JP2014026129A - Developing device, image forming apparatus including the developing device, and detection method for detecting problem in two-component developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a problem due to degradation in the condition of a two-component developer reserved in a developing device.SOLUTION: The developing device includes: a developing tank 330 reserving a two-component developer containing a toner and a carrier; a developing roller 335 supplying the toner in the two-component developer to a photoreceptor; a first magnetic permeability sensor 338, which is arranged in a developer tank bottom, at a position close to the developing roller and which detects a magnetic permeability of the two-component developer; a second magnetic permeability sensor 339, which is arranged in the developer tank bottom, at a position farther from the developing roller than the first magnetic permeability sensor, and which detects a magnetic permeability of the two-component developer; and detecting means 91 detecting a problem of the two-component developer based on a difference in the magnetic permeability detected by the first and second magnetic permeability sensors.

Description

  The present invention stores a two-component developer containing toner and a carrier, supplies the toner of the two-component developer to a photoreceptor, an image forming apparatus provided with the developing device, and a stored two-component developer The present invention relates to a detection method for detecting a defect of an agent.

  In general, a developing device provided in an image forming apparatus stores developer in the apparatus and supplies the developer stored in a photosensitive member serving as a toner image carrier by a developing roller of the apparatus. Has been. In particular, in a developing device using a two-component developer in which toner and a carrier are mixed, the toner replenished from the toner replenishing unit is conveyed while being mixed with the carrier by a screw, a paddle or the like, and is supplied to the developing roller. . Then, the toner consumed by the image forming process is replenished from the toner replenishing unit, and mixing, stirring, and conveyance with the carrier are repeated again. Further, in such a conventional developing device, generally, the toner density stored using a magnetic permeability sensor or the like is detected, and when it is determined that the toner density is lower than a predetermined set value, toner replenishment is performed. The toner is replenished from the part.

  Such a two-component developer stored in a conventional developing device can be used for a long period of time so that the toner in the developer is deteriorated, the developer storage amount is reduced, or the toner and the carrier are mixed. A reduction in the specific balance may occur. That is, the state of the stored developer gradually deteriorates as compared with the optimum state immediately after the introduction of the apparatus or immediately after the maintenance. If the deterioration of the developer state exceeds an allowable range, the ability of the developer itself to supply toner to the photoreceptor is reduced.

  For example, when image forming processing with a low image area ratio is continuously performed due to toner deterioration of the developer, the toner consumption is low, so that much of the developer toner remains in the developing device without being consumed. End up. Then, since the toner staying in the developing device for a long time is repeatedly agitated, toner deterioration occurs in which the additive that promotes charging dispersed in the toner is buried or released in the toner. Due to such toner deterioration, the ability of the developer itself to supply toner to the photoreceptor is reduced, and the density of the formed image is reduced.

  In relation to such toner deterioration of the developer, Patent Document 1 describes a developing device 100 that determines the degree of toner deterioration based on a change in the volume of the developer, as shown in FIG. The developing device 100 includes a sensor 101 that detects a change in the volume of the developer stored in a case that stores a developer containing toner and a carrier. Here, the sensor 101 is provided with a filler 102 that detects the bulk of the developer.

  That is, when the developer toner contained in the case deteriorates, the fluidity of the developer deteriorates. Then, a portion where the developer stays appears in the case, and the bulk of the developer in the staying portion increases. The sensor 101 detects that the volume of the developer has exceeded a certain level due to the movement of the filler 102, and determines the degree of toner deterioration.

  Here, the developing device 100 has density detection means (not shown) for detecting the toner density of the developer, and the toner supplied from the toner replenishing device 103 according to the toner density detected by the density detection means. It is configured to be able to incorporate.

JP 2008-76428 A

  However, in the developing device 100 of Patent Document 1, when the developer state deteriorates in addition to the toner deterioration, there is a possibility that the degree of toner deterioration cannot be correctly determined.

  For example, if the developer carrier is discharged out of the apparatus after the introduction of the apparatus or after the maintenance, the carrier content of the developer decreases. Further, the developing device 100 replenishes toner according to the toner density detected by the density detecting means. That is, when the carrier content of the developer decreases, the toner content of the developer also decreases.

  For this reason, in the developing device 100 of Patent Document 1, when the developer carrier is discharged outside the device, the bulk of the stored developer is reduced as a whole. In other words, even when toner deterioration has occurred, there is a possibility that the degree of toner deterioration cannot be correctly determined because the volume of the developer does not exceed a certain level.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device that detects a problem caused by deterioration of the state of a two-component developer stored in the developing device, and an image forming apparatus having the developing device. An object of the present invention is to provide a detection method for detecting a malfunction of an apparatus and a two-component developer.

  The developing device of the present invention is provided at a developing tank for storing a two-component developer containing toner and a carrier, a developing roller for supplying the toner of the two-component developer to a photosensitive member, and a developing tank bottom near the developing roller. A first magnetic permeability sensor for detecting the magnetic permeability of the two-component developer, and a magnetic permeability of the two-component developer disposed at the bottom of the developing tank farther from the developing roller than the first magnetic permeability sensor. And a detecting means for detecting a defect of the two-component developer based on a difference between the magnetic permeability detected by the first and second magnetic permeability sensors.

  Preferably, the developing device of the present invention is characterized in that an agitating and conveying member that conveys the two-component developer while stirring is disposed in the vicinity of the second magnetic permeability sensor.

  The image forming apparatus of the present invention includes any one of the developing devices described above.

  Further, the detection method for detecting a problem of the two-component developer according to the present invention stores a two-component developer containing toner and a carrier and has a developing roller having a developing roller for supplying the toner of the two-component developer to a photoconductor. And detecting a magnetic permeability of the two-component developer in the vicinity of the first point in the vicinity of the developing roller, and with respect to the developing roller from the first point. The difference between the second step of detecting the magnetic permeability of the two-component developer around the second point which is far away, the magnetic permeability detected in the first step, and the magnetic permeability detected in the second step is set in advance. And detecting a defect of the two-component developer based on the determination as to whether or not the reference value is exceeded.

  According to the present invention, it is possible to detect a problem due to deterioration of the state of the stored developer.

1 is a diagram illustrating an overall configuration of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 3 is a schematic perspective view of a developing unit 33. FIG. 3 is a cross-sectional view showing a configuration inside a developing unit 33 when viewed from the direction A shown in FIG. It is sectional drawing of the developing unit 33 which makes the line BB shown in FIG. 3 a cut surface line. It is a flowchart which shows the process sequence of the detection part 91. FIG. FIG. 6 is a diagram illustrating a relationship between a storage amount of a two-component developer and a magnetic permeability detected by magnetic permeability sensors 338 and 339. 7 is a flowchart illustrating a processing procedure of a toner supply control unit 92. It is a figure which shows the whole structure of the conventional image development apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the processing contents, each step will be described with “step” as “S”.

  FIG. 1 shows a schematic configuration of an image forming apparatus 1 according to an embodiment of the present invention. The configuration of the image forming apparatus 1 will be described below with reference to FIG.

  The image forming apparatus 1 includes a transport mechanism 10, an exposure unit 20, visible image forming units 30, 40, 50, 60, secondary for copying an original image read from a document onto a sheet-like recording medium such as copy paper. The image forming apparatus includes a transfer unit 70, a fixing unit 80, and a control unit 90.

  The transport mechanism 10 picks up the paper P held on the paper feed tray 10 a one by one, and various types for transporting the paper P to the visible image forming units 30, 40, 50, 60 and the secondary transfer unit 70. It is comprised from the mechanism member. Further, the transport mechanism 10 transports the paper P to the fixing unit 80 disposed downstream of the visible image forming units 30, 40, 50, 60 and the secondary transfer unit 70 in the paper transport direction, and the fixing It is composed of various mechanism members for holding the paper P carried out from the unit 80 by the paper discharge tray 10b.

  The exposure unit 20 emits laser light R corresponding to the original image toward the visible image forming units 30, 40, 50 and 60 in order to form an electrostatic latent image corresponding to the original image read from the document. To do. Specifically, the exposure unit 20 includes an optical system member such as a laser light source for emitting a laser beam, a polygon mirror that deflects the laser beam at a constant angular velocity, and a lens that corrects the laser beam deflected at a uniform angular velocity. (Illustrated).

  The four sets of visible image forming units 30, 40, 50 and 60 primarily transfer the toner images onto the intermediate transfer belt 75 based on the laser light R emitted from the exposure unit 20.

  Specifically, the visible image forming unit 30 includes a photoreceptor 31 that serves as a toner image carrier, a charger 32 that charges the photoreceptor 31 to a predetermined potential, and an electrostatic latent image on the surface of the photoreceptor 31. The image forming apparatus includes a developing unit 33 that supplies toner to the toner image and develops a toner image, a toner supplying unit 34 that supplies toner to the developing unit 33, and a primary transfer unit 35 that transfers the toner image to the intermediate transfer belt 75.

  The developing unit 33 has two sets of magnetic permeability sensors 338 and 339 for storing a two-component developer composed of black toner and a carrier and detecting the magnetic permeability around the sensor. The magnetic permeability sensors 338 and 339 output a detection signal corresponding to the detected magnetic permeability to the control unit 90. Here, the magnetic permeability detected by the magnetic permeability sensors 338 and 339 indicates the volume ratio of the carrier, which is a magnetic substance, in the stored two-component developer. That is, the magnetic permeability sensors 338 and 339 are sensors that output higher values as the ratio of the toner amount contained in the two-component developer is smaller or as the ratio of the carrier amount contained in the two-component developer is larger. is there. As the magnetic permeability sensors 338 and 339, for example, TS-K (trade name, manufactured by TDK Corporation) or the like can be used.

  The toner replenishing unit 34 has a replenishment controller 340 for controlling various replenishing members (not shown) for storing black toner of the same color as the toner in the developing unit 33 and replenishing the toner to the developing unit 33. doing. Here, the replenishment controller 340 controls various replenishment members based on a control signal output from the control unit 90. That is, the toner stored in the developing unit 33 is replenished or stopped based on the control signal output from the control unit 90.

  The other three sets of visible image forming units 40, 50 and 60 have the same configuration as that of the visible image forming unit 30, and each developing unit of the visible image forming units 40, 50 and 60 includes yellow. , Magenta and cyan toners and carriers are stored. Further, each toner supply unit of the visible image forming units 40, 50 and 60 contains toner of the same color as the toner in the developing unit.

  The fixing unit 80 fixes the toner image transferred onto the paper P. Specifically, the fixing unit 80 melts and fixes the toner image by heat and pressure when the paper P is sandwiched and moved between the fixing roller 81 in which the heating element 83 is incorporated and the pressure roller 82. Let

  The control unit 90 includes a detection unit 91 for detecting a defect of the two-component developer in the developing units of the visible image forming units 30, 40, 50 and 60, and the visible image forming units 30, 40, 50 and 60. A toner replenishment control unit 92 for replenishing toner from the toner replenishing unit to the developing unit. Here, each process by the detection unit 91 and the toner supply control unit 92 is started when a main power supply (not shown) of the image forming apparatus 1 is turned on by the user. The control unit 90 also has notification means (not shown) for notifying the user of a malfunction detected by voice or display output.

  FIG. 2 is a schematic perspective view of the developing unit 33. FIG. 3 is a cross-sectional view showing the configuration inside the developing unit 33 when viewed from the direction A shown in FIG. Further, FIG. 4 is a cross-sectional view of the developing unit 33 with the line BB shown in FIG. The configuration of the developing unit 33 will be described below with reference to these drawings.

  As shown in FIG. 2, the developing unit 33 includes a developing tank 330 and a developing tank cover 331 that is detachably provided above the developing tank 330 in the vertical direction, and has a cylindrical development at one end in the width direction. A roller 335 is disposed so as to expose a part of the roller surface. Here, the developing tank cover 331 has a supply port 33 </ b> A for supplying toner from the toner supply unit 34.

  As shown in FIG. 3, in the developing tank 330 constituting the internal space of the developing unit 33, a developing roller 335, two sets of stirring and conveying members 336 and 337 for stirring and conveying the developer in the developing tank 330, and Two sets of magnetic permeability sensors 338 and 339 for detecting the magnetic permeability of the developer in the developing tank 330 are provided.

  The developing tank 330 is a member for constituting an internal space for storing a two-component developer composed of toner and a carrier, and includes a doctor blade 3301 and a partition wall 3302.

  The developing roller 335 is a magnet roller disposed opposite to the photosensitive member 31 and is rotated by driving means (not shown) such as a motor so that the developer in the developing tank 330 is carried on the surface and carried. The toner contained in the developer is supplied to the photoreceptor 31. Here, a power supply (not shown) is connected to the developing roller 335, and a developing bias voltage is applied thereto. Then, the developer toner carried on the developing roller 335 is supplied to the photosensitive member 31 by electrostatic force generated by the developing bias voltage in the vicinity of the photosensitive member 31.

  The doctor blade 3301 is a plate-like member that regulates the amount of developer carried on the developing roller 335 to a predetermined amount, and is disposed at one end of the developing tank 330 close to the surface of the developing roller 335 along the longitudinal direction. ing. Here, as a material of the doctor blade 3301, stainless steel, aluminum, synthetic resin, or the like can be used.

  The partition wall 3302 is a member extending along the longitudinal direction of the developing tank 330 at a substantially central portion in the width direction of the developing tank 330, and is disposed between the bottom of the developing tank 330 and the developing tank cover 331. That is, the partition wall 3302 is a member provided to separate the developer conveyance path P by the agitation conveyance member 336 and the developer conveyance path Q by the agitation conveyance member 337.

  The magnetic permeability sensor 338 is disposed at the bottom in the vertical direction, which is the first point X of the developing tank 330 near the developing roller 335. Further, the magnetic permeability sensor 339 is disposed at the bottom in the vertical direction, which is the second point Y of the developing tank 330 in the vicinity of the stirring and conveying member 337.

  That is, the magnetic permeability sensor 338 detects the magnetic permeability of the developer immediately before being pumped up by the developing roller 335. Further, the magnetic permeability sensor 339 detects the magnetic permeability of the developer transported along the transport path Q.

  As shown in FIG. 4, the partition wall 3302 divides the internal space of the developing tank 330 into a conveyance path P, a conveyance path Q, a communication path R, and a communication path S. In addition, a supply port 33A is disposed above the conveyance path P in the vertical direction.

  The agitating and conveying member 336 and the agitating and conveying member 337 are auger clew-like members having spiral conveying blades, and the agitating and conveying member 336 is rotated by driving means (not shown) such as a motor, thereby conveying the path P. The developer is conveyed to the communication path R while being stirred. The agitating / conveying member 337 is also rotated by a driving unit (not shown) to convey the developer in the conveying path Q while stirring the developer up to the communication path S. Here, the developing roller 335 and the stirring and conveying members 336 and 337 are configured to rotate in conjunction with each other.

  Accordingly, the developing unit 33 rotates and drives the developing roller 335 and the agitating / conveying members 336 and 337 in association with each other in the order of the conveying path P, the communicating path R, the conveying path Q, and the communicating path S. The developer is circulated and moved. Further, the developing unit 33 draws up the developer in the developing tank 330 by the developing roller 335 while it is being conveyed on the conveying path Q, and carries it on the surface of the developing roller 335.

  FIG. 5 is a flowchart showing the processing procedure of the detection unit 91. The processing procedure of the detection unit 91 will be described with reference to FIG. Here, the detection unit 91 performs a process for detecting a defect of the developer in the developing unit for each of the visible image forming units 30, 40, 50 and 60. However, each processing is different only in that a detection signal is inputted to a magnetic permeability sensor of a developing unit that is individually configured by each visible image forming unit. Therefore, hereinafter, only a processing procedure for detecting a defect of the developer in the developing unit 33 will be described.

  First, the detection unit 91 receives detection signals V1 and V2 corresponding to the magnetic permeability detected by the magnetic permeability sensors 338 and 339 (S100), and calculates a difference value W between the detection signal V1 and the detection signal V2 ( S110).

  Subsequent to S110, it is determined whether or not the calculated difference value W is greater than or equal to a preset reference value P (S120). If it is less than the reference value P, the process proceeds to S100 described above. That is, the above-described confirmation processing from S100 to S120 is repeated until the difference value of the magnetic permeability detected by the magnetic permeability sensors 338 and 339 exceeds the reference value P.

  On the other hand, if it is determined in S120 that the calculated difference value W is greater than or equal to the preset reference value P, there is a possibility that the developer in the developing tank 330 is defective. The warning sound output and warning information are displayed (S130), and the process is terminated.

  As described above, in the image forming apparatus 1 according to the embodiment of the present invention, when it is determined that the magnetic permeability difference detected by the magnetic permeability sensors 338 and 339 is equal to or larger than the reference value P, the developing tank 330 is used. It is determined that there is a possibility that a problem has occurred in the developer. This process will be described below.

  FIG. 6 is a diagram showing the relationship between the storage amount of the two-component developer in the developing tank 330 and the output values detected by the magnetic permeability sensors 338 and 339. Here, in each storage amount, the mixing ratio of the toner and carrier of the two-component developer is the same. The output values of the magnetic permeability sensors 338 and 339 are detected when the developing roller 335 and the agitation transport members 336 and 337 are rotationally driven in conjunction with each other.

  As shown in FIG. 6, the output values of the magnetic permeability sensors 338 and 339 detected when the storage amount of the two-component developer decreases even though the mixing ratio of the toner of the two-component developer and the carrier is the same. It can be seen that the number is also decreasing. Furthermore, it can be seen that the output value detected by the magnetic permeability sensor 338 is more significantly reduced than the output value detected by the magnetic permeability sensor 339. That is, when the storage amount of the two-component developer in the developing tank 330 is reduced, the difference between the magnetic permeability detected by the magnetic permeability sensors 338 and 339 increases.

  Such a phenomenon is presumed to be caused by a certain amount of carrier being pumped up by the developing roller 335.

  That is, in the vicinity of the magnetic permeability sensor 339 disposed at the second point Y relatively far from the developing roller 335, the carrier content of the magnetic permeability sensor 339 is substantially the same in a wide range. That is, even if the two-component developer moves in the direction of the developing roller 335, the carrier of the same amount as the amount of carrier moving from the sensor detectable range moves to the sensor detectable range. For this reason, the magnetic permeability sensor 339 detects a substantially stable magnetic permeability regardless of the amount of carrier of the two-component developer.

  However, when the carrier amount of the two-component developer is small, a larger amount of carrier than the amount of carrier that moves to a range that can be detected by the transparency sensor 338 is pumped up by the developing roller 335. For this reason, the transparency sensor 338 detects a lower magnetic permeability when the carrier amount of the two-component developer is small.

  The detecting unit 91 uses such a phenomenon to detect a defect in the developer in the developing tank 330. That is, the detection unit 91 determines whether or not the carrier exceeding the allowable amount is pumped up by the developing roller 335 based on the difference in magnetic permeability detected by the magnetic permeability sensors 338 and 339. Then, when it is determined that such a state is present, the inside of the developing tank 330 is caused by factors such as deterioration of the toner of the developer, a decrease in the developer storage amount, or a decrease in the mixing ratio balance between the toner and the carrier. It is determined that there is a possibility that some trouble has occurred in the two-component developer.

  FIG. 7 is a flowchart showing the processing procedure of the toner replenishment control unit 92. The processing procedure of the toner replenishment control unit 92 will be described with reference to FIG. Here, the toner replenishment control unit 92 performs processing for replenishing toner from the toner replenishment unit to the developing unit for each of the visible image forming units 30, 40, 50 and 60. However, each processing is different only in that a control signal or a detection signal is inputted / outputted with respect to a replenishment controller of a replenishment unit or a magnetic permeability sensor of the developing unit individually configured by the visible image forming unit. Therefore, hereinafter, only a processing procedure for supplying toner from the toner supply unit 34 to the developing unit 33 will be described.

  The toner replenishment control unit 92 first receives a detection signal V2 corresponding to the magnetic permeability detected by the magnetic permeability sensor 339 (S200).

  Subsequent to S200, it is determined whether or not the detection signal V2 is less than a preset reference value Q (S210). If it is determined that the detection signal V2 is less than the reference value Q, a control signal for stopping toner supply is sent. Output to the replenishment controller 340 (S220). That is, when the toner of the toner supply unit 34 is supplied to the developing unit 33, the toner supply is stopped.

  On the other hand, if it is determined in S210 that the value is not less than the reference value Q, a control signal for supplying toner is output to the supply controller 340 (S230). That is, when toner supply is stopped, control is performed so that toner is supplied from the toner supply unit 34.

  Then, after the process of S220 or S230, the process proceeds to the process of S200 described above. That is, the processes from S200 to S230 described above are repeatedly executed.

  Here, whether or not the toner is replenished is determined by whether or not the output value detected by the magnetic permeability sensor 339 is equal to or greater than the reference value Q. This is because, as described with reference to FIG. 6, the magnetic permeability sensor 339 disposed at the second point Y relatively far from the developing roller 335 is relatively independent of the storage amount of the two-component developer. It is. That is, the reference value Q is set as a threshold for determining whether the amount of toner contained in the two-component developer is excessive or insufficient.

  As described above, the image forming apparatus 1 according to the embodiment of the present invention determines whether the amount of toner contained in the two-component developer is excessive or insufficient in combination with the processing of the detection unit 91 described above, and based on the determination. Thus, the toner supply unit 34 replenishes toner or stops replenishment. In other words, as long as the toner stored in the toner replenishing unit 34 does not run out, the two-component developer sufficiently containing toner is stored in the developing tank 330.

  Therefore, in the processing of the detection unit 91 described above, it is possible to detect a problem related to a decrease in the developer storage amount, such as the carrier of the two-component developer in the developing tank 330 being discharged out of the developing unit 33. it can.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 10 Conveyance mechanism 10a Paper feed tray 10b Paper discharge tray 20 Exposure unit 30,40,50,60 Visible image formation unit 31 Photoconductor 32 Charger 33 Development unit 33A Supply port 330 Development tank 331 Development tank cover 3301 Doctor blade 3302 Partition wall 335 Developing rollers 336, 337 Stirring conveying members 338, 339 Magnetic permeability sensor 34 Toner replenishment unit 340 Replenishment controller 35 Primary transfer unit 70 Secondary transfer unit 75 Intermediate transfer belt 80 Fixing unit 81 Fixing roller 82 Pressure roller 83 Heating element 90 Control Unit 91 Detection unit 92 Toner supply control unit

Claims (4)

A developing tank for storing a two-component developer containing toner and carrier;
A developing roller for supplying toner of the two-component developer to the photoreceptor;
A first magnetic permeability sensor disposed at the bottom of the developing tank in the vicinity of the developing roller and detecting the magnetic permeability of the two-component developer;
A second magnetic permeability sensor which is disposed at the bottom of the developing tank farther from the developing roller than the first magnetic permeability sensor and detects the magnetic permeability of the two-component developer;
A developing device comprising: a detecting unit that detects a defect of the two-component developer based on a difference in magnetic permeability detected by the first and second magnetic permeability sensors.   The developing device according to claim 1, wherein a stirring and conveying member that conveys the two-component developer while stirring is disposed in the vicinity of the second magnetic permeability sensor.   An image forming apparatus comprising the developing device according to claim 1. A detection method for detecting a failure of a two-component developer in a developing device having a developing roller that stores a two-component developer including toner and a carrier and supplies toner of the two-component developer to a photoreceptor,
A first step of detecting a magnetic permeability of the two-component developer around a first point in the vicinity of the developing roller;
A second step of detecting the magnetic permeability of the two-component developer around a second point that is farther from the developing roller than the first point;
Based on the determination of whether or not the difference between the magnetic permeability detected in the first step and the magnetic permeability detected in the second step exceeds a preset reference value, the two-component developer has a defect. And detecting the step.