JP5659211B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In a two-component electrophotographic image forming apparatus (Multi-Functional Peripheral), a visible image obtained by developing a latent image formed on a photoconductor as an image carrier with toner is used as a medium (paper or resin sheet). Transcript. In general, a developing device that uses a two-component developer of toner and carrier replenishes toner consumed by a developing operation. The developer used in such an image forming apparatus is circulated during the image forming operation so as not to be unevenly distributed in the developing apparatus. When the toner is used and consumed for development and the toner sensor provided in the developing device detects that the toner in the developing device has decreased, the toner is supplied from the toner cartridge to the developing device.

JP 2004-347931 A

  By the way, in response to a demand for high quality printing, a mode is provided in which the image forming speed (printing speed) is changed depending on the thickness (or basis weight) of the medium. As a result, as the printing speed changes, the developer in the developing device is changed. Circulation speed may be changed. On the other hand, the toner supply speed from the toner cartridge is not changed.

  For this reason, for example, when printing is performed at a lower printing speed for thick paper printing, the toner is supplied at the same speed as when the developer circulation speed is high, even though the developer circulation speed is slow. As a result, the toner concentration in the developer is not uniform, and a so-called replenishment unevenness image may be generated.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an image forming apparatus capable of maintaining a uniform toner concentration in a developer in a developing device.

According to an embodiment for solving the above problems, a developing device using a developer composed of toner and a carrier, a density sensor for detecting the toner density in the developing device, and a pixel per page unit of an image to be printed Each time a one-page image is printed, referring to the density measurement value of the density sensor and the count of the pixel counter, either the density measurement value by the density sensor or the pixel count by the pixel counter And, if the pixel count by the pixel counter is equal to or smaller than a predetermined threshold value, the toner supply is performed with the supplied toner amount obtained from the density measurement value of the density sensor. When the pixel count by the first control means and the pixel counter exceeds a predetermined threshold, the pixel count One of said setting means for setting the toner supply number to the developing device, the plurality of times replenishing out to set the toner supplying times in a plurality of times by said setting means in accordance with the supplied toner amount and image printing speed obtained from In addition to referring to the density value of the density sensor in order to perform replenishment from the replenishing device every time a one-page image is printed, the measurement value of the density sensor is referred to, and There is provided an image forming apparatus comprising: a second control unit that performs toner replenishment after confirming that a measured value of toner density in the developing device is a predetermined replenishment level that is not a replenishment prohibition level.

FIG. 4 is a diagram illustrating a configuration related to toner replenishment and a control system of the image forming apparatus according to the present embodiment. FIG. 10 is a sequence diagram illustrating a toner replenishment control operation in a conventional image forming apparatus. FIG. 3 is a cross-sectional view illustrating an arrangement inside a case of the developing device of the image forming apparatus according to the exemplary embodiment. FIG. 4 is a diagram illustrating a concept of toner supply control in the image forming apparatus according to the present embodiment. FIG. 4 is a diagram illustrating a concept of toner supply control based on pixel count in the image forming apparatus according to the present embodiment. FIG. 6 is a sequence diagram illustrating a toner supply control operation in the image forming apparatus according to the present embodiment. FIG. 5 is a diagram illustrating the contents of a toner supply sequence pattern in the image forming apparatus according to the present embodiment. FIG. 6 is a diagram illustrating toner supply start timing information in the image forming apparatus according to the present embodiment. FIG. 6 is a flowchart illustrating a toner supply processing procedure in the image forming apparatus according to the present exemplary embodiment. FIG. 6 is a flowchart illustrating a toner supply processing procedure in the image forming apparatus according to the present exemplary embodiment. FIG. 6 is a flowchart illustrating a toner supply processing procedure in the image forming apparatus according to the present exemplary embodiment. It is a flowchart which shows the process sequence which reduces the transition to the abnormal state in the image forming apparatus of this Embodiment. 6 is a diagram for explaining a method of changing a value of a pixel count information toner supply time conversion table in the image forming apparatus according to the present embodiment. FIG.

  FIG. 1 is a diagram showing a configuration of a part and a control system related to toner replenishment in the image forming apparatus according to the present embodiment.

  The image forming apparatus 1 includes a control unit 10, a photosensitive member 102, a charging device 103, an exposure device 104, a developing device 105, a cleaner device 108, a primary transfer device 109, a transfer belt device 110, a high voltage power supply 111, and a toner replenishing device 112. I have. The developing device 105 is provided with a stirring mixer 213, a developing sleeve 214, and a toner concentration sensor 220.

  The photoconductor 102 rotates in the sub-scanning direction that is the circumferential direction of the photoconductor 102. A charging device 103 is disposed in the vicinity of the periphery of the photoconductor 102. The charging device 103 uniformly charges the surface of the photoconductor 102 by the charging high voltage applied from the high voltage power source 111.

  The exposure apparatus 104 emits light / extinguishes according to the image signal while scanning the semiconductor laser in the exposure apparatus 104. Laser light emitted from the semiconductor laser becomes light that is scanned in the main scanning direction, which is the rotational axis direction of the photosensitive member 102, by a deflector such as a polygon mirror. The photosensitive member 102 is irradiated with laser light by an optical system such as a lens. When the charged photoconductor 102 is irradiated with laser light, the potential of the irradiated portion is lowered and an electrostatic latent image is formed.

  The developing device 105 forms a developer layer on the developing sleeve, thereby supplying toner to a position where the photosensitive member and the developing sleeve face each other, that is, a developing position. The toner replenishing device 112 is detachably provided and replenishes the developing device 105 with toner.

  A primary transfer device 109 is provided at the transfer position of the photosensitive member 102 and forms a toner image on the transfer belt of the transfer belt device 110. The medium supplied from the paper tray is transported to a transfer position, and a toner image is transferred by a secondary transfer device (not shown) and a transfer belt. The medium onto which the toner image has been transferred is conveyed to a fixing device (not shown), and the toner image is fixed by heating and pressing. Then, the medium on which the toner image is fixed is discharged.

Further, after the transfer of the toner image to the medium is completed, the residual toner on the photoconductor 102 is removed by the cleaner device 108. The photosensitive member 102 returns to the initial state and enters a standby state for the next image formation.
By repeating the above process operation, the image forming operation is continuously performed.

  The developing device 105 is provided with a stirring mixer 213 and a developing sleeve 214. The agitating mixer 213 agitates the toner replenished from the toner replenishing device 112 and supplies the toner to the photoconductor 102 via the developing sleeve 214. A developing high voltage is applied to the developing sleeve 214, and the electrostatic latent image on the photosensitive member 102 is developed by a reversal phenomenon.

The developing sleeve 214 and the stirring mixer 213 are mechanically connected (mechanical tie) and are driven together by a developing motor (not shown). On the other hand, the photoconductor 102 is driven by another motor (not shown). These motors are driven based on a drive command from the control unit 10.

  Further, the developing device 105 is provided with a toner concentration sensor 220 that detects the toner concentration in the developing container. The toner density sensor 220 outputs a measurement signal (density sensor detection voltage) corresponding to the remaining amount of toner in the developing container. Therefore, the toner replenishing device 112 is controlled based on the output from the toner density sensor 220 to replenish the toner in the developing container. For example, toner is replenished from the toner replenishing device 112 into the developing container for a time corresponding to the measurement signal of the toner density sensor 220 representing the remaining amount of toner by the toner replenishment control signal. This detailed replenishment operation will be described later.

  The control system of the image forming apparatus 1 includes a control unit 10, a control panel 11, a memory unit 12, an image information management unit 13, and a size information management unit 14.

  The control panel 11 is an instruction input unit for instructing the operation of the image forming apparatus 1 such as the start of image formation or the start of reading of image information of a document by a scanning operation. The memory unit 12 stores a table and information for controlling the toner supply operation. The image information management unit 13 stores the pixel information of the document read by the scanning operation. The size information management unit 14 stores information related to the size (vertical x horizontal x thickness, etc.) of the medium. The control unit 10 controls the overall operation of the image forming apparatus.

  The contents of information stored in the memory unit 12, the image information management unit 13, and the size information management unit 14 will be described in detail later.

  Next, a conventional toner supply control operation will be described.

  FIG. 2 is a sequence diagram illustrating a toner replenishment control operation in the conventional image forming apparatus. The horizontal axis in FIG. 2 represents the passage of time, and the timing for giving a characteristic operation is shown as t0 to t4. The vertical axis indicates the contents of the operation classified into the types of operations S1 to S6.

  At timing t0, for example, when the user instructs the start of the printing operation from the control panel 11, the printing sequence start operation S1 is activated. Subsequently, the developing motor operation S2 is started, and the developing sleeve 214 and the stirring mixer 213 start to rotate. At this time, the photosensitive member 102 also starts rotating.

  At timing t1, an image writing operation S3 for writing image data of the first page of the document on the photosensitive member 102 is started. Note that the toner replenishment motor operation S6 is activated at the timing t1, but since the contents thereof will be described later, the description thereof is omitted here. Subsequent to the end of the image writing operation S3, a page pixel count information acquisition operation S5 is activated to count the number of pixels included in the image data of the first page. This count is stored in “print page pixel count information” of the image information management unit 13.

  At timing t2, an image writing operation S3 for writing the image data of the second page of the document on the photosensitive member 102 is started. Then, at this timing t2, the toner concentration sensor information acquisition operation S4 is activated, and the detection voltage of the toner concentration sensor 220 is acquired.

  Note that in order to acquire a stable detection voltage of the toner density sensor 220, it is prohibited to capture the detection signal of the sensor for a certain period of time after the development motor is started. The predetermined time for prohibition is defined in “toner density sensor detection prohibition time” stored in the memory unit 12.

  Next, the replenishment time is acquired from “print page pixel count information”. When acquiring the replenishment time, the replenishment time is acquired with reference to the “pixel count information toner replenishment time conversion table” stored in the memory unit 12. Further, the replenishment time is acquired from the detection voltage of the toner density sensor 220. When acquiring the replenishment time, the replenishment time is acquired with reference to the “toner density sensor information toner replenishment time conversion table” stored in the memory unit 12. Then, the replenishment time acquired from each information is compared, and the toner is replenished with the longer replenishment time. This replenishment operation is executed in the toner replenishment motor operation S6.

  Thereafter, the above-described operation is repeatedly executed until one page before the last page.

  At timing t3, an image writing operation S3 for writing the image data of the last page of the document on the photosensitive member 102 is started. Then, at this timing t3, the toner concentration sensor information acquisition operation S4 is activated, and the detection voltage of the toner concentration sensor 220 is acquired. At this time, at the timing t3, the toner concentration sensor information acquisition operation S4 is activated, and the detection voltage of the toner concentration sensor 220 is acquired. Then, as described above, the replenishment time acquired from each information is compared, and the toner is replenished with the longer replenishment time. This replenishment operation is executed in the toner replenishment motor operation S6.

  Subsequent to the end of the image writing operation S3, a page pixel count information acquisition operation S5 is activated to count the number of pixels included in the image data of the last page. The replenishment time calculated from the count is stored as data A in the memory unit.

  At timing t4, an end sequence is input. This end sequence is a signal input when the image forming operation of the last page is finished and the medium is conveyed to a predetermined position. At timing t4, a toner concentration sensor information acquisition operation S4 is activated, and the detection voltage of the toner concentration sensor 220 is acquired. The replenishment time calculated from the detected voltage is stored as data B in the memory unit. Then, the developing motor operation S2 and the printing sequence start operation S1 are completed.

  Data A and data B stored by the above-described printing operation are referred to in the next print job. That is, at the timing t1 of the next print job, the replenishment operation is started with the longer replenishment time by comparing the data A and data B stored at the end of the previous job. This operation is indicated by toner supply motor operation S6 at timing t1 in FIG. Note that when the detection voltage of the toner density sensor 220 corresponding to the data B is the upper limit value of toner and is at a level that does not require replenishment (replenishment prohibition level), the toner replenishment motor operation S6 at this timing t1 is not executed.

  Next, the problem in the conventional toner replenishing operation and the basic concept of the toner replenishing operation in the present embodiment will be described.

  FIG. 3 is a cross-sectional view showing the arrangement inside the case of the developing device of the image forming apparatus of the present embodiment.

  Two stirring mixers 213 are provided in the case of the developing device with the partition plate 70 interposed therebetween. A toner replenishing port 52 is provided in the upper part of the case, and the toner conveyed from the toner replenishing device 112 is dropped and supplied into the case through the toner replenishing port 52. A developing sleeve 214 is provided at a position separated by a distance L upstream from the position of the toner supply port 52.

  The developing sleeve 214 is rotatably provided in the case. The developing sleeve 214 supplies toner to the electrostatic latent image formed on the photoconductor 102 to form a toner image. The agitating mixer 213 constitutes an auger. By rotating the agitating mixer 213, the developer (toner and carrier) in the case is moved in the direction of the arrow in the figure while being mixed and circulates in the case. That is, the toner supplied via the toner supply port 52 circulates in the case and is supplied to the developing sleeve 214.

  Accordingly, there is a temporal difference between the timing at which the developing sleeve 214 supplies the developer and the timing at which the developer region where the toner has been consumed reaches the toner supply port 52 by the stirring mixer 213. In the conventional toner replenishing method, this time difference is not taken into consideration. In the present application, a toner replenishing method in consideration of this time difference is presented.

  FIG. 4 is a view for explaining the concept of toner replenishment control in the image forming apparatus according to the present embodiment.

  The amount of toner supplied to and consumed by the developing sleeve 214 by the developing sleeve 214 depends on the electrostatic latent image formed on the photosensitive member 102. That is, the pixel count information corresponds to the amount of toner consumed. Therefore, as shown in FIG. 4, a threshold value Cth is set in the pixel count, and when the pixel count value is larger than the threshold value Cth, toner supply time is obtained based on the pixel count and toner supply is executed. This supply is referred to as “pixel count supply”. On the other hand, when the pixel count value is equal to or less than the threshold value Cth, the toner replenishment time is obtained based on the detection voltage of the toner density sensor, and the toner replenishment is executed.

  FIG. 5 is a diagram for explaining the concept of toner replenishment control based on pixel count in the image forming apparatus according to the present embodiment. The horizontal axis represents the position in the case, and the vertical axis represents the toner density at each position.

  A curve A shown in FIG. 5 represents the distribution shape of the toner density in the case. This distributed shape is a concave shape in which the toner density in the region consumed by the developing sleeve 214 is lowered. This shape is moved as it is by the stirring mixer 213. Then, toner is supplied at the toner supply port 52 position.

  A curve B represents the distribution shape of the toner density after the toner is replenished by the conventional replenishing method. In this shape, a part of the concave shape of the toner is raised, and the toner density has an uneven distribution shape.

  A curve C represents the distribution shape of the toner density after the toner is replenished by the replenishment method of the present embodiment. By supplying the toner divided into a plurality of times, the toner density has a flat distribution shape.

  FIG. 6 is a sequence diagram illustrating a toner supply control operation in the image forming apparatus according to the present embodiment. The horizontal axis in FIG. 6 represents the passage of time, and the timing for giving a characteristic operation is shown as t0 to t4. The vertical axis indicates the contents of the operation classified into the types of operations S1 to S6.

  In the sequence diagram shown in FIG. 6, when printing three pages, toner supply based on the pixel count information is selected for the first and third pages, and the second page is used as the toner density sensor output. This represents a case where toner replenishment based is selected.

  At timing t0, for example, when the user instructs the start of the printing operation from the control panel 11, the printing sequence start operation S1 is activated. Subsequently, the developing motor operation S2 is started, and the developing sleeve 214 and the stirring mixer 213 start to rotate. At this time, the photosensitive member 102 also starts rotating.

  At timing t1, an image writing operation S3 for writing image data of the first page of the document on the photosensitive member 102 is started. Note that the toner replenishment motor operation S6 is activated at the timing t1, but since the contents thereof will be described later, the description thereof is omitted here. Subsequent to the end of the image writing operation S3, a page pixel count information acquisition operation S5 is activated to count the number of pixels included in the image data of the first page.

  This pixel count is a value larger than the threshold value Cth. Accordingly, pixel count replenishment is selected, and then a replenishment pattern is determined.

  FIG. 7 is a diagram showing the contents of a toner supply sequence pattern in the image forming apparatus of the present embodiment.

  The toner replenishment pattern is divided into speed 1 (low speed) and speed 2 (high speed) according to the printing speed. When the medium is thick, the printing speed of the image forming apparatus is selected as speed 1 (low speed). When the medium is thin, the printing speed of the image forming apparatus is selected as speed 2 (high speed). . Here, the printing speed and the developer circulation speed increase or decrease correspondingly. Therefore, this speed can be grasped as the developer circulation speed.

  When the speed is 1 (low speed), the replenishment pattern varies depending on the pixel count x. When the pixel count x ≦ n, the calculated amount of toner is replenished in one replenishment operation. When n <pixel count x ≦ m, the calculated amount of toner supply is divided and executed twice. When m <pixel count x, the toner supply of the calculated amount is divided into three times and executed.

  In the case of speed 2 (high speed), the replenishment pattern varies depending on the pixel count x. When the pixel count x ≦ m, the calculated amount of toner is replenished in one replenishment operation. When m <pixel count x, the replenishment of the calculated amount of toner is performed twice.

  Here, the page pixel count information acquisition operation S5 is determined to execute the calculated amount of toner supply divided into three times. That is, it is determined to execute the first supply (11), the second supply (12), and the third supply (13).

  Next, the process waits until a (1) seconds elapse from the start of the image writing operation S3. Here, a (1) second is determined from the distance L from the left end position (development position) of the developing sleeve 214 shown in FIG. 3 to the toner supply port 52 and the developer circulation speed. That is, a (1) seconds corresponds to the time for the developer region where the toner is consumed by the developing sleeve 214 to reach the toner supply port 52.

  This time is stored in the memory unit 12 as toner supply start timing information shown in FIG. In FIG. 8, since the moving time from the developing position to the toner supply port 52 is defined corresponding to the printing speed (developer circulation speed), the moving time can be easily grasped by using this information. it can.

  Therefore, the toner density sensor information acquisition operation S4 is started when a (1) seconds have elapsed, and the detection voltage of the toner density sensor 220 is acquired. If it is not prohibited to replenish the toner from the detected voltage, the toner replenishment motor operation S6 is executed, and the first replenishment operation (11) divided into three is performed.

  Note that in order to acquire a stable detection voltage of the toner density sensor 220, it is prohibited to capture the detection signal of the sensor for a certain period of time after the development motor is started. The predetermined time for prohibition is defined in “toner density sensor detection prohibition time” stored in the memory unit 12.

  The second supply (12) of the three-part supply operation is executed after elapse of b (11) seconds, and the third supply (13) is executed after elapse of b (12) seconds. These times are obtained on the basis of the medium size (corresponding to the width of the concave portion) stored in the size information management unit 14 and the developer circulation speed so as to provide uniform replenishment as shown by the curve C in FIG. It is done.

  At timing t2, an image writing operation S3 for writing the image data of the second page of the document on the photosensitive member 102 is started. Subsequent to the end of the image writing operation S3, a page pixel count information acquisition operation S5 is activated to count the number of pixels included in the image data of the first page. This pixel count is a value equal to or less than the threshold value Cth. Accordingly, pixel count replenishment is not selected, and the replenishment amount is determined based on the measured value of the toner density sensor 220.

  Next, it waits until a (2) seconds elapse from the start of the image writing operation S3 of the second page. Here, a (2) seconds is determined from the distance L from the left end position (development position) of the developing sleeve 214 shown in FIG. 3 to the toner supply port 52 and the developer circulation speed. That is, a (2) seconds corresponds to the time for the developer region where the toner is consumed by the developing sleeve 214 to reach the toner supply port 52.

  This time is stored in the memory unit 12 as toner supply start timing information shown in FIG. In FIG. 8, since the moving time from the developing position to the toner supply port 52 is defined corresponding to the printing speed (developer circulation speed), the time can be easily grasped by using this information. .

  Therefore, the toner density sensor information acquisition operation S4 is started when a (2) seconds have elapsed, and the detection voltage of the toner density sensor 220 is acquired. If it is not prohibited to replenish toner from this detected voltage, toner replenishment motor operation S6 is executed and replenishment (2) by the toner density sensor is performed. When acquiring the replenishment time, the replenishment time is acquired with reference to the “toner density sensor information toner replenishment time conversion table” stored in the memory unit 12.

  At timing t3, an image writing operation S3 for writing image data of the last page (third page) of the document on the photosensitive member 102 is started. Subsequent to the end of the image writing operation S3, a page pixel count information acquisition operation S5 is activated to count the number of pixels included in the image data of the third page.

  This pixel count is a value larger than the threshold value Cth. Accordingly, pixel count replenishment is selected, and then a replenishment pattern is determined. Since this operation is the same as the operation on the first page, detailed description thereof is omitted. That is, the page pixel count information acquisition operation S5 is determined to execute the calculated amount of toner supply divided into three times. For example, it is determined to execute the first supply (11), the second supply (12), and the third supply (13).

  Then, the toner concentration sensor information acquisition operation S4 is started when a (3) seconds have elapsed from the start of the image writing operation S3, and the detection voltage of the toner concentration sensor 220 is acquired. If it is not prohibited to replenish the toner from the detected voltage, the toner replenishment motor operation S6 is executed and the first replenishment operation (31) divided into three is performed.

  Subsequently, the second supply (32) of the supply operation divided into three is executed after b (31) seconds have elapsed. The third replenishment (33) is planned to be executed after elapse of b (32) seconds.

  At timing t4, an end sequence is input. At timing t4, a toner concentration sensor information acquisition operation S4 is activated, and the detection voltage of the toner concentration sensor 220 is acquired. The replenishment time calculated from the detected voltage is stored as data B in the memory unit. Then, the developing motor operation S2 and the printing sequence start operation S1 are completed.

  Note that the third supply (33) scheduled to be executed after the end sequence input is not performed. The data B stored by the above printing operation is referred to in the next print job. That is, at the timing t1 of the next print job, the replenishment operation is started with the replenishment time of the data B stored at the end of the previous job. This operation is indicated by toner supply motor operation S6 at timing t1 in FIG.

  9, 10, and 11 are flowcharts showing a toner replenishment processing procedure in the image forming apparatus of the present embodiment. The operation of the processing shown in this flowchart is performed by the control unit 10 in an integrated manner. Note that the contents described in FIGS. 1 to 8 and the contents described with reference to these drawings are the same as those in the present embodiment even though the contents are not shown in the flowchart and are not mentioned. include.

  When the user instructs reading of a document from the control panel 11 and the start of the print sequence, the control unit 10 starts the print sequence. In Act 01 of FIG. 9, the control unit 10 starts the operation of the developing motor. In Act 02, the process waits until a predetermined time (t1) elapses from the start of the printing sequence. When the predetermined time (t1) has elapsed (YES in Act 02), in Act 03, the control unit 10 starts an operation of writing the image data of the first page on the photoconductor 102.

  In Act 04, the control unit 10 grasps the printing speed from the thickness of the medium. Then, the toner supply start time a (1) corresponding to the printing speed is extracted with reference to the toner supply start timing information in the memory unit 12. Then, the toner supply start time a (1) is set.

  In Act 05, it is checked whether or not a toner supply request is generated from the previous job. When a toner supply request is generated from the previous job (YES in Act 05), the requested toner supply time is acquired in Act 06, and execution of toner supply is instructed. When the toner supply request from the previous job is not generated (NO in Act 05) and after the instruction of Act 06 is executed, the process waits until the image writing operation for the first page is completed in Act 07.

  When the image writing operation for the first page is completed (YES in Act 07), the pixel count information of the print page is acquired in Act 11 of FIG. 10 ([Page Pixel Count Information Acquisition Operation S5]). In Act 12, it is checked whether or not the condition for executing the pixel count supply is met. That is, it is checked whether the pixel count is greater than the threshold value Cth.

  When the conditions for executing pixel count replenishment are met (YES in Act 12), the pixel count is converted into toner replenishment time in Act 13. In Act 14, the process waits until the developer reaches the toner supply port 52 from the development position. That is, it waits until the toner replenishment start time a (i) has elapsed since the start of image writing. When the developer reaches a position where toner replenishment starts (position of toner replenishing port 52) (YES in Act 14), toner density sensor information is acquired in Act 15 ([Toner density sensor information acquisition operation S4]). ).

  In Act 16, it is determined from the toner density sensor information whether the toner is insufficient and is at the forced toner supply level. When the toner is at the forced toner replenishment level (YES in Act 16), the operation proceeds to the forced toner replenishment operation. After shifting to the forced toner supply operation, a special process is executed without returning to the toner supply operation. Therefore, this process ends.

  When it is not at the forced toner replenishment level (NO in Act 16), it is determined in Act 17 whether or not the toner replenishment is prohibited because toner is excessive from the toner density sensor information. If the toner replenishment level is prohibited (YES in Act 17), the process of Act 20 is executed.

  When the toner replenishment level is not prohibited (NO in Act 17), in Act 18, a toner replenishment sequence pattern is acquired. That is, based on the pixel count and the toner replenishment sequence pattern information, a replenishment method such as whether to replenish the replenishment and the operation timing at the time of the replenishment is determined. In Act 19, execution of the toner supply operation is started according to the determined supply method.

  On the other hand, if NO in Act 12, that is, if the pixel count is less than or equal to the threshold Cth and does not match the conditions for executing pixel count replenishment, in Act 25 the developer moves from the development position to the toner replenishment port 52 position. Wait until it reaches. That is, it waits until the toner replenishment start time a (i) elapses from the start of image writing. When the developer reaches a position (toner supply port position) at which toner supply starts (YES in Act 25), toner concentration sensor information is acquired in Act 26 ([Toner concentration sensor information acquisition operation S4]).

  In Act 27, it is determined from the toner density sensor information whether the toner is insufficient and is at the forced toner supply level. When the forced toner supply level is reached (YES in Act 27), the process proceeds to a forced toner supply operation. After shifting to the forced toner supply operation, a special process is executed without returning to the toner supply operation. Therefore, this process ends.

  When it is not at the forced toner replenishment level (NO in Act 27), the detection voltage of the toner density sensor 220 is acquired in Act 28, and the replenishment time is calculated from this detection voltage. Then, the process of Act 19 is executed.

  In Act 20, it is checked whether or not the processing of the last page has been completed. When the process execution of the last page has not ended (NO in Act 20), the process returns to Act 11 to execute a new page process. When the processing of the last page has been completed (YES in Act 20), the processing of Act 31 in FIG. 11 is executed.

  In Act 31, the process waits until the end sequence starts. When the end sequence is started (YES in Act 31), the toner supply operation is stopped in Act 32. In Act 33, the detection voltage of the toner density sensor 220 is acquired. In Act 34, the toner replenishment time is calculated from the detected voltage, and the fact that there is a toner replenishment request is stored.

  In Act 35, it is determined from the toner density sensor information whether the toner is insufficient and is at the forced toner supply level. When it is not at the forced toner supply level (NO at Act 35), the toner supply process is terminated. When the forced toner replenishment level is reached (YES in Act 35), the operation proceeds to the forced toner replenishment operation. After shifting to the forced toner supply operation, a special process is executed without returning to the toner supply operation. Therefore, this process ends.

  As shown in the above-described embodiment, after the transition to the forced toner supply operation, the toner supply operation is stopped. The toner supply operation is also stopped when the toner supply prohibition level is reached. Therefore, it is necessary to control the toner replenishment operation so as not to transition to such a performance degradation state.

  FIG. 12 is a flowchart showing a processing procedure for reducing the transition to the performance degradation state in the image forming apparatus of the present embodiment.

  When the toner supply based on the pixel count is executed in Act 41, it is checked in Act 42 whether the toner supply based on the pixel count is continuously executed. When the previous toner replenishment is toner replenishment based on the toner density sensor information, and toner replenishment based on the pixel count is not continuously performed (NO in Act 42), this process ends.

  When the toner supply based on the pixel count is continuously performed (YES in Act 42), in Act 43, it is determined from the toner density sensor information whether the toner is insufficient and is at the forced toner supply level. When it is at the forced toner replenishment level (YES in Act 43), it is checked in Act 45 whether the toner in the toner replenishing device 112 is empty.

  When the toner in the toner replenishing device 112 is empty (YES in Act 45), the forced toner replenishment level is caused by the toner replenishing device 112, and thus this processing is terminated. When the toner in the toner replenishing device 112 is not empty (NO in Act 45), the processing in Act 46 is executed.

  If the forced toner replenishment level is not reached (NO in Act 43), it is determined in Act 44 whether or not the toner density sensor information indicates that the toner is excessive and toner replenishment is prohibited. If the toner replenishment level is not prohibited (NO in Act 44), the present process is terminated because no problem has occurred. When the toner supply level is prohibited (YES in Act 44), the process of Act 46 is executed.

  When the toner replenishment level is at a level where toner replenishment is prohibited, that is, when toner replenishment is abnormal, the value of the pixel count information toner replenishment time conversion table is changed in Act 46. .

  FIG. 13 is a diagram for explaining a method of changing the value of the pixel count information toner replenishment time conversion table in the image forming apparatus of the present embodiment.

  The horizontal axis of the coordinates in FIG. 13 represents the pixel count, and the vertical axis represents the toner replenishment time. A characteristic curve X represents the correspondence between the pixel count defined in the pixel count information toner supply time conversion table and the toner supply time.

  Therefore, as shown in FIG. 13A, changing the slope of the characteristic curve X avoids a transition to a forced toner supply level or a level where toner supply is prohibited. For this purpose, the slope of the current characteristic curve X is increased or decreased by a predetermined value.

  Further, as shown in FIG. 13 (2), the toner replenishment time is changed by moving the characteristic curve X up and down (or left and right) to shift to a forced toner replenishment level or a level where toner replenishment is prohibited. To avoid. For this purpose, the current characteristic curve X is moved up and down (or left and right) by a predetermined value.

  According to the embodiment described above, since the toner concentration in the developer in the developing device can be kept uniform, the quality of the printed image can be improved.

  Each function described in the above embodiment may be configured using hardware, or may be realized by reading a program describing each function into a computer using software. Each function may be configured by appropriately selecting either software or hardware.

  Furthermore, each function can be realized by causing a computer to read a program stored in a recording medium (not shown). Here, as long as the recording medium in the present embodiment can record a program and can be read by a computer, the recording format may be any form.

Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.
Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.
Hereinafter, the description of the claims at the beginning of the application of the present application will be added.
[1]
A developing device using a developer composed of toner and carrier;
A toner supply device for supplying toner to the developing device;
A control unit that acquires a toner amount to be replenished from a pixel count of an image to be printed, and variably controls a toner replenishment count according to the pixel count and an image printing speed;
An image forming apparatus comprising:
[2]
The image forming apparatus according to [1], wherein the control unit variably controls the time from when the image data to be printed is written on the photosensitive member to when the toner supply is started according to the image printing speed.
[3]
The control unit acquires the replenishment toner amount from the pixel count when the pixel count exceeds a predetermined threshold, and from the measured value of the toner density in the developing device when the pixel count is equal to or less than the predetermined threshold. The image forming apparatus according to [1] or [2], wherein a replenishment toner amount is acquired.
[4]
The image forming apparatus according to any one of [1] to [3], wherein a plurality of the image printing speeds are provided, and a developer circulation speed in the developing device is variable according to the image printing speed. .
[5]
The control unit continuously obtains the toner amount from the pixel count and replenishes the pixel count. When the toner concentration of the developer in the developing device falls outside a predetermined normal range, the control unit starts from the pixel count. The image forming apparatus according to any one of [1] to [4], wherein the correspondence relationship for obtaining the toner amount is changed.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10 ... Control part, 11 ... Control panel, 12 ... Memory part, 13 ... Image information management part, 14 ... Size information management part, 52 ... Toner supply port, 70 ... Partition plate, 102 ... Photoconductor DESCRIPTION OF SYMBOLS 103 ... Charging device 104 ... Exposure device 105 ... Developer device 108 ... Cleaner device 109 ... Primary transfer device 110 ... Transfer belt device 111 ... High voltage power source 112 ... Toner replenisher 213 ... Agitating mixer 214 ... Developing sleeve, 220 ... Toner density sensor.

Claims (4)

A developing device using a developer composed of toner and carrier;
A density sensor for detecting a toner density in the developing device;
A pixel counter that counts pixels per page of the image to be printed;
Each time a one-page image is printed, the density measurement value of the density sensor and the count of the pixel counter are referred to, and based on either the density measurement value by the density sensor or the pixel count by the pixel counter, the developing device A toner supply device for supplying toner;
First control means for performing toner replenishment with a replenishment toner amount acquired from a density measurement value of the density sensor when a pixel count by the pixel counter is equal to or less than a predetermined threshold;
Setting means for setting the number of toner replenishment to the developing device according to the amount of toner to be replenished acquired from the pixel count and the image printing speed when the pixel count by the pixel counter exceeds a predetermined threshold;
When the number of toner replenishments is set to a plurality of times by the setting means and any one of the plurality of replenishments is performed, the density sensor is used to perform replenishment from the replenishing device each time one page image is printed. In addition to referring to the density value, referring to the measured value of the density sensor, it is confirmed that the measured value of the toner density in the developing device is a predetermined supply level that is not a supply prohibition level. Second control means for implementing
An image forming apparatus comprising: When the printing end sequence is input, the replenishment scheduled to be executed after the end of printing is not executed, and whether or not there is a toner replenishment request with reference to the density value of the density sensor is stored in the memory. The image forming apparatus according to claim 1, wherein when a print request is stored in the memory, toner is replenished in a next print job . The image forming apparatus according to claim 2, wherein the toner supply in the next print job is started based on an image writing operation signal of the next job . Further, when the pixel count replenishment by acquiring and replenishing the toner amount from the pixel count is continued and the toner concentration of the developer in the developing device falls outside a predetermined normal range, the toner amount is deduced from the pixel count. relationship with a changing means for changing the image forming apparatus according to any one of claims 1 to 3 for finding.

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