JP2016009177A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which: execution of positional deviation correction and toner discharge respectively as calibration operations causes downtime, which reduces usability.SOLUTION: Control means causes light irradiation means to form an electrostatic latent image for correction and causes developing means to develop the electrostatic latent image as a toner image, so as to control in parallel an operation to control conditions for forming electrostatic latent images during image formation and an operation to supply toner to cleaning means.

Description

  The present invention relates to an image forming apparatus using an electrophotographic method, and more particularly, to an image forming apparatus capable of correcting misregistration using an electrostatic latent image for correction.

  In an electrophotographic image forming apparatus, a so-called tandem method is known in which image forming portions of respective colors are arranged side by side in order to perform image formation at high speed. In the tandem image forming apparatus, the toner images are sequentially transferred onto the intermediate transfer belt from the image forming portions of the respective colors, and the toner images transferred onto the intermediate transfer belt are transferred onto the recording material in a batch. Has been taken.

  In such an image forming apparatus, due to environmental factors, mechanical factors in the image forming unit for each color, image misregistration occurs in the image forming unit for each color, and color misregistration may occur when the images are superimposed. For this reason, a correction image, which is a toner image for correcting the misregistration, is formed on the intermediate transfer belt, and the misregistration correction is performed by detecting the relative misregistration of each color toner image by the optical sensor. Are known. However, when color misregistration correction is performed, if a correction image is formed on the photosensitive drum and the intermediate transfer belt, and further, the formed toner image is cleaned, downtime occurs and usability is reduced. become.

  Therefore, Patent Document 1 forms a toner image and corrects color misregistration by performing misregistration correction in an image forming unit for each color based on the detection result of the electrostatic latent image for correction formed on the photosensitive drum. It is disclosed that the frequency of performing is suppressed and the occurrence of downtime is suppressed.

JP 2012-32777 A

  By performing the misregistration correction using the electrostatic latent image for correction, it is possible to suppress the frequency of performing the color misregistration correction by forming the toner image. However, in the image forming apparatus, not only misalignment correction as a calibration operation, but also an operation called toner discharge that suppresses turning of the cleaning blade by supplying toner as a lubricant between the photosensitive drum and the cleaning blade. There is also. If the misregistration correction and the toner discharge operation are executed as calibration operations, downtime occurs and usability deteriorates.

  The invention according to the present application has been made in view of the above situation, and an object thereof is to suppress downtime required for calibration.

  In order to achieve the above object, the present invention provides a photosensitive member, a light irradiating unit for irradiating light to form a correcting electrostatic latent image on the photosensitive member, and the correcting electrostatic latent image as a toner. A developing means for developing as an image, a cleaning means for cleaning the toner image on the photoconductor, a detecting means for detecting an electrostatic latent image for correction formed on the photoconductor, and detected by the detecting means Control means for controlling a condition for forming an electrostatic latent image at the time of image formation based on the detection result, and the control means forms the electrostatic latent image for correction and the correction means. By developing the electrostatic latent image as a toner image, the operation for controlling the conditions for forming the electrostatic latent image during the image formation and the operation for supplying the toner to the cleaning unit are performed in parallel. It is characterized by controlling to.

  According to the configuration of the present invention, it is possible to suppress downtime required for calibration.

Schematic configuration diagram of an image forming apparatus High-voltage power supply configuration diagram Flow chart showing reference value acquisition processing The figure which shows a mode that the image for correction | amendment is formed, and the figure which shows a mode that the electrostatic latent image for correction | amendment is formed The figure which shows the surface potential change of the photosensitive drum by the electrostatic latent image 80 for correction | amendment. Flow chart of misalignment correction control using electrostatic latent image 80 for correction Timing chart showing combined use of misalignment correction control and discharge operation by electrostatic latent image 80 for correction The figure which showed the method of controlling the toner amount mounted when developing the electrostatic latent image 80 for correction | amendment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are not necessarily essential to the solution means of the present invention.

(First embodiment)
[Schematic configuration diagram of image forming apparatus]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment. Note that the letters a, b, c, and d at the end of the reference numerals are yellow (Y) and magenta (M), respectively, for the image (developer image) formed by the member and transferred to the intermediate transfer belt 30. , Cyan (C), and black (Bk). In the following description, when it is not necessary to distinguish between colors, the English letter a is used as a reference symbol in order to explain yellow (Y) as an example.

  The photosensitive drum 22a as a photosensitive member is driven to rotate. The charging roller 23a charges the surface of the corresponding photosensitive drum 22a to a uniform potential. For example, the charging bias output from the charging roller 23a is −1200V, and the surface of the photosensitive drum 22a is charged to a potential (dark potential) of −700V. The scanner unit 20a as a light irradiation unit scans the surface of the photosensitive drum 22a with a laser beam corresponding to image data of an image to be formed, and forms an electrostatic latent image on the photosensitive drum 22a. As an example, the potential (bright potential) of the portion where the electrostatic latent image is formed by scanning with the laser light 21a becomes −100V. The developing device 25a has a developer of a corresponding color, and the developer is supplied to the electrostatic latent image formed on the photosensitive drum 22a (on the photosensitive member) by the developing sleeve 24a, thereby the photosensitive drum 22a. The electrostatic latent image is developed. As an example, the developing bias output from the developing sleeve 24a is −350V, and the developing unit 25a attaches the developer to the electrostatic latent image by this potential.

  The primary transfer roller 26 a transfers the developer image (toner image) formed on the photosensitive drum 22 to an intermediate transfer belt 30 as an intermediate transfer member that is driven by rollers 31, 32, and 33. As an example, the transfer bias output by the primary transfer roller 26 a is +1000 V, and the primary transfer roller 26 a transfers the developer image to the intermediate transfer belt 30 by this potential. At this time, a color image is formed by superimposing the developer images on the respective photosensitive drums 22 a to 22 d and transferring them onto the intermediate transfer belt 30. The toner remaining on the photosensitive drum 22a without being transferred to the intermediate transfer belt 30 is cleaned by the cleaning blade 28a.

  The recording material 12 as paper loaded on the paper feed cassette is fed by a pickup roller 13. The fed recording material 12 is detected at the leading edge by the registration sensor 111 and conveyed to the conveying rollers 14 and 15. The secondary transfer roller 27 transfers the developer image formed on the intermediate transfer belt 30 to the recording material 12 being conveyed. The fixing roller pairs 16 and 17 heat and fix the developer image transferred to the recording material 12. The cleaning blade 35 collects in the container 36 the developer that has not been transferred from the intermediate transfer belt 30 to the recording material 12 by the secondary transfer roller 27. In addition, a sensor 40 is provided to face the intermediate transfer belt 30 in order to form a developer image and correct misregistration (color misregistration). The control unit 54 controls the entire image forming apparatus.

  The scanner unit 20a may be configured to expose the photosensitive drum 22a with an LED array or the like instead of a laser. Further, instead of providing the intermediate transfer belt 30, a direct transfer type image forming apparatus that directly transfers the developer images of the respective photosensitive drums 22a to 22d to the recording material 12 conveyed to the recording material conveyance belt may be used. . A group of members for forming developer images of the charging roller 23a, the developing device 25a, and the primary transfer roller 26a including the scanner unit 20a and the photosensitive drum 22a can be used as an image forming unit. In some cases, the image forming unit may be omitted without including the scanner unit 20a. Further, each member (charging roller 23a, developing device 25a, and primary transfer roller 26a) that is disposed in the vicinity of the photosensitive drum 22a and acts on the photosensitive drum 22a can be referred to as a process unit. Further, members such as the photosensitive drum 22a, the intermediate transfer belt 30, and the recording material conveyance belt that can carry the image (developer image) to be formed can also be called an image carrier. That is, a color image is formed by having a plurality of image forming units.

[Configuration diagram of high-voltage power supply]
FIG. 2A is a configuration diagram of a high-voltage power supply for supplying power. The supply of high-voltage power will be described with reference to FIG. The charging high-voltage power supply circuit 43a applies a voltage to the other charging roller 23. Thus, a background potential is formed on the surface of the photosensitive drum 22a, and an electrostatic latent image can be formed by irradiation of the laser light 21a from the scanner unit 20. The development high-voltage power supply circuit 44a applies a voltage to the corresponding development sleeve 24a. As a result, the electrostatic latent image on the photosensitive drum 22a is developed with toner to form a toner image. The primary transfer high-voltage power supply circuit 46a applies a voltage to the corresponding primary transfer roller 26a. As a result, the toner image formed on the photosensitive drum 22 a is primarily transferred onto the intermediate transfer belt 30. The secondary transfer high voltage power supply circuit 48 applies a voltage to the secondary transfer roller 27. As a result, the toner image on the intermediate transfer belt 30 is secondarily transferred to the recording material 12.

  The charging high-voltage power supply circuits 43a to 43d are provided with current detection circuits 50a to 50d, respectively. Each of the development high voltage power supply circuits 44a to 44d is provided with current detection circuits 45a to 45d. Each of the primary transfer high-voltage power supply circuits 46a to 46d includes current detection circuits 47a to 47d. The bias voltage (high voltage) to be applied is adjusted according to the detection results of these current detection circuits. As a result, it is possible to control the image forming performance to be constant with respect to temperature and humidity changes in the image forming apparatus and wear of the photosensitive drums 22a to 22d and the process means.

  Here, the configuration in which the current detection circuit is provided in each of the charging high-voltage power supply circuits 43a to 43d, the development high-voltage power supply circuits 44a to 44d, and the primary transfer high-voltage power supply circuits 46a to 46d has been described as an example. It is not limited. For example, a common current detection circuit may be provided for any or all of the charging high-voltage power supply circuits 43a to 43d. The same applies to the development high-voltage power supply circuits 44a to 44d and the primary transfer high-voltage power supply circuits 46a to 46d.

[Circuit diagram of high-voltage power supply]
The circuit configuration of the charging high-voltage power supply circuit 43a will be described with reference to FIG. 2B, taking the case of yellow in the high-voltage power supply device of FIG. 2A as an example. It should be noted that colors other than yellow can be similarly detected in the development high-voltage power supply circuit 44 and the primary transfer high-voltage power supply circuit 46.

  The transformer 62 boosts the voltage of the AC signal generated by the drive circuit 61 to an amplitude several tens of times. A rectifier circuit 51 including diodes 1601 and 1602 and capacitors 63 and 66 rectifies and smoothes the boosted AC signal. The rectified and smoothed voltage signal is output to the output terminal 53 as a DC voltage. The operational amplifier 60 is driven so that the voltage of the output terminal 53 divided by the detection resistors 67 and 68 is equal to the voltage set value 55 set by the engine control unit 54 (hereinafter also simply referred to as the control unit 54). The output voltage of the circuit 61 is controlled. Then, according to the voltage of the output terminal 53, current flows through the photosensitive drum 22, the charging roller 23, and the ground. In response to this current, the current detection circuit 50 outputs a detection voltage 56.

[Current detection circuit]
The current detection circuit 50 is inserted between the secondary circuit 500 of the transformer 62 and the ground point 57. A current flowing from the output terminal 53 to the current detection circuit 50 through the secondary circuit 500 of the transformer 62 flows from the operational amplifier 70 to the ground through the resistor 71. Further, since the inverting input terminal of the operational amplifier 70 is connected to the output terminal via the resistor 71 (negatively fed back), it is virtually grounded to the reference voltage 73 connected to the non-inverting input terminal. A detection voltage 56 proportional to the amount of current flowing through the output terminal 53 appears at the output terminal of the operational amplifier 70. The capacitor 72 is for stabilizing the inverting input terminal of the operational amplifier 70.

  The detection voltage 56 indicating the detected current amount is input to the negative input terminal (inverted input terminal) of the comparator 74. The threshold value Vref75 is input to the positive input terminal of the comparator 74. When the input voltage at the inverting input terminal falls below the threshold value, the output becomes Hi (positive) and the binarized voltage value 561 (Hi). Voltage) is input to the controller 54. The threshold value Vref75 is a value between a minimum value of the detection voltage 561 when a later-described electrostatic latent image for correcting misalignment passes a position facing the process means and a value of the detection voltage 561 before passing. Set to The rise and fall of the detection voltage 561 are detected by detecting the electrostatic latent image for correction once. For example, the control unit 54 sets the midpoint between the rising detection timing and the falling detection timing of the detection voltage 561 as the detection position of the electrostatic latent image for correction. Further, the control unit 54 may detect only one of the rising edge and the falling edge of the detection voltage 561.

[Block Diagram of Control Unit 54]
FIG. 2C shows a hardware block diagram and a functional block diagram of the control unit 54. First, a hardware block diagram will be described. The control unit 54 comprehensively controls the operation of the image forming apparatus 10. The CPU 321 uses the RAM 323 as a main memory and a work area, and controls each member related to image formation according to various control programs stored in the EEPROM 324. Further, the ASIC 322 performs control of each motor, high-voltage power supply control of the developing bias, and the like in various image forming sequences under the instruction of the CPU 321. Note that part or all of the functions of the CPU 321 may be performed by the ASIC 322, and conversely, part or all of the functions of the ASIC 322 may be performed by the CPU 321 instead. A part of the function of the control unit 54 may be assigned to hardware corresponding to the other control unit 54.

  Next, a functional block diagram will be described. The actuator 326 generically represents actuators such as a drive motor for the photosensitive drum 22a. The sensor 325 generically represents sensors such as the registration sensor 111 and the current detection circuit 50. The control unit 54 controls image forming conditions based on information acquired from the various sensors 325. The patch forming unit 327 controls the scanner unit 20a to form a correction electrostatic latent image as a correction patch on the photosensitive drum 22a. The process means control unit 328 controls the operation and setting of each process means when detecting the electrostatic latent image for correction. The misregistration correction control unit 329 calculates the misregistration correction amount based on the detection result of the electrostatic latent image for correction detected by the detection voltage 561, and sets the image forming condition based on the calculated misregistration correction amount. Make corrections. That is, the conditions for forming an electrostatic latent image during image formation are controlled.

  Note that, in realizing the functions described above, the form of hardware is not limited, and any of the CPU 321, the ASIC 322, and other hardware may be operated, and any hardware may be used. Processing may be shared by each hardware by distribution.

[Color misregistration correction control using electrostatic latent image for correction]
Next, color misregistration correction control using the electrostatic latent image for correction will be described. As shown in FIG. 4B, a laser beam 21a is irradiated on the photosensitive drum 22a to form an electrostatic latent image 80 for correction. Here, as an example, the electrostatic latent image for correction is formed with a width of 30 lines, but the width is not limited to this. It is also possible to form a plurality of patterns as the electrostatic latent image 80 for correction on the photosensitive drum 22a. The time from the formation of the electrostatic latent image 80 for correction to the position of the charging roller 23a is measured by detecting a change in the charging current by the current detection circuit 50, and color misregistration correction is performed based on the measurement result. Set as a reference value for control.

  After setting the reference value, if a predetermined condition such as the temperature in the image forming apparatus changes due to continuous printing or the like, deformation of the optical elements including the reflecting mirror and lens in the scanner unit 20a occurs. Then, the scanning position of the laser beam on the photosensitive drum 22a varies. As a result, after color misregistration correction control using a toner image as a correction image is performed, the color misregistration becomes larger than when a correction electrostatic latent image 80 is formed and a reference value is set. End up. In order to correct this color misregistration, the in-machine temperature is monitored, for example, by a temperature sensor (not shown) under a predetermined condition. Perform correction control. Note that the timing for executing the misregistration correction is not limited to this. For example, the timing at which the electrostatic latent image formation position is deviated by half the sub-scanning direction pitch with respect to the reference position can be set. The amount of temperature shift that can cause such a deviation is estimated in advance through experiments or the like, and the value may be determined appropriately.

  The electrostatic latent image 80 for correction is formed under a predetermined condition, and the above-described time measurement is performed. Then, the time when the reference value is set and the time when the electrostatic latent image for correction 80 is formed under a predetermined condition are compared to calculate the color misregistration amount. Then, the timing of irradiating the laser beam 21a from the scanner unit 20a is corrected as the correction of the image forming condition so as to cancel the calculated color misregistration amount. A detailed description of this series of operations will be described later. Note that the correction of the image forming conditions is not limited to the correction of the timing of laser light irradiation. For example, the speed of the photosensitive drum 22a can be corrected, and the mechanical position of the reflection mirror of the scanner unit 20a can be corrected.

[Reference Value Acquisition Process Flowchart]
A flowchart illustrating reference value acquisition processing for color misregistration correction control according to the present embodiment will be described with reference to FIGS. First, the flowchart of FIG. 3A will be described. FIG. 3A shows the process for yellow, but the same process is performed for other colors.

  In step S <b> 301, the control unit 54 causes the image forming unit to form a toner mark (toner patch) that is an image for color misregistration correction on the intermediate transfer belt 30. Color misregistration correction control using a correction image will be described with reference to FIG. FIG. 4A is a diagram illustrating a state in which an image for correction is formed. Reference numerals 400 and 401 denote correction images for detecting a color misregistration amount in the recording material conveyance direction (sub-scanning direction). Further, tsf1 to ts4 and tsr1 to tsr4 are detection timings of the respective correction images. The arrow indicates the moving direction of the intermediate transfer belt 30. The correction images are formed on the intermediate transfer belt 30 at both ends in the direction (main scanning direction) perpendicular to the moving direction of the intermediate transfer belt 30. This is to detect the color misregistration amount at both ends in the main scanning direction and correct the color misregistration in view of the left / right difference. In order to detect correction images formed at both ends in the main scanning direction, two 40a and 40b are arranged at positions facing the correction images. In the present embodiment, a configuration in which two sensors are arranged is shown as an example, but the number of sensors is not limited to this.

In performing color misregistration correction, the moving speed of the intermediate transfer belt 30 is set to vmm / s. Further, as an example, Y is a reference color, and among the correction images 400 and 401, the theoretical distances between Y, which is the reference color, and each image of M, C, and Bk are δdsM, δdsC, and δdsBk. . For example, the deviation amount δesM of M when Y is the reference color can be obtained from the following equation (1). Similarly, the deviation amount δesC of C when Y is the reference color is obtained by the following equation (2), and the deviation amount δesBk of Bk when Y is the reference color is obtained by the following equation (3). be able to. Here, dsM is an ideal interval between YM, dsC is an ideal interval between Y and C, and dsBk is an ideal interval between Y and Bk.
δesM = v × {(tsf2−tsf1) + (tsr2−tsr1)} / 2−dsM (1)
δesC = v × {(tsf3−tsf1) + (tsr3−tsr1)} / 2−dsC (2)
δesBk = v × {(tsf4-tsf1) + (tsr4-tsr1)} / 2-dsBk (3)
The control unit 54 changes the irradiation timing of the laser light 21 by the scanner unit 20 as an example of image forming conditions, for example, based on the deviation amount obtained by the above formulas (1) to (3). For example, if the amount of color misregistration in the sub-scanning direction is an amount for −4 lines, the control unit 54 controls the emission timing of the laser light 21 to be advanced by +4 lines. In this way, by performing color misregistration correction using an image for correction in S300, the color misregistration state is returned to the reference state, in other words, at least the color misregistration state approaches the reference state, thereby suppressing color misregistration. It can be in a state of being. Note that S301 is not necessarily performed, and can be skipped if color misregistration is already suppressed.

  In step S302, the control unit 54 sets the rotational phase relationship (rotational position relationship) between the photosensitive drums 22a to 22d to a predetermined value in order to suppress the influence when the rotational speed (peripheral surface speed) of the photosensitive drums 22a to 22d varies. Match the condition. Specifically, when the reference color is Y, the control unit 54 adjusts the phases of the photosensitive drums 22b to 22d of other colors with respect to the phase of the photosensitive drum 22a. When the drive gears are provided on the rotation shafts of the photosensitive drums 22a to 22d, the phase relationship of the drive gears of the photosensitive drums 22a to 22d is substantially adjusted. Then, when starting the process of S305, the control unit 54 waits until the rotational phase difference between the photosensitive drums 22a to 22d reaches a predetermined phase difference.

  In S303, the control unit 54 starts a timer. Next, in S304 to S307, the control unit 54 performs a loop process of i = 1 to 12 so that three patterns are formed as the electrostatic latent image 80 for correcting each color. In S305, the control unit 54 forms the electrostatic latent image 80 for correction by irradiating the laser light 21a with the scanner unit 20a. In step S <b> 306, the control unit 54 performs standby processing for a predetermined time based on the formation interval of the electrostatic latent image for correction. This is to prevent the detection results of the electrostatic latent images for correction formed in the respective colors from overlapping, and even if the assumed maximum deviation occurs, the electrostatic latent images for correction 80 do not overlap. Such a waiting time is set. Further, it is desirable that the standby processing time is less than the time for which the photosensitive drum rotates once.

[Formation of electrostatic latent image 80 for correction]
FIG. 4B is a diagram showing a state where the electrostatic latent image 80 for correction is formed on the yellow photosensitive drum 22a (on the photosensitive member). The electrostatic latent image 80 for correction is drawn as wide as possible in the image region width in the main scanning direction, and has a width of about 30 lines in the sub-scanning direction. In addition, the width in the main scanning direction is desirably formed with a width that is at least half of the maximum width in order to obtain a good detection result. In addition, the width of the electrostatic latent image 80 for correction is expanded to an area that further exceeds the paper area outside the image area (image area to be printed on paper) and an area where an electrostatic latent image can be formed. And more preferred.

  Next, the flowchart of FIG. 3B will be described. FIG. 3B also shows processing for yellow, but similar processing is performed for other colors. In S311 to S314, the control unit 54 performs a loop process of i = 1 to 24 in order to detect six edges of the pattern formed three by three as the electrostatic latent image 80 for correcting each color. In S312, the control unit 54 detects the edge detection timing ty (i) (i = 1 to 24) from the reference timing for the 12 electrostatic latent images 80 for correction formed in the flowchart of FIG. ) Is detected. The control unit 54 can determine that an edge has been detected when the output of the binarized voltage value 561 has changed. The reference timing here is the timing at which laser irradiation is started to form a plurality of electrostatic latent images 80 for correction. In S313, the control unit 54 temporarily stores the detected timing of the i-th edge in the RAM 323 as ty (i). Thus, by detecting a plurality of electrostatic latent images for correction 80, for example, by averaging a plurality of detection results, it is possible to suppress at least unevenness in the rotation cycle of the photosensitive drum 22a.

[Description of Change in Surface Potential of Photosensitive Drum by Electrostatic Latent Image 80 for Correction]
FIG. 5A shows an output related to the surface potential of the photosensitive drum 22a, which is output from the current detection circuit 50 when the electrostatic latent image 80 for correction reaches a position facing the charging roller 23a as the process means. The value is shown. In FIG. 5A, the vertical axis indicates the voltage 56 indicating the detected current change, and the horizontal axis indicates time. The waveform of FIG. 5A shows a characteristic that the voltage value becomes minimum when the electrostatic latent image for correction 80 reaches the charging roller 23a, and then returns.

  Here, the reason why the detected voltage value decreases will be described. FIG. 5B is a schematic diagram showing the surface potential of the photosensitive drum 22a. The horizontal axis indicates the surface position in the rotation direction of the photosensitive drum 22a, and the region 93 indicates the position where the electrostatic latent image 80 for correction is formed. The vertical axis indicates the potential, where the dark potential of the photosensitive drum 22a is VD (for example, -700V), the light potential is VL (for example, -100V), and the charging bias potential of the charging roller 23a is VC (for example, -1000V).

  In the region 93 where the electrostatic latent image 80 for correction is formed, the potential difference 96 between the charging roller 23a and the photosensitive drum 22a is larger than the potential difference 95 in other regions. For this reason, when the electrostatic latent image 80 for correction reaches the charging roller 23a, the value of the current flowing through the charging roller 23a increases. As the current increases, the voltage value at the output terminal of the operational amplifier 70 decreases. The above is the reason why the detected voltage value decreases. The detected current value reflects the surface potential of the photosensitive drum 22a. In FIG. 5, the difference between the surface potential of the photosensitive drum 22a and the output voltage of the charging roller 23a has been described as an example. However, the same applies to the change in the amount of current, the surface potential of the photosensitive drum 22a and the transfer voltage. It can be said between. That is, as the process means for detecting the electrostatic latent image 80 for correction, not only the charging roller 23a as the charging means but also the developing sleeve 24a as the developing means and the primary transfer roller 26a as the transfer means may be used. Is possible.

Next, the flowchart of FIG. 3C will be described. In step S321, the control unit 54 calculates the difference between the edge midpoints of the electrostatic latent image 80 for correction between the two colors using the following equations (4) to (6). The calculation method is not particularly limited, and the CPU 321 may perform the calculation based on the program code or may use a hardware circuit or a table.
δesYM = Σ {k = 1-3} {(tm (8k-1) + tm (8k)) / 2} -Σ {k = 1-3} {(ty (8k-7) + ty (8k-6)) / 2} (4)
δesYC = Σ {k = 1-3} {(tc (8k−3) + tc (8k−2)) / 2} −Σ {k = 1−3} {(ty (8k−7) + ty (8k−6) )) / 2} (5)
[delta] esYBk = [Sigma] {k = 1-3} {(tbk (8k-5) + tbk (8k-4)) / 2}-[Sigma] {k = 1-3} {(ty (8k-7) + ty (8k-6) ) / 2} (6)
That is, in S321, the control unit 54 calculates the deviation amount δesYM of the magenta in the sub-scanning direction when yellow is used as a reference from the measured values of ty (1) to ty (6) and tm (1) to tm (6). Calculate. Similarly, a deviation amount δesYC of cyan in the sub-scanning direction and a deviation amount δesYBk of black in the sub-scanning direction are calculated.

  In step S322, the control unit 54 stores δesYM, δesYC, and δesYBk calculated in step S321 in the EEPROM 324 as a reference value when performing positional deviation correction using the electrostatic latent image 80 for correction. When performing misalignment correction using the electrostatic latent image 80 for correction, the control unit 54 performs misalignment correction control so as to eliminate the detected misalignment using the stored reference value as a reference state. . In other words, misregistration correction control is performed so as to return the color misregistration state to the reference state, or at least bring the color misregistration state closer to the reference state.

[Flowchart of misregistration correction control using electrostatic latent image 80 for correction in this embodiment]
Next, a flowchart of misregistration correction control using the electrostatic latent image 80 for correction in this embodiment will be described with reference to FIG. The method for detecting the electrostatic latent image 80 for correction is the same as that in the flowchart of FIG. Below, it demonstrates centering around the difference with FIG.3 (c).

In S621, the control unit 54 is based on the following formulas (7) to (9) from the result of detecting the electrostatic latent image 80 for correction, similarly to the method of calculating δesYM, δesYC, and δesYBk in the previous S321. , DδesYM, dδesYC, and dδesYBk. The acronym “d” is a subscript indicating that the previous reference value is not a detection result at the time of measurement, but a detection result at the time of positional deviation correction under a predetermined condition.
dδesYM = Σ {k = 1-3} {(tm (8k−1) + tm (8k)) / 2} −Σ {k = 1-3} {(ty (8k−7) + ty (8k−6)) / 2} (7)
dδesYC = Σ {k = 1-3} {(tc (8k−3) + tc (8k−2)) / 2} −Σ {k = 1−3} {(ty (8k−7) + ty (8k−6) )) / 2} (8)
dδesYBk = Σ {k = 1-3} {(tbk (8k−5) + tbk (8k−4)) / 2} −Σ {k = 1−3} {(ty (8k−7) + ty (8k−6) ) / 2} (9)
In S622, the control unit 54 stores the dδesYM, dδesYC, and dδesYBk calculated in S621 in the RAM 323. In S623, the control unit 54 obtains a difference between dδesYM stored in S622 and δesYM stored in S322 by the following equation (10).
δY = dδesYM−δesYM (10)
When the result calculated by Expression (10) is 0 or more, that is, when the detection timing of magenta when yellow is used as a reference, the control unit 54 determines the emission timing of the magenta laser light 21b in S624. Speed up according to the result calculated by equation (10). On the other hand, when the result calculated by Expression (10) is less than 0, that is, when the detection timing of magenta when yellow is used as a reference, the control unit 54 emits the magenta laser light 21b in S625. The timing is delayed according to the result calculated by Equation (10). As a result, the misalignment of magenta can be corrected, and the color misalignment between yellow and magenta can be corrected.

In S626, the control unit 54 obtains the difference between dδesYC stored in S622 and δesYC stored in S322 by the following equation (11).
δC = dδesYC−δesYC (11)
When the result calculated by Expression (11) is 0 or more, that is, when the cyan detection timing is delayed from the reference when yellow is used as a reference, the control unit 54 determines the emission timing of the cyan laser light 21c in S627. The time is advanced according to the result calculated by equation (11). On the other hand, when the result calculated by Expression (11) is less than 0, that is, when the cyan detection timing is earlier than the reference when yellow is used as a reference, the control unit 54 emits the cyan laser light 21c in S628. The timing is delayed according to the result calculated by Expression (11). This makes it possible to correct cyan misregistration and to correct color misregistration between yellow and cyan.

In S629, the control unit 54 obtains the difference between dδesYBk stored in S622 and δesYBk stored in S322 by the following equation (12).
δBk = dδesYBk−δesYBk (12)
When the result calculated by Expression (12) is 0 or more, that is, when the black detection timing is delayed from the reference when yellow is used as a reference, the control unit 54 determines the emission timing of the black laser light 21d in S630. The time is advanced according to the result calculated by Expression (12). On the other hand, when the result calculated by Expression (12) is less than 0, that is, when the black detection timing when yellow is used as a reference is earlier than the reference, the control unit 54 emits the black laser beam 21d in S631. The timing is delayed according to the result calculated by Expression (12). This makes it possible to correct black misregistration and to correct color misregistration between yellow and black.

[Combination of misregistration correction control and discharge operation by correcting electrostatic latent image 80]
With reference to the timing chart of FIG. 7, a description will be given of the combined use of the positional deviation correction control by the electrostatic latent image 80 for correction and the ejection operation. The formation of the electrostatic latent image for correction 80 and the discharge operation are performed in parallel when the electrostatic latent image for correction 80 is formed when the reference value is acquired or when the electrostatic latent image for correction is formed under a predetermined condition. This is possible when forming the electrostatic latent image 80.

  FIG. 7 shows a case where the electrostatic latent image 80 for correction is formed when the reference value is acquired as an example. Timing Tb1 is the timing when the color misregistration correction using the correction image is completed. At timing Tb1, charging high voltage, primary transfer high voltage, and development high voltage are already applied, and the developing sleeve 24a is driven.

  First, a plurality of patterns are formed as electrostatic latent images 80 for correction at intervals of about one third of the photosensitive drums 22 at predetermined intervals in the photosensitive drums 22a to 22d of the respective colors in the period of timings Tb1 to Tb3. In FIG. 7, 81YL, 81ML, 81CL, 81KL, 82YL, 82ML, 82CL, 82KL, 83YL, 83ML, 83CL, and 83KL indicate a plurality of patterns. The plurality of patterns formed on the photosensitive drums 22a to 22d are developed as toner images by the developing sleeves 24a to 24d. In FIG. 7, 81YD, 81MD, 81CD, 81KD, 82YD, 82MD, 82CD, 82KD, 83YD, 83MD, 83CD, and 83KD represent a plurality of toner images obtained by developing a plurality of patterns.

  The developed toner images pass through the primary transfer unit in each image forming unit. At this time, the primary transfer bias applied to each of the primary transfer rollers 26a to 26d is set to the same polarity as the toner polarity at the time of development so that the toner image is not transferred to the intermediate transfer belt 30. In FIG. 7, 81YT1N, 81MT1N, 81CT1N, 81KT1N, 82YT1N, 82MT1N, 82CT1N, 82KT1N, 83YT1N, 83MT1N, 83CT1N, and 83KT1N indicate the application timing of the primary transfer bias. The adjustment of the primary transfer bias is an example. For example, when the developed toner image passes through the primary transfer portion, the primary transfer rollers 26a to 26d are separated and the toner image is applied to the intermediate transfer belt 30. May not be transferred.

  A plurality of toner images remaining on the photosensitive drums 22a to 22d without being primarily transferred are conveyed to cleaning blades 28a to 28d (hereinafter also referred to as C blades) and removed by the cleaning blades 28a to 28d. The In FIG. 7, 81YS, 81MS, 81CS, 81KS, 82YS, 82MS, 82CS, 82KS, 83YS, 83MS, 83CS, and 83KS indicate the timing at which the plurality of toner images reach the cleaning blades 28a to 28d. The removed toner serves as a lubricant between the cleaning blades 28a to 28d and the photosensitive drums 22a to 22d, and the effect of suppressing the turning of the cleaning blades 28a to 28d is obtained.

  After the toner image is cleaned, the position where the toner image is formed is moved to a position facing the charging rollers 23a to 23d. At this time, since there is a potential difference between the position where the toner image is formed and other positions, the current detection circuits 50a to 50d can detect that the current value flowing through the charging rollers 23a to 23d changes. . This change in current value corresponds to the detection voltage 561 described above. FIG. 7 shows a change in current detection between timings Tb2 to Tb4. 81A to 81D are results of detecting changes in current due to the electrostatic latent images formed by the laser signals 81YL, 81ML, 81CL, and 81KL. Similarly, 82A to 82D are detection results of laser signals 82YL, 82ML, 82CL, and 82KL, and 83A to 83D are detection results of laser signals 83YL, 83ML, 83CL, and 83KL. When current detection is performed in the period of timing Tb2 to Tb4, the position of the electrostatic latent image for correction 80 can be detected by the control unit 54 based on the detection result as described above, and the electrostatic latent image for correction is corrected. Misalignment correction control using 80 can be performed.

  As described above, in this embodiment, as the calibration operation, the positional deviation correction control using the correction electrostatic latent image 80 and the discharge operation for supplying the toner to the cleaning blade can be performed simultaneously. Thereby, the time required for calibration can be suppressed.

(Second Embodiment)
In the present embodiment, the positional deviation correction control using the electrostatic latent image 80 for correction and the density control of the toner image to be developed when performing the discharge operation for supplying the toner to the cleaning blade at the same time will be described. To do. The positional deviation correction control using the electrostatic latent image 80 for correction and the discharge operation for supplying toner to the cleaning blade are the same as those in the first embodiment, and will be described here. Is omitted. In this embodiment, the density control of the toner image to be developed will be described.

[Conditions for Simultaneously Performing Misalignment Correction Control Using Correction Electrostatic Latent Image 80 and Discharge Operation for Supplying Toner to Cleaning Blade]
In the present embodiment, the discharge operation is executed in order to prevent the cleaning blade from being turned over due to the printing rate of the image to be formed or the printing frequency of the low printing rate image. Specifically, the value is counted when an image having a printing rate equal to or less than a predetermined value is formed by a counting unit that counts a value corresponding to information relating to the printing rate of the formed image. When the accumulated value of the counted values exceeds a predetermined value, the discharge operation is executed. As a value to be counted, for example, when an image having a printing rate of 0.5 to 1.0% is formed, the value is increased by 1. When an image having a printing rate of less than 0.5% is formed, the value is increased by 2. When an image of 5% or more is formed, the value is decreased by 1. Then, when the accumulated value exceeds 100, control is performed so as to execute the discharge operation.

[Combination of misregistration correction control and discharge operation by correcting electrostatic latent image 80]
In the present embodiment, based on the cumulative value counted according to the printing rate of the image to be formed, the misalignment correction control by the correcting electrostatic latent image 80 and the discharge operation are executed simultaneously. In this case, a method for controlling the amount of toner to be loaded when developing the electrostatic latent image for correction 80 in order to suppress toner consumption and increase in downtime will be described with reference to FIG.

  In this embodiment, the density of the toner image to be developed is controlled according to the accumulated value when it is determined that the toner discharge operation is executed. As shown in FIG. 8A, as the cumulative value is larger, the toner amount when developing the electrostatic latent image for correction 80 is increased. This is because the larger the accumulated value counted, the more images with a low printing rate were formed, and it is considered that the amount of toner supplied to the cleaning blade is reduced. Therefore, when the cumulative value is large, the density of the toner image is increased so that a large amount of toner is supplied to the cleaning blade. After executing the toner discharge, the accumulated value is set to zero. Then, counting is performed again. In the present embodiment, the amount of toner to be developed is constant within a certain range of cumulative values, but the present invention is not necessarily limited to this relationship. The relationship between the accumulated value and the toner amount can be set as appropriate, for example, by estimating an appropriate toner amount in advance through experiments and determining the toner amount for each accumulated value.

  In this embodiment, the toner amount is adjusted by changing the developing bias in accordance with the accumulated value as shown in FIG. When the cumulative value increases, the developing bias is also increased, and control is performed to increase the amount of toner during development. When the accumulated value is 0 to 20, the developing bias may be set to 0 V (OFF) so that the ejection operation is not performed. The toner amount may be controlled by changing the developing bias while keeping the charging potential of the photosensitive drum and the exposure amount of the scanner unit constant, or changing the exposure amount while keeping the developing bias constant. You may adjust with. Further, even when the toner amount is maximized (here, the toner amount corresponding to the accumulated value 100 is 8 mg), the toner amount necessary for suppressing the turning of the cleaning blade may not be reached. In such a case, the number of toner images to be formed may be increased to increase the amount of toner supplied to the cleaning blade.

  As described above, by appropriately controlling the amount of toner used for the ejection operation in accordance with the image forming status, it is possible to supply an appropriate amount of toner in accordance with the status of the cleaning blade. In addition, by supplying an appropriate amount of toner, it is possible to suppress toner consumption and suppress an increase in downtime.

20a to 20d Scanner unit 22a to 22d Photosensitive drum 24a to 24d Developing sleeve 28a to 28d Cleaning blade 50a to 50d Current detection circuit 80 Electrostatic latent image for correction

Claims (12)

A photoreceptor,
Light irradiating means for forming a correcting electrostatic latent image on the photosensitive member by irradiating light;
Developing means for developing the electrostatic latent image for correction as a toner image;
Cleaning means for cleaning the toner image on the photoreceptor;
Detecting means for detecting an electrostatic latent image for correction formed on the photoreceptor;
Control means for controlling a condition for forming an electrostatic latent image at the time of image formation based on a detection result detected by the detection means,
The control means forms the electrostatic latent image for correction, and develops the electrostatic latent image for correction as a toner image, thereby forming a condition for forming the electrostatic latent image during the image formation. And an operation for supplying toner to the cleaning unit in parallel. Comprising a counting means for counting a value according to information on the printing rate of the formed image;
The image forming apparatus according to claim 1, wherein the control unit controls a toner amount of the toner image according to an accumulated value counted by the counting unit. The counting means increases the cumulative value if the printing rate of the formed image is lower than a predetermined printing rate,
The control unit forms a toner image having a first toner amount in accordance with a first cumulative value, and has a first toner amount larger than the first toner amount in accordance with a second cumulative value larger than the first cumulative value. The image forming apparatus according to claim 2, wherein a toner image having a toner amount of 2 is formed.   4. The control unit according to claim 2, wherein the control unit controls the toner amount by controlling a light amount irradiated from the light irradiation unit or a developing bias applied to the developing unit. Image forming apparatus. Charging means for charging the photoreceptor;
Transfer means for transferring a toner image formed on the photoconductor,
The detecting means detects an output value when the electrostatic latent image for correction passes through a position facing the charging means, or detects a position where the electrostatic latent image for correction faces the developing means. 5. The output value when the passage is detected, or the output value when the electrostatic latent image for correction passes through a position facing the transfer unit is detected. 6. 2. The image forming apparatus according to item 1. Power supply means for supplying power to the charging means,
6. The image forming apparatus according to claim 5, wherein the detection unit detects an output of the power source unit when the electrostatic latent image for correction passes a position facing the charging unit. Power supply means for supplying power to the developing means,
The image forming apparatus according to claim 5, wherein the detection unit detects an output of the power source unit when the electrostatic latent image for correction passes a position facing the developing unit. Power supply means for supplying power to the transfer means,
The image forming apparatus according to claim 5, wherein the detection unit detects an output of the power source unit when the electrostatic latent image for correction passes through a position facing the transfer unit.   The control means corrects conditions for forming an electrostatic latent image at the time of image formation so that the state in which the electrostatic latent image for correction is detected by the detection means approaches at least a reference state. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The control unit corrects a condition for forming an electrostatic latent image at the time of image formation so that a state in which the electrostatic latent image for correction is detected by the detection unit returns to a reference state. The image forming apparatus according to any one of claims 1 to 8. The light irradiation means forms a first electrostatic latent image for correction at a plurality of positions on the photoconductor,
The detecting means detects an output corresponding to each of the first electrostatic latent images for correction formed at the plurality of positions;
The control means stores the detection result of the first correction electrostatic latent image in a storage means,
The light irradiation unit forms second electrostatic latent images for correction under a predetermined condition at a plurality of positions of the photoconductor,
The detecting means detects an output corresponding to each of the second correction electrostatic latent images formed at the plurality of positions;
The control means is configured to generate a static image during image formation based on the detection result of the first correction electrostatic latent image stored in the storage means and the detection result of the second correction electrostatic latent image. The image forming apparatus according to claim 1, wherein conditions for forming an electrostatic latent image are corrected. A plurality of the photoreceptors;
12. The control unit according to claim 1, wherein the control unit corrects a color misregistration between a plurality of photosensitive members by correcting a condition for forming an electrostatic latent image at the time of image formation. 2. The image forming apparatus according to item 1.

Images