JP2008040300A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a developing device capable of restraining the occurrence of density irregularity in a developed image while restraining the occurrence of control delay of developing operation. <P>SOLUTION: When toner is stuck to an electrostatic latent image formed on a photoreceptor 52 so as to develop the image in such a state that developer containing the toner and carrier is circularly conveyed inside by a developing unit 60, the concentration of the toner inside the developing unit 60 is detected time sequentially, and the variation width of the concentration of the toner is derived to decide whether or not the derived variation width is equal to or above predetermined width. When it is equal to or above the predetermined width, predetermined control to make the variation width under the predetermined width is performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device, and in particular, develops by attaching the toner to an electrostatic latent image formed on a predetermined image holding member in a state where a developer containing toner and a carrier is circulated and conveyed inside. The present invention relates to a developing device.

  Conventionally, as an example of a developing device that circulates and conveys a developer containing toner and a carrier and uses a part of the toner for development in the conveying process, one shown in FIG. 9 has been proposed.

  In this developing device, a developer supply path 502 and a developer stirring path 504 are formed in the axial direction of the developing sleeve 500, and the developer accommodated therein passes through passages 506 and 508 by conveying members 510 and 512 such as screws. Circulated and conveyed in the direction of arrow 516. Further, a part of the developer conveyed through the developer supply path 502 is held on the outer peripheral portion of the developing sleeve 500, and the toner is used for development at a portion facing the photoreceptor 520.

  The toner concentration of the developer, that is, the mixing ratio of the toner with respect to the carrier is detected by a toner concentration detection sensor 518 provided in the developer stirring path 504, and the toner is replenished from the replenishing port 514 in accordance with the decrease in the toner concentration.

  However, in this type of developing device, toner is replenished on the assumption that the toner density detected by the toner density detection sensor 518 represents the whole, and the toner is always replenished accurately to the position where the toner density is lowered. Was not.

  For this reason, as shown in FIG. 10 as an example, fluctuations (ripples) occur in the toner density distribution in the developer supply path 502 and the developer stirring path 504 with respect to the reference density T to be controlled, and development at a constant density. There was a problem that the agent could not be stably supplied to the developing sleeve 500 and density unevenness appeared on the reproduced image.

  In order to solve this problem, Patent Document 1 discloses that in a developing device that develops an electrostatic latent image with a developer composed of a mixture of toner and carrier, a toner storage unit and a toner supply port of the developing device are communicated. A toner replenishing path, a toner replenishing means for conveying the toner in the toner storage section to the toner replenishing path, and a position upstream of the toner replenishing port with respect to the flow of the developer conveyed in the developing device. A toner density detecting means for detecting the toner density of the developer, a time during which the developer is conveyed from the toner density detecting position of the toner density detecting means to the toner replenishing port, and a toner sent from the toner storage section Discloses a technology provided with a time difference from the time until the toner reaches the toner supply port and a control means for delaying the start of toner supply.

According to this developing device, as a result of replenishing the toner to the density-decreasing portion of the developer being circulated, the developer having a stable toner density is supplied to the developing sleeve, and an image having a constant density can be continuously obtained. Can do.
JP-A-2-162376

  However, in the technique disclosed in Patent Document 1, toner replenishment is started by the time when the developer is conveyed from the toner density detection position to the toner replenishment port, and the toner sent from the toner storage unit is removed from the toner replenishment port. Since there is always a delay from the detection timing of the toner density by the time difference from the time required to reach the toner, there is a problem that the development operation is likely to be delayed.

  In recent years, there has been an increasing demand for a high image forming speed for image forming apparatuses, and this problem is serious.

  The present invention has been made to solve the above-described problems, and provides a developing device capable of suppressing the occurrence of unevenness in the density of a developed image while suppressing the occurrence of a control delay in the developing operation. Objective.

  In order to achieve the above object, the developing device according to claim 1 is directed to an electrostatic latent image formed on a predetermined image holding member in a state where a developer including toner and a carrier is circulated and conveyed inside. A developing means for developing the toner by attaching the toner; a replenishing means for replenishing the toner into the developing means from a toner storage; a detecting means for detecting the density of the toner inside the developing means; and the detection A derivation unit for deriving a fluctuation range of the density of the toner detected in time series by the unit, and determining whether or not the variation range derived by the derivation unit is equal to or greater than a predetermined width. In some cases, control means for performing predetermined control for setting the fluctuation range to be less than the predetermined range is provided.

  According to the developing device of claim 1, the developer including toner and carrier is circulated and conveyed by the developing unit to the electrostatic latent image formed on the predetermined image holding member. Is attached and developed. In the present invention, the toner is supplied from the toner storage unit to the inside of the developing unit by the supply unit.

  Here, in the present invention, the toner density inside the developing means is detected by the detecting means, while the fluctuation range of the toner density detected in time series by the detecting means is derived by the deriving means. .

  In the present invention, the control means determines whether or not the fluctuation width derived by the derivation means is equal to or larger than a predetermined width. If the fluctuation width is equal to or larger than the predetermined width, the fluctuation width is less than the predetermined width. Predetermined control for performing the above is performed.

  As described above, according to the developing device of the first aspect, when the fluctuation range of the toner density in the developing unit is equal to or larger than the predetermined width, the fluctuation width is predetermined to be less than the predetermined width. Therefore, compared to the case where the control is always performed, it is possible to suppress the occurrence of density unevenness in the developed image while suppressing the occurrence of the control delay of the developing operation.

  According to the present invention, as in the invention described in claim 2, the control unit performs the toner from the toner storage unit to the inside of the developing unit within a predetermined period thereafter as the predetermined control. The replenishing means may be controlled so that the replenishment amount is smaller than when the fluctuation range is less than the predetermined width.

  According to a third aspect of the present invention, as in the third aspect of the present invention, as the predetermined control, the control unit performs control for temporarily interrupting the image forming process using the image carrier. It is good.

  According to a fourth aspect of the present invention, as in the fourth aspect of the present invention, the replenishing unit continuously increases the toner replenishment amount so that the toner density inside the developing unit becomes a predetermined reference density. The control means, as the predetermined control, changes the state of change in the toner replenishment amount within a predetermined period thereafter, and the fluctuation range is less than the predetermined range. It is good also as what controls the said replenishing means so that it may be in the reverse state to the case where it is.

  Further, according to the present invention, as in the invention described in claim 5, the replenishing unit continuously supplies the toner so that the toner concentration in the developing unit becomes a predetermined reference density. When the control means performs the predetermined replenishment time within the predetermined period thereafter as the predetermined control, the fluctuation range is less than the predetermined range. The supply means may be controlled to be shorter.

  Further, according to the present invention, as in the sixth aspect of the invention, the replenishing unit continuously supplies the toner so that the toner concentration in the developing unit becomes a predetermined reference density. And a period deriving unit for deriving a period of fluctuation of the toner density detected in time series by the detecting unit, and the control unit includes the predetermined control. As an alternative, the replenishing means may be controlled such that the toner replenishment state within a predetermined period thereafter is delayed by half the period derived by the period deriving means.

  Further, according to the present invention, as in the seventh aspect of the invention, the replenishing unit continuously increases the toner replenishment amount so that the toner density inside the developing unit becomes a predetermined reference density. And an integrated amount deriving unit for deriving an integrated amount of the toner replenishment amount by the replenishing unit within the variation period when the variation range of the toner density is equal to or greater than a predetermined width. And the control means, as the predetermined control, determines whether the toner replenishment state within a predetermined period thereafter is derived by the accumulated amount deriving means within a fluctuation cycle of the toner replenishment amount. The replenishing means may be controlled so that the amount is evenly distributed and replenished.

  As described above, according to the present invention, there is an excellent effect that it is possible to provide a developing device that can suppress the occurrence of unevenness in density of a developed image while suppressing the occurrence of a control delay in the developing operation. can get.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an outline of an image forming apparatus 10 according to the present embodiment. As shown in FIG. 1, the image forming apparatus 10 includes an engine unit 12, and a paper feeding unit 14 is provided below the engine unit 12.

  The paper feed unit 14 includes a paper tray 22 on which paper is stacked, and a paper feed roll 24 that feeds paper from the paper tray 22, and the paper delivered by the paper feed roll 24 is The paper passes through the paper feed path 30 via the transport rolls 26 and 28 and is transported to the transfer roll 74 described later.

  After the toner image is transferred onto the paper by the transfer roll 74 and fixed by the fixing roll 32A of the fixing unit 32, the toner image is provided on the upper portion of the engine unit 12 by the discharge roll 36 or the discharge roll 38 depending on the position of the switching claw 34. The discharged first discharge tray 16 or the second discharge tray 18 is discharged.

  Here, in the case of double-sided printing, after the printing of the front surface is completed in the order as described above, before the paper is completely discharged to the first discharge tray 16, the discharge roll 36 is reversed and the paper is reversed. Supplied to the line 40. The paper is then returned to the paper feed path 30 through the transport rolls 42, 44, 46, and 48, and the back side of the paper is printed. In the case of manual printing, by placing paper on the manual feed tray 20, the paper is transported from the manual feed roll 49 to the paper feed path 30 via the transport roll 48 and printed.

  Meanwhile, on the right side of FIG. 1 of the image forming apparatus 10, four developer cartridges 64 filled with a developer for each color (made of toner and magnetic carrier) are arranged. The developer cartridge 64 is connected to developing units 60Y, 60M, 60K, and 60C, which will be described later, arranged in order from the top of FIG. 1 through a developer supply path 65, and the developer in the developer cartridge 64 is stored in the developer cartridge 64. Supplied to developing devices 60Y, 60M, 60K, and 60C.

  Here, in each developer supply path 65, a spiral auger (not shown) that stirs the developer supplied from the corresponding developer cartridge 64 and conveys it to the corresponding developer is rotatably supported. In addition, motors 152 each having a rotation shaft mechanically connected to the shaft of the spiral auger are provided. Therefore, the developer can be supplied from the developer cartridge 64 to the corresponding developing device by rotating the rotating shaft of the motor 152.

  An exposure unit 62 is arranged on the left side of the developer cartridge 64 in FIG. 1, and four laser beams L (Y), L (M), and L (K) corresponding to the image signal are provided from the exposure unit 62. , L (C) is emitted toward the photoconductor 52 constituting the photoconductor unit 50 arranged on the left side of the exposure unit 62 in FIG. 1 to form a latent image on the photoconductor 52.

  The photoconductor unit 50 includes four photoconductor drums 52 (52Y, 52M, 52K, and 52C) arranged in the vertical direction. For example, yellow (52Y), magenta (52M), black (52K), and the like from the top. For cyan (52C).

  The exposure unit 62 includes Y (yellow), M (magenta), C (cyan), and K (black) laser beams L (Y), L (M), L (K), and L (C) (hereinafter, generic names). A light source unit that outputs a laser beam L), a modulation processing unit that modulates and scans the laser beam L, an fθ lens that corrects the scanning speed on the exposure surface, and a lens power in the scanning direction. And an optical system composed of a cylindrical lens for surface tilt correction and the like.

  In the exposure unit 62, the laser light L of each color emitted from the light source unit enters the modulation processing unit, is modulated according to the image information for each color, and is scanned by the polygon mirror 67 rotated by the polygon motor 63. (Main scanning). The laser light L of each color scanned by the polygon mirror 67 is reflected by the mirror group 69 in the arrangement direction of the photoconductor 52 corresponding to each color and is imaged on each photoconductor 52.

  The photoconductor unit 50 includes a charging roll 56 and a refresh roll 54 corresponding to each photoconductor 52, and is provided so as to rotate in contact with the photoconductor 52. In the charging roll 56, the photosensitive member 52 is uniformly charged, and toner flying from a magnet roll 80 provided in the developing unit 58 described later is attached to the surface of the photosensitive member 52. On the other hand, the refresh roll 54 discharges the photosensitive member 52 to remove residual toner adhering to the surface of the photosensitive member 52, thereby preventing ghosts and the like caused by the toner remaining on the surface of the photosensitive member 52.

  Here, the developing unit 58 is arranged on the lower right side in FIG. 1 of each photosensitive unit 50, and four developing units 60 corresponding to the respective photosensitive drums 52 (52Y, 52M, 52K, 52C). (60Y, 60M, 60K, 60C) are arranged in the vertical direction.

  The developing device 60 is in a trickle developing system (in order to prevent the charging performance of the developer from being lowered and to extend the interval for changing the developer, the developer is gradually replenished in the developing device, but becomes excessive ( (Developing system that contains a lot of deteriorated carriers) and develops while discharging the deteriorated developer) is adopted, and the deteriorated developer is collected in a collection container (not shown).

  On the other hand, an intermediate transfer unit 66 is arranged on the left side of the photoconductor unit 50 in FIG. 1, and three drum-shaped intermediate transfer bodies 68, 70, and 72 are provided. The two first intermediate transfer members 68 and 70 are arranged vertically in the vertical direction, and the upper first intermediate transfer member 68 is arranged on the two photoconductors 52Y and 52M arranged at the upper portion of the photoconductor 52. The lower first intermediate transfer member 70 rotates in contact with the two photoconductors 52K and 52C disposed in the lower portion. Further, the second intermediate transfer member 72 is rotated in contact with both the first intermediate transfer members 68 and 70, and the transfer roll 74 described above is rotated in contact with the second intermediate transfer member 72.

  Accordingly, the toner images are transferred from the photoconductors 52Y and 52M to the first intermediate transfer body 68, and the toner images are transferred from the photoconductors 52K and 52C to the first intermediate transfer body 70, respectively. The two color toner images transferred to the first intermediate transfer bodies 68 and 70 are transferred to the second intermediate transfer body 72 to form four colors, and the four color toner images are transferred onto the sheet by the transfer roll 74. Will be.

  A cleaning roll 76 and a cleaning brush 78 are disposed in the vicinity of the intermediate transfer members 68, 70, and 72, respectively, and the residual toner on the surface of the intermediate transfer members 68, 70, and 72 is scraped off.

  As shown in FIG. 2, the developing device unit 58 includes four developing devices 60, and each developing device 60 includes a box-shaped housing 110 and a lid 120 that closes the housing 110. Includes a magnet roll 80 (developer carrier) for supplying toner to the photoconductor 52, a spiral auger 112 (supply member) and a spiral auger for stirring the developer in the developing device 60 and supplying the developer to the magnet roll 80. 114 (stirring member) is rotatably supported. Note that an opening for supplying a developer to the inside of the developing device 60 is provided at a substantially central portion of the lid 120 of each developing device 60, and the developer supply path 65 and the developer supplying path 65 from the corresponding developer cartridge 64 are provided. The developer is supplied (supplemented) through the opening.

  Further, a toner concentration detection sensor 150 for detecting the toner concentration (the mixing ratio of the toner with respect to the carrier) inside the developing device 60 is provided near the lower surface of the portion where the spiral auger 114 is provided in each developing device 60. Is provided.

  Here, each developing device 60 can move between a position where the magnet roll 80 contacts the photoreceptor 52 and a position where the magnet roll 80 is retracted from the photoreceptor 52, and the magnet roll 80 moves to the photoreceptor 52 during image formation. It comes to contact. As a result, toner adheres to the photoconductor 52 corresponding to the latent image formed on the photoconductor 52. However, when image formation is not performed, the developing unit 58 is retracted from the photoconductor 52. It is supposed to be.

  A developing bias voltage in which a DC component is superimposed on an AC component is applied to the magnet roll 80, whereby toner is electrostatically attached only to the electrostatic latent image (image portion) of the photoconductor 52, thereby causing a toner image. Is formed.

  FIG. 3 is a block diagram of a control system for image formation in the engine unit 12.

  The main power management unit 200 is connected to a commercial power source (not shown), generates low voltage power and high voltage power, and supplies driving power to each unit via a power supply line.

  A user interface unit 204 is connected to the main controller 202, and an instruction relating to image formation or the like is given by a user's operation, and information on the time of image formation or the like is notified to the user.

  The main controller 202 is connected to a network line with an external host computer (not shown) so that image data is input.

  When the image data is input, the main controller 202 analyzes, for example, the print instruction information included in the image data and the image data, and converts them into a format suitable for the engine unit 12 (for example, bitmap data). Image data is sent to the image formation processing control unit 206.

  The image formation processing control unit 206 controls the optical scanning system control unit 208, the drive system control unit 210, the charger control unit 212, the developing device control unit 214, and the fixing device control unit 216 based on the input image data. Synchronous control is performed to execute image formation.

  Further, a toner density detection sensor 150 provided in each developing device 60 is connected to the main controller 202. Therefore, the main controller 202 can detect the toner density inside each developing device 60.

  Here, in the main controller 202 according to the present embodiment, as shown in FIG. 4 as an example, a value (hereinafter referred to as “sensor output value”) S output from the toner density detection sensor 150 is a predetermined target. The replenishment amount of toner from the developer cartridge 64 to the developing device 60 is derived by the following equation (1) so that the value corresponds to the toner density (hereinafter referred to as “target value”) M, and the replenishment is performed. The motor 152 is controlled via the image formation processing control unit 206 so that the amount is equal.

Toner replenishment amount = (α × P) + {β × (MS)} (1)
Here, P is the number of pixels of the image actually formed for each sheet of the image formation target, and α and β are predetermined according to the characteristics of the developer, the sheet of the image formation target, and the like. It is a coefficient.

  As an example, the developing device 60 according to the present embodiment circulates and conveys the developer in the same manner as the conventional developing device shown in FIG. 9 and uses a part of the toner for development in the conveying process. The sensor output value S changes continuously and periodically as shown in FIG. 7 as an example. Therefore, as a result of calculating the toner replenishment amount obtained by the above equation (1) as a continuous and periodic change, the toner replenishment amount from the developer cartridge 64 to the developing device 60 is also continuously and periodically. Controlled to change. The toner replenishment amount can be controlled by increasing or decreasing the rotation time or rotation speed of the motor 152 provided in the corresponding developer supply path 65, but the image forming apparatus according to the present embodiment. 10, the rotation speed of the motor 152 is constant at a predetermined rotation speed, and only the rotation time is increased or decreased.

  As described above, in the image forming apparatus 10 according to the present embodiment, the toner density in the developing device 60 is continuously and periodically fluctuated. An image formed as the fluctuation width increases. Concentration unevenness tends to occur on the top. For this reason, the image forming apparatus 10 is equipped with a toner density fluctuation suppressing function capable of suppressing the fluctuation range of the toner density.

  Here, in the image forming apparatus 10, the toner density fluctuation suppression function temporarily stops the toner supply amount suppression process and the image formation process for suppressing the fluctuation range by reducing the toner supply amount from the normal operation. Image formation stop processing that suppresses the fluctuation range, toner replenishment state reversal processing that suppresses the fluctuation range by changing the change state of the toner replenishment amount to a state opposite to that during normal operation, and continuous toner supply Continuous supply time shortening process that suppresses the fluctuation range by shortening the time compared with normal operation, and replenishment timing delay process that suppresses the fluctuation range by delaying the toner supply timing by half of the fluctuation period of the toner density. In the fluctuation cycle of the toner replenishment amount, the toner correction within the fluctuation cycle when the fluctuation range of the toner density is equal to or larger than the predetermined width. This is realized by selectively executing any one of six types of replenishment amount equalization processing that suppresses the fluctuation range by setting the integrated amount to be distributed and replenished. Yes.

  In the image forming apparatus 10, processing to be applied in the toner density fluctuation suppressing function is selected in advance via the user interface unit 204.

  Next, with reference to FIG. 5, a description will be given of the operation at the time of execution of the toner density fluctuation suppressing function of the image forming apparatus 10 according to the present embodiment. FIG. 5 is a flowchart showing the processing flow of the toner density fluctuation suppression processing program executed by the main controller 202 at this time, and the program is stored in advance in a nonvolatile memory (not shown) built in the main controller 202. Has been. Further, here, in order to avoid complications, the toner density fluctuation suppression processing program is executed assuming that it corresponds to only one developing device 60 (hereinafter referred to as “processing target developing device”) in the developing device unit 58. However, in practice, the same processing is executed for all the developing devices 60. Also, here, processing executed by the toner density fluctuation suppression function (here, toner replenishment amount suppression processing, image formation stop processing, toner replenishment state reversal processing, continuous replenishment time reduction processing, replenishment timing delay processing, and replenishment amount equalization) A case will be described in which any one of the conversion processes) is selected in advance by the user.

  In step 300 in the figure, the sensor output value S from the toner density detection sensor 150 provided in the developing device to be processed is acquired, and in the next step 302, the acquired sensor output value S is used as the maximum sensor output value. Is substituted into a variable Smax for storing and a variable Smin for storing a minimum value of the sensor output value.

  In the next step 304, the sensor output value S from the toner density detection sensor 150 provided in the developing device to be processed is acquired again. In the next step 306, the acquired sensor output value S is greater than the value of the variable Smax. If the determination is affirmative, the process proceeds to step 308, where the acquired sensor output value S is substituted into the variable Smax, and at the next step 310, the current time is substituted into the variable maxt. After that, the process proceeds to step 318 described later. At this time, as a time to be substituted for the variable maxt, a mode in which a time value by a timer built in the main controller 202 is applied can be exemplified.

  On the other hand, if a negative determination is made in step 306, the process proceeds to step 312 to determine whether or not the acquired sensor output value S is smaller than the value of the variable Smin. If the determination is affirmative, the process proceeds to step 314. Then, the obtained sensor output value S is substituted into the variable Smin, and at the next step 316, the time at that point is substituted into the variable mint, and then the process proceeds to step 318, while the determination at step 312 is negative. If YES in step 318, the flow advances to step 318 without executing the processing in steps 314 and 316. At this time, the time to be substituted for the variable mint can also be exemplified by a mode in which a time value by a timer built in the main controller 202 is applied.

  In step 318, a value obtained by subtracting the value of variable Smin from the value of variable Smax is substituted into variable H indicating the fluctuation range of the sensor output value. In next step 320, the value of variable H is set in advance. It is determined whether or not the threshold value is equal to or greater than a predetermined threshold value, and if a negative determination is made, the process returns to step 304 above, and the processing subsequent to step 304 is executed again. Transition.

  In Step 322, the value of the variable mint is subtracted from the value of the variable maxt, and the absolute value of the value obtained thereby is calculated, thereby deriving the fluctuation cycle of the toner density. Note that the fluctuation period derived here indicates a period of approximately one half of the actual period, but the fluctuation period used in the subsequent processing is approximately one half of the actual period. Since it is a period or a period that is four times the period, here, in consideration of convenience for subsequent processing, a period that is approximately one half of the actual period is derived.

  In the next step 324, a fluctuation suppressing process routine program for executing a predetermined process in order to reduce the fluctuation range of the sensor output value (toner density fluctuation range) is executed. Hereinafter, the fluctuation suppression processing routine program will be described with reference to FIG. FIG. 6 is a flowchart showing the flow of processing of the fluctuation suppression processing routine / program. The program is also stored in advance in a nonvolatile memory (not shown) built in the main controller 202.

  In step 400 of the figure, it is determined whether or not the process selected in advance by the user is the toner replenishment amount suppression process. If the determination is affirmative, the process proceeds to step 402 and the image forming process control unit 206 is performed. On the other hand, the amount of toner replenished from the developer cartridge 64 that supplies the developer to the processing target developing device into the processing target developing device is smaller than when the value of the variable H is less than the above threshold value (during normal operation). Thus, the toner replenishment amount suppression process is executed by controlling the rotation time of the motor 152, and then the fluctuation suppression process routine program is terminated. In the variation suppression processing routine program according to the present embodiment, as the toner supply amount suppression process, the toner supply amount is set to a half supply amount when the value of the variable H is less than the threshold value. However, the present invention is not limited to this, but is not limited to this, and a mode of applying a process of making the replenishment amount at other ratio when the ratio is less than the above threshold, or a process of stopping the toner replenishment (stopping the rotation of the motor 152) It can also be set as the form etc. which apply.

  On the other hand, if a negative determination is made in step 400, the process proceeds to step 404, where it is determined whether the process selected in advance by the user is an image formation stop process. The process proceeds to 406, and the image formation processing control unit 206 executes the image formation stop processing by causing the image formation processing using the corresponding photosensitive member 52 to be temporarily interrupted, and then performs this change. The suppression processing routine program ends.

  On the other hand, if a negative determination is made in step 404, the process proceeds to step 408, where it is determined whether the process selected in advance by the user is a toner replenishment state reversal process. In step 410, the rotation state of the motor 152 is set so that the state of change in the toner replenishment amount is opposite to that in the case where the value of the variable H is less than the threshold value. The toner replenishment state reversal process is executed by controlling this, and then the fluctuation suppression process routine program is terminated.

  On the other hand, if a negative determination is made in step 408, the process proceeds to step 412. If the process selected in advance by the user is a continuous replenishment time reduction process, the determination is affirmative. The process proceeds to step 414, and the continuous replenishment time is controlled by causing the image forming process control unit 206 to control the rotation state of the motor 152 so that the continuous toner replenishment time is shorter than when the value of the variable H is less than the threshold value. The time reduction process is executed, and then the fluctuation suppression process routine program is terminated. In the variation suppressing process routine program according to the present embodiment, as the continuous replenishment time shortening process, the toner continuous replenishment time is set to a half of the time when the value of the variable H is less than the threshold value. Although the process is applied, the present invention is not limited to this, and a form in which a process with a replenishment time of another ratio when it is less than the above-described threshold may be applied.

  On the other hand, if a negative determination is made in step 412, the process proceeds to step 416, where it is determined whether or not the process selected in advance by the user is a replenishment timing delay process. In step 418, the toner replenishment state is delayed with respect to the image formation processing control unit 206 by the time of the fluctuation cycle calculated by the processing in step 322 (specifically, approximately one half of the fluctuation cycle). The replenishment timing delay process is executed by controlling the rotation state of the motor 152, and then the fluctuation suppression process routine program is terminated.

  By executing the replenishment timing delay process, as shown in FIG. 7 as an example, the toner replenishment timing is delayed by about one half of the toner density fluctuation period, so that the fluctuation range of the toner density is converged. It will be.

  On the other hand, if a negative determination is made in step 416, the process selected in advance by the user is regarded as the replenishment amount equalizing process, and the process proceeds to step 420. As an example, as shown in FIG. After deriving the integrated amount of toner replenishment amount by the motor 152 within the fluctuation period when the fluctuation range of the density of the toner is equal to or greater than the predetermined width, the toner replenishment state for the image forming process control unit 206 is: A supply amount equalization process is executed by controlling the rotation state of the motor 152 so that the calculated integrated amount is evenly distributed and replenished within the fluctuation cycle of the toner replenishment amount. The fluctuation suppression processing routine program is terminated.

  When the fluctuation suppression processing routine program ends, the process proceeds to step 326 of the toner density fluctuation suppression processing program (see FIG. 5) and waits for the arrival of a predetermined timing as the timing for ending the toner density fluctuation suppression processing program. After that, in the next step 328, the operation state of the image forming process control unit 206 by the process executed in the fluctuation suppressing process routine program is changed to the normal operation (when the value of the variable H is less than the threshold value). Operation), and then the toner density fluctuation suppression processing program is terminated. In the toner density fluctuation suppression processing program according to the present embodiment, as the predetermined timing, a period that is four times the fluctuation period derived by the process of step 322 (approximately two cycles of the toner density fluctuation period). However, the present invention is not limited to this. For example, other timings such as the timing at which one print job ends or the timing at which image formation for a predetermined number of prints ends are applied. It goes without saying that it can be in a form to be performed.

  As described above in detail, in the present embodiment, when the fluctuation range of the toner density in the developing means (here, the developing device 60) is equal to or larger than the predetermined width, the fluctuation width is less than the predetermined width. Therefore, it is possible to suppress the occurrence of density unevenness in the developed image while suppressing the occurrence of a delay in the control of the developing operation as compared with the case where the control is always performed. it can.

  In the present embodiment, as the predetermined control, a toner storage unit (here, a developer cartridge) within a predetermined period thereafter (here, a period corresponding to approximately two cycles of the toner density fluctuation period). 64), the toner replenishing means (here, the motor 152) is controlled so that the amount of toner replenished from the developing means to the inside of the developing means is smaller than when the fluctuation range is less than the predetermined width. As a result, the variation in the density of the developed image can be easily suppressed.

  In the present embodiment, as the predetermined control, the image forming process using the image holding member (here, the photosensitive member 52) is temporarily interrupted. As a result, the variation range of the toner density can be reduced, and as a result, the density unevenness of the developed image can be easily suppressed.

  Further, in this embodiment, the replenishing unit changes the toner replenishment amount continuously and periodically so that the toner density inside the developing unit becomes a predetermined reference density. As the predetermined control, the replenishing means is controlled such that the state of change in the toner replenishment amount in a predetermined period thereafter is opposite to the case where the fluctuation range is less than the predetermined width. Therefore, in this case as well, the fluctuation range of the toner density can be easily reduced, and as a result, the density unevenness of the developed image can be easily suppressed.

  In the present embodiment, as the predetermined control, the replenishing means is set so that a continuous replenishment time of the toner within a predetermined period thereafter is shorter than when the fluctuation range is less than the predetermined range. In this case, the variation range of the toner density can be easily reduced, so that the density unevenness of the developed image can be easily suppressed.

  Further, in the present embodiment, as the predetermined control, the replenishing means is controlled so that the toner replenishment state within a predetermined period thereafter is delayed by a half of the toner density fluctuation period. Therefore, in this case as well, the fluctuation range of the toner density can be easily reduced, so that the density unevenness of the developed image can be easily suppressed.

  Further, in the present embodiment, the integrated amount of the toner replenishment amount by the replenishing means within the fluctuation period when the fluctuation range of the toner density is equal to or larger than a predetermined width is derived, and the predetermined control is as follows. Since the toner replenishment state within a predetermined period thereafter is controlled so that the integrated amount is evenly distributed and replenished within the fluctuation period of the toner replenishment amount. In this case as well, the fluctuation range of the toner density can be easily reduced, so that the density unevenness of the developed image can be easily suppressed.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various changes or improvements can be added to the above-described embodiment without departing from the gist of the invention, and embodiments to which such changes or improvements are added are also included in the technical scope of the present invention.

  The above embodiments do not limit the invention according to the claims (claims), and all the combinations of features described in the embodiments are essential for the solution of the invention. Is not limited. The above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. Even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, as long as an effect is obtained, a configuration from which these some constituent requirements are deleted can be extracted as an invention.

  For example, in the above-described embodiment, the case where processing for suppressing fluctuations in toner density is realized by software has been described. However, the present invention is not limited to this, and for example, the processing is realized by hardware. It can also be set as the form to do. In this case, it is expected that the processing speed is increased as compared with the above embodiment.

  In addition, the configuration (see FIGS. 1 to 3) of the image processing apparatus 10 described in the above embodiment is merely an example, and unnecessary portions are deleted or new portions are within the scope not departing from the gist of the present invention. Needless to say, you can add.

  Further, the processing flow (see FIGS. 5 and 6) of the toner density fluctuation suppression processing program and the fluctuation suppression processing routine program described in the above embodiment is an example, and does not depart from the gist of the present invention. It goes without saying that unnecessary steps can be deleted, new steps can be added, and the processing order can be changed within the range.

1 is a side view illustrating a configuration of an image forming apparatus according to an embodiment. It is an enlarged view showing a configuration of a developing unit according to the embodiment. 3 is a control block diagram illustrating a configuration of a control system for image formation in an engine unit of the image forming apparatus according to the embodiment. FIG. 6 is a graph for explaining control of a toner replenishment amount by the image forming apparatus according to the embodiment. 6 is a flowchart illustrating a processing flow of a toner density fluctuation suppression processing program according to the embodiment. It is a flowchart which shows the flow of a process of the fluctuation suppression process routine program which concerns on embodiment. It is a graph with which it uses for description of the replenishment timing delay process which concerns on embodiment. It is a graph with which it uses for description of the supply amount equalization process which concerns on embodiment. FIG. 10 is a diagram for explaining the problems of the conventional technology, and is a schematic plan view illustrating a configuration example of a conventional developing device. FIG. 10 is a diagram for explaining problems of the conventional technology and is a graph showing an example of a toner density distribution state in a conventional developing device.

Explanation of symbols

10 Image forming apparatus 60 Developer (Developing means)
64 Developer cartridge (toner storage)
150 Toner concentration detection sensor (detection means)
152 Motor (replenishment means)
202 Main controller (derivation means, control means, period derivation means, integrated quantity derivation means)

Claims (7)

Developing means for developing the toner by attaching the toner to an electrostatic latent image formed on a predetermined image holding member in a state in which a developer including toner and a carrier is circulated and conveyed inside;
Replenishing means for replenishing the toner from the toner storage unit into the developing means;
Detecting means for detecting the density of the toner inside the developing means;
Derivation means for deriving a fluctuation range of the density of the toner detected in time series by the detection means;
It is determined whether or not the fluctuation range derived by the deriving means is greater than or equal to a predetermined width. If the fluctuation range is greater than or equal to the predetermined width, a predetermined control for setting the fluctuation width to be less than the predetermined width is performed. Control means to perform;
A developing device comprising: As the predetermined control, the control means has a toner replenishment amount from the toner storage portion to the inside of the developing means within a predetermined period thereafter is smaller than when the fluctuation range is less than the predetermined width. The developing device according to claim 1, wherein the supply unit is controlled to be. The developing device according to claim 1, wherein the control unit performs control for temporarily interrupting an image forming process using the image carrier as the predetermined control. The replenishing means continuously and periodically changes the toner replenishment amount so that the density of the toner inside the developing means becomes a predetermined reference density.
The control means, as the predetermined control, is such that the change state of the toner replenishment amount in a predetermined period thereafter is opposite to the case where the fluctuation range is less than the predetermined range. The developing device according to claim 1, wherein the replenishing unit is controlled. The replenishing means continuously and periodically changes the toner replenishment amount so that the density of the toner inside the developing means becomes a predetermined reference density.
The control means controls the replenishment means as the predetermined control so that a continuous replenishment time of the toner within a predetermined period thereafter is shorter than when the fluctuation range is less than the predetermined width. The developing device according to claim 1. The replenishing means continuously and periodically changes the toner replenishment amount so that the density of the toner inside the developing means becomes a predetermined reference density.
A period deriving unit for deriving a period of fluctuation of the toner density detected in time series by the detecting unit;
The control means controls the replenishment means as the predetermined control so that the toner replenishment state within a predetermined period thereafter is delayed by half the period derived by the period deriving means. The developing device according to claim 1. The replenishing means continuously and periodically changes the toner replenishment amount so that the density of the toner inside the developing means becomes a predetermined reference density.
An integrated amount deriving unit for deriving an integrated amount of the toner replenishing amount by the replenishing unit within a variation period when the variation range of the toner density is equal to or greater than a predetermined width;
As the predetermined control, the control means determines whether the toner replenishment state within a predetermined period thereafter is the accumulated amount derived by the accumulated amount deriving means within the fluctuation period of the toner replenishment amount. The developing device according to claim 1, wherein the replenishing unit is controlled to be in a state of being evenly distributed and replenished.

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