JP2006201474A - Developing device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device with which a developer recovered by a trickle development system can be again supplied to a developing unit and can be reused and the occurrence of trouble accompanying temporarily housing the recovered developer can be eliminated, and an image forming apparatus using the same. <P>SOLUTION: The developing device (14) has the developing unit (30) which houses the developer (2) containing at least toner and a carrier and conveys the developer while circulating the developer up to a developer carrier, a replenishing means (5) which houses the developer (2A) for replenishment for replenishing the developer for replenishment to the developing unit and a recovering means (7) which discharges and recovers a portion of the developer to be housed in the developing unit, mixes the recovery developer (2B) to be recovered with the developer for replenishment existing in the replenishing means and sends the mixture into the replenishing method so as to reuse the same. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a developing device that uses a developer containing toner and a carrier and collects a part of the developer, and an image forming apparatus such as a printer, a copying machine, and a multifunction machine using the developer, and particularly collects the developer. The present invention relates to a developing device and an image forming apparatus that employ the reuse of a developer.

  In an image forming apparatus such as a printer that forms an image made of toner on a recording medium such as recording paper by applying an electrophotographic method or an electrostatic recording method, for example, a latent image formed on a photoconductor according to image information is developed. When a two-component developer containing toner and carrier is used as a developer for this purpose, if image formation is repeated, the chargeability of the two-component developer tends to gradually decrease.

  Conventionally, in order to solve such a problem, for example, a developer supply cartridge that can be replaced is loaded into the developer unit, and a developer including a carrier in addition to toner is supplied to the developer unit. A developing device that collects a part has been proposed (Patent Document 1).

Also, as shown in FIG. 11, the applicant also holds a plurality of developing devices a (a1 to a4) on a rotating body b, and sequentially develops each color by facing the photoconductor c by the rotation of the rotating body b. As the rotary developing device d for performing the above, each developer unit a is replenished with the necessary developer f from the developer replenishing means e, while excess developer g in each developer unit a is supplied to the rotating body b. The thing which discharges using the change of the action direction of gravity by rotation is proposed (patent document 2).
JP-A-6-308829 JP 9-218575 A

  However, in a developing device employing a so-called trickle developing method and an image forming apparatus equipped with the developing device, a developer including a carrier is supplied to the developing device and a part of the developer in the developing device is discharged. There are the following problems.

  In other words, the developer recovered by the trickle development method is in a relatively good state in which the carrier in the developer is not deteriorated compared to the carrier in the developer in the developer that does not employ the trickle development method. is there. Nonetheless, this point has not been focused on in the past, and the developer (particularly the carrier) to be collected is temporarily stored in a dedicated collection box or the like and then comes to a developing device or a predetermined time. It was handled that it was taken out from the image forming apparatus, and was not effectively used. In fact, for a developer in a developing device that does not employ this trickle developing method, an At value (a value expressed by the formula “(toner density + coefficient) × charge amount”) indicating a deterioration index of the developer is “400” in the initial stage. ”And decreased to“ about 100 ”at the stage after the continuous image formation (development operation) of 200,000 sheets, whereas the developer recovered in the developing device adopting the trickle development method However, the deterioration index at the stage after the continuous image formation of 200,000 sheets was reduced only to “about 250”, which was an acceptable level.

  In general, an installation space such as a collection box for temporarily storing the collected developer must be secured in the image forming apparatus, which is an obstacle to downsizing the apparatus. On the other hand, for example, in the developing device described in the above-mentioned Patent Document 1, a configuration is provided in which a cylindrical container for storing the collected developer is disposed in the internal space of the toner supply cartridge. Therefore, the amount of the original storage space (volume) in which the replenishment developer for the cartridge is to be accommodated is reduced by the amount of the cylindrical container, and the initial filling amount of the replenishment developer becomes pseudo. Further, in the rotary developing device d described in the above-mentioned Patent Document 2, a collection box j is secured by dividing a part of the storage space of the developer cartridge h that stores the replenishment developer f by a partition plate i. In this case, however, the original storage space (volume) k for storing the replenishment developer f is reduced by an amount that secures the storage space for the collection box j, and the initial filling amount of the replenishment developer f is reduced. I'm under pressure.

  Incidentally, in Patent Document 1, it is proposed to provide a developer recirculation device that recirculates the carrier overflowed by replenishment of the developer containing the carrier from the developing device to the toner replenishment cartridge side. However, the developer reflux device is for temporarily storing and holding the refluxed carrier on the cartridge side, and is intended to be reused by mixing with a new carrier for replenishment in the cartridge. Not in.

  The present invention has been made in view of the above problems and the like, and mainly the developer (mainly carrier) recovered by the trickle development method can be supplied again to the developing device and reused. It is an object of the present invention to provide a developing device and an image forming apparatus using the same that can eliminate the occurrence of problems associated with temporarily storing the collected developer.

  The developing device of the present invention contains a developer containing at least a developer including toner and a carrier and transporting the developer while circulating the developer to a developer carrier, and a replenishment developer for replenishing the developer. A replenishing means for storing and replenishing the developer for replenishment to the developing device; and a part of the developer accommodated in the developing device is discharged and recovered, and the recovered developer recovered is supplied to the replenishing means. And a collection unit that feeds the replenishment developer so as to be reused after being mixed with the existing replenishment developer.

  According to this developing device, the collected developer including the carrier recovered from the developing device by the collecting means is sent to the supplying means, mixed with the replenishing developer, and supplied to the developing device again. It will be reused. Further, it is not necessary to secure an installation space for installing a recovery box that temporarily stores the recovered developer. For example, in the rotary developing device described in the above-mentioned Patent Document 2, it is not necessary to secure a space for a recovery box in a part of the developer cartridge, and as a result, a developer for replenishment of the cartridge is obtained. The problem that the initial filling amount is pressed is also solved.

  In the developing device, the replenishing means is provided with a stirring member that stirs the replenishing developer and the recovered developer. This agitating member is obtained by adding an agitating member that exerts an agitating action to the conveying member when the replenishing means is already provided with a conveying member that rotates and sends the developer for replenishment to the discharge port side. There may be.

  When this stirring member is provided, the recovered developer is well and reliably stirred and mixed with the replenishment developer, and is resupplied to the developing device again in a state where the recovered developer becomes uniform by the stirring. As a result, good development can be performed stably.

  Further, each of the developing devices has a replenishing unit that rotates and replenishes the replenishment developer, and a replenishment mechanism that increases the rotation speed of the delivery mechanism according to the toner concentration of the developer. And a control unit.

  Here, the toner concentration of the developer means the toner concentration of the replenishment developer in the replenishment means. The toner concentration may be grasped by directly measuring the toner concentration of the replenishment developer (including the one mixed with the recovered developer) present in the replenishment means. The reference patch toner image is formed, the image density is measured, and when the measured value at that time falls below a predetermined value, the toner density of the replenishment developer is considered to be lowered (predictive judgment), Alternatively, the pixel value (number of pixels) of image information may be cumulatively counted, and this may be grasped by assuming that the toner concentration of the replenishment developer has decreased when the count value reaches a predetermined value.

  When such a delivery mechanism and a replenishment control unit are provided, the collected developer whose toner density is starting to decrease due to use and the (initial) replenishment developer are mixed, and the developer after the mixing is gradually mixed Although the toner density as a whole is reduced, when the developer after mixing is sent to the developing device and replenished, the developer is rotated at a higher speed than usual so that more developer is developed. The agent (toner etc.) will be replenished quickly. As a result, even if the developer whose toner density starts to decrease is supplied, the toner amount of the developer present in the developing device does not decrease significantly, and a problem caused by the decrease in toner density (for example, development image Occurrence of a decrease in density) can be avoided.

  In each of the developing devices, the replenishing means includes an intake port that takes in the collected developer and an opening / closing member that opens and closes the intake port.

  In the case where the intake port and the opening / closing member are provided, the intake port can be closed by the opening / closing member, so that the developer (replenishment developer and recovered developer) present in the replenishing means is taken in by the intake port. Can be prevented from flowing back to the developing device. In particular, when this configuration is employed in a rotary developing device that replenishes and collects developer by utilizing the motion unique to a rotating body as described in the above-mentioned Patent Document 2, the position by the rotation of the developing device. Even if there is a fluctuation, this is effective because the occurrence of the backflow phenomenon can be prevented.

  In each of the developing devices, the replenishing unit includes a supply port that supplies the replenishment developer to the developing device, and an opening / closing member that opens and closes the supply port.

  When the supply port and the opening / closing member are provided, the supply port can be closed by the opening / closing member, so that it is possible to prevent the developer existing in the developing device from flowing backward to the supply means side through the supply port. it can. Further, it is possible to prevent the developer existing in the replenishing means from being inadvertently supplied to the developing device side through the supply port.

  An image forming apparatus of the present invention is an image forming apparatus having a latent image carrier on which a latent image corresponding to image information is formed, and a developing device for developing the latent image of the latent image carrier with a developer. Any of the developing devices having the above-described configurations is provided as the developing device.

  According to this image forming apparatus, the collected developer collected from the developing device by the collecting means in the developing device is sent to the replenishing means, mixed with the replenishing developer, and replenished to the developing device. As a result, the life of the developing device can be extended. Further, it is not necessary to secure an installation space for installing a collection box for temporarily storing the collected developer, which is advantageous when the apparatus is downsized.

  According to such a developing device or image forming apparatus, the developer (mainly carrier) recovered from the developing device can be supplied again to the developing device and reused. In addition, there is a problem associated with temporarily storing the collected developer, that is, the installation space for the collection box or the like must be secured. Generation | occurrence | production of malfunctions, such as sacrificing accommodation space, can be eliminated.

  FIG. 1 shows an overall outline of a full-color printer to which the present invention is applied.

  The printer 1 is provided with an image forming engine 10 as described below inside the main body. The image forming engine 10 is provided with a photosensitive drum 11 as a latent image carrier that rotates at a predetermined speed in the direction of the arrow. Around the photosensitive drum 11, a charging roll 12 as a charger and an exposure unit as an exposure means. ROS (Raster Output Scanner) 13, rotary developing device 14 equipped with four color developing devices 30Y, 30M, 30C, 30K of yellow (Y), magenta (M), cyan (C), black (K), etc. Is arranged.

  Among these, the rotating type developing device 14 has four color developing devices 30Y, 30M, 30C, and 30K arranged in the circumferential direction of the rotating support 31. Further, the rotation support 31 is rotated by a predetermined amount in the direction of the arrow at a predetermined timing around the rotation shaft 31a, so that the developing devices 30Y, 30M, 30C, and 30K corresponding to the color to be developed are photosensitive. Each of them is moved to a developing position facing the drum 11.

  In this image forming engine 10, basically, after the surface of the photosensitive drum 11 is charged to a predetermined potential by the charging roll 12, a laser beam LB modulated in accordance with image information from the ROS 13 is applied to the charged surface. The electrostatic latent image is formed by scanning exposure, and then the electrostatic latent image is developed by the developer 2 supplied from a predetermined developing device 30 of the rotary developing device 14 to form a toner image of a predetermined color. It is formed.

  In particular, in the image forming engine 10, the above-described charging, exposure, and development processes are repeated a predetermined number of times according to the color of the image to be formed. For example, when a full-color image is formed, the charging, exposure, and development processes are repeated four times corresponding to each color of yellow, magenta, cyan, and black, whereby four colors are formed on the surface of the photosensitive drum 11. Corresponding toner images are sequentially formed.

  Further, the image forming engine 10 is provided with an intermediate transfer belt 21 as an intermediate transfer member at the transfer position of the photosensitive drum 11. The intermediate transfer belt 21 in this example is installed so as to rotate in synchronization with the photosensitive drum 11 while being wound around a plurality of rolls and wound around the outer peripheral surface serving as the transfer position of the photosensitive drum 11. . A primary transfer roll 15 as a primary transfer device is disposed on the inner peripheral surface portion of the intermediate transfer belt 21 that is in contact with the photosensitive drum 11. As a result, the toner image formed on the surface of the photosensitive drum 11 is primarily transferred onto the intermediate transfer belt 21 when passing through the primary transfer roll 15. When the four color toner images are formed on the photosensitive drum 11, the toner images are primarily transferred in a state where the toner images are sequentially superimposed on the intermediate transfer belt 21. The surface of the photosensitive drum 11 after the primary transfer is cleaned by the cleaning device 16.

  A secondary transfer roll 25 as a secondary transfer device is disposed on the intermediate transfer belt 21 at the transfer target position. The secondary transfer roll 25 is supported so as to be able to come into contact with and separate from the intermediate transfer belt 21 and contacts the intermediate transfer belt 21 only when the secondary transfer process is executed. Further, between the intermediate transfer belt 21 and the secondary transfer roll 25 (secondary transfer unit), the recording paper 3 is fed from the paper feed tray 31 of the paper feed unit 30 to a predetermined timing by the feeding device 32, the registration roll 33, or the like. Is fed. As a result, the toner image primarily transferred to the intermediate transfer belt 21 is secondarily transferred collectively to the recording paper 3 in the secondary transfer portion. The surface of the intermediate transfer belt 21 after the secondary transfer is cleaned by a cleaning device 26 supported so as to be able to come into contact with and separate from the belt 21.

  The recording paper 3 onto which the toner image has been secondarily transferred is conveyed from the secondary transfer portion to the fixing device 5. The fixing device 5 includes a heating roll 51 and a pressure roll 52 that rotate in pressure contact with each other. The recording paper 3 is heated and pressed when passing between the rolls in the fixing device 5, whereby the toner image is heat-fixed on the recording paper 3. The recording sheet 3 after fixing is normally discharged as it is onto a discharge tray 1A formed on the upper portion of the printer 1 main body by a discharge roll 55. A one-dot chain line in FIG. 1 indicates a basic conveyance path of the recording paper 3 from the paper supply unit 30 to the discharge tray 1A.

  As shown in FIGS. 2, 3 and the like, the rotary developing device 14 in the printer 1 has a rotating support 31 in addition to the developing units 30Y, 30M, 30C, and 30K, and in each developing unit 30. A developer (supplementing developer) 2A to be replenished is accommodated exclusively, and four developer cartridges 50 constituting a part of the developer replenishing device 5 are attached. In this example, each developer cartridge 50 is detachably attached to the rotary support 31 in a state of approaching the corresponding developing device 30. Further, a collecting device 7 is provided between each developing device 30 and each developer cartridge 50 to collect a part of the developer 2 in each developing device 30 and return it to the developer cartridge 50. ing.

  First, each of the developing devices 30Y, 30M, 30C, and 30K is configured in the same manner except for the difference in the type (color) of the developer to be used and the specific condition setting corresponding to the difference in the type. Yes. In each of the developing devices 30, a two-component developer including a nonmagnetic toner and a magnetic carrier is used as the developer 2.

  The common configuration will be described mainly. As shown in FIGS. 2 to 4 and the like, the developing device 30 has a hollow main body case that is partially opened in a slit shape along the axial direction of the photosensitive drum 11. 32, a developing roll 33 that rotates in a state where a part of the case 32 is exposed from the opening, and a rotating roll that is positioned obliquely below the developing roll 33 and is parallel to the developing roll 33. Spiral augers 34 and 35 as two developer agitating and conveying members are installed.

  The spiral augers 34 and 35 have a structure in which blade portions in a state of being spirally wound around the rotation axis along the axial direction are formed. A partition wall 36 is provided in the case 32 portion between the two spiral augers 34 and 35 (excluding both ends), and communicates at both ends in a parallel state with the partition wall 36 as a boundary. The developer containing passage in a state exists. Thereby, the developer 2 accommodated in the developer accommodating passage is circulated and conveyed in one direction so as to be supplied through the developing roll 33 while being agitated and frictionally charged by the rotation of the spiral augers 34 and 35. Is done. In this example, as shown in FIG. 3, the developer 2 is conveyed in the direction of arrow B by a spiral auger 35 disposed on the rear side when viewed from the developing roll 33, while the spiral auger disposed on the front side thereof. 34 is conveyed in the direction of arrow C (the direction opposite to the direction of arrow B).

  The developing roll 33 adsorbs the magnetic carrier contained in the developer 2 by a magnetic force by a magnet roll 33a installed in a fixed state inside the cylindrical roll body (sleeve), and the developer 2 is attached to the outer peripheral surface of the roll. The developer 2 is carried so as to form a magnetic brush. Then, the toner electrostatically attached to the carrier on the outer peripheral surface of the developing roll 33 is transported to a developing area facing the photosensitive drum 11 so that the electrostatic latent image on the photosensitive drum 11 is transferred to the developing area by the toner. It has come to be visualized.

  In each developing device 30, a replenishing port 37 for receiving the replenishing developer 2 </ b> A replenished from the developer cartridge 50 is formed in a portion of the upper portion of the case 32 that can face the spiral auger 35 on the rear side. Yes.

  A flap 68 whose one end swings about a shaft 68c is provided at the periphery of the supply port 37 so as to open and close the supply port (FIG. 5). As will be described later, the flap 38 swings in the internal space of the developing device according to the rotation position of the rotation support 32 (change in the direction of action of gravity) to open and close the supply port 37. In FIG. 5, a flap indicated by a solid line with reference numeral 68 </ b> A opens the supply port 37, and a flap indicated by a two-dot chain line with a reference symbol 68 </ b> B closes the supply port 37. By providing such a flap 68, the developer 2 in the developing device 30 can flow back to the developer cartridge 50 through the replenishing port 37 even when the rotary support 31 rotates during the developing process, as will be described later. Can be prevented.

  Further, a developer delivery mechanism 60 that constitutes a part of the developer supply device 5 is attached to each developing device 30. The delivery mechanism 60 is rotatably installed in a hollow interior of the delivery unit case 61 and a cylindrical developer delivery unit case 61 that is attached in a state where the delivery mechanism 60 communicates with the supply port 37 in the case 32 of the developing device on one end side. The spiral auger 62 is used. The developer delivery part case 61 is connected to the replenishment port 37 of the developing device case 32 through the connection opening 63. A receiving port 64 for receiving the replenishing developer 2 </ b> A supplied from the developer cartridge 50 is formed at an end of the developer sending unit case 61 opposite to the end facing the replenishing port 37. .

  The spiral auger 62 in the delivery mechanism 60 has substantially the same structure as the spiral auger 34 and the like in the developing device 30. The spiral auger 62 rotates at a predetermined timing for a predetermined time, thereby transporting the replenishment developer 2A supplied from the developer cartridge 50 through the receiving port 64 in the discharge portion case 61 in the direction of arrow B, Finally, the toner is conveyed to the connection opening 63 and supplied to the developing device 30. Further, as will be described later, the spiral auger 62 is rotated by the power of a dispensing motor (65).

  Further, each developing device 30 is attached to a portion of the upper portion of the case 32 facing the rear spiral auger 35 with a discharge pipe 70 constituting the collection device 7 penetrating and protruding. The discharge pipe 70 has a shape in which a tip end side existing in the case 32 of the developing device is bent in an L shape, and a recovery port 72 located in the case 32 has a developer from the supply port 37. It faces the downstream side in the circulation and conveyance direction (the part conveyed so as to be transferred from the rear spiral auger 35 to the front spiral auger 34) (see FIGS. 3 and 4). The opening area of the recovery port 72 is appropriately set according to the developer recovery rate.

  A discharge port 74 for discharging the collected developer (collected developer) 2B is formed at the end of the discharge pipe 70 opposite to the collection port 72. The discharge port 74 is also formed with a cartridge receiving portion having an arcuate cross-sectional arc shape that can be joined to the outer peripheral surface of the developer cartridge 50.

  A portion of the discharge pipe 70 which is slightly inside the discharge port 74 is provided with a flap 75 whose one end swings around the shaft 75c so as to open and close the inside of the discharge port (located on the lower side). (FIG. 6). As will be described later, the flap 75 swings in the space inside the discharge pipe 70 according to the rotational position of the rotary support 32 (change in the direction of action of gravity) to open and close the discharge port 74. In FIG. 6, a flap indicated by a two-dot chain line denoted by reference numeral 75 </ b> A is in a state in which the discharge port 74 is open, and a flap denoted by reference numeral 75 </ b> B and indicated by a solid line is a state in which the discharge port 74 is closed. By providing this flap 75, as will be described later, even when the rotary support 31 rotates during the developing process, the developer 2B discharged from the developing device 30 and once recovered is returned to the developing device 30 through the discharge pipe 70. Can be prevented.

  On the other hand, as shown in FIGS. 3, 4, and 7, the developer cartridge 50 is a cylindrical structure having a cylindrical storage space for storing the replenishment developer 2 </ b> A. On the outer peripheral surface of the cartridge 50, a supply port 51 is formed at a position corresponding to the receiving port 64 of the developing device 30, and an intake port 52 is formed at a position corresponding to the discharge port 74 of the discharge pipe 70. Has been. Incidentally, in this cartridge 50, since there is no restriction that the space for storing the collected developer has to be ensured as in the prior art, the initial filling amount of the replenishment developer 2A is set to an arbitrary amount without being restricted. can do.

  In addition, an agitator 53 is installed inside the cartridge 50 for rotating and feeding the supplied developer 2A toward the supply port 51 (in the direction of arrow C). The agitator 53 has a shape having a spiral portion 53b in which a wire is spirally wound around the linear rotation shaft portion 53a so as to substantially follow the inner wall surface in the cartridge accommodation space. The agitator 53 is rotated by using the rotational power of the dispense motor of the spiral auger 62 in the delivery mechanism 60, but may be configured to rotate by the power of an independent drive source.

  From the viewpoint of efficiently and evenly mixing the collected developer 2B fed into the cartridge 50 with the replenishing developer 2A (which may include the collected developer 2B) present in the cartridge 50, the agitator 53 is shown in FIG. , 7 and the like, a stirring plate 55 that extends in the rotational radius direction from the rotating shaft portion 53a of the agitator may be added.

  Further, the developer cartridge 50 is slid along the circumferential direction on the outer peripheral surface portion where the supply port 51 and the intake port 52 are formed to open and close the supply port 51 and the intake port 52, respectively. 56 and 57 are provided (FIGS. 4 and 7). The slide shutters 56 and 57 slide in the direction in which the supply port 51 and the intake port 52 are closed before the developer cartridge 50 is completely attached (or removed) to the rotation support 31 of the developing device 14. It is biased by a spring or the like (not shown) so as to be positioned.

  In the printer 1, for example, from the developer cartridge 50, the process control operation is executed at a predetermined timing so that the density of each color toner image formed by each developing device 30 of the developing device 14 is stabilized. A developer replenishing operation for replenishing the developer 2A for replenishment to each developing device 30 of the developing device 14 through the delivery mechanism 60 is executed. The predetermined timing is, for example, when the printer is turned on or when a predetermined number of image forming operations (printing) are performed.

  In the process control operation, a reference patch mark composed of the four color toner images is formed on the photosensitive drum 11 at a predetermined reference density such as 100% or 50%, and then transferred to the intermediate transfer belt 21 in an optical manner. The control operation for executing the developer replenishment operation to the required developing device 30 when it is determined that the measured value is lower than the predetermined density value and determined to be lower than the predetermined density value. I do.

  FIG. 8 shows a configuration of a control system mainly related to the developing device 14 in the printer 1.

  The main controller 100 controls the control units of each unit of the printer 1 as a whole. The main controller 100 is connected to an external host computer (not shown) via a network so that image data to be printed is input. The input image data is input to the image formation processing control unit 101 after being subjected to a predetermined process.

  The image forming process control unit 101 mainly controls the operation of each component device in the image forming engine unit 10 in order to perform an image forming operation (printing) by the image forming engine unit 10 based on input image data. The control unit performs synchronous control. As each control unit, there are a driving system control unit, a charging system control unit, an exposure system control unit, a fixing device control unit, etc. (not shown) in addition to the developing device control unit 103 described later.

  The main controller 100 is connected to a process control unit 102 that performs control related to the process operation. The process control unit 102 instructs the image forming processing control unit 101 to form a reference patch mark for density control on the surface of the intermediate transfer belt 21 in the image forming engine unit at a predetermined timing.

  The density sensor 28 described above is connected to the image forming process control unit 101. The density sensor 28 detects the image density of the reference patch mark formed on the surface of the intermediate transfer belt 21. Information detected by the density sensor 28 at this time is transmitted to the process control unit 102 via the image forming process control unit 101. The process control unit 102 stores reference density data. The comparison unit compares the reference density data with the density data detected by the density sensor 28, and develops based on the examination result of the comparison unit. A determination unit is provided for determining whether or not it is necessary to execute a replenishment operation. The comparison unit, the determination unit, the concentration sensor 28, and the like constitute “replenishment detection means” for detecting during a replenishment operation.

  The developing device control unit 103 performs control related to operations related to the developing device 14 (rotating support rotating operation, developing device driving, developing bias applying operation, developer replenishing operation, etc.) A replenishing / feeding mechanism control unit 105 for controlling the operation (drive of the dispensing motor) of the replenishing device 5 of the replenishing device 5 attached to each developing device 30 is connected.

  Then, in the process control unit 102, when it is determined that the developer replenishment operation is necessary in the replenishment detection means, the replenishment delivery mechanism control unit is provided via the developing device control unit 103 so as to perform the replenishment operation. Give instructions to 105. In the replenishing / sending mechanism control unit 105, the dispensing motor 65 in the sending mechanism 60 is rotated at a predetermined speed for a preset time t, and the spiral auger 62 in the sending mechanism 60 is rotationally driven.

  The process control unit 102 cumulatively counts pixel values of image information of a printing operation performed after one developer cartridge 50 is mounted in the image forming process control unit 101, and sets the count value in advance. A comparison unit for comparing with a reference value and a determination unit for determining whether or not the developer replenishment operation needs to be performed at a higher speed than normal based on the result of the comparison by the comparison unit are provided. A “toner density detecting means” for detecting that the toner density of the developer in the developer cartridge 50 is lowered is constituted by the comparison section, the determination section, the pixel accumulation counter, and the like.

  Then, when it is determined that the toner density detecting means needs a high-speed replenishment operation of the developer, the process control unit 102 replenishes and sends the replenishment operation via the developing device control unit 103 so as to perform the replenishment operation. An instruction is given to the mechanism control unit 105. At this time, the replenishing / sending mechanism control unit 105 performs control to switch the rotation speed of the dispensing motor 65 of the sending mechanism 60 from “normal speed” to “high speed” in a replenishing operation performed thereafter. (FIG. 10).

  Next, main operations of the developing device 14 and the printer 1 equipped with the developing device 14 will be described.

  As described above, the electrostatic latent image formed for each color on the photosensitive drum 11 in the image forming engine unit 10 of the printer 1 is developed by the developing device 14 containing the developer 2 corresponding to the color of the latent image. The developing device 30 is moved to a developing position facing the photosensitive drum 11 by the rotation of the rotary support 31 and is moved to be visualized.

  In FIG. 2, the developing device 30 (Y) at the position (developing position) indicated by E1 performs the developing operation. At this time, the replenishment developer 2A is replenished from the developer delivery section case 61 in the delivery mechanism 50 of the replenishing device 5 by the flap 68 being opened by its own weight (68A: FIG. 5). It is put in a state where it can be supplied through the mouth 37. At this time, the flap 75 of the discharge pipe 70 is closed by its own weight (75B: FIG. 6), and the replenishment developer 2A in the developer cartridge 50 is supplied to the developer 30. There is no backflow to the side.

  When the developing device 30 is in the E1 position, if a developer replenishing operation instruction to be described later is instructed, the replenishing operation is executed. On the other hand, when this replenishment operation is executed, at least a part of the developer 2 increased in the developing device 30 is circulated and conveyed by the spiral augers 34 and 35 and is collected into the collection port 72 of the discharge pipe 70. It is led as 2B.

  Next, in the developing device 3 (M) moved to the E2 position shown in FIG. 2 by the rotation of the rotary support 31, the flap 68 hangs down due to its own weight, so that the supply port 37 is opened halfway. At this time, when the recovery port 72 of the discharge pipe 70 is peeled upward, and there is the recovered developer 2B introduced from the recovery port 72, the developer flows back to the developing device 30 side. And reliably taken into the discharge pipe 70.

  Next, in the developing device 3 (C) moved to the E3 position shown in FIG. 2 by the rotation of the rotary support 31, the flap 68 closes the supply port 37 by its own weight (68B: FIG. 5). The developer 2 in 30 does not flow backward to the delivery mechanism 60 side. At this time, the flap 75 of the discharge pipe 70 hangs down due to its own weight, and the discharge port 74 of the developing device is opened (75a: FIG. 6). As a result, the collected developer 2B taken into the discharge pipe 70 is discharged. It is dropped so as to be returned into the developer cartridge 50 through the outlet 74.

  Finally, in the developing device 3 (K) moved to the E4 position shown in FIG. 2 by the rotation of the rotary support 31, the flap 68 keeps the supply port 37 closed by its own weight. At this time, the flap 75 of the discharge pipe 70 makes the discharge port 74 half open by its own weight.

  Thereafter, in the developing device 30 that is moved from the E4 position to the E1 position and is subjected to the developing operation, when the developing replenishment operation is executed, the agitator 53 in the developer cartridge 50 rotates, whereby the collected developer is recovered. 2b is mixed with the replenishment developer 2A and conveyed to the supply port 51 side. As a result, the collected developer 2b including the carrier is supplied to the developing device 30 in a state where it is mixed with the supply developer 2A and reused. When a developer cartridge 50 having an agitator 53 with an additional stirring plate 55 as shown in FIGS. 4 and 7 is used, the recovered developer 2b is supplied by the stirring plate 55 to the replenishment developer. Better and reliable mixing with 2A.

  Then, during the normal printing operation (between jobs), the process control control related to the replenishing operation of the developing device is executed.

  In this process control control, first, as shown in FIG. 9, the above-described reference patch mark for density control is formed on the intermediate transfer belt 21 (step 10: S10), and the density sensor 28 for the patch mark is formed. The density is detected by (S11). Subsequently, reference density data for density adjustment is read from the storage unit of the process control unit 102 (S12), the reference density is compared with the detected density (S13), and the detected density is less than the reference density value. It is determined whether or not there is (S14).

  If it is determined in step 14 that the detected density is not less than the reference density value, the replenishment operation is deemed unnecessary and the replenishment operation is not executed, but if it is determined that it is less than the reference density value. Are deemed to require replenishment. The above operation corresponds to the operation of the above-described supply detection means.

  Next, when it is determined in step 14 that the detected density is equal to or lower than the reference density value, the toner density detection data of the developer is read from the image shape processing control unit 101 (S15). The toner density detection data at this time is a cumulative count value of pixels that are cumulatively counted by the image shape processing control unit 101 described above. Subsequently, the accumulated count value as the read toner density detection data is compared with a predetermined threshold value (S16), and it is determined whether or not the accumulated count value exceeds the threshold value (S17).

  If it is determined in step 17 that the cumulative count value does not exceed the threshold value, the toner concentration of the replenishment developer 2A in the developer cartridge 50 is greatly reduced by mixing with the recovered developer 2B. Therefore, the replenishment operation in a state where the dispensing motor 65 is rotated at the normal speed is started (S18). As a result, the replenishment developer 2A fed from the developer cartridge 50 to the delivery mechanism 60 (including the developer 2B when the recovered developer 2B is reused) is conveyed by the spiral auger 62 that rotates at normal speed. Finally, the developer 30 is supplied through the connection opening 63.

  On the other hand, if it is determined in step 17 that the cumulative count value has exceeded the threshold value, it is considered that the toner concentration of the replenishment developer 2A in the developer cartridge 50 has dropped significantly due to mixing with the recovered developer 2B. Thereafter, the replenishment operation is started in a state where the dispensing motor 65 is rotated at a speed higher than the normal speed (S19). As a result, the replenishment developer 2A (including the collected developer 2B as described above) fed from the developer cartridge 50 to the delivery mechanism 60 is conveyed more than usual by the spiral auger 62 that rotates at high speed. Finally, the developer 30 is supplied through the connection opening 63. The above operation corresponds to the operation of the above-described deterioration detection means.

  When any one of the replenishing operations is started, a timer is started (S20), and it is determined whether or not the rotation operation time of the dispensing motor 65 has reached a predetermined time (t) (S21). At this stage, the rotation operation of the dispensing motor 65 stops and the replenishment operation ends (S22).

As described above, in the developing device 14, as shown in FIG. 10, when the replenishment detecting unit determines that replenishment is necessary, the replenishment device 5 replenishes the developer to the developing device 30. The In this case, the collected developer 2B is returned from the developing device 30 to the developer cartridge 50 by the collecting device 7 and reused as a replenishment developer. The drive time (one replenishment operation time) t (t ₁ , t ₂ ,... T _n ) of the dispensing motor 65 during this replenishment operation is the same constant time, but varies depending on necessity. May be set.

  If the toner concentration detecting means determines that the toner concentration of the developer in the developer cartridge 50 is in a lowered state, the subsequent replenishment operation of the developer is performed at a high speed from the normal speed to the dispensing motor. The operation is executed while being switched to an operation for rotational driving. As a result, when the driving time t of the dispensing motor 65 is constant, more developer than usual is sent from the delivery mechanism 60 to the developing device 30 and is replenished. As a result, a lot of good (less deteriorated) developer (toner, etc.) is replenished to the developing device even slightly. The speed of high-speed driving at this time is set to a speed that is 1.1 to 2.0 times the normal speed (normal speed).

  Moreover, in the printer 1 provided with the developing device 14, as described above, a sufficient initial filling amount of the replenishment developer in the developer cartridge 50 can be secured, and the collected developer is developed for replenishment. Since it can be reused after being mixed with the agent, the life of the developing device 14 can be extended, and it is possible to perform stable development over a long period of time, and consequently, a printing operation.

  In the embodiment described above, the developing device is exemplified as a rotating device. However, the present invention is a fixed developing device that is used by being installed at a fixed position with respect to a latent image carrier such as a photosensitive drum. Even an apparatus is applicable. In this case, a developer conveying member such as a spiral auger is provided for at least one of replenishing the developer from the replenishing device to the developing device and collecting the recovered developer recovered from the developing device to the replenishing device. It is necessary to use a developer transport device.

  Further, in the above-described embodiment, the case where the replenishment operation is controlled to be performed at a higher speed than the normal time according to the state of decrease in the toner density of the developer in the developer cartridge 50 is illustrated. You may comprise so that replenishment operation | movement may be performed. Incidentally, the developer cartridge 50 is used by replacing it with a new one at a predetermined timing. At the time of this replacement, the recovered developer 2B is removed from the developing device 14 and the printer 1 main body together with the developer cartridge to be removed as used.

It is explanatory drawing which shows the principal part of the printer of this invention. It is explanatory drawing which shows the principal part of the image development apparatus of this invention used for the printer of FIG. FIG. 3 is a schematic cross-sectional view showing one developing device (including a replenishing device) in the developing device of FIG. 2. FIG. 4 is a schematic sectional view showing the developing device (including a replenishing device) of FIG. 3. FIG. 6 is an explanatory cross-sectional view showing a structure of a connection portion between a replenishing device (feeding mechanism) and a developing device. It is sectional explanatory drawing which shows a collection | recovery apparatus. FIG. 6 is an explanatory cross-sectional view showing a developer cartridge in the replenishing device. FIG. 4 is a block diagram illustrating a configuration of a control system related to a developer replenishing operation. It is a flowchart which shows the process of the control operation | movement of the process control regarding replenishment operation | movement. It is a timing chart which shows the state of speed control of replenishment operation and replenishment operation. It is explanatory drawing which shows typically the principal part of the conventional rotary developing apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Printer (image forming apparatus), 2 ... Developer containing toner and carrier, 2A ... Replenishment developer, 2B ... Recovered developer, 5 ... Replenishment device (replenishment means), 7 ... Recovery device (recovery means), DESCRIPTION OF SYMBOLS 11 ... Photosensitive drum (latent image carrier), 14 ... Developing device, 30 ... Developer, 33 ... Developing roll (Developer carrier), 50 ... Developer cartridge (a part of supply means), 55 ... Stirring plate ( Agitation member), 60 ... delivery mechanism (part of developing means), 64 ... supply port, 68 ... flapper (opening / closing member), 70 ... discharge pipe (part of recovery means), 74 ... intake port, 75 ... flapper (Opening / closing member), 102... Process control unit (part of the supply control unit), 105... Supply supply mechanism control unit (part of the supply control unit).

Claims (6)

A developer that contains a developer including at least toner and a carrier and conveys the developer while circulating the developer to a developer carrier;
A replenishing means for containing a replenishing developer for replenishing the developing device and replenishing the replenishing developer to the developing device;
A part of the developer stored in the developing unit is discharged and collected, and the collected developer collected in the replenishing unit is mixed with the replenishing developer present in the replenishing unit and reused. A developing device having a collecting means for feeding.   The developing device according to claim 1, wherein the replenishing unit includes a stirring member that stirs the replenishing developer and the collected developer.   The replenishing means includes a delivery mechanism for rotating and delivering the developer for replenishment, and a replenishment control unit for increasing the rotational speed of the delivery mechanism from the normal time according to the toner concentration of the developer. Item 3. The developing device according to Item 1 or 2.   The developing device according to claim 1, wherein the replenishing unit includes an intake port that takes in the collected developer and an opening / closing member that opens and closes the intake port.   The developing device according to claim 1, wherein the replenishing unit includes a supply port that supplies the replenishment developer to the developing device, and an opening / closing member that opens and closes the supply port. An image forming apparatus having a latent image carrier on which a latent image corresponding to image information is formed, and a developing device for developing the latent image of the latent image carrier with a developer,
An image forming apparatus comprising the developing device according to claim 1 as the developing device.

Images