JP2009025516A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus wherein a driving source is used in common as a developing unit driving source and as a toner supply driving source, and then, in changing the process speed, a difference in a toner supply amount per page according to process speed can be reduced. <P>SOLUTION: The image forming apparatus includes: an image carrier 2; a rotary developing device 5 having four developing units 10Y, 10M, 10C and 10K for developing an electrostatic latent image formed on the image carrier 2 with the toner; a toner supply means for supplying the toner to a developing chamber of each developing unit; a driving source used in common for the developing units and for the toner supply means; and a toner supply control part that changes the time for driving the toner supply means by the driving source, in accordance with the operating speed of the image carrier 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  As one method for reducing the cost of an image forming apparatus, a driving source for a developing device (hereinafter referred to as “developing device driving source”) and a driving source for toner supply (hereinafter referred to as “toner replenishing driving source”) are commonly used. On the other hand, in recent years, image forming apparatuses are mainly provided with functions of a high image quality mode and a high productivity mode according to various needs, and image forming processing is performed according to each mode. There may be multiple speeds (hereinafter referred to as “process speeds.”) To prevent image quality defects (BCO, fog, toner cloud, etc.) while stabilizing the image density, the toner density in the development chamber is the target. It is important to control according to the range.

  As described above, when the developing device drive source and the toner replenishment drive source are common and there are a plurality of process speeds, the toner replenishment rate differs depending on the process speed. For this reason, it is important to implement toner density control corresponding to different toner replenishment rates. The toner replenishment rate refers to the amount of toner per unit time replenished to the developing chamber by driving the toner replenishing means.

  As a conventional technique related to toner density control, for example, Japanese Patent Application Laid-Open No. 2004-259542 discloses a technique for solving a problem that a toner replenishment rate changes due to manufacturing variation and deterioration of a toner replenishment roller, toner fluidity change, and toner amount change. An invention relating to an electrophotographic apparatus having means for changing the replenishment time per toner replenishment or the rotation speed of the toner replenishment roller per toner replenishment is disclosed.

  Patent Document 2 listed below is based on the density measurement value of a black reference patch formed by a black developer in a single color image formation mode (monochrome image formation mode) and a multicolor image formation mode (full color image formation mode). An invention relating to an image forming apparatus that controls the amount of toner replenished to the black developer is disclosed.

JP 2002-49234 A JP 2001-34018 A

  The present invention provides an image forming apparatus capable of reducing the difference in toner replenishment amount per page for each process speed when the developing device drive source and the toner replenishment drive source are shared to change the process speed. The purpose is to do.

  According to a first aspect of the present invention, there is provided an image carrier, a developing unit that develops an electrostatic latent image formed on the image carrier with toner, and a toner replenishing unit that replenishes the developing unit with the toner. A driving source common to the developing means and the toner replenishing means, and a toner replenishing control means for changing the driving time of the toner replenishing means using the driving source according to the operating speed of the image carrier. An image forming apparatus characterized by the above.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the toner replenishment control unit is configured such that when the operation speed of the image carrier is relatively high, the driving time of the toner replenishment unit is relative. If the operation speed of the image carrier is relatively slow, the drive time of the toner replenishing means is changed to be relatively long.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the toner replenishment control means uses a coefficient for multiplying a toner replenishment time calculated based on toner density control information by the image carrier. It is characterized by switching according to the operation speed.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the toner replenishment control unit uses the toner replenishment time calculated based on the toner density control information as an addition value to the toner replenishment buffer time. When the toner replenishment buffer process is performed with the drive time of the toner replenishing means as a subtraction value from the toner replenishment buffer time, the coefficient to be multiplied by the subtraction value is switched according to the operating speed of the image carrier. It is a feature.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the toner replenishment control unit is configured to allow a toner replenishment drive time allowed for one development period in accordance with the operation speed of the image carrier. The upper limit value is changed.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the toner replenishment control unit performs toner replenishment operation at a maximum of n times by t time within one development period (n is a natural number of 2 or more). ), The value of t and / or the value of n is changed according to the operating speed of the image carrier.

  According to the first aspect of the present invention, when the developing device driving source and the toner replenishing driving source are made common and the process speed is changed, one page for each process speed is obtained as compared with the case where this configuration is not provided. The difference in the toner replenishment amount can be reduced.

  According to the second aspect of the present invention, the driving time of the toner replenishing means can be changed so that the difference in toner replenishment amount due to the difference in toner replenishment rate becomes small.

  According to the third aspect of the present invention, when controlling the drive time of the toner supply means with reference to the toner supply time calculated based on the toner density control information, the drive time of the toner supply means is imaged. It can be changed according to the operating speed of the holding body.

  According to the fourth aspect of the present invention, when the driving time of the toner replenishing means is controlled by the toner replenishing buffer process, the driving time of the toner replenishing means can be changed according to the operating speed of the image holding member. .

  According to the fifth aspect of the present invention, even when the toner replenishment rate changes depending on the operation speed of the image carrier, the agitating property and the charging property of the toner can be maintained satisfactorily.

  According to the sixth aspect of the present invention, the upper limit value of the toner replenishment drive time can be freely changed using the value of t and the value of n applied to the toner replenishment operation as parameters.

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

  FIG. 1 is a schematic diagram illustrating an example of the overall configuration of an image forming apparatus according to an embodiment of the present invention. The illustrated image forming apparatus 1 generally includes an image carrier 2, a charging device 3, an exposure device 4, a rotary developing device 5, an intermediate transfer member 6, a primary transfer device 7, and a secondary transfer device 8. And a fixing device 9.

  The image carrier 2 is rotationally driven in the R1 direction (counterclockwise direction) at a constant peripheral speed during image formation. The image carrier 2 is constituted by a photosensitive drum. The charging device 3 charges the surface (outer peripheral surface) of the image carrier 2 to a predetermined potential. The exposure device 4 forms an electrostatic latent image on the surface of the image carrier 2 charged to a predetermined potential by, for example, laser beam exposure scanning.

  The rotary developing device 5 forms a toner image on the image carrier 2 by developing the electrostatic latent image formed on the surface of the image carrier 2 with toner. The rotary developing device 5 is equipped with a yellow developing device 10Y, a magenta developing device 10M, a cyan developing device 10C, and a black developing device 10K. The rotary developing device 5 rotates at an angular pitch of 90 degrees in the R2 direction (clockwise direction), thereby being disposed at a position facing the image carrier 2 (hereinafter referred to as “development position”) ( 10Y, 10M, 10C, 10K).

  The rotary developing device 5 includes a toner cartridge 11Y that stores yellow toner, a toner cartridge 11M that stores magenta toner, a toner cartridge 11C that stores cyan toner, and a toner cartridge 11K that stores black toner. Has been. Among these, the size (volume) of the toner cartridge 11K is larger than the sizes of the other toner cartridges 11Y, 11M, and 11C.

  The intermediate transfer member 6 is constituted by an endless belt member. The intermediate transfer member 6 is supported by three belt support rolls 12, 13, and 14. The three belt support rolls 12, 13, and 14 support the intermediate transfer body 6 with a predetermined tension and move (run) the intermediate transfer body 6 at a predetermined speed in the Y direction, which is the image forming process direction. It is.

  The primary transfer device 7 is disposed so as to face the image carrier 2 with the intermediate transfer member 6 interposed therebetween. The primary transfer device 7 transfers the toner image held on the image holding body 2 to the intermediate transfer body 6.

  In addition to the charging device 3 and the rotary developing device 5 described above, a cleaning device 15 is provided around the image carrier 2. The cleaning device 15 removes toner remaining on the image carrier 2 without being transferred to the intermediate transfer member 6 at a position where the primary transfer device 7 and the image carrier 2 are opposed to each other.

  The secondary transfer device 8 transfers the toner image transferred to the intermediate transfer body 6 onto a sheet (recording medium) (not shown). The fixing device 9 fixes the toner image on the paper by heating and pressurizing the paper (not shown) onto which the toner image has been transferred by the secondary transfer device 8.

  Among the three belt support rolls 12, 13, and 14, a density detection sensor 16 is disposed in the vicinity of the belt support roll 12 so as to face the intermediate transfer body 6 wound around the belt support roll 12. . The density detection sensor 16 detects the density of toner patches formed for the purpose of density control, among the toner images transferred to the intermediate transfer body 6 by the primary transfer device 7.

  An intermediate transfer body cleaning device 17 is disposed near the belt support roll 14 so as to face the intermediate transfer body 6 wound around the belt support roll 14. The intermediate transfer member cleaning device 17 removes toner remaining on the intermediate transfer member 6 without being transferred onto the sheet by the secondary transfer device 8.

  In the image forming apparatus 1 having the above-described configuration, the surface of the image carrier 2 is charged to a predetermined potential by the charging device 3 and the charged portion is exposed by the exposure device 4 so that the surface of the image carrier 2 is exposed. An electrostatic latent image is formed. This electrostatic latent image is developed into a toner image by the rotary developing device 5.

  At that time, when forming a black monochrome image, the rotary developing device 5 is rotated and stopped so that the black developing device 10K is disposed at the developing position, and in this state, the electrostatic latent image is driven by the developing device 10K. To a black toner image. On the other hand, when a full-color multicolor image is formed, each time an electrostatic latent image for each color is formed on the surface of the image carrier 2, a corresponding developing device (10Y, 10M, 10C, 10K) is formed. ) Are rotated and stopped repeatedly so that the electrostatic latent image is driven by the developing device for each color (10Y, 10M, 10C, 10K) each time. Develop.

  The toner image developed by the rotary developing device 5 is transferred from the image holding member 2 to the intermediate transfer member 6 by the primary transfer device 7. In the case of forming a multicolor image, the toner image of each color is transferred onto the intermediate transfer body 6 by repeating the transfer of the toner image by the primary transfer device 7. The toner image transferred to the intermediate transfer member 6 in this way is transferred onto the paper by the secondary transfer device 8 and then fixed onto the paper by the fixing device 9.

  FIG. 2 is a cross-sectional view showing a configuration of a developing device mounted on the rotary developing device. Since the basic configurations of the developing units 10Y, 10M, 10C, and 10K for the respective colors described above are common regardless of the development color, the configuration of one developing unit will be described as an example here.

  The illustrated developing device 10 includes a developing roll 100, a first auger 101, a second auger 102, and a third auger 103. The developing roll 100, the first auger 101, the second auger 102, and the third auger 103 are arranged in parallel to each other. The developing roll 100, the first auger 101, and the second auger 102 are provided as developing means, and the third auger 103 is provided as a toner replenishing means.

  The developing roll 100 magnetically attracts and holds the two-component developer composed of toner and carrier, and conveys the developer in the circumferential direction by the rotation of the roll itself. The developing roll 100 is configured using, for example, a magnet roll, and is disposed in the vicinity of the image carrier 2 when the developing device 10 is disposed at the developing position.

  The first auger 101 supplies the two-component developer to the developing roll 100 while conveying it in the axial direction. The second auger 102 charges the toner with a predetermined polarity by friction with the carrier by conveying the toner and the carrier while stirring. The first auger 101 and the second auger 102 are disposed in a developing chamber partitioned by a partition wall. In the following description, the developing chamber in which the first auger 101 is disposed is referred to as a first developing chamber, and the developing chamber in which the second auger 102 is disposed is referred to as a second developing chamber. In this case, the developing roll 100 is disposed facing the first developing chamber.

  The third auger 103 replenishes the second developing chamber with toner by conveying toner taken from a toner cartridge (not shown) at a position P1 in the drawing. The third auger 103 conveys toner by the rotation of the auger itself. For this reason, when the rotation speed of the third auger 103 is increased, more toner is conveyed. The third auger 103 is disposed in a toner supply chamber adjacent to the second developing chamber. The toner replenishing chamber is connected to the second developing chamber at a position P2 in the drawing. The second developing chamber is connected to the first developing chamber at the position P3 in the drawing.

  Each of the first auger 101, the second auger 102, and the third auger 103 is formed with a spiral projection. Each auger 101, 102, 103 conveys developer and toner in the direction of the rotation axis by its own rotation. The developer conveying direction by the first auger 101 is set to the right in the figure, the developer conveying direction by the second auger 102 is set to the left in the figure, and the toner conveying direction by the third auger 103 is shown in the figure. It is set to the right direction.

  Therefore, the toner taken from the toner cartridge at the P1 position is conveyed rightward in the drawing toward the P2 position in the toner supply chamber according to the rotation of the third auger 103, and is sent from the P2 position to the second developing chamber. It is. In the second developing chamber, the toner and the carrier are agitated according to the rotation of the second auger 102, and the agitated two-component developer is conveyed in the left direction in the drawing toward the position P3. The developer thus transported in the second developing chamber is fed into the first developing chamber from the position P3 and is transported in the axial direction of the developing roll 100 (right direction in the drawing) as the first auger 101 rotates.

  The driving source for rotating the developing roll 100, the first auger 101 and the second auger 102, and the driving source for rotating the third auger 103 are constituted by a common (same) driving source. . That is, the developing device drive source and the toner supply drive source are shared. Here, a drive motor 104 is used as a common drive source. The coupling between the developing device 10 and the drive motor 104 is performed by the coupling member 105 when the developing device 10 is disposed at the development position. When the developing roll 100, the first auger 101, the second auger 102, and the third auger 103 are rotated using the driving motor 104 as a common driving source, the developing roll 100 and each auger are proportional to the rotational speed of the driving motor 104. Each of 101, 102, and 103 rotates at a predetermined speed.

  Further, in a state where the developing device 10 and the drive motor 104 are connected by the coupling member 105, the third auger 103 is turned on (turned on) and turned off (turned off) by using, for example, a clutch. Rotation (replenishment of toner) can be started or ended at an arbitrary timing. Therefore, when the toner supply operation is performed with the developing device 10 placed at the developing position, the third auger 103 rotates with the clutch on, and the rotation of the third auger 103 stops with the clutch off. Become.

  In the embodiment of the present invention, a configuration in which power transmission from the drive motor 104 to the third auger 103 is interrupted by a clutch is employed, but an intermittent means other than the clutch may be employed.

  FIG. 3 is a block diagram showing an example of a functional configuration of the toner density control system in the image forming apparatus according to the embodiment of the present invention. The toner replenishment control unit 21 calculates a toner replenishment time based on various types of information (hereinafter referred to as “toner concentration control information”) that is taken in to stably control the toner concentration in the developing chamber. The driving of the third auger 103 is controlled.

  The toner supply control unit 21 is configured to take in information from the density detection sensor 16 and information from the pixel counter 22 as an example of toner density control information. The information from the density detection sensor 16 is information indicating the density of the toner patch developed by any of the developing devices 10 of the rotary developing device 5. The pixel counter 22 counts the number of pixels (number of effective pixels) of image data per page (one sheet of paper). Therefore, the information from the pixel counter 22 is information indicating the pixel count value per page.

  The toner density control information may be an image density per page (a value obtained by dividing the total number of pixels in one page by the number of effective pixels), or the two-component developer in the developing device 10. It may be information obtained by a TC (toner concentration) sensor that detects a toner mixing ratio (a mixing ratio of toner to developer). Information obtained by a density detection sensor that detects the density of the toner patch formed on the surface of the image carrier 2 may also be used.

  The clutch control unit 23 turns the clutch on and off according to an instruction from the toner replenishment control unit 21, thereby transmitting the rotational driving force from the drive motor 104 to the third auger 103 and cutting the transmission. Is. The memory 24 is used for storing various data and information related to toner replenishment control.

  In the toner density control system configured as described above, the toner replenishment control unit 21 predicts the toner consumption amount per page based on the pixel count value information fetched from the pixel counter 22 and calculates the toner consumption amount. A toner replenishment time required to replenish a corresponding amount of toner to the developing chamber is calculated. The third auger 103 is referred to (used as a control parameter) with reference to the toner replenishment time within a period during which development is performed with any one developing device arranged at the development position (hereinafter referred to as “development period”). Is used to control toner supply to the developing chamber. One development period is defined as a period from when rotation of the rotary developing device 5 is stopped and a predetermined (arbitrary one) developing device is arranged at the developing position until rotation of the rotary developing device 5 is resumed. Is done. With respect to the developing period of a certain developing device, the rotary developing device 5 rotates 360 degrees from the end of the previous developing period until the next developing period is reached. The toner replenishment control method based on the pixel count value described above is also called an ICDC (Image Count Dispense Control) method.

  The toner supply control unit 21 uses, in addition to the ICDC toner density control using the pixel counter 22, ADC (Auto Density Control) toner density control using the density detection sensor 16. When the ADC toner density control is used in combination, for example, each time a toner image corresponding to a preset number of pages is developed, the density of the toner patch is detected by the density detection sensor 16, and the toner is replenished based on the detection result. Calculate time. The toner replenishment drive time calculated by the ADC method is a negative value corresponding to the density difference when the density of the toner patch detected by the density detection sensor 16 is higher than the target reference density, and the toner patch density Is lower than the reference density, it becomes a positive value according to the density difference.

When the toner supply time calculated by the ICDC method is defined as “ICDC toner supply time” and the toner supply time calculated by the ADC method is defined as “ADC toner supply time”, the toner supply control unit 21 defines the following (1). The toner replenishment time is obtained by the formula.
Toner replenishment time = ICDC toner replenishment time + ADC toner replenishment time (1)

  On the other hand, the process speed of image formation is determined by the peripheral speed of the image carrier 2 and the moving speed of the intermediate transfer member 6 at the development position. The peripheral speed of the image carrier 2 corresponds to the operation speed of the image carrier in the present invention. For this reason, the process speed of image formation coincides with the operation speed (circumferential speed) of the image carrier 2 at the time of image formation. The peripheral speed of the developing roll 100 is set so as to maintain a constant ratio with the peripheral speed of the image carrier 2. For this reason, the peripheral speed of the developing roll 100 is proportional to the process speed. Therefore, for example, when there are a plurality of process speeds due to differences in image quality required (set) in image formation, the peripheral speed of the developing roll 100 changes in proportion to the process speed applied to image formation. In the present embodiment, as an example, it is assumed that the process speed of image formation (the peripheral speed of the image carrier 2) is switched in three stages according to image formation conditions such as image quality settings. In addition, the three-stage process speed is divided into the normal (standard) speed "medium speed", "high speed" faster than "medium speed", and "low speed" slower than "medium speed" And

  The amount of toner per unit time replenished to the developing chamber by the rotation of the third auger 103, that is, the toner replenishment rate, depends on the rotation speed of the third auger 103. Specifically, the toner supply rate increases as the rotational speed of the third auger 103 increases. Further, since the rotation speed of the third auger 103 is proportional to the rotation speed of the developing roll 100 due to the common use of the drive source, when the process speed applied to image formation changes, the toner replenishment rate also changes accordingly. It will be. That is, the process speed and the toner replenishment rate are proportional to each other. Therefore, even if the third auger 103 is rotated by the same amount of time, the toner replenishment amount changes as the process speed changes. The toner replenishment amount refers to the amount of toner replenished to the developing chamber by driving the toner replenishing means (the third auger 103 in this embodiment).

Here, the time for actually driving the toner replenishing means is defined as the toner replenishing driving time, the unit of the toner replenishing driving time is millisecond (msec), the unit of the toner replenishing amount is milligram (mg), and the toner replenishing time. When the unit of rate is milligram (mg) / second (sec), the relationship of the following equation (2) is established between them.
Toner replenishment amount = toner replenishment rate × 10 ⁻³ × toner replenishment drive time (2)

  In the above equation (2), if the toner replenishment drive time is constant, the toner replenishment amount increases as the toner replenishment rate increases, and conversely, the toner replenishment amount decreases as the toner replenishment rate decreases. As a specific example, if the toner replenishment drive time is constant at 1000 msec, the toner replenishment amount is 200 mg when the toner replenishment rate is 200 mg / sec, and the toner replenishment amount is 300 mg when the toner replenishment rate is 300 mg / sec. Become. For this reason, a difference of 100 mg occurs in the toner replenishment amount due to the difference in toner replenishment rate.

  On the other hand, in the image forming apparatus 1 according to the present invention, the toner replenishment rate is determined according to the process speed for determining the toner replenishment rate so that the toner replenishment amount does not change even if the toner replenishment rate changes depending on the process speed. The toner supply control unit 21 performs processing (details will be described later) for changing the drive time (toner supply drive time) of the third auger 103 using the drive motor 104. In such processing, when the process speed (the operation speed of the image carrier) is relatively high, the driving time of the third auger 103 is changed to be relatively short, and when the process speed is relatively slow, The driving time of the third auger 103 is changed to be relatively long. As a result, as compared with the case where the toner replenishment drive time is constant as described above, the difference in toner replenishment amount due to the difference in toner replenishment rate is reduced.

  As a specific example, assuming that the toner replenishment drive time applied when the toner replenishment rate = 200 mg / sec is 1000 msec, and the toner replenishment drive time applied when the toner replenishment rate = 300 mg / sec is 700 msec, the toner replenishment rate = 200 mg / sec, the toner supply amount is 200 mg, and when the toner supply rate = 300 mg / sec, the toner supply amount is 210 mg. Therefore, even if the toner replenishment rate is different, the difference in toner replenishment amount is 10 mg, which corresponds to 1/10 of the amount when the toner replenishment drive time is constant.

<Toner Supply Control Process According to First Embodiment>
FIG. 4 is a flowchart showing the procedure of toner supply control processing according to the first embodiment of the present invention. First, the toner replenishment control unit 21 determines whether the process speed notified from an image formation control unit (not shown) is set to “high speed”, “medium speed”, or “low speed” (step S1).

  If it is determined in step S1 that the process speed is set to "high speed", the coefficient M1 stored in the memory 24 corresponding to the "high speed" process speed is read (step S2). If it is determined that the process speed is set to “medium speed”, the coefficient M2 stored in the memory 24 corresponding to the process speed of the “medium speed” is read (step S3). Is determined to be set to “low speed”, the coefficient M3 stored in the memory 24 corresponding to the “low speed” process speed is read (step S4). These three coefficients M1, M2, and M3 are set to have a magnitude relationship of “M1 <M2 <M3”.

  Next, the toner replenishment control unit 21 multiplies the ICDC toner replenishment time calculated by the ICDC method by the coefficient M1, M2 or M3 read in step S2, S3 or S4, thereby obtaining the ICDC toner replenishment time. Correction is performed (step S5). Specifically, when the process speed is set to “high speed”, the ICDC toner replenishment time is multiplied by a coefficient M1. When the process speed is set to “medium speed”, the ICDC toner replenishment time is multiplied by the coefficient M2, and when the process speed is set to “low speed”, the coefficient M3 is set to the ICDC toner replenishment time. Multiply.

  Next, the toner replenishment control unit 21 multiplies the ADC toner replenishment time calculated in the ADC system by the coefficient M1, M2 or M3 read in step S2, S3 or S4, thereby obtaining the ADC toner replenishment time. Correction is performed (step S6). Specifically, when the process speed is set to “high speed”, the ADC toner replenishment time is multiplied by a coefficient M1. When the process speed is set to “medium speed”, the ADC toner replenishment time is multiplied by the coefficient M2, and when the process speed is set to “low speed”, the coefficient M3 is set to the ADC toner replenishment time. Multiply.

  Next, the toner replenishment controller 21 uses the ICDC toner replenishment time corrected in step S5 and the ADC toner replenishment time corrected in step S6 to determine the toner replenishment time to be applied to the toner replenishment operation (1). Calculation is performed according to the equation (step S7).

  Next, the toner replenishment control unit 21 gives a command to the clutch control unit 23 to turn on and off the clutch based on the toner replenishment time calculated in step S7, thereby rotating the third auger 103 to perform a toner replenishment operation. Is executed (step S8).

  In the above processing flow, when the process speed of image formation is set to “high speed”, the toner replenishment time (ICDC toner replenishment time + ADC toner replenishment time) is corrected using the smallest coefficient M1, and the process speed is corrected. Is set to “low speed”, the toner replenishment time is corrected using the largest coefficient M3.

  Therefore, for example, assuming that each coefficient is set to M1 = 0.8, M2 = 1.0, and M3 = 1.2, if the process speed is set to “high speed”, the toner If the replenishment time is shortened and the process speed is set to “low speed”, the toner replenishment time is corrected in a longer direction. As a result, in the actual toner replenishment operation, when the process speed is set to “high speed”, the toner replenishment drive time is changed to be shorter than when the process speed is set to “medium speed”. When the speed is set to “low speed”, the toner replenishment drive time is changed to be longer than when the speed is set to “medium speed”.

  As a specific example, image data having a common ICDC toner replenishment time of 1000 msec calculated based on the number of pixels for one page is processed continuously for 10 pages with the same developing color by rotating the rotary developing device 5. The coefficient applied when the process speed is set to “high speed” is set to M1 = 0.8, the coefficient applied when the process speed is set to “medium speed” is set to M2 = 1.0, and “low speed” is set. It is assumed that the coefficient applied at the time of setting “is set to M3 = 1.2.

  In such a case, when the process speed is set to “medium speed”, the ICDC toner replenishment time is reflected in the toner replenishment drive time as it is, so that the toner replenishment drive time for processing image data for 10 pages is as follows. The total is 10,000 msec (one page average is 1000 msec). When the process speed is set to “high speed”, the value obtained by multiplying the ICDC toner replenishment time by the coefficient M1 = 0.8 is reflected in the toner replenishment drive time, so that 10 pages of image data are processed. In this case, the total toner replenishment drive time is 8000 msec (800 msec on an average per page). On the other hand, when the process speed is set to “low speed”, the value obtained by multiplying the ICDC toner replenishment time by the coefficient M3 = 1.2 is reflected in the toner replenishment drive time, so that 10 pages of image data are processed. In this case, the total toner replenishment drive time is 12000 msec (1 page average is 1200 msec).

  For convenience of explanation, the toner supply rate when the process speed is set to “high speed” is 1.2 mg / sec, the toner supply rate when the process speed is set to “medium speed” is 1.0 mg / sec, Assume that the toner replenishment rate when set to “low speed” is 0.8 mg / sec. In such a case, in the above example, the total toner supply amount for 10 pages when the process speed is set to “high speed” is 9.6 mg (average of 0.96 mg per page), and the process speed is set to “medium speed”. The total amount of toner replenishment for 10 pages is 10 mg (1 mg on a page average), and the total amount of toner replenishment for 10 pages when the process speed is set to “low” is 9.6 mg (0.96 mg on a page average) It becomes.

  On the other hand, for example, assuming that the coefficients M1, M2, and M3 are all set to 1.0, the total toner replenishment drive time when processing 10 pages of image data is Regardless of the speed, all are 10,000 msec (average of 1000 msec per page). Therefore, the total toner supply amount for 10 pages when the process speed is set to “high speed” is 12 mg (1.2 mg on an average for one page), and the toner supply amount for 10 pages when the process speed is set to “medium speed”. The total amount of toner replenishment for 10 pages when the process speed is set to “low” is 8.0 mg (0.8 mg on an average for one page).

  Therefore, for example, when image data for one page with the same number of pixels counted by the pixel counter 22 is formed on a sheet at a different process speed, the toner replenishment drive time is changed even if the toner replenishment rate changes depending on the process speed. Thus, the toner replenishment amount per page is equalized regardless of the process speed.

  By the way, the toner replenishing operation by the third auger 103 is performed at the maximum n times (n is a natural number of 2 or more) every t time within one development period in consideration of the stirring property and charging property of the toner. May be. In such a case, if the toner replenishment drive time t per toner replenishment operation is defined as the toner replenishment drive unit time, the upper limit value of the toner replenishment drive time allowed in one development period is defined by n × t time. It will be.

  Further, when a multicolor image is formed by the rotary developing device 5, the period during which the developing devices 10Y, 10M, 10C, and 10K are arranged at the developing position is limited. For this reason, if the toner replenishment time applied to the toner replenishment operation exceeds the upper limit (n × t time), toner replenishment may not be completed within one development period. In such a case, the toner replenishment operation is performed in consideration of the toner replenishment drive time that cannot be processed in the previous development period in the development period when the developing device of the same color is again placed at the development position. This compensates for the shortage of toner replenishment. In the following description, such processing is referred to as “toner supply buffer processing”.

  In the toner replenishment buffer process, the toner replenishment buffer time is stored in the memory 24 for each developing device 10 of each color. That is, the toner replenishment buffer time is stored in the memory 24 for each development color of yellow, magenta, cyan, and black. For the developing device 10 of the corresponding developing color, the toner replenishment time calculated by the ICDC method or the ADC method is added to the toner replenishment buffer time, while the driving time of the third auger 103 (toner replenishment driving time) ) Is subtracted from the toner replenishment buffer time, and toner replenishment buffer processing described later is performed while sequentially updating the toner replenishment buffer time in the memory 24.

<Concept of toner supply buffer processing>
When the toner replenishment operation is performed at the maximum n times (n is a natural number of 2 or more) every t time during one development period, the number of toner replenishment operations is determined based on the toner replenishment buffer time in each development period. Specifically, the number of toner replenishment operations is determined based on the quotient (integer) and the remainder obtained by dividing the toner replenishment buffer time by the value of t, and the toner corresponding to the number of times is determined. The replenishment drive time is subtracted from the toner replenishment buffer time, and the remainder is set as the carry-over amount to the next time. Further, when the toner replenishment buffer time exceeds t × n time that is the upper limit value of the toner replenishment drive time, the excess amount is carried over to the next time, and when the toner replenishment buffer time is a negative value, The toner replenishment buffer time is used as the carry-over to the next time.

<Example of toner supply buffer processing>
Now, in a system configuration of a toner concentration control system capable of performing a toner replenishment operation for a maximum of 3000 msec (n = 6, t = 500 msec) in one development period, it is stored in the memory 24 before entering the current development period. Assuming that the toner replenishment buffer time is 1000 msec, the toner replenishment operation by the third auger 103 is performed twice in 500 msec in this development period. For this reason, the toner replenishment buffer time stored in the memory 24 becomes 0 msec by subtracting 1000 msec reflected in the driving time of the third auger 103 in the current development period.

  On the other hand, assuming that the toner replenishment buffer time is 800 msec before entering the current development period, the toner replenishment operation by the third auger 103 is performed only once at 500 msec in the current development period. For this reason, the toner replenishment buffer time stored in the memory 24 is 300 msec by subtracting 500 msec reflected in the driving time of the third auger 103 in the current development period. The 300 msec time that could not be processed in the current development period is carried over to the next time. If the ICDC toner replenishment time calculated before the next development period is 800 msec, this time is added to the carry-over from the previous time (300 msec) and the next development period starts. For this reason, the toner replenishment buffer time before entering the next development period is 1100 msec. Therefore, in the next development period, the toner replenishing operation by the third auger 103 is performed twice in 500 msec.

  In addition, when the toner replenishment buffer time stored in the memory 24 is 300 msec and the ADC toner replenishment time calculated before the current development period is −500 msec, an addition process is performed by this. The toner replenishment buffer time in the memory 24 is −200 msec. For this reason, the toner replenishment operation by the third auger 103 is not performed during the current development period. In contrast, when the toner replenishment buffer time stored in the memory 24 is 300 msec and the ADC toner replenishment time calculated before the current development period is +200 msec, this is added to this. The toner replenishment buffer time in the memory 24 becomes 500 msec by the processing. For this reason, the toner replenishment operation by the third auger 103 is performed only once in 500 msec during the current development period.

<Toner Supply Control Process According to Second Embodiment>
FIG. 5 is a flowchart showing the procedure of toner supply control processing according to the second embodiment of the present invention. This process flow is applied when the above-described toner supply buffer process is performed. First, the toner replenishment control unit 21 determines whether the process speed notified from an unillustrated image formation control unit is set to “high speed”, “medium speed”, or “low speed” (step S11).

  If it is determined in step S11 that the process speed is set to "high speed", the coefficient M11 stored in the memory 24 corresponding to the "high speed" process speed is read (step S12). If it is determined that the process speed is set to “medium speed”, the coefficient M12 stored in the memory 24 corresponding to the process speed of the “medium speed” is read (step S13), and the process speed is read. Is determined to be set to “low speed”, the coefficient M13 stored in the memory 24 corresponding to the “low speed” process speed is read (step S14). These three coefficients M11, M12, and M13 are set to have a magnitude relationship of “M11> M12> M13”.

  Next, the toner replenishment control unit 21 calculates the coefficients M11, M11 read in step S12, S13 or S14 during the driving time of the third auger 103, which is the first subtraction value from the toner replenishment buffer time in the toner replenishment buffer process. The first subtraction value is corrected by multiplying by M12 or M13 (step S15). Specifically, when the process speed is set to “high speed”, the first subtraction value (toner supply drive time) is multiplied by the coefficient M11, and when the process speed is set to “medium speed”. The first subtraction value is multiplied by a coefficient M12. If the process speed is set to “low speed”, the first subtraction value is multiplied by a coefficient M13.

  Next, the toner replenishment control unit 21 performs the coefficient M11 read in step S12, S13 or S14 during the overrun time of the third auger 103, which is the second subtraction value from the toner replenishment buffer time in the toner replenishment buffer process. , M12 or M13 to correct the second subtraction value (step S16). Specifically, when the process speed is set to “high speed”, the second subtraction value (overrun time) is multiplied by the coefficient M11, and when the process speed is set to “medium speed”, The subtraction value of 2 is multiplied by the coefficient M12, and when the process speed is set to “low speed”, the second subtraction value is multiplied by the coefficient M13.

  The overrun time of the third auger 103 is the time until the rotation of the third auger 103 is completely stopped after the clutch control unit 23 switches the clutch from on to off, that is, the inertia of rotation than the toner replenishment drive time. This is the time during which the third auger 103 rotates excessively by force. This overrun time is a time experimentally obtained in advance. In the toner replenishment buffer process, this overrun time does not necessarily need to be included in the subtracted value from the toner replenishment buffer time.

  Next, the toner supply control unit 21 updates the toner supply buffer time by applying the first subtraction value corrected in step S15 and the second subtraction value corrected in step S16 (step S17). Specifically, the first subtraction value corrected in step S15 and the second subtraction value corrected in step S16 are added, and this addition value is stored in the memory 24 at that time. By subtracting from the buffer time, the toner supply buffer time applied to the toner supply operation is updated in the next development period, and the updated toner supply buffer time is held in the memory 24.

  In the above processing flow, when the image forming process speed is set to “high speed”, the first subtraction value and the second subtraction value are corrected using the largest coefficient M11, and the process speed is “ If it is set to “low speed”, the first and second subtraction values are corrected using the smallest coefficient M13.

  Therefore, for example, assuming that each coefficient is set to M11 = 1.2, M12 = 1.0, and M13 = 0.8, when the process speed is set to “high speed”, When the process speed is set to “low speed”, each subtraction value is corrected to become smaller. As a result, in the actual toner replenishment operation, when the process speed is set to “high speed”, the toner replenishment drive time is changed to be shorter than when the process speed is set to “medium speed”. When the speed is set to “low speed”, the toner replenishment drive time is changed to be longer than when the speed is set to “medium speed”.

  As a specific example, image data having a common ICDC toner replenishment time of 1000 msec calculated based on the number of pixels for one page is processed continuously for 10 pages with the same developing color by rotating the rotary developing device 5. In this case, as described above, the coefficient applied when the process speed is set to “high speed” is set to M11 = 1.2, and the coefficient applied to the setting of “medium speed” is set to M12 = 1.0. Suppose that the coefficient applied when setting “low speed” is set to M13 = 0.8.

  In such a case, when the process speed is set to “medium speed”, the ICDC toner supply time is directly reflected in the toner supply drive time in the toner supply buffer process, and therefore, when image data for 10 pages is processed. The total toner replenishment drive time is 10,000 msec.

  On the other hand, when the process speed is set to “high speed” or “low speed”, the toner replenishment buffer process is performed according to the flow of numerical processing as shown in FIG. For example, when the process speed is set to “high speed”, the toner replenishment buffer time becomes 1000 msec by adding the ICDC toner replenishment time for the image data of the first page. It will be done in two steps. Therefore, the toner replenishment drive time is 1000 msec, and the subtraction value (buffer subtraction value) from the toner replenishment buffer time is 1200 msec by multiplication with the coefficient M11 = 1.2. Therefore, the carry-over time to the next time is −200 msec.

  For the image data of the second page when the process speed is set to “high speed”, the toner supply buffer time is 800 msec by adding the ICDC toner supply time for one page to the carry-over time from the previous time. Therefore, based on this, the toner replenishment operation is performed only once in 500 msec. For this reason, the toner replenishment drive time is 500 msec, and the subtracted value from the toner replenishment buffer time is 600 msec by multiplication with the coefficient M11 = 1.2. Therefore, the carry-over time to the next time is +200 msec.

  On the other hand, when the process speed is set to “low speed”, the toner replenishment buffer time becomes 1000 msec by adding the ICDC toner replenishment time for the image data of the first page. It will be done in two steps. For this reason, the toner replenishment drive time is 1000 msec, and the subtracted value from the toner replenishment buffer time is 800 msec by multiplication with the coefficient M13 = 0.8. Therefore, the carry-over time to the next time is +200 msec.

  For the image data of the second page when the process speed is set to “low speed”, the toner supply buffer time is 1200 msec by adding the ICDC toner supply time for one page to the carry-over time from the previous time. Therefore, based on this, the toner replenishing operation is performed twice in 500 msec. For this reason, the toner replenishment drive time is 1000 msec, and the subtracted value from the toner replenishment buffer time is 800 msec by multiplication with the coefficient M13 = 0.8. Therefore, the carry-over time to the next time is +400 msec.

  As a result, the total toner replenishment drive time for 10 pages when the process speed is set to “high speed” is 8500 msec (an average of 850 msec per page), and the process speed is set to “medium speed”. The total toner replenishment drive time for 10 pages is 10000 msec (an average of 1000 msec per page), and the total toner replenishment drive time for 10 pages when the process speed is set to “low speed” is 12000 msec (1 page) (Average 1200 msec).

  For convenience of explanation, the toner supply rate when the process speed is set to “high speed” is 1.2 mg / sec, the toner supply rate when the process speed is set to “medium speed” is 1.0 mg / sec, Assume that the toner replenishment rate when set to “low speed” is 0.8 mg / sec. In such a case, in the above example, the total toner supply amount for 10 pages when the process speed is set to “high speed” is 10.2 mg (1.02 mg on an average for one page), and the process speed is set to “medium speed”. The total amount of toner replenishment for 10 pages is 10 mg (1 mg on a page average), and the total amount of toner replenishment for 10 pages when the process speed is set to “low” is 9.6 mg (0.96 mg on a page average) It becomes.

  On the other hand, for example, assuming that the above coefficients M11, M12, and M13 are all set to 1.0, the total toner replenishment drive time when processing 10 pages of image data is the process Regardless of the speed, all are 10,000 msec (average of 1000 msec per page). Therefore, the total toner supply amount for 10 pages when the process speed is set to “high speed” is 12 mg (1.2 mg on an average for one page), and the toner supply amount for 10 pages when the process speed is set to “medium speed”. The total amount of toner replenishment for 10 pages when the process speed is set to “low” is 8.0 mg (0.8 mg on an average for one page).

  Therefore, for example, when image data for one page having the same number of pixels is formed on a sheet at a different process speed, even if the toner replenishment rate changes depending on the process speed, the third auger 103 is replenished to the developing chamber. The toner replenishment amount per page is equalized regardless of the process speed.

<Application example of the present invention>
As an application example of the present invention, when the toner replenishment control unit 21 performs the toner replenishment buffer process based on the processing flow shown in FIG. 5, the toner replenishment drive allowed for one development period according to the process speed. It is good also as a structure which changes the upper limit of time. For example, as described above, the upper limit value of the toner replenishment drive time is the value of t when the toner replenishment operation is performed at maximum n times (n is a natural number of 2 or more) every t time within one development period. It changes by changing the value of n.

  That is, if the value of t is a fixed value and the value of n is relatively large, the upper limit value of the toner replenishment drive time is changed. In contrast, if the value of n is relatively small, the toner replenishment drive is performed. It is changed in the direction that the upper limit of time becomes smaller. Further, if the value of n is fixed and the value of t is relatively increased, the upper limit value of the toner replenishment drive time is changed. In contrast, if the value of t is relatively decreased, the toner replenishment drive is performed. It is changed in the direction that the upper limit of time becomes smaller. Further, when both the value of t and the value of n are relatively increased, the upper limit value of the toner replenishment drive time is changed so as to increase. Conversely, when both the values of t and n are relatively decreased. The upper limit value of the toner replenishment drive time is changed in the direction of decreasing.

  FIG. 7 is a flowchart showing a procedure of toner supply control processing applied when the upper limit value of the toner supply drive time is changed according to the process speed. First, the toner replenishment control unit 21 determines whether the process speed notified from an image formation control unit (not shown) is set to “high speed”, “medium speed”, or “low speed” (step S21).

  When it is determined in step S21 that the process speed is set to “high speed”, the value N1 of the toner replenishment operation limit count stored in the memory 24 corresponding to the “high speed” process speed is read. (Step S22). If it is determined that the process speed is set to “medium speed”, the value N2 of the toner replenishment operation limit count stored in the memory 24 corresponding to the “medium speed” process speed is read ( If it is determined in step S23) that the process speed is set to "low speed", the value N3 of the toner replenishment operation limit count stored in the memory 24 corresponding to the "low speed" process speed is read (step S23). Step S24). These three values N1, N2, and N3 are all natural numbers and are set to have a magnitude relationship of “N1 <N2 <N3”.

  Next, the toner replenishment control unit 21 substitutes the value N1, N2 or N3 read in step S21, S22 or S23 for the value of n (step S25). With the above processing flow, the value of n is changed according to the process speed.

  In the processing flow shown in FIG. 7, the three values N1, N2, and N3 are set to have a magnitude relationship of “N1 <N2 <N3”. Therefore, when the process speed is set to “high speed”, Toner replenishment operation is less than when it is set to “Medium speed”, and when the process speed is set to “Low speed”, the toner supply operation is lower than when “Medium speed” is set. Increases the limit. Therefore, when the process speed is set to “high speed”, the upper limit value of the toner replenishment drive time is changed to be smaller than when the process speed is set to “medium speed”, and the process speed is set to “low speed”. If it is set, the upper limit value of the toner replenishment drive time is changed in a direction in which the upper limit of the toner replenishment drive time is larger than that in the case where “medium speed” is set.

  In the processing flow shown in FIG. 7, the value of n is changed according to the process speed. However, the value of t may be changed instead of the value of n. The processing flow in that case is the procedure of steps S31 to S35 in FIG. However, when changing any of the values of n and t, it is assumed that the upper limit value of the toner replenishment drive time becomes smaller as the process speed increases. For this reason, in the processing flow of FIG. 8, the values T1, T2, and T3 of the toner replenishment unit driving time read from the memory 24 in step S32, S33, or S34 are set to a magnitude relationship of “T1 <T2 <T3”. It will be.

1 is a schematic diagram illustrating an example of an overall configuration of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which shows the structure of a developing device. FIG. 3 is a block diagram illustrating a functional configuration example of a toner density control system. 4 is a flowchart illustrating a procedure of toner supply control processing according to the first embodiment of the present invention. 7 is a flowchart illustrating a procedure of toner supply control processing according to a second embodiment of the present invention. FIG. 6 is a diagram illustrating a flow of numerical processing in toner supply buffer processing. It is a figure which shows the processing flow which concerns on the application example of this invention. It is a figure which shows the processing flow which concerns on the application example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Image holding body, 5 ... Rotary developing device 10, 10Y, 10M, 10C, 10K ... Developing device, 100 ... Developing roll 100, 101 ... 1st auger, 102 ... 2nd auger, 103 ... 3rd auger, 104 ... drive motor, 21 ... toner supply control unit, 22 ... pixel counter, 23 ... clutch control unit, 24 ... memory

Claims (6)

An image carrier,
Developing means for developing the electrostatic latent image formed on the image carrier with toner;
Toner replenishing means for replenishing the developing means with the toner;
A common drive source for the developing means and the toner replenishing means;
An image forming apparatus comprising: a toner replenishing control unit that changes a driving time of the toner replenishing unit using the driving source in accordance with an operation speed of the image holding member. When the operation speed of the image carrier is relatively high, the toner replenishment control unit changes the driving time of the toner supply unit to be relatively short so that the operation speed of the image carrier is relatively low. 2. The image forming apparatus according to claim 1, wherein the toner replenishing unit is changed so as to have a relatively long driving time. The image forming apparatus according to claim 1, wherein the toner replenishment control unit switches a coefficient for multiplying a toner replenishment time calculated based on toner density control information according to an operation speed of the image holding member. apparatus. The toner replenishment control means uses the toner replenishment time calculated based on the toner density control information as an addition value to the toner replenishment buffer time, and the drive time of the toner replenishment means as a subtraction value from the toner replenishment buffer time. The image forming apparatus according to claim 1, wherein, when performing a toner replenishment buffer process, a coefficient to be multiplied by the subtraction value is switched according to an operation speed of the image holding member. The image forming apparatus according to claim 1, wherein the toner replenishment control unit changes an upper limit value of a toner replenishment drive time allowed in one development period according to an operation speed of the image carrier. . The toner replenishment control means performs the toner replenishment operation at a maximum of n times (n is a natural number of 2 or more) within one development period, depending on the operation speed of the image carrier. The image forming apparatus according to claim 5, wherein the value of t and / or the value of n is changed.

Images