JP2005300757A - Image forming apparatus and detecting method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately detect toner patches without being adversely effected by variations in the arrival time of a transfer material due to its contraction. <P>SOLUTION: Image patterns for the adjustment of image formation characteristics are formed on a transfer material 1 when images are formed by an electrophotographic system. When the plurality of image patterns formed are detected, a control part 30 detects the conveyed state of the transfer material on a predetermined conveyance path. Based upon the conveyed state detected, the percentage of the contraction of the transfer material is calculated. A reference image formed on the transfer material is detected. Based upon the contraction percentages calculated, the timings of detecting the plurality of image patterns from the reference image are determined. A color sensor 26 is controlled so that the plurality of image patterns are detected with the respective detection timings thus determined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an improvement in toner image density, gradation, and color in an image forming apparatus.

  In recent years, color image forming apparatuses such as color printers and color copying machines that form images by electrophotography have been demanded to improve the quality of output images. However, in the color image forming apparatus, when each part of the apparatus fluctuates due to environmental changes or long-term use, the density of the obtained image also fluctuates. In particular, in the case of an electrophotographic color image forming apparatus, even a slight environmental fluctuation may cause a density fluctuation, which may cause the color balance to be lost. Therefore, it is necessary to always maintain a constant density-gradation characteristic.

  Therefore, the toner of each color is provided with gradation correction means such as a look-up table (LUT) for converting several kinds of exposure conditions and development biases depending on the temperature and humidity, and a look-up table (LUT) for converting image data. An image forming process condition and an optimum value for gradation correction are selected based on the measured temperature and humidity.

  In addition, even if a change occurs in each part of the apparatus, a toner patch for density detection is formed on the intermediate transfer member or the photosensitive drum with each color toner so that a constant density-gradation characteristic can be obtained. The density of the unfixed toner patch is detected by a density detection sensor for unfixed toner (hereinafter referred to as “density sensor”), and the density control is performed by feeding back the process results such as exposure amount and development bias from the detection result. It is configured to obtain a stable image.

  Density control using this density sensor detects toner patches formed on an intermediate transfer belt, photosensitive drum, etc., and changes in the color balance of the image due to subsequent transfer to the transfer material and fixing. Has no control.

  Therefore, a chromaticity detection sensor (hereinafter referred to as “color sensor”) that detects the density of a single-color toner patch on a transfer material or the chromaticity of a full-color image after transfer and fixing, and the exposure amount, process condition, There has also been proposed a color image forming apparatus that adjusts the density or chromaticity of an image by feeding back a lookup table (LUT) or the like (see, for example, Patent Document 1).

  FIG. 13 is a diagram illustrating an example of a color sensor that detects the chromaticity of a color image. In FIG. 13, 132 is an LED serving as a light source, and illuminates a color image with a constant amount of light. Reference numeral 133 denotes a color image as a detection target formed on the transfer material 1. A light receiving unit 131 such as a photodiode receives reflected light 134 from a color image.

A color measuring device using such a photodiode 131 can form a color measuring device. Specifically, as LEDs, for example, three LEDs having different emission spectra such as R (red), G (green), and B (blue) are provided, and the LEDs are caused to emit light independently for the color image to be measured. By obtaining the output of the sensor corresponding to each LED, it is possible to obtain each color component of R, G, B included in the reflected light from the color image, and calculate chromaticity such as L * a * b * and XYZ can do.
JP 2003-84532 A

  However, the conventional control method has the following problems.

  In order to obtain a stable image, toner patches (color images) of various chromaticities are formed on the transfer material, the colors are actually measured with a color sensor, and the difference from the desired chromaticity is obtained. Need to provide feedback on process conditions.

  In order to measure the toner patch with a color sensor with high accuracy, it is necessary to detect the toner patch on the transfer material to be measured at an accurate timing.

  However, due to the shrinkage of the transfer material that occurs when the transfer material passes through the fixing device, the time at which the toner patch arrives within the detection area of the sensor varies, and the toner patch is detected at a fixed timing. It becomes difficult.

  To solve the above problems, there is a method of widening the detection timing margin by increasing the size of the toner patch in the transport direction, but there is a problem that wasteful toner increases and the economy is reduced. Occur.

  Furthermore, since the number of patches that can be formed on one transfer material is also reduced, there is a problem that the number of transfer materials that form patches increases in order to provide feedback to various image forming process conditions. .

  SUMMARY An advantage of some aspects of the invention is to detect a toner patch with high accuracy without being affected by variations in arrival time due to shrinkage of a transfer material.

  The present invention provides detection means for forming an image pattern on a transfer material for adjusting image forming characteristics when an image is formed by an electrophotographic method, and detecting a plurality of image patterns formed on the transfer material. An image forming apparatus having a detection unit that detects a conveyance state of a transfer material on a predetermined conveyance path, a unit that calculates a shrinkage rate of the transfer material based on the detected conveyance state, A reference image formed as a reference is detected by the detection means, a means for determining a timing for detecting the plurality of image patterns from the reference image based on the calculated contraction rate, and the detection timing at the determined detection timing. Control means for controlling the detection means so as to detect a plurality of image patterns.

  In addition, the present invention provides a detection method in which an image pattern for adjusting image formation characteristics when an image is formed by an electrophotographic method is formed on a transfer material, and a plurality of image patterns formed on the transfer material are detected. An image forming apparatus including a detecting unit that detects a conveyance state of the transfer material on a predetermined conveyance path, a unit that obtains a shrinkage rate of the transfer material based on the detected conveyance state, and the detection unit. A storage unit that detects the plurality of image patterns and stores output values of the detected image patterns, and an output value corresponding to the detection timing of each image pattern determined based on the contraction rate is extracted from the storage unit. And means for carrying out the above.

  Furthermore, the present invention provides a detection method in which an image pattern for adjusting image forming characteristics when an image is formed by an electrophotographic method is formed on a transfer material, and a plurality of image patterns formed on the transfer material are detected. An image forming apparatus detecting method comprising: a step of detecting a transfer state of a transfer material on a predetermined transfer path; a step of calculating a shrinkage rate of the transfer material based on the detected transfer state; A step of detecting a reference image formed on the transfer material as a reference by the detecting means and determining a timing for detecting the plurality of image patterns from the reference image based on the calculated contraction rate; And a step of controlling the detection means so as to detect the plurality of image patterns at a detection timing.

  Furthermore, the present invention provides a detection method in which an image pattern for adjusting image forming characteristics when an image is formed by an electrophotographic method is formed on a transfer material, and a plurality of image patterns formed on the transfer material are detected. An image forming apparatus detection method comprising: a step of detecting a transfer material conveyance state on a predetermined conveyance path; a step of obtaining a shrinkage rate of the transfer material based on the detected conveyance state; and the detection Detecting a plurality of image patterns by means, storing output values of the detected image patterns in storage means, and output values corresponding to detection timings of the image patterns determined based on the shrinkage rate And extracting from the storage means.

  According to the present invention, it is possible to detect a toner patch with high accuracy without being affected by variations in arrival time due to shrinkage of a transfer material.

  The best mode for carrying out the invention will be described below in detail with reference to the drawings. In this embodiment, a color laser beam printer is described as an example of a color image forming apparatus. However, the present invention is not limited thereto, and can be applied to, for example, an electrophotographic full-color digital copying machine.

  As a first exemplary embodiment, a method for calculating a contraction rate of a transfer material from an actual length of the transfer material detected by a paper discharge sensor and correcting a detection timing of a chromaticity detection toner patch based on the contraction rate will be described. To do.

  FIG. 1 is a side sectional view showing the structure of the color laser beam printer according to the first embodiment. In the color laser beam printer, for each color of yellow (Y), magenta (M), cyan (C), and black (K), each image forming unit forms an electrostatic latent image by exposure based on image data. The electrostatic latent image is developed to form a visible image, and then the color visible image is transferred and fixed to a transfer material as a recording medium.

  The image forming unit includes photosensitive drums (5Y, 5M, 5C, and 5K), chargers (7Y, 7M, 7C, and 7K) and laser scanners (10Y, 10M, 10C, and 10K) arranged in parallel for the number of development colors. ), Developing device (8Y, 8M, 8C, 8K), toner cartridge (11Y, 11M, 11C, 11K), intermediate transfer belt 12, primary transfer roller (6Y, 6M, 6C, 6K), secondary transfer roller 9, A sheet feeding / conveying unit, a fixing device 13 and the like are included.

  When the printing operation is started, the photosensitive drums (5Y, 5M, 5C, 5K) configured by applying an organic optical conductive layer to the outer periphery of the aluminum cylinder are rotated counterclockwise by a drive motor (not shown). The charging sleeves (7YS, 7MS, 7CS, 7KS) of the chargers (7Y, 7M, 7C, 7K) primarily charge the photosensitive drums (5Y, 5M, 5C, 5K). Next, the laser scanner (10Y, 10M, 10C, 10K) selectively performs exposure based on the input image data, and the electrostatic latent image is sequentially formed on the surface of the photosensitive drum (5Y, 5M, 5C, 5K). Form. The developing sleeve (8YS, 8MS, 8CS, 8CK) of the developing unit (8Y, 8M, 8C, 8K) visualizes the electrostatic latent image on the surface of the photosensitive drum (5Y, 5M, 5C, 5K).

  On the other hand, the intermediate transfer belt 12, which is an endless belt adjusted by the driving roller 18a and the driven rollers (18b, 18c), rotates clockwise while contacting the photosensitive drums (5Y, 5M, 5C, 5K). The toner images are sequentially primary transferred onto the surface of the belt 12 by transfer rollers (6Y, 6M, 6C, 6K).

  In addition, a transfer material 1 is accommodated in a paper feed cassette 2 or a paper feed tray 3 as a paper feed unit, and the transfer material 1 is transported on a transport path 25 including a paper feed roller 4 and a transport roller 24. As a result, the position reaches the pre-registration sensor 19 position. Then, the transfer material 1 is further conveyed by a certain amount, reaches the registration roller 23, forms a loop, and stands by.

  The transfer material 1 that has been waiting is transported again, and the secondary transfer roller 9 comes into contact with the intermediate transfer belt 12 to nipping and transporting the transfer material 1, so that the color visible color transferred onto the intermediate transfer belt 12 is transferred. The image is secondarily transferred at once. The secondary transfer roller 9 is in contact with the intermediate transfer belt 12 as indicated by the solid line during the secondary transfer, but is separated from the position indicated by the dotted line after the secondary transfer.

  Next, the transfer material 1 is conveyed to a fixing device 13, and the toner image on the transfer material 1 is fixed by a fixing roller 14 that heats the toner and a pressure roller 15 that presses the transfer material 1 against the fixing roller 14. Is done. Note that the fixing roller 14 and the pressure roller 15 are formed in a hollow shape, and heaters 16 and 17 are incorporated therein, respectively.

  Then, the transfer material 1 after toner fixing is discharged to a discharge tray (not shown), and the image forming operation is finished.

  The cleaner container 21 cleans the intermediate transfer belt 12 with a built-in cleaning blade, and stores toner remaining on the intermediate transfer belt 12 without being secondarily transferred as waste toner.

  Here, the color sensor 26 is disposed at an intermediate position between the fixing device 13 and the paper discharge tray, reads reflected light from the toner patch fixed on the transfer material 1 by this apparatus, and outputs values from the RGB sensors. Is output to the control unit 30. The control unit 30 includes an arithmetic unit such as a CPU and an MPU, a ROM in which a program of the arithmetic unit is stored, a RAM 27 in which a work area used when executing control, various tables, and the like are defined. Based on the value, feedback is given to a gradation correction unit such as a look-up table to control to give a desired color on the transfer material 1.

  FIG. 2 is a diagram illustrating a pattern of a chromaticity adjustment toner patch according to the first exemplary embodiment. In FIG. 2, reference numeral 201 denotes a position detection toner patch, which is a reference for timing for detecting the pattern of the chromaticity detection toner patch. Reference numerals 202 to 205 denote chromaticity detection toner patch patterns, which are chromaticity detection toner patch patterns in which the chromaticity is changed.

  In order to control the color stability of the color image forming apparatus, it is desirable to detect more chromaticity detection toner patch patterns and feed them back to the image forming conditions. The number of degree detection toner patch patterns is four.

  Here, the configuration and operation of the paper discharge sensor 20 that detects the actual length in the transport direction of the transfer material 1 that has undergone the fixing process will be described. The detection of the actual length of the transfer material 1 is referred to as “actual length detection”.

  FIG. 3 is a diagram illustrating a configuration of the paper discharge sensor 20. As shown in FIG. 3, as the transfer material 1 passes, the flag 301 falls in the direction indicated by the dotted line, so that the photo interrupter 302 reacts and a predetermined output is obtained.

  FIG. 4 is a diagram illustrating the output of the photo interrupter when the transfer material 1 actually passes. Here, the actual length of the transfer material 1 is detected by the control unit 30 measuring the time Tk when the output signal from the photo interrupter 302 shown in FIG. 4 crosses the threshold Th using a timer (not shown). .

  The actual length detection of the transfer material 1 is always performed by the control unit 30 during normal image formation, and the detected actual length Tk is stored in the RAM 27 of the control unit 30. The stored actual length Tk of the transfer material 1 is used to correct the detection timing in the pattern detection sequence of the chromaticity adjustment toner patch of the first embodiment. The method for correcting the pattern detection timing of the toner patch for chromaticity adjustment is as follows.

  First, when the transfer material 1 is not contracted by the fixing process, that is, an ideal (standard value of the transfer material 1) transit time is set as an ideal length Tr and stored in the RAM 27 in advance. Next, the shrinkage rate R (= Tk / Tr) of the transfer material 1 is calculated from the actual length Tk with respect to the ideal length Tr, and the shrinkage rate R is stored and held in the RAM 27.

  Accordingly, the pattern detection timing of the chromaticity adjustment toner patch can be obtained by multiplying the detection start timing from the position detection toner patch 201 as a reference of the predetermined detection timing by the contraction rate R.

  Next, the pattern detection process of the chromaticity adjustment toner patch will be described with reference to FIG. This process is a process executed by an arithmetic unit such as a CPU or MPU of the control unit 30.

  FIG. 5 is a flowchart illustrating the pattern detection process according to the first embodiment. When the toner patch pattern for chromaticity adjustment is transferred and fixed onto the transfer material 1 and conveyed to the position of the color sensor 26, the control unit 30 includes the RGB output signals incident on the light receiving unit 131 of the color sensor 26. Then, monitoring of an arbitrary output signal is started (S501). Then, as shown in FIG. 6, the time when the output value of the output signal from the color sensor 26 first exceeds a predetermined threshold value is stored as Tk11 (S502, S503), and the time when the output signal value falls below the threshold value for the first time after Tk11. Is stored as Tk12 (S504, S505).

  Using these Tk11 and Tk12, the center position of the position detection toner patch 201, that is, the detection start timing Tk1 is calculated from the following equation (1) (S506).

Tk1 = (Tk11 + Tk12) / 2 (1)
As shown in FIG. 6, the above-mentioned time is for obtaining the detection start timing Tk1 of the position detection toner patch 201, and may not be an accurate time. A timer or the like (not shown) may be used. For example, a timer may be started at the start of monitoring, timer values may be stored as the above-described Tk11 and Tk12, and the timer value may be calculated as the detection start timing Tk1.

  Next, the control unit 30 reads the shrinkage rate R stored and held in the RAM 27 (S507), and calculates the detection timings of the chromaticity detection toner patch patterns 202 to 205. That is, by multiplying the predetermined ideal detection timings Tk202, Tk203, Tk204, and Tk205 by the contraction rate R with reference to Tk1, as shown in FIG. 7, the chromaticity detection toner patch patterns 202˜ The detection timing 205 is calculated (S508).

  Then, the control unit 30 detects each toner patch at a timing obtained by multiplying the ideal detection timings Tk202, Tk203, Tk204, and Tk205 by the shrinkage rate R, and obtains RGB output values (S509).

  As described above, according to the first embodiment, the contraction rate in the conveyance direction of the transfer material 1 is obtained by an optical sensor such as a paper discharge sensor, and the detection timing of the chromaticity detection toner patch is calculated based on the contraction rate. Thus, it is possible to detect the chromaticity detection toner patch at an optimal timing without being affected by the shrinkage of the transfer material 1 that has undergone the fixing process.

  In the first embodiment, it is also possible to store data together with their attributes in the RAM 27 for different paper types and paper sizes. When performing chromaticity detection, it is also possible to use data that matches the attributes of the paper type and paper size used in the detection.

  Next, as Example 2, the actual length of the transfer material 1 before and after passing through the fixing process is detected by an optical sensor, and the detection timing of the chromaticity detection toner patch is calculated based on the shrinkage rate of the transfer material 1 calculated from the result. A method for calculating the value will be described.

  The configuration of the image forming apparatus is the same as that in FIG. 1 described in the first embodiment, and a description thereof is omitted. Further, the chromaticity adjustment toner patch pattern of the second embodiment uses the same pattern as that of FIG. 2 of the first embodiment, and the actual length detection of the transfer material 1 after the fixing process is also detected by the method described in the first embodiment. To do.

  That is, the second embodiment is characterized in that the actual length of the transfer material 1 is detected even before the fixing process. Specifically, the control unit 30 detects the actual length of the transfer material 1 before the fixing process by using the transfer material presence / absence detection sensor 28 shown in FIG. The configuration and operation of the transfer material presence / absence detection sensor 28 are the same as those of the paper discharge sensor 20 shown in FIGS.

  Here, the actual length detection result of the transfer material 1 before the fixing process is Tpre, and the actual length detection result of the transfer material 1 after the fixing process is Tk. Based on these results, the shrinkage ratio R ′ (= Tk / Tpre) of the transfer material is calculated and stored in the RAM 27 of the control unit 30.

  Next, the pattern detection processing of the chromaticity adjustment toner patch described above will be described with reference to FIG. This process is also a process executed by an arithmetic unit such as the CPU and MPU of the control unit 30 as in the first embodiment.

  FIG. 8 is a flowchart illustrating pattern detection processing according to the second embodiment. When the pattern of the chromaticity adjustment toner patch is transferred and fixed onto the transfer material and conveyed to the position of the color sensor 26, the control unit 30 includes the RGB output signals incident on the light receiving unit 131 of the color sensor 26. Then, monitoring of an arbitrary output signal is started (S801). Then, as shown in FIG. 6, the time when the output value of the output signal from the color sensor 26 first exceeds a predetermined threshold value is stored as Tk11 (S802, S803), and the time when the output signal value falls below the threshold value for the first time after Tk11. Is stored as Tk12 (S804, S805).

  Using these Tk11 and Tk12, the center position of the position detection toner patch 201, that is, the detection start timing Tk1 is calculated from the following equation (2) (S806).

Tk1 = (Tk11 + Tk12) / 2 (2)
Next, the control unit 30 reads the shrinkage rate R ′ stored and held in the RAM 27 (S807), and calculates the detection timing of the chromaticity detection toner patch patterns 202 to 205. That is, by multiplying the predetermined ideal detection timings Tk202, Tk203, Tk204, and Tk205 by the contraction rate R ′ with reference to Tk1, as shown in FIG. 7, the chromaticity detection toner patch pattern 202 is obtained. The detection timing of ~ 205 is calculated (S808).

  Then, the control unit 30 detects each toner patch at a timing obtained by multiplying the ideal detection timings Tk202, Tk203, Tk204, and Tk205 by the shrinkage rate R ', and obtains an RGB output value (S809).

  As described above, according to the second embodiment, the shrinkage rate in the transfer material fixing process is obtained from the actual length of the transfer material 1 before and after the fixing process, and the chromaticity detection toner patch is obtained based on the shrinkage rate. The optimum detection timing can be calculated, and it is possible to cope with a case where a transfer material having a size other than the standard is used.

  Next, as Example 3, the actual length of the transfer material 1 after the fixing process having the chromaticity adjusting toner patch is detected, and the output value of the toner patch is detected from the detection data of the output signal based on the detection result. A method for extracting optimum data will be described.

  FIG. 9 is a diagram illustrating a chromaticity adjusting toner patch pattern according to the third exemplary embodiment. In the third embodiment, the number of toner patch patterns is four in order to simplify the description.

  Next, the pattern detection process of the chromaticity adjustment toner patch will be described with reference to FIG. This process is also a process executed by an arithmetic unit such as the CPU and MPU of the control unit 30 as in the first and second embodiments.

  FIG. 10 is a flowchart illustrating pattern detection processing according to the third embodiment. First, the control unit 30 calculates the passage time Tk when the transfer material 1 to which the patterns 901 to 904 shown in FIG. 9 are transferred and fixed passes through the paper discharge sensor 20 as in FIG. 4 (S1001). Then, the passage time Tk is stored and held in the RAM 27 (S1002).

  Next, when the transfer material 1 is conveyed to the position of the color sensor 26, the control unit 30 starts monitoring the output signal incident on the light receiving unit 131 (S1003). Then, as shown in FIG. 11, the time when an arbitrary output value of RGB first exceeds the threshold value is stored as Tk1 (S1004, S1005).

  Next, using this Tk1 as a reference (0 ms), the chromaticity detection toner patch patterns 901 to 904 are detected at a fixed timing (in the third embodiment, 1 msec interval), and the RGB output values and the detection time are detected. Are sequentially stored in the output value table shown in FIG. 12 (S1006). Simultaneously with this processing, the output value is compared with the threshold value (S1007), the time when the output value falls below the threshold value is stored as Tk2, and the storage in the output value table is terminated (S1008).

  Thereafter, the shrinkage rate R ″ of the transfer material 1 is calculated from the actual length Tr of the ideal transfer material determined in advance and the actual length Tk of the transfer material detected in steps S1001 and S1002, as in the first embodiment described above ( S1009) Next, each detection timing is calculated by multiplying the predetermined ideal patch detection timing by the contraction rate R ″ (S1010), and the time of the output value table is searched from each detection timing. The RGB output values of time are extracted as output values of the chromaticity detection toner patch patterns 901 to 904 (S1011).

  Here, the calculation of the output value of one toner patch pattern is obtained from the average value of a plurality of sampling data. Optimum by extracting the data required for calculating the average value of each chromaticity detection toner patch pattern from the output value table in which the data is stored, and then calculating the average value. Patch data.

  For example, when the process speed is 100 mm / sec and the pattern width in the transfer material conveyance direction of the chromaticity detection toner patch pattern is 10 mm, the data extraction areas of the predetermined chromaticity detection toner patch patterns 901 to 904 are illustrated in FIG. As in the conventional method column of the output value table shown in FIG.

  Here, when the shrinkage ratio R ″ of the transfer material 1 is 0.99, that is, when the transfer material 1 shrinks by 1%, the data extraction region of the corrected chromaticity detection toner patch patterns 901 to 904 is as shown in FIG. As in the corrected column data shown in FIG. 12, the extraction region is corrected so as to be narrowed by 1% and extracted.

  As described above, according to the third embodiment, it is possible to avoid a detection error due to shrinkage of the transfer material and to detect an accurate output value of the toner patch.

  In the third embodiment, the method of obtaining the sampling start timing and the sampling time of the chromaticity detection toner patch by detecting the front and rear ends of the chromaticity detection toner patch pattern has been described. As described above, the position detection toner patch 201 may be formed at an arbitrary position and measured.

  As described above, according to the embodiment, the shrinkage rate of the transfer material is obtained from the actual length of the transfer material detected by the optical sensor, and the influence of the shrinkage of the transfer material is corrected by correcting the detection timing of the toner patch. Without being received, it is possible to accurately know the timing at which the toner patch reaches the detection area of the color sensor.

  Therefore, it is not necessary to provide a margin for the size of the toner patch, and more patches can be provided for a limited time and with a limited length of the transfer material, improving convenience and color stability. The amount of information that can be used for control can be increased.

  Even if the present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), it is applied to an apparatus (for example, a copier, a facsimile machine, etc.) composed of a single device. It may be applied.

  Another object of the present invention is to supply a recording medium in which a program code of software realizing the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (CPU or MPU) of the system or apparatus stores the recording medium in the recording medium. Needless to say, this can also be achieved by reading and executing the programmed program code.

  In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiment, and the recording medium storing the program code constitutes the present invention.

  As a recording medium for supplying the program code, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like is used. be able to.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Further, after the program code read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

1 is a side sectional view showing the structure of a color laser beam printer in Embodiment 1. FIG. 3 is a diagram illustrating a pattern of a chromaticity adjustment toner patch in Embodiment 1. FIG. 2 is a diagram illustrating a configuration of a paper discharge sensor 20. FIG. It is a figure showing the output of the photo interrupter when the transfer material 1 actually passes. 3 is a flowchart illustrating pattern detection processing according to the first exemplary embodiment. It is a figure which shows the output signal of the toner patch detected by a color sensor. FIG. 6 is a diagram for explaining detection timing of a chromaticity detection toner patch. 10 is a flowchart illustrating pattern detection processing according to the second embodiment. 6 is a diagram illustrating a pattern of a chromaticity adjusting toner patch in Embodiment 3. FIG. 12 is a flowchart illustrating pattern detection processing according to the third embodiment. FIG. 4 is a diagram illustrating an output signal of a chromaticity adjustment toner patch detected by a color sensor. It is a figure which shows the structure of the output value table in Example 3. FIG. It is a figure which shows an example of the color sensor which detects the chromaticity of a color image.

Claims (9)

An image forming apparatus having an image pattern for adjusting image forming characteristics when an image is formed by an electrophotographic method on a transfer material, and detecting means for detecting a plurality of image patterns formed on the transfer material Because
Detecting means for detecting the transfer state of the transfer material on a predetermined transfer path;
Means for calculating a shrinkage rate of the transfer material based on the detected conveyance state;
Means for detecting a reference image formed as a reference on the transfer material by the detection means, and determining timing for detecting the plurality of image patterns from the reference image based on the calculated shrinkage rate;
An image forming apparatus comprising: a control unit that controls the detection unit so as to detect the plurality of image patterns at the determined detection timing. An image forming apparatus having an image pattern for adjusting image forming characteristics when an image is formed by an electrophotographic method on a transfer material, and detecting means for detecting a plurality of image patterns formed on the transfer material Because
Detecting means for detecting the transfer state of the transfer material on a predetermined transfer path;
Means for obtaining a shrinkage rate of the transfer material based on the detected conveyance state;
Storage means for detecting the plurality of image patterns by the detection means and storing output values of the detected image patterns;
An image forming apparatus comprising: an output value corresponding to a detection timing of each image pattern determined based on the shrinkage rate, from the storage unit.   The image forming apparatus according to claim 1, wherein the detection unit detects a conveyance state of the transfer material on a predetermined conveyance path after the transfer material passes through a fixing unit in image formation.   3. The image according to claim 1, wherein the detection unit detects a conveyance state of the transfer material on a predetermined conveyance path before and after the transfer material passes through the fixing unit in image formation. Forming equipment.   5. The apparatus according to claim 1, wherein at least one of density, gradation, and color of a toner image is adjusted based on a detection result of the detection unit. Image forming apparatus. An image forming apparatus having an image pattern for adjusting image forming characteristics when an image is formed by an electrophotographic method on a transfer material, and detecting means for detecting a plurality of image patterns formed on the transfer material Detection method,
Detecting the transfer state of the transfer material on a predetermined transfer path;
Calculating a shrinkage rate of the transfer material based on the detected conveyance state;
Detecting a reference image as a reference formed on the transfer material by the detection means, and determining timing for detecting the plurality of image patterns from the reference image based on the calculated shrinkage rate;
And a step of controlling the detection means so as to detect the plurality of image patterns at the determined detection timing. An image forming apparatus having an image pattern for adjusting image forming characteristics when an image is formed by an electrophotographic method on a transfer material, and detecting means for detecting a plurality of image patterns formed on the transfer material Detection method,
Detecting the transfer state of the transfer material on a predetermined transfer path;
Obtaining a shrinkage rate of the transfer material based on the detected conveyance state;
Detecting the plurality of image patterns by the detection means, and storing output values of the detected image patterns in a storage means;
And a step of extracting from the storage means an output value corresponding to the detection timing of each image pattern determined based on the shrinkage rate.   A program for causing a computer to execute the detection method for an image forming apparatus according to claim 6.   A computer-readable recording medium on which the program according to claim 8 is recorded.