JP2015068954A - Image formation device and image formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device 1 capable of appropriately detecting interface rise of a developer to maintain image quality.SOLUTION: An image formation device 1 comprises: density measurement means 402 that forms a solid band image for two rotations of a drawing roller 40c of a development device HB to measure each of a density of the solid band image of a first rotation and a density of the solid band image of a second rotation; density determination means 403 that determines whether or not a first subtraction value in which a density ID2 of a solid band image 702b of the second rotation is subtracted from a density ID1 of a solid band image 702a of the first rotation exceeds a first threshold value; and supply means 404 that supplies a developer of a first supply amount set in advance when the first subtraction value does not exceed the first threshold value, and that supplies a developer of a second supply amount less than the first supply amount when the first subtraction value exceeds the first threshold value.

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 appropriately detecting an increase in the interface of a developer and maintaining image quality.

  In recent image forming apparatuses, for example, an image carrier, a charger, an exposure unit, a developing unit, a transfer unit, a cleaning unit, and a toner reservoir are integrated as an imaging unit with the main purpose of reusing resources. There are cases where the unit is detachably attached to the main body of the image forming apparatus.

  However, in this image forming apparatus, process conditions (development bias values, etc.) are set regardless of individual variations (including variations in developer characteristics) of the imaging unit. Therefore, when the imaging unit is replaced, there is a problem that the toner density in the developing device is too high or too low due to individual variations of the imaging unit.

  For example, the density of an image to be formed (this is simply referred to as “image density”. In this specification, the term “toner density” refers to the density of toner in the developing device within a range that does not obscure the meaning. In the case of using an imaging unit that is in a state where it is difficult to increase the image density, it is difficult to increase the image density. When the toner density in the container is kept high, there arises a problem that fog and dust increase.

  On the other hand, when using an imaging unit or the like in which the image density tends to be high, the toner density in the developing device is kept low, so that the total amount of developer is reduced and the supply to the developing roller is uniform. This causes a problem that the image is lost and an image defect occurs.

  If a toner concentration detection sensor is provided to manage the toner concentration in the developing device, the above problem can be avoided. However, providing a toner concentration detection sensor increases the cost.

  In order to solve such a problem, Japanese Patent Application Laid-Open No. 2004-226627 (Patent Document 1) discloses an image forming apparatus in which an imaging unit that includes at least a developing device and performs image formation is attached to and detached from the main body. Is disclosed. In this image forming apparatus, an imaging unit loading detection unit that detects that the imaging unit is loaded on the main body, and a development bias output variable unit that variably sets a development bias output to the developing unit of the imaging unit. And an image density detector for detecting an image density of the image formed by the imaging unit. Furthermore, an environment information acquisition unit that acquires environment information indicating an environment in which the main body exists, and operates the imaging unit according to a detection result indicating that the imaging unit is loaded, and a development bias output to the developing device, A correspondence information acquisition unit that acquires correspondence information representing a correspondence relationship with the image density, and a reference characteristic setting unit that sets the reference characteristic by limiting the correspondence information with environment information at the time of the acquisition of the correspondence information. As a result, the toner density can be stabilized and the image quality can be improved without using an expensive toner density detection sensor.

JP 2004-226627 A

  By the way, in a developing device using a two-component developer composed of a toner and a carrier, the toner and the carrier are mixed in a toner supplier, and a pumping roller that pumps the two-component developer from the toner supplier; A magnetic roller (mag roller) for carrying toner from the two-component developer pumped up by the pumping unit; and a developing roller for developing the two-component developer carried by the magnetic roller onto the photosensitive drum. .

  Here, as the amount of developer supplied to the developing container of the developing device increases, the interface of the developer rises between the developing container and the pumping roller. Then, the developer remaining without being supplied from the drawing roller to the magnetic roller remains at the developer interface and is supplied again to the drawing roller. In this case, since the toner concentration of the re-supplied developer is usually low, when this is used for image formation, there is a problem that an image with a low toner concentration is formed and the image quality is lowered. The technique described in Patent Document 1 cannot solve this problem.

  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 appropriately detecting an increase in the interface of the developer and maintaining the image quality. For the purpose.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention includes an image forming apparatus having a developing roller provided with a pumping roller above a bottom portion of a developing container for storing a two-component developer. The apparatus adopts the following configuration.

  That is, the present invention forms a solid band image for two rounds of the pumping roller of the developing device, and measures the density of the solid band image for the first round and the density of the solid band image for the second round. Density determination means for determining whether or not a first subtracted value obtained by subtracting the density of the first solid band image from the density of the second round solid band image exceeds a first threshold; When the first subtraction value does not exceed the first threshold value, the developer is replenished with a preset first supply amount, and when the first subtraction value exceeds the first threshold value. And a replenishing means for replenishing the developer with a second replenishment amount smaller than the first replenishment amount.

  The density measuring means can be configured such that the density is measured by reflected light intensity and the first threshold value is 0.1 based on the ISO 5 series regulations.

  In addition, the solid band image of two rounds of the pumping roller corresponds to the position of a predetermined density detection sensor installed on the intermediate transfer belt, and the longitudinal direction corresponds to the length of two rounds of the pumping roller. The short direction is a substantially rectangular solid band image corresponding to the length in which the density can be detected by the density detection sensor.

  Further, the position of the solid band image for two rounds of the pumping roller is such that the developer supplied is supplied when the supply port for supplying the developer to the developer container is the uppermost stream in the agitating and conveying direction of the developer. This corresponds to the most downstream position in the agitating and conveying direction of the developer returning to the mouth.

  Further, the density determination means determines whether or not a second subtraction value obtained by subtracting a density used at the time of calibration from a density of the solid band image of the first round exceeds a second threshold value, and When the second subtraction value exceeds the second threshold value, it is determined whether or not the first subtraction value exceeds the first threshold value.

  The present invention can also be provided as an image forming method for an image forming apparatus having a developing device provided with a pumping roller above the bottom of a developing container for storing a two-component developer.

  That is, the present invention forms a solid band image for two rounds of the pumping roller of the developing device, and measures the density of the solid band image for the first round and the density of the solid band image for the second round, respectively. Determining whether or not a first subtraction value obtained by subtracting the density of the solid band image of the first round from the density of the solid band image of the second round exceeds a first threshold; and the first subtraction When the value does not exceed the first threshold, the developer is replenished with a preset first supply amount, and when the first subtraction value exceeds the first threshold, the first And a step of replenishing the developer with a second replenishment amount smaller than the replenishment 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 appropriately detect the increase in the interface of the developer and maintain the image quality.

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. It is front sectional drawing of the developing device HB of this invention. FIG. 4 is a plan sectional view showing a positional relationship between the image forming unit FB and the developing device HB of the present invention. FIG. 6 is a front cross-sectional view of the developing device HB according to the present invention when no increase in the developer interface occurs. FIG. 6 is a front cross-sectional view of the developing device HB according to the present invention when the developer interface rises.

  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 a developer 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 developer 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 potential 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 developer on the surface of the magnetic roller 40b after the developing operation on the photosensitive drum 10 is removed by the magnetic roller doctor blade 40g, flows down along the surface of the magnetic roller doctor blade 40g, and passes through a flow path (not shown). The developer stored in the developer container 40 is mixed.

  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 a predetermined value, toner (a developer having a toner concentration higher than the predetermined value) is supplied from a toner cartridge (not shown) to the developing container 40, and the toner concentration is higher than the predetermined 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 the interface rise of the developer is detected. (FIG. 5: S101).

  Any method may be used as the method for determining whether or not the control unit 401 detects an increase in the developer interface. For example, the control unit 401 determines whether or not it is a specific time point. Specifically, the control unit 401 has printed a predetermined number of sheets when the image forming apparatus 1 is turned on. Time (when the number of printed sheets exceeds a predetermined threshold), time when a predetermined amount of toner is consumed by the dot count of the printed image (when toner consumption exceeds a predetermined threshold), time when predetermined calibration is executed A method for determining whether or not any of the above is adopted.

  Here, since the image forming apparatus 1 has been started up earlier, the control unit 401 determines that an increase in the developer interface is detected (FIG. 5: S101 YES), and notifies the density measurement unit 402 accordingly. Upon receiving the notification, the density measuring unit 402 forms a solid band image for two rounds of the pumping roller 40c of the developing device, and determines the toner density of the solid band image for the first round and the toner density of the solid band image for the second round. Measure each.

  The density measuring unit 402 forms a solid band image for two rounds of the pumping roller 40c of the developing device (for example, the developing apparatus HB), and the toner density of the solid band image for the first round and the solid band image for the second round. Any method may be used for measuring the toner density, but for example, the method is as follows.

  First, as shown in FIG. 6, the density measuring means 402 causes the pumping roller 40c of the developing device HB to pump up the developer, and supplies the developer of the pumping roller 40c to the magnetic roller 40b of the developing device HB. The developer of the magnetic roller 40b is applied to the developing roller 40a of the developing device HB.

  Further, the density measuring means 402 uniformly charges the surface of the photosensitive drum 10 by the charger 11, and is based on solid band image data for two rounds of the pumping roller 40c previously stored in a predetermined memory. Thus, the exposure device 12 forms an electrostatic latent image corresponding to the solid band image for two rounds of the pumping roller 40c.

  Here, the solid band image formed by the density measuring unit 402 may be any solid band image as long as it is a solid band image corresponding to two rounds of the pumping roller 40c. For example, as shown in FIG. The longitudinal direction corresponds to one of the two density detection sensors 605 and 606 installed on the intermediate transfer belt B1 (for example, the position 701 of one density detection sensor 605). A substantially rectangular solid band image 702 corresponding to a minute length 2L and having a short side direction corresponding to a length W that can be detected by the density detection sensor 605 is employed. As a result, wasteful toner consumption can be prevented and an increase in the developer interface can be detected.

  The position of the solid band image 702 is not particularly limited as long as the object of the present invention is not impaired. Here, the first agitation spiral 40d and the second agitation spiral 40e for agitating the developer are transported along the predetermined direction in the developer container 40 and circulate. When the replenishing supply port 703 is the uppermost stream in the developer agitation transport direction, it is preferable to correspond to the most downstream position 704 in the developer agitation transport direction in which the conveyed developer returns to the replenishment port 703. . As a result, the position where the developer is likely to stay is the position 704 that is the most downstream in the developer agitating and transporting direction of the developer container 40, and therefore, it is possible to detect an increase in the developer interface with high accuracy.

  Corresponding to the electrostatic latent image formed on the photosensitive drum 10, the developer toner of the developing roller 40a flies to form a solid band image 702 (toner image) for two rounds of the pumping roller 40c. ) Is formed and transferred to the intermediate transfer belt B1 (FIG. 5: S102). As a result, a solid band image 702 corresponding to two rounds of the pumping roller 40c is formed.

  Further, the density measuring unit 402 activates a predetermined density detection sensor 605 corresponding to the position where the solid band image 702 is formed on the intermediate transfer belt B1, so that the solid band image 702 of the intermediate transfer belt B1 is detected. Among them, the toner density (for example, ID1) of the first round solid band image 702a and the toner density (ID2) of the second round solid band image 702b are measured.

  Here, any method may be used for the density measuring unit 402 to measure the toner density ID1 of the first solid band image 702a and the toner density ID2 of the second solid band image 702b. For example, it is made as follows.

  That is, the first detection time from the start of the formation of the solid band image 702 until the center position of the solid band image 702a in the first round of the solid band image 702 reaches the detection position of the density detection sensor 605 is set. Pre-stored in the memory. Then, the density measuring unit 402 measures an elapsed time from the start of the formation of the solid band image 702 with a predetermined timer, and when the elapsed time has passed the first detection time, the density detection unit 402 The density is detected from the sensor 605, and is set as the toner density ID1 of the solid band image 702a in the first round (FIG. 5: S103).

  Similarly to the above, from the start of the formation of the solid band image 702 until the center position of the second solid band image 702b of the solid band image 702 comes to the detection position of the density detection sensor 605. Second detection time (after the center position of the solid band image 702a of the first round has reached the detection position of the density detection sensor 605, the center position of the solid band image 702b of the second round is the position of the density detection sensor 605. The time until the detection position is reached may be stored in the memory in advance. The density measuring unit 402 measures an elapsed time from the start of the formation of the solid band image 702 with a predetermined timer, and when the elapsed time has passed the second detection time, the density detection unit 402 The density is detected from the sensor 605, and is set as the toner density ID2 of the solid image 702b in the second round (FIG. 5: S104).

  The measured toner density is usually 0.0 for blank paper and 1.2 to 1.3 for a solid image.

  When the density measuring unit 402 finishes measuring the toner density ID1 of the first solid band image 702a and the toner density ID2 of the second solid band image 702b, it notifies the density determining unit 403 to that effect. . Upon receiving the notification, the density determination unit 403 subtracts the toner density ID1 of the first solid band image 702a from the toner density ID2 of the second solid band image 702b. It is determined whether or not the difference exceeds a first threshold (for example, 0.1) (FIG. 5: S105).

  Here, when the developer interface does not rise, as shown in FIG. 8, even if excess developer that has not been supplied to the magnetic roller 40b returns to the pumping roller 40c, Then, it falls to the second stirring spiral 40e of the developing container 40. Since the returned developer is once in contact with the magnetic roller 40b, the toner concentration of the developer is usually lower than the toner concentration of the developer stirred by the second stirring spiral 40e. Become. However, since the developer interface S1 has not risen, the dropped developer is again stirred by the second stirring spiral 40e to reach a predetermined toner concentration. In other words, the toner density of the solid band image 702 for two rounds of the pumping roller 40c is substantially constant at any position (location), and the toner density ID1 (for example, 1.3) of the solid band image 702a for the first round. ) And the toner density ID2 (for example, 1.3) of the solid image 702b in the second round hardly occurs. That is, the first subtraction value does not exceed the first threshold value.

  In this case, when the first subtraction value does not exceed the first threshold as a result of the determination (FIG. 5: S105 NO), the density determination means 403 does not raise the developer interface S1. And the supply means 404 is notified of this. Receiving means 404 having received the notification maintains (adopts) a preset first replenishing amount, and uses the first replenishing amount to supply developer (toner or / and carrier) to developer container 40. Is replenished (FIG. 5: S106).

  Specifically, the replenishing unit 404 monitors the toner concentration sensor 40h of the developing container 40, and when the toner concentration of the developer in the developing container 40 becomes lower than a predetermined value, the replenishing unit 404 performs the toner not shown. Toner (a developer having a toner concentration higher than a predetermined value) is supplied from the cartridge through the supply port 703 by the first supply amount. Further, when the toner concentration of the developer in the developing container 40 becomes higher than a predetermined value, the replenishing means 404 replenishes the carrier from a carrier cartridge (not shown) by the first replenishment amount through the replenishing port 703. As a result, an appropriate amount of developer is supplied to the developer container 40 without causing an increase in the developer interface S1.

  On the other hand, when the developer interface rises, as shown in FIG. 9, when the excess developer that has not been supplied to the magnetic roller 40b returns to the pumping roller 40c, the developer becomes the second one. Without being dropped into the stirring spiral 40e, the developer interface S2 rises, and the pump is again pumped up to the pumping roller 40c. In other words, the developer having a low toner concentration is re-supplied to the pumping roller 40c as it is without being stirred by the second stirring spiral 40e. Therefore, out of the toner density of the solid band image 702 for the second round of the drawing roller 40c described above, the toner density ID2 of the solid band image 702b for the second round is lower than the toner density ID1 of the solid band image 702a for the first round. That is, in other words, the toner density ID1 of the solid belt image 702a in the first round is increased, and the density difference is generated. That is, the first subtraction value exceeds the first threshold value.

  In this case, as a result of the determination, when the first subtraction value exceeds the first threshold value (FIG. 5: S105 YES), the density determination means 403 causes an increase in the developer interface S1. The supply means 404 is notified of this. Upon receipt of the notification, the replenishing means 404 replenishes the developer (toner or / and carrier) to the developing container 40 with a second replenishment amount smaller than the first replenishment amount (FIG. 5: S107). In other words, the replenishing means 404 controls to reduce the developer replenishment amount.

  Specifically, the replenishing unit 404 monitors the toner density sensor 40h, and when the toner concentration of the developer in the developing container 40 becomes lower than a predetermined value, the replenishing unit 404 removes toner from the toner cartridge. Replenish only the second replenishment amount. When the toner concentration of the developer in the developing container 40 becomes higher than a predetermined value, the replenishing means 404 replenishes the carrier from the carrier cartridge by the second replenishment amount. This makes it possible to reduce the amount of developer replenishment in the future, to lower the rising developer interface S2, and to eliminate the developer interface S2 increase. In addition, since the increase in the developer interface causes re-supply of the developer having a low toner concentration, there is a possibility that the image quality due to the re-supplied developer may be deteriorated. By reducing, the increase in the developer interface can be positively suppressed, and the image quality can be maintained.

  Here, the first threshold value is not particularly limited as long as the object of the present invention is not hindered as long as it is a threshold value that can reflect the resupply of the developer due to the increase in the developer interface S2. For example, 0.1 is preferable. This makes it possible to detect the increase in the developer interface S2 with high accuracy.

  In addition, when the density determination unit 403 completes the measurement of the toner density ID1 of the first round solid band image 702a and the toner density ID2 of the second round solid band image 702b, the first subtraction value becomes the first subtraction value. Although it has been determined whether or not the first threshold is exceeded, other configurations may be used.

  For example, when the measurement of the toner density ID1 of the first round solid band image 702a and the toner density ID2 of the second round solid band image 702b is completed, the density determination unit 403 first determines the solid band of the first round. A second subtraction value (second density difference) obtained by subtracting the toner density (for example, ID0, the absolute value is about 1.3) used during calibration from the toner density ID1 of the image 702a is the second. It is determined whether or not a threshold value (for example, 0.1) is exceeded.

  As a result of the determination, if the second subtraction value does not exceed the second threshold value, that is, the toner density ID1 of the solid band image 702a in the first round is equivalent to the toner density ID0 used during calibration. In some cases, the density determination unit 403 determines that the increase of the developer interface S1 has not occurred, and the replenishment unit 404 replenishes the developer with the first replenishment amount (FIG. 5: FIG. 5). S106).

  On the other hand, as a result of the determination, if the second subtraction value exceeds the second threshold value, for example, the toner density ID1 of the solid band image 702a in the first round is 1.4 and is used during calibration. When the toner density ID 0 is 1.3, the density determination unit 403 further determines whether or not the first subtraction value exceeds the first threshold value.

  This is because when the developer interface S2 rises, the toner density ID1 of the solid belt image 702a in the first round is higher than normal (1.4 or more). It is possible to detect the increase of the agent interface S2 with high accuracy.

  The second replenishment amount is not particularly limited as long as it does not obstruct the object of the present invention as long as the above-described developer interface S2 increase can be eliminated. 3/4, 1/2, 2/3, 1/3, and the like. The second replenishment amount is appropriately changed depending on the volume of the developing container 40, the size of the drawing roller 40c, the type of developer, and the like.

  By the way, after the replenishing means 404 replenishes the developer with the second replenishment amount, when the developer interface S2 is lowered to an appropriate height, the following is performed. Become.

  That is, it is determined that the control unit 401 detects an increase in the developer interface at some timing (FIG. 5: S101 YES), and the density measuring unit 402 forms a solid band image for two rounds of the pumping roller 40c. Then, the toner density of the solid band image of the first round and the toner density of the solid band image of the second round are respectively measured (FIG. 5: S102 → S103 → S104). Then, the density determination unit 403 determines whether or not the first subtraction value exceeds the first threshold value (FIG. 5: S105). Here, since the increase in the developer interface has been eliminated, the density determination unit 403 determines that the first subtraction value does not exceed the first threshold (FIG. 5: S105 NO), and the replenishment unit. 404 adopts (selects and returns) the first supply amount (normal supply amount) from the second supply amount, and replenishes the developer with the first supply amount (FIG. 5: S106). As a result, when the rise in the developer interface is solved, the developer can be replenished with a normal replenishment amount.

  In this way, in the present invention, a solid band image for two rounds of the drawing roller 40c of the developing device HB is formed, and the toner density of the solid band image for the first round and the toner density of the solid band image for the second round are respectively set. The first subtraction value obtained by subtracting the toner density ID1 of the first solid band image 702a from the toner density ID2 of the second solid band image 702b and the toner density measuring means 402 to measure exceeds the first threshold. Density determining means 403 for determining whether or not to perform, and when the first subtraction value does not exceed the first threshold value, the developer is replenished with a preset first replenishment amount, and the first And a replenishment means 404 for replenishing the developer with a second replenishment amount that is smaller than the first replenishment amount when the subtracted value exceeds the first threshold value.

  As a result, it is possible to appropriately detect an increase in the interface of the developer and maintain the image quality.

  Although the present invention assumes a touch-down development system, any image forming apparatus may be used as long as the image forming apparatus is a developing apparatus using a two-component developer. In the touchdown development method, a toner thin layer is formed on the developing sleeve by transferring only toner from a magnetic roller carrying a two-component developer containing toner and carrier, and an electrostatic latent image is formed. In other words, the electrostatic latent image is developed as a toner image by flying toner from the thin toner layer onto the surface of the photoreceptor.

  In the present invention, the black developing device has been described, but other colors such as yellow (Y), magenta (M), and cyan (C) may be used.

  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 multi-function machines but also for copying machines, printers, and the like, and appropriately detect an increase in the interface of the developer to maintain image quality. This is effective as an image forming apparatus and an image forming method.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 401 Control means 402 Density measurement means 403 Density determination means 404 Developer supply means

Claims (8)

An image forming apparatus having a developing device provided with a pumping roller above a bottom portion of a developing container for storing a two-component developer,
Density measuring means for forming a solid band image for two rounds of the pumping roller of the developing device, and measuring the density of the solid band image for the first round and the density of the solid band image for the second round;
A density determination means for determining whether or not a first subtraction value obtained by subtracting the density of the first round solid band image from the density of the second round solid band image exceeds a first threshold;
When the first subtraction value does not exceed the first threshold value, the developer is replenished with a preset first supply amount, and the first subtraction value exceeds the first threshold value And a replenishing means for replenishing the developer with a second replenishment amount smaller than the first replenishment amount. The concentration measuring means measures the concentration by reflected light intensity based on the ISO 5 series regulations,
The image forming apparatus according to claim 1, wherein the first threshold value is 0.1. The solid band image of two rounds of the pumping roller corresponds to the position of a predetermined density detection sensor installed on the intermediate transfer belt, the longitudinal direction corresponds to the length of two rounds of the pumping roller, and is short. The image forming apparatus according to claim 1, wherein the hand direction is a substantially rectangular solid band image corresponding to a length at which the density can be detected by the density detection sensor. The position of the solid band image for two rounds of the pumping roller is such that when the replenishing port for supplying the developer to the developer container is the uppermost stream in the stirring and conveying direction of the developer, the conveyed developer is supplied to the replenishing port The image forming apparatus according to claim 1, wherein the image forming apparatus corresponds to a downstreammost position in the stirring and conveying direction of the developer that returns. The density determination means determines whether or not a second subtraction value obtained by subtracting a density used at the time of calibration from a density of the solid band image in the first round exceeds a second threshold, The image formation according to claim 1, wherein when the subtraction value exceeds the second threshold value, it is determined whether or not the first subtraction value exceeds the first threshold value. apparatus. An image forming method of an image forming apparatus having a developing device provided with a pumping roller above a bottom of a developing container for storing a two-component developer,
Forming a solid band image for two rounds of the pumping roller of the developing device, and measuring the density of the solid band image for the first round and the density of the solid band image for the second round;
Determining whether or not a first subtraction value obtained by subtracting the density of the first round solid band image from the density of the second round solid band image exceeds a first threshold;
When the first subtraction value does not exceed the first threshold value, the developer is replenished with a preset first supply amount, and the first subtraction value exceeds the first threshold value And a step of replenishing the developer with a second replenishment amount smaller than the first replenishment amount.   A program for causing a computer to execute the image forming method according to claim 6. A computer-readable storage medium storing the program according to claim 7.

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