The toner density sensor 35e is disposed at the bottom of the developing tank 35b so as to be close to the stirring roller 35d. The toner concentration sensor 35e is a magnetic permeability sensor that detects the toner concentration in the developing tank 35b. The toner is consumed by the development process, and the toner concentration in the developing tank 35b is lowered. According to the value of the toner density sensor 35e, the toner supply from the toner hopper 43 to the developing tank 35b is started / stopped.

  In the first embodiment, the mixing ratio of the toner and the carrier is 5:95 by weight, but is not particularly limited to this value, and may be appropriately selected according to the types of the toner and the carrier.

  The toner hopper 43 is connected to the developing tank 35b and is provided with an opening 35g for supplying toner to the developing tank 35b. A toner supply roller 43a is arranged at a position covering the upper side of the opening 35g.

  The toner replenishing roller 43a is constituted by a sponge roller, and replenishes toner to the developing tank 35b by squeezing off the internal toner at the edge of the opening after the bubble portion contains toner.

  Further, the toner hopper 43 includes a supply roller 43b that supplies toner to the toner replenishing roller 43a, and a stirring blade member 43c that stirs and conveys the toner stored in the toner hopper 43.

  In the developing device 35, the toner replenished from the toner hopper 43 is conveyed to the stirring roller 35d by the toner guide roller 35f, mixed with the developer in the developing tank 35b, and used for development.

  The developer used in the first embodiment is a so-called two-component developer including toner and carrier, but may be a one-component developer including only toner.

  The toner used in the first embodiment is composed of toner particles containing a binder resin, a colorant, and a release agent. As the binder resin, those commonly used in this field can be used. For example, polystyrene, a homopolymer of a substituted styrene, a styrene copolymer, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, Examples include polyurethane. Binder resin can be used individually by 1 type, or can use 2 or more types together.

  As the colorant, pigments for toners and dyes conventionally used in electrophotographic image forming techniques can be used. Examples of the toner pigment include carbon black and titanium oxide. Toner pigments can be used alone or in combination of two or more.

  As the release agent, for example, wax can be used. As the wax, those commonly used in this field can be used, and examples thereof include polyethylene wax, polypropylene wax, and paraffin wax.

  In addition to the binder resin, the colorant, and the release agent, the toner contains one or more of general toner additives such as a charge control agent, a fluidity improver, a fixing accelerator, and a conductive agent. May be. The toner can be produced by a known method such as a pulverization method, a suspension polymerization method, or an emulsion aggregation method.

  In the pulverization method, a toner is obtained by melting and kneading a colorant, a release agent, and the like with a binder resin. In the suspension polymerization method, monomers such as a binder resin, a colorant, and a release agent are uniformly dispersed, and then these monomers are polymerized to obtain a toner. In the emulsion aggregation method, a toner is obtained by aggregating a binder resin, a colorant, a release agent, and the like with an aggregating agent, and heating fine particles of the obtained aggregate.

  In the present invention, the volume average particle diameter of the toner is not particularly limited, and is preferably 2 (μm) or more and 7 (μm) or less. Further, when the volume average particle diameter of the toner is appropriately small as described above, the coverage with respect to the recording medium becomes high, so that high image quality with a low adhesion amount and reduction in toner consumption can be achieved.

  When the volume average particle diameter of the toner is less than 2 (μm), the fluidity of the toner is lowered, and during the developing operation, the supply, stirring and charging of the toner become insufficient, so that the toner is supplied to the photosensitive drum 32. A shortage of toner or an increase in reverse polarity toner may occur, and a high-quality image may not be obtained. Further, when the volume average particle diameter of the toner exceeds 7 (μm), toner particles having a large particle diameter that is difficult to soften to the central portion at the time of fixing increase, so that the fixability of the toner image on the recording medium is deteriorated. The color of the image deteriorates, and the image becomes dark particularly when fixing to an OHP sheet.

The toner used in the image forming apparatus 1 of the first embodiment has a glass transition point of 60 (° C.), a softening point of 120 (° C.), and a negative charging property having a volume average particle size of 6 (μm). Insulating non-magnetic toner. A toner amount of 5 (g / m ² ) is required on the surface of the recording medium in order to obtain an image density having a reflection density measurement value of 1.4 by X-Rite 310 using this toner.

  In addition, the toner contains polyester having a glass transition point of 60 (° C.) and a softening point of 120 (° C.) as a binder resin, and contains 12% by weight of a pigment of each color as a colorant, as a release agent. A low molecular weight polyethylene wax having a glass transition point of 50 (° C.) and a softening point of 70 (° C.) is contained by 7% by weight of the total amount of toner. The low molecular weight polyethylene wax used as a release agent for this toner is a wax having a lower glass transition point and softening point than polyester used as a binder resin.

  As the carrier, magnetic particles can be used. Examples of the magnetic particles include metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum or lead. Among these, ferrite is preferable.

  Further, a resin-coated carrier in which magnetic particles are coated with a resin, or a resin-dispersed carrier in which magnetic particles are dispersed in a resin may be used as the carrier.

  In the present invention, the resin that coats the magnetic particles is not particularly limited, and examples thereof include olefin resins, styrene resins, styrene acrylic resins, silicone resins, ester resins, and fluorine-containing polymer resins. Is mentioned. The resin used for the resin-dispersed carrier is not particularly limited, and examples thereof include styrene acrylic resin, polyester resin, fluorine-based resin, and phenol resin.

In the present invention, the volume average particle diameter of the carrier is not particularly limited, and is preferably 30 (μm) or more and 50 (μm) or less in consideration of high image quality. Furthermore, the resistivity of the carrier is preferably 10 ⁸ (Ω · cm) or more, and more preferably 10 ¹² (Ω · cm) or more.

The carrier resistivity is determined by placing the carrier in a container having a cross-sectional area of 0.50 (cm ² ), tapping, then applying a load of 1 (kg / cm ² ) to the carrier packed in the container, This is a value obtained by reading a current value when a voltage generating an electric field of 1000 V / cm is applied between the weight and the bottom electrode. If the carrier resistivity is low, charges are injected into the carrier when a bias voltage is applied to the developing roller 35 a, and carrier particles are likely to adhere to the photosensitive drum 32. Further, breakdown of the bias voltage is likely to occur.

  The magnetization strength (maximum magnetization) of the carrier is preferably 10 (emu / g) or more and 60 (emu / g) or less, more preferably 15 (emu / g) or more and 40 (emu / g) or less.

The magnetization strength depends on the magnetic flux density of the developing roller 35a, but under the general magnetic flux density conditions of the developing roller 35a, if it is less than 10 (emu / g), the magnetic binding force does not work. May cause carrier scattering.
On the other hand, if the magnetization strength exceeds 60 (emu / g), it is difficult to maintain the non-contact state with the photosensitive drum 32 in the non-contact development in which the carrier spikes become too high. Further, in the contact development, there is a risk that a sweep is likely to appear in the toner image.
The shape of the carrier is preferably a spherical shape or a flat shape.

  Next, image forming processing in the copier mode in the image forming apparatus 1 of the first embodiment will be described.

  In the printing unit 30 of the image forming apparatus 1, the toner image developed on the photosensitive drum 32 is transferred onto the recording medium conveyed by the registration roller 31 in the transfer unit where the transfer unit 36 and the photosensitive drum 32 are close to each other. Is transcribed.

  As shown in FIG. 1, in the transfer unit 36, the toner image formed on the photosensitive drum 32 is transferred to the recording medium by applying a high voltage opposite to the toner charging polarity to the wire corona charger. The The recording medium to which the toner image is transferred is conveyed to the fixing unit 38.

  The recording medium on which the toner has been transferred passes through the upper heat roller 38a and the lower heat roller 38b of the fixing unit 38 (fixing step), and heat and pressure are applied, so that the unfixed toner on the recording medium is applied to the recording medium. After being melted and fixed, the paper is discharged onto a paper discharge tray 42 by a paper discharge roller 41 constituting the paper discharge device X.

  When a predetermined sensor detects that a document is placed on the document tray Xa of the ADF 10a (automatic document feeder) included in the document reading unit 10, the document is automatically supplied by the ADF 10a. Copy is executed.

  That is, in the ADF 10a, when the start key operation is performed, the document feeding roller 17 rotates, and the document placed on the document tray Xa is sent into the document reading unit 10 and conveyed on a predetermined conveyance path. On the other hand, the document being conveyed is exposed while the copy lamp unit 12 is stopped at a predetermined stop position. A process of reading an original image by reflected light from the original obtained by this exposure is executed. In this way, the document whose image has been read is discharged to the document discharge unit 18.

  Untransferred toner that has not been transferred to the recording medium adheres to the photosensitive drum 32 after transfer. Further, when the recording medium is paper, the paper dust adhering to the surface of the paper is positively charged during transfer and adheres to the photosensitive drum 32. As shown in FIG. 2, the transfer residual toner and paper dust are scraped off by a cleaning blade 37 a attached to the cleaner unit 37 and are collected as waste toner in the cleaner unit 37.

  As shown in FIG. 2, the waste toner collected by the cleaner unit 37 is conveyed by a screw roller 37 b mounted inside the cleaner unit 37 and is conveyed to the end of the cleaner unit 37. An opening 37c is provided at the end of the cleaner unit 37, and the cleaning unit 37 is sent to a waste toner transport pipe 44 having one end connected to the opening 37c.

  The other end of the waste toner conveying pipe 44 is connected to an opening 44 a provided in the developing device 35. A waste toner conveyance screw 44 b is provided inside the waste toner conveyance pipe 44.

  Waste toner is transported by the waste toner transport screw 44b and mixed into the developing tank 35b through the opening 44a. The mixed waste toner is mixed with the developer accommodated in the developing tank 35b by the stirring roller 35d, sent to the developing roller 35a, and used again for development.

  In the first embodiment, as shown in FIG. 2, the waste toner is returned to the developing tank 35b of the developing device 35. However, the waste toner is not returned to the developing tank 35b, and as shown in FIG. You may make it return to. That is, the waste toner may be mixed into the new toner through the opening 144 a provided in the toner hopper 43 by the waste toner transport pipe 144.

Next, a characteristic configuration of the developing device 35 according to the first embodiment will be described with reference to the drawings.
FIG. 4 is an explanatory view showing the configuration of the foreign matter collection member and the electrode pattern provided in the developing device of the image forming apparatus of the first embodiment, FIG. 5 is a cross-sectional view showing the configuration of the foreign matter collection member and the electrode pattern, and FIG. FIG. 7 is a cross-sectional view showing the connection structure at the end of the electrode pattern, FIG. 8 is a view showing a state in which foreign matter is collected from the developing roller by the foreign matter collecting member. FIG. 9 and FIG. 9 are explanatory views showing the timing of applying a current to the electrode of the foreign material recovery member.

  As shown in FIG. 3, the developing device 35 includes a foreign matter collection member 45 and a foreign matter collection container 46.

First, the foreign material recovery member 45 will be described.
As shown in FIG. 5, the foreign material recovery member 45 is a plate-like FPC (flexible printed circuit board), and as shown in FIG. 5, a PI (polyimide) base material 451 having a thickness of 25 (μm), An adhesive layer 452 in which 18 (μm) thick copper is patterned on both surfaces is formed, and PI of 12.5 (μm) thick as an epoxy-based thermosetting resin (thickness of about 25) is formed as a coverlay 453 on the copper. The two-layer type FPC bonded with (μm) is used.

As shown in FIG. 4, the electrode pattern DP1 is a striped electrode pattern in which a plurality of electrodes are arranged in parallel along the axis of the developing roller 35a, and are all formed on the same surface.
As shown in FIG. 5, the electrode pattern DP1 has an electrode width W of 128 (μm), an array pitch P of 254 (μm), and four different electrodes are formed, each having eight different electrodes for a total of 32 electrodes. Are arranged in order. Note that FIG. 4 is shown in a simplified manner so that the number of electrodes shown in the figure is reduced and the configuration of the electrode pattern is easy to understand.

  When the four electrodes are the first electrode D1, the second electrode D2, the third electrode D3, and the fourth electrode D4, and the FPC on which the electrode pattern DP1 is formed is attached to the developing device 35, the one closer to the developing roller 35a The first electrode D1, the second electrode D2, the third electrode D3, and the fourth electrode D4 are repeated, and the next of the fourth electrode D4 is repeated in the order of the first electrode D1, the first electrode D2,.

  The electrodes of the same type (symbol) are conductive at both ends, and are patterned so that the respective electrode terminals (DT1, DT2, DT3, DT4) are also conductive. The four electrodes (D1, D2, D3, D4) are connected to a high-voltage power supply (not shown), and can generate traveling waves by applying different AC voltages.

  As shown in FIG. 6, both ends are subjected to through-hole processing (reference numeral D10) so that the first electrode D1 and the third electrode D3 (the other end are the second electrode D2 and the fourth electrode D4) do not contact each other. To. That is, as shown in FIG. 7, through-hole processing is performed so as to connect to the copper on the opposite side at the end of the striped pattern of the third electrode D3. In the same manner, the third electrodes D3 having a total of eight striped patterns are connected by performing through-hole processing, and again connected to copper on the same side as the striped pattern by through-hole processing, and patterned to electrode terminals. Note that FIG. 6 is shown in a simplified manner so that the configuration of the electrode pattern can be easily understood by reducing the number of electrodes shown in the figure as in FIG.

Next, the foreign material collection container 46 will be described.
As shown in FIG. 8, the foreign matter collection container 46 includes a collection unit 46 a that can contain foreign matters such as paper dust. A developer restricting member (layer thickness restricting member) 35c is disposed on the upstream side in the developing roller rotation direction of the foreign matter collecting container 46, and a foreign matter collecting member 45 is disposed on the downstream side in the developing roller rotating direction.

The foreign material collecting member 45 is attached so that the first electrode D1 is closest to the developing roller 35a.

  On the surface of the developing roller 35a, a magnetic brush with spikes formed by the carrier 50 and the toner 60 is formed as shown in FIG. Since the magnetic brush that has passed through the developer regulating member 35c is uniformly leveled, the distance from the foreign material collecting member 45 is stabilized, and the paper dust 70 mixed in the developer can be efficiently collected.

  As an operation mode for operating the foreign material recovery member 45, a control unit (not shown) has a foreign material recovery mode for recovering foreign material and a foreign material transfer mode (cleaning mode) for transporting foreign material, which can be operated by switching each mode. It is configured.

  In the first embodiment, when the image forming apparatus 1 is printing, the mode is switched to the foreign matter collecting mode, a DC power source (not shown) is connected to the foreign matter collecting member 45, and all the electrodes of the foreign matter collecting member 45 are connected to, for example, the developing roller 35a. When -450 (V) is applied to DC, a DC voltage of -840 (V) is applied to collect paper dust.

  At this time, the foreign matter collecting member 45 is arranged so that the tip thereof touches or comes close to the tip of the head of the magnetic brush of the developing roller 35a. This is because the closer the foreign material collecting member 45 is to the developing roller 35a, the larger the amplitude of the oscillating electric field is, and the easier it is to collect paper dust. This is because the necessary amount of developer cannot be carried to the developing nip portion where the developing roller 35a and the photosensitive drum 32 are close to each other, which causes image deterioration.

  On the other hand, when the image forming apparatus 1 is on standby, that is, when the developing roller 35a is stopped, the mode is switched to the foreign material transport mode, and the first electrode D1 to the fourth electrode D4 of the foreign material recovery member 45 are switched from an AC power source (not shown). The foreign matter collecting member 45 is cleaned by applying an alternating voltage at different timings to generate a traveling wave electric field and conveying paper dust.

  In order to generate a traveling wave electric field in the foreign material collecting member 45, as shown in FIG. 9, the phase of the alternating voltage applied to the electrode near the developing roller 35a is different from the developing roller 35a in the adjacent electrode in the foreign material collecting member 45. An AC voltage is applied so as to be delayed from the phase of the AC voltage applied to the far electrode.

  The four waveforms applied from the first electrode D1 to the fourth electrode D4 are all the same waveform, frequency, Vpp, and duty, and differ only in phase. That is, the AC voltage applied to the second electrode D2 has a phase that is π / 2 (rad) higher than the AC voltage applied to the first electrode D1, and the AC voltage applied to the third electrode D3 and the fourth electrode D4 is also the first voltage. A four-phase AC voltage advanced by π (rad) and 3π / 2 (rad), respectively, compared to the AC voltage applied to one electrode D1 is applied.

  In FIG. 9, reference numeral T1 denotes a timing position at which the polarity of the first electrode D1 changes, and T2 denotes a timing position at which the polarity of the second electrode D2 changes with reference to the timing position T1 of the first electrode D1. T3 is a timing position where the polarity of the third electrode D3 changes with reference to the timing position T1 of the first electrode D1, and T4 is a polarity change of the fourth electrode D4 with respect to the timing position T1 of the first electrode D1. Indicates the timing position.

  Thus, by shifting the timing at which the polarity of the fourth electrode D4 changes from the first electrode D1, the charged particles are moved between the adjacent electrodes in the direction from the first electrode D1 to the fourth electrode D4 each time the polarity of the voltage changes. An electric field to be moved, that is, a traveling wave electric field can be generated.

  As shown in FIG. 8, the paper dust 70 collected by the foreign material collecting member 45 is conveyed in the direction from the first electrode D1 to the fourth electrode D4 by the traveling wave electric field. The paper powder 70 thus transported is transported to the foreign matter collection container 46. At this time, if the transport direction is the weight direction (the downward direction in the figure), the paper powder 70 can be easily transported to the foreign matter collection container 46 using gravity.

  In this way, the collected paper dust 70 can be removed from the foreign material collection member 45 and cleaned by the foreign material conveyance mode.

Next, a description will be given of the result of verification for conveying the paper dust 70 collected by the foreign matter collecting member 45 in the image forming apparatus 1 of the first embodiment.
FIG. 10 is a table showing a result of verification in which the paper dust collected in the image forming apparatus of the first embodiment is conveyed by the foreign material collecting member.

  In this verification, in the image forming apparatus 1, the voltage (Vpp) is set under the condition that the waveform of the current applied to each electrode (D 1, D 2, D 3, D 4) of the foreign matter collecting member 45 is a rectangular wave and duty 50 (%). ) And change the frequency to verify the conveyance of paper dust. If the paper powder can be conveyed, “○” is indicated. If the paper powder cannot be conveyed, “X” is indicated.

  According to the foreign matter collecting member 45 of the image forming apparatus 1 of the first embodiment, as shown in the table of FIG. 10, when the voltage (Vpp) is 300 (V) or 400 (V), the frequency is 100 (Hz). ), 300 (Hz), and 500 (Hz), a lump of paper dust 70 remained. On the other hand, when the voltage (Vpp) was 500 (V), 600 (V), or 750 (V), the paper dust moved at frequencies of 100 (Hz), 300 (Hz), and 500 (Hz).

  As a result of the verification, according to the foreign material recovery member 45, it has been found that the voltage (Vpp) is 500 (V) or higher and the frequency is 100 to 500 (Hz).

Next, a description will be given of a result of aging performed on the image forming apparatus 1 based on the above-described operating condition of the foreign material collecting member 45 and verifying the cleaning effect of the foreign material collecting member 45.
FIG. 11 is a graph showing an occurrence state of “fogging” of an image defect depending on whether or not the foreign matter collecting member is cleaned in the image forming apparatus of the first embodiment, and FIG. It is a table | surface which shows the level of "fog".

  In the aging of the image forming apparatus 1 in this verification, a document having a printing rate of 5% is copied, and the fogging level is checked every predetermined number of sheets.

The measurement of fog level is as follows.
The original is replaced with a sheet having a circle with a radius of 2 (cm) printed in the center, and the original is set on the original table of the machine and copied. Next, the output sample is placed at a distance of 40 (cm), and a circle with a radius of 2 (cm) is visually observed to count the number of large crushing stains present in the circle.
Using the correspondence table shown in FIG. 12, the fogging level of the sample was obtained from the number of crushed dirt, and the fogging level of 3.0 or less was accepted.

  Further, the surface of the foreign material collecting member 45 was not cleaned up to 35,000 sheets, and the surface of the foreign material collecting member 45 was cleaned every 500 sheets after 35,000 sheets, and a total of 100,000 sheets were printed.

  As a result of aging performed by the image forming apparatus 1 under the above conditions, when the cleaning is not performed, the fogging level is acceptable up to around the initial 10,000 sheets, but the level exceeding 10,000 sheets is exceeded. The fogging level exceeded 3.0, and aging was performed without cleaning up to 35,000 sheets, but generally good print samples could not be obtained.

  On the other hand, when cleaning is performed from 35,000 sheets, as shown in FIG. 11, the fog level is drastically improved by the first cleaning, and after that, by performing cleaning every 500 sheets, the fog level is set to the pass level. Thus, the cleaning effect of the foreign matter collecting member 45 could be verified.

  As described above, according to the first embodiment, the photosensitive drum 32, the developing roller 35a that supplies toner to the photosensitive drum 32, and the developing device 35 that includes the developer regulating member 35c, and the toner image In the image forming apparatus 1, which includes a cleaner unit 37 that collects toner remaining on the photosensitive drum 32 after being transferred to the recording medium, the collected waste toner is returned to the developing device 35. The foreign matter collecting member 45 for collecting foreign matter mixed in the waste toner is provided, and the foreign matter collecting member 45 is provided with four electrodes (D1, D2, D3, D4), and the electrodes (D1, D2, D3, D3). In D4), since the voltages are applied at different timings between adjacent electrodes, a traveling wave electric field is generated in the foreign matter collecting member 45 to convey the charged foreign matter and collect the foreign matter. By cleaning the timber 45, it is possible to stably remove foreign matter in the developer. As a result, when the waste toner is recycled and reused, it can be used effectively without wasteful consumption of the toner without deteriorating the image quality due to the foreign matter contained in the collected waste toner.

  Further, according to the first embodiment, the paper dust 70 mixed in the waste toner is removed as the foreign matter to be removed, so that the main factor causing the image defect can be removed.

  Further, according to the first embodiment, the foreign matter collecting member 45 is formed in a long plate shape along the axial direction of the developing roller 35a, and contacts the surface of the developer whose supply amount is regulated by the developer regulating member 35c. Alternatively, the paper powder 70 can be efficiently collected by the traveling wave electric field by forming the striped electrode pattern DP1 provided close to each other and arranging a plurality of electrodes in parallel along the axis of the developing roller 35a.

  Further, according to the first embodiment, the developing device 35 includes the foreign matter collection container 46 that collects foreign matter, so that the paper powder 70 conveyed by the foreign matter collection member 45 can be temporarily stored in one place. Therefore, the foreign material collecting member 45 can be operated efficiently.

(Second Embodiment)
Next, a second embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 13 is an explanatory view showing the configuration of the foreign matter collecting member and the electrode pattern provided in the developing device of the image forming apparatus according to the second embodiment of the present invention, and FIG. 14 shows the timing of applying a current to the electrode of the foreign matter collecting member. It is explanatory drawing.
The image forming apparatus according to the second embodiment has the same configuration and functions as the image forming apparatus 1 according to the first embodiment except for the configuration of the foreign matter collecting member of the developing device, and the configuration is the same. Components are denoted by the same reference numerals and description thereof is omitted.

As shown in FIG. 13, the foreign material collection member 145 according to the second embodiment has a striped electrode pattern DP100 formed in the same manner as the foreign material collection member 45 of the first embodiment.
In the electrode pattern DP100, an electrode width W is set to 128 (μm), an arrangement pitch P is set to 254 (μm), and 10 different electrodes are formed in each of 10 to arrange 30 electrodes in order. . Note that FIG. 13 is shown in a simplified manner so that the number of electrodes shown in the figure is reduced and the configuration of the electrode pattern is easy to understand.

  When the three electrodes are the first electrode D11, the second electrode D12, and the third electrode D13, and the electrode pattern DP100 is formed and attached to the developing device 35, the first electrode D11, the second electrode in order from the side closer to the developing roller 35a. The electrode D12 and the third electrode D13 are used, and after the third electrode D13, the first electrode D11, the first electrode D12,.

  As shown in FIG. 13, the three waveforms applied from the first electrode D11 to the third electrode D13 are all the same waveform, frequency, Vpp, and duty, and only the phase is different. That is, the phase of the AC voltage applied to the second electrode D12 is advanced by 2π / 3 (rad) from the AC voltage applied to the first electrode D11, and the AC voltage applied to the third electrode D13 is also applied to the first electrode D11. Compared to the alternating voltage to be applied, a three-phase alternating voltage advanced by 4π / 3 (rad) is applied.

  In FIG. 13, T11 is a timing position at which the polarity of the first electrode D11 changes, and T12 is a timing position at which the polarity of the second electrode D12 changes with reference to the timing position T11 of the first electrode D11. T13 indicates the timing position at which the polarity of the third electrode D13 changes with reference to the timing position T11 of the first electrode D11.

  Since it comprised as mentioned above, according to 2nd Embodiment, the polarity of a voltage changes like 1st Embodiment by shifting the timing to which the polarity of the 3rd electrode D13 changes from the 1st electrode D11. A traveling wave electric field that moves charged particles in the direction from the first electrode D11 to the third electrode D13 between adjacent electrodes can be generated every time. Then, the paper dust 70 collected by the foreign material collecting member 145 is conveyed from the first electrode D11 to the third electrode D13 by the traveling wave electric field, and the foreign material collecting member 145 can be cleaned.

  By cleaning the foreign material collecting member 145, the foreign material in the developer can be stably removed. As a result, when the waste toner is recycled and reused, it can be used effectively without wasteful consumption of the toner without deteriorating the image quality due to the foreign matter contained in the collected waste toner.

(Third embodiment)
Next, a third embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 15 is an explanatory diagram showing the timing of applying a current to the electrode of the foreign material collecting member provided in the developing device of the image forming apparatus according to the third embodiment of the present invention.
The image forming apparatus according to the third embodiment has the same configuration and function as the image forming apparatus 1 according to the first embodiment except for the configuration of the foreign matter collecting member of the developing device, and the configuration is the same. Components are denoted by the same reference numerals and description thereof is omitted.

  In the third embodiment, the four current waveforms applied from the first electrode D1 to the fourth electrode D4 in the foreign matter collecting member 45 of the first embodiment are rectangular waves, as shown in FIG. All have the same sine wave.

  As in the first embodiment, adjacent electrodes apply voltages at different timings, and the AC voltage applied to the second electrode D2 is π than the AC voltage applied to the first electrode D1. The phase advances by / 2 (rad), and the AC voltage applied to the third electrode D3 and the fourth electrode D4 is also π (rad) and 3π / 2 (rad), respectively, compared to the AC voltage applied to the first electrode D1. Apply a four-phase AC voltage advanced only by.

  In FIG. 15, T21 is a timing position at which the polarity of the first electrode D1 changes, and T22 is a timing position at which the polarity of the second electrode D2 changes with reference to the timing position T21 of the first electrode D1. T23 is a timing position where the polarity of the third electrode D3 changes with reference to the timing position T21 of the first electrode D1, and T24 is a polarity change of the fourth electrode D4 with respect to the timing position T21 of the first electrode D1. Indicates the timing position.

  Since it was configured as described above, according to the third embodiment, even if the waveforms of the four currents applied from the first electrode D1 to the fourth electrode D4 are sine waves, as in the first embodiment, A traveling wave that moves the charged particles in the direction from the first electrode D1 to the fourth electrode D4 between adjacent electrodes every time the polarity of the voltage changes by shifting the timing at which the polarity of the first electrode D1 changes to the fourth electrode D4. An electric field can be generated. Then, the paper dust 70 collected by the foreign material collecting member 45 is conveyed in the direction from the first electrode D1 to the fourth electrode D4 by the traveling wave electric field, and the foreign material collecting member 45 can be cleaned.

  Then, by cleaning the foreign material collecting member 45, the foreign material in the developer can be stably removed. As a result, when the waste toner is recycled and reused, it can be used effectively without wasteful consumption of the toner without deteriorating the image quality due to the foreign matter contained in the collected waste toner.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. .

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 32 Photosensitive drum 35 Developing apparatus 35a Developing roller 35c Developer control member 37 Cleaner unit (waste toner collecting means)
44,144 Waste toner conveying pipe 45,145 Foreign matter collecting member 46 Foreign matter collecting container (collecting container)
50 Carrier 60 Toner 70 Paper dust D1, D11 First electrode D2, D12 Second electrode D3, D13 Third electrode D4 Fourth electrode DP1, DP100 Electrode pattern

Claims (10)

A photosensitive drum having an electrostatic latent image formed on the surface; a developing roller that supplies toner to the photosensitive drum; and a developer regulating member that regulates an amount of the developer supplied to the developing roller. A developing device that develops an electrostatic latent image formed on the drum to form a toner image, and waste toner collecting means that collects toner remaining on the photosensitive drum after the toner image is transferred to a recording medium; An image forming apparatus configured to return the collected waste toner to the developing device;
The developing device includes a foreign matter collecting member that collects foreign matter mixed in the waste toner,
The foreign material recovery member has at least three or more electrodes,
The image forming apparatus, wherein the electrodes apply voltages at different timings between adjacent electrodes.   The image forming apparatus according to claim 1, wherein the foreign matter includes paper dust.   The foreign matter collecting member is formed in a long plate shape along the axial direction of the developing roller, and is in contact with or close to the surface of the developer that is supplied onto the developing roller and whose supply amount is regulated by the developer regulating member. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided. The foreign matter collecting member includes a striped electrode pattern in which a plurality of rows of electrodes arranged in order are arranged in parallel along the axis of the developing roller,
The image forming apparatus according to claim 1, wherein a three-phase or four-phase AC voltage is applied to the electrode.   A traveling wave electric field is generated by setting the phase of the AC voltage applied to the electrode close to the developing roller in the adjacent electrode delayed from the phase of the AC voltage applied to the electrode far from the developing roller. The image forming apparatus according to claim 4, wherein:   The image forming apparatus according to claim 5, wherein a direction in which the foreign matter is conveyed by the traveling wave electric field is a gravity direction.   7. The operation mode for operating the foreign material recovery member includes a foreign material recovery mode for recovering foreign material and a foreign material transfer mode for transferring foreign material. Image forming apparatus.   The image forming apparatus according to claim 7, wherein the foreign material conveyance mode operates while the developing roller is stopped.   The image forming apparatus according to claim 1, wherein the developing device includes a collection container that collects the foreign matter.   The image forming apparatus according to claim 9, wherein the developer regulating member is provided on the upstream side of the collection container in the rotation direction of the developing roller.

Images