JP2010072409A - Developing device having mechanism for supplying carrier, image forming method, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that maintains the initial developing performance for an extremely long time without requiring time and effort for developer replacement, is free from fog and streak, and has high reproducibility for thin lines; and to provide an image forming method and an image forming apparatus that use the developing device and facilitate maintenance management. <P>SOLUTION: The developing device using at least two-component developer composed of toner and carrier includes: a mechanism that determines the deterioration in the carrier of the two-component developer; a mechanism that separates the deterioration carrier; a mechanism that discharges the deterioration carrier; a mechanism that returns non-deterioration carrier; and a mechanism that supplies developer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device having a mechanism for determining a deterioration state of a carrier, an image forming method using the developing device, and an image forming device.

  Currently, in an image forming apparatus (for example, a copying machine) using an electrostatic latent image developing method such as an electrophotographic method, a developing device using a two-component developer composed of a carrier and a toner is widely used.

  In such a developing device, the toner is consumed by development, but the carrier remains in the developing device without being consumed and is used for a long time. Therefore, stirring with the toner in the developing device causes peeling of the resin coating layer on the surface of the carrier and adhesion of the toner resin, additives, and the like to the surface, and the charge imparting ability of the carrier gradually decreases. It will be. Therefore, the developer containing the above carrier is periodically replaced.

  When the developer is periodically replaced as described above, the carrier immediately before replacement is significantly less functional than the carrier at the beginning of replacement, which greatly improves the image quality at the beginning and immediately before replacement of the carrier. Will change. In addition, the periodic developer replacement work involves removing the old developer from the developing device and filling it with unused developer. At the same time, if the toner in the developing device rises up, a problem in environmental hygiene occurs. Therefore, in order to eliminate such inconvenience, a trickle-type developing device has been proposed in which the carrier in the developing device is gradually discarded while the unused carrier is gradually replenished.

As a typical example of the above-mentioned trickle-type developing device, for example, as disclosed in Patent Literature 1 and Patent Literature 2, an unused developer is gradually replenished from the developer replenishing device to the developing device. On the other hand, there is known a system in which the developer in the developing device that has become excessive due to the replenishment is discharged from the developer discharge port by overflow and collected in a developer collection container. In such a developing device, the charge imparting ability of the developer deteriorates from when the developer is filled with unused developer until a certain period of use elapses. The unused carrier is gradually replenished and the old carrier is gradually discharged, so that the carrier becomes stable and almost constant.
Japanese Patent Publication No. 2-21591 Japanese Utility Model Publication No. 60-2596

  However, in the trickle-type developing device, when attention is paid to individual carrier particles of the developer in use, there are carriers that are not so deteriorated and carriers that are considerably deteriorated. This depends on the difference in durability of each carrier particle and the period of staying in the developing device, the degree of deterioration due to stirring in the developing device, the regulating means when forming the developing layer on the developing roller before development, or the development This is considered to be because the progress of deterioration varies from particle to particle due to the difference in load applied by the subsequent developer peeling means.

  In the trickle method, since the deteriorated carrier and the undegraded carrier are discharged without being separated, the carrier that has not deteriorated so much is discharged in the same manner as the deteriorated carrier. In order to compensate for this, it was pointed out that it was necessary to supply up to the carrier that had not deteriorated, and there was a lot of waste.

  Furthermore, since the deteriorated carrier is not selectively discharged, unless a considerably large amount of new carrier is supplied more than necessary, the deterioration level of the carrier in the entire developer cannot be kept low, and the carrier is charged with toner. The performance becomes lower than the initial stage, fogging and the like occur, and the image quality deteriorates. From the standpoint of printing durability, it is difficult to achieve this because of a problem in terms of cost because the developer replacement ratio must be increased in order to maintain high image quality.

  Furthermore, most of the carriers currently used are so-called resin-coated carriers in which a resin coating layer is provided on the surface of magnetic particles. In recent years, there is a type of carrier in which the resin coating layer on the surface of the carrier is gradually scraped to extend the service life. However, in the trickle method, the peeled product of the resin coating layer is gradually removed from the carrier that has been used for a long time in the developing device. When the peeled material adheres to the developing sleeve, image unevenness such as a streak failure defect is caused, which also causes a problem.

  The present invention has been made to solve the above problems.

  That is, the object of the present invention is to eliminate the need for developer replacement, maintain the initial development performance for a very long time, no fogging or streak failure, and a high reproducibility of fine lines, It is an object of the present invention to provide an image forming method and an image forming apparatus that use the image forming method and can easily maintain and manage.

  As a result of intensive studies, the present inventors have found that the object of the present invention can be achieved by adopting the following configuration.

(1)
In a developing device using a two-component developer comprising at least a toner and a carrier,
A mechanism for determining the deterioration state of the carrier of the two-component developer;
A mechanism for separating the deteriorated carrier;
A mechanism for discharging the deteriorated carrier,
A mechanism for returning undegraded carriers;
A mechanism for replenishing developer;
A developing device comprising:

(2)
The developing device according to (1), wherein the mechanism for determining the deterioration state of the carrier detects and determines a change in the shape of the carrier.

(3)
The developing device according to (1) or (2), wherein the mechanism for determining the deterioration state of the carrier detects and determines a change in the charge amount of the carrier.

(4)
An image forming method, wherein an image is formed using the developing device according to any one of (1) to (3).

(5)
An image forming apparatus that forms an image using the developing device according to any one of (1) to (3).

  According to the present invention, it is possible to maintain the initial developing performance for a very long period of time without requiring the need for replacement of the developer, and there is no development of fog or streak failure, and a developing device with high fine line reproducibility, and the same are used. It is possible to provide an image forming method and an image forming apparatus with high image quality and easy maintenance.

  The present invention will be further described.

[Developing method used in the present invention]
First, an embodiment of a developing device that can be used in the present invention will be described with reference to FIG. FIG. 1 is an enlarged cross-sectional view of the developing device of the present invention. Note that the illustrated arrows in FIG. 1 indicate the rotation direction of each roller, and the double arrows indicate the developer conveyance direction.

  First, in the present invention, the developing device has a meaning that is often used in the past, and refers to a mechanism or apparatus of a part that originally contributes to development. On the other hand, the developing device includes the developing unit, and further adopts a mechanism for judging the deterioration state of the carrier, a mechanism for separating the deteriorated carrier, a mechanism for discharging the deteriorated carrier, and a non-deteriorated mechanism. A device including a mechanism for returning the carrier and a mechanism for supplying a new developer is also referred to.

  In FIG. 1, the developing device 14 has a developing sleeve 141 disposed so as to face the photosensitive surface of the photosensitive drum 10 having an outer diameter of 100 mm, for example.

  In the color image forming apparatus, as shown in FIG. 4 to be described later, the normal developing unit 14 contains yellow (Y), magenta (M), cyan (C) and black (K) two-component developers. Is installed. Each of the photosensitive drums 10 and the developing sleeve 141 is provided at a developing position while maintaining a predetermined gap with respect to the circumferential surface of the photosensitive drum 10.

  The developing device 14 which is a developing device for each color is configured as follows.

  In the developing device 14, 140 is a developing device housing that is a developer containing portion that contains a two-component developer composed of toner and carrier, 142 is a magnet roll that is magnetic field generating means having a fixed magnetic pole, and 141 is a magnet inside. A developing sleeve that is a developer conveying member having a roll 142, 143 is a layer thickness regulating member that is a layer thickness regulating means made of a magnetic material that regulates the developer layer thickness on the developing sleeve 141 to a predetermined amount, and 148 is a magnet on the back surface A developer removing plate having a plate 148a, 145 is a conveyance supply roller, and 146 and 147 are a pair of stirring screws.

  The layer thickness regulating member 143 that is a layer thickness regulating means is made of, for example, a rod-like or plate-like magnetic stainless steel disposed at a predetermined gap from the developing sleeve 141, and is a two-component developer layer on the circumferential surface of the developing sleeve 141. Regulate thickness.

  The developer removing plate 148 is provided to face the magnetic pole N2 of the magnet roll 142, and the development on the developing sleeve 141 is caused by the action of the repulsive magnetic field of the magnetic poles N2 and N3 and the magnet plate 148a provided on the back surface of the removing plate 148. Remove the agent.

  The transport supply roller 145 transports the developer peeled off by the removal plate 148 to the stirring screw 146 and supplies the developer stirred by the stirring screw 146 to the layer thickness regulating member 143. Reference numeral 145A denotes a blade portion that is provided on the conveyance supply roller 145 and conveys the developer.

  The agitating screws 146 and 147 rotate at a constant speed in opposite directions to agitate and mix the toner and the carrier in the developing device 14 to obtain a two-component developer that uniformly contains a predetermined toner component.

  The developer replenished in the developer housing 140 from the developer replenishment port opened to the top plate 140A of the upper portion of the developer housing 140 at the upper portion of the agitator screw 147 rotates at a constant speed in mutually opposite directions. , 147, and agitated and mixed with the developer contained in the developing device housing 140 to form a uniform developer, and the developer is conveyed to the layer thickness regulating member 143 by the conveyance feeding roller 145 rotating, and the layer thickness regulating member A predetermined layer thickness is set by 143, and the developer layer of the two-component developer is stably supplied onto the outer peripheral surface of the developing sleeve 141 by the receiving member 144. The developer that has developed the latent image on the photosensitive drum 10 is peeled off by the action of the repulsive magnetic field of the magnetic poles N 2 and N 3 and the magnet plate 148 a provided on the back surface of the removal plate 148, and again the agitating screw 146 by the transport supply roller 145. It is conveyed to. The electrostatic latent image on the photosensitive drum 10 is reversely developed, for example, in a non-contact state by applying a developing bias voltage in which an alternating current (AC) bias AC1 is superimposed on a direct current (DC) bias E1 as necessary.

  Conventionally, a two-component developer composed of a non-magnetic toner having an average particle diameter of several μm and a magnetic carrier having an average particle diameter of several tens of μm is used for the developing device. The developer used in the present invention includes a toner having a volume median diameter of 2.5 to 7.5 μm, preferably 3.0 to 6.5 μm, and a carrier having a mass average particle diameter of 20 to 60 μm, more preferably 25 to 45 μm. A two-component developer consisting of

  In a normal developing device, only the toner is supplied when the toner concentration detection sensor 149 shown in FIG. 1 detects that the toner concentration in the developing device housing 140 is lower than a predetermined toner concentration. As shown in FIG. 4, in the image forming apparatus, the toner supplied to the developing device 14 is replenished into the developing device 14 from the hopper 200 </ b> D serving as a supply unit through the developer transport path 300. A developer screw is provided inside the developer conveyance path 300 to convey the developer. There is no developer outlet.

  In the trickle type developing device, as described above, the unused carrier (new carrier) is supplied together with the unused toner (new toner) from the hopper 200D. The amount of developer in the developer housing 140 is increased by replenishing new developer composed of unused toner and unused carrier. Correspondingly, the discharge unit discharges the two-component developer whose developer amount has risen above the specified level because it becomes excessive from the amount corresponding to the specified amount of the two-component developer in the developer housing 140. A developer discharge port).

  On the other hand, the developing device used in the present invention has, for example, the configuration shown in FIG.

  That is, the developer is taken out from the developer discharge port of the developing device 14, and is first separated into unnecessary substances such as a carrier, toner, and a carrier film peeled off. Although this mechanism is not indispensable in the present invention, it is preferable to install the mechanism in order to operate the mechanism to be changed later, and to effectively reuse the separated toner.

  Next, the carrier is sent to a deterioration judging mechanism, and further separated into a carrier that cannot withstand future use (deteriorated carrier) and an undegraded carrier that can withstand sufficient use (undegraded carrier). Is discarded. Both the undegraded carrier and the previously separated toner, if possible, are returned to the developing unit 14 and again used for development, but new toner and new carrier are replenished by the amount of toner and deteriorated carrier consumed by development. As a result, the ratio between the carrier and the toner in the developer and the total amount of the developer can be returned to the initial use state. In addition, since it is possible to use a means for removing unnecessary materials together with the deteriorated carrier, even if it is used continuously for a very long time, it may cause an increase in fog, occurrence of streak failure, image quality deterioration of fine line reproducibility, etc. Absent.

  As a means for separating the carrier, toner and waste in FIG. 2, for example, there is a method using air through a mesh.

  Further, the separation is not necessarily performed in one stage, and may be performed in a plurality of stages. Further, for example, a method may be used in which the carrier is first separated using magnetism or the like, and then the toner and the waste are separated.

  In the deterioration determination mechanism, a method using a shape measuring device such as FPIA 3000 can be used to determine the shape, and a charge amount detection method can be a method in which a carrier having a high charge amount is attached to the charged sheet and separated.

  Further, for example, if there is a means capable of simultaneously performing a plurality of mechanisms such as a mechanism for judging a deteriorated carrier, a mechanism for separating and a mechanism for discharging, it may be performed simultaneously, and there is a means for switching the recovery path depending on the deterioration state.

  Next, as an example of a specific method, FIG. 3 shows a conceptual diagram of means for performing a deterioration determination / separation mechanism by a charge amount detection method.

  The undegraded carrier is positively charged immediately after being separated from the toner, and the deteriorated carrier is less positively charged than the undegraded carrier due to current leakage.

  FIG. 3 is a conceptual diagram of an apparatus for judging deterioration and separating unnecessary materials using the above-described characteristics. Individual particles dropped from the upper part of the apparatus by free fall follow Fleming's law by the action of an electric field provided in the cylindrical drop path, undegraded carriers are on the base potential side, and degraded carriers are relatively precious. The course can be changed to the potential side. The most deteriorated carrier falls straight according to gravity. Degraded / undegraded carrier separation has been completed by preparing a storage box in the part where each deteriorated / undegraded carrier falls below the cylindrical drop path where an electric field is applied. become.

  In addition, since unnecessary materials such as a peeled resin that could not be removed in the carrier separation step and the toner separation step are not charged, they fall into a storage box in which deteriorated carriers are stored. The deteriorated carrier and unnecessary matter contained in the container-like container are discharged through a discharge mechanism, and the undegraded carrier is returned to the developing device.

[Mode of Color Image Forming Apparatus Implementing the Present Invention]
FIG. 4 shows an example of a color image forming apparatus incorporating the developing device of the present invention (however, the configuration of the entire developing device of the present invention is not shown). FIG. 4 shows a so-called tandem color image forming apparatus in which a plurality of image forming bodies are arranged in parallel, and the configuration and function are as follows. Of course, the image forming apparatus in which the developing device of the present invention can be incorporated is not limited to the one shown in FIG. 4, and may be an image forming apparatus for forming a monochrome image or a color image forming apparatus. The structure which is not taken may be sufficient.

  In the color image forming apparatus shown in FIG. 4, four sets of process units 100 made of yellow (Y), magenta (M), cyan (C), and black (K) are provided on the peripheral edge of the transfer belt 14a as an intermediate transfer member. The single color Y, M, C, and K toner images formed by each process unit 100 are superimposed and transferred on the transfer belt 14a, and the transferred color toner image is a transfer material. It is configured to be collectively transferred onto a recording sheet, fixed and discharged outside the apparatus.

  10 is a photosensitive drum as an image forming body for each color, 11 is a scorotron charger as charging means for each color, 12 is an exposure optical system as image writing means for each color, 14 is a developing device for each color, A cleaning device 190 is a cleaning unit for the photosensitive drum 10 for each color.

  The photosensitive drum 10 which is an image forming body for each color has an organic photosensitive layer (OPC) provided with an overcoat layer (protective layer) on the outer periphery of a cylindrical metal base formed of, for example, an aluminum material. The photosensitive drum 10 is formed on the outer periphery of the metal substrate, rotates with the movement of the transfer belt 14a brought into contact, and the photosensitive drum 10 for each color rotates in the direction indicated by the arrow in the figure in a grounded state.

  The organophotoreceptor layer has a two-layer structure that is functionally separated into a charge generation layer (CGL) mainly composed of a charge generation material (CGM) and a charge transport layer (CTL) mainly composed of a charge transport material (CTM). The photoreceptor layer. The organic photoreceptor layer may have a single layer structure containing a charge generation material (CGM) and a charge transport material (CTM) in one layer, and the single layer structure or the two layer structure of the photoreceptor layer. Usually contains a binder resin.

  The scorotron charger 11 serving as a charging means for each color has the same polarity as the toner (toner at the time of development) used by the control grid and the corona discharge electrode respectively held at a predetermined potential (negative polarity in this embodiment). The corona discharge causes a charging action (minus charging in the present embodiment) to give a uniform potential to the photosensitive drum 10. As the corona discharge electrode of the scorotron charger 11, other sawtooth electrodes or needle electrodes can be used.

  In the exposure optical system 12, which is an image writing unit for each color, the exposure position on the photosensitive drum 10 is located downstream in the rotation direction of the photosensitive drum 10 with respect to the aforementioned scorotron charger 11 for each color. In this way, it is arranged around the photosensitive drum 10. The exposure optical system 12 image-exposes the photosensitive layer of the photosensitive drum 10 according to the image data of each color read by a separate image reading device and stored in the memory, and electrostatic latent image is formed on the photosensitive drum 10 for each color. Form an image.

  The developing device 14 which is the developing means for each color maintains a predetermined gap with respect to the peripheral surface of the photosensitive drum 10 as already described with reference to FIG. 1, and rotates in the direction shown in the figure with respect to the photosensitive drum 10, for example. It has a developing sleeve 141 formed of a cylindrical nonmagnetic stainless steel or aluminum material having a thickness of 0.5 to 1 mm and an outer diameter of 15 to 25 mm. Yellow (Y) and magenta (M ), Cyan (C) and black (K) two-component developers. The developing unit 14 is maintained at a predetermined gap, for example, 100 to 500 μm, with a photoreceptor roller 10 by a not-shown abutting roller, and a developing bias obtained by superimposing a DC voltage or a DC voltage and an AC voltage on the developing sleeve 141. By applying the toner, the developer carried on the peripheral surface is brought into a stand-up state and contact reversal development is performed to form a toner image on the photosensitive drum 10.

  In addition, the development unit including the developing unit 14 selects the “new toner + new carrier” and “undegraded carrier” supply ports, whose outline is shown in FIG. 2, and the “undegraded carrier” in the developing unit. The developing device of the present invention shown in a configuration in which a mechanism for doing so is incorporated is used.

  On the photosensitive drum 10 uniformly charged by the scorotron charger 11, image exposure is performed by the exposure optical system 12 to form an electrostatic latent image, and development is performed by the developer 14 to form a toner image. . The toner image is transferred onto a transfer belt 14a described later at the transfer position. The transfer residual toner remaining on the drum after the transfer is cleaned by a cleaning device 190 that collects the toner.

The transfer belt 14a in which the Y, M, C, and K process units 100 face each other in parallel is an endless belt having a volume resistivity of 10 ¹² to 10 ¹⁵ Ω · cm. For example, modified polyimide, thermosetting polyimide, ethylene tetrafluoro A conductive material is dispersed in engineering plastics such as ethylene copolymer, polyvinylidene fluoride, nylon alloy, etc., on the outer side of a semiconductive film substrate having a thickness of 0.1 to 1.0 mm, preferably as a toner filming prevention layer. This is a seamless belt having a two-layer structure and having a fluorine coating of 5 to 50 μm. As the substrate of the transfer belt 14a, a semiconductive rubber belt having a thickness of 0.5 to 2.0 mm in which a conductive material is dispersed in silicon rubber or urethane rubber can also be used. The transfer belt 14a is stretched so as to circumscribe the drive roller 14d, the driven roller 14e, the tension roller 14k, and the backup roller 14j, and when the image is formed, the drive roller 14d is rotated by being driven by a drive motor (not shown). The transfer belt 14a is pressed against the photosensitive drum 10 by the pressing elastic plate 14b disposed on the upstream side of the transfer position for each color, and the transfer belt 14a is rotated in the direction indicated by the arrow in the drawing. At this time, the photosensitive drum 10 is driven to rotate by receiving the driving force of the transfer belt 14a following the movement of the transfer belt 14a.

  The primary transfer device 14c, which is a transfer means for each color, is preferably composed of a corona discharge device, and is provided to face the photosensitive drum 10 for each color with the transfer belt 14a interposed therebetween, and is connected to the transfer belt 14a and each color. A transfer area (no symbol) for each color is formed between the photosensitive drum 10 and the photosensitive drum 10. A DC voltage having a polarity opposite to that of the toner (in this embodiment, a positive polarity) is applied to the primary transfer device 14c for each color, and a transfer electric field is formed in the transfer area, so that the color on the photosensitive drum 10 is changed. The toner image is transferred onto the transfer belt 14a.

  The static eliminator 14m serving as a static eliminator for each color is preferably a corona discharger and neutralizes the transfer belt 14a charged by the primary transfer unit 14c.

  A pressing elastic plate 14b, which is a pressing means for the transfer belt, is formed of a rubber blade such as urethane and is disposed upstream of the transfer position for each color, and presses the transfer belt 14a against the photosensitive drum 10 during image formation. The photosensitive drum 10 is rotated following the movement of the transfer belt 14a.

  When the image recording is started, the photosensitive drum 10 of the black (K) image forming unit 100 is rotated in the direction indicated by the arrow in the drawing by the start of the not-shown photosensitive member driving motor, and at the same time, the charging action of the K scorotron charger 11 is performed. As a result, application of a potential to the K photoconductor drum 10 is started.

  After the potential is applied to the K photoconductor drum 10, image writing is started by the K exposure optical system 12 using an electrical signal corresponding to the first color signal, that is, the K image data. An electrostatic latent image corresponding to the K image of the original image is formed on the surface of the image.

  The latent image is subjected to reversal development in a contact state by a K developing device 14, and a black (K) toner image is formed in accordance with the rotation of the K photosensitive drum 10.

  The K toner image formed on the K photoconductive drum 10 as an image forming body by the image forming process described above is the primary transfer of K as the first transfer means in the K transfer area (no symbol). The image is transferred onto the transfer belt 14a by the device 14c.

  Next, the transfer belt 14 a is synchronized with the C toner image, and a potential is applied by the charging action of the C scorotron charger 11 by the cyan (C) image forming unit 100. Is written by an electric signal corresponding to the color signal of C, that is, the C image data, and the C toner image is transferred onto the C photosensitive drum 10 by the reversal development of the contact by the C developing device 14. In (no symbol), a C toner image is superimposed on the K toner image by the C primary transfer device 14c as the first transfer means.

  A similar process is used to synchronize with the superposed toner images of K and C, and the M image by the third color signal formed on the M photoconductor drum 10 by the magenta (M) image forming unit 100. The M toner image corresponding to the data is transferred from the above K and C toner images to the M toner by the M primary transfer device 14c serving as the first transfer means in the M transfer area (no sign). A fourth image formed on the Y photosensitive drum 10 by the yellow (Y) image forming unit 100 is formed by superimposing the images, and synchronized with the superimposed toner images of K, C, and M. The Y toner image corresponding to the Y image data based on the color signal is transferred to the above K, C, and M by the Y primary transfer device 14c as the first transfer means in the Y transfer area (no sign). Y toner image from the top of the toner image Is formed by overlapping, K, C, color toner image overlay M and Y are formed on the transfer belt 14a.

  The transfer residual toner remaining on the peripheral surface of the photosensitive drum 10 for each color after the transfer is cleaned by a cleaning device 190 which is a cleaning unit for the image forming body for each color.

  The recording paper P is the second transfer means from the paper feed cassette 15 as the transfer material storage means through the timing roller 16 as the transfer material feeding means in synchronization with the formation of the superimposed color toner image on the transfer belt 14a. The secondary transfer device 14g is transported to the transfer area (no sign) of the secondary transfer device 14g and applied with a DC voltage having a polarity opposite to that of the toner (in this embodiment, a positive polarity). The alignment color toner image is transferred onto the recording paper P at once.

  The recording paper P to which the color toner image has been transferred is neutralized by a neutralizing electrode 16b which is a separating means comprising a sawtooth electrode plate, conveyed to the fixing device 17, and heat is transferred between the fixing roller 17a and the pressure roller 17b. After the toner image on the recording paper P is fixed by applying pressure, the toner image is discharged to a tray outside the apparatus.

  The transfer residual toner remaining on the peripheral surface of the transfer belt 14a after the transfer is cleaned by a cleaning device 190a which is a transfer belt cleaning unit provided opposite to the driven roller 14e with the transfer belt 14a interposed therebetween.

  The developing device 14 which is a developing unit for each color accommodates the above-described two-component developers of yellow (Y), magenta (M), cyan (C) and black (K), respectively. A developing sleeve 141 that rotates at a developing position as shown in FIG. 1 while maintaining a predetermined gap with respect to the peripheral surface is provided.

  As described above, the developing device of the present invention described with reference to FIG. 2 is used for the developing device including the developing device 14 which is the developing means for each color. The developer in the hopper 200D is supplied to the developing device 14 by the rotation of a supply roller provided at the lower end of the hopper 200D.

  Further, a mesh is used as a means for separating the carrier from the developer in the developing device. In order to separate the undegraded carrier and the deteriorated carrier of the carrier, separation by the shape measuring device (FPIA 3000) and the charge amount shown in FIG. The device was used together.

  Using the above image forming apparatus, the output of actual prints was output up to 2 million sheets, and the degree of image defects such as fogging and streak failure was compared with a trickle type image forming apparatus. The results were good and the amount of replenished carrier was clearly small.

  The image forming apparatus equipped with the developing device having the configuration of the present invention does not need to replace the two-component developer completely, and suggests the possibility that service such as developer replacement by a service person can be unnecessary. To do. The above results show the results for the C (cyan) image, but the Y, M, C, and K toners have similar results.

  Therefore, the developer in the developing unit 14 is always withdrawn, not to mention the normal developing method in which the toner is replenished and the developer is not removed from the developing unit, and this must be discarded. Compared to the trickle development method, the development method of the present invention does not generate a discarded carrier other than the deteriorated carrier, and has drastically reduced maintenance and no need for environmental pollution countermeasures with a waste developer, and has a significantly superior performance. It is clear.

[Recording material]
The recording material used in the present invention is a support for holding a toner image, and is usually called an image support, a transfer material or a transfer paper. Specific examples include various kinds of transfer materials such as plain paper from thin paper to thick paper, coated printing paper such as art paper and coated paper, commercially available Japanese paper and postcard paper, plastic films for OHP, and cloth. However, it is not limited to these.

FIG. 3 is an enlarged cross-sectional view illustrating an example of a developing device that can be used in the present invention. 1 is a configuration diagram showing an example of a developing device used in the present invention. The block diagram of an example of the mechanism which isolate | separates and discharges a deteriorated carrier. 1 is a configuration diagram of a tandem color image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photosensitive drum 14 Developing device 140 Developing device housing 141 Developing sleeve as developer conveying member 142 Magnet roll as magnetic field generating means 143 Layer thickness restricting member as layer thickness restricting means 145 Conveying supply roller 146 Stir screw 147 Stir screw 148 Developer removal plate having a magnet plate on the back

Claims (5)

In a developing device using a two-component developer comprising at least a toner and a carrier,
A mechanism for determining the deterioration state of the carrier of the two-component developer;
A mechanism for separating the deteriorated carrier;
A mechanism for discharging the deteriorated carrier,
A mechanism for returning undegraded carriers;
A mechanism for replenishing developer;
A developing device comprising: The developing device according to claim 1, wherein the mechanism for determining the deterioration state of the carrier detects and determines a change in the shape of the carrier. 3. The developing device according to claim 1, wherein the mechanism for determining the deterioration state of the carrier detects and determines a change in the charge amount of the carrier. An image forming method comprising forming an image using the developing device according to claim 1. An image forming apparatus that forms an image using the developing device according to claim 1.

Images