JP6245034B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device that adjusts at least one of a developer supply amount and a discharge amount, and an image forming apparatus using the same.

  Conventionally, as a two-component developing type developing device using a developer containing toner and carrier, a trickle developing method (AR) that suppresses the deterioration of the developer by supplying a new developer while discharging a part of the developer. [Auto-Refining Developing System] is also used.

  In the trickle development method, the amount of developer in the developing device varies depending on the amount of developer replenished and discharged. Further, as the apparatus is downsized and the processing speed is increased, the variation in the developer amount in the main scanning direction tends to increase. As a result, there are concerns about uneven density due to poor supply of the developer and overflow of the developer due to excessive supply of the developer. Further, as the developer amount is biased, the stress applied to the toner is increased, so that the toner is likely to be aggregated. This causes problems such as white spots and clogging of the regulating portion.

  For this reason, a detection means for detecting the amount of developer (agent surface) inside is provided, and when the developer amount is too large, the developer is discharged, and conversely, when the amount is too small, the developer is supplied. An apparatus has been proposed (see, for example, Patent Document 1).

JP 2005-292511 A JP 2013-37257 A

  Deviation in the amount of developer in the developing device may occur not only in the supply tank that supplies the developer to the developing roller but also in the stirring tank in which the developer is stirred. The deviation in the developer amount in the agitation tank also affects the deviation in the developer amount in the supply tank. Therefore, in order to appropriately adjust the supply amount and discharge amount of the developer, it is preferable to consider not only the amount of developer in the supply tank but also the amount of developer in the stirring tank.

  SUMMARY OF THE INVENTION In view of the above-described problems, it is an object of the present invention to provide a developing device that can more appropriately adjust at least one of a developer replenishment amount and a discharge amount, and an image forming apparatus including the developing device. To do.

The developing device according to the present invention includes a stirring tank for stirring the developer and a supply tank for supplying the developer to the developing roller, and circulates and conveys the developer in a circulation path including the stirring tank and the supply tank. A developing device that replenishes developer upstream of the agitation tank and joins the circulation path; and discharge means that discharges the developer branched from the circulation path downstream of the supply tank; First detection means for detecting the developer amount at a first position near the downstream of the agitation tank, and second detection means for detecting the developer amount at a second position near the downstream of the supply tank. The control unit includes an adjustment unit that adjusts both the replenishment amount and the discharge amount of the developer based on the detection results of the first detection unit and the second detection unit.

According to this configuration, both the supply amount and the discharge amount of the developer can be adjusted more appropriately. In addition, the downstream side of a stirring tank or a supply tank is a downstream side rather than the center, and the case where it is the most downstream is also included. In addition, the form of detection of the developer amount by the first detection means and the second detection means is not limited to the form of directly detecting the developer amount, but the form of indirectly detecting the developer amount (for example, developer Or the like in which the position of the liquid level is detected.

  More specifically, in the configuration described above, the adjustment unit compares each detection result of the first detection unit and the second detection unit with a predetermined reference value, and performs the adjustment based on the comparison result. It is good.

  More specifically, in the configuration described above, the adjustment unit adjusts the adjustment when the detection result of the first detection unit is larger than the reference value and the detection result of the second detection unit is smaller than the reference value. As the process, a first adjustment process for reducing the discharge amount and a second adjustment process for increasing the discharge amount after a predetermined first time has elapsed from the start of the first adjustment process may be performed.

  More specifically, in the configuration described above, the adjustment unit adjusts the adjustment when the detection result of the first detection unit is larger than the reference value and the detection result of the second detection unit is smaller than the reference value. As the process, a third adjustment process for decreasing the replenishment amount and a fourth adjustment process for increasing the replenishment amount after a lapse of a predetermined second time from the start of the third adjustment process may be performed.

  More specifically, in the configuration described above, the adjustment unit adjusts the adjustment when the detection result of the first detection unit is smaller than the reference value and the detection result of the second detection unit is larger than the reference value. As the process, a fifth adjustment process for increasing the discharge amount and a sixth adjustment process for decreasing the discharge amount after a predetermined first time from the start of the fifth adjustment process may be performed.

  More specifically, in the configuration described above, the adjustment unit adjusts the adjustment when the detection result of the first detection unit is smaller than the reference value and the detection result of the second detection unit is larger than the reference value. As the process, a seventh adjustment process for increasing the replenishment amount and an eighth adjustment process for decreasing the replenishment amount after a lapse of a predetermined second time from the start of the seventh adjustment process may be performed.

  More specifically, in the above configuration, the first time may be set to a time when the developer is transported from the first position to the second position. Further, the second time may be set to a time when the developer is transported from the second position to the joining position.

  More specifically, in the configuration described above, the adjustment unit may be configured as the first detection unit or the second detection unit as the adjustment process when the detection results of the first detection unit and the second detection unit are both greater than the reference value. It is good also as a structure which performs the process which increases the said discharge | emission amount and decreases the said replenishment amount until the detection result of 2 detection means falls below the said reference value.

  More specifically, in the configuration described above, the adjustment unit may be configured as the first detection unit or the second detection unit as the adjustment process when the detection results of the first detection unit and the second detection unit are both smaller than the reference value. It is good also as a structure which performs the process which decreases the said discharge | emission amount and increases the said replenishment amount until the detection result of 2 detection means exceeds the said reference value.

  More specifically, the adjustment unit may adjust the discharge amount by adjusting the opening width of the discharge port through which the developer is discharged. More specifically, in the configuration described above, the adjustment unit monitors factors affecting the developer conveyance speed or fluidity in the circulation path, and the content of the adjustment process according to the monitoring result. It is good also as a structure which changes.

  The image forming apparatus according to the present invention includes the developing device having the above-described configuration. According to this configuration, it is possible to enjoy the advantages of the developing device configured as described above.

According to the developing device of the present invention, both the supply amount and the discharge amount of the developer can be adjusted more appropriately. Further, according to the image forming apparatus of the present invention, it is possible to enjoy the advantages of the developing device of the present invention.

1 is an overall configuration diagram of a printer according to an embodiment. FIG. 2 is a schematic cross-sectional view of the developing device according to the present embodiment (including description of adjusting means). It is explanatory drawing regarding the structural example of the shutter which concerns on this embodiment. It is explanatory drawing regarding the mechanism which adjusts the opening width of a discharge port. It is explanatory drawing regarding the mechanism which adjusts the opening width of a discharge port. It is a graph showing the relationship between the drive time of a magnetic sensor and a count value. 6 is a graph showing a relationship between a position on a circulation path and a developer amount in a situation A. 6 is a graph showing a relationship between a position on a circulation path and a developer amount in a situation B. 6 is a graph showing a relationship between a position on a circulation path and a developer amount in a situation C. 10 is a graph showing a relationship between a position on a circulation path and a developer amount in a situation D. 5 is a flowchart regarding adjustment of developer replenishment amount and discharge amount.

  Embodiments of the present invention will be described with reference to the drawings, taking a tandem type digital color printer (which is one form of an image forming apparatus using a developing device, hereinafter simply referred to as “printer”) as an example. However, the content of the present invention is not limited to the embodiment.

[Entire printer configuration]
FIG. 1 is an overall configuration diagram of a printer 10 according to the present embodiment. The printer 10 includes an intermediate transfer belt 12 at substantially the center of the inside thereof. The intermediate transfer belt 12 is made of a semiconductive material, is supported on the outer periphery of three rollers (14, 16, 18), and is driven to rotate in the direction of arrow A.

  Below the lower horizontal portion of the intermediate transfer belt 12, four image forming units (image forming means) (image forming means) respectively corresponding to yellow (Y), magenta (M), cyan (C), and black (K) toners. 20Y, 20M, 20C, 20K) are arranged side by side along the intermediate transfer belt 12.

  Each image forming unit (20Y, 20M, 20C, 20K) has a photosensitive drum (22Y, 22M, 22C, 22K). Around each photosensitive drum (22Y, 22M, 22C, 22K), a charger (24Y, 24M, 24C, 24K) and a print head unit (26Y, 26M, 26C, 26K) are sequentially arranged along the rotation direction. ), A developing device (28Y, 28M, 28C, 28K), a primary transfer roller (primary transfer member) (30Y, 30M, 30C, 30K), and a cleaner (32Y, 32M, 32C, 32K). ing.

  The chargers (24Y, 24M, 24C, 24K) are for uniformly charging the surface of the photosensitive drum (22Y, 22M, 22C, 22K). The print head portions (26Y, 26M, 26C, 26K) form an electrostatic latent image by exposing the uniformly charged surface of the photosensitive drum according to each color image data. The developing devices (28Y, 28M, 28C, 28K) develop the electrostatic latent image formed on the surface of the photosensitive drum with each color toner to form a toner image.

  The primary transfer rollers (30Y, 30M, 30C, 30K) are in contact with the inside of the intermediate transfer belt 12 at positions facing the respective photosensitive drums (22Y, 22M, 22C, 22K) with the intermediate transfer belt 12 interposed therebetween. Each is provided for primary transfer of a toner image formed on the surface of the photosensitive drum onto the intermediate transfer belt 12. The cleaners (32Y, 32M, 32C, and 32K) collect and clean the toner remaining on the surface of the photosensitive drum after the primary transfer.

  Here, the developing device (28Y, 28M, 28C, 28K) is replenished with developer composed of toner and carrier contained in a toner bottle (not shown). Further, the developing devices (28Y, 28M, 28C, 28K) are provided with a developer discharge port, and a trickle developing system (exhaust developer in the developing device is discharged into the waste toner box 40). (AR system) mechanism is provided. The configuration and operation of the developing devices (28Y, 28M, 28C, 28K) will be described in detail again.

  The print head unit (26Y, 26M, 26C, 26K) is composed of a large number of LEDs arranged in the main scanning direction parallel to the axial direction of the photosensitive drum. A secondary transfer roller (secondary transfer member) 34 is pressed against the outside of the portion of the intermediate transfer belt 12 supported by the roller 18.

  A contact area between the secondary transfer roller 34 and the intermediate transfer belt 12 is a transfer area 36. The secondary transfer roller 34 can be retracted to a position where it is not in contact with the intermediate transfer belt 12 by a retracting mechanism (not shown).

  A primary transfer voltage V1 is applied to the primary transfer rollers (30Y, 30M, 30C, 30K) from a power source (not shown). By the action of the primary transfer voltage V1, each color toner image formed on the surface of the photosensitive drum (22Y, 22M, 22C, 22K) of each image forming unit (20Y, 20M, 20C, 20K) is electrostatically attracted. Then, primary transfer is performed on the intermediate transfer belt 12.

  The secondary transfer roller 34 is applied with a secondary transfer voltage V2 by a power source (not shown), and the roller 18 supporting the intermediate transfer belt 12 is grounded. By the action of the secondary transfer voltage V2, the toner image formed on the intermediate transfer belt 12 is electrostatically attracted to the paper conveyed to the transfer area 36 as will be described later, and is secondarily transferred. .

  A cleaner 38 (cleaning brush roller) is pressed against the portion of the intermediate transfer belt 12 supported by the roller 16. The cleaner 38 scrapes off the toner remaining on the intermediate transfer belt 12 after the secondary transfer and collects it in the waste toner box 40. Similarly to the secondary transfer roller 34, the cleaner 38 can also be retracted to a position where it is not in contact with the intermediate transfer belt 12 by a retracting mechanism (not shown).

  A paper feed cassette 42 is detachably disposed below the printer 10. The sheets S stacked and accommodated in the sheet feeding cassette 42 are sent out one by one from the uppermost one to the conveying path 46 by the rotation of the sheet feeding roller 44.

  The conveyance path 46 extends from the paper feed cassette 42 to the paper discharge tray 11 through the nip portion of the timing roller pair 48, the secondary transfer region 36, and the fixing unit 50. The timing roller pair 48 is for feeding the paper S sent from the paper feed cassette 42 to the transfer area 36 in synchronization with the image on the intermediate transfer belt 12.

  A timing sensor 52 is disposed in the vicinity of the timing roller pair 48. The timing sensor 52 is for detecting that the leading edge of the paper S sent out from the paper feed cassette 42 to the transport path 46 is nipped by the timing roller pair 48. When the leading edge of the sheet S is detected by the timing sensor 52, the timing roller pair 48 temporarily stops its rotation, and then the sheet S is fed to the transfer area 36 in synchronization with the toner image on the intermediate transfer belt 12. To do.

  Further, a paper thickness sensor 54 is disposed so as to face one roller 48 a of the timing roller pair 48. The paper thickness sensor 54 detects the amount of movement of the roller 48a when the leading edge of the paper is nipped by the timing roller pair 48, whereby the paper is plain paper, thick paper or OHP sheet. Can be determined.

  The fixing unit 50 is supported by a pair of rollers (56, 58) and is rotationally driven in the direction of arrow B. The fixing unit 50 is pressed against the roller 56 via the fixing belt 60 and is driven to rotate in the direction of the arrow. A mouth-ra 62 is provided. In addition, a nip portion between the fixing belt 60 and the fixing roller 62 through which the sheet on which the toner image is secondarily transferred passes is a fixing region 64. The fixing belt 60 is heated by a heater (not shown).

[Printer operation overview]
Next, the operation of the printer 10 having the above configuration will be described. When an image signal is input from an external device (for example, a personal computer) to an image signal processing unit (not shown) of the printer 10, the image signal processing unit digitally converts the image signal into yellow, cyan, magenta, and black. A signal is generated and transmitted to the LED drive circuit for the print head.

  This drive circuit performs exposure by causing the print head portions (26Y, 26M, 26C, 26K) of the image forming units (20Y, 20M, 20C, 20K) to emit light based on the input digital signals. This exposure is performed with a time difference in the order of the print heads (26Y, 26M, 26C, 26K). Thereby, an electrostatic latent image for each color is formed on the surface of each photosensitive drum (22Y, 22M, 22C, 22K).

  The electrostatic latent images formed on the photosensitive drums (22Y, 22M, 22C, 22K) are developed by the developing devices (28Y, 28M, 28C, 28K), respectively, and become toner images of the respective colors. The toner images of the respective colors are sequentially superimposed on the intermediate transfer belt 12 that moves in the direction of arrow A by the action of each primary transfer roller (30Y, 30M, 30C, 30K) to which a positive primary transfer voltage is applied. Primary transcription.

  In this way, the superimposed toner image formed on the intermediate transfer belt 12 reaches the transfer region 36 as the intermediate transfer belt 12 moves. The superimposed color toner images are sent out from the paper feed cassette 42 to the conveyance path 46 by the action of the secondary transfer port-roller 34 to which a secondary transfer voltage having the same polarity as the primary transfer voltage is applied. The toner images of the respective colors are secondarily transferred collectively onto the sheet S passing through the transfer region 36 by driving the timing roller pair 48. The toner remaining on the intermediate transfer belt 12 after the secondary transfer is collected by the action of the cleaner 38 to which the positive polarity cleaning current is applied, and moves to the cleaning unit.

  The sheet S on which the toner image is secondarily transferred is sent to the fixing unit 50 through the conveyance path 46, and passes through the fixing region 64 where the toner image is heat-fixed on the sheet S. Then, the paper S is discharged to the paper discharge tray 11.

  The color image forming operation is performed as described above. In the case of a monochrome image, only the image forming unit 20K operates to form a black toner image on the intermediate transfer belt 12 based on the input monochrome image data. . Thereafter, similarly, the black toner image is secondarily transferred to the paper S in the transfer region 36, heated and fixed by the fixing unit 50, and the paper S is discharged to the paper discharge tray 11.

[Configuration and operation of developing device]
Each developing device (28Y, 28M, 28C, 28K) described above has basically the same configuration and is set to perform the same operation. Hereinafter, the configuration and operation of the developing device (collectively referred to as the developing device 28) will be described in detail. FIG. 2 is a schematic sectional view of the developing device 28 (including a description of the adjusting means 92).

  As shown in FIG. 2, the developing device 28 has a configuration in which a stirring screw 81, a supply screw 82, and a developing roller 83 are accommodated in a housing 80. The stirring screw 81, the supply screw 82, and the developing roller 83 are rotatably attached to the housing 80 so that their rotation axes are in the same direction (left and right direction in FIG. 2).

  In addition, a partition wall 84 that partitions the stirring screw 81 and the supply screw 82 is installed in the housing 80. Therefore, a stirring tank 85 on the side where the stirring screw 81 is located and a supply tank 86 on the side where the supply screw 82 are located are formed in the housing 80 with the partition wall 84 as a boundary. The developing roller 83 is in a position facing the partition wall 84 in the supply tank 86 and is exposed in the supply tank 86.

  However, the partition wall 84 has a configuration in which communication portions for communicating the stirring tank 85 and the supply tank 86 are provided on both end sides (left and right sides in FIG. 2). Thus, a circulation path including the stirring tank 85 and the supply tank 86 is formed in the housing 80. The agitating screw 81 and the supply screw 82 are spiral type screws, and when these are rotated, the developer is circulated and conveyed in the circulation path as shown by broken line arrows in FIG. Note that the terms “upstream” and “downstream” used in the following description mean “upstream” and “downstream” with respect to the flow of this circulating conveyance.

  In the agitation tank 85, the developer is conveyed while being agitated by the rotation of the agitation screw 81. In the supply tank 86, the developer is conveyed by the rotation of the supply screw 82. In the process, a part of the developer is supplied to the developing roller 83. The developing roller 83 uses the developer supplied from the supply tank 86 to develop the electrostatic latent image formed on the photosensitive drum.

  A replenishment port 87 for replenishing the developer is provided on the upstream side of the agitation tank 85. The supply port 87 is formed by opening the housing 80 at a position indicated by a broken line in FIG. The developer replenished from the replenishment port 87 to the upstream side of the agitation tank 85 joins the circulation path. Note that the amount of developer supplied from the supply port 87 (replenishment amount) can be adjusted.

  Further, the supply tank 86 is provided with a discharge port 88 through which the developer branched from the circulation path on the downstream side of the supply tank 86 (developer that is excessive in the circulation path) is discharged. The discharge port 88 is formed by opening the housing 80 at the downstream end of the supply tank 86. Further, the discharge port 88 is provided with a shutter 89 that can adjust the opening width.

  FIG. 3 is a diagram illustrating a configuration example of the shutter 89 (a diagram when viewed in the direction A in FIG. 2). As shown in the figure, the shutter 89 is supported on both sides by, for example, a guide 89a extending in the moving direction of the shutter 89, and by moving along the guide 89a, the opening width of the discharge port 88 is adjusted ( Including closing the outlet 88). The wider the opening width of the discharge port 88, the easier the developer is discharged from there. Therefore, by adjusting the opening width of the discharge port 88, the amount of developer (discharge amount) discharged from the discharge port 88 is adjusted.

  In addition, as a mechanism for adjusting the opening width of the discharge port 88, a mechanism other than the above may be employed. As an example, an adjustment lid 90 may be provided in the vicinity of the discharge port 88 as shown in FIGS. The adjustment lid 90 shown in FIG. 4 has a plate shape, and the opening width of the discharge port 88 is adjusted by rotating around a shaft 91 provided on one end thereof. Further, the adjustment lid 90 shown in FIG. 5 rotates around a shaft 91 provided at the center thereof, and thereby the opening width of the discharge port 88 is adjusted.

  As shown in FIG. 2, a first detection means S <b> 1 for detecting the developer amount at that position is installed at a predetermined position near the downstream of the stirring tank 85. Further, a second detection means S2 for detecting the developer amount at that position is provided at a predetermined position near the downstream of the supply tank 86. The first detection means S1 may be installed on the most downstream side of the stirring tank 85, and the second detection means S2 may be installed on the most downstream side of the supply tank 86.

  Note that a non-contact type magnetic sensor is used as the first detection unit S1 and the second detection unit S2, and also serves as a toner concentration detection sensor. Further, the developing device 28 is based on the developer amount (first detection amount X1) detected by the first detection unit S1 and the developer amount (second detection amount X2) detected by the second detection unit S2. An adjusting means 92 is provided for adjusting the developer replenishment amount and the discharge amount.

  The adjustment unit 92 is constituted by, for example, a microcomputer, and can grasp both the developer amount and the toner density based on the output of each detection unit (S1, S2) that is a magnetic sensor. This principle will be described below.

  The adjusting unit 92 always counts the output of the magnetic sensor during driving of the magnetic sensor, and can obtain information of the waveform (graph showing the relationship between the driving time and the count value) illustrated in FIG. it can. Here, when the absolute value of the count value is large, it can be determined that the amount of carrier is small. From this, it can be determined that the toner ratio of the developer is high or the amount of developer is small. Conversely, when the absolute value of the count value is small, it can be determined that the amount of carrier is large. From this, it can be determined that the toner ratio of the developer is low or the amount of developer is large.

  Furthermore, when the width of the waveform shown in FIG. 6 is wide, it can be determined that the carrier amount is unstable and the developer is small. Conversely, when the width is narrow, it can be determined that the carrier amount is stable and the developer amount is large. From the above, the adjusting unit 92 can grasp the developer amount at the position of the magnetic sensor based on the absolute value and width of the count value. Further, the toner density is calculated by calculating a deviation amount of the next measured count value using the first measured count value as a reference value, and further multiplying the calculated result by a predetermined coefficient. The processing for deriving the developer amount and the toner density in this way may be performed by each detection means (S1, S2) itself.

  Next, the adjustment of the developer replenishment amount and the discharge amount performed by the adjustment unit 92 will be described more specifically. This adjustment is performed based on a result of comparing each of the first detection amount X1 and the second detection amount X2 with a predetermined reference value Y indicating an appropriate developer amount.

  More specifically, the adjusting unit 92 is a situation where both the first detection amount X1 and the second detection amount X2 are larger than the reference value Y (situation A), both the first detection amount X1 and the second detection amount X2. Is smaller than the reference value Y (situation B), the first detected amount X1 is larger than the reference value Y, the second detected amount X2 is smaller than the reference value Y (situation C), and the first detected amount X1 is the reference value. The content of adjustment is switched according to which of the situations (situation D) in which the second detection amount X2 is smaller than Y and greater than the reference value Y.

  Hereinafter, the contents of the adjustment will be described with reference to the graphs shown in FIGS. 7 to 10 are graphs showing the relationship between the position on the circulation path (horizontal axis) and the developer amount (vertical axis) under each situation, and the reference value Y is indicated by a broken line. The amount of developer inferred from the detection result of each detection means (S1, S2) is shown by a solid line.

  First, in a situation where both the first detection amount X1 and the second detection amount X2 are larger than the reference value Y (situation A), as shown in the graph of FIG. 7, the developer amount is the reference in the most part of the circulation path. It can be said that it is larger than the value Y. Therefore, the adjustment unit 92 performs a process of increasing the developer discharge amount and reducing the replenishment amount as usual as the adjustment process corresponding to the situation A. At this time, the discharge amount may be maximized or the replenishment amount may be minimized.

  As a result, the amount of developer in the circulation path gradually decreases and approaches the reference value Y. The process may be performed until at least one of the first detection amount X1 and the second detection amount X2 falls below the reference value Y, or until both of them fall below the reference value Y. Also good.

  Further, in a situation where both the first detection amount X1 and the second detection amount X2 are smaller than the reference value Y (situation B), as shown in the graph of FIG. 8, the developer amount is the reference in the most part of the circulation path. It can be said that it is smaller than the value Y. Therefore, the adjustment unit 92 performs a process of decreasing the developer discharge amount and increasing the replenishment amount as the adjustment process corresponding to the situation B. At this time, the discharge amount may be minimized or the replenishment amount may be maximized.

  As a result, the amount of developer in the circulation path gradually increases and approaches the reference value Y. The process may be performed until at least one of the first detection amount X1 and the second detection amount X2 exceeds the reference value Y, or until both of them exceed the reference value Y. Also good.

  Further, in the situation (situation C) where the first detection amount X1 is larger than the reference value Y and the second detection amount X2 is smaller than the reference value Y, the developer amount on the circulation path is approximately as shown in the graph of FIG. . In this situation, it can be said that the developer replenishment is excessive and the developer discharge is excessive. In this case, the adjustment unit 92 performs the following first to fourth adjustment processes as the adjustment process corresponding to the situation C.

  As processing relating to developer discharge, first adjustment processing for reducing the discharge amount from normal is performed. However, it is known from the detection result of the first detection means S1 that there is much developer on the downstream side of the stirring tank 85. Therefore, the second adjustment process for increasing the discharge amount from the current state is performed after the elapse of a predetermined first time from the start of the first adjustment process. The first time is a time during which the developer is transported from the position where the first detection unit S1 is installed to the position where the second detection unit S2 is installed (which is obtained in advance by experiments, calculations, or the like). Is set.

  In addition, as processing related to developer replenishment, first, third adjustment processing for reducing the replenishment amount from normal is performed. However, it is known from the detection result of the second detection means S2 that there is little developer on the downstream side of the supply tank 86. Therefore, after the elapse of a predetermined second time from the start of the third adjustment process, a fourth adjustment process for increasing the supply amount from the current state is performed. The second time is a time (determined in advance by experiment, calculation, etc.) for the developer to be transported from the position where the second detection means S2 is installed to the position where the replenished developer joins the circulation path. Is set).

  In a situation where the first detection amount X1 is smaller than the reference value Y and the second detection amount X2 is larger than the reference value Y (situation D), the developer amount on the circulation path is approximately as shown in the graph of FIG. . In this situation, it can be said that developer replenishment is insufficient and developer discharge is insufficient. In this case, the adjustment unit 92 performs the following fifth to eighth adjustment processes as the adjustment process corresponding to the situation D.

  As a process related to the discharge of the developer, first, a fifth adjustment process for increasing the discharge amount than usual is performed. However, it is known from the detection result of the first detection means S1 that there is little developer on the downstream side of the stirring tank 85. Therefore, the sixth adjustment process for reducing the emission amount from the current state is performed after the first time described above from the start of the first adjustment process.

  In addition, as a process related to developer replenishment, first, a seventh adjustment process for increasing the replenishment amount than usual is performed. However, it is known from the detection result of the second detection means S2 that there is much developer on the downstream side of the supply tank 86. For this reason, after the elapse of the second time described above from the start of the seventh adjustment process, an eighth adjustment process for reducing the replenishment amount from the current state is performed.

  Note that the developer bias in the circulation path and the ease of occurrence of excess and deficiency depend on the developer conveyance speed and fluidity in the circulation path. As a factor that affects the developer conveyance speed, for example, setting switching of the print mode (plain paper mode / thick paper mode) can be mentioned. That is, in the plain paper mode (high linear speed), the developer transport speed is relatively fast, and in the thick paper mode (low linear speed), the developer transport speed is relatively slow. When the developer transport speed is increased, the force for pushing the developer to the discharge port 88 is increased and the discharge amount is increased. Conversely, when the developer transport speed is decreased, the force for pushing the developer to the discharge port 88 is decreased. Reducing emissions.

  Further, as a factor that affects the fluidity of the developer, for example, a change in environmental conditions such as an environmental temperature can be cited. Even if the opening width of the discharge port 88 is the same, if the flowability of the developer increases, the developer easily flows out from the discharge port 88 and the discharge amount increases, and if the flowability of the developer decreases, the developer Becomes difficult to flow out from the discharge port 88, and the discharge amount is reduced.

  In consideration of the above circumstances, the adjusting unit 92 monitors factors (such as the above-described print mode and environmental conditions) that affect the developer conveyance speed or fluidity in the circulation path, and according to the results of this monitoring. Change the contents of the adjustment process described above. For example, when the above-described print mode and environmental conditions change, the adjustment unit 92 performs the first time length, the second time length, and the operation amount (replenishment amount) of the first to eighth adjustment processes described above. Alternatively, a part or all of the degree of increase / decrease in the discharge amount is changed so as to suit the changed printing mode and environmental conditions.

  As a result, even if the developer conveyance speed or fluidity varies, the adjustment accuracy of the developer replenishment amount and the discharge amount can be maintained satisfactorily. Therefore, it is possible to suppress problems such as density unevenness due to poor supply of developer and overflow of developer due to excessive supply.

  Next, a control flow regarding adjustment of the developer replenishment amount and discharge amount will be described with reference to the flowchart shown in FIG.

  At the stage where the control is started, the developer discharge amount and the replenishment amount are set to normal amounts (predetermined amounts). First, each detection means (S1, S2) detects the developer amount at that position, and grasps the first detection amount X1 and the second detection amount X2 (step S1). Next, the adjusting unit 92 determines whether or not the first detection amount X1 is larger than the reference value Y (step S2), and further determines whether or not the second detection amount X2 is larger than the reference value Y (step S2). S3 or S4).

  When the first detection amount X1 is larger than the reference value Y (Yes in step S2) and the second detection amount X2 is larger than the reference value Y (Yes in step S3), that is, in the situation A, the adjusting means 92 executes the adjustment process corresponding to the situation A already described (step S5). Further, when the first detection amount X1 is larger than the reference value Y (Yes in Step S2) and the second detection amount X2 is smaller than the reference value Y (No in Step S3), that is, in the situation C, The adjustment unit 92 executes an adjustment process corresponding to the situation C that has already been described (step S6).

  If the first detection amount X1 is smaller than the reference value Y (No in step S2) and the second detection amount X2 is larger than the reference value Y (Yes in step S4), that is, if the situation D, the adjustment is performed. The means 92 executes an adjustment process corresponding to the situation D that has already been described (step S7). Further, when the first detection amount X1 is smaller than the reference value Y (No in step S2) and the second detection amount X2 is smaller than the reference value Y (No in step S4), that is, in the situation B, The adjusting unit 92 executes an adjustment process corresponding to the situation B that has already been described (step S8).

  After the execution of any one of the processes in steps S5 to S8, when both (or one) detection amounts of the respective detection means reach the reference value Y (Yes in step S9), the current set values (for example, The first time length, the second time length, and the setting values related to the operation amounts of the first to eighth adjustment processes) are stored (step S10), and the current control is stopped. On the other hand, when the reference value Y has not been reached (No in step S9), the process in step S1 is performed again. In this way, the developer replenishment amount and discharge amount are appropriately adjusted. However, the series of processes in steps S1 to S10 described above is merely an example of a control flow relating to the adjustment of the developer replenishment amount and the discharge amount, and the content of the control flow is not limited thereto.

[Others]
As described above, the developing device 28 includes the stirring tank 85 that stirs the developer and the supply tank 86 that supplies the developer to the developing roller 83, and is a circulation path that includes the stirring tank 85 and the supply tank 86. Circulates and conveys the developer. Further, the developing device 28 includes a replenishing unit that replenishes the developer upstream of the agitation tank 85 and joins the circulation path, a discharge unit that discharges the developer branched from the circulation path downstream of the supply tank 86, First detection means S1 for detecting the developer amount at a predetermined position near the downstream of the stirring tank 85, and second detection means S2 for detecting the developer amount at a predetermined position near the downstream of the supply tank 86. I have.

  Further, the developing device 28 includes an adjusting unit 92 that adjusts the developer replenishment amount and the discharge amount based on the detection results of the first detection unit S1 and the second detection unit S2. Therefore, according to the developing device 28, it is possible to more appropriately adjust the replenishment amount and the discharge amount of the developer as compared with, for example, the adjustment based on the detection result of only one detection unit. In the present embodiment, both the supply amount and the discharge amount of the developer are adjusted based on the detection results of the first detection unit S1 and the second detection unit S2. Instead, the supply amount and the discharge amount are adjusted. Only one of the quantities may be adjusted.

  Further, the discharge port for discharging the developer is not limited to a mode in which only one discharge port is provided as in the present embodiment, but a discharge port for adjusting the developer amount in addition to the main discharge port. May be provided separately. In this embodiment, a magnetic sensor is used as means for detecting the developer amount. However, a liquid level sensor (piezoelectric sensor), an optical sensor, or the like disposed inside the developing device may be used. However, when a magnetic sensor is used as in this embodiment, it can be used as a toner concentration detection sensor, which is preferable in that the manufacturing cost can be reduced.

  The present invention can be used in, for example, a developing device employing a trickle developing system.

10 Printer (image forming device)
11 Paper discharge tray 12 Intermediate transfer belt 14, 16, 18 Roller 20Y, 20M, 20C, 20K Image forming unit 22Y, 22M, 22C, 22K Photosensitive drum 24Y, 24M, 24C, 24K Charger 26Y, 26M, 26C, 26K Print head portion 28Y, 28M, 28C, 28K, 28 Developing device 30Y, 30M, 30C, 30K Primary transfer roller 32Y, 32M, 32C, 32K Cleaner 34 Secondary transfer roller 36 Transfer area 38 Cleaner 40 Waste toner box 42 Paper feed cassette 44 Feed roller 46 Conveying path 48 Timing roller pair 48a Roller 50 Fixing unit 52 Timing sensor 54 Thick paper sensor 56, 58 Roller 60 Fixing belt 62 Fixing roller 64 Fixing area 80 Housing 81 Stirring screw 82 Screw 83 developing roller 84 partition wall 85 stirred tank 86 feed tank 87 supply inlet 88 outlet 89 shutter 89a guide 90 for regulating cap 91 axis 92 adjusting device S1 first detecting device S2 second detecting means

Claims (13)

A stirring tank for stirring the developer and a supply tank for supplying the developer to the developing roller;
A developing device that circulates and conveys a developer in a circulation path including the stirring tank and the supply tank,
Replenishment means for replenishing developer upstream of the agitation tank and joining the circulation path;
Discharging means for discharging the developer branched from the circulation path on the downstream side of the supply tank;
First detection means for detecting a developer amount at a first position near the downstream of the stirring tank;
Second detection means for detecting a developer amount at a second position that is closer to the downstream of the supply tank;
A developing device, comprising: an adjusting unit that adjusts both a replenishment amount and a discharge amount of the developer based on detection results of the first detection unit and the second detection unit. The adjusting means includes
The developing device according to claim 1, wherein each detection result of the first detection unit and the second detection unit is compared with a predetermined reference value, and the adjustment is performed based on the comparison result. The adjusting means includes
When the detection result of the first detection means is larger than the reference value and the detection result of the second detection means is smaller than the reference value,
3. The adjustment process includes a first adjustment process for decreasing the discharge amount and a second adjustment process for increasing the discharge amount after a predetermined first time has elapsed from the start of the first adjustment process. Development device. The adjusting means includes
When the detection result of the first detection means is larger than the reference value and the detection result of the second detection means is smaller than the reference value,
The adjustment process includes a third adjustment process for decreasing the replenishment amount and a fourth adjustment process for increasing the replenishment amount after a predetermined second time has elapsed from the start of the third adjustment process. Development device. The adjusting means includes
When the detection result of the first detection means is smaller than the reference value and the detection result of the second detection means is larger than the reference value,
The adjustment process includes a fifth adjustment process for increasing the discharge amount and a sixth adjustment process for decreasing the discharge amount after a predetermined first time has elapsed since the start of the fifth adjustment process. Development device. The adjusting means includes
When the detection result of the first detection means is smaller than the reference value and the detection result of the second detection means is larger than the reference value,
The adjustment process includes a seventh adjustment process for increasing the replenishment amount and an eighth adjustment process for decreasing the replenishment amount after a predetermined second time has elapsed from the start of the seventh adjustment process. Development device.   The developing device according to claim 3, wherein the first time is set to a time during which the developer is transported from the first position to the second position.   The developing device according to claim 4 or 6, wherein the second time is set to a time during which the developer is conveyed from the second position to the joining position. The adjusting means includes
When the detection results of the first detection means and the second detection means are both larger than the reference value,
The process of increasing the discharge amount and decreasing the supply amount until the detection result of the first detection unit or the second detection unit falls below the reference value as the adjustment process. The developing device according to any one of the above. The adjusting means includes
When the detection results of the first detection means and the second detection means are both smaller than the reference value,
10. The adjustment according to claim 2, wherein the adjustment is performed by decreasing the discharge amount and increasing the replenishment amount until a detection result of the first detection unit or the second detection unit exceeds the reference value. The developing device according to any one of the above. The adjusting means includes
The developing device according to claim 2, wherein the discharge amount is adjusted by adjusting an opening width of a discharge port through which the developer is discharged. The adjusting means includes
Monitoring factors affecting the developer transport speed or fluidity in the circuit;
The developing device according to claim 2, wherein the content of the adjustment process is changed according to the monitoring result.   An image forming apparatus comprising the developing device according to claim 1.