JP5233741B2 - Image density estimation apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image density estimation apparatus and an image forming apparatus.

  In Patent Document 1, in an image forming apparatus that performs printing by transferring a toner image formed on an image carrier to a recording medium, a plurality of image forming units that form color and black toner images, and toner images of each color A toner holder that holds the toner, a reading unit that reads the density of the toner image held on the toner holder, a shielding member that is provided between the reading unit and the toner holder, and shields the reading unit, Opening and closing means for switching the shielding member to either an open state enabling reading by the reading means or a closed state shielding the reading means, and an adjusting means for adjusting the reading means, the reading The means includes a light emitting unit whose light emission amount can be adjusted, and a first light receiving unit and a second light receiving unit each having an output corresponding to the light receiving amount, and the first light receiving unit receives light emitted from the light emitting unit. Toner holding The second light receiving unit is disposed so as to receive the regular reflected light in which the light emitted from the light emitting unit is regularly reflected by the surface of the toner holding member. The first light receiving unit receives the diffuse reflected light from the color toner image held on the toner holding body to read the density of the color toner image, and the second light receiving unit receives the toner holding The density of the black toner image is read by receiving specularly reflected light from the black toner image held on the body, and when the shielding member is in the closed state, diffuse reflected light from the shielding member with respect to the emitted light Based on the output of the first light receiving unit according to the above, the adjusting means determines the light emission amount for color reading of the emitted light when reading the density of the color toner image, and the shielding means is opened. is there Then, based on the output from the second light receiving unit according to the specularly reflected light from the surface of the toner holding body with respect to the emitted light, the adjusting means emits the light when reading the density of the black toner image. When the light emission amount for black reading of light is determined and the density of the color toner image is read, the light emitting unit emits light emission having the light emission amount for color reading, and when the density of the black toner image is read, An image forming apparatus is disclosed in which the light emitting unit emits light having the black reading light amount.

  Patent Document 2 discloses an image forming apparatus that controls the image forming condition by detecting the density of a reference toner image for density measurement formed on an image carrier using an optical detection unit. Storage means for irradiating the reference toner image with light from the optical detection means, diffusing and reflecting by the reference toner image, and storing a reference diffuse reflection light quantity detected by the diffuse reflection light receiving element of the optical detection means; The diffuse reflection detected by the diffuse reflected light receiving element when the diffuse reflected light amount detected when the reference toner image is irradiated with light from the optical detection means at a predetermined time does not match the reference diffuse reflected light amount. Control means for controlling the optical detection means so that the amount of light coincides with the reference diffuse reflection light quantity stored in the storage means. Location is disclosed.

JP 2004-110018 A JP 2006-145679 A

  An object of the present invention is to provide an image density estimation apparatus and an image forming apparatus that estimate the image densities of three primary colors with high accuracy without incurring costs as compared with the case without this configuration.

  In order to achieve the above object, an image density estimation apparatus according to claim 1 includes an image carrier that holds an image formed on a surface thereof, and a magnitude of a current that is supplied to the image carrier. Diffuse reflection when irradiating light by the irradiating means with respect to a reference image composed of any one of the three primary colors formed on the surface of the image holding body and irradiating means for irradiating a corresponding amount of light Diffuse reflected light detecting means for detecting a physical quantity indicating the amount of light, and regular reflected light detection for detecting a physical quantity indicating the amount of specularly reflected light when the surface of the image carrier is irradiated with light by the irradiating means. Means, current detection means for detecting the magnitude of current when the irradiation means is energized so that the physical quantity detected by the specular reflection light detection means becomes a predetermined physical quantity, and detected by the current detection means The magnitude of the current The ratio of the physical quantity detected by the diffuse reflected light detecting means or the regular reflected light detecting means when the current of the magnitude detected by the current detecting means is applied and light is applied to the reference image. And calculating means for calculating.

  According to a second aspect of the present invention, there is provided the image density estimation apparatus according to the first aspect of the invention, wherein the calculation means further includes a current having a magnitude detected by the current detection means with respect to the predetermined physical quantity. Is applied to the black reference image formed on the surface of the image carrier to calculate the proportion of the physical quantity detected by the regular reflection light detection means.

  On the other hand, in order to achieve the above object, an image forming apparatus according to a third aspect of the present invention is configured to form an image on the surface of the image density estimating apparatus according to the first or second aspect and the image carrier. A developer supplying means for supplying a developer comprising colored particles and magnetic particles on the surface of the image carrier, and the ratio calculated by the calculating means is set to a predetermined value. Adjusting means for adjusting the ratio of the colored particles contained in the developer to the developer supplied to the surface of the image carrier by the developer supply means.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect of the present invention, the image forming apparatus further includes a display unit that displays information indicating the ratio calculated by the calculation unit.

  According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the fourth aspect, wherein the developer is supplied to the developer supplied by the developer supply means based on the ratio calculated by the calculation means. It further includes deriving means for deriving the ratio of the colored particles contained, and the display means further displays the ratio derived by the deriving means.

  According to the first aspect of the present invention, it is possible to obtain an effect that the image densities of the three primary colors are accurately estimated without incurring costs compared to the case where the present configuration is not provided.

  According to the second aspect of the present invention, it is possible to obtain an effect that the black image density is accurately estimated without incurring costs compared to the case where the present configuration is not provided.

  According to the third aspect of the invention, it is possible to obtain an effect of accurately adjusting the image density without incurring costs compared to the case without the present configuration.

  According to the fourth aspect of the invention, an effect of easily grasping the estimation result of the image density can be obtained as compared with the case where the present configuration is not provided.

  According to the invention which concerns on Claim 5, compared with the case where it does not have this structure, the effect of grasping | ascertaining easily the ratio of the colored particle contained in a developing agent with respect to a developing agent is acquired.

1 is a schematic configuration diagram illustrating a main configuration of an image forming apparatus according to an embodiment. FIG. 2 is a schematic configuration diagram illustrating a main configuration of an image forming unit according to an embodiment. It is a schematic block diagram of a diffusion type sensor. 1 is a block diagram illustrating a main configuration of an electrical system of an image forming apparatus according to an embodiment. It is a schematic block diagram of a regular reflection type sensor. It is a flowchart which shows the flow of a process of the image density estimation process program which concerns on embodiment.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating a main configuration of an image forming apparatus 10 according to the present embodiment.

  As shown in FIG. 1, the image forming apparatus 10 includes an endless belt-like intermediate transfer belt 14 that is wound around a plurality of rollers 12 and conveyed in the direction of arrow E by driving a motor (not shown). A plurality of image forming units 15 (details will be described later) are arranged along the longitudinal direction of the intermediate transfer belt 14.

  Note that the image forming apparatus 10 in the present embodiment also supports color image formation, and toner images corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K). Are formed. Image forming units 15Y, 15M, 15C, and 15K are respectively provided. Hereinafter, the members provided for each color are shown by adding alphabets (Y / M / C / K) indicating the respective colors at the end of the reference numerals. The description will be made by omitting the alphabet at the end of the code.

  The different color toner images formed by the image forming units 15 are transferred onto the intermediate transfer belt 14 so as to overlap each other on the belt surface of the intermediate transfer belt 14. As a result, a color toner image is formed on the intermediate transfer belt 14. In this embodiment, the toner image in which the four color toner images are transferred in a superimposed manner is referred to as a final toner image.

  On the downstream side of the four image forming units 15 in the conveying direction of the intermediate transfer belt 14, a transfer device 26 including two rollers 26A and 26B facing each other is disposed. The final toner image formed on the intermediate transfer belt 14 is fed between the rollers 26A and 26B, taken out from a paper tray 29 provided at the bottom of the image forming apparatus 10, and similarly between the rollers 26A and 26B. Is transferred to the paper 28 that has been conveyed to the paper.

  In addition, a fixing device 30 including a pressure roller 30A and a heating roller 30B is disposed on the conveyance path of the paper 28 onto which the final toner image has been transferred. The paper 28 conveyed to the fixing device 30 is nipped and conveyed by the pressure roller 30A and the heating roller 30B, whereby the final toner image is melted and pressed against the paper 28 to be fixed. As a result, a desired image (color image) is formed on the paper 28. The paper 28 on which the image is formed is discharged out of the apparatus.

  On the other hand, a cleaner 32 that collects toner remaining on the intermediate transfer belt 14 without being transferred to the paper 28 by the transfer device 26 is disposed downstream of the transfer device 26 in the transport direction of the intermediate transfer belt 14. . The cleaner 32 is provided with a blade 34 so as to be in contact with the intermediate transfer belt 14, and collects residual toner by rubbing it.

  Further, on the downstream side of the image forming unit 15 in the transport direction of the intermediate transfer belt 14, a value corresponding to the density of the toner image transferred to a predetermined position on the intermediate transfer belt 14 (hereinafter referred to as “density corresponding value”). . ”Is also provided. A diffusion type sensor 36 is provided for detecting a physical quantity (in this case, a light quantity) used when calculating“.

  FIG. 2 shows the configuration of the image forming unit 15. Since the configuration of each image forming unit 15 is the same, the description is omitted here by omitting the last symbol indicating each color.

  As shown in the figure, the image forming unit 15 includes a photosensitive drum 16 that is disposed in contact with the intermediate transfer belt 14 and rotates in a direction indicated by an arrow F at a predetermined speed.

  A charging roller 18 for charging the photosensitive drum 16 is disposed on the circumferential surface of each photosensitive drum 16. The charging roller 18 is a conductive roller, and its peripheral surface is in contact with the peripheral surface of the photosensitive drum 16, and is arranged so that the axial direction of the charging roller 18 coincides with the axial direction of the photosensitive drum 16. Has been.

  A predetermined voltage (DC voltage −500 V in this embodiment) in which a DC (direct current) component and an AC (alternating current) component are superimposed is applied to the charging roller 18, and follows the rotation of the photosensitive drum 16. The surface of the photosensitive drum 16 is uniformly charged to a predetermined potential (in this embodiment, about −500 V) while rotating as described above.

  Further, an exposure device 20 for forming an electrostatic latent image on the photosensitive drum 16 is provided on the circumferential surface on the downstream side of the charging roller 18 in the rotation direction (arrow F direction) of each photosensitive drum 16. It has been.

  The exposure device 20 includes an LED array in which a plurality of LEDs (light emitting diodes) 20A are arranged along the main scanning direction (the front-rear direction in FIG. 2) during image formation. Irradiation is performed while scanning a light beam based on the image data in the axial direction of the photosensitive drum 16 charged in a positive direction. The potential of the region irradiated with the light beam from the exposure device 20 is increased (in this embodiment, about −200 V), and an electrostatic latent image is formed on the photosensitive drum 16.

  Further, an electrostatic latent image formed on the photosensitive drum 16 is arranged in a predetermined color (yellow / magenta / cyan / black) around the exposure device 20 in the rotation direction of each photosensitive drum 16. A developing device 22 is provided for developing with a toner of any one color) to form a toner image. A toner box 44 that contains toner is connected to the developing device 22 via a pipe (not shown). The amount of toner replenished from the toner box 44 to the developing device 22 is adjusted by the rotation time of a dispense motor (not shown).

  In the present embodiment, a developer including two components of toner particles (colored particles) having negative polarity and carriers (magnetic particles) having positive polarity is applied as the toner. In order to improve development efficiency and transfer efficiency described later, the toner particles are preferably spherical. In the present embodiment, the developer 22 is not replenished with toner particles, but only toner particles are replenished.

  As shown in the figure, the developing unit 22 includes a developing roller 38 and a blade 40 that are disposed close to the photosensitive drum 16. The developing roller 38 is applied with a predetermined voltage in which a DC (direct current) component and an AC (alternating current) component having the same polarity as the surface of the photosensitive drum 16 (negative polarity in the present embodiment) are superimposed. The toner particles are conveyed to the peripheral surface together with the positive polarity carrier loaded in the container 22. Further, the developing roller 38 is driven to rotate in the same direction as the rotation direction of the photosensitive drum 16 (in the direction of arrow G in the figure), and the toner particles and the carrier that are excessively attached to the developing roller 38 are dropped by the blade 40 and developed. 38 evenly.

  The toner attached to the developing roller 38 is supplied to the surface of the photosensitive drum 16 by the rotation of the developing roller 38 in the arrow G direction.

  When the surface potential Vh of the unexposed part of the photosensitive drum 16 is −500 V and the surface potential Vl of the exposed part is −200 V, the DC component Vd of the bias voltage applied to the developing roller 38 is −400 V. In this case, the toner adhering to the developing roller 38 adheres to the exposed portion on the photosensitive drum 16. Therefore, the electrostatic latent image formed on the photosensitive drum 16 is reversely developed.

  On the other hand, a transfer roller 25 for transferring the toner image on each photoconductive drum 16 to the intermediate transfer belt 14 is provided around the downstream side of the developing device 22 in the rotation direction of each photoconductive drum 16. The transfer roller 25 rotates in the direction of arrow H, conveys the intermediate transfer belt 14 at a predetermined speed, and sequentially opposes the photosensitive drum 16. A power supply 42 is connected to the transfer roller 25, and a positive bias voltage is applied to the transfer roller 25 to transfer the toner on the photosensitive drum 16 onto the intermediate transfer belt 14.

  Here, the transfer roller 25 cannot transfer all of the toner on the photosensitive drum 16 to the intermediate transfer belt 14, and toner is not transferred onto the photosensitive drum 16 that has passed the position where the transfer roller 25 is disposed. Slightly remains (transfer residual toner).

  There is also toner (retransfer toner) whose polarity is reversed to plus by the transfer roller 25 and reattached on the photosensitive drum 16. Note that, when a toner image of another color has already been transferred onto the intermediate transfer belt 14 when passing the position where the transfer roller 25 is disposed, the toner of the other color is included in the retransfer toner.

  Therefore, a cleaning roll 24 that temporarily holds the transfer residual toner or the retransfer toner on the photosensitive drum 16 is disposed downstream of the transfer roller 25 on the peripheral surface of the photosensitive drum 16. The cleaning roll 24 has conductive brush bristles planted on the surface thereof, and is arranged so that the bristles come into contact with the photosensitive drum 16 so that a bias voltage is applied and the brush roll is driven to rotate. It has become.

  The cleaning roll 24 is rotated in the same direction as the rotation direction of the photosensitive drum 16 while a bias voltage having a negative polarity (-500 V in this embodiment) is applied during a period in which image formation is performed. As a result, the positive polarity retransfer toner adhering to the surface of the photosensitive drum 16 is attracted to the brush hair and collected.

  The cleaning roller 24 does not collect the negative transfer residual toner, and the photosensitive drum 16 is charged and exposed while adhering to the photosensitive drum 16, so that the transfer residual adhering to the non-image portion is performed. The toner is collected in the developing device 22 by rubbing with the carrier and toner attached to the developing roller 38 of the developing device 22.

  The retransfer toner collected by the cleaning roll 24 is discharged onto the photosensitive drum 16 in a cleaning mode executed during non-image formation.

  In the cleaning mode, a positive bias voltage (+500 V in this embodiment) is applied to the cleaning roll 24, and the rotation of the photosensitive drum 16 is followed in a direction different from the rotational direction of the photosensitive drum 16. It is rotated. As a result, the positive polarity retransfer toner held on the cleaning roll 24 is discharged onto the photosensitive drum 16.

  The retransfer toner discharged on the photosensitive drum 16 in this way is conveyed to the transfer position by the rotation of the photosensitive drum 16.

  In the cleaning mode, a negative bias voltage is applied to the transfer roller 25, and the retransfer toner conveyed to the transfer position is transferred onto the intermediate transfer belt 14 by the transfer roller 25, and the intermediate transfer belt. 14 to the cleaner 32 and scraped off by the blades 34 of the cleaner 32.

  FIG. 3 shows the configuration of the diffusion sensor 36. As shown in the figure, the diffusion sensor 36 is an LED that irradiates the surface of the intermediate transfer belt 14 (the surface on which the toner image is formed) with a light amount corresponding to the magnitude of the energized current. The regular reflection light is received when the LED irradiation unit 36A emits light to the irradiation unit 36A and the surface of the intermediate transfer belt 14 or a reference toner image of K color formed on the surface. The first photodiode 36B for detecting the amount of light and a reference toner image composed of any one of the three primary colors Y, M, and C formed on the surface of the intermediate transfer belt 14 by the LED irradiation unit 36A. And a second photodiode 36C that receives diffusely reflected light when irradiated with light and detects the amount of the diffusely reflected light. In the present embodiment, the incident angle of light on the surface of the intermediate transfer belt 14 is 60 °, but it is not always necessary to be 60 °.

  FIG. 4 is a block diagram showing a main configuration of the electrical system of the image forming apparatus 10 according to the present embodiment.

  As shown in FIG. 1, an image forming apparatus 10 includes a CPU (Central Processing Unit) 60, a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 64, an NVM (Non Volatile Memory) 66, a UI (user interface). ) A panel 68 and a communication interface 70 are included.

  The CPU 60 controls the overall operation of the image forming apparatus 10. The ROM 62 functions as a storage unit that stores in advance a control program for controlling the operation of the image forming apparatus 10, an image density estimation processing program to be described later, various parameters, and the like. The RAM 64 is used as a work area when executing various programs. The NVM 66 stores various types of information that must be retained even when the power switch of the apparatus is turned off.

  The UI panel 68 is configured by a touch panel display or the like in which a transparent touch panel is superimposed on a display. Various information is displayed on the display surface of the display, and desired information and instructions are input when the user touches the touch panel. Is done.

  The communication interface 70 is connected to a terminal device 72 such as a personal computer, and receives various information such as image information indicating an image formed on the paper 28 from the terminal device 72.

  The CPU 60, ROM 62, RAM 64, NVM 66, UI panel 68, and communication interface 70 are connected to each other via a system bus BUS. Therefore, the CPU 60 accesses the ROM 62, RAM 64, and NVM 66, displays various information on the UI panel 68, grasps the contents of user operation instructions on the UI panel 68, and communicates via the communication interface 70 from the terminal device 72. Various types of information are received.

  Further, the image forming apparatus 10 includes an image forming engine unit 74 that forms an image on the paper 28 by the LED xerography method. The image forming engine unit 74 includes the image forming unit 15, the transfer device 26, and the fixing device 30 described above.

  The image forming engine unit 74 is also connected to the system bus BUS. Therefore, the CPU 60 controls the operation of the image forming engine unit 74.

  In addition, the image forming apparatus 10 includes a current value detection unit 76 that detects a current value flowing through the LED irradiation unit 36A when light is emitted from the LED irradiation unit 36A. The current value detection unit 76 is also a system. Connected to bus BUS. Furthermore, the diffusion type sensor 36 described above is also connected to the system BUS. Therefore, the CPU 60 controls the operation of the LED irradiation unit 36A, acquires the amount of received light detected by each of the first photodiode 36B and the second photodiode 36C, and acquires the current value detected by the current value detection unit 76. And each.

  Incidentally, as schematically shown in FIG. 5 as an example, when a regular reflection type sensor 80 using a polarization beam splitter instead of the diffusion type sensor 36 is applied, the density correspondence value is calculated as follows as an example. It was.

  First, the surface of the intermediate transfer belt 14 on which no image is formed is irradiated with a predetermined amount of light from the LED irradiation unit 80A, and the light regularly reflected by the surface of the intermediate transfer belt 14 is irradiated by the photodiode 80B. The received light amount is stored in a predetermined memory (not shown).

  Next, a reference toner image is formed on the surface of the intermediate transfer belt 14, and a predetermined amount of light is irradiated to the reference toner image, and the light regularly reflected by the reference toner image is received by the photodiode 80B. Then, the light quantity β of the regular reflection light obtained in this way is stored in a predetermined memory (not shown).

  Finally, by dividing the light amount β by the light amount α, a density correspondence value indicating the ratio of the light amount β to the light amount α is calculated. Since the density correspondence value is a value corresponding to the density of the reference toner image, it is used for TC (toner concentration) control or density adjustment of an image formed on the surface of the intermediate transfer belt 14.

  As an example, as shown in Table 1 under the condition that the surface of the intermediate transfer belt 14 is not deteriorated and the light emission amount by the LED irradiation unit 80A is not reduced due to temperature change or deterioration with time. Further, the LED irradiating unit 80A irradiates the surface of the intermediate transfer belt 14 with light having a light amount of '100', and the amount of regular reflection light from the surface of the intermediate transfer belt 14 is '100'. When the amount of regular reflection light received from the reference toner image of each color of M, Y, and K is “50”, the density correspondence value is 0.5 (= 50/100) for each color toner.

また、一例として、中間転写ベルト１４の表面が劣化しており、かつ温度変化や経時劣化などに起因してＬＥＤ照射部８０Ａによる発光量が低下していない、との条件下で、表２に示すように、中間転写ベルト１４の表面に対してＬＥＤ照射部８０Ａにより光量が‘１００’の光を照射し、中間転写ベルト１４の表面からの正反射光の受光量が‘８０’であり、Ｃ，Ｍ，Ｙ，Ｋの各色の基準トナー像からの正反射光の受光量が‘４０’である場合、濃度対応値は、各色トナーとも０．５（＝４０／８０）となる。

As an example, Table 2 shows that the surface of the intermediate transfer belt 14 is deteriorated and the amount of light emitted by the LED irradiating unit 80A is not reduced due to temperature change or deterioration over time. As shown in the drawing, the surface of the intermediate transfer belt 14 is irradiated with light having a light amount of '100' by the LED irradiating unit 80A, and the amount of regular reflection light from the surface of the intermediate transfer belt 14 is '80'. When the amount of regular reflection light received from the reference toner images of C, M, Y, and K is “40”, the density correspondence value is 0.5 (= 40/80) for each color toner.

また、一例として、中間転写ベルト１４の表面が劣化しており、かつ温度変化や経時劣化などに起因してＬＥＤ照射部８０Ａによる発光量が低下している、との条件下で、表３に示すように、中間転写ベルト１４の表面に対してＬＥＤ照射部８０Ａにより光量が‘８０’の光を照射し、中間転写ベルト１４の表面からの正反射光の受光量が‘６４’であり、Ｃ，Ｍ，Ｙ，Ｋの各色の基準トナー像からの正反射光の受光量が‘３２’である場合、濃度対応値は、各色トナーとも０．５（＝３２／６４）となる。

Further, as an example, Table 3 shows that the surface of the intermediate transfer belt 14 is deteriorated and the amount of light emitted by the LED irradiating unit 80A is reduced due to temperature change or deterioration with time. As shown in the figure, the surface of the intermediate transfer belt 14 is irradiated with light having a light amount of '80' by the LED irradiating unit 80A, and the amount of regular reflection light from the surface of the intermediate transfer belt 14 is '64'. When the amount of regular reflection light received from the reference toner images of C, M, Y, and K is “32”, the density correspondence value is 0.5 (= 32/64) for each color toner.

このように、濃度対応値は、中間転写ベルト１４の表面の劣化やＬＥＤ照射部８０Ａの発光量の低下とは無関係な値であるため、当該濃度対応値を用いることにより、ＴＣ制御や中間転写ベルト１４の表面に形成された画像の濃度調整などが精度良く行われる。

As described above, the density correspondence value is a value irrelevant to the deterioration of the surface of the intermediate transfer belt 14 and the light emission amount of the LED irradiating unit 80A. Therefore, by using the density correspondence value, TC control or intermediate transfer is performed. The density of the image formed on the surface of the belt 14 is adjusted with high accuracy.

  On the other hand, when the above method is applied to the diffusion type sensor 36 that is the diffusion type sensor of the image forming apparatus 10 according to the present embodiment, the diffused light is substituted for the C, M, and Y instead of the detection of the regular reflection light. Will be applied.

  As an example, as shown in Table 4 under the condition that the surface of the intermediate transfer belt 14 is not deteriorated and the amount of light emitted by the LED irradiation unit 36A is not reduced due to temperature change or deterioration with time. Further, the surface of the intermediate transfer belt 14 is irradiated with light having a light amount of “100” by the LED irradiating unit 36A, and the amount of regular reflection light from the surface of the intermediate transfer belt 14 is “100”. When the amount of diffusely reflected light received from the reference toner images of M and Y is “50”, the density correspondence value is 0.5 (= 50/100) for each color toner.

また、一例として、中間転写ベルト１４の表面が劣化しており、かつ温度変化や経時劣化などに起因してＬＥＤ照射部３６Ａによる発光量が低下していない、との条件下で、表５に示すように、中間転写ベルト１４の表面に対してＬＥＤ照射部３６Ａにより光量が‘１００’の光を照射し、中間転写ベルト１４の表面からの正反射光の受光量が‘８０’であり、Ｃ，Ｍ，Ｙの各色の基準トナー像からの拡散反射光の受光量が‘５０’である場合、濃度対応値は、各色トナーとも０．６２５（＝５０／８０）となる。

Further, as an example, Table 5 shows the conditions that the surface of the intermediate transfer belt 14 is deteriorated and the light emission amount by the LED irradiation unit 36A is not reduced due to temperature change or deterioration with time. As shown in the figure, the surface of the intermediate transfer belt 14 is irradiated with light having a light amount of '100' by the LED irradiating unit 36A, and the amount of regular reflection light from the surface of the intermediate transfer belt 14 is '80'. When the amount of diffuse reflected light received from the reference toner images of C, M, and Y is “50”, the density correspondence value is 0.625 (= 50/80) for each color toner.

また、一例として、中間転写ベルト１４の表面が劣化しており、かつ温度変化や経時劣化などに起因してＬＥＤ照射部３６Ａによる発光量が低下している、との条件下で、表６に示すように、中間転写ベルト１４の表面に対してＬＥＤ照射部３６Ａにより光量が‘８０’の光を照射し、中間転写ベルト１４の表面からの正反射光の受光量が‘６４’があり、Ｃ，Ｍ，Ｙの各色の基準トナー像からの拡散反射光の受光量が‘４０’である場合、濃度対応値は、各色トナーとも０．６２５（＝４０／６４）となる。

Further, as an example, Table 6 shows the conditions that the surface of the intermediate transfer belt 14 is deteriorated and the amount of light emitted by the LED irradiation unit 36A is reduced due to temperature change, deterioration with time, and the like. As shown in the drawing, the surface of the intermediate transfer belt 14 is irradiated with light having a light amount of '80' by the LED irradiating unit 36A, and the amount of regular reflection light from the surface of the intermediate transfer belt 14 is '64'. When the amount of diffusely reflected light received from the reference toner images of C, M, and Y is “40”, the density correspondence value is 0.625 (= 40/64) for each color toner.

このように、濃度対応値は、中間転写ベルト１４の表面の劣化やＬＥＤ照射部３６Ａによる発光量の低下に応じて変化する。これは、受光量（正反射光）に対する受光量（拡散光）の割合としているからである。

As described above, the density correspondence value changes in accordance with the deterioration of the surface of the intermediate transfer belt 14 and the decrease in the light emission amount by the LED irradiation unit 36A. This is because the ratio of the amount of received light (diffused light) to the amount of received light (regularly reflected light) is used.

  In addition, when applying the technique in the regular reflection type sensor 80 to the diffusion type sensor, a method of applying the detection of the regular reflection light instead of the detection of the diffused light is also conceivable, but the detection of the regular reflection light is a diffusion type. This method cannot be applied to photodiodes because the light reception level is extremely low.

  Therefore, in the image forming apparatus 10 according to the present embodiment, the current value supplied to the LED irradiation unit 36A is detected, and the density correspondence value is calculated by the following equation (1). In equation (1), Z is a density-corresponding value, X is the amount of diffuse reflected light from the reference toner image of each color of C, M, and Y formed on the surface of the intermediate transfer belt 14, and Y is light. Each of the current values supplied to the LED irradiation unit 36A when irradiating the LED is shown.

Z = X ÷ Y (1)
Incidentally, in the image forming apparatus 10 according to the present embodiment, the image density estimation process is executed at a predetermined timing.

  Next, the operation of the image forming apparatus 10 when executing the image density estimation process will be described with reference to FIG. FIG. 6 is a flowchart showing a flow of processing of an image density estimation processing program executed by the CPU 60 of the image forming apparatus 10 when executing the image density estimation processing, and the program is predetermined in the ROM 62. Pre-stored in the storage area.

  In step 100 in the figure, by applying a current having a predetermined current value, the surface of the intermediate transfer belt 14 is irradiated with light of a light amount corresponding to the current value from the LED irradiation unit 36A, and the next step. At 102, the process waits until the light regularly reflected by the surface of the intermediate transfer belt 14 is received by the first photodiode 36B.

  In the next step 104, it is determined whether or not the amount of received light detected by the first photodiode 36B in step 102 is a predetermined amount of received light (hereinafter referred to as “reference received light amount”). When the determination is made, the process proceeds to step 106, while when the determination is negative, the process proceeds to step 108, the current value supplied to the LED irradiation unit 36 </ b> A is adjusted, and the process returns to step 102.

  In step 106, the current value detection unit 76 is caused to detect the current value supplied to the LED irradiation unit 36A, and in the next step 108, the current value detected by the current value detection unit 76 in step 106 is used as a reference. The current value is stored in the NVM 66.

  In the next step 110, a K-color reference toner image is formed on the surface of the intermediate transfer belt 14 by the image forming engine unit 74. In the next step 112, the LED irradiation is performed with the reference current value stored in the NVM 66 in the above step 108. By energizing the part 36A, light is emitted from the LED irradiation part 36A to the reference toner image of K color formed on the surface of the intermediate transfer belt 14 in step 110 described above.

  In the next step 114, the process waits until the light regularly reflected by the K reference toner image formed on the surface of the intermediate transfer belt 14 is received by the first photodiode 36B and the amount of received light is detected.

  In the next step 116, the received light amount detected by the first photodiode 36B in the above step 114 with respect to the reference received light amount by dividing the received light amount received by the first photodiode 36B in the above step 114 by the reference received light amount. A density correspondence value indicating the ratio of the above is calculated. Instead of the reference amount of received light, the density corresponding value for the reference current value may be calculated by dividing by the reference current value.

  For example, as shown in Table 7 under the condition that the surface of the intermediate transfer belt 14 is deteriorated and the amount of light emitted by the LED irradiating unit 36A is reduced due to temperature change or deterioration over time. The light is received from the LED irradiation unit 36A to the surface of the intermediate transfer belt 14 on which no image is formed so that the amount of light received by the first photodiode 36B becomes the reference amount of light received (here, “100”). The current value applied to the LED irradiation unit 36A when irradiating is “125”, and the LED irradiation unit 36A is energized with the current value to emit light from the LED irradiation unit 36A to the reference toner image of K color. When the amount of received light detected by the first photodiode 36B upon irradiation is “50”, the density correspondence value is 0.5 (= 50/100).

次のステップ１１８では、上記ステップ１１６で算出した濃度対応値をＮＶＭ６６に記憶する。

In the next step 118, the density correspondence value calculated in step 116 is stored in the NVM 66.

  In the next step 120, the image forming engine unit 74 forms a reference toner image having one of the three primary colors C, M, and Y on the surface of the intermediate transfer belt 14. In the next step 122, By energizing the LED irradiation unit 36A with the reference current value stored in the NVM 66 in step 108, the LED irradiation unit 36A emits light to the reference toner image formed on the surface of the intermediate transfer belt 14 in step 120. .

  In the next step 124, the process waits until the light diffusely reflected by the reference toner image formed on the surface of the intermediate transfer belt 14 is received by the second photodiode 36C and the amount of received light is detected.

  In the next step 126, the reference current value stored in the NVM 66 in the above step 108 is obtained by dividing the received light amount detected by the second photodiode 36C in the above step 124 by the reference current value stored in the NVM 66 in the above step 108. On the other hand, a density corresponding value indicating the ratio of the amount of received light detected by the second photodiode 36C in step 124 is calculated.

  For example, as shown in Table 8, under the condition that the surface of the intermediate transfer belt 14 is deteriorated and the amount of light emitted by the LED irradiating unit 36A is reduced due to temperature change or deterioration over time. The light emitted from the LED irradiator 36A to the surface of the intermediate transfer belt 14 on which no image is formed so that the amount of received light detected by the first photodiode 36B becomes the reference amount of received light (here, “100”). The current value applied to the LED irradiation unit 36A when irradiating is “125”, and the LED irradiation unit 36A is energized with the current value, whereby the LED irradiation unit 36A applies any YMC color reference toner image. When the received light amount detected by the second photodiode 36C when the light is irradiated is “62.5”, the density correspondence value is 0.5 (= 62.5 / 125).

次のステップ１２８では、上記ステップ１２６で算出した濃度対応値をＮＶＭ６６に記憶する。

In the next step 128, the density correspondence value calculated in step 126 is stored in the NVM 66.

  In the next step 130, it is determined whether or not the processing from step 120 to step 128 has been completed for all three primary colors C, M, and Y. If YES, the routine proceeds to step 132.

  In step 132, the UI panel 68 displays the density corresponding values of C, M, Y, and K stored in the NVM 66, and displays a screen asking the user whether or not to execute TC control. Let In the present embodiment, the visual display by the UI panel 68 is described as an example. However, the present invention is not limited to this, and is a permanent visual display by an image forming apparatus such as a printer, and an audible display by a speech synthesizer. Also good.

  In the next step 134, it is determined whether or not information for instructing execution of the TC control is input to the UI panel 68. If the determination is negative, the process proceeds to step 136 while the determination is affirmative. If so, the process proceeds to step 138.

  In step 136, it is determined whether or not a predetermined time (30 seconds in this case) has elapsed since the execution of the process in step 132. If a negative determination is made, the process returns to step 134, while an affirmative determination is made. In this case, the image density estimation processing program is terminated.

  On the other hand, in step 138, for each color of C, M, Y, and K, the density corresponding value stored in the NVM 66 is included in the toner for the toner in the developing unit 22 so as to be a predetermined value. After performing control (TC control) for adjusting the ratio of toner particles, the image density estimation processing program is terminated.

  As mentioned above, although this invention was demonstrated using the said embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various changes or improvements can be added to the above-described embodiment without departing from the gist of the invention, and forms to which the changes or improvements are added are also included in the technical scope of the present invention.

  Moreover, the said embodiment does not limit the invention described in the claim, and all the combinations of the characteristics demonstrated in the said embodiment are essential for the solution means of invention. Is not limited. The above-described embodiments include various stages of the invention, and various inventions are extracted by combinations according to situations in a plurality of disclosed constituent requirements. Even if some constituent requirements are deleted from all the constituent requirements shown in the above-described embodiment, as long as an effect is obtained, a configuration in which these some constituent requirements are deleted can be extracted as an invention.

  For example, in the above-described embodiment, an example in which the TC control is performed using the density correspondence value is described. However, the present invention is not limited to this, and the bias voltage applied to the transfer roller 25 is adjusted using the density correspondence value. Accordingly, the image density formed on the surface of the intermediate transfer belt 14 may be adjusted, or by adjusting the bias voltage applied to the roller 26A when the toner image is transferred from the intermediate transfer belt 14 to the paper 28. The image density formed on the paper 28 may be adjusted.

  In the above embodiment, the ratio of the amount of received light detected by the second photodiode 36C with respect to the reference current value is the density-corresponding value. However, the present invention is not limited to this, and is detected by the first photodiode 36 with respect to the reference current value. The ratio of the received light amount may be a density correspondence value.

  In the above embodiment, the light reception amount detected by the first photodiode 36B and the second photodiode 36C is used in calculating the density correspondence value. However, the present invention is not limited to this, and the first photodiode 36B and the second photodiode 36 A physical quantity corresponding to the amount of light received by each of the diodes 36C (for example, a current value flowing through each photodiode when reflected light is received) may be used.

  In the above-described embodiment, an example of a case in which the density-corresponding value is displayed on the UI panel 68 has been described. However, the present invention is not limited to this. Table information indicating the correspondence relationship with the particle ratio is stored in the ROM 62 in advance, and the CPU 60 calculates the ratio of the toner particles contained in the toner to the toner in the developing device 22 using the table information from the density correspondence value. Derived and the derived ratio may be displayed. Further, the CPU 60 may derive the ratio of the toner particles contained in the toner to the toner in the developing device 22 from the density correspondence value using an arithmetic expression, and display the derived ratio. The display includes a visible display by an image display device such as the UI panel 68, a permanent visible display by an image forming device such as a printer, and an audible display by a speech synthesizer.

  In addition, the configuration of the image forming apparatus 10 described in the above embodiment (see FIG. 1) and the configuration of the image forming unit 15 (see FIG. 2) are merely examples, and are within the range not departing from the gist, depending on the situation. Needless to say, it may be changed.

  The processing flow of the image density estimation processing program described in the above embodiment (see FIG. 6) is also an example, and unnecessary steps are deleted or new steps are added within a range not departing from the gist. Needless to say, the processing order may be changed.

10 Image forming apparatus 14 Intermediate transfer belt (image carrier)
22 Developer (Developer supply means)
36A LED irradiation unit (irradiation means)
36B First photodiode (regular reflection light detection means)
36C second photodiode (diffuse reflected light detecting means)
60 CPU (calculation means, adjustment means, derivation means)
68 UI panel (display means)
76 Current value detection unit (current detection means)

Claims (5)

An image carrier for holding an image formed on the surface;
Irradiation means for irradiating the image holding body with a light amount corresponding to the magnitude of the energized current;
Diffuse reflected light for detecting a physical quantity indicating the amount of diffuse reflected light when the irradiation means irradiates a reference image composed of any of the three primary colors formed on the surface of the image carrier with the irradiation means. Detection means;
Regular reflection light detection means for detecting a physical quantity indicating the amount of regular reflection light when the irradiation means irradiates light on the surface of the image carrier,
Current detection means for detecting the magnitude of current when the irradiation means is energized so that the physical quantity detected by the specular reflection light detection means becomes a predetermined physical quantity;
When the reference image is irradiated with light having a magnitude detected by the current detection means with respect to the magnitude of the current detected by the current detection means, the diffuse reflection detection means or the Calculating means for calculating the proportion of the physical quantity detected by the regular reflection light detecting means;
An image density estimation apparatus including:   The calculation means further applies a current of a magnitude detected by the current detection means with respect to the predetermined physical quantity to emit light to a black reference image formed on the surface of the image carrier. The image density estimation apparatus according to claim 1, wherein the ratio of the physical quantity detected by the specular reflection light detection means upon irradiation is calculated. The image density estimation apparatus according to claim 1 or 2,
Developer supplying means for supplying a developer comprising colored particles and magnetic particles to the surface of the image carrier when forming an image on the surface of the image carrier;
The ratio of the colored particles contained in the developer to the developer supplied to the surface of the image carrier by the developer supply means so that the ratio calculated by the calculation means becomes a predetermined value. Adjusting means for adjusting
An image forming apparatus including:   The image forming apparatus according to claim 3, further comprising display means for displaying information indicating the ratio calculated by the calculation means. A derivation unit for deriving a ratio of the colored particles contained in the developer to the developer supplied by the developer supply unit based on the ratio calculated by the calculation unit;
The image forming apparatus according to claim 4, wherein the display unit further displays a ratio derived by the deriving unit.

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