JP2008070751A - Developing device, process unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hopping development type image forming apparatus capable of restraining the occurrence of surface staining further than in the conventional manner. <P>SOLUTION: In the image forming apparatus, toner is conveyed in the arranging direction of a plurality of conveying electrodes while making the toner hop on the surface of the toner conveying substrate 1 by traveling electric field formed by applying pulse voltage to the plurality of conveying electrodes of the toner conveying substrate 1, and the toner being conveyed is stuck to a latent image on a photoreceptor 25 in a developing area Ar2 where the toner conveying substrate 1 and the photoreceptor 25 are opposed to each other, so that the latent image is developed. The apparatus is provided with a pre-development toner collecting means for collecting reversely electrified toner particles and high electrified amount toner particles included in the toner conveyed on the surface of the toner conveying substrate 1 from the substrate in a pre-development conveying area Ar1 on a more upstream side in a toner conveying direction than the developing area Ar2. Thus, intruding amount of the reversely electrified toner particles and the high electrified amount toner particles which are the cause of the surface staining in the developing area Ar2 is reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device for developing a latent image by attaching toner hopping on the surface of an electrode array mounting member having a plurality of electrodes arranged in a predetermined direction to a latent image on a latent image carrier. is there. The present invention also relates to a process unit and an image forming apparatus using such a developing device.

  Conventionally, as image forming apparatuses such as a copying machine, a facsimile, and a printer, those described in Patent Document 1 and Patent Document 2 are known. In these image forming apparatuses, toner carried on a developer carrying member such as a developing roller that moves on the surface is conveyed to a developing region that is a region facing the latent image carrying member as the surface moves. In the developing area, the toner on the developing carrier is electrostatically moved by the potential difference between the surface of the developer carrier and the electrostatic latent image on the latent image carrier to perform development. In such a configuration, the above-described potential difference must be relatively large. This is because the toner must be given a force sufficient to overcome the adhesion force with the developer carrier due to van der Waals force or mirror image force. In addition, so-called background contamination that causes toner particles to adhere to the background portion of the latent image carrier may occur. This background stain is generated when the reversely charged toner particles that are charged in the opposite polarity to the normal charged polarity contained in the toner adhere to the background portion of the latent image carrier.

  On the other hand, as an image forming apparatus, as described in Patent Document 3, an apparatus that develops a latent image on a latent image carrier with toner hopped on the surface of an electrode array mounting member is also known. The developing device of this image forming apparatus has a toner transport substrate having a plurality of transport electrodes arranged in a predetermined direction, and applies toner pulses by applying pulse voltages that are out of phase with each other to adjacent transport electrodes. A traveling electric field is formed on the surface of the transport substrate. Then, the toner supplied on the toner transporting and transporting substrate by the toner supplying means is transported in the direction in which the transporting electrodes are arranged while being hopped on the surface of the substrate by the traveling electric field, and sent to the developing region facing the latent image carrier. With such a configuration, it is possible to realize low-potential development in which the potential difference is significantly reduced as compared with a method in which development is performed using toner carried on a developer carrying member (hereinafter referred to as a carried toner development method). For example, toner can be selectively attached to an electrostatic latent image having a potential difference of only a few tens [V] from the surrounding background portion.

JP-A-9-197781 JP-A-9-329947 JP 2002-351218 A

  However, even in the image forming apparatus having such a configuration, the reversely charged toner particles hopped on the toner transport substrate may adhere to the latent image carrier to cause background staining. Furthermore, unlike the image forming apparatuses described in Patent Document 1 and Patent Document 2, high charge amount toner particles contained in the toner also cause background staining. Specifically, in the developing region where the latent image carrier and the toner transport substrate face each other, the toner particles hopped from the surface of the toner transport substrate eventually reach the vicinity of the latent image carrier. Under the toner particles, a toner cloud is formed by countless toner particles hopping from the substrate surface back and forth. The toner particles that have reached the vicinity of the latent image carrier are repelled by the charges of countless toner particles in the toner cloud and are pushed toward the latent image carrier. Of the infinite number of toner particles contained in the toner, the majority of the toner particles having an average charge amount are pushed from the toner cloud when they reach the vicinity of the background portion of the latent image carrier. However, it cannot overcome the repulsive electric field caused by the background. For this reason, it begins to descend toward the substrate surface without adhering to the background portion. However, high-charge toner particles that are charged to the normal polarity side of the average value more than the average value may overcome the repulsive electric field and return to the background depending on the magnitude relationship between the repulsive force received from the toner cloud and the repulsive electric field by the background. May stick. And this causes soiling.

  Note that the present inventors are developing an image forming apparatus that performs a novel development called flare development. In this flare development, toner particles hopped on the electrode array mounting member are reciprocated between adjacent electrodes in the electrode array. Then, the reciprocating toner is conveyed to the developing region by the surface movement of the electrode array mounting member by rotational driving or the like. Similar problems may occur in such flare development.

  The present invention has been made in view of the above background, and an object of the present invention is to provide a hopping-type developing device capable of suppressing the occurrence of background contamination as compared with the conventional one, and a process unit and an image forming apparatus using the same. Is to provide.

In order to achieve the above object, the invention of claim 1 has an electrode array mounting member having a plurality of electrodes arranged in a predetermined direction, and pulse voltages that are out of phase with each other adjacent to each other in the plurality of electrodes. The toner hopped on the surface of the electrode array mounting member by the electric field formed by the application of is applied to the developing region where the electrode array mounting member and the latent image carrier of the image forming apparatus face each other. In the developing device for developing the latent image by attaching it to the latent image on the latent image carrier, reversely charged toner particles and high charge amount toner particles contained in the toner conveyed on the surface of the electrode array mounting member; Among them, a pre-development toner collecting means for collecting at least one of them from the surface area of the electrode array mounting member upstream of the developing area in the toner transport direction is provided.
The invention of claim 2 uses the developing device of claim 1 in which the pre-development toner collection means collects both the reversely charged toner particles and the high charge amount toner particles. It is a feature.
Further, the invention of claim 3 is the developing device according to claim 2, wherein the pre-development toner collecting means has a predetermined gap with respect to the surface area of the electrode array mounting member upstream of the development area in the toner transport direction. And oppositely charged toner particles and high charge amount toner particles hopping in the surface region of the electrode array mounting member are attached to the counter electrode before development and collected. It is characterized by using the thing.
According to a fourth aspect of the present invention, there is provided the developing device according to any one of the first to third aspects, wherein a predetermined gap is provided with respect to a region downstream of the developing region on the surface of the electrode array mounting member from the developing region. And a post-development facing member that faces each other.
According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image carried on the latent image carrier with toner. The developing device according to any one of claims 1 to 4 is used.
According to a sixth aspect of the present invention, in the image forming apparatus of the fifth aspect, the developing device according to the third aspect is used as the developing device, and the latent image with respect to the pre-development counter electrode is used as the pre-development toner collecting means. By supplying a separation bias having the same value as the background portion potential of the image carrier, the reversely charged toner particles and the toner conveyed in the surface area of the electrode array mounting member upstream of the development area in the toner conveyance direction What uses high charge amount toner particles to adhere to the counter electrode before development and separates them is used.
According to a seventh aspect of the present invention, in the image forming apparatus of the sixth aspect, the length in the direction perpendicular to the toner transport direction on the surface facing the electrode array mounting member as the counter electrode before development is the electrode array. A mounting member having a length equal to or greater than the length in the same direction of the surface facing the pre-development counter electrode is used.
The invention according to claim 8 is the image forming apparatus according to claim 6 or 7, wherein the length in the toner transport direction on the surface facing the electrode array mounting member as the pre-development counter electrode is the toner in the development region. It is characterized by using a thing longer than the length in the transport direction.
According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the sixth to eighth aspects, as the pre-development toner collecting means, a bias supplied to the pre-development counter electrode is discharged from the separation bias at a different value. By switching to the bias at a predetermined timing, the reversely charged toner particles and the high charge amount toner particles adhering to the counter electrode before development are returned to the surface of the electrode array mounting member at the predetermined timing. It is characterized by this.
According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the sixth to ninth aspects, the gap between the electrode array mounting member and the pre-development counter electrode is separated from the latent image carrier in the development region. It is characterized by having the same size as the gap with the electrode array mounting member.
According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the sixth to tenth aspects, a toner transport condition in a pre-development collection area where the electrode array mounting member and the counter electrode before development are opposed to each other is defined as This is characterized in that the toner conveyance conditions in the region are the same.
According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the sixth to eleventh aspects, the developing device having the post-development counter electrode as the post-development counter electrode in the development device of the fourth aspect is used. In addition, a bias supply means for supplying a bias having a polarity opposite to the normal charging polarity of the toner to the counter electrode after the development is provided.
According to a thirteenth aspect of the present invention, there is provided at least the latent image in an image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image carried on the latent image carrier with toner. 5. The process unit in which the carrier and the developing unit are held as a single unit on a common holding unit and can be integrally attached to and detached from the main body of the image forming apparatus. 5. A developing device is used.
According to a fourteenth aspect of the present invention, there is provided a process unit having a latent image carrier that carries a latent image and a developing unit that develops the latent image carried on the latent image carrier with toner on the latent image carrier. In the image forming apparatus for forming a toner image, the process unit according to claim 13 is used as the process unit.
According to a fifteenth aspect of the present invention, in the image forming apparatus according to the fourteenth aspect, a plurality of the process units are provided, and a toner image formed on the latent image carrier of each process unit is superimposed on a transfer member. A transfer means for transferring is provided.

  In these inventions, among the countless toner particles hopping on the electrode array mounting member and heading toward the development region, the reversely charged toner particles or the high charge amount toner particles are removed by the pre-development toner collecting means by the electrode array mounting member. By collecting from above, the amount of reversely charged toner particles or high charge amount toner particles conveyed to the development area is reduced. Thereby, generation | occurrence | production of background dirt can be suppressed rather than before.

Hereinafter, embodiments of an image forming apparatus to which the present invention is applied will be described.
FIG. 1 is a configuration diagram illustrating the toner transport substrate 1 and the transport power supply circuit 5 of the image forming apparatus according to the present embodiment, together with the photoconductor 25 of the image forming apparatus. In FIG. 1, a toner transport substrate 1 as an electrode array mounting member has a base 1a, a plurality of transport electrodes 1b, a surface layer 1c, and the like. The plate-like substrate 1a is formed by forming an insulating material into a plate shape. Each of the plurality of transport electrodes 1b has a strip shape, and in the same figure, the base is arranged in a posture that extends in the longitudinal direction in a direction perpendicular to the drawing sheet, and is arranged at a predetermined pitch in the left-right direction in the figure. It is formed on the surface of 1a. The surface layer 1c is laminated on the non-electrode forming surface of the substrate 1a and the plurality of transport electrodes 1b to cover them.

  Repetitive n-phase (for example, three-phase) pulse voltages that are out of phase with each other for forming a traveling electric field on the substrate are applied to the respective transport electrodes 1b by the transport power supply circuit 5 serving as pulse voltage supply means. More specifically, among the plurality of transport electrodes 1b, those that are located in the developing region Ar2 that is a region facing the photosensitive member 25 that is a latent image carrier and is relatively close to the photosensitive member 25 are 3 Va2 to Vc2, which are phase repetitive pulse voltages, are applied. Further, Va1 to Vc1, which are three-phase repetitive pulse voltages, are applied to the other transport electrodes 1b. The substrate area upstream of the development area Ar2 in the toner conveyance direction is a pre-development conveyance area Ar1 for conveying the toner T on the toner conveyance substrate 1 toward the development area Ar2. Further, in the substrate area downstream of the developing area Ar2 in the toner conveyance direction, the toner T excessively adhered to the surface of the photoreceptor 1 is returned to the toner conveyance board 1 or the toner T is collected from the toner conveyance board 1. The post-development transport area Ar3.

  The toner T on the toner transport substrate 1 is transported from the right side to the left side in the figure while hopping on the substrate by a traveling electric field formed on the substrate by repeatedly applying a pulse voltage to each transport electrode 1b. Go. As a result, the toner T existing in the pre-development transport area Ar1 is transported from the pre-development transport area Ar1 toward the development area Ar2, and enters the development area Ar2. In the developing area Ar2, a drum-shaped photoreceptor 25 that is rotationally driven by a driving unit (not shown) is disposed above the toner transport substrate 1 so as to face the toner transport substrate 1 with a predetermined development gap. . An electric field generated by an electrostatic latent image formed on the surface of the photosensitive member 25 by a known electrophotographic process acts on the toner T that has approached the photosensitive member 25 to some extent by hopping, and the toner T becomes an electrostatic latent image. Adhere to. At this time, since an electric field for electrostatically repelling the toner T is formed on the non-image portion (background portion) of the photoconductor 25, most of the toner T does not adhere to the background portion, but only the electrostatic latent image. Selectively adhere to. By such selective adhesion of the toner T, the electrostatic latent image on the photoconductor 25 is developed into a toner image.

  In the development area Ar2, a part of the toner T contributes to development in this way, and the rest is conveyed from the right side to the left side in the figure by repeated hopping, and passes through the development area Ar2 and is conveyed after development. Enter the area Ar3.

  In the vicinity of the entrance side in the post-development transport region Ar3, the hopped toner T is electrostatically moved from the ground portion toward the toner transport substrate 1 depending on the relationship between the background potential of the photoconductor 25 and the pulse potential of each transport electrode 1b. An electric field is generated. As a result, the toner T adhering to the background portion is collected on the toner transport substrate 1.

  FIG. 2 is a plan view showing the toner carrying substrate 1 from the front surface side. FIG. 3 is a longitudinal sectional view showing a cross section A-A ′ in FIG. 2 of the toner transport substrate 1. FIG. 4 is a cross-sectional view showing the B-B ′ cross section in FIG. 2 of the toner transport substrate 1. FIG. 5 is a cross-sectional view showing the C-C ′ cross section in FIG. 2 of the toner transport substrate 1. FIG. 6 is a cross-sectional view showing the D-D ′ cross section of the toner transport substrate 1 in FIG. 2. Note that the arrow X in FIGS. 2 and 3 indicates the toner conveyance direction. Hereinafter, the configuration of the toner transport substrate 1 will be described in detail with reference to these drawings.

  The plurality of transport electrodes 1b of the toner transport substrate 1 are adjacent to the A-phase transport electrode 1bA, the B-phase transport electrode 1bB adjacent to the A-phase transport electrode 1bA downstream in the toner transport direction, and the downstream in the toner transport direction. An electrode set including the C-phase transport electrode 1bC is arranged so as to be repeatedly arranged in the toner transport direction. By repeatedly disposing such an electrode set, an electrode row composed of a plurality of electrodes is formed on the surface of the base 1a. A surface layer 1c made of an insulating material is formed on the electrode array.

  Lead electrodes extending in the toner transport direction are connected to both ends in the longitudinal direction of the transport electrode 1b. This lead electrode is for A phase, B phase, and C phase, and the A phase one is connected to a plurality of A phase transport electrodes 1bA, and repeats the A phase from the transport power supply circuit (5). While receiving the application of the A-phase pulse voltage, which is a pulse voltage, it is guided to each A-phase transport electrode 1bA. The B-phase one is connected to a plurality of B-phase carrier electrodes 1bB, and receives the B-phase pulse voltage, which is a B-phase repetitive pulse voltage, from the carrier power supply circuit, and applies it to each B-phase carrier electrode 1bB. Lead to. The C-phase one is connected to a plurality of C-phase transport electrodes 1bC, and receives the C-phase pulse voltage, which is a C-phase repetitive pulse voltage, from the transport power supply circuit, and applies it to each C-phase transport electrode 1bC. Lead to. However, as described above, for the transport electrode 1b in the development area Ar2 shown in FIG. 1, a three-phase repetitive pulse voltage (Va2) different from the transport electrodes in the pre-development transport area Ar1 and the post-development transport area Ar3, respectively. , Vb2, Vc2) are applied. For this reason, the lead electrodes for A phase include transport A phase lead electrodes 2A connected to the A phase transport electrodes 1bA in the pre-development transport area Ar1 and post-development transport area Ar3, and the A phases in the development area Ar2. There is a developing A-phase lead electrode 3A connected to the transport electrode 1bA. Similarly, the B phase and the C phase include a transport B phase lead electrode 2B, a development B phase lead electrode 3B, a transport C phase lead electrode 2C, and a development C phase lead electrode 3C.

  An intermediate layer 1d is formed between the non-electrode-forming surface of the substrate 1a, each transport electrode 1b, and the surface layer 1c. The intermediate layer 1d material may be the same as or different from the surface layer 1c. The intermediate layer 1d is interposed between the A-phase transport electrode 1bA and the B-phase or C-phase lead electrodes (2B, 2C, 3B, 3C), thereby ensuring insulation between the two. An intermediate layer 1d is also interposed between the B-phase transport electrode 1bB and the A-phase and C-phase lead electrodes, thereby ensuring insulation between the two. Similarly, the C-phase transport electrode 1cC ensures insulation between the A-phase and B-phase lead electrodes.

  Each lead electrode is provided with an input terminal (not shown) for connecting a wiring from the carrier power supply circuit (5) which is a pulse voltage applying means. This input terminal may be provided in the same layer as the lead electrode, and may be connected to the input terminal through a wiring in a through hole provided in the base 1a, or the input terminal may be provided on the intermediate layer 1d and provided in the surface layer 1c. The holes may be connected to the input terminals through wiring.

As the substrate 1a, a substrate made of an insulating material such as glass, resin, ceramics, a substrate made of a conductive material such as stainless steel, an insulating film such as SiO _2, a flexible deformable material such as a polyimide film A substrate made of or the like can be used.

  The transport electrode 1b is formed by depositing a conductive material such as Al or Ni—Cr on the base 1a in a thickness of 0.1 to 10 μm (preferably 0.5 to 2.0 μm). It is processed into a required electrode pattern shape by technology or the like. The width L (see FIG. 3) of the transport electrode 1b in the toner transport direction X should be 1 to 20 times the average particle size of the toner T, and the gap G between the transport electrodes should be the same length. Is desirable.

The surface layer 1c, for example _{SiO 2, TiO 2, TiO 4} , SiON, BN, TiN, a thickness of the material of _Ta 2 _{O 5} or _the like is 0.5 to 20 [[mu] m] (preferably 0.5 to 3 [mu] m) The film is formed. Instead of these materials, inorganic nitride compounds such as SiN, Bn, and W may be used. In particular, since the charge amount of the toner tends to decrease during the conveyance when the surface hydroxyl groups increase, an inorganic nitride compound having a small surface hydroxyl group (SiOH, silanol group) is preferable.

  When a pulse voltage is repeatedly output from the conveyance power supply circuit 5 to the plurality of conveyance electrodes 1b in the toner conveyance substrate 1 having such a configuration, a traveling electric field is formed on the substrate. The toner on the toner transport substrate 1 is hopped by the electrostatic force generated by the traveling electric field. As shown in FIG. 7 and FIG. 8, the repetitive pulse voltage includes an A-phase pulse voltage Va, a B-phase pulse voltage Vb, and C that cause a rectangular pulse wave having a positive (+) or negative (-) value to rise in a predetermined cycle. Examples of the phase pulse voltage Vc that are out of phase with each other can be given. The A-phase pulse voltage Va, the B-phase pulse voltage Vb, and the C-phase pulse voltage Vc are applied to the A-phase transport electrode 1bA, the B-phase transport electrode 1bB, and the C-phase transport electrode 1bC.

  Assume that the negatively chargeable toner T is present on the B-phase transport electrode 1bB. At time T1, the A-phase carrier electrode 1bA that receives the A-phase pulse voltage Va and the B-phase carrier electrode 1bB that receives the B-phase pulse voltage Vb become “0 V (G)” and the C-phase pulse voltage Vc is Assume that the received C-phase transport electrode 1bC becomes “+ potential”. Then, the negatively chargeable toner T on the B-phase transport electrode 1bB is electrostatically attracted toward the C-phase transport electrode 1bC and hops from the substrate surface. And it moves on C-phase conveyance electrode 1bC.

  Next, at time T2, the A-phase transport electrode 1bA becomes “+ potential”, while the B-phase transport electrode 1bB and the C-phase transport electrode 1cC become “0 V (G)”. Then, a repulsive electric field for the toner T on the C-phase transport electrode 1bC is formed between the B-phase transport electrode 1bB and the C-phase transport electrode 1bC, and between the C-phase transport electrode 1bC and the A-phase transport electrode 1cC. Is formed with an attractive electric field for the toner T. As a result, the toner T on the C-phase transport electrode 1bC hops toward the A-phase transport electrode 1bA and moves onto the A-phase transport electrode 1bA.

  Furthermore, at time T3, it is assumed that the A-phase transport electrode 1bA and the C-phase transport electrode 1bC are each “0 V (G)” while the B-phase transport electrode 1bB is “+ potential”. Then, a repulsive electric field for the toner T on the A-phase transport electrode 1bA is formed between the C-phase transport electrode 1bC and the A-phase transport electrode 1bA, and between the A-phase transport electrode 1bA and the B-phase transport electrode 1bB. An attraction electric field is formed on the toner. As a result, the toner T on the A-phase transport electrode 1bA hops toward the B-phase transport electrode 1bB and moves onto the B-phase transport electrode 1bB. A traveling electric field in which the appearance and disappearance of the repulsive electric field as described above and the appearance and disappearance of the attraction electric field are repeated is formed on the toner transport substrate 1.

  The movement of the toner on the toner transport substrate 1 will be described in more detail. As shown in FIG. 9A, the toner is transferred when the A-phase, B-phase, and C-phase transport electrodes 1b are all at 0V (G). It is assumed that the negatively chargeable toner T is placed on the transport substrate 1. From this state, when only the A-phase transport electrode (A) becomes “+ potential” as shown in FIG. 9B, the toner T on the C-phase transport electrode (C) is directed toward the A-phase transport electrode (A). Electrostatically attracted and hopped, and moved onto the A-phase transport electrode (A). Next, as shown in FIG. 9C, when only the B-phase transport electrode (B) becomes “+ potential”, the toner T on the B-phase transport electrode (B) is transferred to the A-phase transport electrode (A) side. Receives a repulsive force and receives a suction force from the C-phase transport electrode (C) side. As a result, the toner on the B-phase transport electrode (B) hops from the substrate surface toward the C-phase transport electrode (C) and moves onto the C-phase transport electrode (C). Further, as shown in FIG. 9D, when only the C-phase transport electrode (C) becomes “+ potential”, the toner T on the C-phase transport electrode (C) is transferred from the B-phase transport electrode (B) side. While receiving a repulsive force, it receives a suction force from the A-phase transport electrode (A) side. As a result, the toner on the C-phase transport electrode (C) hops from the substrate surface toward the A-phase transport electrode (A) and moves onto the A-phase transport electrode (A).

  8 and 9, an example in which a negatively chargeable toner T is used and a positive polarity is applied to the electrode as a repetitive pulse voltage has been described. Conversely, a positively chargeable toner is used. A combination of T and a negative repetitive pulse voltage may be employed. Further, a combination of a positively or negatively chargeable toner T and a repetitive pulse voltage having the same polarity may be employed. Further, both positive and negative pulse voltages may be used in combination.

  FIG. 10 is a block diagram illustrating a part of an electric circuit of the image forming apparatus according to the present embodiment. In the figure, a carrier power supply circuit 5 includes a pulse signal generation circuit 6 that generates and outputs a pulse signal, a general A phase waveform amplifier 7A, a general B phase waveform amplifier 7B, a general C phase waveform amplifier 7C, and a development A phase. It has a waveform amplifier 8A, a developing B-phase waveform amplifier 8B, a developing C-phase waveform amplifier 8C, and the like.

  The pulse signal generation circuit 6 receives, for example, logic level input pulses, and includes two sets of pulses that are shifted in phase from each other by 120 °, and is included in the waveform amplifiers 7A, B, C, (A, B, C) of the next stage. A switching means, for example, a transistor is driven to generate and output a pulse signal having an output voltage of 10 to 15 V at a level capable of switching 100 [V].

  The general A-phase pulse wave, B-phase pulse wave, and C-phase pulse wave emitted from the pulse generation circuit 6 are a general A-phase waveform amplifier 7A, a general B-phase waveform amplifier 7B, and a general C-phase waveform amplifier 7C. To become a general-purpose A-phase pulse voltage Va1, B-phase pulse voltage Vb1, and C-phase pulse voltage Vc1. Then, the toner is applied to general A-phase, B-phase, and C-phase transport electrodes existing in the pre-development transport area (Ar1) and the post-development transport area (Ar3) on the toner transport substrate (1). The developing A-phase pulse wave, B-phase pulse wave, and C-phase pulse wave generated from the pulse generation circuit 6 are a development A-phase waveform amplifier 8A, a development B-phase waveform amplifier 8B, and a development C-phase waveform. Amplified by the amplifier 8C to become an A-phase pulse voltage Va2, B-phase pulse voltage Vb2, and C-phase pulse voltage Vc2 for development. Then, it is applied to the A-phase, B-phase, and C-phase transport electrodes for development existing in the development region (Ar2) of the toner transport substrate (1).

  The general-purpose A-phase waveform amplifier 7A, B-phase waveform amplifier 7B, and C-phase waveform amplifier 7C convert the pulse wave generated from the pulse generation circuit 6 to +100 [V] of each phase as shown in FIG. The application time ta is converted to three-phase pulse voltages Va1, Vb1, and Vc1 (about 3% of the repetition period tf) (referred to as “carrier voltage pattern”). Further, the A phase waveform amplifier 8A, the B phase waveform amplifier 8B, and the C phase waveform amplifier 8C for development use an application time of +100 [V] or 0] V] of each phase as shown in FIG. 12 or FIG. 13, for example. It is converted into a three-phase repetitive pulse voltage (Va2, Vb2, Vc2) in which ta is about 67% which is 2/3 of the repetitive period tf (this is referred to as a “hopping voltage pattern”). Such a transport voltage pattern or hopping voltage pattern causes an EH phenomenon in which the toner T is hopped on the toner transport substrate.

  EH development means a phenomenon in which wave movement occurs due to toner hopping on the surface of the electrode array mounting member. In this image forming apparatus, the toner can be conveyed from the pre-development conveyance area (Ar1) to the development area (Ar2) by this wave movement. Further, in the development area (Ar1), an electric field is formed so that the hopped toner is directed to the development carrier for the latent image on the latent image carrier, while being directed to the electrode array mounting member for the background portion. be able to.

  When a pulsed voltage waveform transitioning from 0 to −100 V is employed as in the hopping voltage pattern shown in FIG. 13, when the background potential on the latent image carrier is made lower than −100 V, the development region (Ar1) The toner hopped in is directed to the latent image in the vicinity of the latent image, while being directed to the substrate in the vicinity of the background portion. When the potential of the background portion is set to −150V or −170V, the toner is directed to the background portion near the toner background portion.

  In addition, when a pulse waveform in which the repetitive pulse voltage of the hopping voltage pattern transitions from 20 V to −80 V is adopted, the potential of the low level of the repetitive pulse voltage is set when the potential of the latent image is about 0 V and the potential of the background portion is −110 V. Is between the latent image potential and the background potential. Therefore, similarly, the toner hopped in the development area (Ar1) is directed to the latent image in the vicinity of the latent image, while being directed to the substrate in the vicinity of the background portion.

  In this way, by setting the low level potential of the repetitive pulse voltage to a value between the latent image potential and the background portion potential, the toner is attracted and adhered to the latent image, while the toner is applied to the background portion. Can be repelled. For the toner that has approached the latent image carrier to some extent by hopping, the traveling electric field does not reach, so that the toner can be easily ejected toward the latent image, and development with high image quality can be performed at a low voltage. Can be done.

On the other hand, in the so-called jumping development method using a developer carrier such as a developing roller, in order to remove the toner adhering to the surface of the developer carrier, the toner and the developer carrier are attached. It is necessary to apply an electrostatic force exceeding the wearing force. In addition, it is necessary to draw the separated toner toward the latent image on the latent image carrier and to repel the background portion. Under such conditions, a developing bias of DC 600 to 900 V must be applied to the developing carrier. On the other hand, if the ETH phenomenon is used, the above-described conditions may be provided outside the area of the traveling electric field, so that the strength of the traveling electric field is an electrostatic force exceeding the adhesion between the toner and the developer carrier. Any level may be used as long as it can act. For this reason, even when the amplitude of the repetitive pulse voltage applied to the transport electrode is a low voltage of | 150 to 100 V | or less, the toner can be selectively attached to the latent image. Further, since the potential difference between the latent image and the background portion in the latent image carrier such as the OPC photosensitive member does not need to be a large value as in the jumping method, the background portion potential can be considerably reduced. Thus, development of very small amounts of ozone and NO _x generated when uniformly charging the surface of the image bearing member background portion potential was suppressed reduction in the life of the friendly and the latent image bearing member to the environment It can be performed.

As latent image bearing member, the thickness of the surface of the CTL (Charge Transport Layer) is using the 15 [[mu] m] in and the OPC photosensitive member relative dielectric constant ε is about 3, the charge density of the toner 10 ^{-3 In the case of −4} [C / m ² ], if the EH phenomenon is used, a repetitive pulse voltage of 0 to −100 V and a duty of 50% may be applied to each transport electrode. Then, the value of the repetitive pulse voltage becomes -50 V on average, and if the toner is negatively charged, selective adhesion to the latent image of the toner becomes possible. By setting the average value (average potential) of the repetitive pulse potential applied to the carrier electrode to a potential between the latent image potential of the latent image carrier and the background potential, the image portion of the latent image of the latent image carrier In contrast, it is possible to generate an electric field in which the toner is directed toward the latent image carrier and the background is directed toward the transport substrate.

  The gap (interval) between the toner transport substrate and the OPC photoreceptor may be about 0.2 to 0.3 [mm]. Depending on the toner charge amount Q / M, the magnitude of the pulse voltage, the surface linear velocity of the OPC photoconductor, etc., in the case of a negatively chargeable toner, the background potential of the OPC photoconductor is −300 V or less, and further − Even if it is 100 V or less, it can be sufficiently developed. In the case of positively charged toner, the potential of the background portion becomes a positive potential.

  As the repetitive pulse voltage, a sinusoidal wave (sine curve), a triangular wave, or the like may be adopted in addition to the rectangular wave as shown. The duty of the repetitive pulse voltage can be adjusted in the range of 33.3 to 66.7 [%] in the case of three phases and in the range of 25 to 75 [%] in the case of four phases.

  In FIG. 3 described above, the electrode width L and the electrode gap G in the toner transport substrate 1 greatly affect the toner transport efficiency and the hopping efficiency. The toner flying in the middle between the electrodes is subjected to an electrostatic force in a substantially horizontal direction, whereas the toner directly above the transport electrode 1b has components in the vertical and horizontal directions with respect to the substrate surface. This is because the electrostatic force acts on the electrode width L and the electrode gap G. Specifically, the toner on the transport electrode 1b and in the vicinity of the end in the electrode width direction may jump over the adjacent transport electrode 1b due to hopping. The toner with a large moving distance increases. Thereby, the toner conveyance efficiency is increased. However, if the electrode width L is too large, the electric field strength on the transport electrode 1b and in the vicinity of the center in the electrode width direction will be insufficient, and the toner transport efficiency will decrease.

  The electrode gap G affects the electric field strength between the electrodes. As the electrode gap G becomes smaller, the electric field strength between the electrodes becomes stronger, and the initial speed (momentum) of hopping increases. However, with toner that moves from directly above the transport electrode 1b to just above the adjacent transport electrode 1b, the travel distance per hopping is shortened, so that the desired toner transport efficiency cannot be obtained unless the drive frequency is increased. .

  Furthermore, the thickness of the surface layer 1c covering the surface of the transport electrode 1b affects the electric field strength on the transport electrode 1b. In particular, the influence of the vertical component on the lines of electric force is increased.

  It is desirable that at least one toner is present on the transport electrode 1b in the transport direction. For this purpose, it is necessary to set the electrode width L to be equal to or greater than the average particle diameter of the toner. If the electrode width L is made smaller than this, the electric field acting on the toner is reduced, and the conveying force is remarkably high, which is not sufficient for practical use.

  In the vicinity of the center in the electrode width direction on the transport electrode 1b, the electric field lines extending from the electrode surface incline toward the traveling direction (horizontal direction) as the electrode width L increases, so that the electric field strength in the vertical direction decreases. . This reduces the initial speed of hopping. Therefore, if the electrode width L is too large, the image force between the toner and the surface of the substrate, the van der Waals force, the adsorption force due to moisture, etc. will be superior to the electric field strength for hopping, and the toner cannot be hopped. .

  From the viewpoint of the conveyance efficiency and the initial speed of hopping, the repetitive pulse voltage of a low voltage of about 100 [V] can be used as long as the electrode width L allows about 20 toners to exist on the conveyance electrode 1b in the electrode width direction. The toner can be transported efficiently with good hopping. For example, when the average particle diameter of the toner is 5 [μm], the electrode width L is preferably in the range of 5 to 100 [μm]. When the electrode width L is larger than that, toner stays on the transport electrode 1b.

  A more preferable range of the electrode width L for efficiently transporting the toner at a low voltage of 100 [V] or less applied by the pulse voltage is 2 to 10 times the average particle diameter of the toner. By setting the electrode width L within this range, the decrease in electric field strength near the center in the electrode width direction on the transport electrode 1b can be suppressed to 1/3 or less, and the decrease in hopping efficiency is 10% or less. Will no longer cause a significant drop. This corresponds to a range of 10 to 50 [μm] when the average particle diameter of the toner is 5 [μm], for example. A more preferable range of the electrode width L is 2 to 6 times the average particle diameter of the toner. This corresponds to, for example, 10 to 30 [μm] when the average particle diameter of the toner is 5 [μm].

  FIG. 14 is a graph showing the relationship between the electric field strength TE in the traveling direction (horizontal direction) in the electric field on the toner transport substrate and the electric field strength HE in the height direction. FIG. 15 is a graph showing the relationship between the electric field strength TE in the traveling direction, the electrode width L, and the electrode gap G. FIG. 16 is a graph showing the relationship between the electric field strength HE in the height direction, the electrode width L, and the electrode gap G. In these graphs, as the toner transport substrate, the electrode width L of the transport electrode 1b is 30 [μm], the electrode gap G is 30 [μm], the thickness of the transport electrode 1b is 5 [μm], and the thickness of the surface layer 1c is 0. .1 [μm], respectively, created based on experimental results using those set. The electric field intensity when the A-phase transport electrode 1bA becomes 0 [V] and the B-phase transport electrode 1bB becomes +100 [V]. In the drawing, only two transport electrodes are shown for easy understanding of details, but in the experiment, a toner transport substrate provided with a plurality of transport electrodes for A, B, and C phases was used. As the toner T, a toner having a particle diameter of 8 [μm] and a charge amount of −20 [μC / g] was used. The electric field strength shown in FIGS. 15 and 16 is the value of the representative point on the transport electrode 1b, and the representative point TEa of the traveling direction strength TE is 5 [μm] above the end of the transport electrode 1b as shown in FIG. This is the point. The representative point HEa of the electric field strength HE in the height direction is a point 5 [μm] above the center in the width direction of the transport electrode 1b.

  From these graphs, it is understood that the electric field strength for applying an electrostatic force for hopping to the toner T needs to be 5E + 5 [V / m] or more. Further, the electric field strength for applying a strong electrostatic force to the toner T so as not to stay on the electrode needs to be 1E + 6 [V / m] or more, and a more preferable electric field strength that can give a sufficient electrostatic force is as follows. It turns out that it is 2E + 6 [V / m] or more. The larger the electrode gap G, the lower the traveling direction electric field strength TE. The average particle diameter of the toner is 1 to 20 times, preferably 2 to 10 times, and more preferably 2 to 6 times.

  Further, as shown in the graph of FIG. 16, the hopping efficiency decreases as the electrode gap G increases, but a hopping efficiency that is practically acceptable is obtained up to 20 times the average particle size of the toner T. If the average particle diameter of the toner T exceeds 20 times, a large amount of toner stays on the electrode, so that the electrode gap G needs to be 20 times or less of the average particle diameter of the toner.

  According to the experiments by the present inventors, the average particle diameter of the toner is 2 to 10 [μm], and the charge amount Q / M is | 3 to 40 [μC / g] |, more preferably | 10 to 30 [μC]. / G] |, a particularly efficient toner conveyance can be realized.

  By providing the toner transport substrate with the surface layer 1c described above, contamination of the transport electrode 1b and toner adhesion to the substrate surface can be suppressed. FIG. 17 shows the results of measuring the electric field strength TE in the traveling direction when the thickness of the surface layer 1c is changed in the range of 0.1 to 80 [μm] in the electrode configuration shown in FIG. This is a result when a pulse voltage having an amplitude of 100 [V] is applied to each carrier electrode 1b. The dielectric constant ε of the surface layer 1c used in the experiment is higher than that of air, and is usually ε = 2 or more. As can be seen from the graph in the figure, if the film thickness of the surface layer 1c is too large, the electric field strength TE in the traveling direction acting on the toner on the substrate surface decreases. In consideration of the toner conveyance efficiency, the temperature and humidity resistance environment, etc., the practical thickness of the surface layer 1c is 10 [μm] or less, which preferably keeps the decrease in the toner conveyance efficiency to about 30 [%], more preferably the toner conveyance efficiency. It is 5 [μm] or less, which keeps the decrease to a few [%].

  FIG. 18 is a schematic diagram showing a state of an electric field on the toner transport substrate when the thickness of the surface layer 1c is 5 [μm]. FIG. 19 is a schematic diagram showing a state of an electric field on the toner transport substrate when the thickness of the surface layer 1c is 30 [μm]. In any case, the electric field generated when a pulse voltage having an amplitude of 100 [V] is applied to each transport electrode of the toner transport substrate having an electrode width L of 30 [μm] and an electrode interval G of 30 [μm]. State. As can be seen from these figures, as the thickness of the surface layer 1c increases, the number of lines of electric force bridging between the electrodes in the surface layer 1c having a dielectric constant higher than that of air increases. Decrease. Further, the electric field strength acting on the toner is reduced by the thickness of the surface layer 1c. The number of lines of electric force in the height direction that contribute to toner hopping greatly depends on the thickness of the surface layer 1c. With a small pulse voltage of about 100 [V], the electric field strength that does not cause toner retention is 1E + 6 [V / m] or more. Further, the electric field strength that can hop the toner with sufficient momentum is 2E + 6 [V / m] or more. The thickness of the surface layer 1c that satisfies these conditions is 10 [μm] or less, more preferably 5 [μm] or less.

As a material for the surface layer 1c, a material having a specific resistance of 10 ⁶ [Ωcm] or more and a dielectric constant ε of 2 or more is preferably used. In the case of using a negatively chargeable toner, it is desirable that the background potential of the photoreceptor is set to −300V or a value closer to 0V. In addition, when positively charged toner is used, it is desirable that the voltage be +300 V or less. In this way, even when a low pulse voltage of 150 to 100 [V] or less is applied to each transport electrode arranged at a fine pitch, the toner can be hopped satisfactorily.

  As the toner resin material, from the viewpoint of melting temperature, transparency, and the like, styrene-acrylic copolymers, polyester resins, epoxy resins, polyol resins and the like are generally used. The charging characteristics of the toner are affected by these resin materials, but the characteristics can be adjusted by adding a charge control agent. Examples of the charge control agent for the black toner (BK) include a nigrosine dye and a quaternary ammonium salt in the case of positive charging. In the case of negative charging, examples include azo metal-containing complexes and salicylic acid metal complexes. Examples of the charge control agent for color toner include quaternary ammonium salts and imidazole complexes in the case of positive charging. In the case of negative charging, salicylic acid metal complexes, salts, organic boron salts and the like can be mentioned.

  Since the toner repeats contact and separation with the surface layer 1c as hopping on the toner transport substrate due to the action of the traveling electric field, the toner is affected by frictional charging. It depends on the charging series between materials. By maintaining the charge amount of the toner at a saturation charge amount determined mainly by the charge control agent, or to some extent, the hopping efficiency and development efficiency can be improved. Specifically, in the case of a negatively chargeable toner, a material that exhibits frictional chargeability close to that used as a charge control agent for the toner or a positively chargeable material is used for the surface layer 1c. It is preferable. For example, when the toner charge control agent is a salicylic acid metal complex, polyamide-based resins such as polyamide 66 (trade name) and nylon 11 (trade name) are preferable. In the case of a positively chargeable toner, it is preferable to use a material that exhibits frictional chargeability close to that used as a charge control agent for the toner or a negatively chargeable material for the surface layer 1c. For example, when the charge control agent is a quaternary ammonium salt, a fluorine-containing resin such as Teflon (registered trademark) is preferable.

  On the surface of the toner transport substrate, irregularities corresponding to a region where the electrode is present under the surface layer 1c and a region where the electrode is not present are generated. However, by setting the thickness of the transport electrode 1b to 3 [μm] or less, it is possible to suppress a decrease in toner transportability due to the unevenness. Thereby, the planarization process of the surface layer 1c can be omitted and the substrate manufacturing cost can be reduced.

  FIG. 20 is a schematic configuration diagram illustrating the photosensitive member 25 and the developing device 30 of the image forming apparatus according to the present embodiment. In the figure, a photosensitive member 25 as a latent image carrier is rotationally driven in a clockwise direction in the drawing by a driving means (not shown). A developing device 30 having a toner transport substrate 1 is disposed on the side of the photoconductor 25 in the drawing.

  The developing device 30 has a housing portion for housing a mixture agent (not shown) containing toner and magnetic particles in the casing 31. In addition, it has a toner transport section 33 that houses the cylindrical toner transport substrate 1 for receiving the toner supplied from the storage section and transporting it to the development area (Ar2) that is the area facing the photoconductor 25. .

  The above-described housing portion is divided into a first housing portion 32a, a second housing portion 32b, and a third housing portion 32c, and the first housing portion 32a and the second housing portion 32b are separated by a partition wall 31a. . A first conveying screw 34 that conveys the mixture from the near side to the far side in the direction perpendicular to the drawing sheet is disposed in the first accommodating portion 32a while being driven to rotate by a driving means (not shown). Yes. In addition, a second transport screw 35 that transports the mixture from the back side to the front side in the same direction while being driven to rotate by a driving unit (not shown) is disposed in the second storage portion 32a. A supply roll 36 is disposed in the third storage portion 32c.

  In the first accommodating portion 32a, the mixed agent conveyed from the near side in the drawing to the vicinity of the end on the far side in the drawing along with the rotation of the first conveying screw 34 passes through a communication port (not shown) provided in the partition wall 31a. To enter the second housing portion 32b. Then, along with the rotation of the second transport screw 34, the second transport screw 34 is transported from the back side to the front side in the figure.

  A supply roll 36 disposed in the third housing portion 32c includes a supply sleeve 36a made of a non-magnetic pipe that is rotated in a counterclockwise direction in the drawing by a driving means (not shown), Magnet roller 36b. The magnet roller 36b includes six magnetic poles in which N and S poles are alternately arranged in the circumferential direction.

  A part of the mixture conveyed from the rear side to the front side in the drawing as the second conveying screw 34 rotates in the second accommodating portion 32b is adsorbed on the surface of the supply sleeve 36a by the magnetic force generated by the magnet roller 36b. The And it is pumped up by the supply sleeve 36a which rotates as a mixture carrier, and enters into the 3rd accommodating part 32c. Thereafter, the thickness of the sleeve on the sleeve is regulated at a position facing the doctor grade 37 while following the supply sleeve 36a, and then the position facing the cylindrical toner transport substrate 1 in the toner transport section 33 is reached.

  A roll bias is applied to the supply roll 36 by a roll power supply circuit 38. The toner in the mixture that has entered the position facing the toner conveyance substrate 1 while being rotated along the supply sleeve 36a is caused by the potential difference between the roll bias and the pulse voltage applied to the conveyance electrode of the toner conveyance substrate 1. And then transferred onto the toner transport substrate 1. By this transfer, toner is supplied to the supply area of the toner transport substrate 1.

  The toner supplied to the supply area of the toner transport substrate 1 is transported relatively counterclockwise in the figure while hopping along the curved surface of the toner transport substrate 1 by the action of the traveling electric field. Then, after passing through the pre-development transport area (Ar1) and entering the development area (Ar2) to contribute to development, the post-development transport area (Ar3) is entered.

  On the supply sleeve 36a of the third storage portion 32c, the mixture that has supplied the toner to the toner transport substrate 1 passes through a position facing the toner transport substrate 1 as the sleeve rotates, and then the second storage portion 32b. Return to the opposite position. And it separates from the sleeve surface by the magnetic force of the two repulsive magnetic poles of the magnet roller 36b, and returns to the second housing portion 32b. Further, after being transported to the vicinity of the front end in the direction orthogonal to the drawing surface as the second transport screw 35 rotates, the interior of the first accommodating portion 32a passes through a communication port (not shown) provided in the partition wall 31a. Return to.

  The admixture that has returned to the inside of the first storage portion 32a is transferred from the front side to the back side in the drawing along with the rotation of the first transfer screw 34, from a magnetic permeability sensor or the like fixed to the bottom surface of the casing 31. The toner density sensor 40 detects the toner density. This detection result is sent to a toner density control unit (not shown). The toner density control unit drives a toner replenishing device (not shown) for a predetermined time when the detection result by the toner density sensor 40 is a predetermined threshold value or less. As a result, toner is supplied into the first storage portion 32a through the toner supply port 31b of the casing 31, and the toner density is recovered.

  The toner replenished in the first storage portion 32a is conveyed while being stirred and mixed with the magnetic particles by the first conveying screw 34 and the second conveying screw 35, or the mixture layer thickness regulation by the doctor blade 37 on the supply sleeve 36a. It is possible to sufficiently triboelectrically charge by pressurizing with. In this state, the toner is supplied to the pre-development conveyance area of the toner conveyance substrate 1. In this embodiment, a negatively chargeable toner is used as the toner, but a positively chargeable toner may be used.

  FIG. 21 is a schematic diagram showing the photoreceptor, the toner transport substrate 1 and the supply roll 36 of the image forming apparatus according to the present embodiment. In the drawing, the supply sleeve 36a of the supply roll 36 is driven to rotate in the counterclockwise direction in the figure by a driving means (not shown). Then, a cylindrical toner transport substrate 1 disposed on the side of the supply sleeve 36a is mixed with an infinite number of magnetic particles M carried on the surface and a toner adhering to the surface of each magnetic particle M. Rubbing.

  On the surface of the cylindrical toner conveying substrate 1, the toner is conveyed while hopping in the counterclockwise direction in the drawing along the curved surface. Then, after passing through the development area (Ar2), which is the area facing the photoconductor 25, and the post-development transport area (Ar3), it returns to the supplied area (Ar0), which is the area facing the supply sleeve 36a. . At the boundary between the supplied area (Ar0) and the post-development conveyance area (Ar3), the surface of the supply sleeve 36a that moves from the vertical direction upward to the bottom with respect to the toner conveyed upward from the vertical direction downward Face each other. Then, as shown in FIG. 22, the toner on the toner transport substrate 1 is scraped off and collected on the supply sleeve 36a by the mixed agent that moves while being carried on the surface of the supply sleeve 36a. That is, in the image forming apparatus according to the present embodiment, the supply sleeve 36a functions as a collection member. By actively scraping off the toner on the toner transport substrate 1 with a mixture, even if the toner transport density is relatively high, the toner can be satisfactorily recovered from the toner transport substrate 1 and a recovery failure occurs. Can be suppressed.

  FIG. 23 is a schematic configuration diagram illustrating an image forming apparatus according to the present embodiment. In the figure, a drum-like photoconductor 25 (for example, organic photoconductor: OPC) as a latent image carrier is rotated in the clockwise direction in the drawing.

  When an operator places a document (not shown) on the contact glass 50 and presses a print start switch (not shown), a first scanning optical system 53 including a document illumination light source 25 and a mirror 52 and first mirrors 54 and 55 are provided. The two-scan optical system 56 moves to read the original image.

  The scanned document image is read as an image signal by an image reading element 58 disposed behind the lens 57, and the read image signal is digitized and processed. Then, the laser diode (LD) is driven by the processed signal, and the laser light from the laser diode is reflected by the polygon mirror 59, and then the photoconductor 25 is scanned through the mirror 60. Prior to this scanning, the photosensitive member 25 is uniformly charged by the charging device 61, and an electrostatic latent image is formed on the surface of the photosensitive member 25 by scanning with a laser beam.

  The electrostatic latent image is developed into a toner image with toner attached thereto by the developing device 30, and then conveyed to a transfer area that is an area facing the transfer charger 66 as the photosensitive member 25 rotates. In this transfer region, a first paper feed unit 62 having a first paper feed roller 64 or a second paper feed unit having a second paper feed roller 65 so as to be synchronized with the toner image on the photoconductor 25. Recording paper P is fed from 63. The toner image on the photoconductor 25 is transferred onto the recording paper P by corona discharge of the transfer charger 66. The recording paper P onto which the toner image has been transferred in this way is separated from the surface of the photosensitive member 25 by corona discharge of the separation charger 67 and then conveyed toward the fixing roller pair 69 by the conveying belt 68. Then, after entering the fixing nip formed by the contact of the two rollers of the fixing roller pair 69 and fixing the toner image, the toner image is discharged toward a discharge tray 70 outside the apparatus.

  The transfer residual toner that has adhered to the surface of the photoconductor 25 that has passed through the transfer region is removed from the surface of the photoconductor 25 by the cleaning device 71. The surface of the photosensitive member 25 that has been subjected to the cleaning process in this manner is discharged by the discharging lamp 72 and is prepared for the next latent image formation.

Next, a characteristic configuration of the image forming apparatus according to the present embodiment will be described.
Generally, when toner powder is rubbed, the triboelectric charge amount of individual toner particles in the toner powder is not constant, and the charge amount shows a normal distribution curve. In addition, there are not a few negatively charged toner particles that are not reflected in the normal distribution curve and are frictionally charged to a polarity opposite to the normal polarity.

  In FIG. 1 described above, the individual toner particles that hop in the pre-development area Ar1 gradually approach the development area Ar2 as described above, but include reversely charged toner particles. The reversely charged toner particles fly while being attracted to the electrode adjacent to the transport electrode when the toner particles charged to the normal polarity are flying while being attracted to any of the A, B, and C phase transport electrodes. . Then, it gradually approaches toward the developing area Ar2. Further, the reversely charged toner particles that are larger in the normal polarity side than the average charge amount are gradually approaching toward the developing area Ar2 in the same manner as the toner particles having the average charge amount. When these reversely charged toner particles and high charge amount toner particles are transported to the developing area Ar2, they adhere to the non-image area (background area) of the photosensitive member 25 and cause soiling.

  Therefore, in the image forming apparatus according to the present embodiment, the development that collects the reversely charged toner particles and the high charge amount toner particles among the toner particles hopped on the toner transport substrate 1 in the pre-development transport area Ar1. Pre-toner collecting means is provided.

  FIG. 24 is an enlarged configuration diagram illustrating the toner transport substrate 1 and its peripheral configuration in the developing device (30) of the image forming apparatus in an enlarged manner. In the drawing, the one-dot chain line arrow indicates the conveyance direction by toner hopping on the toner conveyance substrate 1. As shown in the figure, the developing device (30) of the image forming apparatus has a predetermined gap with respect to the surface located in the pre-development transport area Ar1 in the entire area of the toner transport substrate 1 in the toner transport direction. And a pre-development counter electrode 100 facing each other. This pre-development counter electrode 100 has at least a surface facing the toner transport substrate 1 curved so that the gap with the toner transport substrate 1 is uniform from the upstream end to the downstream end in the toner transport direction. Yes.

  First, with reference to FIG. 10 and the like, for the A, B, and C phase transport electrodes (1bA, 1bB, and 1bC) positioned in the pre-development transport area Ar1, general A phase pulse voltage Va1 and B phase pulse voltage are used. It has been described that the Vb1, C-phase pulse voltage Vc1 is output. However, among the plurality of A, B, and C phase transport electrodes positioned in the pre-development transport area Ar1, those in the area facing the pre-development counter electrode 100 shown in FIG. 24 are in the development area Ar2. Similarly to the above, the A-phase pulse voltage Va2, B-phase pulse voltage Vb2, and C-phase pulse voltage Vc2 for development are output.

  The gap between the pre-development counter electrode 100 and the toner transport substrate 1 is set to the same value as the development gap, which is the minimum gap between the photosensitive member 25 and the toner transport substrate 1 in the development area Ar2. That is, the toner is hopped in the gap between the pre-development counter electrode 100 and the toner transport substrate 1 under the same conditions as the development area Ar2.

  A pre-development counter bias power supply 101 is connected to the pre-development counter electrode 100 through a conductive line, and the background portion (uniform charging potential) on the photoconductor 25 is pre-development having a DC voltage of the same polarity and value. Outputs counter bias. That is, by applying the pre-development counter bias, the potential of the pre-development counter electrode 100 has the same polarity and the same value as the background portion potential on the photoconductor 25.

  The above-mentioned pre-development toner collecting means includes a pre-development counter electrode 100, a pre-development counter bias power source 101, and a control unit (not shown) that controls on / off of the pre-development counter bias output from this power source. During the developing operation (a state in which toner that can contribute to the development of the electrostatic latent image is being conveyed in the pre-development conveyance area Ar1 and the development area Ar2), the pre-development counter bias with respect to the pre-development counter electrode 100. Is applied. In such a configuration, among the infinite number of toner particles hopped in the pre-development transport area Ar1, a scumming toner that adheres to the background portion of the photoreceptor 25 in the development area Ar2 and causes scumming, that is, reverse charging. The toner particles and the high charge amount toner particles are selectively attached to the counter electrode 100 before development. Thus, the background toner is selectively separated from the toner conveyed in the pre-development conveyance area Ar1.

  When the developing operation (continuous developing operation at the time of continuous printing) is completed, the control unit uses the control signal to output the output voltage from the pre-development counter bias power supply 101 from the above-mentioned separation bias to the toner charging polarity side. To a large discharge bias (large in the negative side in this example). In addition, the charging device (61) is controlled so that the uniform charging potential of the photosensitive member 25 is increased to the charging polarity side of the toner than during normal printing. As a result, the reversely charged toner particles and the high charge amount toner particles adhering to the counter electrode 100 before development are separated from the counter electrode 100 before development and discharged onto the toner transport substrate 1. Then, after passing through the development area Ar2 and the post-development transport area Ar3, the toner is collected on the development sleeve 36a.

  The high charge amount toner particles conveyed on the pre-development conveyance area Ar1 have a larger charge amount than other toner particles, and therefore hop higher than the other toner particles. Then, when the maximum level is reached by hopping, a toner cloud composed of a large amount of toner particles is positioned below itself, and due to the repulsive force, the toner cloud 1 may be scattered to the extent that the electric field restraint force does not reach. is there. By providing the pre-development counter electrode 100, it is possible to prevent such scattering of toner particles having a high charge amount.

  As the counter electrode 100 before development, it is desirable to use a surface of an electrode layer made of a conductive material such as metal (a surface facing the toner transport substrate 1) covered with an insulating layer made of an insulating material. According to this configuration, it is possible to avoid charge injection to the toner particles and leakage of the charge of the toner particles to the electrode layer due to direct contact between the toner particles and the conductive electrode layer.

  Further, as the counter electrode 100 before development, the length in the direction orthogonal to the toner transport direction on the surface facing the toner transport substrate 1 is the length in the same direction of the surface facing the counter electrode 100 before development on the toner transport substrate 1. More than that is used. In such a configuration, with respect to the toner hopping on the substrate surface in the pre-development conveyance region Ar1, separation processing of the reversely charged toner particles and the high charge amount toner particles is performed in all regions in the direction orthogonal to the toner conveyance direction on the substrate surface. Can be applied.

  In addition, as the pre-development counter electrode 100, the one in which the length in the toner transport direction on the surface facing the toner transport substrate 1 is longer than the length in the toner transport direction of the development region Ar <b> 2 is used. In such a configuration, unlike the case where the length of the development area Ar2 is less than the length in the toner transport direction, the toner is transported immediately below the counter electrode 100 before development for a time longer than the development area passage time, so that the development area Ar2 is grounded. Reversely charged toner particles and high charge amount toner particles that become dirty toner can be reliably separated. The photosensitive member 25 and the toner transport substrate 1 are opposed to each other with the same length as the diameter of the photosensitive member 25 in the toner transport direction, but the developing region Ar2 is a photosensitive member in the region facing the substrate and the photosensitive member 25. The length in the toner transport direction in such a development region Ar2 where 25 is a region that is considerably close to the toner transport substrate 1 due to its curvature can be measured as follows. That is, the solid image formed on the photosensitive member 25 is developed while photographing the development area Ar2 and the behavior of the toner in the vicinity in the vicinity thereof with a high-magnification high-speed camera. Then, the position at which the toner particles adhering to the upstream end of the solid image in the rotation direction of the photoconductor are hopped last on the substrate surface, and the toner particles adhering to the downstream end of the solid image in the photoconductor rotation direction are on the substrate surface. Measure the distance from the last hopped position. This distance is the length in the toner transport direction in the development area Ar2.

  In this image forming apparatus, the toner transport conditions in the region where the toner transport substrate 1 and the pre-development counter electrode 100 face each other (hereinafter, this region is referred to as a pre-development collection region) are the same as the toner transport conditions in the development region Ar2. It is set. In such a configuration, it is possible to avoid the deterioration of separation / collection accuracy of the reversely charged toner particles and the high charge amount toner particles caused by making the toner conveyance condition in the pre-development collection area different from the development area Ar2. The toner conveyance conditions referred to here are a combination of the width of the conveyance electrode (length in the toner conveyance direction), the arrangement pitch of the conveyance electrodes, the conveyance voltage pattern applied to each conveyance electrode, and the frequency of the pulse voltage.

Next, the image forming apparatus of each example in which a more characteristic configuration is added to the image forming apparatus according to the embodiment will be described. Note that the configuration of the image forming apparatus according to each example is the same as that of the embodiment unless otherwise specified.
[First embodiment]
FIG. 25 is an enlarged configuration diagram illustrating the toner transport substrate 1 and its peripheral configuration in the developing device (30) of the image forming apparatus according to the first embodiment. In the figure, the post-development counter electrode 102, which is a post-development counter member, faces the surface located in the post-development transport region Ar3 in the entire toner transport direction region of the toner transport substrate 1 through a predetermined gap. is doing. Similarly to the pre-development counter electrode 102, the post-development counter electrode 102 is at least a toner transport substrate so that the gap with the toner transport substrate 1 is uniform from the upstream end to the downstream end in the toner transport direction. The surface facing 1 is curved.

  In such a configuration, the post-development counter electrode 102 can prevent the toner particles conveyed in the post-development conveyance area Ar3 from scattering. Note that a post-development counter bias power source 103 is connected to the post-development counter electrode 102 via a conduction line. This post-development counter-bias power supply 103 outputs a post-development counter-bias having the same polarity as the toner charging polarity to the post-development counter electrode 102. In this configuration, contact between the counter electrode 102 after development and the toner particles hopped can be suppressed by electrically repelling the counter electrode 102 after development and the toner hopped on the substrate surface by a counter bias after development. . Thereby, adhesion of toner particles to the counter electrode 102 after development can be suppressed.

  As the counter electrode 102 after development, for the same reason as that of the counter electrode 100 before development, an electrode layer made of a conductive material such as metal is coated with an insulating layer made of an insulating material. desirable. Further, the length of the surface facing the toner transport substrate 1 in the direction orthogonal to the toner transport direction is set to be equal to or longer than the length of the surface facing the pre-development counter electrode 100 of the toner transport substrate 1 in the same direction. It is desirable. Furthermore, it is desirable to use a toner conveying substrate whose length in the toner conveying direction on the surface facing the toner conveying substrate 1 is equal to or longer than the length of the developing region Ar2 in the toner conveying direction.

  Further, if the value of the counter bias after development is excessively increased, the transport electric field on the toner transport substrate 1 is crushed and the good transport of toner is hindered. Therefore, the size is set such that the carrier electric field is not crushed.

[Second Embodiment]
FIG. 26 is a schematic configuration diagram illustrating an image forming apparatus according to the second embodiment. The image forming apparatus includes four optical writing devices 80Y, 80M, 80M, 80C, 80K, 4K corresponding to four colors of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K), respectively. Process units 81Y, M, C, and K are provided. Also provided are a paper feed cassette 82 for storing recording paper, a paper feed roller 83 for feeding recording paper from this cassette, and the like. Furthermore, a transfer belt 84 that conveys the recording paper fed from the paper supply roller 83 to the transfer unit of each process unit, a fixing unit 87 that fixes an image on the recording paper, and a recording paper after image fixing are placed. A paper discharge tray 88 is also provided.

  The four process units 81Y, 81M, 81C, and 81K have the same configuration except that the color of the toner used is different. As an example, a Y process unit 81Y for forming a Y toner image includes a photosensitive member 25Y, a charging roller 51Y as a charging unit, a developing device 30Y, a cleaning blade 52Y and the like as shown in FIG. It has in the casing. The image forming apparatus main body is detachable.

  FIG. 28 is an enlarged configuration diagram showing the photoreceptor 25Y and the developing device 30Y in the Y process unit. The developing device 30Y contains only non-magnetic Y toner, not a mixture containing non-magnetic Y toner and magnetic particles. In the toner storage section that stores toner, Y toner is frictionally charged while being stirred by the first stirring blade 42Y and the second stirring blade 43Y. The Y toner thus frictionally charged is pumped up by the supply roller 44Y that is driven to rotate in the clockwise direction, and then is moved to a position facing the supply region in the cylindrical toner transport substrate 1 as the roller rotates. Carried.

  A roll bias is applied to the supply roller 44Y by a roll power supply circuit (not shown), and the Y toner on the supply roller 44Y receives an electrostatic force due to a potential difference between the roll bias and a pulse voltage applied to each transport electrode. Thus, the supply roller 44Y moves to the supply area of the toner transport substrate 1Y. Then, by the traveling electric field on the toner transport substrate 1Y, it is transported relatively clockwise in the drawing while hopping along the curved surface of the toner transport substrate 1Y, and passes through the pre-development transport region (Ar1). At this time, the reversely charged toner particles and the high charge amount toner particles are separated from the toner transport substrate 1 by the counter electrode 100Y before development. The toner particles remaining on the toner transport substrate 1 after separation enter the development area (Ar2) and contribute to development.

  A metal recovery roller 45Y that is rotated counterclockwise in the drawing by a driving means (not shown) is disposed below the toner conveyance substrate 1Y in the drawing, and a post-development conveyance region (Ar3) on the toner conveyance substrate 1Y. ) Through a predetermined gap. The toner that has not contributed to development in the development area (Ar2) proceeds to the post-development conveyance area (Ar3) and is electrostatically attracted to the surface of the collection roller 45Y to which a collection bias is applied.

  As the recovery bias, a DC voltage having a polarity opposite to that of the three-phase pulse voltage applied to each carrier electrode is employed. In the second embodiment, a collection bias of about 0 to +100 [V] is applied to the collection roller 45Y.

  The gap between the collection roller 45Y and the toner transport substrate 1 is set to 50 to 1000 [μm], preferably 150 to 400 [μm], and is preferably smaller than the hopping height of Y toner on the substrate. In the second embodiment, it is set to about 400 [μm].

  The Y toner adsorbed on the surface of the collecting roller 45Y is scraped off from the roller surface by a scraping blade 46Y that contacts the collecting roller 45Y, and then returns to the toner container by gravity.

  In the post-development transport area (Ar3), as shown in the drawing, the Y toner transport direction on the toner transport substrate 1 and the surface movement direction of the collection roller 45Y are set in the same direction. Then, the average transport speed vt of the toner on the toner transport substrate 1 and the surface moving speed vk of the collection roller 45Y are set so as to satisfy the condition “vt ≦ vk”. In such a setting, of the entire area of the surface of the collecting roller 45Y that moves endlessly with respect to the toner conveyed toward the post-development conveyance area (Ar3), a solid area where no toner is attached is faced. Let As a result, the toner conveyed in the post-development conveyance area (Ar3) can be satisfactorily adhered to the solid area of the collection roller 45Y, and occurrence of toner collection failure can be suppressed.

  Although only the Y process unit 81Y using Y toner has been described, the process units 81M, C, and K for other colors have the same configuration.

  In FIG. 27 described above, a slit for allowing the laser beam L from the Y optical writing device (80Y) to enter the casing is provided on the casing rear surface side of the Y process unit 81Y.

  In FIG. 26, the Y, M, C, and K optical writing devices 80Y, 80M, 80C, and 80K include a semiconductor laser (not shown), a collimator lens, an optical deflector such as a polygon mirror, and scanning imaging optics. It consists of systems. Then, a laser beam modulated in accordance with image data for each color input from a host (image processing apparatus) such as a personal computer outside the apparatus is emitted. The emitted laser beam scans the Y, M, C, and K photoconductors 25Y, M, C, and K, and writes an electrostatic latent image.

  When the image forming operation is started, the photoconductors 25Y, M, C, and K of the process units 81Y, M, C, and K are uniformly charged by the charging roller, and then the optical writing devices 80Y, M, C, and A laser beam corresponding to image data is irradiated from K to carry an electrostatic latent image. This electrostatic latent image is developed and visualized with toner of each color by ETH development by the toner transport substrate of the developing device.

  In synchronization with image formation of each color of each process unit 81Y, M, C, K, the recording paper in the supply cassette 82 is fed by the paper feed roller 83 and then conveyed toward the transfer belt 84. Then, the recording paper is sequentially fed to the transfer section in each of the process units 81Y, 81M, 81C, 81K while being held by the transfer belt 84 that moves endlessly. At each transfer portion, the Y, M, C, and K toner images on the photoconductors 25Y, 25M, 25C, and 25K are superimposed and transferred onto the transfer belt 84 that is a transfer body. Thereby, a full-color image is formed on the recording paper. The recording sheet is fed into the fixing unit 87 and the full color image is fixed, and then discharged to a discharge tray 88 outside the apparatus.

  In the figure, reference numeral 85 designates a transfer unit which is a transfer means for moving the transfer belt 84 endlessly in the clockwise direction in the drawing while being stretched by a plurality of rollers. This transfer unit 85 has transfer rollers 86Y, 86M, 86C, 86K inside the loop of the transfer belt 84, and between the photoconductors 25Y, 25M, 86K, and the transfer rollers 86Y, 86M, 86C, 86K. The transfer belt 84 is sandwiched between them to form a transfer portion. A transfer bias is applied to the transfer rollers 86Y, 86M, 86C, 86K by bias applying means (not shown). As a result, a transfer electric field is formed between the photoconductors 25Y, M, C, and K and the transfer rollers 86Y, M, C, and K in the transfer portions for the respective colors, so that the image on the photoconductors 25Y, M, C, and K is formed. The toner image is transferred onto the transfer belt 84.

  As shown in the figure, the transfer unit 85 stretches the transfer belt 84 in a vertically long posture with a space in the vertical direction rather than the horizontal direction. The housing of the image forming apparatus is provided with an opening / closing door (not shown). When the opening / closing door is opened, the transfer unit 85 is a rotating shaft of a driven roller which is a tension roller located at the lowest side in the drawing. As shown in FIG. 29, it can be rotated around the center. When this rotation takes a horizontally long posture that takes a space in the horizontal direction rather than the vertical direction, the process units 81Y, 81M, 81C, and 81K of each color can be exposed to the outside as illustrated. In this state, the process units 81Y, 81M, 81C, and 81K of each color are attached to and detached from the image forming apparatus main body by being slid in the horizontal direction.

[Third embodiment]
FIG. 30 is a schematic configuration diagram illustrating an image forming apparatus according to the third embodiment. The image forming apparatus includes a transfer belt 84 that is endlessly moved in a counterclockwise direction in the drawing while being stretched in a horizontally long posture that takes a space in a horizontal direction rather than a vertical direction. Above the horizontal upper tension surface of the transfer belt 84, four process units 81Y, 81M, 81C, and 81K are arranged along the belt moving direction.

  These process units 81Y, 81M, 81C, and 81K have the same configuration except that the color of the toner used is different. Taking the Y process unit 81Y as an example, as shown in FIG. 31, it has a charging roller 51Y, a developing device 30Y, a drum cleaning device 48Y, and the like around the drum-shaped photoconductor 25Y, and these are supported. It is integrally supported by a body casing. The image forming apparatus main body is detachable.

  The Y, M, C, and K toner images developed on the photoconductors 25Y, M, C, and K of the process units 81Y, M, C, and K of the respective colors are transferred onto the transfer belt 84 in a superimposed manner, and are four-color toners. Become a statue. With the endless movement of the transfer belt 84, the transfer belt 84 is sent to the secondary transfer nip where the front surface of the transfer belt 84 and the secondary transfer roller 89 come into contact with each other, and simultaneously onto the recording paper P that has entered the nip. Batch transfer is performed.

[Fourth embodiment]
FIG. 32 is an enlarged configuration diagram illustrating the developing device and the photoconductor of the image forming apparatus according to the fourth embodiment. Also in the developing device 30 of this image forming apparatus, only non-magnetic Y toner is used instead of a mixture containing non-magnetic Y toner and magnetic particles.

  A recovery brush roller 47 in which an infinite number of raised brushes are erected on the peripheral surface of the rotating shaft member is disposed below the cylindrical toner transport substrate 1 in the figure, and a clock in the figure is driven by a driving means (not shown). It is rotationally driven in the turning direction.

  At the position where the toner transport substrate 1 and the collection brush roller 47 face each other, the toner transport direction and the surface movement direction of the collection brush roller 47 are opposite to each other. Then, the surface of the collection brush roller 47 moves in the reverse direction, thereby weakening the momentum of the rapid flow in the forward direction or generating the airflow in the reverse direction. As a result, the toner staying time at the position facing the recovery brush roller 47 is extended, so that even when the toner transport density is relatively high, the toner can be recovered satisfactorily from the toner transport substrate 1 and the recovery is poor. Can be suppressed.

  The collection brush roller 47 is disposed so that the front end side of the brush is rubbed against the post-development pre-development conveyance area (Ar3) of the toner conveyance substrate 1. This rubbing promotes frictional charging of the toner. The toner that has passed through the developing area (Ar2) is mechanically scraped from the toner transport substrate 1 by the recovery brush roller 47, and then transferred to the recovery brush roller 47 to which a recovery bias having a polarity opposite to that of the toner is applied. In the post-development transport area (Ar3), the recovery brush roller 47 is surface-moved in the direction opposite to the toner transport direction, so that the toner can be actively scraped by the brush. Thereby, it is possible to more reliably suppress toner collection failure.

  As the recovery bias, a DC voltage having a polarity opposite to that of the three-phase pulse voltage applied to each carrier electrode is employed. In the third modified apparatus, a recovery bias of about 0 to +100 [V] is applied to the recovery brush roller 47.

  The toner adhering to the front end side of the brush is removed from the brush by an impact when the brush is repelled by the flicker bar 49 arranged so as to contact the brush while extending in the brush rotation axis direction. Instead of the flicker bar 49, a bias roller may be brought into contact with the brush tip. The toner removed from the brush by the flicker bar 49 returns to the toner container by its own weight.

[Fifth embodiment]
FIG. 33 is an enlarged configuration diagram illustrating the developing device and the photoconductor of the image forming apparatus according to the fifth embodiment. Also in the developing device 30 of this image forming apparatus, only non-magnetic Y toner is used instead of a mixture containing non-magnetic Y toner and magnetic particles.

  Below the cylindrical toner conveyance substrate 1 in the figure, a collection plate 150 made of a flexible plate-like member is cantilevered by a vibrator 151, and its free end faces the toner conveyance substrate 1. . A collection bias for forming an electric field for electrostatically moving the toner from the toner conveyance substrate 1 side toward the collection plate 150 side is applied between the toner conveyance substrate 1 and the collection plate 150.

  The toner that passes through the development area (Ar2) and reaches the post-development conveyance area (Ar3) while hopping on the toner conveyance substrate 1 reaches the position opposite to the collection plate 150, and then reaches the collection plate 150 from the substrate. Metastasize. A control unit (not shown) turns on the power supply to the vibrator 151 and vibrates the vibrator 151 at a predetermined timing (a timing when a certain amount of collected toner accumulates on the collecting plate 150). Due to this vibration, the toner is removed from the flexible recovery plate 150 and returned to the toner container.

[Sixth embodiment]
FIG. 34 is an enlarged configuration diagram illustrating the developing device and the photoconductor of the image forming apparatus according to the sixth embodiment. Also in the developing device 30 of this image forming apparatus, only non-magnetic Y toner is used instead of a mixture containing non-magnetic Y toner and magnetic particles.

  Below the toner transport substrate 1, a suction nozzle 152 connected to the suction side of the suction pump 153 directs the suction port toward the toner transport substrate 1. When the suction pump 153 is activated, air existing between the suction nozzle 152 and the toner transport substrate 1 is sucked from the suction port of the suction nozzle 152.

  The toner that passes through the development area (Ar2) and reaches the post-development conveyance area (Ar3) while hopping on the toner conveyance substrate 1 is sucked by the suction nozzle 152 together with air. Then, the ink is returned to the toner container through the discharge pipe 154 connected to the discharge side of the suction pump 153.

  A seal member 155 is cantilevered at the downstream end of the suction nozzle 152 in the toner transport direction, and the free end of the seal member 155 is in contact with the toner transport substrate 1. This avoids a situation in which the air around the supply roller 44Y is sucked together with the toner on the supply roller 44Y.

  Up to this point, an example of outputting a three-phase voltage as a forward n-phase pulse voltage or a reverse n-phase pulse voltage has been described. You may make it apply to an electrode.

  In addition, although the example in which the pre-development toner collecting unit is configured to collect both the reversely charged toner particles and the high charge amount toner particles has been described, only one of the toners may be collected.

  As described above, in the image forming apparatus according to the embodiment and each example, as the pre-development toner collecting unit, the one that collects both the reversely charged toner particles and the high charge amount toner particles is used. In such a configuration, it is possible to suppress the occurrence of background contamination as compared with the case of collecting only one of the toner particles.

  Further, in the image forming apparatus according to the embodiment and each example, the pre-development toner collecting unit is predetermined with respect to the pre-development collection area which is the toner conveyance substrate surface area upstream of the development area Ar2 in the toner conveyance direction. And having oppositely charged toner particles and high charge amount toner particles hopping in the pre-development recovery area adhered to the pre-development counter electrode 100. The one to be collected is used. In such a configuration, the reversely charged toner particles and the high charge amount toner particles of the toner hopped in the pre-development collection area can be attached to the counter electrode 100 before development and separated from the other toner particles.

  Further, in the image forming apparatus according to the first embodiment, a predetermined value is applied to the post-development transport area Ar3, which is an area downstream of the development area Ar2 on the surface of the toner transport substrate 1 that is an electrode array mounting member. And a post-development facing member that faces each other through the gap. In such a configuration, the post-development counter electrode 102 can prevent the toner particles conveyed in the post-development conveyance area Ar3 from scattering.

  Further, in the image forming apparatus according to the embodiment and each example, as a pre-development toner collecting unit, a separation bias having the same value as the background portion potential of the photosensitive member as a latent image carrier is supplied to the pre-development counter electrode 100. As a result, the reversely charged toner particles and the high charge amount toner particles are pre-developed from the toner conveyed in the pre-development conveyance area Ar1 which is the surface area of the electrode array mounting member upstream of the development area Ar2. An electrode that adheres to and separates from the counter electrode 100 is used. In such a configuration, the reversely charged toner particles and the high charge amount toner particles can be separated from the other toner particles due to a difference in charge polarity and charge amount from the toner particles.

  In the image forming apparatus according to the embodiment and each example, the length in the direction orthogonal to the toner conveyance direction on the surface facing the toner conveyance substrate 1 as the counter electrode 100 before development is the development on the toner conveyance substrate 1. Those having a length in the same direction of the surface facing the front counter electrode 100 are used. In such a configuration, with respect to the toner hopping on the substrate surface in the pre-development conveyance region Ar1, separation processing of the reversely charged toner particles and the high charge amount toner particles is performed in all regions in the direction orthogonal to the toner conveyance direction on the substrate surface. Can be applied.

  In the image forming apparatus according to the embodiment and each example, the length in the toner transport direction on the surface facing the toner transport substrate 1 as the counter electrode 100 before development is the length in the toner transport direction of the development area Ar2. The above is used. In such a configuration, the reversely charged toner particles and the high charge amount toner particles that become scumming toner in the developing area Ar2 are reliably obtained by conveying the toner immediately under the counter electrode 100 before development for a time longer than the developing area passing time. Can be separated.

  In the image forming apparatus according to the embodiment and each example, as a pre-development toner collecting unit, the bias supplied to the pre-development counter electrode 100 is switched from the separation bias to another discharge bias at a predetermined timing. Thus, the reversely charged toner particles and the high charge amount toner particles adhering to the counter electrode 100 before development are returned onto the surface of the toner transport substrate 1 at a predetermined timing. In this configuration, due to excessive accumulation of reversely charged toner particles and high charge amount toner particles on the counter electrode 100 before development, the toner particles are reversed from the counter electrode 100 before development to the toner transport substrate 1 during the developing operation. It is possible to avoid such a situation that it is moved.

  In the image forming apparatus according to the embodiment and each example, the gap between the toner transport substrate 1 and the pre-development counter electrode 100 is the same as the gap between the photosensitive member 25 and the toner transport substrate 1 in the development area Ar2. Therefore, it is possible to avoid the deterioration of the collection accuracy of the reversely charged toner particles and the high charge amount toner particles caused by the former gap being different from the latter gap.

  In the image forming apparatus according to the embodiment and each example, the toner transport condition in the recovery area before development where the toner transport substrate 1 and the counter electrode 100 before development face each other is the same as the toner transport condition in the development area Ar2. Therefore, it is possible to avoid the deterioration of the recovery accuracy of the reversely charged toner particles and the high charge amount toner particles due to the difference in the toner conveying conditions.

  Further, in the image forming apparatus according to the embodiment or each example, the developing device 30 includes a post-development counter electrode 102 which is a post-development counter electrode, and the toner is normally charged with respect to the post-development counter electrode 102. Bias supply means for supplying a bias having a polarity opposite to that of the polarity is provided. In such a configuration, it is possible to suppress adhesion of the toner particles hopped in the post-development transport area Ar3 to the counter electrode 102 after the development.

  In the image forming apparatus according to the second and third embodiments, a plurality of process units are provided, and a transfer belt 84 or a recording sheet as a transfer member for a toner image formed on the photosensitive member of each process unit. Since a transfer unit is provided as a transfer means for transferring the image superimposed on P, a multicolor image can be formed by superimposing a plurality of color toner images.

1 is a configuration diagram illustrating a toner transport substrate and a transport power supply circuit of an image forming apparatus according to an embodiment together with a photoreceptor of the image forming apparatus. FIG. 3 is a plan view showing the toner transport substrate from the front surface side. FIG. 3 is a longitudinal sectional view showing a cross section A-A ′ in FIG. 2 of the toner transport substrate. FIG. 3 is a transverse sectional view showing a B-B ′ section in FIG. 2 of the toner transport substrate. FIG. 3 is a transverse sectional view showing a C-C ′ section in FIG. 2 of the toner conveying substrate. FIG. 3 is a transverse sectional view showing a D-D ′ section in FIG. 2 of the toner transport substrate. FIG. 6 is a waveform diagram showing an A-phase pulse voltage Va, a B-phase pulse voltage Vb, and a C-phase pulse voltage Vc applied to each transport electrode of the toner transport substrate. FIG. 4 is a schematic diagram illustrating the toner transport substrate and a state of a voltage applied to each transport electrode of the toner transport substrate. (A), (b), (c), (d) is a schematic diagram for demonstrating the behavior of the toner on the toner conveyance board | substrate, respectively. FIG. 2 is a block diagram showing a part of an electric circuit of the image forming apparatus. FIG. 6 is a waveform diagram showing three-phase repetitive pulse voltages Va1, Vb1, and Vc1 applied to respective transport electrodes in a supplied region and a post-development transport region of the toner transport substrate. FIG. 4 is a waveform diagram showing three-phase repetitive pulse voltages Va2, Vb2, and Vc2 applied to the respective transport electrodes in the development region of the toner transport substrate. FIG. 13 is a waveform diagram showing repetitive pulse voltages Va2, Vb2, and Vc2 at timings different from those in FIG. 6 is a graph showing a relationship between an electric field strength TE in a traveling direction (horizontal direction) of a traveling electric field formed on the toner transport substrate and an electric field strength HE in a height direction. The graph which shows the relationship between the electric field strength TE of the advancing direction, the electrode width L, and the electrode gap | interval G. The graph which shows the relationship between the electric field strength HE of the height direction, the electrode width L, and the electrode gap G. 6 is a graph showing the relationship between the thickness of the surface layer of the toner carrying substrate and the electric field strength TE in the traveling direction. The schematic diagram which shows the state of the electric field on the homologous carrier conveyance board | substrate in case the thickness of the same surface layer is 5 [micrometers]. The schematic diagram which shows the state of the electric field on the homologous carrier conveyance board | substrate in case the thickness of the same surface layer is 30 [micrometers]. FIG. 2 is a schematic configuration diagram illustrating a photoreceptor and a developing device in the image forming apparatus. FIG. 3 is a schematic diagram illustrating a photoconductor, a toner transport substrate, and a supply roll of the image forming apparatus. FIG. 3 is an enlarged schematic diagram illustrating a facing portion between the toner transport substrate and a supply roll. FIG. 2 is a schematic configuration diagram illustrating the image forming apparatus. FIG. 3 is an enlarged configuration diagram illustrating an enlarged toner conveyance substrate and a peripheral configuration thereof in the developing device. FIG. 3 is an enlarged configuration diagram illustrating, in an enlarged manner, a toner transport substrate and its peripheral configuration in the developing device of the image forming apparatus according to the first embodiment. FIG. 6 is a schematic configuration diagram illustrating an image forming apparatus according to a second embodiment. FIG. 3 is an enlarged configuration diagram illustrating a process unit for Y in the image forming apparatus. FIG. 2 is an enlarged configuration diagram illustrating a photosensitive member and a developing device of the process unit. FIG. 2 is a schematic configuration diagram illustrating the image forming apparatus in a state where a transfer unit is rotated to a retracted position. FIG. 6 is a schematic configuration diagram illustrating an image forming apparatus according to a second embodiment. FIG. 3 is an enlarged configuration diagram illustrating a process unit for Y in the image forming apparatus. FIG. 10 is an enlarged configuration diagram illustrating a developing device and a photoconductor of an image forming apparatus according to a fourth embodiment. FIG. 10 is an enlarged configuration diagram illustrating a developing device and a photoconductor of an image forming apparatus according to a fifth embodiment. FIG. 10 is an enlarged configuration diagram illustrating a developing device and a photoconductor of an image forming apparatus according to a sixth embodiment.

Explanation of symbols

1: Toner transport substrate (electrode array mounting member)
1bA: Phase A transport electrode 1bB: Phase B transport electrode 1bC: Phase C transport electrode 25: Photoconductor (latent image carrier)
30: Developing device 81Y, M, C, K: Process unit 84: Transfer belt (transfer body)
85: Transfer unit (transfer means)
100: Pre-development counter electrode (part of pre-development toner collecting means)
102: Counter electrode after development 103: Counter bias power supply (bias supply means) after development
Ar2: Development area P: Recording paper (transfer body)

Claims (15)

An electrode array mounting member having a plurality of electrodes arranged in a predetermined direction, and mounting of the electrode array by an electric field formed by applying pulse voltages that are out of phase with each other to adjacent electrodes in the plurality of electrodes The toner hopped on the surface of the member is attached to the latent image on the latent image carrier in the developing region where the electrode array mounting member and the latent image carrier of the image forming apparatus are opposed to each other. In a developing device for developing
At least one of the reversely charged toner particles and the high charge amount toner particles contained in the toner transported on the surface of the electrode array mounting member is disposed on the upstream side of the developing area in the toner transport direction. A developing device comprising a pre-development toner collecting means for collecting from a surface area of a mounting member. The developing device according to claim 1.
A developing device using, as the pre-development toner collecting means, a unit that collects both the reversely charged toner particles and the highly charged toner particles. The developing device according to claim 2.
The pre-development toner collecting means has a pre-development counter electrode facing the electrode array mounting member surface area upstream of the development area in the toner transport direction with a predetermined gap, and A developing apparatus comprising: a reversely charged toner particle hopping on a surface region of an electrode array mounting member; and a high charge amount toner particle that is collected by adhering to the counter electrode before development. The developing device according to any one of claims 1 to 3,
A developing apparatus, comprising a post-development facing member that faces a region on the surface of the electrode array mounting member that is downstream of the developing region with respect to the toner conveying direction with a predetermined gap. In an image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image carried on the latent image carrier with toner.
An image forming apparatus using the developing device according to claim 1 as the developing means. The image forming apparatus according to claim 5.
While using the developing device of claim 3 as the developing device,
As the pre-development toner collecting means, a separation bias having the same value as the background potential of the latent image carrier is supplied to the pre-development counter electrode, so that the electrode array upstream of the development region in the toner transport direction An image forming apparatus comprising: a toner that is transported on a surface area of a mounting member, and that separates a reversely charged toner particle and a highly charged toner particle by attaching them to the counter electrode before development. The image forming apparatus according to claim 6.
As the counter electrode before development, the length in the direction orthogonal to the toner conveyance direction on the surface facing the electrode array mounting member is the same length of the surface facing the counter electrode before development in the electrode array mounting member. An image forming apparatus using the above. The image forming apparatus according to claim 6 or 7,
An image forming apparatus using the pre-development counter electrode having a length in the toner transport direction on the surface facing the electrode array mounting member that is equal to or greater than the length of the development region in the toner transport direction . The image forming apparatus according to any one of claims 6 to 8,
The reversely charged toner particles attached to the pre-development counter electrode by switching the bias supplied to the pre-development counter electrode from the separation bias to another discharge bias at a predetermined timing as the pre-development toner collecting means And an image forming apparatus that returns high-charge toner particles onto the surface of the electrode array mounting member at the predetermined timing. The image forming apparatus according to any one of claims 6 to 9,
An image forming apparatus, wherein the gap between the electrode array mounting member and the pre-development counter electrode is made the same size as the gap between the latent image carrier and the electrode array mounting member in the development area. The image forming apparatus according to any one of claims 6 to 10,
An image forming apparatus, wherein a toner conveyance condition in a pre-development collection area where the electrode array mounting member and the pre-development counter electrode face each other is the same as the toner conveyance condition in the development area. The image forming apparatus according to any one of claims 6 to 11,
The developing device having a post-development counter electrode as the post-development counter electrode in the development device of claim 4 is used, and a bias having a polarity opposite to the normal charging polarity of the toner is supplied to the post-development counter electrode. An image forming apparatus comprising a bias supply unit. In an image forming apparatus comprising a latent image carrier that carries a latent image and a developing unit that develops the latent image carried on the latent image carrier with toner, at least the latent image carrier and the developing unit are provided as one unit. As a process unit that is held by a common holding body and can be integrally attached to and detached from the image forming apparatus main body,
5. A process unit using the developing device according to claim 1 as the developing means. Image forming apparatus for forming a toner image on a latent image carrier by a process unit having a latent image carrier that carries the latent image and a developing unit that develops the latent image carried on the latent image carrier with toner In
An image forming apparatus using the process unit according to claim 13 as the process unit. The image forming apparatus according to claim 14.
An image forming apparatus comprising: a plurality of process units; and transfer means for transferring a toner image formed on the latent image carrier of each process unit in a superimposed manner on a transfer body.

Images