JP6087254B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method, and more particularly, to an image forming apparatus and an image forming method capable of maintaining a stable image quality by changing a toner replenishment amount based on laser power.

  Conventionally, in an image forming apparatus, in order to adjust the image formation (printing) image quality, a reference image pattern serving as a reference is developed on an image carrier, the density is read by a density center, and the reference image pattern is read. Based on the image forming conditions to be formed and the density of the reference image pattern, the image forming conditions are corrected to stabilize the image.

  JP-A-8-202092 (Patent Document 1) discloses a solid patch image output means for outputting a solid patch image before digital image formation, a detection means for optically detecting an image on the image carrier, A digital image forming apparatus comprising a peripheral speed ratio variable setting means for variably setting the peripheral speed ratio of the developer carrying carrier to the image carrier during digital image formation based on the signal output value of the detection means. ing. In this digital image forming apparatus, a halftone patch image output means for outputting a halftone patch image at the set peripheral speed ratio at the time of digital image formation, and a signal from the detection means when detecting on the image carrier A halftone control means for variably controlling at least one of the charging potential on the image carrier and the power of the laser for writing so that the density of the halftone patch image becomes a desired density based on the output value. Yes. That is, in this digital image forming apparatus, in order to adjust the halftone density of image formation, the reference potential pattern is set to the halftone and the charging potential or the laser power is adjusted. As a result, the image density of the entire region from the halftone image to the solid image can be adjusted.

  In the touch-down development method or the hybrid development method, the high density (100% density, solid patch density) of the reference image pattern is adjusted by adjusting the toner layer thickness of the toner carrier, and the halftone density is obtained by charging potential or laser power. By adjustment, it can be varied independently. The touch-down development method is a magnetic brush provided on a development carrier carrying a two-component developer, and a toner layer thickness is formed on the toner carrier, and depending on the toner layer thickness on the toner carrier. This means an image forming system for developing and visualizing an electrostatic latent image on an image carrier. The hybrid development system means an image forming system in which toner is charged by mixing friction with a carrier, and conveyance to the development area is performed by thinning the toner on a developing carrier.

Japanese Patent Laid-Open No. 8-202092

  However, in an image forming apparatus using a two-component developer, toner charging in image formation is caused by noise such as fluctuations in the toner density of the developer in the developer container, environmental fluctuations such as temperature and humidity fluctuations, and deterioration of the developer. The amount varies greatly. Therefore, as described above, there is a problem that the image quality cannot be maintained only by correcting the charging potential and the laver power. Therefore, the technique described in Patent Document 1 cannot solve the above problem. In this specification, the term “toner density” is used for both the meaning of the toner density in the developing device and the meaning of the image density within a range where the meaning is not obscured.

  Therefore, the present invention has been made to solve the above problems, and provides an image forming apparatus and an image forming method capable of maintaining a stable image quality by changing a toner replenishment amount based on laser power. The purpose is to provide.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention is an image forming apparatus capable of performing light quantity calibration, which forms an image with a two-component developer, and has the following configuration. adopt.

  That is, the present invention forms a halftone patch having a preset reference density with a preset reference laser power, measures the density of the halftone patch, and measures the measured density and the reference density. Light amount calibration execution means for correcting the laser power based on the reference laser power, and the corrected correction laser power and reference laser power after the correction, or the measured density and the reference density of the halftone patch, the developing container And a toner replenishing means for adjusting the toner replenishment amount.

  The toner replenishing means calculates a change amount obtained by subtracting the reference laser power from the correction laser power, and the change amount corresponds to a graph in which the toner replenishment amount decreases as the laser power increases. The amount of change in the toner replenishment amount is calculated backward, and the amount of change is added to the reference toner replenishment amount corresponding to the reference laser power to obtain the corrected toner replenishment amount.

  The toner replenishing means calculates a change amount obtained by subtracting the reference density from the measured density of the halftone patch, and the toner replenishment amount increases as the density of the halftone patch increases. Accordingly, the amount of change in the toner replenishment amount is calculated backward, and the amount of change is added to the reference toner replenishment amount corresponding to the reference density to obtain the corrected toner replenishment amount.

  Further, the toner replenishing means is configured to provide a target of the toner density sensor based on the correction laser power and the reference laser power, or the measured density and the reference density of the halftone patch when the toner density sensor exists in the developing container. The toner supply amount is adjusted by changing the value.

  In addition, the present invention can be provided as an image forming method for an image forming apparatus capable of performing light quantity calibration in which an image is formed with a two-component developer.

  That is, the present invention forms a halftone patch having a preset reference density with a preset reference laser power, measures the density of the halftone patch, and measures the measured density and the reference density. Correcting the laser power based on the reference laser power, and supplying toner to the developing container based on the corrected laser power and reference laser power after correction, or the measured density and reference density of the halftone patch Adjusting the amount. Even with such a configuration, the same effects as described above can be obtained.

  Further, the present invention can be provided as a program for causing a computer to circulate individually via a telecommunication line or the like. In this case, the central processing unit (CPU) realizes the control operation in cooperation with each circuit other than the CPU according to the program of the present invention. Each means realized by using the program and the CPU can also be configured by using dedicated hardware. The program can also be distributed in a state where it is recorded on a computer-readable recording medium such as a CD-ROM.

  According to the image forming apparatus and the image forming method of the present invention, it is possible to maintain a stable image quality by changing the toner replenishment amount based on the laser power.

1 is a schematic configuration diagram of an image forming apparatus according to an exemplary embodiment. FIG. 3 is a detailed view of one image forming unit. 2 is a schematic configuration diagram relating to control of the image forming apparatus 1 in the present embodiment. FIG. 1 is a functional block diagram of an image forming apparatus of the present invention. It is a flowchart for showing the execution procedure of this invention. FIG. 6 is a diagram (FIG. 6A) showing an example of a halftone patch on an intermediate transfer belt according to the present invention, and a density / laser power graph according to the present invention (FIG. 6B). FIG. 7 is a density / toner supply amount graph according to the present invention (FIG. 7A) and a density / toner supply amount graph according to the present invention (FIG. 7B).

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not. Moreover, the alphabet S added before the number in a flowchart means a step.

<Image forming apparatus>
The image forming apparatus 1 according to the present invention will be described below. FIG. 1 is a schematic configuration diagram of an image forming apparatus 1 of the present embodiment.

  The image forming apparatus 1 transfers a toner image formed by the tandem-type image forming unit A1 that forms a toner image based on image data, a paper storage unit 2 that stores paper, and the image forming unit A1 onto the paper. A next transfer unit 3 is provided. The image forming apparatus further includes a fixing unit 4 that fixes the transferred toner image on the paper, a paper discharge device 5 that discharges the fixed paper, and a paper discharge tray 7 that receives the discharged paper. Further, the image forming apparatus 1 includes a paper transport unit 6 that transports paper from the paper storage unit 2 to the paper discharge device 5.

  The image forming unit A1 includes an intermediate transfer belt B1 (intermediate transfer member), a cleaning unit B2 for cleaning the intermediate transfer belt B1, and each color of yellow (Y), magenta (M), cyan (C), and black (B). Are provided with image forming units FY, FM, FC, and FB, respectively.

  The intermediate transfer belt B1 is a belt-like member having an endless shape, that is, a loop shape, which is wider than a sheet having the maximum length in the direction perpendicular to the usable sheet conveying direction and having conductivity. Circulated around.

  The image forming units FY, FM, FC, and FB are arranged in this order along the intermediate transfer belt B1 in the moving direction of the intermediate transfer belt B1, downstream from the cleaning unit B2 and upstream from the secondary transfer unit 3. . Note that the order of arrangement of the image forming units FY, FM, FC, and FB is not limited to this, but this arrangement is preferable in consideration of the influence of the color mixture on the completed image. The image forming units FY, FM, FC, and FB are arranged so that the intervals between the image forming units are equal.

  Next, an image forming operation of the image forming apparatus 1 will be described. FIG. 2 is a detailed view of one of the image forming units FY, FM, FC, and FB. The image forming units FY, FM, FC, and FB have almost the same configuration.

  The image forming unit FY includes a photosensitive drum (image carrier) 10, a charger 11, an LED exposure device 12, a yellow developing device HY, a primary transfer roller (voltage applying unit) 20, and a cleaning blade 35 for the photosensitive drum 10. , A static elimination device 13 and a carrier removal roller (carrier removal member) 30.

  The other image forming units FM, FC, and FB include developing devices HM, HC, and HB corresponding to the respective colors. Of the image forming units, the image forming unit FB located on the most downstream side in the moving direction of the intermediate transfer belt B1 is not provided with the carrier removing roller 30 because the image forming unit is not located downstream thereof. Other configurations are the same.

  The photoreceptor drum 10 only needs to be able to carry a toner image including toner charged on its surface (charged positively in this embodiment).

  In the present embodiment, the photosensitive drum 10 is a substantially cylindrical member that is arranged to be rotatable about a rotation axis that is perpendicular to the moving direction of the intermediate transfer belt B1 and parallel to the surface direction of the intermediate transfer belt B1. The photosensitive drum 10 is in contact with the surface of the intermediate transfer belt B1 at a predetermined primary transfer position 10S. The photosensitive drum 10 can rotate so that the moving direction at the primary transfer position 10S is the same as the moving direction of the intermediate transfer belt B1, that is, in FIG.

  The cleaning blade 35, the charge eliminating device 13, the charger 11, the exposure device 12, and the yellow developing device HY are arranged around the photosensitive drum 10 in this order as seen from the primary transfer position along the rotation direction described above. The

  The charger 11 can uniformly charge the surface of the photosensitive drum 10. The exposure device 12 has a light source such as an LED, and irradiates the charged surface of the photosensitive drum 10 with light corresponding to the image data in accordance with the image data from the above-described host device, so that the surface of the photosensitive drum 10 is statically exposed. An electrostatic latent image can be formed.

  The yellow developing device HY holds a developer containing yellow toner and a carrier so as to face the electrostatic latent image, thereby applying toner to the electrostatic latent image, and converting the electrostatic latent image into a toner image. Can be developed. This toner image is primarily transferred by the primary transfer roller 20 to the intermediate transfer belt B1. Details of the primary transfer roller 20 will be described later.

  The cleaning blade 35 is a blade-like member disposed so as to be in contact with the photosensitive drum 10. The cleaning blade 35 removes the developer remaining on the surface of the photosensitive drum 10 after the primary transfer.

  The neutralization device 13 includes a light source. After the developer is removed by the cleaning blade 35, the surface of the photosensitive drum 10 is neutralized by light from the light source to prepare for the next image formation.

  The primary transfer roller 20 is disposed so as to contact the back surface of the intermediate transfer belt B1 at a voltage application position 20S downstream from the primary transfer position 10S in the moving direction of the intermediate transfer belt B1. A voltage having a polarity opposite to that of the toner in the toner image (minus in this embodiment) is applied to the primary transfer roller 20 from a power source (not shown). That is, the primary transfer roller 20 can apply a voltage having a polarity opposite to that of the toner to the intermediate transfer belt B1 at the voltage application position 20S. Since the intermediate transfer belt B1 has conductivity, the applied voltage attracts toner to the surface side of the intermediate transfer belt B1 at the voltage application position 20S and the periphery thereof.

  Therefore, in the present embodiment, the primary transfer position 10S is disposed within a range in which toner is attracted to the intermediate transfer belt B1 side by the applied voltage. As a result, the toner moves from the photosensitive drum 10 to the surface of the intermediate transfer belt B1, and primary transfer is performed.

  As long as primary transfer is possible in this way, the specific configuration of the primary transfer roller 20 is not particularly limited, and the specific configuration can be changed as appropriate. In the present embodiment, the primary transfer roller 20 can rotate in the opposite direction to the photosensitive drum 10 around a rotation axis parallel to the rotation axis of the photosensitive drum 10, that is, the movement direction at the charge application position 20S is intermediate. It is a substantially cylindrical member that can be rotated in the same direction as the transfer belt B1.

  In this embodiment, the carrier removal roller 30 is a substantially cylindrical member that can rotate in the same direction as the photosensitive drum 10 around a rotational axis parallel to the rotational axis of the photosensitive drum 10. The carrier is not limited, and it is sufficient that the carrier can be removed from the surface of the intermediate transfer belt B1 downstream of the charge application position 20S and upstream of the secondary transfer position in the moving direction of the intermediate transfer belt B1. Specifically, the carrier removing roller 30 only needs to be able to move the carrier on the surface of the intermediate transfer belt B1 to its own surface by contacting the surface of the intermediate transfer belt B1.

  During primary transfer, a small amount of carrier may be transferred from the photosensitive drum 10 to the intermediate transfer belt B1 together with the toner. This carrier transfer may interfere with primary transfer in the downstream image forming unit and cause image defects such as image blurring and blurring. Providing the carrier removal roller 30 can prevent such an image defect.

  In the present embodiment, the carrier removal roller 30 is disposed so as to contact the surface of the intermediate transfer belt B1 downstream of the charge application position 20S in the moving direction of the intermediate transfer belt B1. The carrier removal roller 30 is incorporated in the cleaning unit 31 together with the cleaning blade 35 described above. The cleaning unit 31 is provided in the image forming unit FY. In addition to the cleaning blade 35 and the carrier removing roller 30, the cleaning unit 31 is in contact with the surface of the carrier removing roller 30 to remove the carrier attached to the surface of the carrier removing roller 30. The carrier removal blade 31b, the carrier removed from the carrier removal roller 30, and the developer (including toner and carrier) removed from the surface of the photosensitive drum 10 by the cleaning blade 35 are conveyed to the outside of the cleaning unit 31. A transport member 31c is provided. The image forming unit FY may further include a separation unit that separates the carrier and the toner in order to reuse the carrier and the toner conveyed by the conveyance member 31c.

  Next, the configuration of the developing device HY will be described. The configurations of the developing devices HY, HM, HC, and HB for the respective colors are the same.

  The developing device HY includes a developing container 40, a developing roller 40a, a magnetic roller (mag roller) 40b, a drawing roller 40c, stirring spirals 40d and 40e, a cleaning blade 45, and a magnetic roller doctor blade 40g.

  The developing container 40 stores therein a developer composed of yellow toner (toner particles) and a carrier. The stirring spirals 40d and 40e are provided so as to be entirely immersed in the developer in the developing container 40, and stir the developer. The toner is uniformly dispersed in the carrier by the rotation of the stirring spirals 40d and 40e.

  The drawing-up roller 40c is arranged so that a part of the drawing-up roller 40c is immersed in the developer in the developing container, and the developer is pumped up by adhering to the surface. A magnetic roller 40b is arranged in contact with the pumping roller 40c, and a developer is supplied from the pumping roller 40c. The magnetic roller 40b rotates in the counter direction of the developing roller 40a, and in the vicinity of the nip, a magnetic roller doctor blade 40g is provided that simultaneously peels off the developer and places the developer. The magnetic roller doctor blade 40g regulates the developer layer thickness on the surface of the magnetic roller 40b to a predetermined amount. A developing roller 40a (also referred to as a developing device) is disposed so as to be in contact with the magnetic roller 40b, and toner is applied to the surface thereof from the magnetic roller 40b. Since the developer layer thickness of the magnetic roller 40b is regulated to a predetermined value, the toner layer thickness formed on the surface of the developing roller 40a is also kept at the predetermined value. The developing roller 40a is in contact with the photosensitive drum 10, and responds to an image instructed to be formed from the host apparatus by the potential difference between the electrostatic latent image on the surface of the photosensitive drum 10 and the developing bias value applied to the developing roller 40a. A toner image is formed on the surface of the photosensitive drum 10 (development operation).

  The image forming apparatus of the present invention is characterized in that image density correction of a toner image is performed by adjusting a developing bias value (voltage value, simply referred to as a bias value) applied to the developing roller 40a.

  Further, the toner on the surface of the developing roller 40a that has completed the developing operation on the photosensitive drum 10 is collected by the magnetic brush and the AC bias on the magnetic roller 40b.

  Further, a toner concentration sensor 40h is arranged in the developing container, and detects the toner concentration of the developer in the developing container 40. When it is detected that the toner concentration is lower than the target value, toner (developer having a toner concentration higher than the target value) is supplied from a toner cartridge (not shown) to the developing container 40, and the toner concentration is higher than the target value. The carrier is supplied to the toner container 40 from a carrier cartridge (not shown).

  Under such a configuration, the image forming apparatus 1 that has received an instruction for image formation from a host device such as a personal computer (PC) or the like forms toner images of each color corresponding to the received image data in the image forming units FY, FM. , FC, and FB. The toner image formed in each image forming unit is transferred to the intermediate transfer belt B1, and is superimposed on the intermediate transfer belt B1 to form a color toner image.

  In synchronism with the formation of the color toner image, the paper stored in the paper storage unit 2 is taken out from the paper storage unit 2 one by one by a paper feeding device (not shown) and transported on the paper transport unit 6. Then, the sheet is fed to the secondary transfer unit 3 in synchronization with the primary transfer to the intermediate transfer belt B1, and the color toner image on the intermediate transfer belt B1 is secondarily transferred to the sheet by the secondary transfer unit 3. The sheet on which the color toner image has been transferred is further conveyed to the fixing unit 4 where the color toner image is fixed on the sheet by heat and pressure. Further, the paper is discharged by a paper discharge device 5 to a paper discharge tray section 7 provided on the outer periphery of the image forming apparatus 1. The toner remaining on the intermediate transfer belt B1 after the secondary transfer is removed from the intermediate transfer belt B1 by the cleaning unit B2.

  Further, two density detection sensors 605 and 606 for detecting the patch density of the patch formed on the intermediate transfer belt B1 and the background density of the intermediate transfer belt B1 at a predetermined timing are provided with the black image forming unit FB and the secondary. It is provided at a predetermined position between the transfer unit 3. The black image forming unit FB is located on the most downstream side with respect to the rotation direction of the intermediate transfer belt B1 as compared with the other image forming units FY, FM, and FC. Therefore, the density detection sensors 605 and 606 detect the patch density of any one of the plurality of image forming units FY, FM, FC, and FB even if the patch is formed on the intermediate transfer belt B1. It is configured to be able to.

  Further, the density detection sensors 605 and 606 are provided in advance at positions corresponding to the positions of the intermediate transfer belt B1 where the patches are formed. In the embodiment of the present invention, two density detection sensors 605 and 606 are provided near both ends of the intermediate transfer belt B1. Provided. The density detection sensors 605 and 606 may be in any form as long as they can detect the patch density or background density of the patch for each color. For example, based on the provisions of the ISO 5 series, patches or intermediate transfer Reflection type density detection sensors 605 and 606 that irradiate the background on the belt B1 with light from the light source, detect the reflected light intensity with the light receiving sensor, and convert the light intensity information into the density.

  The density detection sensors 605 and 606 are also used for detecting the toner density of a solid band image to be described later.

  FIG. 3 is a schematic configuration diagram relating to control of the image forming apparatus 1 in the present embodiment.

  The image forming apparatus 1 includes a CPU (Central Processing Unit) 301, a RAM (Random Access Memory) 302, a ROM (Read Only Memory) 303, a HDD (Hard Disk Drive) 304, and a driver 305 corresponding to each driving unit in the printing. They are connected via an internal bus 306. The CPU 301 uses, for example, the RAM 302 as a work area, executes a program stored in the ROM 303, the HDD 304, or the like, and exchanges data and commands with the driver 305 based on the execution result, as shown in FIG. The operation of each driving unit is controlled. Also, each means (shown in FIG. 4) described later other than the drive unit operates as each means when the CPU 301 executes a program.

<Embodiment of the present invention>
Next, the configuration and execution procedure according to the embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is a functional block diagram of the image forming apparatus of the present invention. FIG. 5 is a flowchart for showing the execution procedure of the present invention.

  First, when the user turns on the power to the image forming apparatus 1, the image forming apparatus 1 is activated, and the control unit 401 of the image forming apparatus 1 determines whether or not to execute light amount calibration (FIG. 5: S101).

  Any method may be used as the method by which the control unit 401 determines whether to execute the light amount calibration. For example, there is a method in which the control unit 401 determines whether or not the current time is a specific time.

  Specifically, when the control unit 401 powers on the image forming apparatus 1 at the current time, when the current time prints a predetermined number of sheets (when the number of printed sheets exceeds a predetermined threshold), the current time indicates a print image. A method of determining whether a predetermined amount of toner is consumed by a dot count (when a toner consumption amount exceeds a predetermined threshold) or a predetermined calibration is performed is employed. .

  Here, since the image forming apparatus 1 is activated earlier, the control unit 401 determines to execute the light amount calibration (FIG. 5: S101 YES), and notifies the light amount calibration execution unit 402 to that effect. Receiving the notification, the light quantity calibration execution unit 402 uses a preset reference laser power LP (V) and a preset reference density CDT (−) (for example, a CDT value corresponding to a density of 25%). A halftone patch (also referred to as a half patch) is formed, the density of the halftone patch is measured, and the measured density CDTm (−), the reference density CDT (−), and the reference laser power LP (V) are measured. Based on the above, the laser power is corrected (determined).

  Specifically, the light quantity calibration execution unit 402 applies a preset developing bias (V) for printing to the magnetic roller 40a to attach toner, and the magnetic roller doctor blade 40g The deposited developer is set to a predetermined layer thickness (ΔV) (FIG. 5: S102).

  The light amount calibration execution unit 402 applies a preset charging potential (V) to the photosensitive drum 10 by using the charger 11 to uniformly charge the surface of the photosensitive drum 10. .

  The light quantity calibration execution unit 402 refers to a halftone patch image stored in advance in a predetermined memory and also refers to a halftone laser power (V) for forming a halftone patch image (FIG. 5). : S103).

  Here, the halftone patch images are two patch images corresponding to the positions of the two density detection sensors 605 and 606 of the intermediate transfer belt B1, for example, the same position in the rotation direction of the intermediate transfer belt B1. In the direction perpendicular to the rotation direction of the intermediate transfer belt B1, the front and rear positions are different. The halftone laser power (V) is a laser power LP (V) that is an absolute value of a quarter, which is four steps lower than the upper limit value of the laser power used when forming a solid patch image. . As a result, it is possible to form a halftone patch having a density that is a quarter of the density of the solid patch image.

  The light amount calibration execution unit 402 irradiates the surface of the charged photosensitive drum 10 with light corresponding to the halftone patch image by the exposure device 12 based on the halftone patch image and the halftone laser power. Then, an electrostatic latent image corresponding to the halftone patch image is formed on the surface of the photosensitive drum 10.

  Further, the light quantity calibration execution unit 402 matches the electrostatic latent image on the surface of the photosensitive drum 10 with the toner having a predetermined layer thickness (ΔV) on the surface of the magnetic roller 40a. The electrostatic latent image is developed as a toner image. Then, the light quantity calibration execution unit 402 primarily transfers the toner image to the intermediate transfer belt B1 via the primary transfer roller 20 (FIG. 5: S104).

  The light quantity calibration execution unit 402 activates the two density detection sensors 605 and 606 installed on the intermediate transfer belt B1, and forms them on the intermediate transfer belt B1 as shown in FIG. The densities CTD1 (−) and CTD2 (−) of the two halftone patches 600 and 601 are measured (FIG. 5: S105). Here, the two density detection sensors 605 and 606 are CTD (Color Toner Density) sensors, and the output value is a CTD value (−).

  Now, when the light intensity calibration execution unit 402 completes the measurement of the densities CTD1 (−) and CTD2 (−) of the two halftone patches 600 and 601, the average value CTDm (−) of both is calculated and the measurement is performed. A density / laser power graph is generated using the measured density CTDm (−) of the halftone patch and the halftone reference laser power LP (V) used.

  As shown in FIG. 6B, the generated density / laser power graph 602 is a linear graph in which the density of a halftone patch increases as the laser power increases. The measured density CTDm (−) of the measured halftone patch is associated with the used reference laser power LP (V).

  Here, ideally, the measured density CTDm (−) of the halftone patches 600 and 601 formed by the reference laser power LP (V) is the reference density CTD of the halftone patch whose density is ¼. It should be consistent with (-).

  However, for example, when the charge amount of the toner inside the image forming apparatus 1 increases, the flying property of the toner in the magnetic roller 40a to the surface of the photosensitive drum 10 becomes higher with the increase of the charge amount, so that it is easily developed. It becomes. In other words, the density of a halftone image should be adjustable by adjusting the laser power. However, when the laser power is constant, if the toner charge amount is high, the image density increases. Thus, when the charge amount of the toner is low, the density of the image is low. Then, even if the density of the halftone patch is adjusted based on the laser power, it varies depending on the toner charge amount.

  In the case of a solid density patch, if the charge amount of the toner increases, the developability deteriorates, and the reverse phenomenon occurs. This is thought to be because toner with a high charge amount can compensate for the potential difference of the electrostatic latent image with a small amount.

  Therefore, the light amount calibration execution unit 402 executes light amount calibration using the density / laser power graph 602.

  Specifically, a density / laser power graph in which the light intensity calibration execution unit 402 associates the measured density CTDm (−) of the halftone patch with the reference laser power LP (V), which is generated earlier. From 602, the laser power LPm (V) that is the reference density CTD (−) of the halftone patch is calculated backward.

  In FIG. 6B, the reference density CTD (−) of the reference halftone patch is lower than the measured density CTDm (−) of the measured halftone patch, that is, the charge amount of the toner is high. The laser power LPm (V) calculated backward is lower by 20% than the reference laser power LP (V) used.

  The light quantity calibration execution unit 402 uses the corrected laser power LPm (V) to form a halftone patch of the reference density CTD (−) (the density is ¼). (FIG. 5: S106), and notifies the control unit 401 accordingly. Upon receiving the notification, the control unit 401 executes image formation based on the corrected laser power LPm (V).

  For example, when forming an image having a density corresponding to the density of the solid patch image, the control unit 401 increases the correction laser power LPm (V) by four levels and uses the increased laser power (V). The solid image density reproducibility is maintained. Thereby, execution of light quantity calibration is completed.

  Here, when the execution of the light amount calibration is completed, the light amount calibration execution unit 402 notifies the toner supply unit 403 to that effect, and the toner supply unit 403 that has received the notification notifies the correction laser power LPm ( V) and the reference laser power LP (V), or the toner supply amount to the developing container 40 is adjusted based on the measured density CTDm (−) and the reference density CTD (−) of the halftone patch (FIG. 5: S107). ).

  Any method may be used for the toner replenishing means 403 to adjust the toner replenishment amount to the developing container 40.

  For example, when the toner replenishment amount is adjusted based on the correction laser power LPm (V) and the reference laser power LP (V), the following is performed.

  That is, the toner replenishing unit 403 first refers to a laser power / toner replenishment amount graph stored in advance in the storage unit 404.

  As shown in FIG. 7A, the laser power / toner supply amount graph 700 is a linear graph in which the toner supply amount decreases as the laser power increases. In the graph 700, the reference laser power is reduced. LP (V) is associated with a reference toner supply amount V0 (mg / 1 pulse) as a reference in advance. The graph 700 is linear, but may be curved.

  Here, the unit of the toner replenishment amount V0 is one pulse per unit printing rate (or unit dot count) applied to the DC motor in a DC motor that rotates a supply unit that supplies toner to the developing container 40. Although displayed as a toner amount per driving engine (mg / 1 pulse), it may be displayed as an ON time (msec / 1 pulse) within one pulse period per unit printing rate applied to the DC motor.

  The toner replenishing means 403 associates the corrected laser power LPm (V) with the laser power / toner replenishment amount graph 700, and supplies the toner replenishment amount V1 (mg / mg) of the laser power / toner replenishment amount graph 700. 1 pulse) can be calculated backward. Therefore, the toner replenishing means 403 determines the reversely calculated toner replenishment amount V1 (mg / 1 pulse) as a correction toner replenishment amount corresponding to the correction laser power LPm (V), and the correction toner replenishment amount V1 ( Toner replenishment is executed at (mg / 1 pulse).

  Here, since the correction laser power LPm (V) is lower by 20% than the reference laser power PL (V), the correction toner supply amount V1 (mg / 1 pulse) is the reference toner supply amount V0. It is set higher by 110% (1.1 times) than (mg / 1 pulse).

  Thereby, for example, when the correction laser power LPm (V) is lower than the reference laser power PL (V), it is estimated that the toner charge amount is high, and the toner replenishing means 403 moves to the developing container 40. By increasing the toner replenishment amount V1 (mg / 1 pulse), it becomes possible to reduce the toner charge amount of the entire developing device. As a result, it is possible to execute image formation with stable image quality.

  Contrary to the above, when the correction laser power LPm (V) is higher than the reference laser power PL (V), the correction toner replenishment is performed according to the laser power / toner replenishment amount graph 700. The amount V1 (mg / 1 pulse) is set lower than the reference toner replenishment amount V0 (mg / 1 pulse).

  As a result, contrary to the above, it is possible to increase the toner charge amount of the entire developing device.

  In the above description, the toner replenishing means 403 calculates the corrected toner replenishment amount V1 (mg / 1 pulse) by making the laser power / toner replenishment amount graph 700 correspond to the correction laser power LPm (V). However, other methods may be used.

  For example, the toner replenishing means 403 calculates a change amount X (V) obtained by subtracting the reference laser power LP (V) from the corrected laser power LPm (V), and the laser power / toner replenishing amount graph 700 Corresponding to the change amount X (V), the toner supply amount change amount Y (mg / 1 pulse) is calculated backward, and this is added to the reference toner supply amount V0 (mg / 1 pulse), thereby correcting the correction. The toner replenishment amount V1 (mg / 1 pulse) can be calculated.

  The corrected toner replenishment amount V1 (mg / 1 pulse) may be calculated by multiplying the reference toner replenishment amount V0 by a predetermined ratio that decreases in response to the increase in the change amount X. As a method for calculating the correction toner supply amount V1 (mg / 1 pulse), a known calculation method may be used.

  Unlike the above, for example, when the toner replenishment amount is adjusted based on the measured density CTDm (−) and the reference density CTD (−) of the halftone patch, the following is performed.

  That is, the toner replenishing unit 403 first refers to a density / toner replenishment amount graph stored in advance in the storage unit 404.

  As shown in FIG. 7B, the density / toner supply amount graph 701 is a linear graph in which the toner supply amount increases as the density of the halftone patch increases. The density CTD (−) and the reference toner supply amount V0 (mg / 1 pulse) are associated in advance. The graph 701 is linear, but may be curved.

  When the density / toner replenishment amount graph 701 is associated with the measured density CTDm (−), the toner replenishing means 403 calculates the toner replenishment amount V1 (mg / 1 pulse) in the density / toner replenishment amount graph 701 in a reverse manner. I can do it. Therefore, the toner replenishing means 403 uses the calculated toner replenishment amount V1 (mg / 1 pulse) as the corrected toner replenishment amount corresponding to the measured density CTDm (−) (in other words, the corrected laser power LPm (V)). And the toner supply is executed with the corrected toner supply amount V1 (mg / 1 pulse).

  Here, since the measured density CTDm (−) is 20% higher than the reference density CTD (−), the correction toner replenishment amount V1 (mg / 1 pulse) is the power laser / toner replenishment amount. Similar to the graph 700, the reference toner replenishment amount V0 (mg / 1 pulse) is set higher by 110% (1.1 times).

  Thereby, for example, when the measured density CTDm (−) is higher than the reference density CTD (−), it is estimated that the charge amount of the toner is high, and the toner replenishing means 403 causes the toner to be supplied to the developing container 40. It is possible to increase the replenishment amount V1 (mg / 1 pulse) and to reduce the toner charge amount of the entire developing device.

  Contrary to the above, when the measured density CTDm (−) is lower than the reference density CTD (−), the corrected toner replenishment amount V1 (mg / 1) according to the density / toner replenishment amount graph 701. (Pulse) is set lower than the reference toner supply amount V0 (mg / 1 pulse).

  Further, as described above, for example, the toner replenishing unit 403 calculates the change amount Z (−) obtained by subtracting the reference density CTD (−) from the measured density CTDm (−), and the density / toner replenishment amount graph. 701 is associated with the change amount Z (−), and the toner supply amount change amount Y (mg / 1 pulse) is calculated backward and added to the reference toner supply amount V0 (mg / 1 pulse). Thus, the correction toner supply amount V1 (mg / 1 pulse) may be calculated.

  Therefore, even if the toner charge amount in image formation greatly fluctuates due to fluctuations in the toner density of the developer in the developing container 40, environmental fluctuations such as temperature and humidity fluctuations, and noise such as developer deterioration, the light quantity calibration By adjusting the toner replenishment amount based on the execution result of the application, stable image formation can be performed for a long time.

  As described above, in the present invention, a halftone patch having a preset reference density CDT (−) is formed with a preset reference laser power LP (V), and the density of the halftone patch is measured. Light amount calibration execution means 402 for correcting (determining) the laser power based on the measured density CDTm (−), the reference density CDT (−), and the reference laser power LP (V) measured, and the post-correction The toner supply amount to the developing container 40 is adjusted based on the corrected laser power LPm (V) and the reference laser power LP (V), or the measured density CTDm (−) and the reference density CTD (−) of the halftone patch. And toner replenishing means 403.

  This makes it possible to maintain a stable image quality by changing the toner replenishment amount based on the laser power.

  Note that the toner replenishing unit 402 according to the present invention includes the corrected laser power LPm (V) and the reference laser power LP (V) after correction, or the measured density CTDm (−) and the reference density CTD (−) of the halftone patch. ), The toner replenishment amount to the developing container 40 is adjusted. However, other configurations may be used.

  For example, predetermined upper threshold value (V) and lower limit threshold value (V) are provided above and below the reference laser power LP (V), respectively, and the toner replenishing means 402 causes the corrected laser power LPm (V) and the The upper limit threshold (V) and the lower limit threshold (V) are respectively compared, the correction laser power LPm (V) is equal to or lower than the upper limit threshold (V), and the correction laser power LPm (V) is equal to the lower limit. When it is equal to or greater than the threshold value (V), the toner replenishment amount is not corrected and the corrected laser power LPm (V) exceeds the upper threshold value (V), or the corrected laser power LPm (V) is the lower threshold value. If it is less than (V), the toner replenishment amount can be adjusted. As a result, the toner replenishment amount can be adjusted only when the correction laser power is remarkably changed from the reference laser power, and the toner charge amount can be gradually corrected.

  When the threshold is set, when the corrected laser power LPm (V) exceeds the upper threshold (V), or when the corrected laser power LPm (V) is less than the lower threshold (V), A change amount obtained by subtracting the upper limit threshold value (V) from the correction laser power LPm (V), or a change amount obtained by subtracting the lower limit threshold value (V) from the correction laser power LPm (V). The corrected toner supply amount V1 (mg / 1 pulse) may be calculated based on the laser power / toner supply amount graph 700. As a result, the toner replenishment amount (mg / 1 pulse) can be adjusted gently.

  Instead of the laser power, the density of a halftone patch may be used. For example, a predetermined upper limit threshold (−) and a lower limit threshold (−) are provided above and below the reference density CDT (−), respectively. The toner replenishing unit 402 compares the measured density CDTm (−) with the upper threshold (−) and the lower threshold (−), respectively, and the measured density CDTm (−) is less than or equal to the upper threshold (−). If the measured density CDTm (−) is equal to or greater than the lower threshold (−), the toner replenishment amount is not corrected, and the measured density CDTm (−) exceeds the upper threshold (−). Alternatively, when the measured density CDTm (−) is less than the lower limit threshold (−), the toner replenishment amount may be adjusted.

  When the measured density CDTm (−) exceeds the upper limit threshold (−), or when the measured density CDTm (−) is less than the lower limit threshold (−), the toner replenishing means 402 performs the measurement. A change amount obtained by subtracting the upper limit threshold value (−) from the density CDTm (−) or a change amount obtained by subtracting the lower limit threshold value (−) from the measured density CDTm (−) and the density / toner supply amount graph 701 The same applies when the correction toner supply amount V1 (mg / 1 pulse) is calculated based on the above.

  Further, when the toner density sensor 40h is present in the developing container 40, the toner replenishing means 403 is based on the correction laser power and the reference laser power, or the measured density and reference density of the halftone patch. The toner replenishment amount may be adjusted by changing the target value of the toner density sensor 40h.

  For example, the toner replenishing unit 403 calculates a change amount obtained by subtracting the reference laser power from the correction laser power, and the target value of the toner density sensor 40h decreases as the laser power increases. Corresponding to the graph, the new target value is calculated backward, and the new target value is set as the target value of the toner density sensor 40h to adjust the toner supply amount.

  The toner replenishing unit 403 calculates a change amount obtained by subtracting the reference laser power from the correction laser power, and the target value of the toner density sensor 40h increases as the laser power increases. Corresponding to the graph, a new target value may be calculated backward, and the new target value may be set as the target value of the toner density sensor 40h to adjust the toner supply amount. Even if comprised in this way, the effect similar to the above can be acquired.

  In the present invention, the touch-down development method is assumed. However, any image forming apparatus may be used as long as the image forming apparatus is a developing device using a two-component developer. For example, an image forming apparatus of a hybrid development method may be used.

  In the present invention, the parameter of a predetermined color (for example, black) has been described, but the same applies to parameters of other colors of yellow (Y), magenta (M), and cyan (C).

  In the embodiment of the present invention, the image forming apparatus 1 is configured to include each unit. However, a program that realizes each unit may be stored in a storage medium, and the storage medium may be provided. . In this configuration, the image forming apparatus 1 is caused to read the program, and the image forming apparatus 1 realizes the respective units. In that case, the program itself read from the recording medium exhibits the effects of the present invention. Furthermore, it is possible to provide a method for storing the steps executed by each means in a hard disk.

  As described above, the image forming apparatus and the image forming method according to the present invention are useful not only for complex machines but also for copying machines, printers, etc., and by changing the toner replenishment amount based on the laser power, stable image quality can be obtained. This is effective as an image forming apparatus and an image forming method that can be maintained.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 401 Control means 402 Light quantity calibration execution means 403 Toner replenishing means 404 Storage means

Claims (5)

An image forming apparatus capable of performing light quantity calibration for forming an image with a two-component developer,
A halftone patch having a preset reference density is formed with a preset reference laser power, the density of the halftone patch is measured, and the measured density, the reference density, and the reference laser power are measured. A light amount calibration executing means for correcting the laser power based on
The amount of change by subtracting the reference laser power from the correction laser power is calculated, and the amount of change is back-calculated corresponding to a graph in which the amount of toner replenishment decreases as the laser power increases. An image forming apparatus, comprising: a toner replenishing unit that replenishes the toner after correction, with an amount obtained by adding the change amount to a reference toner replenishing amount corresponding to the reference laser power as a toner replenishing amount . An image forming apparatus capable of performing light quantity calibration for forming an image with a two-component developer,
A halftone patch having a preset reference density is formed with a preset reference laser power, the density of the halftone patch is measured, and the measured density, the reference density, and the reference laser power are measured. A light amount calibration executing means for correcting the laser power based on
A change amount obtained by subtracting the reference density from the measured density of the halftone patch is calculated, and the change amount is associated with a graph in which the toner supply amount increases as the density of the halftone patch increases. And a toner replenishing means for replenishing the toner after correction, with the amount of change added to the reference toner replenishing amount corresponding to the reference density as a toner replenishing amount. Image forming apparatus. The toner replenishing means determines a target value of the toner density sensor based on the correction laser power and reference laser power, or the measured density and reference density of the halftone patch when a toner density sensor is present in the developing container. by changing, the image forming apparatus according to claim 1 or 2 for adjusting the toner supply amount. An image forming method of an image forming apparatus capable of performing light amount calibration, which forms an image with a two-component developer,
A halftone patch having a preset reference density is formed with a preset reference laser power, the density of the halftone patch is measured, and the measured density, the reference density, and the reference laser power are measured. Correcting the laser power based on:
The amount of change by subtracting the reference laser power from the correction laser power is calculated, and the amount of change is back-calculated corresponding to a graph in which the amount of toner replenishment decreases as the laser power increases. And a toner replenishing step for replenishing the toner after correction, with the amount of change added to a reference toner replenishing amount corresponding to the reference laser power as a toner replenishing amount . An image forming method of an image forming apparatus capable of performing light amount calibration, which forms an image with a two-component developer,
A halftone patch having a preset reference density is formed with a preset reference laser power, the density of the halftone patch is measured, and the measured density, the reference density, and the reference laser power are measured. Correcting the laser power based on:
A change amount obtained by subtracting the reference density from the measured density of the halftone patch is calculated, and the change amount is associated with a graph in which the toner supply amount increases as the density of the halftone patch increases. And a toner replenishment step of replenishing the toner after correction, with the amount of change added to the reference toner replenishment amount corresponding to the reference density as a toner replenishment amount. Image forming method.

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