JP2005189493A - Image forming device, process cartridge, image forming method, computer program and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To comprehensively determine deterioration of developer. <P>SOLUTION: The following processes are provided, i.e., a picture quality detecting pattern forming process (S107) in which a picture quality detecting pattern is formed on an image carrier, a computing process (S109) in which reflected light quantity from the picture quality detecting pattern formed in the picture quality detecting pattern forming process is detected (S108) and an image characteristic is computed, a determination process ( S110) in which degree of picture quality deterioration is determined from the image characteristic computed in the computing process, a density detecting pattern forming process (an S112) which is used to form a density detecting pattern on the image carrier when the degree of picture quality deterioration determined in the determination process is equal to or more than the preset degree, a density detecting process (S113) which is used to respectively detect the density of the density detecting pattern formed in the density detection pattern forming process and the density of the portion where the density detecting pattern is not formed and a developer deterioration determination process (S115) which is used to determine the degree of deterioration of the developer based on the densities detected in the density detecting process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention has a function of determining deterioration of a developer, and determines an image forming apparatus that forms a visible image on a recording medium using toner, a process cartridge used in the image forming apparatus, and deterioration of the developer The present invention relates to an image forming method having a developer deterioration judgment function, a computer program for realizing the image forming method, and a recording medium on which the computer program is recorded.

  As this type of technology, for example, the inventions disclosed in Patent Documents 1 to 3 are known. Among them, in Patent Document 1, a uniformly charged photoconductor is developed with a developer, and a toner adhesion amount (referred to as fog amount) adhering to the photoconductor is detected by an adhesion amount sensor. A latent image formed on the body under a predetermined condition is developed with a developer, and the toner adhesion amount (development amount) of the reference toner image adhering to the photoconductor is detected by an adhesion amount sensor, and the humidity around the photoconductor is detected. A technique for determining whether or not the developer has passed its life from the fogging amount, the developing amount, and the humidity is disclosed.

  Patent Document 2 discloses a humidity measuring unit that measures relative humidity in an image forming apparatus, a toner concentration detecting unit that detects a toner concentration of a developer contained in the developing device, and a toner concentration detecting unit. Based on the output, toner density adjusting means for maintaining a constant toner density, potential measuring means for detecting the potential of the surface of the image carrier, and an image for forming a reference patch having a predetermined area ratio on the image carrier Exposure control means for controlling the exposure apparatus so as to emit light; and on the downstream side of the developing device in the moving direction of the surface of the image carrier, on the upstream side of the potential measuring means, and on the image carrier The static elimination exposure means for extinguishing the potential of the reference, a calculation means for comparing the potential measured at the reference patch portion with a reference value, and a reference value for comparison with the measurement value by the calculation means corresponding to the value of relative humidity Memory The image forming apparatus is disclosed having a stage.

  Further, in Patent Document 3, at least two of the developing units including the first and second developing units are composed of a two-component developing unit, and the image forming apparatus describes the latent image potential of the formed maximum density patch. , A means for measuring the density of the developed patch, and a means for automatically changing the developer of the two-component developing means in accordance with the measured density of the patch. There is disclosed a multicolor image forming apparatus including a means for discharging a developer, a means for supplying a carrier to a two-component developing means, and a means for supplying toner.

As a technique for detecting the deterioration of the developer by a method other than detecting the toner density attached to the image bearing member, the inventions disclosed in Patent Documents 4 to 8 are known. Among these, Patent Document 4 discloses an invention in which the potential of a toner image on an image carrier is detected, and the agent deterioration is judged from the detection result. Patent Document 5 discloses an invention in which a counter electrode is placed in a developing machine and a resistance value of the developer is detected to determine agent deterioration. Patent Document 6 discloses an invention in which a constant voltage bias power source is connected to a developing roller, a developing bias current supplied to the developing roller is detected, and agent deterioration is judged from a developing bias current value corresponding to a non-image portion. ing. Patent Document 7 discloses an invention in which a voltage is applied to a counter electrode arranged at a distance from the developing roller, and a current flowing through the developer attached to the counter electrode is detected to determine agent deterioration. Further, Patent Document 8 discloses an invention in which a magnetic permeability sensor for detecting agent deterioration is arranged in a developing machine, and agent deterioration is judged from the sensor output when the toner concentration is a reference value.
JP-A-6-266223 JP-A-8-123263 Japanese Patent Laid-Open No. 10-186831 JP 2001-222140 A JP-A-6-102743 JP 60-112076 A Japanese Patent Laid-Open No. 6-083179 JP-A-6-130818

  Conventionally, detection of agent deterioration in an electrophotographic apparatus is performed by creating a toner image on an image carrier, detecting a physical quantity proportional to the density of the toner image, and comparing the detection result with a reference value measured in advance. The method of judging agent deterioration is taken. For example, in the invention described in Japanese Patent Application Laid-Open No. H10-228707, the toner adhesion amount of the image area and the non-image area on the photosensitive member is measured, and the deterioration of the developer is determined in consideration of the environment (humidity). In the invention described in Patent Document 2, the charging potential, the developing bias, the light amount of the exposure device, and the toner density in the developing device are controlled to be constant, and in this state, a reference patch is formed on the image carrier, and the formed toner layer The potential of the toner is measured and compared with a reference value to determine the degree of toner deterioration. In the invention described in Patent Document 3, the latent image potential of the maximum density patch on the image carrier is confirmed, the density of the developed patch is measured, the developer is discharged according to the measurement result, and the carrier and toner are removed. Supply. In these three examples, in any case, the density of the patch on the image carrier is measured, and the agent deterioration is determined from the measurement result. The determination of deterioration is performed by comparison with a reference value measured in advance. In these examples, only the concentration of the patch is used as an indicator of agent deterioration.

  However, agent deterioration affects not only the density on the image carrier but also the image quality. Therefore, image quality should also be used as an indicator of agent deterioration. In the above example, the relationship between the agent deterioration and the image quality can be examined when determining the reference value used for the determination of the agent deterioration. The relationship is obtained in advance through experiments or the like. However, it is well known that the environment in which the image forming apparatus is installed and how it is used are diverse, and the characteristics such as density and image quality are actually greatly affected by temperature and humidity. It is impossible to uniquely determine in advance the relationship between agent deterioration and image quality in all situations. Therefore, there is a possibility that the agent replacement is performed because it is determined that the agent is deteriorated even though the image quality is not actually deteriorated. In this case, the agent exchange is unnecessary, and rather than taking time and effort to the user, a financially wasteful burden is applied.

  Patent Documents 4 to 8 disclose inventions for judging agent deterioration without using a toner image on an image carrier. However, in these inventions, the image quality of a toner image is not viewed. It does not judge agent deterioration in relation to

  On the other hand, it is known that what constitutes image quality includes not only the gradation and solid density but also many other factors. Among them, “graininess (image roughness that appeals to human vision)” can be cited as an element that greatly affects image quality. In order to achieve high image quality in the electrophotographic process, a technique for maintaining this granularity in a low state is essential. This graininess is largely determined by the initial image forming conditions, but in addition to this, it is known that the graininess changes (deteriorates) continually. The cause of this change over time may be due to environmental fluctuations such as temperature and humidity, or may be due to deterioration of the developer or the photoreceptor. Therefore, in order to continue to maintain high-quality images over time, it is necessary to detect the image quality that has a strong correlation with graininess or graininess by some means, and change the image formation conditions based on the detection result. is required.

However, no means have been disclosed so far for a means for detecting image quality by paying attention to graininess. Graininess is density unevenness in a plane space where an image is formed, and about 1 [cycle / mm] when human visual characteristics are taken into consideration.
With a peak of 0 [cycle / mm] to about 10 [cycle / mm]
The graininess is determined by density unevenness having a spatial frequency in the range of
About 1 [cycle / mm]
The peak is about 0.2 [cycle / mm] to about 4 [cycle / mm].
Density unevenness having a spatial frequency in the range is particularly problematic.

  Therefore, in order to obtain such granularity information related to human visual characteristics, the means for detecting density unevenness existing at the spatial frequency described above and the density unevenness signal detected by this means are used as the spatial frequency characteristics. It is considered that it is desirable to evaluate the image quality using such means and to evaluate the agent deterioration in relation to the agent deterioration.

  Therefore, an object of the present invention is to enable comprehensive determination of agent deterioration.

  Another object is to enable determination at low cost when comprehensively determining agent deterioration.

  Further, another object is to determine the deterioration of the agent and to determine whether or not to form an image in accordance with this determination.

  In order to achieve the above object, the first means has developer deterioration degree detecting means for detecting the degree of developer deterioration, and forms an image formed on the recording medium by a toner image developed by the developer. In the apparatus, image quality detection means for detecting the image quality of the image formed on the image carrier, and control for judging whether or not to replace the developer based on the detection results of the developer deterioration degree detection means and the image quality detection means Means.

  The second means is the first means, wherein the image quality detecting means is formed by an image quality detecting pattern forming means for forming an image quality detecting pattern on the image carrier and the image quality detecting pattern forming means. Reflected light quantity detection means for detecting the reflected light quantity from the image quality detection pattern in a minute region, and calculation for calculating the characteristics of the image formed on the image carrier based on the reflected light quantity detected by the reflected light quantity detection means Means.

  According to a third means, in the first means, the image quality detecting means is provided opposite to the dedicated transfer member to which the pattern formed on the image carrier is transferred, and the dedicated transfer member. A unit comprising: a reflected light amount detection unit; and a calculation unit that calculates the characteristics of the image formed on the transfer member based on the reflected light amount detected by the reflected light amount detection unit. .

  A fourth means is the first to third means, wherein the control means controls the image quality based on a detection result of the image quality detection means.

  A fifth means is characterized in that, in the fourth means, the image quality control is performed by combining at least any two of a developing bias, a developing sleeve linear velocity, an LD output, and a charging grid bias.

  The sixth means further comprises density detection pattern forming means for forming a density detection pattern on the image carrier in the first to third means, wherein the image quality detection means is formed by the density detection pattern formation means. The toner density is detected from the formed density detection pattern.

  A seventh means is the sixth means, wherein the image quality detecting means detects not only the density of the density detection pattern but also the density of the non-image portion of the image carrier on which the density detection pattern is not formed. It is characterized by that.

  The eighth means further comprises a secular change detecting means for detecting a secular change of the image carrier in the first to seventh means, and the control means detects the secular change by the secular change detecting means, Detection by the developer deterioration degree detection means and the image quality detection means is executed.

  According to a ninth means, in the eighth means, the secular change detected by the secular change detecting means is caused by scratches, dirt, filming of the image bearing member, potentials of the image portion and the non-image portion, film thickness, and remaining. It includes at least one of potentials.

  According to a tenth means, in the eighth or ninth means, the secular change detecting means detects a secular change state based on a preset threshold value, and the secular change affects the image quality. When the control means determines, the control means changes the threshold value and determines again the state of aging and the influence on the image quality.

  An eleventh means is characterized in that, in the first to ninth means, the image carrier is any one of a photosensitive member, an intermediate transfer member, a recording paper conveying member, and a dedicated transfer member.

  A twelfth means includes a display means for displaying at least one result of the detection result of the secular change detection means, the detection result of the image quality detection means and the judgment result of the control means in the first to eleventh means. It is characterized by.

  A thirteenth means is characterized in that, in the twelfth means, the control means causes the display means to display whether or not to continue image formation after displaying the result.

  In a fourteenth aspect, in the first to eleventh means, at least one result of the detection result of the secular change detection means, the detection result of the image quality detection means, and the determination result of the control means is transmitted to an external device. Means are provided.

  The fifteenth means is characterized in that in any of the first to eleventh means, the user has an input means for inputting an instruction to execute image formation even when the image quality cannot be guaranteed.

  The sixteenth means has a developer deterioration degree detecting means for detecting the degree of deterioration of the developer, and is a process cartridge used in an image forming apparatus for forming a toner image developed by the developer on a recording medium. The image forming apparatus is provided with image quality detecting means for detecting the image quality of the image formed on the image carrier, and the control means provided on the image forming apparatus side detects the detection result of the developer deterioration degree detecting means and the image quality detecting means. Based on this, it is determined whether to replace the developer.

  A seventeenth means is the image forming apparatus according to the sixteenth means, wherein the image quality detecting means is formed by an image quality detecting pattern forming means for forming an image quality detecting pattern on the image carrier and the image quality detecting pattern forming means. Reflected light quantity detection means for detecting the reflected light quantity from the image quality detection pattern in a minute region, and calculation for calculating the characteristics of the image formed on the image carrier based on the reflected light quantity detected by the reflected light quantity detection means Means.

  In an eighteenth means according to the sixteenth means, the image quality detecting means is provided opposite to the dedicated transfer member to which the pattern formed on the image carrier is transferred, and the dedicated transfer member. A unit comprising: a reflected light amount detection unit; and a calculation unit that calculates the characteristics of the image formed on the transfer member based on the reflected light amount detected by the reflected light amount detection unit. .

  A nineteenth means includes a developer deterioration degree detecting means for detecting a degree of developer deterioration, and in the image forming method for forming a toner image developed by the developer on a recording medium, on the image carrier. An image quality detection pattern forming step for forming an image quality detection pattern on the image, a calculation step for calculating an image characteristic by detecting a reflected light amount from the image quality detection pattern formed in the image quality detection pattern forming step, and A determination step for determining the degree of image quality deterioration from the image characteristics calculated in the calculation step, and an image quality control for executing image quality control when the degree of image quality deterioration determined in the determination step is smaller than a preset degree. And a process.

  The twentieth means includes a developer deterioration degree detecting means for detecting the degree of deterioration of the developer, and in the image forming method for forming a toner image developed by the developer on the recording medium, on the image carrier. An image quality detection pattern forming step for forming an image quality detection pattern on the image, a calculation step for calculating an image characteristic by detecting a reflected light amount from the image quality detection pattern formed in the image quality detection pattern forming step, and A determination step for determining the degree of image quality deterioration from the image characteristics calculated in the calculation step, and a density detection on the image carrier when the degree of image quality deterioration determined in the determination step is greater than or equal to a preset degree. A density detection pattern forming step for forming a pattern for density, a density detection pattern formed in the density detection pattern formation step, and a portion where the density detection pattern is not formed Characterized in that it includes a concentration detection step for detecting a concentration, respectively, and a step agent degradation determination to determine the degree of deterioration of the developer based on the concentration detected by the concentration detection step.

  The twenty-first means further includes a time-dependent change detecting step for detecting a time-dependent change of the image carrier and a time-dependent change detecting step before performing the image quality detection pattern forming step in the nineteenth or twentieth means. A temporal change determination step for determining whether there is a temporal change based on the detected result, and whether the temporal change affects image quality when it is determined that there is a temporal change in the temporal change determination step An image quality influence determining step for determining whether or not the influence on the image quality cannot be eliminated even if the determination criteria are changed in the image quality influence determining step, Or a replacement instruction process for displaying.

  A twenty-second means includes a time-dependent change detecting step for detecting a time-dependent change of the image carrier and a time-dependent change detecting step before the image quality detection pattern forming step in the nineteenth or twentieth means. A temporal change determination step for determining whether there is a temporal change based on the detected result, and whether the temporal change affects image quality when it is determined that there is a temporal change in the temporal change determination step An image quality influence determining step for determining whether the image quality influence determining step has changed the criteria for determination, and if the influence on the image quality is eliminated, the process proceeds to the image quality detection pattern forming step. Features.

  A twenty-third means further comprises a temperature / humidity detecting step for detecting the temperature and humidity in the device in the twentieth means, and the temperature / humidity detected in the temperature / humidity detecting step in the agent deterioration determining step. The degree of deterioration of the developer is determined from the density detected in the density detection step.

  According to a twenty-fourth means, in the twentieth or twenty-third means, there is provided a transmitting step of transmitting the determination result of the agent deterioration determining step to an external device.

  The twenty-fifth means is characterized in that, in the twentieth or twenty-third means, a display step of displaying the judgment result of the agent deterioration judgment step on a display means.

  The twenty-sixth means displays in any one of the twentieth, twenty-third, twenty-fourth and twenty-fifth means whether or not to continue image formation regardless of the determination result of the agent deterioration determining step, and performs image formation. An image forming process is provided for forming an image when an instruction to continue is issued.

  The twenty-seventh means is characterized in that a computer program includes a procedure for executing the image forming method according to any one of the nineteenth to twenty-sixth means by a computer.

  The twenty-eighth means is characterized in that the computer program according to the twenty-seventh means is read by a computer and recorded on a recording medium so as to be executable.

  In the embodiments described later, the developer deterioration degree detecting means is a control circuit CON including a CPU, a RAM and a ROM, and the image carrier is a photosensitive member 61, an intermediate transfer belt 5, a recording paper conveying belt 69, and a dedicated transfer roller. 109a, the image quality detection means and the aged deterioration detection means are the sensor 100a, the arithmetic circuit 130 and the control circuit CON, or the sensor unit 100c and the control circuit CON, the control means is the control circuit CON, and the image quality detection pattern formation means is the control circuit. CON, the charging unit 62, the exposure unit 65, the developing unit 63, and in addition to these, the primary transfer roller 53 and / or the secondary transfer roller 51. The reflected light amount detection means is a light emitting element 101, a light receiving element 103, lenses 102, 104. , 106 and fibers 105, 107, or sensor head 108, the calculation means is In the arithmetic circuit 130 or the arithmetic unit 130a, the dedicated transfer member is in the dedicated transfer roller 109a, and the density detection pattern forming means is the control circuit CON, the charging unit 62, the exposure unit 65 and the developing unit 63, or in addition to these, primary transfer. The roller 53 and / or the secondary transfer roller 69, the display unit and the input unit correspond to the operation display unit 1a, and the transmission unit corresponds to the external I / F 1e.

  Also, the image quality detection pattern formation process is in step S107, the calculation process is in steps S108 and S109, the determination process is in step S110, the image quality control process is in step S111, and the density detection pattern formation process is in step S112. The process is in step S113, the agent deterioration determination process is in step S115, the temporal change detection process is in step S101, the temporal change determination process is in step S102, the image quality influence determination process is in step S103, and the replacement instruction process is in step S106. The temperature / humidity detection process corresponds to step S114, the transmission process to be transmitted corresponds to steps S116 and S119, the display process corresponds to steps S117 and S120, and the image formation process corresponds to steps S122 and S123.

  According to the present invention, the image quality forming apparatus is provided with means for detecting, calculating, and determining the image quality, and the agent deterioration determination is performed when the image quality deterioration determining means determines that the image quality has deteriorated. Can be determined.

  Further, since the image quality detection means also serves as the density detection means, it is possible to make a determination at a low cost when comprehensively determining the agent deterioration.

  Further, it is possible to determine whether or not to form an image by determining the deterioration of the agent and taking into account the deterioration in image quality due to this determination.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, equivalent parts are denoted by the same reference numerals, and overlapping descriptions are omitted as appropriate.

1. Outline of Image Quality Detection First, an outline of image quality detection will be described with reference to FIGS.

1.1 Overall Configuration FIG. 1 is a diagram showing a schematic configuration of an entire image forming apparatus as an object of image quality detection, and FIG. 2 is a tandem arrangement of photosensitive drums as latent image carriers used in the image forming apparatus of FIG. FIG. 2 is a diagram showing an image forming unit of the dry two-component development type full-color image forming apparatus.

  In FIG. 1, an image forming unit 1 is disposed substantially at the center of a tandem type color image forming apparatus MFP, and a sheet feeding unit 2 is disposed immediately below the image forming unit 1. A paper feed tray 21 is provided. A scanner unit 3 for reading a document is disposed above the image forming unit 1. On the downstream side (left side in the figure) of the image forming unit 1 in the paper conveyance direction, a paper discharge storage unit, a so-called paper discharge tray 4 is provided, on which the discharged image-formed recording paper is stacked.

  In the image forming unit 1, as shown in FIG. 2, a plurality of yellow (Y), cyan (C), magenta (M), and black (K) prints are formed above the intermediate transfer belt 5 formed of an endless belt. An image unit 6 is juxtaposed. In each image forming unit 6, along the outer periphery of a drum-shaped photoconductor (photosensitive drum) 61 provided for each color, a charging charger 62, an exposure unit 65, a developing unit 63, a cleaning unit 64, an eraser (QL) ) 67 and the like are arranged. The charging charger 62 performs charging processing on the surface of the photoreceptor 61, and the exposure unit 65 irradiates the laser light from the writing unit 7 that irradiates the surface of the photoreceptor 61 with image information with laser light. The developing unit 63 develops and visualizes the electrostatic latent image formed by exposing the surface of the photoreceptor 61 with toner, and the cleaning unit 64 removes and collects the toner remaining on the surface of the photoreceptor 61 after the transfer.

  As an image forming process, an image for each color is formed on the intermediate transfer belt 5, and four colors are superimposed on the intermediate transfer belt 5 to form one color image. At this time, first, the yellow (Y) toner is developed in the yellow (Y) image forming unit, and transferred to the intermediate transfer belt 5 by the primary transfer device (roller) 66. Next, cyan toner is developed and transferred onto the intermediate transfer belt 5 in the cyan (C) image forming unit. Next, the magenta (M) image forming unit develops the magenta toner and transfers it to the intermediate transfer belt 5. Finally, the black (K) toner is developed and transferred onto the intermediate transfer belt 5. A full-color toner image in which four colors are superimposed is formed. Then, the four color toner images transferred onto the intermediate transfer belt 5 are transferred to the recording paper 20 fed from the paper feeding unit 2 by the secondary transfer device (roller) 51 and fixed by the fixing unit 8. After that, the paper is discharged onto a paper discharge tray 4 by a paper discharge roller or conveyed to a duplex unit 9. During double-sided printing, the conveyance path is branched by the branching unit 91, and the recording paper 20 is reversed via the double-sided unit 9. Then, the paper skew is corrected by the registration roller 23, and the image forming operation on the back surface is performed in the same manner as the image forming operation on the front surface. On the other hand, after the full-color toner image is transferred, the toner remaining on the surface of the intermediate transfer belt 5 is removed and collected by the cleaning unit 52. Reference numeral 92 denotes a paper feed reverse path from the duplex unit 9. In FIG. 2, Y, C, M, and K representing colors are added after the symbols of the respective parts to distinguish the image forming parts of the respective colors.

  In the paper feeding unit 2, unused recording paper 20 is stored in the paper feeding tray 21, and the uppermost recording paper 20 is picked up by the pickup roller 25, and the vertical feeding path 27 is moved by the rotation of the paper feeding roller 26. Then, it is conveyed to the registration roller 23 side. The registration roller 23 temporarily stops the conveyance of the recording paper 20, and sends out the recording paper 20 at a timing so that the positional relationship between the toner image on the intermediate transfer belt 5 and the leading edge of the recording paper 20 is a predetermined position.

  In the scanner unit 3, the first and second traveling bodies on which the document illumination light source and the mirror are mounted reciprocate to read and scan the document placed on the contact glass. The image information scanned by the traveling body is condensed on the imaging surface of the CCD installed behind by the lens, and is read as an image signal by the CCD. The read image signal is digitized and subjected to image processing. Then, based on the image-processed signal, optical writing is performed on the surface of the photosensitive member 61 by light emission of the laser diode LD in the writing unit 7 to form an electrostatic latent image. The optical signal from the LD reaches the photosensitive member 61 via a known polygon mirror or lens. An automatic document feeder (ADF) 36 that automatically feeds the document onto the contact glass is attached to the upper portion of the scanner unit 3.

  The color image forming apparatus MFP according to the present embodiment performs a control (not shown) in addition to a function as a so-called digital color copying machine that scans an original by optical scanning, digitizes it, and copies it onto a sheet as described above. This is a multi-function image forming apparatus having a facsimile function for sending and receiving image information of a document to and from a remote place, and a so-called printer function for printing image information handled by a computer on paper. An image formed by any function forms an image on the recording paper 20 by a similar image forming process, and is discharged to one discharge tray 4 and stored. When image quality deterioration is detected and image quality deterioration is confirmed, appropriate image forming condition control can be performed automatically, so there is no need to immediately replace the developer or photoconductor, and the developer. And the lifetime of the photoconductor can be extended to the limit.

  In FIG. 1, a full color machine of a four-tandem type intermediate transfer system is shown as an example of the image forming apparatus according to the present invention, but this is only drawn as a representative example of the image forming apparatus and will be described later. As described above, the present invention may be applied to a full-color machine such as a 4-drum tandem direct transfer system or a 1-drum intermediate transfer system, a direct transfer monochrome machine, or an image forming apparatus of another system.

1.2 Image Quality FIGS. 3 and 4 show a halftone image formed on the recording paper 20 by the image forming apparatus of FIGS. 1 and 2 having a 600 dpi writing system (the size of one halftone dot is “2 pixels × 2 pixels ") is an enlarged photograph (for convenience of description, binarization processing is performed at the time of photographing). FIG. 3 shows an initial image PT1, and FIG. 4 shows a very long period under certain conditions. An image PT2 after printing is shown. As shown in FIG. 3, the halftone image PT1 which was initially uniform becomes a halftone image PT2 having a rough feeling due to various factors such as the deterioration of the developer and the photoreceptor in the long-term image forming process. I'm stuck. Such a feeling of roughness can be quantified as a spatial frequency characteristic of fine density unevenness, and is expressed as a characteristic value such as “granularity”, for example.

That is, an image with a high degree of granularity (poor graininess) shows an image with a large roughness, and an image with a low degree of granularity (good graininess) shows a uniform image with little feeling of roughness. However, not all of the density unevenness gives a sense of roughness that appeals to the eye, and the image quality of the printed image need not be felt when a human visually observes it. FIG. 5 shows visual spatial frequency characteristics of an average subject regarding density unevenness. As described above, the spatial frequency at which density unevenness is perceived by human vision is about 0 [cycle / mm] to about 10 [cycle / mm] with a peak of about 1 [cycle / mm] as described above.
It is known that it is limited to the spatial frequency region of the range.

1.3 Image Quality Detection Device FIG. 6 is a diagram showing a schematic configuration of an image quality detection device that measures fine density unevenness of an image. In the figure, an image quality detection apparatus 100 is based on a light reflection type sensor (photo reflector) 110, an amplification circuit 120 for amplifying an electric signal from the light reflection type sensor 110, and a signal amplified by the amplification circuit 120. And an arithmetic circuit 130 as arithmetic means for performing predetermined arithmetic processing, and a signal generation circuit 140 as signal generation means for generating a signal for optical writing control based on the arithmetic output from the arithmetic circuit 130. The light reflection type sensor 110 includes an LED (light emitting diode-light emitting element) 101 as a light source, a condensing lens 102 that condenses the emitted light from the LED 101 into a light beam having a predetermined beam diameter, and an image carrier 150. The photoelectric conversion element (light receiving element) 103 that receives the reflected light from the image pattern 151 and converts it into an electrical signal, and imaging that forms the reflected light from the image pattern 151 on the imaging surface of the photoelectric conversion element 103 Lens 104. As the light reflection type sensor 110, a light reflection type sensor that uses the spot light SP by narrowing the irradiation beam diameter is used as can be seen from the characteristic diagram showing the relationship between the distance (beam diameter) in the scanning direction and the amount of light in FIG.

  The light reflection sensor 110 condenses the irradiation beam from the light source composed of the LED 101 by the condenser lens 102, and the circular beam diameter on the surface of the image pattern 151 formed on the image carrier 150 becomes approximately 400 [μm]. I am doing so. The light reflected from this is detected by the photoelectric conversion element 103 such as a photodiode, and the uneven adhesion of the toner particles 152 in the image pattern 151 can be captured as fluctuations in the amount of light incident on the photoelectric conversion element 103.

  As a method of capturing the light amount fluctuation according to the toner adhesion amount, a method of detecting based on a difference in regular reflection characteristics or irregular reflection characteristics between the toner particles and the surface of the image carrier, or a difference in reflection spectral characteristics between the toner particles and the surface of the image carrier. There are detection methods and the like, and by combining these, detection with higher sensitivity can be performed. When utilizing the difference between regular reflection characteristics or irregular reflection characteristics, since the toner image generally has strong irregular reflection characteristics, the surface of the image carrier 150 is preferably made of a material having high glossiness and strong regular reflection characteristics. Further, when detecting based on a difference in reflection spectral characteristics, it is preferable to use a light source wavelength in which the reflection spectral characteristics of the toner particles 152 and the reflection spectral characteristics of the surface of the image carrier 150 are greatly different. The measuring apparatus in FIG. 6 is an example in which the LED 101 having an emission wavelength of 870 [nm] is used and a detection method using the difference in irregular reflection characteristics between the toner particles 152 and the surface of the image carrier 150 is implemented. With respect to the beam diameter, at least the beam diameter (in the scanning direction of the spot light SP) in order to detect the density unevenness of about 1 [cycle / mm] with the highest sensitivity in the spatial frequency characteristics of human vision as shown in FIG. In FIG. 7, d1) needs to be 1 [mm] or less. This beam diameter d1 is derived from 1 [mm] which is the reciprocal of the value 1 [cycle / mm] at which the spatial frequency is maximum in FIG. 5. Here, the beam diameter (d1) is approximately 400 [μm]. Yes. The beam diameter d1 is defined here as a distance between points on both sides of the light beam at which the power per unit area of the spot light SP on the beam irradiation surface is reduced to 1 / e of the maximum value.

  FIG. 2 is a diagram showing an example of the configuration of the image forming process of the image forming apparatus in which the light reflection type sensor (image quality sensor) 10 of FIG. 6 is installed facing the intermediate transfer belt 5 immediately after the developing process. Scanning of the images on the photoconductors 61Y, 61C, 61M, and 61K by the spot light SP is performed by rotating the photoconductors 61Y, 61C, 61M, and 61K, and images PT1 and PT2 as shown in FIG. The output of the reflected light when scanning in the transport direction (longitudinal direction in the figure) is detected. FIG. 8 shows the state of fluctuation of the amount of light (voltage) of the reflected light from the amplifier circuit 20. The scanning condition of the spot light SP at this time is that the scanning speed is 200 [mm / s], the scanning distance is about 11 [mm], and the data sampling period is 75 [μs], that is, the sampling interval on the image is about The pitch is 15 [μm], and only one scan does not include an average processing step. Note that the average adhesion amount of the toner particles 152 adhering to the pattern can also be calculated by obtaining the light quantity average value in FIG.

1.4 Visual noise (image quality)
1.4.1 Calculation of noise amount Since the spatial frequency characteristic of the image density unevenness cannot be read in the output state in which the light amount is output with the time shown in FIG. 8 as a parameter, the spatial frequency characteristic is calculated by the arithmetic circuit 130. To do. In calculating the spatial frequency characteristics, it is preferable in terms of processing speed to apply a known method such as fast Fourier transform (FFT). The conversion result by the fast Fourier transform is shown in FIG. Note that the peak observed at 6 [cycle / mm] in FIG. 9 is due to the repetition frequency of the dot patterns in FIGS.

  As can be seen from FIG. 5, the visual characteristic is very sensitive to density unevenness having a spatial frequency near 1 [cycle / mm], and therefore, for example, the noise amount near 1 [cycle / mm] in FIG. 9 is compared. Thus, the degree of image quality deterioration of the pattern (image PT2) shown in FIG. 4 with respect to the pattern (image PT1) shown in FIG. 3 can be known. When a decrease in image quality is detected in this way, a signal is generated by the signal generation circuit 40 in the measurement apparatus of FIG. 6 so as to prompt control of appropriate image forming conditions. In response to this signal, the image forming conditions are automatically controlled by the control circuit CON of the image forming apparatus MFP shown in FIG. 6, and automatic control is performed so that the image quality can be restored to the normal image quality as much as possible.

  When it is determined that the image quality cannot be restored only by automatic control, the control circuit CON instructs a display device (not shown) to replace parts such as a developer and a photoreceptor, and prompts replacement of the parts. These procedures can maximize the life of the developer and the photoconductor. Further, since the minimum required pattern size is about 1 [mm] × about 10 [mm], the amount of toner consumed by pattern image formation can be suppressed to the minimum level.

  In the example of FIG. 2, the spot light SP is irradiated so as to detect the image quality of the surface of the intermediate transfer belt 5, but the image formed on the surface of the photoreceptors 61 </ b> Y, 61 </ b> C, 61 </ b> M, 61 </ b> K and the recording medium 20. The spot light SP can be irradiated.

1.4.2 Calculation of Visual Noise Amount After obtaining the spatial frequency characteristic shown in FIG. 9, the arithmetic circuit 130 weights the visual spatial frequency characteristic shown in FIG. Ask for. FIG. 10 is a diagram showing the relationship between the visual noise amount and the spatial frequency, and shows the output state of the visual noise amount of the arithmetic circuit 130. This weighting is performed by multiplying the characteristic of FIG. 9 by the characteristic of FIG. This calculation makes it possible to extract only the spatial frequency characteristics that appeal to the eye, so that the target image quality can be easily detected. Further, since it is possible to remove a signal component due to an image pattern structure that has appeared in the vicinity of 6 [cycle / mm], it is also possible to remove information unrelated to the image quality of interest. If information that is not related to image quality can be removed in this way, the occurrence of false detection can be almost eliminated.

1.4.3 Total amount of visual noise When the visual noise amount shown in FIG. 10 is integrated with respect to the spatial frequency region of 0.2 [cycle / mm] to 4 [cycle / mm] using the arithmetic circuit 130, FIG. As shown, the total amount of visual noise is calculated. With this value, it is possible to know the overall image quality change in almost all spatial frequency regions appealing to the eye.

  Note that an image quality evaluation pattern described later preferably uses a halftone image of about 50%. This is because the graininess is easily noticeable. First, in the case of a monocular sensor as shown in FIG. 6, on the image pattern, density fluctuation continuous data in the sub-scanning direction is collected, and in the case of a line sensor, density fluctuation continuous data in the main and sub-scanning directions are collected. In the case of a monochrome sensor, continuous data of only a specific wavelength (color) is collected, and in the case of a color sensor, continuous data of a plurality of wavelengths (colors) is collected. The collected continuous data is Fourier transformed as described above to obtain a power spectrum of density fluctuation. The square root (amplitude of fluctuation) of the power spectrum is multiplied by the visual spatial frequency characteristic (VTF), and the density fluctuation is weighted based on the visual characteristic in the frequency domain as described above. The granularity is obtained by integrating the weighted density fluctuation amount. This is a method for obtaining density-based granularity, but recently, granularity of lightness with good linearity with human vision has also been adopted. Therefore, when obtaining the granularity of lightness, it is necessary to first convert density data into lightness data. When obtaining the color granularity, the granularity is calculated by adding the chromaticity information to the lightness information. The above is how to obtain graininess information from density variation data. By applying feedback control based on the graininess information thus obtained, it is possible to continuously output images with stable graininess.

  In addition to the pattern shown in FIG. 3 described above, the pattern for detecting the image quality based on the density unevenness is, for example, a dot having a minimum unit of 600 dpi as one unit of 2 pixels × 2 pixels, and in the scanning direction of the spot light SP. If the dot array repetition period z1 is about 170 [μm] (spatial frequency f1 is about 5.9 [cycle / mm]), scanning is performed with the spot light SP having a beam diameter of about 400 [μm] as described above. When performing the above, a spectrum appears at a spatial frequency near 6 [cycle / mm] as shown in FIG. In order to avoid that the spectrum caused by the image pattern itself overlaps the image quality detection signal detection region, the dot array repetition period z1 in the scanning direction is smaller than 250 [μm], preferably 200 [μm]. It is necessary to make it smaller. Therefore, here, z1 = 170 [μm].

  In any case, as shown in the flowchart of FIG. 34 to be described later, a procedure for forming an image pattern on the image carrier to detect image quality, a procedure for irradiating the image pattern with spot light, An image quality detection function is realized by a computer program including a procedure for scanning the image pattern with the spot light and detecting a light amount reflected from the image pattern, and a procedure for detecting an image quality based on the detected light amount. Such a computer program is used by being downloaded from a recording medium recorded so as to be readable by a computer, or downloaded from a server or the like via a network.

  This control is executed by the CPU of control circuit CON of image forming apparatus MFP based on the output signal from signal generation circuit 140 of image quality detection apparatus 100. The CPU executes each process while using a ROM (not shown) as a work area based on a ROM (not shown) or a downloaded program. Program data is downloaded to a storage device such as a hard disk (not shown) from a server via a network (not shown) or from a recording medium such as a CD-ROM or an SD card via a recording medium driving device (not shown) or upgraded. Is called.

2. First Embodiment 2.1 Image Forming Unit FIGS. 12 to 14 are views showing a main part of an image forming apparatus according to the present embodiment. 12 is a monochrome image forming apparatus of a direct transfer system, FIG. 13 is a full color image forming apparatus of a quadruple tandem type intermediate transfer system, which is also described in FIGS. 1 and 12, and FIG. 14 is a full color of a quadruple tandem type direct transfer system. The image forming units of the image forming apparatus are respectively shown.

  12 includes a charging unit 62, an exposure unit 65, a developing unit 63, a primary transfer roller 53, a photoconductor cleaning unit 64, and a quenching lamp 67 along the outer peripheral surface of the photoconductor (drum) 61. The recording paper transport belt 69 is passed through the nip between the primary transfer roller 53 and the photoreceptor 61. A registration roller 23 is provided on the upstream side of the recording paper conveyance belt 69 in the paper conveyance direction, and a fixing unit 8 including a fixing roller 8a and a pressure roller 8b is provided on the downstream side. The exposure is performed by a laser beam emitted from an exposure unit (not shown) in an exposure unit 65 provided between the charging unit 62 and the developing unit 63. In the embodiment shown in FIG. 12, a temperature / humidity sensor 68 for detecting the ambient temperature and humidity in the vicinity of the image forming unit is disposed between the exposure unit 65 and the developing unit 63.

  FIG. 13 shows an image forming unit corresponding to FIG. 2, and is different from FIGS. 1 and 2 only in that the recording paper conveyance belt 69 is illustrated and the temperature / humidity sensor 68 is provided. Description is omitted. In this embodiment, the temperature / humidity sensor 68 is provided on the downstream side of the black K image forming section.

  In FIG. 14, a recording paper conveyance belt 69 is arranged instead of the intermediate transfer belt 5 with respect to the example of FIG. 13, and the paper is passed between the recording paper conveyance belt 69 and each YCMK photoconductor (drum) 61. Thus, an image is transferred onto the surface of the sheet in the order of YCMK, and each color is sequentially superimposed to form a full color image. In this embodiment, the temperature / humidity sensor 68 is disposed between the registration roller 23 and the Y image forming section on the most upstream side in the sheet conveying direction. Other parts that are not specifically described are configured in the same manner as the above-described embodiments.

  FIG. 15 shows an example of the sensor unit of the image quality detection apparatus used in these embodiments. The image quality detection apparatus in FIG. 6 is a direct light emitting / receiving type that does not use an optical fiber, but the sensor optical system is used. This is an example using an optical fiber.

  When image quality is detected in image forming apparatus MFP that performs such an image forming operation, image quality detection pattern 200 is formed on photoconductor 61, the amount of reflected light from pattern 200 is detected in a minute region, and An arithmetic circuit 130 that calculates image characteristics from the detection result is provided to detect image quality. Further, feedback control may be performed based on the calculation result of the calculation circuit 130. Although the feedback control system is not depicted in FIG. 15, the control circuit CON of the image forming apparatus main body receives the output from the arithmetic circuit 130 as shown in FIG.

  An LD, LED, or the like is used as the light emitting element 130, and light from these enters the optical fiber 105 through the collimator lens 102. After the light is emitted from the tip of the optical fiber 105, the diameter of the light beam is reduced to a desired size by the lens 106, and the detection is made up of the image carrier (photosensitive member) 150 to be detected and the toner image on the surface. The pattern 151 is irradiated. The light reflected from the image carrier itself (photosensitive member) 150 and the detection pattern 151 then enters the optical fiber 107 on the light receiving side and is irradiated to the light receiving element 103 via the lens 104. An amplification circuit 120 is installed in the vicinity of the light receiving element 103, and a weak current or a weak voltage generated in the light receiving element 103 is amplified to an output voltage of a certain level. Further, the amplified signal from the amplifier circuit 120 is input to the arithmetic circuit 130, and is typically calculated as image quality information such as granularity. If the granularity is calculated as the image quality information, the arithmetic circuit 130 calculates the noise spectrum of the signal by Fourier transform, weights the noise spectrum data by the human visual spatial frequency characteristic VTF, as described above, and the effective frequency band. Data integration, etc. are performed.

  The image quality detection sensor 100a including the detection unit 111 and the arithmetic circuit 130 illustrated in FIG. 15 is installed at a position facing the photosensitive member 61 between the developing unit 63 and the primary transfer roller 53 of the image forming unit illustrated in FIGS. Has been. Each installation position is configured to detect an image immediately before being transferred to the recording paper 20, and an image close to the image on the recording paper 20 is detected.

2.2 Relationship between Reflected Light and Image Quality Detection Device (Sensor) FIG. 16 shows a state at the time of detection of an image quality detection sensor that detects specularly reflected light, and FIG. 17 shows a state at the time of detection of an image quality detection sensor that detects diffusely reflected light. It is a figure which shows a state. Both are depicted in a form using an optical fiber. In FIG. 16, the light receiving fiber 107 is installed at a regular reflection position with respect to the light projecting fiber 105, and in FIG. It shows a state where irregularly reflected light is received by installing a coaxial fiber in which the light projecting fiber 105 and the light receiving fiber 107 are formed coaxially with an inclination. In order to achieve efficient detection, experimental data has been obtained that it is better to stand vertically to the detection surface as much as possible for both light projection and light reception. Therefore, when detecting regular reflection light shown in FIG. When detecting the irregularly reflected light shown in FIG. 17 from above the light receiving fibers 105 and 107, it is efficient to receive the irregularly reflected light at an angle close to the vertically upward direction by making the inclination of the coaxial fiber as shallow as possible. Detection is performed. In these drawings, the optical fibers 105 and 107 are used for drawing, but there is no problem even with a direct light emitting / receiving type sensor.

  Whether to detect with regular reflection light or irregular reflection light is determined by a combination of the color, surface optical characteristics, and toner color of the image carrier (photoconductor) 150. The color or toner color of the image carrier 150 is sensitive to the projection wavelength. The surface optical characteristics of the image carrier 150 are glossy surfaces (reflect light in a specular manner). ) Or diffusing surface (reflects light diffusely). Further, the toner image 152 on the image carrier 150 has a property of scattering light diffusely. For easy understanding, the light source wavelength is 650 nm below. The colors having sensitivity to this wavelength are Y, M, R, and W (white), and the insensitive colors are C, G, B, and K. The image carrier itself 150 is often dark and often has little sensitivity to this wavelength. Therefore, regarding the toner color, a combination with the surface optical characteristics (glossy surface or diffusion surface) of the image carrier 150 is considered, where M is a sensitive color and K is a non-sensitive color.

  FIG. 18 conceptually depicts the state of reflection of four combinations of surface optical characteristics (glossy surface or diffusion surface) and toner color (M or K), assuming that the color of the image carrier 150 is black with no sensitivity. It is a figure. 18A to 18D, the magnitudes of regular reflection light and irregular reflection light from the surface of the image pattern (toner image) 151 and the surface of the image carrier (photosensitive member) 150 are illustrated. .

  First, focusing on the reflection from the surface of the image pattern 151, (a) and (b) are M toners, and (c) and (d) are K toners. Since the toner image forms a diffusing surface, ideally, the reflected light is uniformly generated at any angle. Experimentally, the strongest reflected light is returned in the direction of light projection, and the amount of reflected light tends to decrease as the angle increases. However, this is also influenced by the surface properties of the toner particles themselves and is not universal as an absolute value. For red light of 650 nm, M toner reflects with high sensitivity and K toner hardly reflects. Therefore, the reflected light from the M toner in (a) and (b) has a certain amount of both regular reflection and irregular reflection, but the reflected light from the K toner in (c) and (d) is reflected in the reflection direction. Regardless, it is weak.

  Next, reflection from the surface of the image carrier 150 is considered. The state of reflection on the diffusing surface may be considered in the same manner as the toner image 152 that is also the diffusing surface, but reflection from the glossy surface occurs even from an insensitive color as far as specular reflection light is concerned. Light is reflected only by surface properties. In other words, if you place your eyes at the position of regular reflection with respect to the light source, it does not mean that where the light is shining, but what the light source looks like. This means that specularly reflected light is generated from the surface of the photoreceptor (black, glossy surface) in the diagrams (a) and (c). Since the intensity of the specular reflection light depends on the glossiness, the absolute value is not discussed here. Based on such examination, the reflected light intensities (a) to (d) are drawn. In the figure, there is a difference between the reflected light from the toner image 152 and the reflected light from the surface of the image carrier 150. Some are measurable, and others are not measurable. FIG. 19 shows the result of reading which reflected light has a difference. FIG. 19 shows the relationship between the glossy surface and the diffusing surface and regular reflection and irregular reflection.

2.3 Graininess Calculation and Control Graininess is calculated and controlled. The graininess is calculated by the arithmetic circuit 130 shown in FIG. 6 or FIG. 15, but will be described in more detail with reference to FIG. To do. It has been found that graininess is affected by image density. Therefore, if the image pattern to be measured is one gradation, it is affected by the density, and accurate granularity cannot be detected. In this embodiment, several to a dozen types of gradation patches are used as image patterns for measuring graininess, and gradation patches that fall within a certain image density range are used for detection. Thus, by always detecting a pattern in the same density range, even if the density of the entire image changes, the influence of density fluctuation can be eliminated from the detected granularity.

  For the image density, sensor outputs from the respective gradation patches 200a to 200i are used. There is no clear indication as to what pattern to create each tone patch in, but it is said that the unevenness of the pattern shape affects the graininess, so the pattern of the same shape is repeatedly formed If it's a patch, the pattern shape seems less important. By detecting the gradation pattern 200 with a sensor, raw sensor output data for the time at the left end 200a in FIG. 20 can be obtained for each of the patches 200a to 200i. The sensor output of each patch 200a is converted into an image density, and only the raw data of the patch that falls within a predetermined density range is used.

  Next, each data to be used is converted to the frequency domain by performing FFT conversion, and the value SS (f) on the vertical axis represents the spatial frequency characteristics of the patches 200a to 200i. Furthermore, VTF, which is the spatial frequency characteristic of human vision, is multiplied by SS (f), and brightness correction is added to the integrated value. Finally, the graininess is obtained by averaging the values of several types of patches. This graininess is shown by the following equation.

Granularity = h (D) ∫SS (f) × VTF (f) df
FIG. 21 shows a comparison between the graininess index calculated by the above equation and the granularity of an image on actual paper. It can be seen that the correlation coefficient is 0.941, which is very correlated with the granularity on the paper. When the graininess calculated in this way fluctuates, the graininess can be kept in a good state by changing a control factor that can control the graininess. As control factors, development bias, charging grid bias, LD power, development sleeve linear velocity, and the like can be considered. By maintaining good graininess with these control factors, it is possible to continue forming an image that does not make the image viewer feel the roughness of the image.

2.4 Calculation and control of sharpness Sharpness is evaluated by calculating a spatial frequency characteristic (MTF) of an image. Since there are various methods for calculating the MTF, it will not be described here. In practice, however, a sensor capable of detecting a minute region density of the frequency pattern 210 as shown in FIG. 22, such as the image quality detection sensor shown in FIG. 6 or FIG. It is realistic to detect and analyze / calculate with 100a. When the sharpness deteriorates, the edge of the frequency pattern 210 becomes blurred and cannot be resolved. In order to prevent this, it is controlled by a control factor that can control the sharpness. These factors are considered to be development bias, charging grid bias, LD power, development sleeve linear velocity, etc., as well as graininess.

2.5 Gradation Calculation and Control Gradation is evaluated by outputting several (or more than a dozen) types of gradation patterns and detecting them with an image density sensor. This is something that has been done for some time on the market and has been implemented using a density sensor. Therefore, although it is not new as a technique, it is advantageous that a minute area density sensor (here, image quality detection sensor 100a) capable of detecting graininess and sharpness also serves as gradation control, and the density sensor can be replaced. it can. Further, since the density sensor does not narrow the luminous flux, a gradation pattern with a certain size (about 20 mm square) is necessary. However, since the minute area density sensor narrows the luminous flux to about 1 mm or less, the gradation pattern The length in the main scanning direction can be made considerably smaller than the conventional P sensor pattern. Also, regarding the length in the sub-scanning direction, the micro area density sensor (here, the image quality detection sensor 100a) collects data at a high response speed in order to detect micro density unevenness such as graininess and sharpness. Therefore, it can be made considerably shorter than the conventional density sensor pattern. The gradation control factor is LD power.

2.6 Image Quality Control Factors Image quality control factors such as graininess and sharpness are development bias, charging grid bias, LD power, and development sleeve linear velocity, all of which are development conditions. Further, the development bias, the charging grid bias, and the LD power are adjustments of development potential (potential development ability), and the development sleeve linear velocity is adjustment of development chance (physical development ability). Both have the ability to change the toner adhesion amount. However, increasing the developing bias increases the effect of placing toner on the electrostatic latent image, and increasing the developing sleeve linear velocity increases the potential well shape for the electrostatic latent image. It has the effect of fraying the toner faithfully.

  Image quality (granularity, sharpness) can be improved by adjusting the development bias, charging grid bias, and LD power when the development potential is insufficient, and by adjusting the developing sleeve linear velocity when the development opportunity is insufficient. it can. Of these development conditions, FIG. 23 shows the change in graininess when the development bias and the development sleeve linear velocity are controlled in combination. In the figure, the horizontal axis represents the toner adhesion amount and the vertical axis represents the graininess. In the figure, the one-dot chain line that rises to the right is the equal sleeve linear velocity line M, and the dotted line that descends to the right is the equal developing bias line N. That is, as the developing sleeve linear velocity is changed, the graininess and the toner adhesion amount move on the equal sleeve linear velocity line M in accordance with the developing bias value fixed at that time. The reverse is true when the development bias is changed. Therefore, when the two are controlled in combination, for example, when the image quality deteriorates from the point of “standard image quality” in FIG. 23 to the point of “degraded image quality” due to deterioration over time, as indicated by arrows S1 and S2. Image quality can be restored by control. In addition, there is a case where the toner adhesion amount is controlled by another control algorithm. In this case, control is performed as indicated by arrows T1 and T2 so as not to change the toner adhesion amount, and only the image quality is the value of the standard image. It is also possible to restore to (point of image quality A).

  In this example, the development bias and the developing sleeve linear velocity are controlled in combination. However, the developing bias, the charging grid bias, and the LD power are factors that change the developing potential, and other combinations (charging grid bias and developing sleeve linear velocity). Or LD power and developing sleeve linear velocity) and all these four factors can be combined to control the same effect. Thus, the range of image quality control can be expanded by combining control factors.

2.7 Concentration detection Next, consider the case of detecting the concentration. The density optically detects the density of the pattern on the image carrier (photosensitive body) 150, but the same detection means (here, the reflected light quantity detection means for detecting the image quality, only the pattern to be detected is different) Then, it can be detected by the image quality detection sensor 100a). When detecting the density, a density detection pattern is formed on the image carrier (photosensitive body) 150, the amount of reflected light from the pattern is detected in a minute region, and the average value of the obtained sensor outputs is obtained. Yes. Whether the density of the pattern on the image carrier (photoconductor) 150 should be detected with specular reflection light (FIG. 16) or irregularly reflected light (FIG. 17) depends on the color of the image carrier (photoconductor) 150 or It is determined by a combination of surface optical characteristics and toner color. This is the same as in the case of image quality detection, and the description in FIGS. 18 and 19 also applies to the case of density detection.

  A gradation pattern is used as the density detection pattern. FIG. 24 shows the correlation between the sensor output in the halftone dot image pattern and the actual density (attachment amount on the image carrier). Also in this case, a very high correlation with a correlation coefficient of 0.958 is obtained, indicating that the density detection can be performed with high accuracy by the image quality detection means.

2.8 Environmental Fluctuation (Temperature and Humidity) Detection The density and image quality on the image carrier (photosensitive member) 150 are greatly affected by environmental fluctuations (temperature and humidity). Therefore, as shown in FIGS. 12 to 14, a temperature / humidity sensor 68 is installed in the image forming apparatus MFT to detect temperature and humidity. Various installation positions of the temperature / humidity sensor 68 other than the positions shown in FIGS. 12 to 14 are conceivable, and the installation position is not limited. The temperature and humidity of the image quality formation area in the image forming apparatus MFT are detected. It can be anywhere you can. However, in the vicinity of the fixing unit 8, it is necessary to avoid the vicinity of the fixing unit 8 because the temperature and humidity in the image forming apparatus MFT cannot be accurately detected due to the influence of the temperature of the fixing roller 8 a.

  FIG. 25 and FIG. 26 show the influence of the density (toner adhesion amount) on the image carrier (photoconductor) 150 from the temperature and humidity. FIG. 25 is a characteristic diagram showing the temperature dependence of the density (toner adhesion amount), and it can be seen that the density (toner adhesion amount) on the image carrier (photoconductor) 150 increases as the temperature increases. FIG. 26 is a characteristic diagram showing the humidity dependence of density, and it can be seen that the density (toner adhesion amount) on the image carrier (photoconductor) 150 increases as the humidity increases. As described above, the toner density on the image bearing member (photosensitive member) 150 is greatly influenced by environmental fluctuations (temperature and humidity).

  27 and 28 are diagrams showing the influence of image quality on temperature and humidity. Here, the granularity is taken on the vertical axis. The granularity is an important factor that determines the image quality as described above. A larger value indicates that the image quality is deteriorated. FIG. 27 is a characteristic diagram showing the temperature dependence of the image quality. From this figure, the image quality improves as the temperature is raised from a low temperature, and takes a minimum value near 15 to 20 ° C., and further raises the temperature. It turns out that the image quality is getting worse again. FIG. 28 is a diagram showing the humidity dependence of the image quality, and it can be seen that the change is similar to the case of temperature. Thus, the image quality is also greatly affected by environmental fluctuations (temperature and humidity). This indicates that the influence of environmental fluctuations (temperature and humidity) should also be taken into account when determining agent deterioration.

2.8 Deterioration with time 2.8.1 Image carrier As an influence on the detection of density and image quality, a change with time of the image carrier (photosensitive member) 150 is also conceivable. The surface of the image bearing member (photosensitive member) 150 may be scratched or scraped due to dirt from paper dust or residual toner, discharge due to charging / transfer, abrasion at the cleaning unit, and the like. When the density and image quality are detected on the image carrier (photosensitive member) 150 whose surface is deteriorated due to such dirt, scratches, or shavings, the amount of reflected light from the pattern or image carrier (photosensitive member) 150 is contaminated. Due to scratches and shavings, accurate density and image quality cannot be detected. Although the developer is not actually deteriorated, the density and image quality show abnormal values, and it is determined that the agent is deteriorated, and there is a sufficient possibility that unnecessary developer replacement is performed. Therefore, the surface state of the image carrier (photosensitive member) 150 is detected before the density and image quality are detected.

  Actually, the amount of light reflected from the surface of the photoconductor 61 is detected in a minute region without forming a toner image on the photoconductor 61. As in the case of density, the detection means can be detected by the same detection means as the reflected light amount detection means (image quality detection sensor 100a) for detecting the image quality. When the surface of the photoconductor 61 is not deteriorated, the amount of reflected light shows a constant value. However, when the surface of the photoconductor 61 is soiled, scratched or scraped, the amount of reflected light shows an abnormal value, and deterioration can be detected. When the surface deterioration of the photoreceptor 61 is detected, a message for replacing the corresponding member is displayed on the display unit of the image forming apparatus MFT, or information on the surface deterioration is transmitted to the external management apparatus.

2.8.2 Other deterioration over time (filming, film thickness, potential of image area and non-image area, residual charge after static elimination)
Furthermore, filming, film thickness, potential of image and non-image areas, and residual charge after static elimination can be considered as changes over time that affect the detection of density and image quality. Therefore, when detecting these temporal changes, as shown in FIG. 29, the first potential sensor 210 is provided downstream of the quenching lamp 67 in the photosensitive member rotation direction, and the filming detection sensor 211 is further provided downstream thereof. A second potential sensor 213 is provided on the downstream side of the exposure unit 65, and the film thickness detector / measurement device 212 is connected to a charging unit (charging roller).

  If comprised in this way, the detection of filming can be performed by irradiating the surface of the photoreceptor 61 with light, and detecting the amount of reflected light. Whether to detect with regular reflection light or diffuse reflection light is determined as described with reference to FIG. 18 and FIG. 19, as in the case of image quality detection and density detection. Compared with the amount of reflected light from the portion where filming has not occurred, the amount of reflected light from the portion where filming has occurred shows an abnormal value, so that it is possible to detect filming by detecting the amount of reflected light.

The film thickness of the photoconductor 61 is detected by measuring the current value flowing into the surface of the photoconductor 61 during charging with the film thickness measuring device 212. The surface potential of the photosensitive member 61 is detected by the second potential sensor 213. The remaining charge after the charge removal is performed by detecting the potential of the surface of the photoreceptor 61 after the charge removal by the quenching lamp 67 by the first potential sensor 210. When abnormality with time of the photoconductor 61 is detected, a message for replacing the corresponding member is displayed on the display unit of image forming apparatus MFP, or information on the abnormality is transmitted to the external management apparatus.

2.9 Agent Degradation FIG. 30 is a characteristic diagram showing the relationship between developer degradation and granularity. Of the deteriorated states, the “initial” is a new developer, and there is no deterioration at all. “Slightly deteriorated” is a slightly deteriorated state, but is an allowable deterioration state. “Large deterioration” is a state in which deterioration has progressed considerably and can be determined as a deterioration agent. As can be seen from FIG. 30, the granularity value increases as the developer deteriorates, and the image quality deteriorates.

  FIG. 31 is a characteristic diagram showing an example of the relationship between developer deterioration and toner adhesion amount (density) on the photoreceptor. This is a change in density when the developer is deteriorated, and it can be seen from FIG. 31 that the toner adhesion amount decreases as the developer deteriorates. Accordingly, the degree of deterioration of the developer can be determined from the pattern density on the photoreceptor 61.

  Further, when the developer is deteriorated, toner with weak charge (weakly charged toner) or toner charged with reverse polarity (reversely charged toner) is generated. FIG. 32 is a diagram showing measurement data of charge Q / particle diameter d in the initial agent and the deterioration agent. Since the particle size distribution of the toner is not so wide, FIG. 32 can be considered as a charge distribution. From FIG. 32, weakly charged toner and reversely charged toner are observed around −0.2 to +0.1 [fC / μm] in the degrading agent. The weakly charged toner and the reversely charged toner are likely to adhere to the non-image area on the photosensitive member 61, causing scumming and dust and leading to image quality deterioration. Therefore, image quality deterioration and agent deterioration can be recognized by detecting weakly charged toner and reversely charged toner in the non-image area. The detection of the weakly charged toner and the reversely charged toner is performed by detecting the density of the non-image portion on the photoreceptor 61.

2.10 Determination of Agent Degradation Image quality degradation is performed by comparing the calculated granularity, gradation, and sharpness indicators with respective threshold values. The respective threshold values are obtained in advance by experiments or the like and stored in the RAM in the image forming apparatus MFP. Similarly, the agent deterioration is determined based on the comparison between the obtained density and the threshold value and the density value of the non-image part. Since the density is affected by the temperature and humidity, the threshold is calibrated using the temperature and humidity detection result.

2.10.1 Control Circuit Image quality and agent deterioration are performed by a control circuit CON in the image forming apparatus MFP. This control configuration is shown in FIG. FIG. 33 is a block diagram showing an outline of the control device of the digital multi-function peripheral according to the present embodiment. In the figure, the control circuit CON controls the ADF 36, the writing unit 7, the image forming unit 6, the fixing unit 8, the paper feeding unit 2, and the scanner unit 3, and the operation display unit 1a, the image processing unit 1b, and the image memory. 1c, nonvolatile memory 1d, image quality detection sensor 100a, and various sensors 100b are connected to the control circuit CON. The control circuit CON executes a control desired by the user in response to an instruction input from the operation display unit 1a, temporarily stores the image data read by the scanner unit 3 in the image memory 1c, and then selects a predetermined or desired image by the user. The processing is performed by the image processing unit 1 b and output to the writing unit 7, the image is formed by the image forming unit 6, transferred to the recording paper 20 fed from the paper feeding unit 2, fixed by the fixing unit 8, and then discharged. Paper out or carry out to the duplex unit 9 side. These control programs are stored in the non-volatile memory 1d, and the control circuit CON executes predetermined control according to the control program.

2.10.2 Control Procedure FIG. 34 shows a control procedure for image formation in consideration of the agent deterioration determination and the agent deterioration determination. In this processing, first, aged deterioration of a portion related to image formation of the image forming apparatus is checked, and then image quality check and agent deterioration check are performed. This is the timing for performing these checks, but this is not a limitation. It may be either when the power is turned on, after a certain time has elapsed, after outputting a certain number of sheets, or after a certain amount of toner has been consumed. Alternatively, it may be performed after receiving an instruction from a user, a serviceman, or an external management device.

  In this process, as described above, first, the deterioration with time of the image carrier (photoconductor) 150 is detected (step S101). Deterioration over time includes the check of scratches and dirt on the image carrier, filming check, image portion and non-image portion potential check, film thickness check and residual potential check as in the previous operation. Alternatively, if it is performed serially and there is any abnormality (deterioration with time) in the check (step S102-N), it is further checked whether the deterioration with time affects the image quality (step S103).

  If it is determined that the image quality is affected, change the criterion for determining that the abnormal (deteriorated over time) is abnormal (by changing the preset threshold value that is the criterion) -Step S105) The influence of the image quality is checked again (Step S103). If it is not possible to set a threshold value that does not affect the image quality by repeating this process several times, the deterioration with time has progressed and image control cannot be handled. Displayed on the operation display unit 1a of the apparatus. At the same time, the information can be transmitted to the external management apparatus (step S124).

  When no deterioration over time is recognized in all the parts checked in step S101 (step S102-N), or when deterioration over time is recognized in step S102 but can be dealt with by changing the image control, the image carrier The image quality detection pattern 200 shown in FIG. 20 is created on the (photosensitive member) 150 (step S107), and the image quality detection pattern 200 is irradiated with light from the light emitting element 101. The amount of light reflected from the pattern 200 is detected by the light receiving element 103 (step S108), and image characteristics such as graininess and sharpness are calculated from the detection result (step S109).

  Next, the calculated image characteristic is compared with a preset characteristic to determine the degree of image quality degradation (step S110). If the degree of image quality degradation is equal to or greater than a preset value, a density detection pattern is formed on the image carrier (photosensitive body) 150 assuming that image quality degradation has progressed. Conventionally used gradation patterns are used as the density detection patterns. On the other hand, if the degree of image deterioration does not reach a preset value in the determination in step S110, it is determined that the image quality has not deteriorated, and density detection is performed on the image carrier 150 in order to perform constant density control. A pattern is formed, and the density of the pattern is detected. Based on the detection result, the charging grid bias, the developing bias, and the LD power are controlled to perform a constant density control. Thereafter, the sleeve linear velocity is combined with the charging grid bias / development bias / LD power to restore the image quality while maintaining the constant density, thereby controlling the image quality (step S111). Finally, the γ curve is controlled and copying is performed (step S123).

  On the other hand, if it is determined in step S110 that the degree of image quality deterioration is equal to or greater than a predetermined value and the image quality deterioration is progressing, a density detection pattern is formed on the image carrier (photosensitive body) 150, and the density of the pattern is determined. The density of the non-image part is detected (step S113). Further, the temperature and humidity in image forming apparatus MFP are detected by temperature / humidity sensor 68 (step S114). Using the temperature and humidity detection results, the density threshold value stored in the nonvolatile memory 1d of the image forming apparatus MFP is calibrated. The calibrated threshold value is compared with the detected concentration, and the agent deterioration is comprehensively determined (step S115).

  When it is determined that the developer is deteriorated in the agent deterioration determination (step S115-Y), the determination result of the agent deterioration determination is transmitted to the external management device by the communication means (step S116). The determination result is displayed on operation display unit 1a of image forming apparatus MFP (step S117).

  Any order may be used, and the agent deterioration determination result is not transmitted from the external I / F 1e to the external management device, but only displayed on the operation display unit 1a, and the user contacts the service station. Good. At that time, if the developer is deteriorated, it is necessary to replace the developer. Therefore, a service man call for replacing the developer may be displayed. The external management apparatus that has received the determination result from the image forming apparatus MFP notifies the service person of the instruction to replace the developer, or the service center dispatches the service person in response to the notification from the user.

  Next, on the operation display unit 1a of the image forming apparatus MFP, a display asking whether or not to continue the image formation even if the image has deteriorated is displayed to the user (step S121). By looking at the display 1a, it is determined whether or not to perform image formation for the job currently being used (step S122). Then, even if the agent has deteriorated and the image quality has deteriorated, the copy is executed if the copy is necessary (step S123). If the copy having the deteriorated image quality is unnecessary, the process ends without performing the copy.

  If it is determined in step S115 that the agent is not deteriorated, it is determined that there are other factors that are not caused by the respective parts checked in step S110 or are not caused by the agent deterioration (step S118). Then, it is transmitted to the external management apparatus by the communication means (step S119), and the fact that the agent deterioration is not a factor of the image quality deterioration is displayed on the operation display unit 1a of the image forming apparatus MFP (step S120). Any order may be used, and the determination result may be stopped on the operation display unit 1a without being transmitted to the external management apparatus by the communication means, and the user may contact the service station. At that time, since it is important to find the cause, a service man call may be displayed. The external management apparatus that has received the determination result from the image forming apparatus notifies the service person that the cause is unknown, or the service center dispatches a service person in response to a notification from the user.

  Next, on the operation display unit 1a of the image forming apparatus MFP, a display asking whether or not to continue the image formation even if the image has deteriorated is displayed to the user (step S121). By looking at the display 1a, it is determined whether or not to perform image formation for the job currently being used (step S122). Then, even if the agent has deteriorated and the image quality has deteriorated, the copy is executed if the copy is necessary (step S123). If the copy having the deteriorated image quality is unnecessary, the process ends without performing the copy.

  If the cause of the image quality deterioration is other than the part checked in step S101 and not the agent deterioration, for example, the writing unit 7 may be defective. A serviceman call is indispensable because any cause can only be dealt with by a serviceman.

3. Second Embodiment FIG. 35 is a schematic configuration diagram showing a main part of an image forming section 1 of an image forming apparatus MFP according to a second embodiment. In this second embodiment, the image quality and density are detected on the same image carrier 150, but in the first embodiment, what is detected on the photosensitive member 61 is the intermediate transfer member (intermediate transfer belt 5). The configuration and detection method of the sensor 100a are the same as in the first embodiment.

  The installation position of the sensor 100a is a position facing the intermediate transfer belt 5 between the primary transfer roller 66 and the secondary transfer roller 51 as shown in FIG. An image immediately before being transferred to the recording paper 20 is detected, and an image close to the image transferred onto the recording paper 20 is detected.

  In addition to environmental fluctuations (temperature and humidity) in the image quality forming apparatus MFP, filming of the photoconductor 61, film thickness, image and non-image area potentials, residual charge after static elimination, and other factors that affect density and image quality Further, deterioration of the surface of the intermediate transfer belt 5 with time can be considered. The surface of the intermediate transfer belt 5 may be scratched or scraped due to dirt caused by paper dust or residual toner, discharge due to transfer, uneven wear at the cleaning portion, and the like, and surface deterioration will occur over time. When the density or image quality is detected on the intermediate transfer belt 5 whose surface has deteriorated due to such dirt, scratches, or shavings, the amount of light reflected from the patterns 200 and 210 and the image carrier 150 is affected by the dirt, scratches, or shavings. As a result, accurate density and image quality cannot be detected. For this reason, although the developer is not actually deteriorated, the density and image quality show abnormal values, and it is determined that the agent is deteriorated, and there is a possibility that wasteful developer replacement is performed. Therefore, before detecting the density and image quality, the surface state of the intermediate transfer belt 5 as the image carrier 150 is detected (step S101).

  Actually, the amount of light reflected from the surface of the intermediate transfer belt 5 is detected in a minute region without forming a toner image on the intermediate transfer belt 5. As in the case of density, the detection means can be detected by the same detection means as the reflected light amount detection means (image quality detection sensor 100a) for detecting the image quality. When the surface of the intermediate transfer belt 5 is not deteriorated, the amount of reflected light shows a constant value. However, when the surface of the intermediate transfer belt 5 is soiled, scratched or scraped, the amount of reflected light shows an abnormal value, and deterioration can be detected. . When surface deterioration of intermediate transfer belt 5 is detected, a message for replacing the corresponding member is displayed on operation display unit 1a of image forming apparatus MFP, or information on surface deterioration is transmitted to the external management apparatus. The detection of scratches or dirt on the surface of the intermediate transfer belt 5 is performed at the same time as the filming of the photoconductor 61, the film thickness, the potential of the image area and the non-image area, and the detection of the residual charge after static elimination.

  Other parts not specifically described are configured in the same manner as in the first embodiment.

4). Third Embodiment FIGS. 36 and 37 are schematic configuration diagrams showing the main part of an image forming section 1 of an image forming apparatus according to a third embodiment. In the third embodiment, the image quality and density are detected on the same image carrier 150, but in the first embodiment, the detection on the photosensitive member 61 is the recording paper transport member (recording paper transport belt). 69) The configuration and detection method of the sensor 100a are the same as those in the first embodiment.

  As shown in FIGS. 36 and 37 (as in the case of the monochrome image forming unit 1 as shown in FIG. 12), the sensor 100a is installed at a position facing the recording paper conveyance belt 69 of the image forming unit 1. A sensor 100a is installed at this position to detect an image transferred on the recording paper conveyance belt 69.

  In addition to environmental fluctuations (temperature and humidity) in the image quality forming apparatus MFP, filming of the photoconductor 61, film thickness, image and non-image area potentials, residual charge after static elimination, and other factors that affect density and image quality Also, the surface deterioration of the recording paper transport belt (recording paper transport member) 69 can be considered. The surface of the recording paper conveyance belt 69 is soiled, scratched or scraped by paper dust, and the surface deteriorates over time. When the density or image quality is detected on the recording paper transport belt 69 whose surface has deteriorated due to such dirt, scratches, or shavings, the amount of light reflected from the patterns 200 and 210 and the recording paper transport belt 69 is soiled, scratched, or scraped. Therefore, accurate density and image quality cannot be detected. Although the developer is not actually deteriorated, the density and image quality show abnormal values, and it is determined that the agent is deteriorated, and there is a sufficient possibility that unnecessary developer replacement is performed. Therefore, the surface state of the recording paper transport belt 69 is detected before the density and image quality are detected. Actually, the amount of light reflected from the surface of the recording paper conveyance belt 69 is detected in a minute region without forming a toner image on the recording paper conveyance belt 69. As in the case of density, the detection means can be detected by the same detection means as the reflected light amount detection sensor 100a that detects the image quality.

  When the surface of the recording paper transport belt 69 is not deteriorated, the reflected light amount shows a constant value. However, when the surface of the recording paper transport belt 69 is soiled, scratched or scraped, the reflected light amount shows an abnormal value and the deterioration is detected. it can. When the surface deterioration of the recording paper conveyance belt 69 is detected, a message for replacing the corresponding member is displayed on the operation display unit 1a of the image forming apparatus MFP, or information on the surface deterioration is transmitted to the external management apparatus. The detection of scratches / stains on the surface of the recording paper conveyance belt 69 is performed at the same time as the filming of the photoconductor 51, the film thickness, the potential of the image area and the non-image area, and the detection of the residual charge after static elimination.

  Other parts not specifically described are configured in the same manner as in the first embodiment.

5). Fourth Embodiment In the first to third embodiments described above, detection patterns (image quality detection pattern 200 and density detection pattern− formed on or transferred to the photoreceptor 61, the intermediate transfer belt 5 and the recording paper transport belt 69). In the sensor unit 100c shown in FIG. 38, a dedicated transfer roller 109a as an image carrier to which a detection pattern is transferred is used as the photosensitive member 51, the intermediate transfer belt 5, and the like. Alternatively, it is installed between the recording paper conveyance belt 69 and the sensor head 108, and the detection pattern transferred onto the dedicated transfer roller 109 a is detected by the sensor head 108.

  FIG. 38 is a diagram showing a schematic configuration of a sensor unit 100c according to the fourth embodiment. In the figure, the sensor unit 100c includes a detection unit including a sensor head 108, a sensor amplifier 120a, and a calculation unit 130a, a dedicated transfer roller 109a, and a cleaning unit 109b, and constitutes one unit. The sensor head 108 is configured as one unit from the light emitting element 101, the light receiving element 103, the lenses 102, 104, and 106 and the fibers 105 and 107 in FIG. 15, and the lens 106 faces the surface of the dedicated transfer roller 109a. The sensor amplifier 120a corresponds to the amplifier circuit 120 in FIG. 15, amplifies the output photoelectrically converted by the light receiving element 103, and passes it to the arithmetic unit 130a. The calculation unit 130a corresponds to the calculation circuit 130 in FIG. 15, and performs predetermined calculation processing based on the amplified signal.

  The dedicated transfer roller 109a is formed on the photosensitive member 51, the intermediate transfer belt 5, or the recording paper transport belt 69, or the transferred pattern is further transferred. The sensor head 108 is transferred onto the dedicated transfer roller 109a. The above-described image quality and density are detected by optically scanning the pattern. The cleaning unit 109b cleans the toner image on the dedicated transfer roller 109a with a cleaning blade, for example.

  Various materials such as a conductive, non-conductive, and elastic roller can be used as the material for the dedicated transfer roller 109a. The configuration of the sensor unit may be a direct light emitting / receiving type that does not use the optical fibers 105 and 107, and the cleaning method of the dedicated transfer roller 109b may not be the blade cleaning method as shown in the figure, for example, a fur brush cleaning method Alternatively, a cleaning method may be employed in which a cleaning member is not installed, and reverse transfer is performed to the image carrier side by applying a reverse transfer bias after measurement. In any case, the positioning accuracy of the sensor head 108 with respect to the surface of the dedicated transfer roller 109a can be improved by positioning the sensor head 108 and the dedicated transfer roller 109a in this way (that is, fixing them to each other). . In addition, this makes it possible to stabilize the diameter of the light projection spot on the surface of the dedicated transfer roller 109a, to stably enter the reflected light on the light receiving element 103, and to improve the accuracy of the detected and calculated image quality data. Further, in the case of this sensor unit 100c, the image quality data (digital data) calculated by the calculation unit 130a is output, so that there is an advantage that it is easy to handle when viewed from the image forming apparatus MFP main body side. However, the sensor is expensive.

  Therefore, as another configuration, there is a configuration in which the dedicated transfer roller 109a and the detection unit are used as one unit and the calculation unit 103a is installed on the main body side. In this configuration, calculation unit 130a is required outside the sensor, so sensor analog data is received on the control board side of image forming apparatus MFP, and calculation processing is performed on the control board. Since the calculation unit 103a is not installed in the sensor itself, it is advantageous in reducing the size and cost of the sensor 103a. However, on the other hand, it is necessary to bring the analog signal to the control board side of image forming apparatus MFP, and there is a possibility that new noise is generated in the signal during that time. Accordingly, the configuration to be selected is determined in consideration of these advantages and disadvantages.

  The sensor unit 100c configured as shown in FIG. 38 is installed at the same position as in the first to third embodiments. This corresponds to further transferring the image immediately before transferring to the recording paper at each installation position or the image transferred to the recording paper (actually, transferring the image transferred on the recording paper transport belt 69 instead of the recording paper) ), And a situation similar to that in which an image on a recording sheet is detected is created by optimally setting a transfer condition. Further, the dedicated transfer roller 109a is configured so as to be able to come into contact with and separate from the photoconductor 51, the intermediate transfer belt 5, and the recording paper conveyance belt 69. The belt 5 or the recording paper conveyance belt 69 is separated. By doing so, it is possible to reduce scratches and dirt due to aging of the dedicated transfer roller 109a, and the image is not disturbed in a normal image output state.

  Whether to detect with regular reflection light or irregular reflection light is determined by the combination of the color of the dedicated transfer roller 109a, the surface optical characteristics, and the toner color. In the case of detection on the dedicated transfer roller 109a, the surface optical characteristics and color of the dedicated transfer roller 109a can be arbitrarily selected. Therefore, W (white) with sensitivity and K (black) with no sensitivity can be selected as colors, and a glossy surface and a diffusion surface can be arbitrarily selected as surface optical characteristics. In addition, since there are M (mascent) and K (black) as toner colors, there are eight possible conditions. When considered in the same manner as the case of FIG. 19 of the first embodiment, a result as shown in FIG. 39 is obtained.

  The detection of image quality and density is the same as that of the first embodiment, except that the place to be detected is replaced by the dedicated transfer roller 109a.

  In addition to environmental fluctuations (temperature and humidity) in the image quality forming apparatus MFP, filming of the photoconductor 51, film thickness, image and non-image area potentials, residual charge after static elimination, and other factors that affect density and image quality Also, the surface deterioration of the dedicated transfer roller 109a may be considered. The surface of the dedicated transfer roller 109a may be scratched or scraped due to dirt due to residual toner, discharge due to transfer, uneven wear at the cleaning unit, or the like, and surface degradation may occur over time. When density and image quality are detected on the transfer roller 109a whose surface has deteriorated due to such dirt, scratches, or scraping, the amount of light reflected from the pattern or the dedicated transfer roller 109a is affected by dirt, scratches, or scraping, and is accurate. High density and image quality cannot be detected. For this reason, although the developer is not actually deteriorated, the density and image quality show abnormal values, and it is determined that the agent is deteriorated, and there is a possibility that wasteful developer replacement is performed. Therefore, the surface state of the dedicated transfer roller 109a is detected before the density and image quality are detected. Actually, the amount of light reflected from the surface of the dedicated transfer roller 109a is detected in a minute region without forming a toner image on the dedicated transfer roller 109a. As in the case of density, the detection means uses a sensor head 108 that detects image quality, a sensor amplifier 120a, and a calculation unit 130a.

  When the surface of the dedicated transfer roller 109a is not deteriorated, the amount of reflected light shows a constant value. However, when the surface of the dedicated transfer roller 109a is dirty, scratched or scraped, the amount of reflected light shows an abnormal value, and deterioration can be detected. . When the surface deterioration of the dedicated transfer roller 109a is detected, a message for replacing the dedicated transfer roller 109a is displayed on the operation display unit 1a of the image forming apparatus MFP, or information on the surface deterioration is transmitted to the external management device. The detection of scratches and dirt on the surface of the dedicated transfer roller 109a is performed at the same time as the filming of the photosensitive member 61, the film thickness, the potential of the image area and the non-image area, and the detection of the residual charge after static elimination. Corresponds to step 101 of FIG.

  The other parts are configured in the same way as in the first embodiment.

  As described above, according to the first to fourth embodiments, the following effects can be obtained.

(1) When the image quality is detected by the control circuit CON or the arithmetic circuit 130 in the image forming apparatus, the detection result is calculated, and the agent deterioration is determined based on the calculation result, the pattern formed on the image carrier 150 is displayed. Not only the toner density but also the image quality can be used as a criterion.

(2) Since the agent deterioration is determined after the image quality is determined to be deteriorated, the agent deterioration can be determined based on the image quality.

(3) Since the sensor 100a, the arithmetic circuit 130, and the control circuit CON that detect the image quality also detect the density, the single sensor 100a can detect both the image quality and the density, and a means for detecting the image quality is provided separately. The cost increase due to can be greatly reduced.

(4) Since not only the density of the image part but also the density of the non-image part is detected, it is possible to detect weakly charged toner and reversely charged toner, and it is possible to determine the deterioration of the agent with high accuracy.

(5) In the system in which the toner image on the photosensitive member 61 is directly transferred to the recording paper 20, the image quality and density are detected at a position after development and before transfer, thereby being close to the actual image on the recording paper 20. An image can be detected.

(6) By detecting the image quality and density immediately before the toner image is transferred to the recording paper 20, an image close to the actual image on the recording paper 20 can be detected.

(7) By detecting the image quality and density at the position immediately after transfer to the recording paper transport belt 69 instead of the recording paper 20, an image equivalent to the image on the actual recording paper 20 can be detected.

(8) By installing a dedicated transfer roller 109a for image quality / density pattern detection and detecting the pattern on the dedicated transfer roller 109a, the influence of the surface optical characteristic difference of the photoreceptor 61 and the intermediate transfer belt 5 depending on the model Thus, it is possible to detect a pattern that is not affected by scratches or dirt due to deterioration with time.

(9) By matching the surface optical characteristics of the dedicated transfer roller 109a with the optical system of the sensor 100a that detects image quality, more accurate detection can be performed.

(10) The installation position of the dedicated transfer roller 109a is set to a position immediately before the transfer of the toner image to the recording paper 20, or a position immediately after the toner image is transferred to the recording paper conveyance belt 69 (instead of the recording paper 20). As a result, an image equivalent to the image on the actual recording paper 20 can be transferred onto the dedicated transfer roller 109a, and the image quality and density detected thereby are substantially the same as the image quality and density of the image on the recording paper. Can be.

(11) Since the density of the pattern is greatly influenced by temperature and humidity, the temperature and humidity at the time of detecting the density are measured, and the determination of the agent deterioration is performed based on the result, thereby making a highly accurate determination. Can do.

(12) When it is determined that the agent has deteriorated, it is possible to notify the user or service person of the agent deterioration or agent replacement by displaying the determination result of the image quality deterioration or the agent deterioration.

(13) When it is determined that the agent has deteriorated, the determination result is transmitted to the external management device, whereby the external management device can instruct the serviceman to replace the agent, and places a burden on the user for the serviceman call. In addition, the downtime of the image forming apparatus can be reduced.

(14) By detecting the change with time of the image carrier 150 before determining the agent deterioration and confirming that it is normal, the agent deterioration can be determined with high accuracy.

(15) By detecting changes with time (scratches, dirt, filming, film thickness change, potential change, residual charge) of the image carrier 150 before determining agent deterioration, and confirming that it is normal, Although the developer is not actually deteriorated, it can be determined that the developer is deteriorated and the developer is not replaced.

1 is a diagram showing an entire full-color image forming apparatus of a dry two-component development system in which photosensitive drums as latent image carriers according to an embodiment of the present invention are arranged in tandem. FIG. 2 is a diagram illustrating an image forming unit of a dry two-component developing full-color image forming apparatus in which the photosensitive drums in FIG. 1 are arranged in tandem. FIG. 3 is a diagram illustrating an initial image of a halftone dot image formed on a recording medium by the image forming apparatus of FIG. 2 having a 600 dpi writing system. FIG. 3 is a diagram showing an image after printing for a very long time under certain conditions of a halftone image formed on a recording medium by the image forming apparatus of FIG. 2 having a 600 dpi writing system. It is a figure which shows the visual spatial frequency characteristic by the average test subject regarding density nonuniformity. 1 is a diagram illustrating a schematic configuration of an image quality detection apparatus that measures fine density unevenness of an image and a control circuit of the image forming apparatus according to an embodiment of the present invention. It is a characteristic view which shows the relationship between the distance (beam diameter) of a scanning direction, and light quantity. 6 is a diagram showing the light amount (voltage) fluctuation from the amplifier circuit of the reflected light. It is a figure which shows the spatial frequency characteristic computed by the fast Fourier transform (FFT) from the measurement result of FIG. It is a figure which shows the relationship between visual noise amount and a spatial frequency. It is a figure which shows the total amount of the calculated visual noise. 1 is a schematic configuration diagram illustrating an image forming unit of a direct transfer type monochrome image forming apparatus according to a first embodiment; 1 is a schematic configuration diagram illustrating an image forming unit of a full color image forming apparatus of a quadruple tandem type intermediate transfer system in a first embodiment. 1 is a schematic configuration diagram illustrating an image forming unit of a full-color image forming apparatus of a quadruple tandem direct transfer method according to a first embodiment. It is a schematic block diagram which shows an example of the sensor part of the image quality detection apparatus used in 1st Example. It is a figure which shows the state at the time of the detection of the image quality detection sensor which detects regular reflection light. It is a figure which shows the state at the time of the detection of the image quality detection sensor which detects irregularly reflected light. FIG. 5 is a diagram conceptually depicting the state of reflection for each of four combinations of surface optical characteristics and toner color, assuming that the color of the image carrier is black with no sensitivity. It is a figure which shows the relationship between the glossy surface and diffusion surface in the combination shown in FIG. 18, and regular reflection and irregular reflection. It is a figure which shows the computing equation, pattern, and characteristic at the time of detecting and calculating graininess. It is a figure which shows the comparison with the index of graininess, and the granularity of the image on actual paper. It is a figure which shows the frequency pattern used for the calculation and control of sharpness. It is a figure which shows the state of a graininess fluctuation | variation at the time of controlling combining a developing bias and a developing sleeve linear velocity. It is a figure which shows the correlation with the sensor output in a halftone image pattern, and an actual density | concentration. FIG. 6 is a characteristic diagram showing temperature dependence of toner density on an image carrier. FIG. 6 is a characteristic diagram showing humidity dependency of toner density on an image carrier. FIG. 6 is a characteristic diagram showing temperature dependence of image quality of an image formed on an image carrier. FIG. 4 is a characteristic diagram showing humidity dependency of image quality of an image formed on an image carrier. It is a figure which shows arrangement | positioning of the detection means for detecting a time-dependent change. FIG. 6 is a characteristic diagram illustrating a relationship between developer deterioration and granularity. FIG. 6 is a characteristic diagram showing a relationship between developer deterioration and toner adhesion amount (density) on a photoreceptor. It is a figure which shows the measurement data of the electric charge Q / particle diameter d with an initial stage agent and a deterioration agent. 2 is a block diagram illustrating a control configuration of the image forming apparatus. FIG. 6 is a flowchart showing a control procedure for image formation in consideration of agent deterioration determination and agent deterioration determination. FIG. 6 is a schematic configuration diagram illustrating a main part of an image forming unit of an image forming apparatus according to a second embodiment in which a sensor is provided to face an intermediate transfer belt. FIG. 10 is a schematic configuration diagram illustrating a main part of an image forming unit of an image forming apparatus according to a third embodiment in which a sensor is provided to face the recording paper conveyance belt. FIG. 10 is a schematic configuration diagram illustrating a main part of an image forming unit of an image forming apparatus according to a fourth embodiment in which a sensor is provided to face the recording paper conveyance belt. It is a schematic block diagram of a sensor unit for detecting a detection pattern transferred onto a dedicated transfer roller with a sensor head. It is a figure which shows the relationship between a glossy surface and a diffused surface, regular reflection, and irregular reflection in the case similar to the combination shown in FIG. 18 of the pattern for a detection transcribe | transferred on the exclusive transfer roller.

Explanation of symbols

1 Image forming unit 1a Operation display unit 1e External I / F
5 Intermediate transfer belt 51 Secondary transfer roller 53 Primary transfer roller 61 Photoconductor 62 Charging unit 63 Developing unit 69 Recording paper transport belt 100a Sensor 100c Sensor unit 109a Dedicated transfer roller 101 Light emitting elements 102, 104, 106 Lens 103 Light receiving element 105, Reference Signs List 107 fiber 108 sensor head 130 arithmetic circuit 130a arithmetic unit 150 image carrier CON control circuit P recording paper

Claims (28)

In an image forming apparatus that includes a developer deterioration degree detection unit that detects a degree of developer deterioration, and forms a toner image developed by the developer on a recording medium.
Image quality detecting means for detecting the image quality of the image formed on the image carrier;
Control means for determining whether or not to replace the developer based on the detection results of the developer deterioration degree detecting means and the image quality detecting means;
An image forming apparatus comprising: The image quality detecting means is
An image quality detection pattern forming means for forming an image quality detection pattern on the image carrier;
A reflected light amount detecting means for detecting a reflected light amount from the image quality detecting pattern formed by the image quality detecting pattern forming means in a minute region;
A computing means for computing the characteristics of the image formed on the image carrier based on the reflected light quantity detected by the reflected light quantity detecting means;
The image forming apparatus according to claim 1, further comprising: The image quality detecting means is
A dedicated transfer member to which a pattern formed on the image carrier is transferred;
A reflected light amount detecting means provided facing the dedicated transfer member;
A computing means for computing the characteristics of the image formed on the transfer member based on the reflected light quantity detected by the reflected light quantity detecting means;
The image forming apparatus according to claim 1, further comprising a unit.   4. The image forming apparatus according to claim 1, wherein the control unit controls image quality based on a detection result of the image quality detection unit.   The image forming apparatus according to claim 4, wherein the image quality control is performed by combining at least two of a developing bias, a developing sleeve linear velocity, an LD output, and a charging grid bias. Further comprising density detection pattern forming means for forming a density detection pattern on the image carrier,
4. The image forming apparatus according to claim 1, wherein the image quality detecting unit detects a toner density from a density detection pattern formed by the density detection pattern forming unit.   7. The image forming apparatus according to claim 6, wherein the image quality detecting unit detects a density of a non-image portion of an image carrier on which the density detection pattern is not formed, in addition to the density of the density detection pattern. apparatus. Further comprising aging detection means for detecting aging of the image carrier,
8. The control unit according to claim 1, wherein after the aging change is detected by the aging change detection unit, the detection is performed by the developer deterioration degree detection unit and the image quality detection unit. The image forming apparatus described.   The secular change detected by the secular change detecting means includes at least one of scratches, dirt, filming, image portion and non-image portion potential, film thickness, and residual potential of the image carrier. The image forming apparatus according to claim 8.   The aging detection means detects a state of aging based on a preset threshold value, and when the control means determines that the aging change affects image quality, the control means changes the threshold value. 10. The image forming apparatus according to claim 8, wherein the state of secular change and the influence on the image quality are determined again.   The image forming apparatus according to claim 1, wherein the image carrier is any one of a photosensitive member, an intermediate transfer member, a recording paper conveying member, and a dedicated transfer member.   12. The display device according to claim 1, further comprising display means for displaying at least one result of a detection result of the secular change detection means, a detection result of the image quality detection means, and a determination result of the control means. 2. The image forming apparatus according to item 1.   13. The image forming apparatus according to claim 12, wherein after the display of the result, the control unit causes the display unit to display whether to continue image formation.   12. A transmission unit for transmitting at least one of a detection result of the secular change detection unit, a detection result of the image quality detection unit, and a determination result of the control unit to an external device. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 1, further comprising an input unit through which a user inputs an instruction to execute image formation even when image quality cannot be guaranteed. In a process cartridge used in an image forming apparatus for forming a toner image developed by the developer on a recording medium, the developer deterioration degree detecting means for detecting the degree of deterioration of the developer.
An image quality detection unit configured to detect the image quality of an image formed on the image carrier, and a control unit provided on the image forming apparatus side based on detection results of the developer deterioration degree detection unit and the image quality detection unit; A process cartridge for determining whether or not to replace a developer. The image quality detecting means is
An image quality detection pattern forming means for forming an image quality detection pattern on the image carrier;
A reflected light amount detecting means for detecting a reflected light amount from the image quality detecting pattern formed by the image quality detecting pattern forming means in a minute region;
A computing means for computing the characteristics of the image formed on the image carrier based on the reflected light quantity detected by the reflected light quantity detecting means;
The process cartridge according to claim 16, further comprising: The image quality detecting means is
A dedicated transfer member to which a pattern formed on the image carrier is transferred;
A reflected light amount detecting means provided facing the dedicated transfer member;
A computing means for computing the characteristics of the image formed on the transfer member based on the reflected light quantity detected by the reflected light quantity detecting means;
17. The process cartridge according to claim 16, wherein the process cartridge is unitized. In an image forming method for forming a toner image developed by the developer on a recording medium, the developer deterioration degree detecting means for detecting the degree of deterioration of the developer.
An image quality detection pattern forming step of forming an image quality detection pattern on the image carrier;
A calculation step of detecting an amount of reflected light from the image quality detection pattern formed in the step of forming the image quality detection pattern and calculating image characteristics;
A determination step of determining the degree of image quality degradation from the image characteristics calculated in the calculation step;
An image quality control step of executing image quality control when the degree of image quality degradation determined in the determination step is smaller than a preset level;
An image forming method comprising: In an image forming method for forming a toner image developed by the developer on a recording medium, the developer deterioration degree detecting means for detecting the degree of deterioration of the developer.
An image quality detection pattern forming step of forming an image quality detection pattern on the image carrier;
A calculation step of detecting an amount of reflected light from the image quality detection pattern formed in the step of forming the image quality detection pattern and calculating image characteristics;
A determination step of determining the degree of image quality degradation from the image characteristics calculated in the calculation step;
A density detection pattern forming step for forming a density detection pattern on the image carrier when the degree of image quality degradation determined in the determination step is greater than or equal to a preset level;
A density detection step for detecting a density detection pattern formed in the density detection pattern formation step and a density of a portion where the density detection pattern is not formed;
An agent deterioration determination step for determining the degree of developer deterioration based on the concentration detected in the concentration detection step;
An image forming method comprising: Before performing the image quality detection pattern forming step,
A temporal change detection step for detecting a temporal change of the image carrier;
A temporal change determination step for determining whether there is a temporal change based on the detection result detected in the temporal change detection step;
When it is determined that there has been a change over time in the time change determination step, an image quality influence determination step of determining whether the change over time affects the image quality;
A replacement instruction step for instructing and / or displaying replacement of a member that has been determined to have changed over time if the influence on the image quality cannot be eliminated even if the determination criteria are changed in the image quality influence determination step;
The image forming method according to claim 19 or 20, further comprising: Before performing the image quality detection pattern forming step,
A temporal change detection step for detecting a temporal change of the image carrier;
A temporal change determination step for determining whether there is a temporal change based on the detection result detected in the temporal change detection step;
When it is determined that there is a change over time in the time change determination step, an image quality influence determination step of determining whether the time change affects image quality;
With
21. The image formation according to claim 19 or 20, wherein if the determination criterion is changed in the image quality influence determination step and the influence on the image quality is eliminated, the process proceeds to the image quality detection pattern formation step. Method. It further comprises a temperature and humidity detection process for detecting the temperature and humidity in the device,
21. In the agent deterioration determination step, the degree of deterioration of the developer is determined from the concentration detected in the concentration detection step based on the temperature and humidity detected in the temperature and humidity detection step. The image forming method described.   The image forming method according to claim 20 or 23, further comprising a transmission step of transmitting the determination result of the agent deterioration determination step to an external device.   24. The image forming method according to claim 20, further comprising a display step of displaying the determination result of the agent deterioration determination step on a display unit.   An image forming step for displaying whether or not to continue image formation regardless of the determination result of the agent deterioration determining step and performing an image formation when instructed to continue the image formation is provided. The image forming method according to any one of claims 20, 23, 24, and 25.   A computer program comprising a procedure for executing the image forming method according to any one of claims 19 to 26 on a computer. A recording medium on which the computer program according to claim 27 is read and recorded so as to be executable.

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