JP2015060065A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that precisely performs calibration.SOLUTION: An image forming apparatus includes: image forming means including forming means for forming an unfixed image on a recording material, and fixing means for fixing the unfixed image formed on the recording material to the recording material according to set fixing conditions; measuring means for measuring the image fixed to the recording material by the fixing means; and control means for performing calibration according to a result of the measurement of the measuring means, where the control means performs calibration according to fixing conditions in predetermined standard settings.

Description

  The present invention relates to a calibration technique for an image forming apparatus.

  In an electrophotographic image forming apparatus, during continuous printing, for example, the toner charge retention amount may fluctuate, which may cause the image density to change. Further, the density of the output image also varies depending on the installation environment of the image forming apparatus and the characteristic variation of each part. For this reason, Patent Document 1 discloses that density calibration is performed by forming a pattern image and measuring the density of the formed pattern image. Patent Documents 2 and 3 disclose a configuration in which calibration is performed based on the amount of applied toner. Further, Patent Document 4 discloses a configuration in which adjustment is made so that an optimum fixing temperature is obtained for each type of recording material.

JP 04-268873 A JP 2007-272112 A JP 2010-286620 A JP 2005-338362 A

  For example, if the fixing temperature of the fixing device is changed, the detected density may be different even if the toner loading amount is the same. As described in Patent Document 2, the toner loading amount is adjusted to a specified toner loading amount. Can not be. Also, as in Patent Document 3, when newly registering a recording material to be used for calibration, an area where the density does not change even when the amount of applied toner changes at a predetermined fixing temperature is used. There is a decrease in calibration accuracy.

  The present invention provides an image forming apparatus that performs calibration with high accuracy.

  According to an aspect of the present invention, the image forming apparatus includes: a forming unit that forms an unfixed image on the recording material; and a fixing unit that fixes the unfixed image formed on the recording material to the recording material according to set fixing conditions. An image forming unit; a measuring unit that measures an image fixed on the recording material by the fixing unit; and a control unit that performs calibration based on a measurement result of the measuring unit. The control unit includes the calibration unit. The fixing condition is set to a predetermined standard when executing the operation.

  Calibration can be performed with high accuracy.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment. FIG. 3 is a control configuration diagram of the image forming apparatus according to the first embodiment. The block diagram of the color sensor by 1st embodiment. The flowchart of the calibration by 1st embodiment. FIG. 6 is a diagram illustrating a relationship between detected luminance and toner applied amount according to the first embodiment. Explanatory drawing of the maximum density control by 1st embodiment. The figure which shows the relationship between the glossiness and fixing conditions by 1st embodiment. Explanatory drawing of the relationship between the irregular reflection light quantity and toner by 1st embodiment. Explanatory drawing of the influence on the toner applied amount by the glossiness by 1st embodiment. The flowchart of the calibration by 1st embodiment. The flowchart of the calibration by 2nd embodiment.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In the following drawings, components that are not necessary for the description of the embodiments are omitted from the drawings. Moreover, each following embodiment is an illustration and does not limit the range of this invention to embodiment.

<First embodiment>
FIG. 1 is a cross-sectional view showing the structure of the image forming apparatus 100. The image forming apparatus 100 includes a housing 101. The casing 101 is provided with each mechanism for configuring the image forming engine unit and a control board storage unit 104. The control board storage unit 104 stores an engine control CPU 102 that controls each process for printing (for example, a paper feed process) and a printer controller 103 that performs image processing.

  As shown in FIG. 1, the image forming engine unit is provided with four stations 120, 121, 122, 123 corresponding to YMCK. Stations 120, 121, 122, and 123 are image forming units that form toner images by transferring toner, which is a color material, to a recording material. Here, YMCK is an abbreviation for yellow, magenta, cyan, and black. Each station is composed of almost common parts. The photosensitive drum 105 is a kind of image carrier, and is charged to a uniform surface potential by a primary charger 111. A latent image is formed on the photosensitive drum 105 by the laser light output from the laser 108. The developing device 112 develops the latent image using toner to form a toner image. The toner image (visible image) is primarily transferred onto the intermediate transfer member 106. The visible image formed on the intermediate transfer member 106 is secondarily transferred by the transfer roller 114 to the recording material 110 conveyed from the storage 113.

  The fixing processing mechanism of the present embodiment includes a first fixing device 150 and a second fixing device 160 that heat and press the toner image, which is an unfixed image transferred to the recording material 110, to fix the toner image on the recording material 110. ing. The first fixing device 150 includes a fixing roller 151 for applying heat to the recording material 110, a pressure belt 152 for pressing the recording material 110 against the fixing roller 151, and a first post-fixing sensor for detecting completion of fixing. 153. These rollers are hollow rollers and each have a heater inside. Further, these rollers are driven by a motor (not shown) to convey the recording material 110. The second fixing device 160 is arranged downstream of the first fixing device 150 in the conveyance direction of the recording material 110. The second fixing device 160 adds gloss to the toner image on the recording material 110 fixed by the first fixing device 150 or ensures the fixing property. Similar to the first fixing device 150, the second fixing device 160 also has a fixing roller 161, a pressure roller 162, and a second post-fixing sensor 163. Depending on the type of the recording material 110, it is not necessary to pass the second fixing device 160. In this case, the recording material 110 passes through the conveyance path 130 without going through the second fixing device 160 for the purpose of reducing energy consumption. The flapper 131 switches whether to guide the recording material 110 to the conveyance path 130 or to the second fixing device 160.

  The flapper 132 is a guide member that guides the recording material 110 to the discharge path 135 or guides the recording material 110 to the discharge path 139 to the outside. A reversing sensor 137 is provided in the discharge path 135. The leading end of the recording material 110 passes through the reversing sensor 137 and is conveyed to the reversing unit 136. When the reverse sensor 137 detects the trailing edge of the recording material 110, the conveyance direction of the recording material 110 is switched. The flapper 133 is a guide member that guides the recording material 110 to the conveyance path 138 for double-sided image formation or guides the recording material 110 to the discharge path 135. The switching flapper 134 is a guide member that guides the recording material 110 to the discharge path 139 to the outside. A number of transport rollers 140 are provided on transport paths such as the discharge path 135 and the discharge path 139.

  A color sensor 200 that detects a test pattern on the recording material 110 is disposed downstream of the second fixing device 160 in the conveyance direction of the recording material 110. The color sensor 200 functions as a measurement unit that measures the color of an image fixed on the recording material 110 downstream of the first fixing device 150 and the second fixing device 160 in the conveyance direction of the recording material 110. The color sensor 200 may be disposed in the discharge path 139. In response to an instruction from the operation panel 180, the printer controller 103 executes maximum density control, gradation control, and the like.

  FIG. 2 is a block diagram illustrating a control configuration of the image forming apparatus 100. The host computer 301 is a computer that transmits a print job to the image forming apparatus 100 via a wired or wireless communication line. The printer controller 103 controls the operation of the image forming apparatus 100 in cooperation with the engine control CPU 102. Each unit constituting the printer controller 103 is connected via a bus 319.

  The host I / F unit 302 is a communication unit that controls input / output with the host computer 301. The input / output buffer 303 stores control codes from the host I / F unit 302 and accumulates data from each communication unit. The printer controller CPU 313 is a main processor that controls the overall operation of the printer controller 103. A ROM 304 is a memory that stores a control program and control data for the printer controller CPU 313. Examples of functions realized by the printer controller CPU 313 executing this control program include an image information generation unit 305, a density condition determination unit 306, a gradation correction table generation unit 307, and a fixing temperature determination unit 308. The RAM 309 is a memory used as a work area for interpreting control codes and data, calculations necessary for printing, or processing print data. The RAM 309 is provided with a table storage unit 310 that stores various data determined or generated by the density condition determination unit 306 and the gradation correction table generation unit 307.

  The image information generation unit 305 generates various image objects (such as test patterns) according to the setting information received from the host computer 301. A RIP (Raster Image Processor) unit 314 is a processor that develops an image object into a bitmap image. The color processing unit 315 performs color conversion processing according to the color profile. The tone correction unit 316 performs monochrome tone correction using the tone correction table (γLUT) created by the tone correction table generation unit 307. The pseudo halftone processing unit 317 performs pseudo halftone processing such as a dither matrix and an error diffusion method on the image data. The engine I / F unit 318 is a communication unit that transfers image data to the engine control CPU 102. The engine control CPU 102 controls the four stations 120, 121, 122, 123 according to the image data.

  The operation panel 180 includes a display device and an input device, and inputs an instruction to execute printing and correction processing, and displays information to the operator. A panel I / F unit 311 connects the operation panel 180 and the printer controller 103.

  FIG. 3 is a configuration diagram of a color sensor 200 (measurement unit) that reads a test pattern formed on the recording material 110 and measures RGB values. Note that R, G, and B are abbreviations of red, green, and blue, respectively. The color sensor 200 includes a light emitting element 53 that outputs white light and a light receiving element 54 with an RGB on-chip filter. In the first embodiment, the light emitting element 53 is provided so that light is incident at an angle of 45 degrees with respect to the normal direction of the recording material 110 on which the test pattern after fixing is formed. In one embodiment, the light receiving element 54 is provided so as to receive irregularly reflected light reflected in the normal direction of the recording material 110 and measures the R, G, and B values of the irregularly reflected light. The configurations of the light-emitting element 53 and the light-receiving element 54 are not limited to those shown in FIG. 3. The configuration in which the light-receiving element 54 receives irregularly reflected light, for example, the incident angle is 0 degree and the reflection angle is 45 degrees. It may be a configuration. Moreover, it can also be comprised by the light emitting element which each light-emits three colors of RGB, and the light receiving element without a filter. The color sensor 200 outputs the luminance information of the test patterns for Y, M, C, and K to the printer controller 103 using the complementary color information from the measured RGB values. For K, G color information is used.

  Next, calibration executed by the printer controller CPU 313 (hereinafter simply referred to as CPU 313) will be described with reference to FIG. The calibration includes maximum density control and gradation control for matching the maximum density. When the execution of calibration is instructed, the CPU 313 obtains temperature / humidity information from a temperature / humidity sensor (not shown) in S10, calculates a specified environment classification, determines a charging potential in S11, and then determines the determined charging The developing bias is determined based on the potential. The developing bias is determined such that the difference from the determined charging potential is a specified amount.

  In S12, the CPU 313 executes maximum density control. First, the CPU 313 causes the engine control CPU 102 to form a test pattern for each color of YMCK using the charging potential and the developing bias determined in S11. Each color test pattern is formed by changing a plurality of exposure intensities, that is, the light level (power) applied to the photosensitive drum 105. The color sensor 200 measures the test patterns formed at different light levels for each color, and notifies the printer controller 103 of the luminance component of each color. The CPU 313 converts the detected brightness measured by the color sensor 200 into the applied toner amount at each light level based on the conversion information indicating the relationship between the detected brightness and the applied toner amount (color material amount) shown in FIG. Then, as shown in FIG. 6, the CPU 313 calculates a light level at which the applied toner amount becomes a specified maximum applied amount. In the example of FIG. 6, a test pattern is formed with five light levels of LPW1 to LPW5, the relationship between the light level and the toner loading amount is obtained, and the light level that is the prescribed maximum loading amount is determined from the obtained relationship. Yes.

  Subsequently, using the light level determined in S12, the CPU 313 forms a gradation pattern on the recording material 110 by pseudo halftone processing, and measures the formed gradation pattern to generate a γLUT. The generated γLUT is used in the gradation correction unit 316. Note that the relationship between the detected brightness and the applied toner amount shown in FIG. 5 differs depending on the type of recording material. Therefore, a predetermined reference recording material is used when performing calibration.

  The image forming apparatus can control the glossiness of the output image according to the melting degree of the toner, and the image forming apparatus according to this embodiment can set the glossiness by the user. FIG. 7 shows the relationship between the set gloss level and the fixing condition (fixing temperature). In FIG. 7, the glossiness can be set in a total of seven stages from -3 to +3 with reference to the standard setting. As shown in FIG. 7, a fixing temperature is associated with each gloss level.

  The density detected by the optical sensor increases as the amount of irregularly reflected light decreases. This irregularly reflected light is affected by the degree of light absorption by the toner and the roughness (unevenness) of the toner surface. Specifically, as shown in FIGS. 8A and 8B, the density increases as the amount of light absorbed by the toner increases. Further, as shown in FIGS. 8C and 8D, even if the amount of applied toner is the same, as the toner surface becomes smoother, the regular reflection component increases and the irregular reflection component decreases, so that it is detected. The concentration becomes high. The smoother the toner surface, the higher the glossiness. Therefore, as shown in FIG. 9, the applied toner amount with respect to the luminance A detected by the color sensor 200 varies depending on the set glossiness. Therefore, in the case of maximum density control and gradation control, it is necessary to consider the set gloss level, that is, the set fixing conditions.

  FIG. 10 is a flowchart of calibration according to the present embodiment, that is, maximum density control and gradation control. Before executing the process shown in FIG. 10, the CPU 313 executes the processes of S10 and S11 in FIG. 4 to determine the charging potential and the developing bias. First, the case of maximum density control will be described. In step S20, the CPU 313 determines the set fixing condition, and in step S21, determines whether the setting is standard. The standard setting is, for example, a predetermined fixing condition such as a glossiness of 0 in FIG. If the fixing condition is not the standard setting, the CPU 313 changes the fixing condition to the standard setting in S22. Subsequently, as described above, the CPU 313 forms test patterns at a plurality of light levels for each color in S23. The fixing conditions at this time are standard settings. When the CPU 313 acquires the measurement result from the color sensor 200 in S24, the CPU 313 obtains the relationship between the light level and the applied toner amount for each color from the relationship shown in FIG. 5 in S25. The relationship of FIG. 5 used at this time is the relationship between the detected luminance and the toner applied amount when the fixing condition is set as a standard setting. In step S26, the CPU 313 determines whether the current control is maximum density control or gradation control. If it is maximum density control, the CPU 313 determines the maximum specified from the relationship between the light power obtained in step S26 and the applied toner amount. In step S27, the optical power to be loaded is determined. In the case of gradation control, a test pattern for gradation control is formed in S23, and a γLUT is generated in S28.

  In the present embodiment, at the time of calibration, the fixing condition is returned to the standard setting to form a test pattern. With this configuration, the amount of applied toner can be maintained in a specified state, and calibration accuracy can be improved.

<Second embodiment>
Next, the second embodiment will be described focusing on the differences from the first embodiment. In the first embodiment, when the fixing condition is not the standard setting, the test pattern is formed after returning to the standard setting. Therefore, when the fixing condition is returned to the standard setting, a waiting time for adjusting the fixing temperature occurs. In the present embodiment, this waiting time is prevented and the calibration time is shortened.

  FIG. 11 is a flowchart of processing performed by the CPU 313 in this embodiment. Hereinafter, differences from the first embodiment of FIG. 10 will be described. In this embodiment, after determining the fixing conditions set at the time of executing calibration in S30, a test pattern is formed in S31 using the fixing conditions as they are, and the measurement results are obtained from the color sensor 200 in S32. get. In step S33, the CPU 313 obtains the relationship between the light level and the applied toner amount for each color from the relationship shown in FIG. Note that the relationship of FIG. 5 used at this time is the relationship between the detected luminance and the applied toner amount in the setting of the fixing condition determined in S30. That is, in the present embodiment, the relationship between the light level and the applied toner amount under each fixing condition is stored in the table storage unit 310 in advance. For example, if the fixing conditions that can be set are as shown in FIG. 7, seven relationships are held for each color. The subsequent processing from S34 to S36 is the same as the processing from S26 to S28 in FIG.

  In the present embodiment, the time required for calibration is shorter than the configuration in the first embodiment. In the above-described embodiment, the fixing condition is changed by adjusting the glossiness. However, the fixing condition is changed depending on other settings such as image quality priority or productivity priority. The present invention is also applicable. Furthermore, in the present embodiment, the test pattern is formed under the fixing conditions set by the user, but it is also possible to change to a fixing condition that is frequently used. For example, when the use of the image forming apparatus is started and the setting of the fixing condition is not changed, the calibration is executed according to the first embodiment. When the setting of the fixing condition is changed, calibration is executed according to the second embodiment, and the used fixing condition is recorded. If the use frequency of the fixing condition can be grasped after a predetermined period elapses, the calibration can be executed under the fixing condition having a high use frequency. It is also possible to determine the setting of the fixing conditions used for calibration based on the frequency of use in the past predetermined period rather than the frequency of use since the start of use of the image forming apparatus.

<Third embodiment>
In the first embodiment and the second embodiment, a predetermined type of recording material is used as a reference recording material, and calibration is performed using the reference recording material. This is because the relationship between the detected luminance and the applied toner amount varies depending on the recording material. However, in addition to the relationship between the detected luminance and the applied toner amount for the reference recording material, for other recording materials, the difference from the relationship of the reference recording material is measured and held in advance. Recording material can be used for calibration. Here, there are recording materials of various basis weights, and some of the recording materials are rough. Therefore, depending on the type of recording material, when high glossiness or low glossiness is set, there is a possibility that measurement will be performed in an area where the density does not change even if the applied toner amount changes. May not be detected.

  Therefore, in this embodiment, for example, when calibration is performed with a recording material other than the reference recording material, a range is provided for the fixing conditions that can be used. In the configuration of the second embodiment, when calibration is performed with a recording material other than the reference recording material and the set fixing condition is outside the range of fixing conditions that can be used with the recording material to be used. The calibration is performed by changing the fixing condition within the range. For example, in the case where the glossiness can be set as shown in FIG. 7, for a certain recording material, the glossiness range corresponding to the fixing condition that can be used for calibration is set to be −2 to +1. In this case, when performing calibration using this certain recording material, if the set glossiness is -3, it is changed to -2, and if it is +2 or +3, it is changed to +1. If the set glossiness is within the range, calibration is performed with the setting. With the above configuration, calibration can be executed with high accuracy using an arbitrary recording material.

Claims (8)

An image forming unit comprising: a forming unit that forms an unfixed image on a recording material; and a fixing unit that fixes the unfixed image formed on the recording material to the recording material according to a set fixing condition;
Measuring means for measuring an image fixed on the recording material by the fixing means;
Control means for performing calibration according to the measurement result of the measurement means,
The image forming apparatus, wherein the control unit sets the fixing condition to a predetermined standard setting when the calibration is executed.   The image forming apparatus according to claim 1, wherein the control unit performs calibration by converting a measurement result of the measurement unit according to conversion information in the standard setting. An image forming unit comprising: a forming unit that forms an unfixed image on a recording material; and a fixing unit that fixes the unfixed image formed on the recording material to the recording material according to a set fixing condition;
Measuring means for measuring an image fixed on the recording material by the fixing means;
Control means for performing calibration according to the measurement result of the measurement means,
The control unit has conversion information corresponding to each setting of the fixing condition, and performs calibration by converting the measurement result of the measuring unit according to the conversion information corresponding to the setting of the fixing condition used at the time of calibration. An image forming apparatus.   The image forming apparatus according to claim 3, wherein the control unit determines a setting of a fixing condition to be used for calibration based on a use frequency of each setting of the fixing condition.   The image forming apparatus according to claim 3, wherein the control unit determines setting of a fixing condition to be used for calibration according to a type of a recording material to be used for calibration.   The control means holds information indicating the setting of the fixing conditions that can be used for the recording material used for calibration, and the setting of the fixing conditions at the time of executing the calibration is used for the recording material used for the calibration. 6. The image forming apparatus according to claim 5, wherein when the fixing condition is not set, calibration is performed by changing the setting to a fixing condition that can be used for the recording material.   The image according to any one of claims 2 to 6, wherein the conversion information is information for converting a measurement result of the measuring unit into a color material amount of an image formed on the recording material. Forming equipment.   The image forming apparatus according to claim 1, wherein the calibration is calibration for maximum density or gradation correction.

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