JP6287617B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus.

  In an electrophotographic image forming apparatus, toner is attached to an electrostatic latent image formed on the surface of a photoconductor and developed to form a toner image on the photoconductor. In the development, for example, a two-component developer composed of toner and a carrier that is magnetic particles is used. The developer is circulated and conveyed while being stirred in the developing device, and the toner and the carrier are frictionally charged with each other.

  In the system using the above two-component developer, the toner is consumed by the development, and new toner for the consumed amount is replenished. On the other hand, the carrier is used repeatedly without being consumed by development. For this reason, the carrier in the developing device gradually deteriorates. Therefore, a trickle development method has been proposed in which a new carrier is supplied together with the toner, and the overflowed developer is gradually discharged to the outside. By adopting the trickle developing method, the carrier in the developing device can be replaced and the deterioration level of the carrier can be suppressed within a certain range (see, for example, Patent Document 1).

  In this trickle developing system, if the amount of developer in the developing device increases too much, the load on the screw that stirs and conveys the developer increases, and the screw may be damaged. On the other hand, if the amount of the developer in the developing device is excessively reduced, uneven supply of the developer occurs, and there is a possibility that problems such as blurring occur in the formed image. Therefore, in the trickle development method, it is important to stabilize the developer amount in the developing device within an appropriate range.

JP-A-8-334977

  However, the amount of developer discharged in the trickle development method greatly depends on the fluidity of the developer. The developer fluidity increases when the charge amount decreases, such as immediately after the developer is charged or after the developer is stopped stirring, and decreases when the charge amount increases. When the flowability of the developer is high, the developer tends to overflow, so the discharge amount becomes excessive. When the flowability is low, the developer becomes difficult to overflow, and the discharge amount becomes too small. In the technique described in Patent Document 1, since the flowability of the developer is not considered at all, for example, when the flowability of the developer is high, the developer is excessively discharged. In this case, the amount of developer in the developing device cannot be stabilized, which causes a problem. Patent Document 1 describes that a magnet is attached to a sliding portion of a shutter that opens and closes a developer supply port and a discharge port. However, the technique described in Patent Document 1 is intended to improve the sealing performance and is not intended to stabilize the amount of developer in the developing device.

  The present invention has been made in view of the above circumstances, and provides a developing device and an image forming apparatus that adjust the discharge amount of the developer in consideration of the fluidity of the developer.

  The above object is achieved by the following means.

  (1) The electrostatic latent image on the image carrier is developed by a developer tank that contains a developer containing toner and a magnetic carrier, and a developer that is replenished in the developer tank and circulated in the circulation path. A developing path, a connection path following the discharge path for discharging a part of the developer in the developer tank from the circulation path, and a connection path provided in the connection path, and the developer in the circulation path is directed to the discharge section. A reverse conveyance unit that conveys the developer in a direction opposite to the direction, a deriving path that can bypass the reverse conveying unit and that can lead the developer to the discharge unit, and deters the developer from being derived in the deriving path A possible resistance member, an acquisition unit for acquiring information on the fluidity of the developer in the developer tank as fluidity information, and the discharge amount of the developer by controlling the resistance member based on the fluidity information And a control unit for adjusting the developing device.

  (2) The developing device according to (1), wherein the acquisition unit acquires, as the fluidity information, an amount of developer that passes through the lead-out path per unit time.

  (3) The resistance member includes a magnetic body that is movably provided in the vicinity of the lead-out path, and the control unit suppresses the lead-out of the developer by causing the magnetic body to approach the lead-out path. The developing device according to (1) or (2), wherein the developer is allowed to be led out by separating the magnetic body from the lead-out path.

  (4) The resistance member includes an electromagnet provided in the vicinity of the lead-out path, and the control unit suppresses the lead-out of the developer by increasing a current supplied to the electromagnet, and supplies the electromagnet to the electromagnet. The developing device according to (1) or (2), wherein the developer is allowed to be led out by reducing a current to be generated.

  (5) The resistance member includes a movable wall that is movably provided in the lead-out path, and the control unit moves the movable wall to a position that blocks a part of the lead-out path, thereby deriving the developer. The developing device according to (1) or (2), wherein the developer is allowed to be led out by suppressing and retracting the movable wall to a position where the lead-out path is not blocked.

  (6) The controller determines from the fluidity information whether or not the developer in the developer tank has high fluidity. If the fluidity is determined to be high, the resistance member determines whether the developer is fluid. The developing device according to any one of (1) to (5), which suppresses derivation.

  (7) The control unit determines the degree of fluidity of the developer in the developer tank from the fluidity information at a predetermined timing, and derives the developer by the resistance member according to the degree of fluidity. The developing device according to any one of the above (1) to (5), which determines a time for inhibiting the toner.

  (8) The acquisition unit acquires, as fluidity information, at least one of the temperature outside the developer tank, the humidity, and the leaving time in which the circulation is stopped and the developer is left unattended. The developing device according to any one of 7).

  (9) The developing device according to any one of (1) to (8), wherein the acquisition unit acquires, as the fluidity information, an amount of developer passing through the lead-out path by a magnetic center or an optical sensor. .

  (10) It further includes a weight detection sensor that detects the weight of the developer discharged from the discharge unit, and the acquisition unit indicates an increase rate of the developer weight detected by the weight detection sensor. The developing device according to any one of (1) to (9), which is acquired as:

  (11) The electrostatic latent image on the image carrier is developed by a developer tank that contains a developer containing toner and a magnetic carrier, and a developer that is replenished in the developer tank and circulated in the circulation path. A developing path, a connection path following the discharge path for discharging a part of the developer in the developer tank from the circulation path, and a connection path provided in the connection path, and the developer in the circulation path is directed to the discharge section. A reverse conveyance unit that conveys the developer in a direction opposite to the direction, a deriving path that can bypass the reverse conveying unit and that can lead the developer to the discharge unit, and deters the developer from being derived in the deriving path A possible resistance member, an acquisition unit for acquiring information on the fluidity of the developer in the developer tank as fluidity information, and the discharge amount of the developer by controlling the resistance member based on the fluidity information A control unit for adjusting the image and an image forming unit Image forming apparatus.

  According to the developing device of the present invention, the operation of the magnetic material is controlled based on the fluidity information. Accordingly, the developer discharge amount can be adjusted in consideration of the flowability of the developer, so that the developer amount in the developing device can be stabilized.

1 is a cross-sectional view for explaining an image forming apparatus according to a first embodiment. It is a schematic block diagram for demonstrating the image development apparatus shown by FIG. FIG. 3 is a schematic configuration diagram illustrating an enlarged discharge unit of the developing device illustrated in FIG. 2. It is sectional drawing along the II line | wire of FIG. It is a flowchart which shows an example of the discharge amount adjustment process which concerns on this embodiment. It is a figure which shows a mode that discharge amount adjustment processing is performed in the developing device which concerns on 1st Embodiment. It is sectional drawing along the II-II line of FIG. It is a schematic block diagram for demonstrating the developing device which concerns on 2nd Embodiment. It is sectional drawing along the III-III line of FIG. It is a schematic block diagram for demonstrating the developing apparatus which concerns on 3rd Embodiment. It is a figure which shows the relationship between the number of printed sheets and the developer amount in a developing device. It is a figure which shows the relationship between the fluidity | liquidity of a developer, and a saturated developer amount.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

(First embodiment)
FIG. 1 is a cross-sectional view for explaining the image forming apparatus according to the first embodiment.

  The image forming apparatus A shown in FIG. 1 is also called a tandem type color image forming apparatus, and performs color image formation by four sets of image forming units. The image forming apparatus A forms an image of image data on a sheet such as an image forming sheet (recording medium) using an electrophotographic image forming process.

  The four image forming units include an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, and an image forming unit that forms a cyan (C) color image. The unit 10C is an image forming unit 10K that forms a black (K) color image.

  The image forming unit 10Y includes a photosensitive drum 1Y as an image carrier, and a charging unit 2Y, an optical writing unit 3Y, a developing device 4Y, and a photosensitive drum cleaning device 5Y disposed around the photosensitive drum 1Y. Similarly, the image forming unit 10M includes a photosensitive drum 1M as an image carrier, and a charging unit 2M, an optical writing unit 3M, a developing device 4M, and a photosensitive drum cleaning device 5M disposed around the photosensitive drum 1M. The image forming unit 10C includes a photosensitive drum 1C as an image carrier, and a charging unit 2C, an optical writing unit 3C, a developing device 4C, and a photosensitive drum cleaning device 5C arranged around the photosensitive drum 1C. The image forming unit 10K includes a photosensitive drum 1K as an image carrier, and a charging unit 2K, an optical writing unit 3K, a developing device 4K, and a photosensitive drum cleaning device 5K disposed around the photosensitive drum 1K. The photosensitive drums 1Y, 1M, 1C and 1K of the image forming units 10Y, 10M, 10C and 10K, charging units 2Y, 2M, 2C and 2K, optical writing units 3Y, 3M, 3C and 3K, and developing devices 4Y, 4M, 4C, and 4K and the photosensitive drum cleaning devices 5Y, 5M, 5C, and 5K have the same functions. Therefore, in the following description, symbols Y, M, C, or K are not used unless otherwise specified.

  The developing device 4 contains a two-component developer (hereinafter referred to as “developer”) including a carrier and toner, and a trickle developing method is adopted as a developing method. Details of the developing device 4 will be described later.

  In the image forming process of the present embodiment, the photosensitive drum 1 and the intermediate transfer belt 6 are used as the image carrier.

  The intermediate transfer belt 6 is an endless belt, is constructed by a plurality of rollers, and is supported so as to be able to run. The toner images of the respective colors formed on the image forming units 10Y, 10M, 10C and 10K are sequentially transferred onto the intermediate transfer belt 6 running by the primary transfer units 7Y, 7M, 7C and 7K. As a result, a color image (toner image) in which layers of each color (Y, M, C, K) are superimposed is primarily transferred onto the intermediate transfer belt 6.

  The paper transport unit 20 transports the paper S. The paper S is accommodated in the paper feed trays 291, 292 and 293, fed by the first paper feed unit 21, conveyed to the secondary transfer unit 30 through the loop forming roller pair 22 and the registration roller pair 23. The

  The secondary transfer unit 30 secondarily transfers the color toner image on the intermediate transfer belt 6 onto the paper S. The secondary transfer unit 30 includes a roller or a belt disposed in the vicinity of the intermediate transfer belt 6 and downstream of the paper transport unit 20. The secondary transfer unit 30 transfers the paper S sent from the paper transport unit 20 to the intermediate transfer belt 6 side. The color image is transferred onto the paper S. After the secondary transfer, the sheet S is sent to the fixing device 50. The toner image on the sheet S is melted and fixed on the sheet S on which the color image is transferred by applying heat and pressure at the nip portion N of the fixing device 50. Then, the paper S is discharged out of the apparatus by the paper discharge roller 25.

  Each unit of the image forming apparatus A is connected to the control unit 90 and is appropriately controlled by the control unit 90. A CPU (not shown) configured as a part of the control unit 90 executes a process for obtaining developer fluidity information in the developing device 4 and a process for adjusting the developer discharge amount. Details of these processes will be described later. A program corresponding to these processes is stored in a storage unit (not shown) included in the control unit 90. Each function of the above-described units of the image forming apparatus A is exhibited by the CPU executing a corresponding program.

  Note that the image forming apparatus A may include components other than the components described above, or may not include some of the components described above.

  Next, an electrophotographic process for forming an image on a sheet by the image forming apparatus A will be described.

  First, a document is placed on a document table having a slit SL on the top, and the placed document is scanned and exposed by an optical system of a scanning exposure device of the image reading device SC, and reflected light from the document is reflected by a mirror. Via a line image sensor and photoelectrically converted. The image information signal for each color generated by photoelectric conversion is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like by an image processing unit (not shown), and then image formation of the corresponding color is performed. Input to the optical writing unit 3 of the unit 10.

  The optical writing unit 3 of the image forming unit 10 writes an image information signal to the photosensitive drum 1 and forms a latent image on the photosensitive drum 1 based on the image information signal. Specifically, the photosensitive drum 1 has a photosensitive layer made of a resin such as polycarbonate including an organic photoconductor (OPC) on a metal substrate. The surface of the photosensitive drum 1 is charged by ions generated by a charging unit 2 formed of a corona discharge electrode such as a scorotron type, and the optical writing unit 3 scans and exposes the photosensitive drum 1 based on an image information signal. To do. The exposed portion of the charged photosensitive drum 1 has a reduced potential, and an electrostatic latent image corresponding to the image information signal is formed on the photosensitive drum 1. The developing device 4 uses an electrostatic force to develop the electrostatic latent image formed on the photosensitive drum 1 with toner, and a toner image corresponding to each color is formed.

  Here, the toner for development is charged on the same electrode as the photosensitive drum 1. For example, the photosensitive drum 1 is charged to the negative electrode. Of the region on the photosensitive drum 1 charged to the negative electrode, the toner charged to the negative electrode is attached only to the latent image portion whose potential has been lowered by the optical writing unit 3, and the electrostatic latent image is formed on the photosensitive drum 1. Can be formed. The electrostatic latent image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 6, and a toner image can be formed on the intermediate transfer belt 6. At this time, by charging the intermediate transfer belt 6 to the positive electrode, the transfer of the toner charged to the negative electrode to the intermediate transfer belt 6 can be promoted. On the intermediate transfer belt 6, patches that are not transferred to the paper S are formed for the purpose of correcting the printing density, color, or image forming position. The toner for forming the patch is charged to the negative electrode like the toner for forming the electrostatic latent image. Then, the toner image formed on the intermediate transfer belt 6 is secondarily transferred onto the paper S in the secondary transfer unit 30. At this time, by charging the sheet S to the negative electrode, the transfer of the toner image charged to the positive electrode by the intermediate transfer belt 6 onto the sheet S can be promoted.

[Developing device 4]
Next, the configuration of the developing device 4 will be described in detail.

  FIG. 2 is a schematic configuration diagram for explaining the developing device shown in FIG. FIG. 3 is an enlarged schematic configuration diagram showing the vicinity of the discharge portion of the developing device shown in FIG. 4 is a cross-sectional view taken along the line II of FIG.

  As illustrated in FIG. 2, the developing device 4 includes a developer tank 40, a supply unit 41, a connection unit 42, a discharge unit 43, and a developing roller 44.

  The developer tank 40 is a container that stores a developer in which toner and a carrier are mixed. The developer tank 40 is provided with a circulation path 400 for circulating the developer stored therein while stirring. The circulation path 400 is provided with a plurality of stirring screws 401. The developer is conveyed while being agitated by the rotation of each agitating screw 401 and circulates in the circulation path 400 as indicated by the white arrow.

  The replenishing unit 41 replenishes toner and a carrier into the developer tank 40 from a toner cartridge, a carrier cartridge, or the like (not shown) outside the developer tank 40. The toner and carrier may be replenished separately or may be replenished in a premixed state.

  The connecting portion 42 is provided in the developer tank 40 adjacent to the circulation path 400. The connection part 42 connects the circulation path 400 and the discharge part 43.

  The discharge portion 43 is provided in the developer tank 40 adjacent to the connection portion 42. The discharge unit 43 discharges the developer that has moved through the connection unit 42 to the outside of the developer tank 40.

  The developing roller 44 as a developing unit supplies toner to the photosensitive drum 1 and develops the electrostatic latent image on the photosensitive drum 1.

  Next, the connection part 42 and the discharge part 43 of the developing device 4 will be described in detail.

  As shown in FIG. 3, the connection portion 42 includes a connection path 420 and a reverse screw 421. The connection path 420 connects between the circulation path 400 and the discharge unit 43. On the connection path 420, a reverse screw 421 is provided. The reverse screw 421 serves as a reverse conveyance unit, and conveys the developer in a direction opposite to the direction in which the developer in the circulation path 400 is directed toward the discharge unit 43. That is, the reverse screw 421 conveys the developer to the circulation path 400 side.

  In addition, the connecting portion 42 has a lead-out path 422 that can bypass the reverse screw 421 and lead the developer to the discharge section 43 in parallel with the connecting path 420. The lead-out path 422 is formed so that, for example, the connection path 420 is extended outward and the developer can flow between the reverse screw 421 and the inner wall of the developer tank 40. In the vicinity of the entrance of the lead-out path 422, that is, in the vicinity of the upstream side of the lead-out path 422, a magnetic body 423 is movably provided as a resistance member. The magnetic body 423 moves so as to approach and separate from the lead-out path 422 by driving the motor by the control unit 90 or the like. For example, as shown in FIG. 4, the magnetic body 423 moves between a position above the lead-out path 422 and a position having the same height as the rotation axis of the reverse screw 421. The lead-out path 422 is provided with a sensor (not shown) that detects the amount of developer that passes through the lead-out path 422. For example, a magnetic sensor or an optical sensor is used as the sensor.

  As shown in FIG. 3, the discharge portion 43 is connected to the circulation path 400 via the connection portion 42. The discharge unit 43 has a discharge port 430 and a conveying screw 431. The transport screw 431 transports the developer sent from the connection unit 42 to the discharge port 430. The discharge port 430 discharges the developer conveyed by the conveyance screw 431 to the outside.

[Developer discharge control]
Next, a developer discharge amount adjustment process executed by the developing device 4 will be described.

  FIG. 5 is a flowchart illustrating an example of the discharge amount adjustment process according to the present embodiment. FIG. 6 is a diagram illustrating a state in which the discharge amount adjustment process is performed in the developing device according to the first embodiment. 7 is a cross-sectional view taken along line II-II in FIG. The processing shown in the flowchart of FIG. 5 is stored as a program in the storage unit of the control unit 90 and is executed by the CPU of the control unit 90.

  As shown in FIG. 5, the control unit 90 starts a developer discharge amount adjustment process (step S101). Specifically, the control unit 90 starts the discharge amount adjustment process at a predetermined timing such as when the power is turned on or when returning from the standby state, or at an arbitrary timing instructed by the user.

  Subsequently, the control unit 90 acquires fluidity information, which is information relating to the fluidity of the developer in the developer tank 40, as an acquisition unit (step S102). Specifically, the control unit 90 acquires the amount of developer that passes through the lead-out path 422 per unit time from a sensor provided in the lead-out path 422.

  Subsequently, the control unit 90 determines whether or not the fluidity of the developer in the developer tank 40 is high based on the fluidity information acquired in step S102 (step S103). Specifically, the control unit 90 determines whether or not the amount of developer passing through the derivation path 422 acquired as the fluidity information is greater than a predetermined threshold value. Here, when the amount of developer passing through is larger than the predetermined threshold, it is determined that the flowability of the developer is high, and when the amount of developer passing through is smaller than the predetermined threshold, the fluidity of the developer is It is judged to be low.

  When it is determined that the flowability of the developer is high (step S103: YES), the control unit 90 executes a discharge suppression operation for suppressing the amount of developer discharged from the developer tank 40 (step S104). Specifically, as shown in FIGS. 4 and 7, the control unit 90 causes the magnetic body 423 provided in the vicinity of the derivation path 422 to approach the derivation path 422. For example, as shown in the graph on the right side of FIG. 7, the control unit 90 increases the height of the center position of the magnetic body 423 to the same height as the center position of the rotating shaft of the reverse screw 421. The magnetic body 423 is moved. As a result, as shown in FIGS. 6 and 7, carriers that are magnetic particles contained in the developer are attracted and aggregated by the magnetic body 423, and the flow of the developer in the lead-out path 422 is suppressed. As a result, the derivation of the developer from the circulation path 400 to the discharge unit 42 is suppressed, and the discharge of the developer from the developer tank 40 is suppressed.

  On the other hand, when it is determined that the fluidity of the developer is low (step S103: NO), the control unit 90 sets the magnetic body 423 so as not to approach the lead-out path 422 and proceeds to the process of step S105. . In this case, the carrier is not attracted to the magnetic body 423, and the derivation of the developer in the derivation path 422 is not inhibited. Therefore, the developer is allowed to be discharged.

  Subsequently, the control unit 90 determines whether it is time to end the discharge amount adjustment process (step S105). The timing for ending the discharge amount adjustment processing is, for example, a predetermined timing such as when the power of the image forming apparatus A is shut off or switching to the standby state, or a timing when an instruction to end the processing is received from the user. Is set.

  When it is not time to end the discharge amount adjustment process (step S105: NO), the control unit 90 returns to the process of step S102 and continues the discharge amount adjustment process.

  When it is time to end the discharge amount adjustment process (step S105: YES), the control unit 90 ends the discharge amount adjustment process.

  As described above, according to the image forming apparatus A of the present embodiment, the operation of the magnetic body 423 is controlled based on the fluidity information. Thereby, since the discharge amount of the developer can be adjusted in consideration of the flowability of the developer, the developer amount in the developing device 4 can be stabilized.

  In addition, the image forming apparatus A acquires the amount of developer passing through the lead-out path 422 per unit time as fluidity information. Thereby, the fluidity of the developer can be accurately detected, and the discharge amount adjustment process can be executed more appropriately.

  In addition, the image forming apparatus A acquires the amount of developer passing through the lead-out path 422 by using a magnetic sensor or an optical sensor as fluidity information. Thereby, the amount of the developer passing through the lead-out path 422 can be detected without hindering the flow of the developer.

  Further, the image forming apparatus A includes a magnetic body 423 that is provided as a resistance member so as to be movable in the vicinity of the lead-out path 422. By causing the magnetic body 423 to approach the lead-out path 422, the lead-out of the developer is suppressed and separated. To permit the derivation of the developer. Thus, the developer discharge amount can be adjusted without providing a complicated mechanism in the developer tank 40. As a result, the manufacture and maintenance of the device are facilitated.

  In the above embodiment, the amount of developer passing through the lead-out path 422 per unit time is acquired as the fluidity information. However, the present invention is not limited to this. For example, a weight detection sensor that detects the weight of the developer discharged from the discharge unit 43 is provided outside the discharge unit 43, and the rate of increase in the developer weight detected by the weight detection sensor is acquired as fluidity information. May be. In this case, when the increase rate of the developer weight is increased, it can be determined that the developer fluidity is high, and when the developer weight increase rate is decreased, the developer fluidity is low. It can be judged that As a result, it is possible to detect the flowability of the developer and the tendency of the change in fluidity, and it is possible to appropriately adjust the discharge amount.

  In the above embodiment, the discharge amount adjustment process is described as being continuously executed until the process end timing, but the present invention is not limited to this. The discharge amount adjustment process may be executed at a predetermined timing set in advance.

  In the above-described embodiment, the fluidity is described as being determined in two stages of “high” or “low”, but the present invention is not limited to this. The fluidity may be determined in multiple stages, and the degree of the discharge suppression operation may be adjusted according to each stage. For example, the distance at which the magnetic body 423 approaches the lead-out path 422 may be changed according to the degree of fluidity.

  In the above embodiment, the amount of developer that passes through the lead-out path 422 per unit time is used as the fluidity information, but the present invention is not limited to this. As the fluidity information, the temperature / humidity outside the developer tank 40 or the leaving time which is the time during which the developer circulation is stopped and the developer is left may be used.

  In the following, an example of a case where the discharge amount adjustment process is executed at a predetermined timing set in advance, the fluidity is judged in multiple stages, and the temperature and humidity outside the developer tank 40 and the standing time are used as fluidity information. Will be described in detail.

[Modification 1]
The predetermined timing at which the discharge amount adjustment processing is executed may be, for example, when the power of the image forming apparatus A is turned on, when it returns from the standby state, when the developer is turned on, or every hour. For example, every time a certain driving time elapses.

  When the discharge amount adjustment process is executed, the control unit 90 acquires the temperature / humidity environment and the leaving time outside the developer tank 40 as fluidity information. The control unit 90 determines the operation time of the discharge suppression operation based on the acquired temperature / humidity environment and the leaving time and the determination matrix as shown in Table 1 and Table 2 stored in advance in the storage unit.

  Regarding the temperature and humidity environment shown in Table 1, HH indicates a high temperature and high humidity environment, for example, an environment having a temperature of 30 ° C. or higher and a humidity of 80% or higher. LL indicates an environment having a low temperature and a low humidity, for example, an environment having a temperature of less than 10 ° C. and a humidity of less than 15%. NN indicates an environment of a combination of temperature and humidity other than HH and LL. In the example shown in Table 1, the longer the standing time, the higher the developer fluidity. This is because when the developer is agitated and left to stand, the charge amount of the toner and the carrier contained in the developer is reduced, the resistance between the toner and the carrier is reduced, and the fluidity is increased.

  In the example shown in Table 1 and Table 2, for example, let us consider a case where the standing time is “6 hours”, the temperature is “20 ° C.”, and the humidity is “50%”. In Table 1, since the standing time is in the range of “0 to 12 hours” and the temperature and humidity environment is “NN”, the fluidity of the developer is determined to be “low”. Therefore, based on Table 2, the operation time of the discharge suppression operation is determined to be “3 minutes”. In this case, the control unit 90 performs the discharge suppression operation for 3 minutes.

  For example, let us consider a case where the standing time is “18 hours”, the temperature is “35 ° C.”, and the humidity is “85%”. In Table 1, since the standing time is in the range of “12 to 24 hours” and the temperature and humidity environment is “HH”, the fluidity of the developer is determined to be “high”. Therefore, based on Table 2, the operation time of the discharge suppression operation is determined to be “10 minutes”. In this case, the control unit 90 performs the discharge suppression operation for 10 minutes.

[Modification 2]
In the first modification, the fluidity of the developer is determined using the standing time and the temperature / humidity environment as the fluidity information, and the operation time of the discharge suppression operation is determined. However, the present invention is not limited to this. Furthermore, the fluidity may be determined in consideration of other factors, and the operation time of the discharge suppression operation may be determined.

  First, the case where the toner concentration, which is the mass ratio between the toner and the developer containing the toner, is considered in addition to the standing time and the temperature and humidity environment.

  Table 3 below shows an example of a judgment matrix for determining the operation time of the discharge suppression operation in consideration of the toner concentration in addition to the standing time and the temperature / humidity environment.

  The toner density level shown in Table 3 is determined based on the difference between the toner density in the developer tank 40 and a preset target toner density. For example, when the toner concentration in the developer tank 40 is higher than the target toner concentration by 1% or more, it is determined as “high”, and when it is lower than 1%, it is determined as “low”. When the difference between the toner density in the developer tank 40 and the target toner density is less than 1%, the toner density level is determined to be “center”. The target toner density is set to about 7%, for example. In the example shown in Table 3, under the same standing time and temperature / humidity environment conditions, it is considered that the higher the toner concentration, the lower the fluidity of the developer. It is set short. On the other hand, the lower the toner concentration, the higher the fluidity of the developer. Therefore, the lower the toner concentration, the longer the operation time of the discharge suppression operation is set.

[Modification 3]
Next, a case where the coverage during printing in addition to the standing time and the temperature / humidity environment is considered will be described. Coverage represents the ratio of the area of the printed page where toner is used to the total area of the page.

  Table 4 below shows a judgment matrix for determining the operation time of the discharge suppression operation in consideration of the coverage in the printing process performed before the execution of the discharge amount adjustment process in addition to the standing time and the temperature / humidity environment. An example is shown.

  The coverage levels shown in Table 4 are determined based on an average value of 1000 coverages printed immediately before executing the discharge amount adjustment process. For example, when the average value of coverage is 50% or more, the coverage level is determined to be “high”. When the average coverage value is 10% or more and less than 50%, the coverage level is determined to be “medium”, and when the average coverage value is less than 10%, the coverage level is determined to be “low”. In the example shown in Table 4, when the coverage level is “high” or “medium” under the same standing time and temperature / humidity environment, the developer fluidity is higher than when the coverage level is “low”. It is considered to be. Therefore, when the coverage level is “high” or “medium”, the operation time of the discharge suppression operation is set longer than when the coverage level is “low”.

[Modification 4]
Next, a case where the traveling distance of the developer is considered in addition to the standing time and the temperature / humidity environment will be described. The developer travel distance is a distance traveled by the developer replenished in the developing device 4 being circulated and conveyed. The travel distance of the developer is calculated from, for example, the rotational speed of the stirring screw 401.

  Table 5 below shows an example of a judgment matrix for determining the operation time of the discharge suppression operation when considering the developer travel distance at the time of executing the discharge amount adjustment processing in addition to the standing time and the temperature / humidity environment. Indicates.

  The developer travel distance level shown in Table 5 is determined based on the ratio between the predetermined developer durability life and the developer travel distance at the time of executing the discharge amount adjustment processing. For example, when the travel distance is less than 20% of the durable life, the travel distance level is determined as “initial”. If the mileage is 20% or more and less than 80% of the durable life, the mileage level is judged as “medium”, and if the mileage is 80% or more of the durable life, the mileage level is “durable”. It is judged as “the end”. In the example shown in Table 5, when the developer mileage level is “initial” under the same standing time and temperature / humidity environment conditions, the developer fluidity is higher than in the case of “medium” or “end of life”. It is thought to be higher. Therefore, when the developer travel distance level is “initial”, the operation time of the discharge suppression operation is set to be longer than in the case of “mid-term” or “end-of-life”.

  In addition to the examples shown in Tables 1 to 5, the image forming apparatus A takes into account the developer and fluidity in consideration of the toner and carrier charge amounts, the toner replenishment cycle, the continuous drive time of the developing device, and the like. May be determined and the operation time of the discharge suppression operation may be determined.

  Thus, by determining the fluidity level of the developer in the developer tank 40 from the fluidity information at a predetermined timing, and determining the operation time of the developer discharge inhibiting operation according to the fluidity level, It is possible to execute the discharge adjustment process with high accuracy and efficiency.

(Second Embodiment)
Next, an image forming apparatus according to the second embodiment will be described. Note that components similar to those of the image forming apparatus of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The configuration of the image forming apparatus of the second embodiment is different from the configuration of the image forming apparatus shown in FIG. 1 only in the configuration of the developing device 4, and the other configurations are the same.

  In the first embodiment, a movable magnetic body 423 is provided in the vicinity of the lead-out path 422 as a resistance member, and the developer discharge amount is adjusted by moving the magnetic body 423. However, an electromagnet may be used as the resistance member, and the developer discharge amount may be adjusted by the magnitude of the current flowing through the electromagnet. In the second embodiment, a case will be described in which an electromagnet is provided in the vicinity of the upstream side of the lead-out path 422 as a resistance member, and the developer discharge amount is adjusted by the magnitude of the current flowing through the electromagnet.

  FIG. 8 is a schematic configuration diagram for explaining the developing device according to the second embodiment. 9 is a cross-sectional view taken along line III-III in FIG.

  As shown in FIGS. 8 and 9, in the developing device 4, an electromagnet 424 is provided in the vicinity of the inlet of the outlet path 422, that is, in the vicinity of the upstream side of the outlet path 422. The magnitude of the current flowing through the electromagnet 424 is controlled by the control unit 90.

  The flow of the discharge amount adjustment process in the image forming apparatus of the second embodiment is the same as the flow of the discharge amount adjustment process in the image forming apparatus of the first embodiment shown in the flowchart of FIG.

  In the second embodiment, when executing the discharge suppression operation in the process of step S104 of FIG. 5, the control unit 90 supplies the current supplied to the electromagnet 424 as in the case where the fluidity is increased in the graph on the right side of FIG. Increase the size of. As the current supplied to the electromagnet 424 increases, the magnetic force of the electromagnet 424 increases. As a result, as shown in FIGS. 8 and 9, carriers that are magnetic particles contained in the developer are attracted and aggregated by the electromagnet 424, and the flow of the developer in the lead-out path 422 is suppressed. As a result, the derivation of the developer from the circulation path 400 to the discharge unit 43 is suppressed, and the discharge of the developer from the developer tank 40 is suppressed.

  On the other hand, if it is determined in step S103 that the developer has low fluidity, the control unit 90 proceeds to step S105 with the magnitude of the current supplied to the electromagnet 424 decreased. In this case, the carrier is not attracted to the electromagnet 424, and the lead-out of the developer in the lead-out path 422 is not suppressed. Therefore, the developer is allowed to be discharged.

  As described above, according to the image forming apparatus A of the second embodiment, by including the electromagnet 424 provided in the vicinity of the lead-out path 422 as a resistance member, by changing the magnitude of the current supplied to the electromagnet 424, Adjust the developer discharge amount. Accordingly, the developer discharge amount can be adjusted with a simple configuration without providing a complicated movable mechanism. As a result, the manufacture and maintenance of the apparatus are facilitated.

  Also in the second embodiment, the fluidity may be determined in multiple stages as in the first to fourth modifications of the first embodiment, and the application time of the discharge suppression operation may be changed.

(Third embodiment)
Next, an image forming apparatus according to a third embodiment will be described. Note that components similar to those of the image forming apparatus of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The configuration of the image forming apparatus of the third embodiment is different from the configuration of the image forming apparatus shown in FIG. 1 only in the configuration of the developing device 4, and the other configurations are the same.

  In the first embodiment, a movable magnetic body 423 is provided in the vicinity of the lead-out path 422 as a resistance member, and the developer discharge amount is adjusted by moving the magnetic body 423. However, a movable wall that is movably provided on the lead-out path 422 may be provided as a resistance member, and the developer discharge amount may be adjusted depending on the position of the movable wall. In the third embodiment, a case will be described in which a movable wall is provided on the lead-out path 422 as a resistance member, and the developer discharge amount is adjusted according to the position of the movable wall.

  FIG. 10 is a schematic configuration diagram for explaining a developing device according to the third embodiment. In FIG. 10, (A) shows a state in which the discharge of the developer is allowed, and (B) shows a state in which the discharge of the developer is suppressed.

  As shown in FIGS. 10A and 10B, in the developing device 4, a movable wall 425 is movably provided at the inlet on the upstream side of the lead-out path 422. The movable wall 425 moves between a position where the entrance of the lead-out path 422 is blocked and a position where there is no block by driving the motor by the control unit 90 or the like.

  The flow of the discharge amount adjustment process in the image forming apparatus of the third embodiment is the same as the flow of the discharge amount adjustment process in the image forming apparatus of the first embodiment shown in the flowchart of FIG.

  In the third embodiment, it is determined that the flowability of the developer is high in the process of step S103 in FIG. 5, and the control unit 90 performs the discharge suppression operation in the process of step S104, as shown in FIG. As described above, the movable wall 425 is moved to a position where the entrance of the outlet path 422 is blocked. The entrance of the lead-out path 422 is blocked by the movable wall 425, so that the developer flow in the lead-out path 422 is suppressed. As a result, the derivation of the developer from the circulation path 400 to the discharge unit 43 is suppressed, and the discharge of the developer from the developer tank 40 is suppressed.

  On the other hand, if it is determined in step S103 that the developer has low fluidity, the control unit 90 moves the movable wall 425 to a position that does not block the entrance of the lead-out path 422 as shown in FIG. In the moved state, the process proceeds to step S105. In this case, the lead-out of the developer in the lead-out path 422 is not inhibited, and the developer is allowed to be discharged.

  As described above, according to the image forming apparatus A of the third embodiment, the developer discharge amount includes the movable wall 425 provided in the lead-out path 422 as a resistance member, and the position of the movable wall 425 is moved. Adjust. By using the movable wall 425 as the resistance member, the developer discharge amount can be more reliably adjusted.

  Also in the third embodiment, the fluidity may be determined in multiple stages as in the first to fourth modifications of the first embodiment, and the application time of the discharge suppression operation may be changed.

  In the first to third embodiments, the control unit 90 that controls the developing device 4 has been described as being provided separately from the developing device 4, but the present invention is not limited to this. The control unit 90 that controls the developing device 4 may be provided integrally with the developing device 4.

(Example)
Next, embodiments of the present invention will be described in more detail using examples. However, the present invention is not limited at all by this example.

  In this example, printing was continuously performed in the image forming apparatuses according to the first to third embodiments, and the amount of developer in the developer tank 40 and the image quality of printed matter (presence of developer supply unevenness) were evaluated.

  First, the implementation pattern in the present embodiment is as follows.

[Implementation pattern]
In Example 1, the image forming apparatus according to the first embodiment of the present invention shown in FIG. 3 was used.

  In Example 2, the image forming apparatus according to the second embodiment of the present invention shown in FIG. 8 was used.

  In Example 3, the image forming apparatus according to the third embodiment of the present invention shown in FIG. 10 was used.

  In the comparative example, an image forming apparatus that is different from the image forming apparatus used in Examples 1 to 3 only in that a resistance member for performing the developer discharge inhibiting operation is not provided.

  Subsequently, the implementation conditions are as follows.

[Conditions]
Process speed 300mm / s
Initial developer amount 700g
Initial toner concentration 7.0 wt%
Coverage 5% fixed Number of printed sheets per day 20,000 sheets After the completion of printing 20000 sheets on each implementation day, the operation of the developing device was stopped and the developer was left until the start time of the next day.

  Then, the evaluation result in a present Example is demonstrated.

[Evaluation results]
FIG. 11 is a diagram illustrating the relationship between the number of printed sheets and the amount of developer in the developing device. FIG. 12 is a diagram illustrating the relationship between the flowability of the developer and the amount of saturated developer in the developing device. The saturated developer amount is an amount of the developer that is most stable in the developing device at a certain time.

  In FIG. 11 and FIG. 12, the implementation result of the comparative example is shown as a broken line. On the other hand, the implementation results of Examples 1, 2, and 3 are shown as a solid line, a one-dot chain line, and a two-dot chain line, respectively.

  As shown in FIG. 11, in the comparative example, the amount of developer in the developing device is reached at the timing when printing is resumed after the number of printed sheets reaches 20,000, 40,000, 60,000 and the developer is left to stand. Was rapidly reduced to a developer amount at which developer supply unevenness occurred.

  In Examples 1 to 3, when the number of printed sheets reaches 20,000, 40,000, 60,000, the developer is left and the printing is resumed at the timing when printing is resumed, as in the comparative example. The dosage decreased. However, in Examples 1 to 3, unlike the comparative example, the developer amount started to increase before the developer amount decreased to the developer amount at which the developer supply unevenness occurred, and the developer supply unevenness occurred. Was avoided.

  As shown in FIG. 12, in the comparative example, the saturated developer amount decreases as the developer fluidity increases. Further, the degree of decrease in the saturated developer amount increases as the fluidity increases. Therefore, when the fluidity increases to some extent, the saturated developer amount decreases to an amount that causes uneven supply of the developer. In other words, the amount of developer in the developing device is stabilized in the amount in which supply unevenness occurs, and unevenness is likely to occur in the formed image in the image forming apparatus.

  On the other hand, in Examples 1 to 3, the saturated developer amount decreases as the developer fluidity increases. However, when the fluidity increases to some extent, the degree of decrease in the saturated developer amount decreases. Therefore, even if the fluidity increases to some extent, the saturated developer amount is not reduced to an amount that causes uneven supply of the developer, and an appropriate amount is ensured.

[Discussion]
From the above, as in the comparative example, when the resistance member for performing the developer discharge suppression operation is not provided, when the developer fluidity is increased, the developer is excessively discharged from the developing device. As a result, it has been found that uneven supply of the developer occurs. On the other hand, when the resistance member for performing the discharge prevention operation of the developer is provided as in Embodiments 1 to 3, the developer is excessive from the developing device even when the flowability of the developer is increased. It was found that the discharge can be suppressed, and the occurrence of uneven supply of the developer can be suppressed.

1Y, 1M, 1C, 1K photosensitive drum,
2Y, 2M, 2C, 2K charging unit,
3Y, 3M, 3C, 3K optical writing unit,
4Y, 4M, 4C, 4K developing device,
5Y, 5M, 5C, 5K photosensitive drum cleaning device,
6 Intermediate transfer belt,
7A Secondary transfer part,
7Y, 7M, 7C, 7K primary transfer part,
10Y, 10M, 10C, 10K image forming unit,
40 developer tank,
400 circuit,
401 stirring screw,
41 Supply section,
42 connections,
420 connection path,
421 reverse screw,
422 derivation route,
423 magnetic material,
424 electromagnet,
425 movable wall,
43 discharge section,
44 Developing roller,
90 Control unit.

Claims (11)

A developer tank containing a developer containing toner and a carrier that is a magnetic material;
A developing unit for developing the electrostatic latent image of the image carrier with a developer replenished in the developer tank and circulated in a circulation path;
A connection path that continues from the circulation path to a discharge unit that discharges a part of the developer in the developer tank;
A reverse conveyance unit that is provided in the connection path and conveys the developer in a direction opposite to a direction in which the developer in the circulation path is directed to the discharge unit;
A deriving path capable of deriving the developer to the discharge unit by bypassing the reverse conveying unit;
A resistance member capable of suppressing the derivation of the developer in the derivation path;
An acquisition unit for acquiring information on fluidity of the developer in the developer tank as fluidity information;
Based on the fluidity information, a control unit that controls the resistance member to adjust the developer discharge amount;
A developing device.   The developing device according to claim 1, wherein the acquisition unit acquires the amount of developer passing through the lead-out path per unit time as the fluidity information. The resistance member includes a magnetic body movably provided in the vicinity of the lead-out path,
The control unit suppresses the derivation of the developer by bringing the magnetic body closer to the derivation path, and permits the derivation of the developer by separating the magnetic body from the derivation path. The developing device according to claim 2. The resistance member includes an electromagnet provided in the vicinity of the lead-out path,
2. The control unit according to claim 1, wherein the controller suppresses the derivation of the developer by increasing the current supplied to the electromagnet, and permits the derivation of the developer by decreasing the current supplied to the electromagnet. 2. The developing device according to 2. The resistance member includes a movable wall movably provided in the lead-out path,
The control unit suppresses the derivation of the developer by moving the movable wall to a position that blocks a part of the derivation path, and the developer by retracting the movable wall to a position that does not block the derivation path. The developing device according to claim 1, wherein the derivation of the toner is allowed.   The controller determines from the fluidity information whether or not the developer in the developer tank has high fluidity, and if the fluidity is determined to be high, the resistance member suppresses the derivation of the developer. The developing device according to any one of claims 1 to 5.   The controller determines the degree of fluidity of the developer in the developer tank from the fluidity information at a predetermined timing, and suppresses the derivation of the developer by the resistance member according to the degree of fluidity. The developing device according to claim 1, wherein time is determined.   The acquisition unit acquires at least one of temperature, humidity, and a leaving time during which the developer is left as the circulation is stopped as fluidity information. The developing device according to item.   The developing device according to claim 1, wherein the acquisition unit acquires, as the fluidity information, an amount of developer that passes through the lead-out path by a magnetic center or an optical sensor. A weight detection sensor for detecting the weight of the developer discharged from the discharge unit;
The developing device according to claim 1, wherein the acquisition unit acquires, as the fluidity information, an increase rate of the developer weight detected by the weight detection sensor. A developer tank containing a developer containing toner and a carrier that is a magnetic material;
A developing unit for developing the electrostatic latent image of the image carrier with a developer replenished in the developer tank and circulated in a circulation path;
A connection path that continues from the circulation path to a discharge unit that discharges a part of the developer in the developer tank;
A reverse conveyance unit that is provided in the connection path and conveys the developer in a direction opposite to a direction in which the developer in the circulation path is directed to the discharge unit;
A deriving path capable of deriving the developer to the discharge unit by bypassing the reverse conveying unit;
A resistance member capable of suppressing the derivation of the developer in the derivation path;
An acquisition unit for acquiring information on fluidity of the developer in the developer tank as fluidity information;
Based on the fluidity information, a control unit that controls the resistance member to adjust the developer discharge amount;
An image forming unit;
An image forming apparatus.