JP4580666B2 - Image forming apparatus, image quality management method, computer program, and recording medium - Google Patents

Description

  The present invention relates to an image forming apparatus that forms a visible image on a recording medium using toner, an external management apparatus that is communicably connected to the image forming apparatus, the image forming apparatus, or the external management apparatus to the image forming apparatus. The present invention relates to an image quality management method for managing image quality of an image formed by the above, a computer program for executing this image quality management by a computer, 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 these, in Patent Document 1, each image is used in an image quality diagnosis system for an image recording apparatus in which the image quality of a plurality of image recording apparatuses that are diagnosis target terminals is individually diagnosed by the central diagnosis apparatus via the central management apparatus. The recording apparatus is provided with storage means for storing main parameters of image quality control, and a terminal to which the main parameters of image quality control stored in the storage means are transferred to the central management apparatus side at the time of image quality diagnosis Side data transfer means is provided, and the terminal side data transfer means predicts the failure location when it is recognized that an abnormality has occurred in the main parameter of image quality control or when there is a possibility that an abnormality will occur. On the other hand, in the central diagnostic device, the main parameters of image quality control are normal depending on the image quality state. In addition to providing a pattern table for image quality diagnosis that is pre-patterned with regard to whether or not there is an abnormality and what kind of trouble is expected, the main image quality control transferred from the terminal-side data transfer means is provided. An image quality state determining means for determining which pattern of the image quality diagnosis pattern table matches and determining the image quality state is provided, and at least the terminal side data under the condition that the failure prediction is performed by the failure prediction means An invention is disclosed in which main parameters of image quality control are transferred from the transfer means to the central management apparatus side.

  Japanese Patent Application Laid-Open No. 2004-268531 discloses that in an image forming apparatus that stores defect occurrence information, a detection unit that detects a defect, and the image forming apparatus is in an operation-prohibited state in accordance with the content of the detected defect. A first control unit, a second control unit that maintains the operable state by setting the operation setting of the image forming apparatus to an operation setting different from the standard according to the content of the detected defect, and the second control unit The detection means for detecting the state as an inappropriate state when the operation setting differs from the standard, the time measuring means for generating date information and time information, and the inappropriateness including the contents of the inappropriate state and the occurrence date and time An invention is provided in which an improper status data storage means for storing status data and an improper status data display means for displaying the improper status data in order of occurrence date and time are provided. It is.

Further, in Patent Document 3, in an image quality detection device that detects image quality based on a predetermined image pattern formed on an image carrier, the image pattern and the image carrier on which the pattern image is formed are disclosed. A light emitting means for irradiating spot light; a scanning means for scanning the image pattern with the spot light; and a light quantity reflected or transmitted through the image pattern and the image carrier in the scanning process by the scanning means. And a light receiving means, and the diameter of the spot light in the scanning direction in the previous period is set to be equal to or less than the reciprocal of the spatial frequency that maximizes human visual sensitivity.
JP 2001-22232 A Japanese Patent No. 2780348 JP 2004-53944 A

  2. Description of the Related Art Conventionally, in an electrophotographic apparatus, a diagnostic system for controlling image quality deterioration due to environmental changes and temporal changes has been performed. For example, in the invention described in Patent Document 1, the influence of main parameters of image quality control on image quality is examined in advance using an actual machine and patterned. These are compiled into a table and stored in the central management apparatus as a pattern table for image quality diagnosis. Data is transmitted from the image recording apparatus to the central management apparatus under the condition that main parameters of image quality control are detected by the individual image recording apparatuses and failure prediction is performed by the failure prediction means. The central management device determines which pattern in the image quality diagnosis pattern table matches the transmitted main parameter of image quality control, and determines the image quality. Further, the central management apparatus performs image quality control by rewriting main parameters of image quality control of the image recording apparatus.

  However, in this known technique, what is detected is the main parameter of image quality control, not the image quality itself. In addition, the effect of parameters on image quality is examined in advance with an actual machine, but there are a wide variety of environments and usages in which an image recording apparatus is actually installed. Therefore, it is impossible to create a pattern table that covers all the patterns, and the image quality determined using the pattern table stored from the main parameters is different from the image quality of the actual image recording apparatus. End up. Therefore, accurate image quality management cannot be performed.

  Also in the invention described in Patent Document 2, a physical property value associated with an electrophotographic process is measured by a sensor, and process control is performed based on the output. If it is determined that the measured state is an inappropriate state, the state is transmitted to an external management device. However, even in this example, what is detected is a physical property value associated with the electrophotographic process, not the image quality itself. Therefore, management of the image forming apparatus based on the image quality cannot be performed accurately.

  The invention described in Patent Document 3 exemplifies a method for detecting image quality. However, consideration is given to identifying a location that has caused image degradation based on the detected image quality and controlling the image quality to be restored. Not.

  The present invention has been made in view of the situation of the prior art as described above, and an object of the present invention is to identify a portion where the image quality is deteriorated when the image quality is deteriorated and to easily manage the image quality. is there.

In order to achieve the object, the first means includes a pattern forming means for forming an image quality detection pattern on the image carrier, and a reflected light amount from the pattern formed on the image carrier by the pattern forming means. In an image forming apparatus comprising a detecting means for detecting in a minute area and having means for evaluating image quality based on the detection output of the detecting means, the temperature inside the machine, the humidity inside the machine, the toner density in the developing unit, the image carrier State quantity detection means for detecting a state quantity including at least one of the toner adhesion amount, the image / non-image part potential on the photoreceptor, and the transfer bias, and the graininess and sharpness from the detection result of the detection means and calculating means for calculating an image characteristic including at least one tonality, and a degradation determiner means deterioration of the image characteristics on the basis of the calculation result of the calculating means, Starring of the arithmetic means Control means for setting a control parameter including at least one of a developing bias, a charging grit bias, an LD power, and a developing sleeve linear velocity based on the result, and performing image formation based on the set control parameter; and the state quantity State history creating means for creating a state history from the state quantity detected by the detecting means, the calculation result of the image characteristic computed by the computing means, and the control parameter set by the control means, and the detected state quantity Identifying means for identifying a location where an abnormality has occurred in the image forming apparatus from the calculated calculation result, the set control parameter, and the created state history , and the control means includes the deterioration determination means The image characteristic is determined to be deteriorated, and the deterioration is determined by the control parameter. When it is determined that recovery is possible by changing the meter, the control parameter is changed, and the image quality detection pattern is formed again to determine the deterioration of the image characteristics. The state history is created when it is determined by the means that the image characteristic is not deteriorated, and the specifying means is a case where the deterioration determining means determines that the image characteristic is deteriorated and When it is determined that the deterioration cannot be recovered by changing the control parameter, a location where an abnormality has occurred is specified .

The second means further comprises storage means for storing and accumulating the state history generated by the first means.

The third means is characterized in that, in the first or second means, the detection means is provided at the final stage of the image forming process immediately before fixing the image .

A fourth means is an image quality management method for determining an image quality state from an image quality detection pattern formed on an image carrier of an image forming apparatus and managing the image quality based on the determination result. Detecting a state amount including at least one of a toner density in the developing unit, a toner adhesion amount on the image bearing member, a potential of an image portion / non-image portion on the photosensitive member, and a transfer bias; A step of calculating image characteristics including at least one of graininess, sharpness, and gradation based on a pattern detection result; a step of determining a deterioration state of image quality from the calculation result of the calculation; and the deterioration state If it is determined that the image quality is deteriorated in the determining step, the image quality is changed by changing a control parameter including at least one of a developing bias, a charging grit bias, an LD power, and a developing sleeve linear velocity. If it is determined that recovery is possible in the step of determining whether recovery is possible and the step of determining whether recovery is possible, the image quality detection pattern is formed again by changing the control parameter, A step of determining a deterioration state of image quality; a step of creating a state amount history from the calculation result of the state amount, the control parameter, and the image quality characteristic if the image quality is not deteriorated by the determination; If it is determined in the step of determining whether or not recovery is possible, recovery is performed based on the detected state quantity, the calculated calculation result and the set control parameter, and the created state history. And a step of identifying the impossible portion .

The fifth means is a computer program for controlling the image quality of an image that is loaded into the image forming apparatus and forms an image. The temperature inside the machine, the humidity inside the machine, the toner concentration in the developing unit, and the toner adhesion on the image carrier. A first procedure for detecting a state quantity including at least one of a quantity, a potential of an image area / non-image area on the photosensitive member, and a transfer bias, and a developing bias, a charging grit bias, an LD power, and a developing sleeve linear velocity. A second procedure for detecting a control parameter including at least one, a third procedure for forming a detection pattern, and a fourth procedure for detecting the amount of reflected light from the detection pattern formed in the third procedure. And a fifth procedure for calculating image characteristics including at least one of graininess, sharpness, and gradation from the amount of reflected light detected in the fourth procedure, and a fifth procedure. If the image quality is determined to be deteriorated in the sixth procedure for determining the image quality deterioration based on the image characteristics and the determination in the sixth procedure, the image quality is determined as the development bias, the charging grit bias, and the LD power. And a seventh procedure for determining whether or not recovery is possible by changing a control parameter including at least one of the developing sleeve linear velocity and a determination as to whether or not recovery is possible in the seventh procedure. In this case, the control parameter is changed, the image quality detection pattern is formed again, and the image quality is not deteriorated by the determination in the eighth procedure and the determination in the sixth procedure again. Are unrecoverable in the ninth procedure for creating a state history from the calculation result of the state quantity, the control parameter, and the image quality characteristic, and the determination as to whether or not recovery is possible in the seventh procedure. If it is determined, the detected state quantity, and a tenth step of specifying the irreversible point based on the calculated operation result and the set control parameters and state history created in the above It is characterized by.

A sixth means is characterized in that the computer program according to the fifth means is read by a computer and recorded on a recording medium so as to be executable .

  According to the present invention, when the image quality is deteriorated, it is possible to specify the portion where the image quality is deteriorated, and thus the image quality can be easily managed.

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 so-called paper discharge tray 4 is provided, and the discharged recording paper on which an image has been formed 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. First, yellow (
Y) develops yellow (Y) toner in the image forming section, and transfers the primary transfer device (on the intermediate transfer belt 5).
The image is transferred by a 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, transfers it to the intermediate transfer belt 5, and finally develops the black (K) toner.
The image is transferred onto the intermediate transfer belt 5 to form a full-color toner image in which four colors are superimposed.

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. This read image signal is
Digitized and image processed. 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 are halftone images formed on the recording paper 20 by the image forming apparatus MFP 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 photography), FIG. 3 shows an initial image PT1, and FIG. 4 shows a very long period under certain conditions. The image PT2 after performing the transition 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 includes a light reflection type sensor (photo reflector) 110, an amplification circuit 120 that amplifies an electric signal from the light reflection type sensor 110, and the amplification circuit 120.
An arithmetic circuit 13 as arithmetic means for performing predetermined arithmetic processing based on the signal amplified by
0 and a signal generation circuit 140 as signal generation means for generating a signal for optical writing control based on the calculation output from the calculation 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 light emitted from the LED 101 into a light beam having a predetermined beam diameter, and an image carrier 150. Photoelectric conversion element (light receiving element) 1 that receives reflected light from the image pattern 151 and converts it into an electrical signal
03 and an imaging lens 104 that forms an image of the reflected light from the image pattern 151 on the imaging surface of the photoelectric conversion element 103. As can be seen from the characteristic diagram showing the relationship between the distance in the scanning direction (beam diameter) and the amount of light in FIG.
A light reflection type sensor with P is used.

The light reflection sensor 110 converts an irradiation beam from a light source including the LED 101 into the condenser lens 1.
The circular beam diameter on the surface of the image pattern 151 formed on the image carrier 150 is approximately 400 [μm]. 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 by 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 of 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 of FIG.
This is an example in which a detection method using a difference in irregular reflection characteristics between the toner particles 152 and the surface of the image carrier 150 is performed using the LED 101 having an emission wavelength of [nm]. Figure 5 shows the beam diameter.
About 1 [cycle / which is the most sensitive in the spatial frequency characteristics of human vision as shown in FIG.
mm], at least the beam diameter (d1 in FIG. 7) in the scanning direction of the spot light SP 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 a configuration of an image forming process of the image forming apparatus MFP 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. 3 to the pattern (image PT2) shown in FIG.
It is possible to know the degree of image quality degradation for the image PT1). 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. Also,
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 a 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.
0 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 The amount of visual noise shown in FIG. 10 is calculated from 0.2 [cycle / mm] using the arithmetic circuit 130.
When integration is performed with respect to a spatial frequency region of 4 [cycle / mm], the total amount of visual noise is calculated as shown in FIG. 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, a specific wavelength (color)
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. For example, the dot array repetition period z1 is approximately 1
Assuming 70 [μm] (spatial frequency f1 is approximately 5.9 [cycle / mm]), when scanning is performed with the spot light SP having a beam diameter of about 400 [μm] as described above, FIG. As shown, a spectrum appears at a spatial frequency near 6 [cycle / mm]. 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 250 [μm].
And preferably smaller than 200 [μm]. 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. CPU is not shown ROM
Alternatively, each processing is executed using a RAM (not shown) as a work area based on the downloaded program. The program data is downloaded from a server via a network (not shown) or from a recording medium such as a CD-ROM or an SD card to a storage device such as a hard disk (not shown) via a recording medium driving device (not shown).
Alternatively, version upgrade is performed.

2. First Embodiment 2.1 Image Forming Unit FIGS. 12 to 14 are diagrams showing a main part of an image forming apparatus MFP 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. Are arranged, and the primary transfer roller 53 and the photoreceptor 61 are arranged.
A recording paper conveyance belt 69 is passed through the nip. A registration roller 23 is provided upstream of the recording paper conveyance belt 69 in the paper conveyance direction, and a fixing roller 8a and a pressure roller 8b are provided downstream.
A fixing unit 8 is provided. Exposure is performed by the charging unit 62 and the developing unit 6.
3 is performed by a laser beam emitted from an exposure unit (not shown) in an exposure unit 65 provided between the exposure unit 65 and the exposure unit 65. In the embodiment shown in FIG. 12, the image quality detection sensor 100a is provided at a position facing the recording paper transport belt at the end of the recording paper transport belt 69 on the most downstream side in the paper transport direction. This position corresponds to the last stage before fixing in the image forming process. This position is a position for detecting an image close to the image on the recording paper. The position is not limited to the above position, and may be a position immediately before transfer to the recording paper, a position immediately after transfer to the recording paper conveying member instead of the recording paper, or a position immediately before transfer from the photosensitive member 61 to the transfer target. However, in these cases, it is impossible to detect deterioration in image quality caused by secondary transfer. The same applies to the following examples. Reference numeral 68 denotes a temperature / humidity sensor for detecting the atmospheric temperature and humidity in the machine.

  FIG. 13 shows an image forming unit corresponding to FIG. 2, and the point that the recording paper conveyance belt 69 is shown in FIGS. 1 and 2 is different from the arrangement of the image quality sensor 100a. Is omitted. Similar to the case of FIG. 12, the image quality sensor 100a is provided to face the end of the recording paper transport belt 69, which is the last stage before fixing in the image forming process.

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 image quality sensor 100a is provided so as to face the end of the recording paper transport belt 69, which is the last stage before fixing in the image forming process, as in FIG. 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.

  Although the feedback control system is not shown in this figure, the CPU of the control circuit CON of the image forming apparatus MFP main body receives the output from the arithmetic circuit 130 and applies feedback control.

In image forming apparatus MFP that performs such an image forming operation, when detecting image quality,
An image quality detection pattern 200 is formed on the photoconductor 61, an amount of reflected light from the pattern 200 is detected in a minute region, and an arithmetic circuit 130 for calculating the characteristics of the image from the detection result is provided to detect the 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 MFP main body receives the output from the arithmetic circuit 130 as shown in FIG.

An LD, LED, or the like is used for the light emitting element 130, and light from these is collimated lens 1.
02 enters the optical fiber 105. 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 image carrier (detection target)
The detection pattern 151 including the photosensitive member 150 and the toner image on the surface 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, this 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,
And so on.

The image quality detection sensor 100a including the detection unit 111 and the arithmetic circuit 130 shown in FIG. 15 is configured to detect the image immediately before the image fixing in FIGS. 12 to 14, and the image transferred onto the recording paper 20 An image close to 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, and in FIG.
In FIG. 7, the diffused light is diffused by installing a coaxial fiber in which the light projecting fiber 105 and the light receiving fiber 107 are formed coaxially with respect to the detection surface in FIG. It shows a state of receiving light. 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 it should be detected by specular reflection light or irregular reflection light is determined by the image carrier (photosensitive member) 15.
It is determined by a combination of 0 color, surface optical characteristics, and toner color. The color or toner color of the image carrier 150 is sensitive to the projection wavelength.
A surface optical characteristic of 0 is whether it is a glossy surface (reflects light in a specular reflection manner) or a diffusion surface (reflects light in an irregular reflection manner). Further, the toner image 152 on the image carrier 150 has a property of scattering light diffusely. For the sake of clarity, the light source wavelength is set to 6 below.
50 nm. 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, paying attention to the reflection from the surface of the image pattern 151, (a) and (b) are M toner,
(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 is (a), (c
) Means that regular reflection light is generated from the surface of the photoreceptor (black, glossy surface). 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, the patches 200a to 200i are detected as shown in FIG.
Sensor output raw data with respect to the time of the middle left end 200a can be taken. 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, this SS (f) is multiplied by VTF, which is the spatial frequency characteristic of human vision,
Lightness 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
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. MTF
Since there are various methods for calculating the above, there is no particular description here, but actually, a sensor capable of detecting a minute area density of the frequency pattern 210 as shown in FIG. 21, for example, the image quality detection sensor 100a shown in FIG. 6 or FIG. It is realistic to detect, analyze, and calculate with this. 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. Development bias, charging grid bias, and LD power are development potential (potential development ability)
The development sleeve linear velocity is an adjustment of the 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. 22 shows how the graininess fluctuates 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. 22 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 development sleeve linear velocity are controlled in combination, but the development bias, charging grid bias, and LD power are factors that change the development potential.
The same effect can be obtained by controlling other combinations (charging grid bias and developing sleeve linear velocity, or LD power and developing sleeve linear velocity), or a combination of these four factors. Thus, the range of image quality control can be expanded by combining control factors. The above detection / control is periodically performed in the image forming apparatus MFP. Various timings are conceivable, such as when the power is turned on, every certain number of output sheets, every certain period of time, or forcibly performed by the user or service person, but is not particularly limited here.

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.

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. The installation position of the temperature / humidity sensor 68 is shown in FIG.
Various positions other than the positions shown in 2 to 14 are conceivable, and the installation position is not limited. Any position can be used as long as it can detect the temperature and humidity of the image quality formation area in the image forming apparatus MFT. However, in the vicinity of the fixing unit 8, the image forming apparatus M is affected by the temperature of the fixing roller 8 a.
Since the temperature and humidity in the FT cannot be accurately detected, it is necessary to avoid the vicinity of the fixing unit 8.

  As the temperature rises, the density (toner adhesion amount) on the image carrier (photoconductor) 150 increases, and as the humidity increases, the density (toner adhesion amount) on the image carrier (photoconductor) 150 also increases. In addition, the image quality improves as the temperature is raised from a low temperature, takes a minimum value in the vicinity of 15 to 20 ° C., and becomes worse as the temperature is further raised. The image quality is also dependent on humidity and changes in the same way as 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 is stained with paper dust or residual toner,
Scratches and scraping occur due to discharge at the time of transfer and wear at the cleaning portion, and surface degradation occurs over time. 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,
Information on surface deterioration is transmitted to the external management device.

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 changes over time, for example, the first potential sensor is located downstream of the quenching lamp 67 in the direction of rotation of the photosensitive member, the filming detection sensor is located further downstream, and the exposure unit 65 is located downstream. A second potential sensor is provided at the same time, and a film thickness detector 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 value of the current flowing into the surface of the photoconductor 61 at the time of charging with a film thickness measuring instrument. This is done by detecting the potential of the surface of the photoreceptor 61 with a second potential sensor. The remaining charge after the charge removal is performed by detecting the surface potential of the photoreceptor 61 after the charge removal by the quenching lamp 67 with the first potential sensor. 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. 25 is a characteristic diagram showing the relationship between developer degradation and granularity. "Initial" of the deterioration state
Is a new developer and does not deteriorate 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. From FIG. 25, it can be seen that the granularity value increases as the developer deteriorates, and the image quality deteriorates.

FIG. 26 is a characteristic diagram showing an example of the relationship between the deterioration of the developer and the 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. 26 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. 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. 23 is a block diagram illustrating an outline of a 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
Each sensor 100b is connected to the control circuit CON. The control circuit CON is
The control desired by the user is executed by an instruction input from the operation display unit 1a, and the image data read by the scanner unit 3 is temporarily stored in the image memory 1c, and then predetermined or desired image processing is performed by the image processing unit. 1b, output to the writing unit 7, image 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.
Or it carries 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. 24 is a flowchart showing a control procedure in the first embodiment of the present invention that creates a state history based on the detected state quantity and identifies an abnormal part therefrom.

  In the process of identifying the abnormal part, the state quantity and the state history information are important elements. The state quantity is a parameter that affects the image quality other than the control parameter. The temperature and humidity in the image forming apparatus MFP, the toner density in the developing device, the toner adhesion amount, and the image / non-image part potential on the photoconductor. , Transfer bias, and the like. These parameters are parameters representing the state of the image quality forming apparatus when image quality detection / control is performed. The state history information is information in which changes over time such as changes in state quantities, calculation results of image characteristics, and changes in parameters are recorded. The idea of creating this state history information is the most important idea of the present invention, and since the state history information has been created, this history information is used to identify abnormal parts (parts where image quality degradation that cannot be recovered occurs). I was able to do it.

  Therefore, in this process, first, the state quantity, here, the temperature and humidity in the image forming apparatus MFP, the toner density in the developing unit, the toner adhesion amount, the image / non-image part potential on the photosensitive member, and the transfer bias are calculated. Detect (step S101). Thereafter, control parameters for image formation, such as a developing bias, a charging grid bias, an LD current, and a developing sleeve linear velocity are detected (step S102). Next, an image quality detection pattern is formed on the image carrier (step S103). The image carrier here is primarily the photoconductor 61, and what is actually detected is the image quality detection sensor 100a. A secondary image pattern is formed on the intermediate transfer belt 5 transferred from the photosensitive member 61 that moves to a position opposite to the intermediate transfer belt 5. The detection light is projected onto the secondary pattern, and the reflected light from the image quality detection pattern is detected as described above (step S104). Then, image quality characteristics such as graininess, sharpness, and gradation are calculated from the reflected light as described above (step S105), and it is determined from the calculation results whether the image quality has deteriorated (step S106). ). This determination is performed by comparison with a predetermined threshold value. As described above, the cause of image quality deterioration includes factors such as agent deterioration, environmental change, and deterioration over time. Regardless of any cause, image deterioration is determined in this step.

  If it is determined in step S106 that the image quality has not deteriorated, the state quantity detected in step S101, the control parameter detected in step S102, and the image characteristics calculated in step S105 are stored together with the date and time when the image quality detection was performed. The stored state quantities, control parameters, and image characteristics are stored as history information since they are stored every time image quality is detected (step S107). That is, the date and time when image quality detection / control was performed, the calculation result at that time, the value of the control parameter, and the state quantity at that time are created and stored as a state history. This state history is updated each time image quality is detected and controlled.

  On the other hand, if it is determined in step S106 that the image quality has deteriorated, it is next determined whether the deterioration can be controlled by changing the control parameter (step S108). This determination is also made by comparison with a predetermined threshold value of image quality characteristics. If it is determined in step S108 that control is possible, the change of the control parameters (development bias, charging grid bias, LD current, development sleeve linear velocity) is changed (step S109), and the process returns to step S102. In actuality, the control parameter is changed by measuring in advance how the calculation result and the toner adhesion amount change with a combination of the values of the respective control parameters, and using the result as a table in the image forming apparatus MFP. Stored in the nonvolatile memory 1d. In step S109, the control parameter value in the table stored in the nonvolatile memory 1d is selected based on the calculation result and the adhesion amount when the image quality is detected, and the control parameter value is changed.

  In step S102, the changed control parameter is detected, and the processes after step S103 are repeated. If it is determined again that the image quality has deteriorated in step S106, the loop processing of steps S102, S103, S104, 105, S106, S108, and S109 is repeated until it is determined that the image quality has not deteriorated. If it is determined that the image quality has not deteriorated, the state history is created as described above (step S107).

  If it is determined in step S106 that the image quality has deteriorated, and if it is determined in step S108 that control is not possible even by changing the control parameter, an abnormal part is specified in step S110. The abnormal part is specified based on the state history information created in step S107. Here, an example in the case where the abnormality of the developer, the transfer bias, and the photoreceptor is specified will be described.

1) In the case of developer It is well known that the developer deteriorates with time, and when the developer deteriorates as described above, the image quality and the charging characteristics of the developer are affected. As can be seen from FIG. 25 described above, as the degree of deterioration increases as compared with the initial agent, the granularity also increases and the image quality deteriorates. Since the charging bias, LD power, and developing bias of the photosensitive member 61 are all constant, the developing potential that is the difference between the image portion potential and the developing bias is also constant in both the initial agent and the deterioration agent. Therefore, looking at FIG. 26 described above, the amount of adhesion decreases as the degree of deterioration increases compared to the initial agent. This indicates that the charge amount is increased because the development potential is constant. In image forming apparatus MFP, the amount of adhesion on photoreceptor 61 is controlled to be constant. Therefore, when the charge amount increases due to the deterioration of the developer, the adhesion amount becomes constant by increasing the development potential.

  FIG. 27 shows the variation with time in granularity and development potential. The horizontal axis represents the number of output images of image forming apparatus MFP. The granularity fluctuates upward with time, and the development potential also fluctuates upward. This indicates that the charge amount of the developer is increased because the constant amount of adhesion is controlled. Therefore, it can be specified that the image quality deterioration in this case is caused by the deterioration of the developer. Actually, the value of the development potential is obtained from the image portion potential and the development bias in the state history, and it is also checked whether it is controlled to be constant from the value of the adhesion amount. Thus, the deterioration of the developer can be specified from the image portion potential, the developing bias, and the adhesion amount in the state history.

2) In the case of transfer bias The transfer bias should be controlled to an appropriate value determined by humidity or the like, but if it fluctuates due to poor control or the like, it affects the image quality. FIG. 28 shows the temporal variation of the granularity and the transfer bias. The horizontal axis is an output image of image forming apparatus MFP. In FIG. 28, there are large fluctuations due to poor control of the transfer bias at two locations. It can be seen that the granularity also increases rapidly. From this result, it can be seen that the transfer bias greatly affects the image quality. Therefore, when the image quality deteriorates until it cannot be controlled, it is possible to identify an abnormality in the transfer portion from the transfer bias and humidity in the state history.

3) In the case of the photoconductor The photoconductor 61 deteriorates with time due to film thickness reduction, filming, light fatigue, and the like. Deterioration of the photoreceptor 61 also affects the charging characteristics. Even when the same charging bias is applied, the charged potential decreases due to deterioration. FIG. 29 shows potential fluctuations in the non-image area over time. The horizontal axis represents the number of output images of image forming apparatus MFP. It can be seen that the non-image portion potential is constant at the initial stage, but the value of the non-image portion potential decreases as the output image increases. If the charged potential of the photoreceptor decreases with time, the image quality in subsequent exposure, development, and transfer is also affected. Therefore, when the image quality deteriorates until it cannot be controlled, the abnormality of the photosensitive member 61 can be specified from the charging bias of the state history and the non-image portion potential.

  When the abnormal part is specified in step S110 in this way, the image quality deterioration that cannot be recovered in step S111 has occurred, and the occurrence point of the image quality deterioration specified in step S110 is displayed on the display unit of image forming apparatus MFP. indicate. Then, a service man call is performed. If the service center is connected to or can be contacted via a network or a public line, the service person is automatically informed of the contents. Since the service person knows where the image quality has deteriorated, if he / she visits the user with a corresponding replacement part, the maintenance will be performed quickly. If the abnormal portion cannot be identified in step S110, the display unit displays that the image quality is degraded, and further notifies the service person that the image quality degradation (image quality abnormality) has occurred.

  Apart from the above method, it is possible to detect a sign of occurrence of an abnormality using the state history and prevent the abnormality in advance. Image quality abnormality due to deterioration with time in image forming apparatus MFP does not occur suddenly but progresses gradually. Therefore, the sign of image quality abnormality due to deterioration with time can be known from the state history. In image quality detection and control, the image quality calculation result before control approaches the threshold for determining whether control is possible, or the image quality calculation result after control approaches the threshold for determination whether image quality is degraded. If so, it can be determined that this is a sign of an image quality abnormality. In that case, a part that affects the sign of image quality abnormality is identified from the state history. If it can be identified, the serviceman is informed of the abnormality sign and information on the specific part, and if it cannot be identified, the serviceman is informed of only the abnormality sign. By doing so, there is no downtime of image forming apparatus MFP, and abnormality can be prevented in advance. This control can be easily performed by changing the threshold value for determining whether control is possible in step S108, or by separately providing a threshold value for performing the above determination.

  In addition, there are various timings for detecting and controlling the image quality, such as when the power is turned on, every certain number of output sheets, every certain period of time, or forcibly performed by the user or serviceman, but is not particularly limited here.

3. Second Embodiment In the second embodiment, the control method in the first embodiment is changed. In the first embodiment, the state history is created in each image forming apparatus MFP. Then, a transmission means is installed in each image forming apparatus MFP, the image quality calculation result, the control parameter, and the state quantity at that time are transmitted to the external management apparatus, and the external management apparatus transmits each image forming apparatus based on the sent information. An MFP status history is created. The processing procedure of this embodiment is shown in the flowchart of FIG.

  Steps S101 to S106 are processed in the same manner as in the first embodiment. If it is determined in step S106 that the image quality has not deteriorated, the state quantity detected in step S101, the control parameter detected in step S102, and the image characteristics calculated in step S105 are temporarily stored together with the date and time when the image quality detection was performed. (Step S121). Then, the stored information is transmitted to the external management device SV (step S122). The external management device SV receives the transmitted information and temporarily stores it (step S124). Thereafter, the external management device SV creates a state history similar to the state history created in step S107 of the first embodiment based on the stored information (step S125). The created status history is stored in the storage device of the external management device SV, and the status history of each image forming apparatus MFP is updated each time information is transmitted from each image forming apparatus MFP.

  If it is determined in step S106 that the image has deteriorated, it is determined whether the degree of image quality deterioration can be controlled by changing the control parameter in the same manner as in step S108 in the first embodiment. In step S109, the control parameter is changed, the process returns to step S102, and the subsequent processes are repeated. The processes of steps S108 and S109 and steps S102 to S107 are the same as in the first embodiment.

  If it is determined in step S108 that control is impossible, the display unit displays that the image quality is degraded. Then, the state quantity already detected at that time (step S101), the control parameter (step S102), the calculation result of the image characteristics, and information for specifying which image forming apparatus is transmitted to the external management apparatus SV. (Step S123).

  The external management device SV identifies an abnormal part in the same manner as in step S110 described above from the transmitted state quantity, control parameter, calculation result of image characteristics and the state history created in step S125 (step S126). When the part is specified, the service person is notified of the specified abnormal part and information on the image quality deterioration. When the abnormal part cannot be specified, only the information on the image quality deterioration (image quality abnormality) is notified to the service person.

  In the second embodiment, the sign of the image quality abnormality is determined in the same manner as in the first embodiment, and the portion that affects the sign of the image quality abnormality is identified from the state history of each image forming apparatus. If it can be identified, the serviceman is informed of the abnormality sign and information on the specific part, and if it cannot be identified, the serviceman is informed of only the abnormality sign. By doing so, there is no downtime of each image forming apparatus, and abnormality can be prevented in advance.

  As described above, if the external management device SV is provided with the function of creating the state history and specifying the abnormal portion, the image forming device itself does not need to have the functions described above. Cost can be reduced.

  Note that the image quality detection / control timing can be considered variously, such as when the power is turned on, every certain number of output sheets, every certain period of time, or forcibly performed by the user or serviceman, as in the first embodiment. Not limited. It may be configured to detect and control the image quality according to a command from the external management device SV.

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

4). Third Embodiment In the first embodiment, detection patterns on the image carrier such as the photoreceptor 61, the intermediate transfer belt 5, and the recording paper transport belt 69 are directly detected, but the detection pattern is transferred to the surface. A dedicated transfer roller may be installed between the image carrier and the sensor, and the detection pattern on the dedicated transfer roller may be detected by the sensor. An example of this is shown in FIG. It should be noted that the position immediately before transferring to the recording paper as described above instead of the above position, or the position immediately after transferring to the recording paper conveying member instead of the recording paper, immediately before transferring from the photosensitive member 61 to the transfer target side. It may be a position.

  FIG. 31 is a diagram showing a schematic configuration of a sensor unit 100c according to the third 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. 31 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. 32 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 reflected light 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 may be 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.

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

As described above, according to the first to third embodiments, the following effects can be obtained.
(1) Since the state history can be created, the image forming apparatus can be managed based on the image quality of the actually created pattern.

(2) Since the state history is created based on the control parameters and the state quantity of the image forming apparatus at the time of detection / control, when an image quality abnormality occurs, it is easy to identify an abnormal part related to the image quality abnormality. Can be done.

(3) Since the status history is created by the external management device, it is not necessary to provide a large-scale recording unit or control unit in each image forming apparatus. As a result, the cost of the image forming apparatus can be reduced.

(4) Since the external management apparatus can manage the status histories of a plurality of image forming apparatuses, the image quality of each image forming apparatus can be efficiently managed as a system.

(5) In the case of an image forming apparatus that directly transfers a toner image on a photoreceptor onto a recording sheet, an image on an actual recording sheet is detected by detecting a detection pattern at a position after development and before transfer. It is possible to detect a close image. If the state history is created based on the detection result, the image quality of the image close to the actual image on the recording paper can be managed.

(6) By detecting the detection pattern at a position immediately before the toner image is transferred to the recording paper, it is possible to detect an image close to the actual image on the recording paper. Since the state history is created based on the detection result, the image quality of the image close to the actual image on the recording paper can be managed.

(7) It is possible to detect an image equivalent to an image on an actual recording sheet by detecting the detection pattern at a position immediately after being transferred to the recording sheet conveying member instead of the recording sheet. If the state history is created based on the detection result, the image quality of the image close to the actual image on the recording paper can be managed.

(8) By installing a dedicated transfer roller for pattern detection and detecting the pattern on the dedicated transfer roller, the influence of the surface optical characteristic difference between the photoconductor and intermediate transfer body depending on the model, and the photoconductor and intermediate transfer body It is possible to detect a pattern that is not affected by scratches or dirt due to deterioration over time. Further, by matching the surface optical characteristics of the roller with the optical system of the detection means, more accurate detection can be performed. Further, since the state history is created from the detection result on the dedicated transfer roller, it becomes possible to manage image quality with higher accuracy.

(9) By setting the position of the dedicated transfer roller immediately before the toner image is transferred to the recording paper or immediately after the toner image is transferred to the recording paper conveying member (instead of the recording paper), An image equivalent to the image can be transferred onto a dedicated transfer roller. Therefore, the image detected by the detection unit can be substantially the same as the image on the recording paper. Since the state history is created based on the detection result, the image quality of the image close to the actual image on the recording paper can be managed.

(10) Graininess, sharpness, and gradation are important factors that determine image quality. Since the state history is created based on the result of detection / control of the graininess, sharpness, and gradation, the image quality can be managed with high accuracy.

(11) The development bias, the charging grid bias, and the LD power determine the development potential. When the development potential fluctuates due to deterioration over time, or when the required development potential value changes, the desired development potential can be obtained by controlling the development bias, charging grid bias, and LD power. Sharpness and gradation can be improved.

(12) When the developer pumping amount changes due to deterioration over time and the developer amount supplied to the development nip changes, the developer pumping amount is adjusted by adjusting the developing sleeve linear speed, Sharpness can be improved.

(13) The temperature and humidity in the image forming apparatus greatly affect the image quality. By detecting the temperature and managing it with the state history, it is possible to grasp the influence of the temperature when an image quality abnormality occurs.

(14) When the toner density fluctuates greatly, the toner charge amount fluctuates accordingly. When the charge amount varies, the appropriate values of the developing bias and the transfer bias do not match, which greatly affects the image quality. By detecting the toner density and managing it with the status history, it is possible to grasp the influence of the toner density when an image quality abnormality occurs.

(15) When the toner charge amount fluctuates due to developer deterioration or the like, the toner adhesion amount on the image carrier fluctuates accordingly. The fluctuation of the toner adhesion amount greatly affects the image quality. By detecting the toner adhesion amount and managing it with the state history, it is possible to grasp the influence of the toner adhesion amount when an image quality abnormality occurs.

(16) The charging characteristics of the photoconductor vary due to deterioration of the photoconductor over time, such as scratches, dirt on the surface of the photoconductor, filming, changes in the film thickness of the photoconductor, and changes in the optical characteristics of the photoconductor. The fluctuation of the charging characteristic can be detected by the image portion / non-image portion potential of the photoreceptor. By detecting the image portion / non-image portion potential of the photoconductor and managing it based on the state history, it becomes possible to grasp the influence of deterioration of the photoconductor over time when an image quality abnormality occurs.

(17) The fluctuation of the transfer bias greatly affects the image quality due to discharge or the like during transfer. By detecting the transfer bias and managing it based on the state history, it is possible to grasp the influence of the transfer bias when an image quality abnormality occurs.

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 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. 2 is a block diagram illustrating a control configuration of the image forming apparatus. FIG. It is a flowchart which shows the control procedure in 1st Example. It is a figure for demonstrating the influence on the image quality of deterioration of a developer. It is a figure for demonstrating the influence on the adhesion amount of deterioration of a developer. It is a figure which shows the discharge of the temporal change of a granularity and development potential. It is a figure which shows the state of a time-dependent fluctuation | variation of a granularity and a transfer bias. It is a figure which shows the state of a time-dependent fluctuation | variation of a to-be-imaged part potential. It is a flowchart which shows the control procedure in 2nd Example. It is a schematic block diagram of the sensor unit which detects the pattern for a detection transferred on the exclusive transfer roller which concerns on 3rd Example with a sensor head. It is a figure which shows the relationship between a glossy surface and a diffusion 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 Photosensitive Member 62 Charging Unit 63 Developing Unit 69 Recording Paper Conveying Belt 100a Sensor 100c Sensor Unit 101 Light Emitting Element 102, 104, 106 Lens 103 Light Receiving Element 108 Sensor Head 109a Dedicated Transfer roller 130 arithmetic circuit 130a arithmetic unit 150 image carrier CON control circuit

Claims (6)

A pattern forming unit that forms an image quality detection pattern on the image carrier; and a detection unit that detects the amount of light reflected from the pattern formed on the image carrier by the pattern forming unit in a minute region. In an image forming apparatus comprising means for evaluating image quality based on the detection output of the means,
A state that detects at least one of the in-machine temperature, the in-machine humidity, the toner density in the developing device, the toner adhesion amount on the image carrier, the potential of the image / non-image part on the photoconductor, and the transfer bias. A quantity detection means;
A computing means for computing image characteristics including at least one of graininess, sharpness and gradation from the detection result of the detecting means;
Deterioration determining means for determining deterioration of the image characteristics based on a calculation result of the calculating means;
Control means for setting a control parameter including at least one of a developing bias, a charging grit bias, an LD power, and a developing sleeve linear velocity based on the calculation result of the calculating means, and causing image formation to be performed based on the set control parameter When,
A state history creating means for creating a state history from the state quantity detected by the state quantity detecting means, the calculation result of the image characteristic calculated by the calculating means, and the control parameter set by the control means;
A specifying unit for specifying a location where an abnormality has occurred in the image forming apparatus from the detected state quantity, the calculated calculation result, the set control parameter, and the created state history;
The control means sets the control parameter when it is determined by the deterioration determination means that the image characteristic is deteriorated, and when it is determined that the deterioration can be recovered by changing the control parameter. Change, and again form the image quality detection pattern to determine the deterioration of the image characteristics,
The state history creating means creates the state history when the deterioration determining means determines that the image characteristics are not deteriorated,
In the case where it is determined that the image characteristic is deteriorated by the deterioration determining means and the deterioration is determined to be unrecoverable by the change of the control parameter, the specifying means has an abnormality. An image forming apparatus characterized by identifying the location.   The image forming apparatus according to claim 1, further comprising storage means for storing and storing the generated state history.   3. The image forming apparatus according to claim 1, wherein the detecting unit is provided at a final stage of an image forming process immediately before fixing an image. In an image quality management method for determining an image quality state from an image quality detection pattern formed on an image carrier of an image forming apparatus and managing the image quality based on the determination result,
Detecting a state quantity including at least one of in-machine temperature, in-machine humidity, toner density in the developing device, toner adhesion amount on the image bearing member, potential of image area / non-image area on the photoreceptor, and transfer bias When,
Calculating image characteristics including at least one of graininess, sharpness, and gradation based on the detection result of the image quality detection pattern;
Determining a deterioration state of image quality from a calculation result of the calculation;
If it is determined that the image quality is deteriorated in the step of determining the deterioration state, the image quality is recovered by changing a control parameter including at least one of a developing bias, a charging grit bias, an LD power, and a developing sleeve linear velocity. Determining whether it is possible;
If it is determined that the recovery is possible in the step of determining whether or not the recovery is possible, the control parameter is changed, the image quality detection pattern is formed again, and the deterioration state of the image quality is determined again.
If the image quality has not deteriorated in the determination, creating a state amount history from the calculation result of the state amount, the control parameter, and the image quality characteristic;
If it is determined that recovery is not possible in the step of determining whether or not recovery is possible, the detected state quantity, the calculated calculation result and the set control parameter, and the created state history Identifying a non-recoverable part based on,
An image quality management method comprising: In a computer program for controlling the image quality of an image to be loaded and imaged in an image forming apparatus,
Detecting a state quantity including at least one of in-machine temperature, in-machine humidity, toner density in the developing device, toner adhesion amount on the image carrier, potential of image / non-image part on the photoreceptor, and transfer bias 1 procedure,
A second procedure for detecting a control parameter including at least one of a developing bias, a charging grit bias, an LD power, and a developing sleeve linear velocity;
A third procedure for forming a detection pattern;
A fourth procedure for detecting the amount of reflected light from the detection pattern formed in the third procedure;
A fifth procedure for calculating image characteristics including at least one of graininess, sharpness, and gradation from the amount of reflected light detected in the fourth procedure;
A sixth procedure for determining deterioration in image quality based on the image characteristics calculated in the fifth procedure;
If it is determined that the image quality is deteriorated in the determination in the sixth procedure, the image quality is recovered by changing a control parameter including at least one of a developing bias, a charging grit bias, an LD power, and a developing sleeve linear velocity. A seventh procedure for determining whether it is possible;
If it is determined in the seventh procedure that recovery is possible, the control parameter is changed to form an image quality detection pattern again, and the image quality degradation state is determined again. 8 steps,
A ninth procedure for creating a state history from the calculation result of the state quantity, the control parameter, and the image quality characteristic when the image quality has not deteriorated in the determination in the sixth procedure;
When it is determined that recovery is not possible in the determination of whether or not recovery is possible in the seventh procedure, the detected state quantity, the calculated calculation result, the set control parameter, and the created A tenth procedure for identifying unrecoverable locations based on the state history;
A computer program comprising: 6. A computer program according to claim 5 , wherein said computer program is read and recorded so as to be executable.

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