JP5483142B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus including the developing device.

  2. Description of the Related Art Conventionally, as this type of developing device, one that uses toner hopped on the surface of a toner carrier for development is known.

  In the developing device described in Patent Document 1, a plurality of electrodes are arranged at a predetermined interval of about several tens [μm] in the circumferential direction of an insulating support base, and the surfaces of the support base and the electrodes are insulative. It has a cylindrical toner carrier on which surface layers are laminated. These electrodes are formed by repeatedly arranging electrode pairs composed of two adjacent electrodes. An alternating electric field is formed between the two electrodes in each electrode pair. Then, the toner located on one electrode in the electrode pair floats and landes on the other electrode, or floats on the other electrode and landes on one electrode. Then, while repeating hopping in this way, the cylindrical toner carrier is transported to the developing region by surface movement accompanying rotational driving. In the developing region, the toner that has floated to the vicinity of the latent image on the latent image carrier is attracted to the electric field by the latent image and does not descend toward the electrode of the toner carrier, and adheres to the latent image. In such a configuration, not the toner adsorbed on the developing roller or the magnetic carrier but the toner that does not exhibit the adsorbing force by hopping is used for the development. As a result, low-potential development that cannot be realized by the conventional one-component development method or two-component development method in which development is performed using toner adsorbed on a developing roller or a magnetic carrier can be realized. .

JP-A-3-21967

  However, when the toner is hopped on the surface of the toner carrying member as in the developing device described in Patent Document 1, the toner carrying member and the toner repeatedly collide, and the toner is subjected to stress due to the collision. Deteriorates. Thus, when the toner deteriorates, there arises a problem that the latent image on the latent image carrier cannot be developed satisfactorily.

  In particular, during continuous printing, the time during which the toner hops on the surface of the toner carrying member is longer than in the case of single-shot printing, so the toner is more susceptible to stress and the above problem becomes more prominent.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device and an image forming apparatus capable of reducing toner deterioration by suppressing stress applied to the toner when the toner carrying member collides with the toner. Is to provide a device.

In order to achieve the above object, according to the first aspect of the present invention, a plurality of electrodes are arranged at predetermined intervals along the surface of the support substrate, and an insulating surface layer is formed on the surface of the support substrate and the electrodes. And an electric field for hopping toner charged to a predetermined polarity carried on the surface of the toner carrier by applying a periodic voltage to the plurality of electrodes. Hopping electric field generating means for generating on the surface of the toner carrying member, and transporting the toner carried on the surface of the toner carrying member to a developing region facing the latent image carrying member on the latent image carrying member. in the developing device for developing the latent image by adhering toner to the latent image, when non-development during continuous printing, shorten the voltage application time during which a voltage is applied to the plurality of electrodes than at the time of development control the hopping electric field generator A control means for performing relative stage, the control means, when developing, and control of the hopping electric field generating means to apply a voltage with a frequency f1 and is periodically T1, during non-development, in the period T2, the frequency The hopping electric field generating means is controlled so as to apply a voltage of period T1 and m times each period, and the period T1 and the period T2 satisfy the relationship of T1 × m <T2. It is.
The invention of claim 2 is the developing apparatus according to claim 1, wherein the frequency range of the voltage applied to the plurality of electrodes by the hopping electric field generating means at least during the development is 0.1 [kHz] or more and 10 [ kHz] or less.
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the toner adhesion amount detecting means for detecting the adhesion amount of the toner adhered to the latent image on the latent image carrier, and the toner carrier Toner layer potential detecting means for detecting the potential of the toner layer in the hopping state on the surface, and the control means is configured to detect the detection result of the toner adhesion amount detecting means and the detection result of the toner layer potential detecting means. The above control is performed based on this.
According to a fourth aspect of the present invention, in the developing device according to the first, second, or third aspect, the surface layer of the toner carrier has a charge of the same polarity as the normal charging polarity of the toner due to friction with the toner. It is characterized by being formed of a material having electrical properties that can be imparted.
According to a fifth aspect of the present invention, in the developing device of the first, second, third, or fourth aspect, the periodic voltage applied to the plurality of electrodes during the development is such that the average potential value at each moment is the latent image. It is characterized in that it is set to have a value between the image portion potential and the non-image portion potential formed on the carrier.
According to a sixth aspect of the present invention, there is provided a latent image carrier that carries a latent image, and a developing means that develops the toner by attaching toner to the latent image of the latent image carrier. An image forming apparatus for forming an image by finally transferring a developed toner image onto a transfer material, wherein the developing device of claim 1, 2, 3, 4 or 5 is used as the developing means. To do.
According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect of the present invention, the image forming apparatus includes a plurality of the developing devices that store a plurality of color toners in association with each color, and are formed on the latent image carrier. A full color image obtained by superimposing a plurality of toner images of the respective colors is formed on the transfer material.

  Here, during “continuous printing”, the “development” refers to the time when the latent image on the latent image carrier is developed by the developing device, and the “non-development” refers to the development of the latent image on the latent image carrier. This is when the image is not developed by the apparatus.

  In the present invention, at the time of non-development during continuous printing, whether the frequency of the voltage applied to the plurality of electrodes is lower than at the time of development or whether the voltage application time for applying the voltage to the plurality of electrodes is shortened. The control means performs at least one of the control on the hopping electric field generating means. Thus, the number of collisions between the toner carrying member and the toner at the time of non-development can be reduced as compared with the case where a voltage having the same frequency as that at the time of development is applied for the same time. Therefore, since the number of collisions between the toner carrying member and the toner at the time of non-development is reduced, the stress applied to the toner by the collision with the toner carrying member is suppressed, and toner deterioration can be reduced.

  As described above, according to the present invention, there is an excellent effect that the deterioration of the toner can be reduced by suppressing the stress applied to the toner due to the collision between the toner carrier and the toner.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, the same part is represented by the same symbol. FIG. 2 shows an example of an image forming apparatus to which the present invention can be applied.

  In the image forming apparatus of the present embodiment, an image carrier 11 in which an organic photoreceptor is configured in a belt shape is stretched by a plurality of stretching rollers, and is rotated in the direction of the arrow in the drawing by a rotation driving mechanism (not shown). Be prepared to be. On the left side of the image carrier 11 in the drawing, an image forming unit 70K as a plurality of image forming units for forming toner images of each color of black (K), magenta (M), cyan (C), and yellow (Y), 70M, 70C, and 70Y are arranged along the surface of the image carrier 11. The image forming units 70K, 70M, 70C, and 70Y include developing devices 13K, 13M, 13C, and 13Y that store toners of black, magenta, cyan, and yellow, respectively, and charging devices that charge the image carrier 11 with negative polarity. 12K, 12M, 12C, and 12Y, and writing devices 4K, 4M, 4C, and 4Y that write latent images corresponding to the colors of black, magenta, cyan, and yellow, respectively, on the charged image carrier 11 according to image information are provided. It has been. As the writing device 4, various devices such as an optical scanning device using a polygon and an LED array can be used.

  Further, as shown in FIG. 3, the developing devices 13K, 13M, 13C, and 13Y are detachable from the space that is opened when the image carrier 11 is retracted, and can be replaced by the user.

  First, the image carrier 11 is uniformly charged by the charging device 12K of the image forming unit 70K, and is exposed by the laser beam 72K modulated by the black image data by the writing device 4K as the exposure means. An electrostatic latent image is formed. The electrostatic latent image is developed by the developing device 13K and becomes a black toner image. Thereafter, the image carrier 11 is neutralized by a neutralizing device (not shown) to prepare for the next image formation.

  Next, the image carrier 11 is uniformly charged by the charging device 12M of the image forming unit 70M, and is exposed by the laser beam 72M modulated with magenta image data by the writing device 4M at a predetermined timing. An electrostatic latent image is formed on the carrier 11. The electrostatic latent image is developed by the developing device 13M, and becomes a magenta toner image overlapping the black toner image. Thereafter, the image carrier 11 is neutralized by a neutralizing device (not shown) to prepare for the next image formation.

  Next, the image carrier 11 is uniformly charged by the charging device 12C of the image forming unit 70C, and is exposed to laser light 72C modulated with cyan image data by the writing device 4C at a predetermined timing. An electrostatic latent image is formed on the carrier 11. The electrostatic latent image is developed by the developing device 13C, and becomes a cyan toner image overlapping the black toner image and the magenta toner image. Thereafter, the image carrier 11 is neutralized by a neutralizing device (not shown) to prepare for the next image formation.

  Next, the image carrier 11 is uniformly charged by the charging device 12Y of the image forming unit 70Y, and is exposed by the laser beam 72Y modulated with yellow image data by the writing device 4Y at a predetermined timing. An electrostatic latent image is formed on the carrier 11. The electrostatic latent image is developed by the developing device 13Y to become a yellow toner image that overlaps the black toner image, the magenta toner image, and the cyan toner image. Thereby, a full-color image is formed on the image carrier 11.

  Below the image forming apparatus, there is provided a paper feeding device 5 that stores a transfer material such as recording paper and starts conveying the transfer material during image formation. A full-color image on the image carrier 11 is transferred by a transfer roller 2 as a transfer unit to which a transfer material is fed from the paper feeding device 5 and a transfer bias is applied to the transfer material from a power source (not shown) provided in the image forming apparatus. (Toner image of each color) is transferred. The transfer material onto which the full-color image has been transferred is heated while being sandwiched between the heating roller 3a and the pressure roller 3b of the fixing device 3 provided at the upper part of the image forming apparatus, whereby the full-color image is fixed on the transfer material. After that, it is discharged outside.

  Note that the image forming apparatus of the present embodiment does not include a cleaning member for collecting the transfer residual toner particles on the surface of the image carrier 11. Transfer residual toner particles remain on the surface of the image carrier 11, but are charged by the four charging devices 12, transferred to a transfer material, and removed from the image carrier 11. When the transfer residual toner particles are transferred to the transfer material, some image disturbance occurs, but if the transfer residual toner particles are slightly disturbed, they are not visually recognized.

  In the image forming apparatus according to the present embodiment, four color images are written on the same image carrier 11, so that in principle the color is different from the tandem method in which a dedicated image carrier is provided for each color. Almost no deviation occurs, and a high-quality full-color image without color deviation can be obtained on the image carrier 11.

  In the mode in which the position of each color toner image is adjusted and the toner density is adjusted, a toner image having a predetermined pattern is formed on the image carrier 11 and faces the surface of the image carrier 11 on which the toner image is formed. Such a toner pattern is detected by a P sensor (not shown) provided, and the writing timing and the development bias are changed based on the detection result, so that an optimum color image can be obtained.

  FIG. 4 shows an enlarged view of the vicinity of the developing device 13 in the image forming unit. Since each color developing device has the same structure, only one will be described.

  In the present embodiment, a corona charging method is adopted as the charging device 12. If a charging unit is used in which the charging device 12 is not in contact with the image carrier 11 as in the corona charging method, the toner image formed by the image forming unit 70 on the upstream side in the rotation direction of the image carrier is not disturbed. The carrier 11 can be charged.

  The toner carrier 13a provided in the developing device 13 is opposed to the image carrier 11 in a non-contact manner with a gap of 50 to 1000 [μm], preferably 150 to 400 [μm] at least during image formation. Yes.

  Further, the developing device 13 shown in FIG. 4 is provided with a supply roller 13h for supplying toner particles to the toner carrier 13a. The toner carrier 13a and the supply roller 13b are rotated by a rotation driving mechanism (not shown). It has come to be.

  A toner regulating member 13c that regulates the toner layer is formed in the upstream portion of the developing region in the toner transport direction to form a toner thin layer. The regulating member 13c is brought into contact with the toner by a blade, a roller, or the like. At that time, the toner is charged by friction between the toner carrying member 13a, the regulating member 13c, and the like and the toner. Further, as shown in FIG. 5, a paddle 13d for pumping up the toner stored in the developing casing 13e to the supply roller 13h is installed in a region opposite to the image carrier 11 of the supply roller.

  The toner particles in this embodiment are those obtained by radical polymerization in the state where a styrene or acrylic polymerizable monomer is dispersed in water together with a polymerization initiator as a binder resin, or a polyester resin is dispersed in water. Non-magnetic toner particles having a weight average particle size of about 5 [μm] obtained by granulating using a polymer obtained by polyaddition reaction and adding a colorant, a charge control agent, etc. .

  Further, a paddle 13d is provided for pumping the toner contained in the developing device 13 to the supply roller 13h while stirring. The toner pumped up by the supply roller 13h is provided so as to face the image carrier 11 through an opening opened in the developing device 13 when the developing device 13 is mounted at a predetermined position in the main body of the image forming apparatus. Is supplied to the toner carrier 13a. The toner carrier 13a and the supply roller 13h are rotated by a rotation drive mechanism (not shown).

  From the supply roller 13h to the toner carrier 13a where the toner is supplied, on the downstream side in the rotation direction of the toner carrier, to the upstream side in the rotation direction of the toner image carrier from the location where the toner carrier 13a and the image carrier 11 face each other. Is provided with a blade-like toner regulating member 13c for regulating the toner layer on the toner carrier 13a in order to form a toner thin layer on the toner carrier 13a. In the present embodiment, the toner regulating member 13c is brought into contact with the toner conveyed by the rotation of the toner carrier 13a, thereby regulating the toner carried on the toner carrier 13a to a certain amount. At this time, the toner is charged by friction between the toner carrier 13a, the toner regulating member 13c, and the like. The toner regulating member is not limited to the blade shape, and may be a roller.

Next, the configuration of the toner carrier 13a will be described in detail with reference to FIG.
FIG. 6 is an enlarged cross-sectional view of the surface of the toner carrier 13a on the image carrier 11 side. The toner carrying member 13a has a plurality of electrodes 102-1a, 102-1b, 102-2a, 102-2b,... Arranged at predetermined intervals along the toner moving direction on the support base 101, and is further provided thereon. An insulating surface protective layer 103 is laminated. Further, the surface of the surface protective layer 103 functions as a toner transport surface.

As the support substrate 101, an insulating film such as SiO ₂ is formed on a substrate made of an insulating material such as a glass substrate, a resin substrate or a ceramic substrate, or a substrate made of a conductive material such as stainless steel or aluminum. Or a base material made of a material that can be deformed flexibly, such as a polyimide film, can be used.

  The electrode 102 is formed by depositing a conductive material such as Al or Ni—Cr on the support base 101 with a thickness of 0.1 to 10 [μm], preferably 0.5 to 2.0 [μm]. It is formed by patterning into a predetermined electrode shape using a photolithographic technique or the like. In the present embodiment, the width R of the electrode 102 is 1 to 20 times the average particle diameter of the powder (toner).

The surface protective layer 103 is formed of an inorganic or organic insulating material. For example, SiO ₂ , TiO ₂ , TiO ₄ , SiON, BN, TiN, Ta ₂ O _{5 and the} like have a thickness of 0.5 to 10 μm. Preferably, the film is formed with a thickness of 0.5 to 3 [μm].

  FIG. 7 is an external view of the toner carrier 13a in the image forming apparatus according to the embodiment of the present invention. The toner carrier 13a is formed in the shape of a rotating roller, and is an aggregate of odd-numbered electrodes in an electrode pattern composed of a plurality of electrodes 102 that are arranged at a predetermined pitch in the moving direction and are spatially arranged. It has electrode shaft 40A as a first common electrode connected to each electrode in the a-phase electrode. Moreover, it has the electrode shaft 40B as a 2nd common electrode connected to each electrode in b phase electrode which is an aggregate | assembly of an even-numbered electrode.

  In the electrode shaft 40A, a metal rotation shaft member located on one end side in the rotation axis direction of the toner carrier 13a is also used as the first common electrode. Further, the electrode shaft 40B is a member in which a metal rotation shaft member located on the other end side in the rotation axis direction of the toner carrier 13a is also used as the second common electrode. The electrode shaft 40A and the electrode shaft 40B are disposed so as to maintain an insulating state from each other, and are rotatably supported by bearings (not shown).

  An AC voltage is applied to each of the electrode shafts 40A and 40B as a bias potential from power supplies 45A and 45B which are AC power supplies described later by sliding contact members 47A and 47B such as electrode brushes described later. As shown in FIG. 8, the AC voltage is applied to the rectangular wave-shaped a-phase pulse voltage applied to the electrode shaft 40A bundled with the a-phase electrodes and the electrode shaft 40B bundled with the b-phase electrodes. It consists of a rectangular wave-shaped b-phase pulse voltage. These a-phase pulse voltage and b-phase pulse voltage are in opposite phases as shown in the figure, and the average potentials per unit time are the same.

  In addition, since the voltage is applied to the a-phase electrode and the b-phase electrode by shifting the phase by π, this phase difference always causes a potential difference of Vpp between the a-phase electrode and the b-phase electrode. ing. Then, an electric field is generated between the a-phase electrode and the b-phase electrode due to the potential difference, and the toner moves in a reciprocating manner by hopping between the electrodes according to the electric field. This phenomenon is hereinafter referred to as flare (or flare phenomenon). The state causing the flare phenomenon is called flare state. Vpp is set to 100 [V] to 1000 [V]. When Vpp is smaller than 100 [V], the electric field between the electrodes becomes small, and the toner does not hop. Further, when Vpp is larger than 1000 [V], there is a possibility that leakage occurs between the electrodes over time. When a leak occurs, no electric field is generated between the electrodes thereafter, and the toner does not hop. The frequency of the voltage during normal development is 0.1 [kHz] to 10 [kHz]. If the frequency is smaller than 0.1 [kHz], the toner hopping cannot keep up with the developing speed. When the frequency is higher than 10 [kHz], the toner cannot follow the voltage switching. Further, the central value V0 of the voltage is varied between the image portion potential and the non-image portion potential depending on the development conditions. As shown in FIG. 8, the voltage applied to the a-phase electrode and the b-phase electrode has a rectangular wave shape, so that the voltage is switched instantly and is suitable for toner hopping. May be applied.

  Also, as shown in FIG. 9, a rectangular wave pulse voltage is applied to one (a phase electrode) electrode axis, and a DC voltage that is the average potential of the pulse voltage is applied to the other (b phase electrode) electrode axis. Even so, it is possible to cause a flare phenomenon as in the case of employing a pulse voltage having an opposite phase. In this case, since the potential difference between the electrodes is Vpp / 2, the range of Vpp is 200 [V] to 2000 [V]. When voltage application as shown in FIG. 3 is performed, it is not necessary to consider the phase difference between the voltages applied to the a-phase electrode and the b-phase electrode, and the power supply cost is reduced.

  As shown in FIG. 10 (a), the toner carrying member 13a is formed by press-fitting metal electrode shafts 40A and 40B having conductivity into the shaft hole 52 of the cylinder 51 as shown in FIG. 10 (b). 40A and 40B are connected to an a-phase electrode and a b-phase electrode, respectively. As shown in FIG. 11, the a-phase electrode protrudes from the left side of the toner carrier 13a in the drawing and the b-phase electrode protrudes from the right side of the toner carrier 13a, and the a-phase electrode and the b-phase electrode are comb teeth. Electrode configuration. Further, as described above, an AC voltage is applied to the electrode shafts 40A and 40B as a bias potential from the power supply 45A and 45B that are AC power supplies by the sliding contact members 47A and 47B such as electrode brushes.

  In such a configuration, the electrode shaft 40A and the electrode shaft 40B for guiding a common voltage to the same group of electrodes of the plurality of electrodes of the toner carrying roller 31 have a width in consideration of the toner particle size and hopping property. Since it is not necessary to decide, it is possible to use a considerably wide one as shown. Further, the sliding contact members 47A and 47B such as electrode brushes that are rubbed against the electrode shafts can be widened in accordance with the widths of the electrode shafts 40A and 40B. As a result, the timing of occurrence of contact failure due to wear between the electrode shafts 40A and 40B and the sliding contact members 47A and 47B can be delayed as compared with the conventional one, and the life of the developing device can be extended.

  The electrode shaft 40A serving as the first common electrode and the electrode shaft 40B serving as the second common electrode are disposed so as to be shifted from each other in the rotation axis direction in the toner carrier 13a. In such a configuration, the electrode shaft 40A and the electrode shaft 40B are shifted in the rotational axis direction, so that the sliding contact members 47A and 47B are slid independently from the rotating electrode shaft 40A and the electrode shaft 40B, respectively. Can be rubbed.

  In the image forming apparatus according to the present embodiment, the metal electrode shaft 40A located on one end side in the rotation axis direction of the toner carrier 13a is also used as the first common electrode, and the metal located on the other end side. The manufactured electrode shaft 40B is also used as the second common electrode, and these electrode shafts are insulated from each other. In such a configuration, a pulse voltage can be applied independently to each electrode group without providing a new common electrode on the toner carrier 13a.

  In the developing device 13 having such a toner carrier 13a, the toner supplied from the supply unit 13h to the toner carrier 13a rotated clockwise by a rotation driving device (not shown) is thinned by the toner regulating member 13c. Thereafter, a flare (cloud) is formed by the electric field between the electrodes formed on the surface of the toner carrier 13a, and the flare (cloud) is transported to the development region, where the latent image formed on the image carrier 11 is developed. Further, in the developing device 13 of the present embodiment, as shown in FIG. 5, an electrometer 50 is provided on the toner carrier 13a, and the potential of the toner layer in the flare (cloud) state is detected by the electrometer 50. Yes. The toner layer potential in the flare (cloud) state is determined by the charge amount Q / M [μC / g], the toner amount, and the hopping state of the hopping toner. In this embodiment, the amount of layered toner on the latent image carrier is detected using an optical sensor (not shown). By using both the toner amount on the latent image carrier and the toner layer potential, the charge amount Q / M [μC / g] of the toner in the flare (cloud) state can be estimated.

  Conventionally, developing devices used in image forming apparatuses such as copying machines, printers, and facsimiles include a two-component developing method and a one-component developing method. The two-component development method is very suitable for high-speed development, and is the mainstream method for current medium-speed and high-speed image forming apparatuses. In this two-component development method, in order to aim for high image quality, it is necessary to make the state of the developer very dense in the contact portion with the electrostatic latent image on the latent image carrier. For this reason, the carrier particles are currently being reduced in diameter, and on the commercial level, carriers of about 30 [μm] have begun to be used.

  The one-component developing method is the mainstream method of current low-speed image forming apparatuses because the mechanism is small and light. In this one-component development system, toner carried on the surface of a developer carrying member such as a developing roller is used for development without hopping. Specifically, in order to form a toner thin layer on the developing roller, a toner regulating member such as a blade or a roller is brought into contact with the toner on the developing roller, and at that time, the developing roller or the toner regulating member and the toner are in contact with each other. The toner is charged by friction. The charged toner layer formed as a thin layer on the developing roller is carried to the developing unit and develops the electrostatic latent image on the latent image carrier. The one-component development method here is roughly divided into a contact type and a non-contact type. The former is a type in which the developing roller and the latent image carrier are in contact, and the latter is a type in which the developing roller and the latent image carrier are non-contact. It is a contact.

  In order to compensate for the disadvantages of the two-component development method and the one-component development method, there is also a hybrid method in which the two-component development method and the one-component development method are hybridized, as described in Japanese Patent Laid-Open No. 3-100575. Several proposals have been made.

  As a method for developing high-resolution minute uniform dots, for example, there is a method described in Japanese Patent Laid-Open No. 3-113474. In this method, a high-resolution dot developability is realized by installing a wire to which a high-frequency bias is applied to the developing unit, to form a toner cloud in the developing unit, as compared to the hybrid method.

  Japanese Patent Laid-Open No. 3-21967 (Patent Document 1) proposes a method of forming an electric field curtain on a rotating roller in order to form the most efficient and stable toner cloud.

  Japanese Patent Laid-Open No. 2003-15419 discloses a developing device that transports a developer by an electric field curtain using a traveling wave electric field. Japanese Patent Application Laid-Open No. 9-269661 discloses a developing device having a plurality of magnetic poles that attract substantially one layer of carriers almost uniformly on the peripheral surface of the developing roller. Japanese Patent Application Laid-Open No. 2003-84560 discloses that a periodic conductive electrode pattern is provided on the surface of a developer carrying member carrying non-magnetic toner through an insulating portion, and a predetermined bias potential is applied to the electrode. Describes a developing device that generates an electric field gradient in the vicinity of the surface of the developer carrying member and adheres and conveys the non-magnetic toner onto the developer carrying member.

  In the conventional two-component development method, the demand for higher image quality is increasing, and the dot size of the required pixel itself needs to be equal to or smaller than the current carrier particle diameter. In terms of reproducibility, the carrier particles must be further reduced. However, as the carrier diameter is reduced, the permeability of the carrier particles decreases, so that carrier detachment from the developing roller tends to occur, and when the detached carrier particles adhere to the latent image carrier, the carrier In addition to image defects due to the attachment itself, various side effects such as scratching the latent image carrier from the origin are caused.

  In order to prevent this carrier detachment, attempts have been made to increase the magnetic permeability of carrier particles from the material surface and to increase the magnetic force of the magnet included in the developing roller. Development is extremely difficult due to this balance. In addition, due to the downsizing of the developing roller, the developing roller is becoming smaller in diameter, and it becomes difficult to design a developing roller having a strong magnetic field configuration that can completely prevent carrier detachment. Yes.

  In the first place, the two-component development method is a process of forming a toner image by rubbing the ears of a two-component developer called a magnetic brush against the electrostatic latent image. Unevenness tends to occur in the developability. Although an image quality can be improved by forming an alternating electric field between the developing roller and the latent image carrier, it is difficult to completely eliminate the fundamental image unevenness such as the unevenness of the ears of the developer.

  In order to improve transfer efficiency and cleaning efficiency in the step of transferring the developed toner image on the latent image carrier and the step of cleaning the toner remaining on the latent image carrier after the transfer, It is necessary to reduce the non-electrostatic adhesion between the carrier and the toner as much as possible. As a method for reducing the non-electrostatic adhesion force between the latent image carrier and the toner, it is known that reducing the friction coefficient on the surface of the latent image carrier is effective. Since the spikes of the agent smoothly pass through the developing portion, the development efficiency and the dot reproducibility become very poor.

  In the one-component development method, the toner layer on the developing roller thinned by the toner regulating member is sufficiently pressed on the developing roller, so that the toner responsiveness to the electric field in the developing unit is very high. bad. Therefore, in general, in order to obtain high image quality, it is mainstream to form a strong alternating electric field between the developing roller and the latent image carrier. However, even if this alternating electric field is formed, an electrostatic latent image is formed. On the other hand, it is difficult to stably develop a certain amount of toner, and it is difficult to uniformly develop high resolution minute dots. In addition, this one-component development system applies a very large stress to the toner when the toner thin layer is formed on the developing roller, so that the toner circulating in the developing device deteriorates very quickly. As the toner deteriorates, unevenness and the like easily occur in the process of forming a toner thin layer on the developing roller, and the one-component developing method is generally not suitable as a high-speed and highly durable image forming apparatus.

  In the hybrid system (Japanese Patent Laid-Open No. 3-110355), although the size of the developing device itself and the number of parts increase, some problems are overcome. However, the developing unit still has the same problem as the one-component developing method, that is, it is difficult to develop a high-resolution minute uniform dot.

  The method described in Japanese Patent Laid-Open No. 3-113474 can be considered to realize highly stable and high-quality development, but the configuration of the developing device is complicated.

  Moreover, although the method described in JP-A-3-21967 (Patent Document 1) can be interpreted as being extremely excellent for obtaining a small-sized and high-quality development, as a result of intensive studies by the present inventors, In order to obtain an ideal high image quality, it was discovered that the conditions such as the electric field curtain and development to be formed must be limited. In other words, if image formation is performed under conditions that deviate from the appropriate conditions, not only the effect is not obtained, but also poor image quality is provided. In this method, the toner to be hopped on the toner carrier is transported to the development area by moving the surface of the toner carrier. However, the toner is only moved by hopping without moving the surface of the toner carrier. The same can be said for the method described in JP-A-2002-341656.

  In the image forming process in which the first toner image is formed on the latent image carrier and the second toner image and the third toner image are sequentially formed thereon, the latent image carrier is first formed. The developing method must not disturb the toner image formed on the body. Each color toner can be sequentially formed on the latent image carrier by using a non-contact one-component development method or a toner cloud development method described in JP-A-3-113474. In this method, since an alternating electric field is formed between the latent image carrier and the developing roller, a part of the toner is peeled off from the toner image previously formed on the latent image carrier. Get into the device. This not only disturbs the image on the latent image carrier, but also causes a problem that the toner in the developing device is mixed. These are fatal for obtaining high-quality images, and as a method for solving this problem, it is necessary to realize cloud development by a method in which an alternating electric field is not formed between the latent image carrier and the developing roller. .

  As a method for realizing such flare (cloud) development, the methods described in JP-A-3-21967 (Patent Document 1) and JP-A-2002-341656 described above are considered effective. As described above, these methods have no effect unless they are used under appropriate conditions.

  In addition, as in the method described in Japanese Patent Laid-Open No. 2002-341656, a method of eliminating the mechanical driving of the toner carrier and electrostatically conveying and developing the toner by an alternating electric field of three or more phases is also effective. It is believed that there is. However, according to the method described in the publication, the toner accumulates on the transport substrate starting from the toner that can no longer be electrostatically transported due to some cause, resulting in a problem that the toner does not function. In order to solve such a problem, a structure such as a combination of a fixed transport substrate and a toner carrier that moves on the surface thereof has been proposed as in the method described in Japanese Patent Application Laid-Open No. 2004-286837. Becomes very complicated. On the other hand, in the method in which the toner is reciprocated between the electrodes by hopping and conveyed to the development region by moving the surface of the toner carrier, as in the present image forming apparatus, the toner accumulation and the mechanism are complicated as described above. Can be avoided.

  Further, in the developing device of the type in which the toner is separated from the surface of the toner carrier by the electric field between the electrodes and forms a flare (cloud) as in this embodiment, the toner moves by hopping the surface of the toner carrier. The toner and the surface of the toner carrier are in non-contact for most of the time. Therefore, the force with which the toner electrostatically adheres to the surface of the toner carrier is weak. Therefore, even if the developing electric field is set weak (for example, even when the developing potential is 100 [V] or less), there is an advantage that the developing ability can be easily secured. Further, since the electrostatic force between the toner and the surface of the toner carrying member is weak, the toner can be easily peeled off from the surface of the toner carrying member, and the deterioration of the toner can be suppressed. is there.

  Further, by using a developing device that forms a flare (cloud) in an image forming apparatus such as the present embodiment that forms a full color image by superimposing four color toner images, the image is once formed on the image carrier 11. The formed toner image is not affected at all, and the preceding color toner layer formed on the image carrier 11 is not transferred into the developing device 13 for the subsequent color. Therefore, there is no problem such as scavenging (scraping) or color mixing, and an image forming process capable of forming a high-quality image can be stably performed over a long period of time.

  Next, the toner used in this embodiment will be described. As the toner, a toner whose base resin (the main component of the toner) is made of polyester or styrene acrylic and whose normal charging polarity is negative polarity (negative polarity) is used. Then, both the uniformly charged portion (background portion) and the latent image portion of the image carrier 11 have the same polarity (negative polarity in this example) as the normal charging polarity of the toner, and the potential is attenuated more than the background portion. So-called reversal development in which toner is selectively attached to the image portion is performed.

  Here, the toner carrier 13 a in the present embodiment includes a support base 101, a plurality of electrodes 102, and a surface protective layer 103 that covers these electrodes 102. The surface protective layer 103 is made of a material that promotes frictional charging to the normal charging polarity side (minus side in this example) of the toner in accordance with sliding with the toner hopping on the surface of the toner carrier 13a. Can be used. That is, the toner is positioned on the negative side in the triboelectric charging series than the surface protective layer 103. Examples of the material of the surface protective layer 103 that can realize such a relationship include organic materials such as silicone, nylon, melamine resin, acrylic resin, PVA, and urethane. Moreover, a quaternary ammonium salt, a nigusilon type dye, etc. may be sufficient. Furthermore, the material which mixed 2 or more of the material illustrated so far may be used. In addition to promoting frictional charging of the toner toward the normal charging polarity side of the toner, these materials can avoid leakage of toner charge to the electrodes due to its insulating properties.

  In the developing device 13 including the toner carrier 13 a having such a surface protective layer 103, the toner carrier 13 a moves toward the normal charging polarity side of the toner as the surface protective layer 103 of the toner carrier 13 a slides on the hopping toner. Promotes frictional charging. Then, frictional charging to the side opposite to the normal charging polarity of the toner due to rubbing with the surface protective layer 103 is avoided. Thereby, by suppressing the decrease in the toner charge amount (regular charge polarity) due to hopping, it is possible to suppress the development failure due to the toner hopping failure.

  As the toner, a toner whose normal charging polarity is positive polarity (positive polarity) may be used. In this case, the surface protective layer 103 may be made of a material that promotes frictional charging of the toner toward the positive polarity side of the toner as it slides on the toner.

  The toner charging series means a charging series of the whole toner in which an external additive such as silica or titanium oxide is added to the toner base resin (particles). The order in the charging series can be examined as follows. That is, after the toner is rubbed against the surface protective layer for a predetermined time on the surface protective layer, the toner is sucked and collected. Then, the charge amount of the collected toner is measured with an electrometer. If this measurement result indicates an increase in the charge amount of the toner to the negative polarity, the toner becomes a negative charge series with respect to the surface protective layer. Further, if the measurement result indicates an increase in the charge amount of the toner to the positive polarity, the toner becomes a positive charge series with respect to the surface protective layer.

Further, an intermediate layer may be provided between the surface protective layer 103 and the electrode. In this case, as the intermediate _{layer, Ti, Sn, Fe, Cu} , Cr, Ni, Zn, Mg, Al, T i O 2, SnO 2, Fe 2 O 3, Fe 3 O 4, CuO, Cr 2 O 3, It is possible to use a conductive material such as NiO, ZnO, MgO, Al ₂ O ₃ or the like.

  When the latent image on the image carrier 11 is developed using the developing device 13 of the present embodiment as described above, the toner that is hopped on the surface of the toner carrier 13a and is in a flare (cloud) state is the toner carrier. By repeating the collision with the body 13a, the amount of charge is changed or the toner is deteriorated due to stress caused by the collision. Thus, when the toner deteriorates, the latent image on the image carrier 11 cannot be developed satisfactorily. Therefore, in order to achieve high durability of the toner, it is necessary to reduce the stress received by the toner by colliding with the toner carrier 13a.

  For this reason, in the present embodiment, the latent image on the image carrier 11 such as between sheets during continuous printing is not developed by the developing device 13 between the a-phase electrode and the b-phase electrode provided on the toner carrier 13a. The frequency of the voltage applied to is lower than that when the latent image on the image carrier 11 is developed by the developing device 13. As a result, compared to the case where the frequency of the voltage applied between the a-phase electrode and the b-phase electrode is always the same, the number of times that the toner and the toner carrier collide is reduced by decreasing the frequency at the above timing. Thus, the stress applied to the toner by colliding with the toner carrier 13a can be reduced. Below, the verification experiment concerning this is demonstrated.

This experiment was performed using the image forming apparatus according to this embodiment shown in FIG. A belt-shaped organic photoreceptor having a thickness of 13 [μm] was used as the image carrier 11, and laser writing was performed at 1200 [dpi] by the writing device 4 to form a latent image on the image carrier 11. The gap between the toner carrier 13a and the image carrier 11 is 300 [μm], and the toner regulating member 13c is adjusted so that the toner amount on the toner carrier 13a is 0.4 [mg / cm ² ]. . An AC voltage Vpp400 [V] having a frequency of 1 [kHz] is developed between the a-phase electrode and the b-phase electrode with the toner being placed on the toner carrier 13a at 0.4 [mg / cm ² ]. To hop toner on the surface of the toner carrier 13a to form a flare (cloud). During development, a voltage having a frequency of 1 [kHz] is applied with a voltage application time of 1 [kHz] period.

  In addition, between the papers during non-development, the voltage is applied between the electrodes by changing the frequency, voltage application time, and the like to the conditions of Examples 1 to 4 described later with respect to the voltage application conditions during development. Applied. As a comparative example, an experiment was also conducted in which a voltage was applied between the electrodes under the same conditions as the voltage application conditions during development without changing the voltage application conditions between the sheets. Then, 10,000 sheets were continuously printed using the image forming apparatus, and the degree of toner deterioration in each of Examples 1 to 5 and Comparative Example after the 10,000 sheets were printed was determined from the toner remaining in the developing device 13.

  In addition, as voltage application control which applies a voltage between the said electrodes at the time of development at the time of continuous printing and between papers (at the time of non-development), what is shown, for example in FIG. 1 is mentioned. The voltage application control is not limited to that shown in FIG.

  In the voltage application control shown in FIG. 1, first, after continuous printing is started, a control unit (not shown) provided in the main body of the apparatus, such as a CPU and a memory, determines whether or not it is between sheets (during non-development). S1). When it is determined that there is a gap between sheets (Y in S1), the voltage application condition at least one of the voltage frequency lowering or the voltage application time shorter than the voltage application condition at the time of development is satisfied. Change is made (S2). Then, a voltage is applied between the a-phase electrode and the b-phase electrode under the changed voltage application condition (S3). Thereafter, the controller determines whether or not it is during development (S4). If it is during development (Y in S4), the voltage application condition during development is changed (S5). Then, a voltage is applied between the electrodes under the changed voltage application condition (S6). Thereafter, it is determined by the control unit whether or not there is a sheet gap, and the above-described series of control is repeated. If the control unit does not determine that the development is in progress (N in S4), the control unit determines whether or not the continuous printing is finished (S7). If it is determined that the continuous printing is finished (Y in S7), a series of control is finished. If the continuous printing has not ended, it is determined again whether or not it is during development (S4). Note that when the control unit determines the time of development or the interval between sheets (non-development), it can be performed based on image information such as a document or electronic data that is the basis of an image formed by continuous printing. Good.

  Here, the degree of deterioration of the toner is determined by rank evaluation using the external additive surface layer remaining rate indicating how much of the external additive added to the toner surface layer at the time of toner production remains on the toner surface layer. This rank evaluation is classified into five levels. Rank 5 is a state (initial state) at the time of toner production, and the amount of external additive remaining on the toner surface layer decreases as the rank decreases. Reference numeral 1 denotes a state in which no external additive is present on the toner surface layer. It has been found that when the toner deteriorates to rank 1, the toner adheres to the surface of the toner carrying member and the toner cannot be hopped. As the degree of toner deterioration, rank 4 or higher is acceptable in actual use.

Next, voltage application conditions of voltages applied between the a-phase electrode and the b-phase electrode during the continuous printing (non-development) in Examples 1 to 5 and the comparative example are shown.
Example 1: The frequency of the voltage applied between the a-phase electrode and the b-phase electrode between the sheets is set to 0.1 [kHz].
Example 2: No voltage is applied between the a-phase electrode and the b-phase electrode between paper sheets.
Example 3 The application time applied between the a-phase electrode and the b-phase electrode between the papers was changed. That is, as shown in FIG. 12, a voltage having a frequency T1 having a frequency of 1 [kHz] was applied a predetermined number of times during a voltage application time having a frequency T having a frequency of 0.1 [kHz].
Example 4: The frequency of the voltage applied between the a-phase electrode and the b-phase electrode between the papers was increased, and the application time was changed. That is, a voltage having a frequency of 3 [kHz] was applied a predetermined number of times during a voltage application period having a frequency of 0.1 [kHz].
Comparative example: Voltage application control of the voltage applied between the a-phase electrode and the b-phase electrode between the paper is not performed (same conditions as the voltage applied between the electrodes during development).

The experimental results are shown in Table 1.

  As can be seen from Table 1, in Examples 1 to 4, the rank of the degree of toner deterioration is rank 4 or higher, and in the comparative example is rank 3. That is, from the results of Example 1 and Example 2, it can be seen that the toner deterioration can be reduced by lowering the frequency of the voltage applied between the a-phase electrode and the b-phase electrode between the papers than during the development. . Further, from the results of Example 3 and Example 4, the toner deterioration is reduced by shortening the voltage application time during which voltage is applied between the a-phase electrode and the b-phase electrode between the papers. It can be seen that it can be reduced. In summary, the frequency of the voltage applied between the a-phase electrode and the b-phase electrode is lower between the paper than during development, and the voltage application time is shortened as in the comparative example. The number of times the toner collides with the toner carrier 13a is smaller than when the voltage condition applied between the electrodes between the paper is the same as that during development and the toner carrier 13a collides. It can be seen that the stress applied to the toner can be reduced and toner deterioration can be reduced. In Example 4, since the frequency of the voltage between the papers is higher than that during development, the number of collisions between the toner carrier 13a and the toner is likely to increase as compared with the comparative example. It is considered that the number of times of collision between the toner and the toner carrier 13a is smaller than that in the comparative example by shortening the voltage application time for applying the voltage between the electrodes.

  In addition, process control can be performed at the time of non-development in the present invention, that is, between sheets. In this process control, the density of the toner image formed on the image carrier 11 is detected, and the image forming conditions are changed based on the detection result so that a toner image with a predetermined density can be formed. By performing such process control, a toner image having an appropriate density can be formed over time, and stable continuous printing can be performed. Here, by detecting the toner adhesion amount on the image carrier 11 and the toner layer potential in the flare (cloud) state of the toner carrier 13a, the change in the charge amount of the toner in the flare (cloud) state (toner deterioration) The state of the image to be printed can be estimated. Further, the surface of the toner carrier 13a is flared (clouded) based on the result of voltage application control of the voltage applied between the a-phase electrode and the b-phase electrode provided on the toner carrier 13a. It is also possible to predict the state of the toner. For these reasons, the image forming apparatus can suppress the deterioration of the toner and can form an image with high stability by setting the interval between the sheets as a detection timing for reducing the stress of the toner by the voltage application control and controlling the process. Can be obtained.

  For example, as described above, the toner hopped on the surface of the toner carrier 13a and in a flare (cloud) state changes its charge amount by repeatedly colliding with the toner carrier 13a. Therefore, it is possible to estimate the degree of toner deterioration from the change in the toner charge amount. Further, as described above, the charge amount of the toner in the flare (cloud) state can be estimated from the toner adhesion amount on the image carrier 11 and the toner layer potential in the flare (cloud) state of the toner carrier 13a. . Therefore, when it is estimated that the toner charge amount has changed with respect to the initial state based on the toner adhesion amount and the toner layer potential, according to the change, between the electrodes during non-development. By controlling the voltage application such that the frequency of the voltage applied to the toner is lower than that during development or the voltage application time is shorter than that during development, the progress of toner deterioration can be suppressed.

  Further, the following problems can be solved by using the developing device 13 of the present embodiment. That is, if the toner carrier 13a rotates in a flare (cloud) state where toner is hopped on the surface of the toner carrier 13a, toner scattering may occur. During development, since the flare toner is attracted to the latent image by the electric field formed between the latent image formed on the image carrier 11 and the toner carrier 13a, toner scattering is suppressed. At the time of development, since the electric field is not formed, the toner in the flare state is easily scattered by the momentum of rotation of the toner carrier 13a and the airflow accompanying the rotation. Therefore, by performing the above-described voltage application control during non-development as in the developing device 13 of this embodiment, the number of toner hopping times during non-development is reduced, and flare (cloud) state can be suppressed and toner scattering can be reduced. it can.

As described above, according to this embodiment, the plurality of electrodes 102 are arranged at predetermined intervals along the surface of the insulating support base material 101, and the insulating base layer is provided on the surfaces of the support base material 101 and the electrode 102. A cylindrical toner carrier 13a on which a certain surface protective layer 103 is laminated, and a toner charged to a predetermined polarity carried on the surface of the toner carrier 13a by applying a periodic voltage to the plurality of electrodes 102. And an electric power source 45A, 45B which is a hopping electric field generating means for generating an electric field for hopping on the surface of the toner carrier 13a, and an image which is a latent image carrier for the toner carried on the surface of the toner carrier 13a. In the developing device 13 that develops the latent image by transporting it to a developing area facing the carrier 11 and attaching the toner to the latent image on the image carrier 11, non-printing during continuous printing is performed. When an image (sheet interval), has the control unit is a control means for performing to that control short application time of the voltage applied to the upper Symbol plurality of electrodes 102 supply 45A, against 45B than at the time of development The control unit controls the power supplies 45A and 45B so as to apply the voltage of the frequency T1 and the cycle T1 during development, and the frequency T1 and the voltage of the cycle T1 at the cycle T2 during non-development m times each cycle. The power supplies 45A and 45B are controlled to be applied, and the period T1 and the period T2 satisfy the relationship of T1 × m <T2. Thus, the number of collisions between the toner carrier 13a and the toner during non-development can be reduced as compared with the case where a voltage having the same frequency as that during development is applied for the same time during non-development. Therefore, since the number of collisions between the toner carrier 13a and the toner during non-development is reduced, the stress received by the toner due to the collision with the toner carrier 13a is suppressed, and toner deterioration can be reduced.
Further, according to the present embodiment, the frequency range of the voltage applied to the plurality of electrodes 102 by the power supplies 45A and 45B at least during the development is 0.1 [kHz] or more and 10 [kHz] or less. As described above, the hopping state of the toner can be optimized.
Further, according to the present embodiment, the above-mentioned optical sensor, which is a toner adhesion amount detecting means for detecting the adhesion amount of the toner adhered to the latent image on the image carrier 11, and the toner in a hopping state on the surface of the toner carrier 13a. An electrometer 50 which is a toner layer potential detecting means for detecting the potential of the layer, and the control unit includes a detection result of the toner adhesion amount by the optical sensor and a detection result of the toner layer potential by the electrometer 50. By performing the control based on the above, it is possible to suppress the progress of toner deterioration as described above.
In addition, according to the present embodiment, the surface protective layer 103 of the toner carrier 13a has a material having an electrical characteristic capable of imparting to the toner a charge having the same polarity as the normal charging polarity of the toner by friction with the toner. Thus, it is possible to suppress a decrease in toner charge amount (regular charge polarity) due to hopping, and to prevent development failure due to toner hopping failure.
Further, according to the present embodiment, the periodic voltage applied to the plurality of electrodes 102 during the development is such that the average potential value at each moment is the image portion potential and the non-image portion potential formed on the image carrier 11. It is desirable that the value be set to a value between.
In addition, according to the present embodiment, the image bearing member 11 that is a latent image bearing member that bears a latent image and the developing unit that develops the toner by attaching the toner to the latent image on the image bearing member 11 are provided. In an image forming apparatus for forming an image by finally transferring a toner image developed on a carrier onto a transfer material, toner deterioration can be reduced by using the developing device 13 of the present invention as the developing means. Good image formation can be performed over time.
In addition, according to the present embodiment, a plurality of developing devices that store a plurality of colors of toner corresponding to each color are obtained, and a plurality of toner images of each color formed on the image carrier 11 are obtained by superimposing each other. By using the developing device 13a of the present invention with respect to an image forming apparatus that forms a full color image to be formed on the transfer material, the toner image once formed on the image carrier 11 can be completely affected. In addition, the toner layer of the preceding color formed on the image carrier 11 is not transferred into the developing device 13 of the subsequent color. Therefore, there is no problem such as scavenging (scraping) or color mixing, and an image forming process capable of forming a high-quality image can be stably performed over a long period of time.

  The image forming apparatus to which the present invention can be applied is not limited to the one described above. For example, an image carrier is provided corresponding to each color, and a developing device, a charging device, a cleaning device, etc. are provided for each color image carrier, and each color toner image formed by each color image carrier. A so-called intermediate transfer type full-color image forming apparatus that forms a full-color image on the transfer material by transferring the full-color image onto the transfer material from the intermediate transfer member by superimposing the images on the intermediate transfer member. Alternatively, a monochrome image forming apparatus that forms only a black toner image on a transfer sheet may be used. In these cases, the developing device and at least one of the image carrier, the charging device, and the cleaning device are integrally formed and configured as a process cartridge that is detachable from the main body of the image forming device, thereby maintaining the developing device and the like. Improves.

The flowchart which shows an example of voltage application control. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. FIG. 3 is a schematic diagram when the developing device is attached to and detached from the image forming apparatus main body. FIG. 3 is an enlarged view of the vicinity of a developing device in an image forming unit. FIG. 2 is a schematic configuration diagram of a developing device. FIG. 3 is an enlarged cross-sectional view of an image carrier side surface of a toner carrier. FIG. 3 is an external view of a toner carrier. FIG. 4 is a waveform diagram showing characteristics of a pulse voltage applied to an electrode of a toner carrier. FIG. 6 is a waveform diagram when a rectangular wave pulse voltage is applied to one electrode of a toner carrier and a DC voltage is applied to the other electrode. (A) The perspective view of an electrode shaft. (B) Schematic diagram of a toner carrier that serves both as a rotating shaft and an electrode shaft of the toner carrier. FIG. 3 is a development view showing a state in which a toner carrier is developed in a planar shape. The schematic diagram used for description of the change of the application time which applies a voltage between electrodes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Image carrier 13 Developing device 13a Toner carrier 40 Electrode shaft 45 Power source 46 Current measuring device 47 Sliding contact member 50 Electrometer 70 Image forming unit 101 Support base material 102 Electrode 103 Surface protective layer

Claims (7)

A cylindrical toner carrier in which a plurality of electrodes are arranged at predetermined intervals along the surface of the support substrate, and an insulating surface layer is laminated on the surface of the support substrate and the electrodes;
Generation of a hopping electric field that generates an electric field on the surface of the toner carrying member by hopping the toner charged to a predetermined polarity carried on the surface of the toner carrying member by applying a periodic voltage to the plurality of electrodes. Means,
A developing device that develops the latent image by transporting the toner carried on the surface of the toner carrying member to a developing region facing the latent image carrying member and attaching the toner to the latent image on the latent image carrying member. In
During the non-development during continuous printing, and a control means for performing a voltage control system you shorten the voltage application time is being applied to the plurality of electrodes than at the time of development with respect to the hopping electric field generating means,
The control means controls the hopping electric field generating means to apply a voltage having a frequency f1 and a period T1 during the development, and applies a voltage having a frequency f1 and a period T1 to each period m at the period T2 during the non-development. Controlling the hopping electric field generating means to apply each time,
The developing device, wherein the cycle T1 and the cycle T2 satisfy a relationship of T1 × m <T2. The developing device according to claim 1.
A developing apparatus, wherein a frequency range of a voltage applied to the plurality of electrodes by the hopping electric field generating means at least during the development is 0.1 [kHz] or more and 10 [kHz] or less. The developing device according to claim 1 or 2,
Toner adhesion amount detection means for detecting the adhesion amount of toner adhered to the latent image on the latent image carrier;
Toner layer potential detecting means for detecting the potential of the toner layer in a hopping state on the surface of the toner carrier,
The developing device according to claim 1, wherein the control means performs the control based on a detection result of the toner adhesion amount detection means and a detection result of the toner layer potential detection means. The developing device according to claim 1, 2 or 3,
The development, wherein the surface layer of the toner carrier is formed of a material having an electrical property capable of imparting to the toner a charge having the same polarity as the normal charge polarity of the toner by friction with the toner. apparatus. The developing device according to claim 1, 2, 3 or 4,
The periodic voltage applied to the plurality of electrodes during the development is such that the average potential value at each moment is a value between the image portion potential formed on the latent image carrier and the non-image portion potential. A developing device that is set. A latent image carrier for carrying a latent image;
Developing means for developing toner by attaching the toner to the latent image of the latent image carrier,
In an image forming apparatus for forming an image by finally transferring a toner image developed on the latent image carrier onto a transfer material,
An image forming apparatus using the developing device of claim 1, 2, 3, 4 or 5 as the developing means. The image forming apparatus according to claim 6.
A plurality of the developing devices for storing a plurality of color toners in association with each color;
An image forming apparatus, wherein a full color image obtained by superimposing a plurality of toner images of each color formed on the latent image carrier is formed on the transfer material.

Images