JP2010060597A - Developing device and image forming apparatus equipped with the developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that prevents agglomeration of developer and moves the developer stably to a developing section by efficiently and sure stirring of the developer in a developing tank. <P>SOLUTION: The developing device includes a developing tank that stores developer, a developing roller formed from a rubber roller, a supply sponge roller, and a stirring cooperation member located above it. The developing device supplies developer from the developing tank to the developing section, while stirring developer by rotating the stir cooperation member within the developing tank. The developing tank has a coil spring having a spiral structure that is fixed on the stir cooperating member, at lengthwise both ends, below a developer supply port and that differs in coil structure between the end sides and the center side. When the stir cooperating member rotates and is brought into contact with the coil spring, the coil spring causes falling of developer accumulating on the coil spring. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device used in an electrostatic image forming apparatus and an image forming apparatus including the developing device.

  As a developer used in an image forming apparatus adopting an electrophotographic system, a one-component developer composed only of toner and a two-component developer composed of toner and carrier are known.

  In the case of using a two-component developer, the developer composed of toner and carrier is stirred in the developing tank to charge the toner so that the toner adheres to the surface of the carrier. The developer in this state adheres to the outer periphery of the developing roller, and is conveyed to a developing region at a position where the photosensitive drum carrying the electrostatic latent image and the developing roller are opposed to each other. As a result, a sufficient amount of toner can be obtained and a high density image can be obtained.

  However, in the case of using a two-component developer, it is necessary to maintain a constant mixing ratio of the toner and the carrier in order to maintain a constant developing density, and the configuration of the entire developing device including the developing tank is complicated. There is a problem of becoming.

  In addition, when a one-component developer is used, handling is simpler than when a two-component developer is used. As the one-component developer, non-magnetic toner is known, and this non-magnetic toner is conveyed to a nip region between the developing roller and a blade plate that regulates the toner layer thickness. As a result, a toner layer having a constant film thickness adheres to the peripheral surface of the developing roller, and this toner layer is conveyed to a developing region at a position where the photosensitive drum and the developing roller are opposed to each other.

  On the other hand, in recent years, an image forming apparatus employing a color electrophotographic system has become widespread. In this image forming apparatus, for example, a plurality of toner image forming portions that perform charging, exposure, and development processes on the photosensitive drum are arranged in the horizontal direction, and each toner image forming portion is disposed at a position opposite to the photosensitive drum. A transfer conveyance belt for sequentially transferring the recording medium is provided.

  Each toner image forming unit forms toner images of different colors, that is, black, cyan, magenta, and yellow on the photosensitive drum, and these toner images are transferred to a plain paper or an OHP sheet via a transfer conveyance belt. The image is sequentially transferred onto a final recording medium such as the above, or directly transferred onto the recording medium conveyed on the transfer conveyance belt.

  An image forming apparatus in which such toner image forming units are arranged side by side is called a tandem system. This tandem type image forming apparatus has an advantage that the image forming speed is faster than other methods in which a single photosensitive drum is used to superimpose a toner image on paper wound around a transfer drum. Yes. In addition, it is said that the use of the above-described non-magnetic toner, which is a one-component developer, is excellent in terms of high image quality and color compatibility.

In addition, in consideration of environmental issues in recent years, various additions such as wax to improve the releasability from the fixing device, instead of the silicone oil used in the fixing device for fixing the toner on the recording medium. A technique of adding a product to the toner itself is employed.
Further, in a color electrophotographic image forming apparatus, since fixing is performed in a state where toners of two or more colors are superimposed, a toner having higher fixability is required.
In order to save energy, there is a tendency to use a toner having a low average molecular weight that enables fixing at a lower temperature.

  Furthermore, the toner particle size tends to be smaller for the purpose of high resolution. Such recent toner is more likely to aggregate in the developing tank as compared to previous toner. In order to prevent this, the developing tank is provided with a stirring mechanism. However, in a developing tank having a complicated internal structure, there is a dead space that is not sufficiently stirred.

  Further, in general, when printing, the pixels are often concentrated on the center side rather than the end side of the recording paper. Therefore, the toner in the developing tank is often used on the center side, and the toner consumption on the end side is small, and density unevenness tends to occur during printing on the center side and the end side in the developing tank.

  In Patent Document 1, the toner in the toner tank that is long in the vertical direction is stirred efficiently and reliably by contacting the stirring interlocking member provided above the stirring blade and rotating the stirring blade while vertically vibrating. Thus, toner aggregation is prevented.

  Patent Document 2 is composed of a rotating shaft and a conveying blade arranged in a spiral shape. By rotating an agitating and conveying roller having an eccentric rod attached to a peripheral end portion of the conveying blade, toner in the developing tank is removed. Since it is leveled to a flat surface, better image quality can be maintained.

Patent Document 3 discloses a coil spring that constitutes a toner supply roller and an agitating / conveying member in a configuration in which a stirring-and-conveying member including a crank-shaped stainless steel shaft and a coil spring for agitating and conveying toner is disposed in the vicinity of the upper portion of the toner supply roller A uniformizing member made of a thin plate-like elastic film that homogenizes the toner is disposed in the space between the toner and the toner to ensure uniform distribution of the toner and to prevent uneven image density.
JP 2007-334239 A JP 2006-53500 A JP 2006-98738 A

  However, in Patent Document 1, the toner fluidity decreases as the toner is consumed, the toner is clogged at both ends of the coil spring, the toner is not supplied to the stirring interlocking member shaft portion, and the image solid portion is crumpled. A phenomenon occurred.

  In addition, when this coil spring is removed, the toner in the dead space of the developing tank in which the toner is difficult to stir is accumulated on the end of the stir interlocking member shaft, and the remaining torque is detected by the stirring interlocking member shaft torque detection mechanism. Does not work, and a phenomenon of false detection occurs when the toner is low.

  Further, as in Patent Document 2 and Patent Document 3, toner is easily accumulated at the end position of the developing tank only with a crank-shaped stainless steel shaft for stirring and transporting toner and a stirring and conveying member shaft made of a spiral coil spring. Is not enough.

  Furthermore, even if a compression type wire diameter of 1 mm / outer diameter of 12 mm / inner diameter of 10 mm / number of windings of 12 coil springs is provided at both ends in the longitudinal direction of the upper part of the agitating / conveying member shaft, the toner is consumed and the bulk of the toner in the developing tank is reduced. If the amount is reduced, toner accumulates in the coil spring above the stirring / conveying member shaft, and the toner may not be transported to the stirring / conveying member shaft position. It is necessary to ensure both improvement of the stirring mechanism and toner transportability.

  The present invention has been made in consideration of the above-described circumstances, and efficiently and surely loosens the developer in the developing tank, prevents aggregation of the developer, and stably removes the developer. It is an object of the present invention to provide a developing device that can be moved to an image forming apparatus and an image forming apparatus including the developing device.

  In order to solve the above-described problems, a developing device of the present invention includes a developing tank for storing a developer, a developing roller including a rubber roller, a sponge-like supply roller, and an agitation interlocking member on an upper portion thereof. In the developing device that rotates the interlocking member in the developing tank and stirs the developer and supplies the developer from the developing tank to the developing unit, the developer tank has the developer at the upper part of the stirring interlocking member. A coil spring having a spiral structure with different coil structures on the end side and the center side, fixed at both ends in the longitudinal direction below the replenishing port, and when the stirring interlocking member rotates and contacts, The developer deposited on the coil spring is dropped.

A coil having any one of the following shapes is used as the coil having the spiral structure.
(1) A shape having an outer diameter of 8.0 mm to 13.0 mm.
(2) The center side spring pitch in the longitudinal direction is smaller than both end side spring pitches.

  Further, one end on the center side of the coil spring of the spiral structure is fixed, and an expansion / contraction mechanism that can be rotationally driven is attached to the other end, and the expansion / contraction mechanism is rotated in conjunction with the rotation of the stirring interlocking member, The coil spring may be driven to extend and contract in the longitudinal direction.

  In addition, one end on the center side of the coil spring of the spiral structure is rotatably attached, and a rotation mechanism is attached to the other end. The rotation mechanism is rotated in conjunction with the rotation of the stirring interlocking member, and the coil The spring may be driven to rotate.

  Furthermore, a vibration plate is provided on the rear surface of the developing tank, and the vibration plate is resonated in conjunction with the stirring interlocking member so that the developer accumulated on the coil spring is dropped by resonating the coil spring. Also good.

  Further, in the image forming apparatus provided with the above developing device, the same operation and effect as the developing device of the present invention can be achieved.

  According to the present invention, it is possible to efficiently and reliably loosen the developer in the developing tank, prevent aggregation of the developer, and stably move the developer to the developing unit.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a developing device of the invention and an image forming apparatus including the developing device will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a configuration of an image forming apparatus 100 according to the present embodiment. In FIG. 1, the image forming apparatus 100 forms first to fourth developing devices Pa that form toner images on recording paper P. , Pb, Pc, Pd, and laser beam scanner units 27a, 27b, 27c, 27d for exposing the photosensitive drums 22a, 22b, 22c, 22d of the first to fourth developing devices Pa, Pb, Pc, Pd. With.

  A first developing device Pa, a second developing device Pb, a third developing device Pc, and a fourth developing device Pd are juxtaposed in order from the upstream side of the transfer conveying belt 16 in the vicinity of the transfer conveying belt 16. The developing devices Pa, Pb, Pc, and Pd have substantially the same configuration, and the laser beam scanner units 27a, 27b, 27c, and 27d also have the substantially same configuration. For this reason, in the following description, the reference numerals for the description of the same configuration are representative of those of the first developing device Pa and the laser beam scanner unit 27a, and the second to fourth developing devices Pb, Pc, Pd and the laser. Reference numerals corresponding to the beam scanner units 27b, 27c, and 27d are omitted.

  The first developing device Pa is rotationally driven in the direction of arrow F shown in FIG. 1 to form a photosensitive drum 22a on which an electrostatic latent image is formed, a charger 23a that uniformly charges the photosensitive drum 22a, and a photosensitive member. A developing device Pa that develops the electrostatic latent image formed on the drum 22a, a transfer discharger 25a that transfers the developed toner image on the photosensitive drum 22a to the recording paper P, and a photosensitive drum 22a. And a cleaning device 26a for removing residual toner. The charger 23a, the developing device Pa, the transfer discharger 25a, and the cleaning device 26a are sequentially arranged in the periphery along the rotation direction F of the photosensitive drum 22a.

  The laser beam scanner unit 27a is disposed on the upper side of the photosensitive drum 22a, and a semiconductor laser element (not shown) that emits dot light modulated according to image data, and a laser beam from the semiconductor laser element. A polygon mirror 271 for deflecting in the main scanning direction, an axisymmetric aspherical lens (fθ lens) 272 for imaging the laser beam deflected by the polygon mirror 271 on the surface of the photosensitive drum 22a, and a mirror 273 274.

  The laser beam scanner unit 27a has a pixel signal corresponding to the black component image of the color document image, the laser beam scanner unit 27b has a pixel signal corresponding to the cyan component image of the color document image, and the laser beam scanner unit 27c has a pixel signal. The pixel signal corresponding to the magenta color component image of the color original image is input to the laser beam scanner unit 27d, and the pixel signal corresponding to the yellow color component image of the color original image is input thereto.

  Thereby, electrostatic latent images corresponding to the color-converted document image information are formed on the respective photosensitive drums 22a, 22b, 22c, and 22d. The developing device Pa contains black toner, the developing device Pb contains cyan toner, the developing device Pc contains magenta toner, and the developing device Pd contains yellow toner. The electrostatic latent images on the photosensitive drums 22a, 22b, 22c, and 22d are developed with the toners of these colors. Thus, the document image information color-converted by the image reading unit is reproduced as a toner image of each color.

  A sheet adsorbing charger 28 is disposed between the first developing device Pa and the paper feeding mechanism 11, and the sheet adsorbing charger 28 charges the surface of the transfer conveyance belt 16. The recording paper P supplied from the paper feeding mechanism 11 is transported without deviation between the first developing device Pa and the fourth developing device Pd in a state in which the recording paper P is reliably adsorbed on the transfer transport belt 16.

  Further, a static eliminator 29 is disposed between the fourth developing device Pd and the fixing device 17 and substantially directly above the drive roller 14. An AC current for separating the recording paper P electrostatically attracted to the transfer conveyance belt 16 from the transfer conveyance belt 16 is applied to the static eliminator 29.

  In the image forming apparatus of the present embodiment, cut sheet-like paper is used as the recording paper P. When the recording paper P is fed out from the paper feeding cassette and supplied into the guide of the paper feeding / conveying path of the paper feeding mechanism 11, its leading end is detected by a sensor (not shown) and output from this sensor. Based on the detected signal, the pair of registration rollers 12 are temporarily stopped.

  This recording paper P is fed onto the transfer conveyance belt 16 rotating in the direction of the arrow Z in FIG. 1 at the timing of each developing device Pa, Pb, Pc, Pd. At this time, the transfer conveyance belt 16 is charged by the sheet adsorbing charger 28 as described above, so that the recording sheet P is stable while passing through the developing devices Pa, Pb, Pc, Pd. Then transported.

  In each developing device Pa, Pb, Pc, Pd, a toner image of each color is formed, and each toner image is superimposed on the recording paper P that is electrostatically adsorbed by the transfer conveyance belt 16 and conveyed. When the transfer of the image by the fourth developing device Pd is completed, the recording paper P is peeled off from the transfer conveyance belt 16 by the static eliminator 29 sequentially from the leading end portion thereof and guided to the fixing device 17. Finally, the recording paper P on which the toner image is fixed is discharged onto a paper discharge tray 20 from a paper discharge port (not shown).

  In the image forming apparatus of the present embodiment, optical writing is performed by scanning the laser beam by the laser beam scanner unit 27a and exposing the photosensitive drum 22a. However, instead of the laser beam scanner unit 27a, the laser beam scanner unit 27a performs optical writing. A writing optical system (LED head) composed of a light emitting diode array and an imaging lens array may be used. The LED head is smaller than the laser beam scanner unit 27a, has no moving parts, and is silent. Therefore, it is suitable for a tandem image forming apparatus that requires a plurality of optical writing units.

  FIG. 2 is a schematic diagram showing the first developing device Pa in the image forming apparatus of the present invention. Since the other second to fourth developing devices Pb, Pc, and Pd have the same configuration, description thereof is omitted.

  Around the photosensitive drum 22a, the charger 23a for charging the surface potential of the photosensitive drum 22a to be constant at −500 V, the photosensitive drum 22a is exposed, and the electrostatic latent image is transferred to the photosensitive drum 22a. A laser beam scanner unit 27a (not shown) formed on the surface is brought into contact with the photosensitive drum 22a in the nip region, and the toner is supplied to the photosensitive drum 22a to be formed on the surface of the photosensitive drum 22a. A developing roller 34a, which is a toner carrier for developing the electrostatic latent image, and a cleaning device 26a for removing the toner remaining on the surface of the photosensitive drum 22a are arranged along the rotation direction F of the photosensitive drum 22a. Are sequentially arranged.

  The photosensitive drum 22a includes a conductive substrate made of metal or a synthetic resin material, an undercoat layer formed on the surface of the conductive substrate, and a photosensitive layer formed on the surface of the undercoat layer, as shown in the figure. It is configured to rotate in the direction of F.

The developing roller 34a is configured to rotate in the direction E shown in the drawing. This rotation is realized by a rotation drive unit 38a including a power source such as a motor and a power transmission mechanism including gears and the like.
The developing roller 34a has a conductive support as a center and the periphery thereof is covered with an elastic body. The elastic body is formed from a rubber material having conductivity and elasticity by adding a conductive agent such as carbon black. Examples thereof include urethane rubber, silicone rubber, and NBR (Nitrile-Butadiene Rubber) rubber. The elastic body of the present embodiment, it is assumed that the volume resistivity is formed by for example 5 × 10 ⁶ Ωcm polyurethane rubber.

  On the surface of this elastic body, a coat layer forming the surface layer of the developing roller 34a is provided. Since this coat layer is a layer that carries toner, toner transportability, toner filming prevention, abrasion resistance, toner chargeability to a predetermined polarity, adhesion to an elastic body, and elastic body machinery The material is selected such that the follow-up property to the mechanical deformation is good. For example, materials such as nylon or vinyl, urethane resin, silicone resin, fluorine-containing resin are suitable, and the coating layer uses these synthetic resins as the base material, and ensures conductivity with materials that promote charging with toner. For example, it is coated on an elastic body by performing a treatment such as dispersing carbon.

The hardness of the developing roller 34a is preferably 50 to 90 degrees in Asker C, and the volume resistivity is preferably 10 ⁴ to 10 ⁸ Ωcm. When the volume resistivity is 10 ⁶ to 10 ⁷ Ωcm, the characteristics of the developing roller 34a are best.
A supply roller (sponge) 35a for supplying toner to the developing roller 34a is disposed in contact with the developing roller 34a, and the toner layer thickness on the surface of the developing roller 34a is regulated, and the toner The doctor blade 36a, which is a regulating member for charging the battery, is also disposed in contact with the doctor blade 36a.

The supply roller 35a is a conductive elastic foam roller having a diameter of 20 mm made of a conductive urethane foam having a volume resistivity of about 10 ⁵ Ωcm, a cell density of 80 to 140 pcs / inch, and an Asker C hardness of 60 degrees to an Asker C hardness of 30 degrees. is there.

  The doctor blade 36a uses a thin plate-like spring member such as stainless steel or phosphor bronze and is brought into contact with the developing roller 34a so as to apply a required pressure contact force. As a contact method, a counter contact method is employed in which the free end is positioned upstream of the fixed end in the rotation direction of the developing roller 34a.

  The toner used in the image forming apparatus as described above is fine particles having an average particle diameter of 7 to 10 μm. As a method for producing such fine particles, a so-called pulverization method in which a resin, a colorant or the like is melt-kneaded and then pulverized and classified is generally used. In addition, a toner manufacturing method called a wet method has been proposed. In this wet method, a monomer (monomer) in which a colorant or an additive is dispersed in an aqueous medium in the presence of a dispersion stabilizer. There are a suspension polymerization method, an emulsion polymerization method, a phase inversion emulsification method and the like for polymerization.

Examples of the binder resin material used for the toner include styrene resins such as polystyrene or polystyrene-acrylic acid ester copolymers, vinyl chloride resins, phenol resins, epoxy resins, polyester resins, polyether polyol resins, polyurethane resins or 1 type (s) or 2 or more types chosen from groups, such as polyvinyl butyral resin, may be used.
The binder resin material may be one in which crystalline waxes or incompatible substances are finely dispersed in advance from the synthesis stage.
However, among the binder resin materials described above, polyester resins or polyether polyol resins are excellent in thermal properties such as resin elasticity, and therefore it is desirable to use them for the binder resin material.

  The glass transition point temperature (Tg) of the polyester resin or the polyether polyol resin is suitably in the range of 50 to 90 ° C. from the viewpoint of the thermal fixability and storage stability of the toner. The number average molecular weight (Mn) of the polyester resin or polyether polyol resin is suitably in the range of 3,000 to 100,000. When it is less than 3,000, it is difficult to form particles, and when it is 100,000 or more, it is not preferable because it becomes high viscosity during phase inversion emulsification and affects the control of particle diameter and distribution. .

The colorant used in the toner is not particularly limited as long as it is a variety of dyes and pigments that have been used as toner materials so far, and is organic or inorganic as shown below. Various dyes and pigments can be used.
That is, examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline / black, activated carbon, nonmagnetic ferrite, magnetic ferrite, and magnetite.

  Yellow colorants include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, nablue yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow Examples of the compound include GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake.

  Examples of the orange colorant include compounds such as red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G or indanthrene brilliant orange GK.

  Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, virazolone red, watch red, calcium salt, lake red C, lake red D, brilliant carmine 6B, Examples include eosin lake, rhodamine lake B, alizarin lake or brilliant carmine 3B.

  Examples of purple colorants include compounds such as manganese purple, fast violet B, and methyl violet lake.

  Examples of the blue colorant include compounds such as bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated product, first sky blue or indanthrene blue BC.

  Examples of the green colorant include compounds such as chromium green, chromium oxide, pigment green B, micalite green lake, and final yellow green G.

  Examples of the white colorant include compounds such as zinc white, titanium oxide, antimony white, and zinc sulfide.

  In the toner for developing the electrostatic latent image, components such as magnetic powder such as magnetite, hematite or various ferrites, an anti-offset agent, or a charge control agent can be blended as necessary in addition to the above materials.

  The offset preventive agent used for the purpose of improving the fixing property of the toner is not particularly limited as long as it has been used as a toner material so far, and those shown below can be used. For example, petroleum wax such as paraffin wax, oxidized paraffin wax or microcrystalline wax, mineral wax such as montan wax, animal and plant wax such as beeswax or carnauba wax, or polyolefin wax (such as polyethylene or polypropylene), Examples thereof include synthetic waxes such as oxidized polyolefin wax or Fischer-Tropsch wax. These offset inhibitors may be used alone or in combination of two or more.

  As the charge control agent, various substances from low molecular compounds to high molecular compounds can be used. For example, a quaternary ammonium salt compound, a nigrosine compound, an organometallic complex, a chelate compound, and a monomer having an amino group are homopolymerized. Alternatively, copolymerized polymer compounds and the like can be mentioned.

  In addition, inorganic fine powders such as silica fine powder, titanium oxide fine powder, and alumina fine powder are preferably used as the external additive or fluidizing agent added for the purpose of charge adjustment and surface resistance adjustment. These inorganic fine powders are made of silicone varnish, various modified silicone varnishes, silicone oils, various modified silicone oils, silane coupling agents, silane coupling agents having functional groups, and other organosilicons for hydrophobicity and chargeability control. It may be treated with a treating agent such as a compound. Moreover, 1 type, or 2 or more types chosen from the processing agent mentioned above may be used.

Further, as other additives, for example, a lubricant such as polytetrafluoroethylene, zinc stearate, polyfluorinated vinylidene, or silicone oil particles (containing about 40% silica) is preferably used.
Further, a small amount of white fine particles having a polarity opposite to that of the toner particles may be used as a developability improver.

By the way, in the tandem type image forming apparatus as described above, since the developing devices Pa to Pd are arranged close to each other, in order to accommodate a large amount of developer in the developing devices Pa to Pd, the developing devices It is necessary to make the developing tank of Pa to Pd vertically long.
In such a vertically long developing tank, a dead space in which the developer is not sufficiently stirred is generated with only one stirring blade as in the prior art.

Therefore, in this embodiment, as shown in FIG. 2 and FIG. 3, two types of stirring means are provided in the longitudinal direction to efficiently and reliably stir the developer in the developing tank, The aggregation of the developer is prevented.
2 is a cross-sectional view showing the internal structure of each of the developing devices Pa to Pd, and FIG. 3 is a cross-sectional view taken along the longitudinal direction as viewed from the direction A of the developing device Pa.

  In FIG. 2, the developer tank 39 for containing the developer has a stirring interlocking member 40 provided on the upper portion of the supply roller 35a, and has a structure on the end side and the center side at both ends in the longitudinal direction of the upper portion of the stirring interlocking member 40. Two helical springs 41 having different structures are provided.

  As shown in FIG. 3, the agitation interlocking member 40 has a structure in which a metal crank-shaped stainless steel shaft having a total length of about 330 mm and a coil spring are provided outside the shaft. Further, a gear 48 that is a drive transmission member is provided at one end portion (left end portion in FIG. 3) of the shaft, and by rotating the drive transmission member by an external force, the stirring interlocking member 40 is rotated to develop the developing tank. The toner in 39 is agitated.

When the replenishing port 45 is viewed from the top of the developer replenishing tank 44, it has a generally rectangular shape as shown in FIG. 4, and reinforcing ribs 46 are provided at these three locations to provide four openings (A to D). ).
The two spiral coil springs 41 are each about 70 mm in length, and are arranged so as to be below the openings (A and D) at both ends of the four openings of the supply port 45. Each end is fixed to the fixing member 47, and the other end is also fixed to the developing tank 39 (FIG. 3).

The developer in the developer replenishing tank 44 is dropped and replenished from the replenishing port 45 to the lower developing tank 39 as a developer stirring sheet (not shown) wound around the developer replenishing tank 44 rotates.
At this time, the developer (near the openings B and C in FIG. 4) in the center of the developer supply tank 44 falls straight, but the developer supplied from the openings A and D is temporarily coil springs. Falls on 41.

  The shaft of the agitation interlocking member 40 rotates along the rotation trajectory indicated by the dotted line in FIG. 2, and contacts the coil springs 41 provided at both ends of the developing tank 39 when the shaft reaches the uppermost position. The developer supplied from the A and D portions of 45 is stirred in two stages by the coil spring 41 and the stirring interlocking member 40 and then conveyed to the supply roller 35a.

  The coil spring 41 having the above-described spiral structure is assumed to have the following shape as shown in FIG.

(1) The longitudinal outer diameter of the helical coil spring 41 is 8 mm or more and 13 mm or less, and the center side wire diameter is larger than the both end side wire diameters (FIGS. 5A and 5B).
For example, the center side wire diameter is 1 mm, the outer diameter is 8.5 mm, the both end side wire diameters are 0.5 mm, and the outer diameter is 12.5 mm.
By forming the coil spring 41 having a spiral structure in such a shape, the developer is transferred to the left and right end portions on the longitudinal center side where the outer diameter is small and the wire diameter is large, and both ends having a large outer diameter and a small wire diameter are transferred. In this portion, the developer is prevented from accumulating inside the coil spring 41.

  For this reason, since the developer in the developing tank 39 is homogenized, the rotational force of the agitation interlocking member 40 is not wasted, and it is not necessary to significantly increase the rotational force of the agitation interlocking member 40. Further, the coil spring 41 does not hinder the rotation of the stirring interlocking member 40 or stops the rotation, and can always loosen the developer.

(2) The spring pitch on the center side in the longitudinal direction of the helical coil spring 41 is made smaller than the spring pitch on both ends (FIG. 5C).
For example, the center side spring pitch is 6 mm, and the both end side spring pitch is 8 mm.
By forming the spiral coil spring 41 in such a shape, the developer is transferred to the left and right end sides on the longitudinal center side where the spring pitch is small, and development is performed inside the coil spring 41 at both end portions where the spring pitch is large. The function that the agent does not accumulate occurs.

  For this reason, since the developer in the developing tank 39 is homogenized, the rotational force of the agitation interlocking member 40 is not wasted, and it is not necessary to significantly increase the rotational force of the agitation interlocking member 40. Furthermore, since the coil spring 41 does not hinder the rotation of the stirring interlocking member 40 or stop the rotation, the aggregation of the developer can always be loosened.

  The above-described helical spring coil spring 41 is fixed at both ends, but may be provided with an expansion / contraction mechanism or a rotation mechanism at the end on the developing tank 39 side.

(3) Coil spring 41 having a helical structure provided with a telescopic mechanism:
As shown in FIG. 6, the expansion / contraction auxiliary coupler 50 is provided with a gear 51 as a drive transmission member, and is connected to the gear 48 of the stirring interlocking member 40 by a belt 52.
By rotating the gear 48 of the agitation interlocking member 40 by an external force, this rotational force is transmitted to the gear 51, so that the expansion / contraction auxiliary coupler 50 is hooked or detached from the end of the helical coil spring 41. The coil spring 41 is expanded and contracted.
By extending and contracting the coil spring 41 in the longitudinal direction in this way, the developer that tends to accumulate inside the coil spring 41 is loosened and the developer is smoothly transferred to the lower agitation interlocking member 40. Will not occur.

(4) Coil spring 41 having a spiral structure including a rotation mechanism:
As shown in FIG. 7, the rotation shaft 53 is provided with a gear 51 as a drive transmission member, and is connected to the gear 48 of the agitation interlocking member 40 by a belt 52. One end of the coil spring 41 is fixed to the rotating shaft 53, and the other end of the coil spring 41 is rotatably held.
By rotating the gear 48 of the agitation interlocking member 40 by an external force, this rotational force is transmitted to the gear 51, and the rotating shaft 53 rotates the coil spring 41 having a spiral structure.

  By constantly rotating the coil spring 41 in this way, the developer that tends to accumulate inside the coil spring 41 is loosened, and the developer is smoothly transferred to the lower agitation interlocking member 40. It will not occur and there will be no false detection of the remaining toner sensor.

Further, a vibration plate 43 (see FIG. 2) is provided on the back of the agitation interlocking member 40 and the spiral coil spring 41 (outside of the developing tank 39 opposite to the developing roller 34a) to apply vibration to the developing tank 39. The developer in the helical coil spring 41 may be loosened.
For example, a diaphragm EE20A-63A resonance frequency 6.3 KHZ maximum input voltage 30 Vp-p manufactured by FDK Corporation is used for the diaphragm 43, and the stirring interlocking member 40 has a predetermined rotation speed (for example, 10 rotations). The main body device that has received the toner detection signal causes the vibration plate 43 to resonate for a predetermined time (for example, 1 second).
When the coil spring 41 having a helical structure resonates due to this resonance motion, the developer in the coil spring 41 is loosened and thus does not accumulate, and the developer is smoothly transferred to the lower agitation interlocking member 40. Thus, normal image quality is maintained until the remaining amount of toner is reduced.

Next, it will be shown through the following experiment that the above-described helical spring coil spring 41 improves the stirring property and the conveyance property, which are the problems of the present invention.
The stirrability of the developer is investigated through the following two experimental items.
(1) The image density on the end side and the center side is examined, and when the difference is small, the developer is regarded as being stirred.
(2) Check whether the supplied toner is uniformly diffused.

The developer transportability is investigated through the following two experimental items.
(3) Investigate whether the toner bulkiness at the end and the center is uniform.
(4) The amount of toner remaining when the absence of toner is detected is investigated.

  Next, the structure of two helical coil springs attached to both ends in the major axis direction in each experimental example and the conventional example will be described (see Table 1). These two springs shall have the same structure.

<Conventional example>
A helical coil spring having an outer diameter of 12 mm, an inner diameter of 10 mm, a wire diameter of 1 mm, and a pitch of 6 mm is used (FIG. 8).

<Experimental example 1>
A spiral coil spring having an outer diameter of 12 mm, an end-side wire diameter of 0.5 mm, a center-side wire diameter of 1 mm, and a pitch of 6 mm is used.

<Experimental example 2>
A spiral coil spring having an outer diameter of 12.5 mm on the end side, an outer diameter of 8.5 mm on the center side, a wire diameter of 1 mm, and a pitch of 6 mm is used.

<Experimental example 3>
A spiral coil spring having an outer diameter of 12 mm, an inner diameter of 10 mm, a wire diameter of 1 mm, an end side pitch of 8 mm, and a center side pitch of 6 mm is used.

<Experimental example 4>
Using a spring with an outer diameter of 12 mm, an end side wire diameter of 0.5 mm, a center side wire diameter of 1 mm, and a pitch of 6 mm, an extension coupler is attached to the end of the helical coil spring, It is attached so that the helical coil spring can be extended and contracted.

<Experimental example 5>
A spiral coil spring with an outer diameter of 12 mm, an end side wire diameter of 0.5 mm, a center side wire diameter of 1 mm, and a pitch of 6 mm is used so that the spiral coil spring rotates in conjunction with the agitation interlocking member shaft. To do.

<Experimental example 6>
Using a spiral coil spring with an outer diameter of 12 mm, an inner diameter of 10 mm, a wire diameter of 1 mm, an end side pitch of 8 mm, and a center side pitch of 6 mm, the diaphragm is operated so as to operate in conjunction with the drive signal of the agitation interlocking member shaft. Install.

Next, an experimental method will be described.
Coil springs with spiral structure corresponding to the experimental example and the conventional example described above are mounted on a modified Sharp color complex machine ARC260, and a document with a 30% printing rate that is uniform in the longitudinal direction of the developer tank (streaks) is used. Thus, 1,100 sheets are copied in the continuous printing mode.
After copying, the image density of the solid image on the center side and the end side is measured using a Macbeth densitometer (RD-900, manufactured by Sakata Inx Engineering).

Further, the developing tank and the developer supply tank are separated, and a scaled metal rod is inserted from the upper part of the developing tank toward the stirring interlocking member shaft to measure the toner bulkiness on the center side and the end side.
Next, when the developing tank and the developer replenishing tank are returned to their original positions, the developing tank is filled with regular yellow toner, a small amount of black toner is charged on the end side, and 10 continuous solid images are printed. Count the number of sheets when the black toner spreads evenly and becomes gray as a whole.

  Finally, using a 30% coverage linear document that is uniform in the longitudinal direction of the developing tank, continuously printing until it is detected that the amount of toner is low, and the weight of toner when the amount of toner remaining is displayed is measure. The weight of this toner is calculated by subtracting the empty weight of the developing device (the weight of only the device without toner) and the weight of the waste toner from the current weight of the developing device (the remaining toner and the total weight of the device).

  The results of the experimental example and the conventional example investigated by the above method are as shown in Table 2.

  Next, criteria for determining whether or not there is an effect on the task will be described. In addition, the symbol shown below indicates whether or not there was an effect on the task, “×” indicates no effect, “△” indicates that the effect is the same as in the past, and “○” indicates that the effect is slightly recognized but is optimal. However, “◎” indicates that the effect was sufficient.

For stirring properties,
(1) Image density of the solid image on the center side and the end side:
(Image density of center-side solid image) − (Image density of end-side solid image) is calculated, and the smaller this value, the more uniformly the developer is stirred.
As for this value, 0.2 or more is evaluated as “×”, 0.1 to 0.2 as “Δ”, 0.05 to 0.1 as “◯”, and 0.05 or less as “◎”.

(2) Toner diffusion:
When the regular yellow toner is filled in the developing tank, a small amount of black toner is charged on the edge side, and 10 continuous solid images are printed, the smaller the total number of gray images, the more the toner becomes. It shows that it was stirred.
When this number is not uniform at the 10th sheet, “X”, when it becomes uniform at the 10th sheet, “△”, when it becomes uniform at the 8th sheet, “○”, when it becomes uniform at the 6th sheet Evaluate as “◎”.

For transportability,
(3) Toner bulkiness:
(Center-side toner bulkiness) − (End-side toner bulkiness) is calculated, and the smaller this value, the more uniform the bulkiness of the toner deposited in the longitudinal direction, which indicates better transportability and fluidity. .
When this value is 10 mm or more, it is evaluated as “X”, 5 to 10 mm as “Δ”, 2.5 to 5 mm as “◯”, and 2.5 mm or less as “」 ”.

(4) Remaining toner:
When it is displayed that the remaining amount of toner is low, the supplied developer is transported to the developing unit as the remaining toner weight decreases.
A toner remaining amount of 50 g or more is evaluated as “x”, 33 g to 50 g or less as “Δ”, 25 g to 33 g or less as “◯”, and 25 g or less as “◎”.

  Summarize the evaluation of each experimental item above. If there is an “×”, “X”, if there is “△”, “△”, if there is more than half of “○”, “○”, “◎” If there are more than half, the overall evaluation is “◎”.

  Table 3 summarizes the evaluation results for the above conventional examples and examples. As a result, Experimental Examples 4 to 6 were evaluated as “◎”, confirming the effectiveness of the coil spring having the helical structure of the present invention.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and corrections can be made without departing from the scope of the present invention. For example, the present invention can be applied not only to an image forming apparatus that forms a color image but also to an image forming apparatus that forms only a monochrome image. Further, the present invention can be applied to any developing device having any structure as long as it has a stirring member for stirring the developer in the developing tank.

1 is a longitudinal sectional view illustrating a configuration of an embodiment of an image forming apparatus of the present invention. FIG. 2 is a cross-sectional view showing an internal structure of the developing device of FIG. 1. It is a figure which shows the installation position of the stirring interlocking member and the coil spring of a helical structure. It is a figure which shows the shape of a supply port. It is a figure which shows the shape of a coil spring. It is a figure which shows the coil spring provided with the expansion-contraction mechanism. It is a figure which shows the coil spring provided with the rotation mechanism. It is a figure which shows the shape of the conventional coil spring of a helical structure.

Explanation of symbols

P: recording paper, Pa to Pd: first to fourth developing devices, 100: image forming apparatus, 11: paper feeding mechanism, 12: registration roller, 14: driving roller, 15: driving roller, 16: transfer conveyance belt, DESCRIPTION OF SYMBOLS 17 ... Fixing device, 20 ... Paper discharge tray, 22a-22d ... Photoconductor drum, 23a-23d ... Charger, 25a-25d ... Transfer discharger, 26a-26d ... Cleaning device, 27a-27d ... Laser beam scanner unit 271: Polygon mirror, 272: Non-axisymmetric aspherical lens (fθ lens), 273, 274 ... Mirror, 28: Charger for sheet adsorption, 29: Charger, 34a-34d ... Developing roller, 35a-35d ... Supply Roller (sponge roller), 36a ... Doctor blade, 38a ... Rotation drive unit, 39 ... Developing tank, 40 ... Shaking interlocking member shaft, 41 ... Co Le spring, 43 ... diaphragm, 44 ... developer supply tank, 45 ... supply port, 46 ... rib, 47 ... fixing member, 48 ... gear, 50 ... auxiliary coupler for expansion / contraction, 51 ... gear, 52 ... belt, 53 ... Axis of rotation.

Claims (7)

A developer tank containing a developer, a developing roller composed of a rubber roller, a sponge-like supply roller, and an agitation interlocking member on the top thereof, and the developer is rotated by rotating the agitation interlocking member in the developer tank. In the developing device for supplying the developer from the developing tank to the developing unit while stirring,
The developer tank is provided with a spiral coil spring having different coil structures on the end side and the center side, which is fixed at both ends in the longitudinal direction below the developer supply port at the upper part of the stirring interlocking member,
The developing device, wherein the coil spring causes the developer deposited on the coil spring to fall when the stirring interlocking member rotates and contacts.   2. The developing device according to claim 1, wherein the coil having the spiral structure has an outer diameter of 8.0 mm or greater and 13.0 mm or less.   2. The developing device according to claim 1, wherein the coil having the spiral structure has a shape in which a center side spring pitch in a longitudinal direction is smaller than both end side spring pitches. 3.   4. The developing device according to claim 1, wherein one end on the center side of the helical coil spring is fixed, and another end is provided with a telescopic mechanism that can be driven to rotate. A developing device characterized in that the expansion and contraction mechanism is rotated in conjunction with rotation to drive the coil spring to expand and contract in the longitudinal direction.   4. The developing device according to claim 1, wherein one end on the center side of the helical coil spring is rotatably attached, and a rotation mechanism is attached to the other end to rotate the stirring interlocking member. A developing device characterized in that the rotating mechanism is rotated in conjunction with the rotating mechanism to drive the coil spring to rotate.   6. The developing device according to claim 1, wherein a vibration plate is provided on a rear surface of the developing tank, and the vibration plate is resonated in conjunction with the stirring interlock member to resonate the coil spring. A developing device that drops developer deposited on a coil spring.   An image forming apparatus comprising the developing device according to claim 1.

Images