JP2014219444A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can provide fixed images having desired glossiness according to the various types of recording materials.SOLUTION: A heating control unit 69 uses a measurement recording sheet having a plurality of toner images formed on the single surface and having an image gradation pattern in which image gradation gradually changes, causes a fixing unit 60 to fix toner images at a heating temperature different in every group of the image gradation pattern to form fixed images, causes a glossiness detection sensor 68 to detect the glossiness of the fixed image of every group on the measurement recording sheet, stores the value of the glossiness of the fixed image of every group detected by the glossiness detection sensor 68 in a recording medium 70 as image gradation pattern data having the image gradation and heating temperature associated with each other, refers to the image gradation obtained from pixel data included in image data so that the fixed images have arbitrary glossiness, and control the heating temperature of a heating element 61 on the basis of the image gradation pattern data of every group stored in the storage medium 70.

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine in which these are functionally combined.

  Conventionally, in an electrophotographic image forming apparatus, when a toner image transferred to a recording material is fixed, reproducing the glossiness of the fixed image as a desired glossiness is intended to improve image quality. It is an important matter to consider.

  Mainly to improve the image quality and quality of color images, it is necessary to adjust the gloss level of the fixed image (hereinafter simply referred to as “gloss level”) when fixing the toner image transferred to the recording material. It has been. At this time, the higher the glossiness, the higher the image density, the wider the color gamut, and the higher glossiness is preferred. However, if the glossiness is too high, the amount of reflected light increases, so that there is a problem that visibility is deteriorated particularly in a character image.

  In addition, as a fixing device used in an electrophotographic image forming apparatus, a method in which an unfixed toner image on the surface of a recording material is fixed by heating and pressurizing is adopted. It is known that the glossiness changes depending on fixing conditions such as a conveyance speed.

  However, since the fixing conditions differ depending on the type of recording material, there is a problem that it is difficult to adjust the glossiness for each type of recording material.

  In response to such a problem with glossiness, for example, image formation in which the glossiness on the same surface of the recording material is made uniform by changing the fixing conditions according to the glossiness characteristics of the surface of the recording material itself. An apparatus is disclosed (for example, see Patent Document 1).

  Also, the glossiness judgment image is transferred and fixed on the recording material, and the glossiness is detected by a glossiness detection sensor built in the main body of the apparatus. If the glossiness is not desired, the heating temperature, the conveyance speed, etc. An image forming apparatus that obtains a desired glossiness by repeatedly resetting the glossiness adjustment parameter is disclosed (for example, see Patent Document 2).

  Furthermore, an image forming apparatus is disclosed that stores a change in glossiness at each fixing temperature for an image pattern having a different toner color, and determines optimum fixing conditions for arbitrary image data based on the glossiness data. (For example, see Patent Document 3).

  However, for example, in the method described in Patent Document 1, since the relationship between the temperature at the time of fixing and the conveyance speed of the recording material and the glossiness is stored in the storage device in advance, it supports various recording materials having different glossiness characteristics. There was a problem that we could not do it. Further, since the difference in glossiness characteristics depending on the image gradation is not taken into consideration, there has been a problem that it is impossible to deal with other than a uniform solid image.

  In addition, since the method described in Patent Document 2 employs a feedback method, it can be applied to various recording materials, but the gloss determination image is transferred and fixed each time the glossiness adjustment parameter is changed. There is a need. For this reason, in order to set the fixing conditions for obtaining the optimum glossiness, a lot of test prints and time are required. Also, even when there are different portions in the image tone of the toner image on the same surface of the recording material, the desired glossiness can be obtained throughout the same surface in order to fix at a uniform temperature. The problem was difficult.

  Furthermore, in the method described in Patent Document 3, since an image pattern having a different color material amount is output, a change in glossiness with respect to a change in color material amount can be stored at one time, but in order to obtain temperature dependency of the glossiness However, there is a problem that it takes time to output the image pattern a plurality of times. Also, even when there are different locations in the image tone of the toner image on the same surface of the recording material, a desired glossiness can be obtained over the entire area of the same surface in order to fix at a uniform temperature. The problem was difficult.

  The present invention has been made to solve the above-described conventional problems, and provides an image forming apparatus capable of obtaining a fixed image having a desired glossiness according to various types of recording materials. Objective.

  In order to achieve the above object, an image forming apparatus according to the present invention fixes a toner image on a recording material to a recording material by nip conveyance between a heating unit and a pressing unit, and fixing performed by the fixing unit. Glossiness detecting means for detecting the glossiness of an image, and heating control means for applying different heating temperatures to the heating means on the same surface of the recording material, the heating control means being in the same surface Using a measurement recording material in which a plurality of image gradation pattern toner images having gradually changing image gradations are formed, the fixing means fixes the toner images at different heating temperatures for each set of image gradation patterns. A fixed image is formed, the glossiness detecting means detects the glossiness of the fixed image for each set on the measurement recording material, and the glossiness of the fixed image for each set detected by the glossiness detecting means is detected. Values for image gradation and heating temperature Is stored in the storage unit as image gradation pattern data in association with each other, and the storage unit refers to the image gradation obtained from the pixel data included in the image data so that the fixed image has an arbitrary glossiness. The heating temperature of the heating means is controlled based on the stored image gradation pattern data for each set.

  According to the present invention, it is possible to provide an image forming apparatus capable of obtaining a fixed image having a desired glossiness according to various types of recording materials.

1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention. 1 is a schematic configuration diagram illustrating a fixing device used in an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is an explanatory diagram showing a relationship between an energization pulse voltage of a thermal head and an image gradation pattern in the fixing device used in the image forming apparatus according to the first embodiment of the present invention. It is a comparison graph figure of the relationship between the image area ratio and 60 degree | times glossiness (high quality plain paper) in the image forming apparatus which concerns on the 1st Embodiment of this invention. It is a comparative graph figure of the relationship between the image area ratio and 60 degree | times glossiness (art paper) in the image forming apparatus which concerns on the 1st Embodiment of this invention. FIG. 6 is a comparative graph showing the relationship between the image area ratio and 60 degree glossiness (matte paper) in the image forming apparatus according to the first embodiment of the present invention. It is explanatory drawing of the image gradation pattern in the image forming apparatus which concerns on the 1st Embodiment of this invention. FIG. 3 is a flowchart of a heating temperature control routine for adjusting glossiness in the image forming apparatus according to the first embodiment of the present invention. It is a graph for demonstrating the reduction method when the glossiness level difference is made with the glossiness specified in the low image area ratio, and the actual glossiness. FIG. 5 is a schematic configuration diagram illustrating a fixing device used in an image forming apparatus according to a second structure of the present invention. It is a comparison graph figure of the relationship between the image area ratio and 60 degree | times glossiness (high quality plain paper) in the image forming apparatus which concerns on the 2nd structure of this invention. It is a comparison graph figure of the relationship between the image area rate and 60 degree | times glossiness (art paper) in the image forming apparatus which concerns on the 2nd structure of this invention. It is a schematic block diagram which shows the image forming apparatus which concerns on the 3rd structure of this invention. It is a comparison graph figure of the relationship between the image area ratio and 60 degree glossiness (quality plain paper) in the image forming apparatus which concerns on the 3rd structure of this invention. It is a comparison graph figure of the relationship between the image area ratio and 60 degree | times glossiness (art paper) in the image forming apparatus which concerns on the 3rd structure of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

First, the configuration will be described.
As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment employs an electrophotographic system, and a sheet feeding unit 10 is disposed below the drawing, and an exposure unit 20, an imaging unit 30, The intermediate transfer unit 40, the secondary transfer unit 50, and the fixing unit 60 are provided in the order of the recording material conveyance process. The recording material P after the toner image is fixed by the fixing unit 60 is accumulated via a paper discharge unit (not shown). In the following description, unless otherwise specified, the recording material P is referred to as upstream and downstream based on the conveyance direction of the recording material P.

  The sheet feeding unit 10 is disposed below the inside of the image forming apparatus 1. The paper feed unit 10 includes a drawer-type paper feed cassette 11. The paper feed cassette 11 can store a recording material P such as a sheet of recording paper.

  A sheet feeding roller that feeds the recording material P stored in each sheet feeding cassette 11 one by one from the uppermost one and feeds it to the recording material conveyance path 12 at the upper part on the downstream end side of each sheet feeding cassette 11. 13 is provided. In the paper supply unit 10, a registration unit 14 that adjusts the conveyance timing of the recording material P is disposed between the paper supply roller 13 and the secondary transfer unit 50. In addition, since the specific structure and effect | action of the resist part 14 are well-known, description is abbreviate | omitted. Further, the registration unit 14, the secondary transfer unit 50, the fixing unit 60, and the various conveyance rollers 15 to 18 facing the recording material conveyance path 12 constitute a conveyance unit that nips the recording material P and passes the paper. .

  The exposure unit 20 is disposed above the imaging unit 30. For example, the exposure unit 20 irradiates the imaging unit 30 with laser light L based on image data included in print data transmitted from a personal computer (not shown). Since the specific configuration and operation of the exposure unit 20 are known, description thereof will be omitted. The print data here includes, for example, color / monochrome designation, enlargement / reduction ratio, number of copies, etc. in addition to image data for image formation. The image data includes pixel data.

  The imaging unit 30 includes four image forming units 31Y, 31C, 31M, and 31K for generating toner images for respective colors of yellow, cyan, magenta, and black (hereinafter referred to as Y, C, M, and K). They are arranged in tandem style. These image forming units 31Y, 31C, 31M, and 31K use different colors of Y toner, C toner, M toner, and K toner, but other configurations are common to four colors. Here, the number of colors is not limited, and a configuration having units of five or more colors may be employed. In the following description, the image forming unit 31Y for Y toner will be described as an example. In the following description, for convenience of description and illustration, unless otherwise specified, a common configuration for each color is omitted from the description of Y, C, M, and K, and illustrated.

  The image forming unit 31 includes a charging device 33, an exposure unit 20 (laser light L), a developing device 34, a drum cleaning device 35, and a charge eliminating device (not shown) around the image carrier 32 in the order of the image forming process. . Each of these devices is held by a common holding body and is integrally attached to and detached from the device main body so that they can be exchanged at the same time. Since the drum cleaning device 35 and the static eliminator are those of a known technique, detailed description thereof is omitted here.

  As the image carrier 32, for example, a drum-type photosensitive member is used. The image carrier 32 has an organic photosensitive layer formed on the surface of a drum base, and is rotated in the clockwise direction in the drawing by a driving unit (not shown).

  The charging device 33 is a roller in which a metal core bar is coated with a conductive elastic layer made of a conductive elastic material, and a charging bias is applied thereto. The charging device 33 uniformly charges the surface of the image carrier 32 by generating a discharge between the charging device 33 and the image carrier 32 while contacting or approaching the image carrier 32. In this embodiment, the toner is uniformly charged (for example, −690 V) to the same negative polarity as the normal charging polarity of the toner. As the charging bias, one in which an AC voltage is superimposed on a DC voltage is employed. The charging device 33 may employ a charging charger method such as a charging brush method or a scorotron method instead of a method in which a charging member such as a charging roller is brought into contact with or close to the image carrier 32.

  The surface of the uniformly charged image carrier 32 is optically scanned with a laser beam L emitted from the optical writing unit to carry an electrostatic latent image. Above the image forming unit 31, an optical writing unit serving as a latent image writing means is disposed, and the image carrier 32 is optically scanned with a laser beam L emitted from a laser diode based on image data. By this optical scanning, an electrostatic latent image is formed on the image carrier 32.

  Specifically, of the entire area of the uniformly charged surface of the image carrier 32, the portion irradiated with the laser light L attenuates the potential. As a result, an electrostatic latent image in which the potential of the laser irradiation portion is smaller than the potential of the other portion (background portion) is obtained. The optical writing unit polarizes the laser light L emitted from the light source in the main scanning direction with a polygon mirror that is rotationally driven by a polygon motor (not shown), and passes it to the image carrier 32 via a plurality of optical lenses and mirrors. Irradiation. You may employ | adopt what performs optical writing by the LED light emitted from several LED of the LED array.

  The developing device 34 visualizes the toner image by attaching charged toner to the electrostatic latent image formed on the surface of the image carrier 32. The developing device 34 includes, for example, a developer transport unit that stirs and transports the developer, and a developing unit that stores the developing roller.

  The developer conveying portion is configured by a screw member including a rotating shaft member whose both ends in the axial direction are rotatably supported by bearings, and a spiral blade projecting spirally on the peripheral surface of the rotating shaft member. doing. The screw member rotates to convey the developer to the developing roller while stirring. A toner concentration sensor (not shown) is disposed on the lower wall of the casing in the developer conveying unit, and detects the toner concentration of the developer in the developer conveying unit.

  As the toner concentration sensor, a sensor comprising a magnetic permeability sensor is used. Since the magnetic permeability of the developer containing the toner and the magnetic carrier has a correlation with the toner concentration, the magnetic permeability sensor detects the toner concentration. The image forming apparatus is provided with a toner replenishing unit (not shown) for replenishing toner to the developer transport section of the developing device.

  The main control unit of the image forming apparatus 1 stores Vtref, which is a target value of the output voltage value from the toner density detection sensor, in the RAM. When the difference between the output voltage value from the toner density detection sensor and Vtref exceeds a predetermined value, the toner replenishing means is driven for a time corresponding to the difference. As a result, the toner is supplied to the developer transport section in the developing device 34.

  The developing roller accommodated in the developing unit faces the screw member and also faces the image carrier 32 through an opening provided in the casing. The developing roller includes a cylindrical developing sleeve made of a non-magnetic pipe that is driven to rotate, and a magnet roller that is fixed so as not to rotate with the developing sleeve. Then, while the developer supplied from the screw member is carried on the surface of the developing sleeve by the magnetic force generated by the magnet roller, the developer is transported to the developing region facing the image carrier 32 as the developing sleeve rotates.

  A developing bias having the same polarity as the toner and larger than the electrostatic latent image of the image carrier 32 and smaller than the potential for uniformly charging the image carrier 32 is applied to the developing sleeve. .

  As a result, a developing potential for electrostatically moving the toner on the developing sleeve toward the electrostatic latent image acts between the developing sleeve and the electrostatic latent image on the image carrier 32. Further, a non-developing potential that moves the toner on the developing sleeve toward the sleeve surface acts between the developing sleeve and the background portion of the image carrier 32. By the action of the developing potential and the non-developing potential, the toner on the developing sleeve is selectively transferred to the electrostatic latent image on the image carrier 32, and the electrostatic latent image is developed into a toner image.

  In this embodiment, a development system using a two-component developer including toner and carrier is used. However, a development system using only a single-component developer among these can also be used. .

  When the toner image is developed on the image carrier 32 in this way, the toner image is then sequentially transferred to the intermediate transfer belt 41 of the intermediate transfer unit 40. The transfer residual toner remaining on the surface of the image carrier 32 after the toner image is transferred to the intermediate transfer belt 41 is removed by the drum cleaning device 35 for the image carrier 32 and the surface of the image carrier 32 is cleaned. . Next, the surface potential of the surface of the image carrier 32 is initialized by a static elimination device (not shown) such as a static elimination lamp.

  The intermediate transfer unit 40 is an intermediate transfer method in which the toner image formed on the image carrier 32 is transferred to the intermediate transfer belt 41 and then the toner image is transferred from the intermediate transfer belt 41 to the recording material P.

  The intermediate transfer belt 41 is an intermediate transfer belt on the belt, but the intermediate transfer belt 41 may have a drum shape. An endless intermediate transfer belt 41 is stretched below the image forming unit 31. In addition to the intermediate transfer belt 41 as an image carrier, the intermediate transfer unit 40 includes a driving roller 42, a cleaning backup roller 43, a secondary transfer back roller 44, four primary transfer rollers 45 corresponding to each color, a belt cleaning device 46, a potential. Sensor 47 and the like.

  The intermediate transfer belt 41 is stretched by a driving roller 42, a secondary transfer back roller 44, a cleaning backup roller 43, and four primary transfer rollers 45 disposed inside the loop. The intermediate transfer belt 41 is rotationally moved in the same direction by the rotational force of the driving roller 42 that is rotationally driven by a driving unit (not shown). The volume resistivity of the intermediate transfer belt 41 is, for example, about 1E6 [Ωcm] to 1E12 [Ωcm], and preferably about 1E9 [Ωcm] (Mitsubishi Chemical Hiresta UP MCP HT45 under the condition of an applied voltage of 100V. Measurement).

  The four primary transfer rollers 45 sandwich the rotating intermediate transfer belt 41 with the image carrier 32. As a result, a primary transfer nip for Y, C, M, and K where the surface of the intermediate transfer belt 41 and the image carrier 32 abut is formed.

  A primary transfer bias is applied to the primary transfer roller 45 by a transfer bias power source (not shown). As a result, a transfer electric field is formed between the Y, C, M, and K toner images on the image carrier 32 and the primary transfer roller 45. The primary transfer roller 45 can be separated. For example, when only K is transferred, the primary transfer rollers 45 of other colors are separated. The primary transfer roller 45 includes an elastic roller having a metal core and a conductive sponge layer fixed on the surface thereof. A primary transfer bias controlled by a constant voltage or a constant current is applied to such a primary transfer roller 45. In place of the primary transfer roller 45, a transfer charger, a transfer brush, or the like may be employed.

  First, the intermediate transfer belt 41 enters the primary transfer nip portion for Y toner as the image carrier 32 rotates, and the Y toner image is primarily transferred by the action of the transfer electric field and nip pressure. Thereafter, the intermediate transfer belt 41 sequentially passes through the primary transfer nips for C, M, and K. Then, the C, M, and K toner images of the respective image carriers 32 are primarily transferred to the intermediate transfer belt 41 while being sequentially superimposed. Next, the toner image primarily transferred to the intermediate transfer belt 41 is secondarily transferred from the intermediate transfer belt 41 to the recording material P in the secondary transfer unit 50.

  The secondary transfer unit 50 includes a secondary transfer roller 51 that faces the secondary transfer back roller 44 with the intermediate transfer belt 41 interposed therebetween. The secondary transfer roller 51 forms a secondary transfer nip portion with the intermediate transfer belt 41, and the recording material P enters the secondary transfer nip portion.

  While the secondary transfer roller 51 is grounded, a secondary transfer bias is applied to the secondary transfer back roller 44 by a secondary transfer bias power supply 48. As a result, a secondary transfer electric field that electrostatically moves a negative polarity toner from the secondary transfer back roller 44 side to the secondary transfer roller 51 side between the secondary transfer roller 51 and the secondary transfer back roller 44. Is formed. The secondary transfer bias power supply 48 has a DC power supply, and is applied with a constant voltage or a constant current controlled voltage having the same polarity as the normal charging polarity of the toner.

  The fixing unit 60 used in the image forming apparatus of the present invention has a heating unit and a heating control unit that apply different heating temperatures to different portions of the same surface of the recording material P, and adopts a digital fixing system. Yes. The digital fixing method is, for example, a method in which arbitrary heating temperature control is performed using a low-capacity linear heating body, and a thermal head having a plurality of heating regions in a direction orthogonal to the conveyance direction is used to go straight in the conveyance direction and the conveyance direction. There is a method of performing arbitrary heating temperature control in the direction to perform.

  Specifically, as shown in FIG. 2, the fixing unit 60 includes a heating element 61 as a heating unit, a driving roller 62, a pair of driven rollers 63 and 64, an endless belt 65, and a pressure roller that faces the heating element 61. 66, a temperature sensor 67 for detecting the heating temperature of the heating element 61, a gloss level detection sensor 68 as a gloss level detection unit, and a heating control unit 69 as a heating control unit.

  The endless belt 65 is wound around the heat generating element 61, the driving roller 62, and the driven rollers 63 and 64, and rotates with a predetermined peripheral speed without wrinkles, meandering, or speed delay as the driving roller 62 rotates. To do.

  The pressure roller 66 as a pressure means is a roller body having a rubber elastic layer with good releasability such as silicon rubber. The pressure roller 66 forms a fixing nip portion by sandwiching the endless belt 65 with the heat generating element 61. The pressure roller 66 is opposed to the lower surface of the heat generating element 61 with a predetermined contact pressure by an urging means such as a spring (not shown), and is in the direction in which the recording material P carrying the toner image T is conveyed. Rotate forward.

  The heating element 61 applies different heating temperatures to different portions of the recording material P in the same plane, and a method in which the direction orthogonal to the conveyance direction of the recording material P is a uniform heating temperature and the conveyance direction of the recording material P Even in the same direction orthogonal to each other, there is a method in which a plurality of heating regions are provided to obtain an arbitrary heating temperature. In any case, the heating element 61 preferably has a low heat capacity because arbitrary heating temperature control is performed in the transport direction. For the heating element 61, for example, a linear heating member integrated in the same direction can be used in a method in which the heating temperature is uniformly controlled in a direction orthogonal to the conveyance direction.

  The recording material P conveyed to the fixing nip portion formed by the heat generating element 61 and the pressure roller 66 with the endless belt 65 interposed therebetween is heated and pressed by the heat generating element 61 while being conveyed in the nip by the rotational movement of the endless belt 65. The toner image T is fixed by the pressure of the roller 66.

  Image data included in print data output from a personal computer or the like is input to the heating control unit 69, and heating control of the heating element 61 is performed according to the image data. In this case, since the heating temperature of the heating element 61 cannot be changed in the direction orthogonal to the transport direction, the averaged information of the image data in the same direction is taken, and the heating control of the heating element 61 with respect to the transport direction is performed based on the information. I do. In FIG. 2, the heating control unit 69 is illustrated so as to directly control the heating of the heating element 61, but actually controls the heating driver, heating source, and the like of the heating element 61.

  In the method in which the heating element 61 has a plurality of heating regions in a direction orthogonal to the conveyance direction and performs arbitrary heating control in the direction orthogonal to the conveyance direction, a plurality of heating elements divided in the direction orthogonal to the conveyance direction are arranged. Then, the entire toner image T is fixed by each of the heating elements. The number of heating element divisions is not particularly limited, but four or more divisions are desirable in order to ensure a high degree of glossiness adjustment in each heating region of each divided heating element.

  As shown in FIG. 3, when the heating element 61 is divided into four in the direction orthogonal to the conveyance direction, the heating elements 61 </ b> A to 61 </ b> D into which the heating element 61 is divided are applied to the toner image T corresponding to the image data. Performs pulse energization combining these to fix the toner image T. The heating elements 61A to 61D of the heating element 61 shown in FIG. 3 are the minimum number of divisions for convenience of description, and do not indicate the actual number of divisions. As the actual heating element 61, it is preferable to use a thermal head composed of a heating element divided into 20 along a direction orthogonal to the conveying direction.

  At this time, based on a heating control method described later, heating control is performed on each heating element according to the image density so as to obtain a desired glossiness. Further, when the divided area of the heating element 61 is smaller than one pixel, the average value of the image area ratio for each area is taken from the image data, and the heating control of the heating element 61 for each area is performed based on the information. A region where no image is detected is not heated, or a small amount of heating is performed in response to unintentional toner adhesion such as scumming.

  As described above, in the direction orthogonal to the conveyance direction with respect to the heating element 61, the method of performing arbitrary heating control can be performed with finer heating control than the method of performing uniform heating control, and more precise glossiness adjustment. Heating control can be used. In addition, when the heating element 61 is divided in a direction orthogonal to the transport direction, the thermal head method is used because it becomes possible to perform heating control with higher accuracy as the divided area of each heating element is divided more finely. Is preferred. The divided heating elements may be arranged in a straight line along a direction orthogonal to the conveyance direction, but may be arranged in a staggered pattern shifted in the conveyance direction to eliminate gaps in the divided areas. . Further, the waveform of the energization pulse applied to the heating element 61 may have any shape such as a square wave, a triangular wave, and a sine wave.

  Next, a specific detection method of the gloss level detection sensor 68 will be described.

  The glossiness detection sensor 68 measures the glossiness of the fixed image, and the measured glossiness is recorded in a storage medium 70 such as a RAM. In the gloss measurement, as defined in JISZ8741, the light source 68A and the light receiving unit 68B are installed so that the incident angle θ and the light receiving angle θ ′ are equal to the normal of the image plane.

  Then, a light beam with a certain opening angle is made incident from the light source 68A, and the light beam with a certain opening angle specularly reflected is measured by the light receiving unit 68B.

  In the present embodiment, all measurements were performed at an incident angle θ = 60 degrees. However, the measurement is not necessarily limited to 60 degrees, and when it is desired to increase the glossiness detection accuracy in the case of a fixed image with extremely high glossiness. It is also effective to reduce the incident angle θ. It should be noted that the installation position of the glossiness detection sensor 68 is preferably set at a location where the heat resistance of the glossiness detection sensor 68 accompanying heating of the fixing unit 60 does not become a problem.

  Here, the glossiness is used as the glossiness evaluation, but another value corresponding to the glossiness may be used as the glossiness evaluation. In this embodiment, since it is necessary to detect the glossiness of a fixed image depending on the fixing temperature and the image gradation by one conveyance, an apparatus that outputs one glossiness evaluation value for one image patch. If present, it is necessary to provide a plurality of units in the main operation direction.

  Here, the relationship between the toner area ratio and the glossiness in the recording material P and the image gradation pattern will be described. Here, the fixing conditions and glossiness according to the type of the recording material P were examined as follows.

First, an image sample in which the glossiness of the fixed image was changed for each type of recording material P was created. As the recording material P at that time, high-quality plain paper (70 g / m ² , TYPE 6000 <70 W> manufactured by Ricoh), art paper (127.9 g / m ² , manufactured by Mitsubishi Paper Industries: both sides of Tokuhishi art), matte paper (127 , 9 g / m ² , manufactured by Mitsubishi Paper Industries Co., Ltd .: both sides of Super Matte Art).

As for the glossiness of the image, five levels of glossiness were obtained by changing the heating temperature in the fixing unit 60. Here, the image forming conditions were adjusted so that the toner adhesion amount per unit area in a 100% solid portion of a single color was about 0.4 mg / cm ² .

  The gloss measurement pattern is obtained by gradually changing the image gradation of the image patch of three colors gray. More specifically, an image in which a number of image patches in which a halftone process of a dither having a different screen angle for each color is performed and the image gradation changes with the change in the image area ratio (paper white to solid three colors) is arranged. It is a gradation pattern.

  There are various methods for expressing a change in image gradation, such as an image area ratio, density, brightness, and color material amount. Here, the image area ratio will be described. However, if the matrix data of the glossiness depending on the image gradation and the heating temperature can be acquired, the heating control of the heating element 61 can be performed. Therefore, the image gradation property may be expressed or quantified by any method. .

  The above-mentioned five levels of glossiness are A to E, respectively, and the glossiness characteristics for each type of each recording material P are shown in FIGS.

  4 is high-quality plain paper, FIG. 5 is art paper, and FIG. 6 is matte paper. The horizontal axis of each graph is the area ratio in the image gradation pattern, and the vertical axis is the gloss (Gloss).

  The difference in glossiness depending on the image area ratio is small in the high-quality plain paper shown in FIG. 4, but the change in glossiness is large in the art paper shown in FIG. 5 and the mat paper shown in FIG. On the other hand, in the high-quality plain paper, the portion with the lowest glossiness is the paper surface itself, whereas in the art paper, the portion with the lowest glossiness is a fixed image per medium density (where the image area ratio is medium). As described above, the relationship between the glossiness and the heating temperature varies depending on the type of the recording material P.

  Therefore, in the image forming apparatus 1 of the present embodiment, it is possible to adjust the glossiness for any recording material P by providing the following glossiness test mode.

  For example, as shown in FIG. 7, the image gradation pattern is formed by forming a plurality of image patches along the column direction on the same surface of the measurement recording material P and forming a plurality of sets in the row direction. It is what. Each set of image patches is a CMY three-color gray image patch by changing the ratio of C + M + K little by little. This image gradation pattern is stored in advance in the storage medium 70 of the image forming apparatus.

  In the fixing unit 60, the heating temperature of each row is changed, and the glossiness value depending on the image gradation and the heating temperature in the same plane of the measurement recording material P is acquired.

  The storage medium 70 stores a data table for glossiness test data necessary for acquiring matrix data. The matrix data is data for making it possible to adjust the glossiness of each recording material P by arbitrarily changing the heating temperature of each heating element of the heating element 61 according to the desired glossiness and image data.

  Since the user can perform the glossiness test mode using any type of recording material used as the measurement recording material P, the glossiness can be adjusted for all types of recording material.

  In FIG. 7, the image gradation pattern has different densities along the column direction indicated by the alphabet (A, B, C...), And the temperature change is a numerical value ((1), (2), (3). The temperature is different along the row direction indicated by. Here, for example, it is assumed that heating control is arbitrarily performed using the heating elements 61 </ b> A to 61 </ b> T obtained by dividing the heating element 61 into 20 along the direction orthogonal to the conveyance direction of the measurement recording material P. In such a case, if the image gradation pattern can be fixed so as to achieve a desired heating temperature and image gradation, the arrangement of the heating elements 61 and the conveyance direction of the measurement recording material P are opposite to each other. Either the column direction or the row direction may be used.

  At this time, fixing the image gradation pattern so as to obtain a desired heating temperature and image gradation means that, for example, when the heating elements 61A to 61T are arbitrarily heated, adjacent image patches having different heating temperatures are combined into one image patch. This means that the heating elements 61A to 61T are not heated. Further, in the case of a method in which the heating element 61 is uniformly heated, the measurement recording material P may be conveyed and the heating temperature may be sequentially increased or decreased so that the heating temperature can be changed in the numerical direction.

  Next, as an example of heating control for the heating element 61 by the heating control unit 69 in the present embodiment, the gloss value depending on the image gradation and the heating temperature stored as a data table in the storage medium 70 is acquired. The process flow will be described.

  In FIG. 8, in step S <b> 1, when the glossiness test mode is selected by the user's mode selection operation, the heating control unit 69 causes the imaging unit 30 to perform an image gradation pattern output operation.

  The image gradation pattern image data stored in the storage medium 70 is output from the main control unit (not shown) of the image forming apparatus 1 to the exposure unit 20 and irradiates the imaging unit 31K of the imaging unit 30 with the laser light L. The image gradation pattern image data stored in the storage medium 70 is also output to the heating controller 69.

  In step S2, an image forming operation is performed based on the image data of the image gradation pattern by the exposure unit 20, the imaging unit 30, the intermediate transfer unit 40, and the secondary transfer unit 50, and the recording material P is used as the measurement recording material P. Secondary transfer of gradation pattern. The toner image secondarily transferred to the measurement recording material P is fixed by the fixing unit 60.

  In step S3, the heating control unit 69 acquires the gloss level of the fixed image in each image patch from the gloss level detection sensor 68, and acquires the gloss level in the image gradation corresponding to each image patch.

  In step S4, the heating control unit 69 creates matrix data of glossiness depending on the heating temperature of the heating element 61 and the image gradation as glossiness characteristics.

  Here, in the case of a conventional heating control method for adjusting glossiness, an image gradation pattern is output a plurality of times at different temperatures in order to obtain image gradation pattern data depending on temperature and image gradation. There is a need. For this reason, the operations of step S3 and step S4 are repeated as many times as necessary temperature resolution is obtained.

  On the other hand, in the method of the present embodiment, since the digital fixing method is adopted, a different heating temperature can be applied to the heating element 61 for each set of image gradation patterns, and gloss when the heating temperature is different. Even a fixed image can be obtained at a time. For this reason, the glossiness value depending on the heating temperature and the image gradation can be acquired at once, and the glossiness test mode can be completed in a much shorter time than before, and the usability is improved.

  In step S5, the heating control unit 69 stores the matrix data of the glossiness depending on the heating temperature and the image gradation created by the above procedure in the storage medium 70 as image gradation pattern data. At this time, the heating control unit 69 creates matrix data in association with the conveyance speed of the recording material P at the fixing nip portion, and stores the matrix data in the storage medium 70 as image gradation pattern data. it can.

  Thus, in the image forming apparatus 1, the glossiness test mode is performed for every recording material P scheduled to be used by the user when the recording material P is used for the first time. It is possible to adjust the glossiness to an arbitrary level corresponding to the type of recording material P.

  In the present embodiment, the glossiness adjustment is performed using the three-color gray image gradation data as a representative. However, in order to cope with the monochrome portion, the relationship between the Black image gradation and the glossiness is also examined. A mode for performing more precise glossiness adjustment on the black single color may be provided.

  On the other hand, as shown in step S6, when the fixed image does not have the desired glossiness, the nip conveyance speed of the recording material P in the fixing nip portion is changed for each sheet, and the image gradation pattern is again displayed. Output different glossiness images. Note that changing the nip conveyance speed of the recording material P in units of sheets means that the nip conveyance speed of the same recording material P is not partially changed and nip conveyance is performed at the same speed.

  In this case, the heating control unit 69 determines that the glossiness of each image patch acquired by the glossiness detection sensor 68 is not a value that matches or approximates the reference glossiness stored in advance in the storage medium 70 (No). Then, the conveyance speed of the recording material P is changed in a direction approaching the reference glossiness (step S7). Then, by repeating the routine from step S1 to step S5 and outputting the image gradation pattern again, different glossiness images can be obtained.

  At this time, when the glossiness of each image patch acquired by the glossiness detection sensor 68 is lower than the reference glossiness stored in advance in the storage medium 70, the heating control unit 69 reduces the conveyance speed of the recording material P. To do. The heating control unit 69 increases the conveyance speed of the recording material P when the glossiness of each image patch acquired by the glossiness detection sensor 68 is higher than the reference glossiness stored in advance in the storage medium 70. .

  Even if the output fixed image does not have a desired glossiness by visual observation (No), if there is a manual setting operation by the user, the heating control unit 69 changes the conveyance speed (step S7). The routine from step S1 to step S5 is repeated.

  As described above, with the speeding up of the image forming process, by providing a mode in which the glossiness is given priority over the image forming processing speed, it is possible to meet the needs for high glossiness.

  At this time, the user selects a recording material P to be used and a desired gloss level via an operation panel, a printer driver, or the like, and commands an arbitrary image output.

  The type of recording material P to be used can be arbitrarily added, and the same type of recording material P is used by associating the result of the glossiness test with the type name of the recording material P and storing it in the storage medium 70. When doing so, the glossiness test can be omitted.

  Further, on the glossiness selection screen displayed on the operation panel or the monitor of the personal computer, there are a method of selecting from a visualized glossiness image and a method of selecting from a numerical value and an explanatory text. The selected information is input to the main control unit of the image forming apparatus 1 as part of the print data.

  The print data input to the main control unit of the image forming apparatus 1 includes the setting information described above in addition to the image data related to the image formation itself.

  The heating control unit 69 converts the image data from the setting information into toner adhesion amount information at the time of image output, averages the heating temperature of each region of the heating element 61 for each region, and the image area in the glossiness test mode. The heating temperature of each region is controlled based on the relationship among the rate, temperature, and glossiness.

  However, as shown in FIGS. 4 to 6, when the image area ratio is low, the glossiness depends on the surface state of the recording material P. Therefore, the glossiness higher than the glossiness of the recording material P is selected. However, the glossiness may not be increased on the low image area ratio side.

  When the glossiness specified in the low image area ratio can be extremely different from the designated glossiness, the heating control unit 69, as shown in FIG. 9, has the glossiness at 0% and 50% in the area where the image area ratio is 50% or less. Fixing is performed under fixing conditions that take values closest to an assumed straight line connecting the specified glossiness with a straight line.

  As a result, it is possible to prevent an extreme gloss level difference from occurring in the image gradation. Note that the desired glossiness is not necessarily uniform over the entire surface of the recording material P. Therefore, in the case of the digital fixing method, the heating control region of the heating element 61, that is, each heating element 61A to 61T. The glossiness can be adjusted by controlling the heating.

  Also, depending on the image, the white background of the recording material P is often exposed, and the difference between the glossiness of the white background and the glossiness of the image may be uncomfortable. In such a case, the glossiness of the white background of the recording material P is also measured in the glossiness test mode, and a mode for performing heating control close to the glossiness of the white background, for example, the glossiness of the white background ± 15, may be added. Is possible.

  Therefore, in the case of the recording material P to be used for the first time, the glossiness test mode is performed before performing the image forming process. When the user selects a glossiness for each region where glossiness can be adjusted, heating-controlled digital fixing is performed based on the result of the glossiness test mode, and an image with a desired glossiness can be obtained.

  In the glossiness test mode, the user may select the glossiness for each area where the glossiness can be adjusted and automatically perform fixing, or automatically adjust the glossiness close to the above-mentioned glossiness. The user burden may be reduced by going.

  As described above, according to various types of recording materials P, a fixed image having a desired glossiness can be obtained even for images having different densities in the same plane.

(Embodiment 2)
By the way, in the above embodiment, the heating element 61 of the fixing unit 60 performs only heating. However, for example, as shown in FIG. 10, a fixing unit 80 having a cooling peeling structure can be arranged. . Each structure of the image forming apparatus excluding the fixing unit 80 shown in the second embodiment is the same as that in the above embodiment.

  The cooling and peeling type fixing unit 80 shown in the second embodiment includes a heating element 81, a driving roller 82, driven rollers 83, 84, and 85, an endless belt 86, a pressure roller 87, a cooling device 88, and a temperature sensor 89. Have. The fixing unit 80 employs a digital fixing method in the same manner as the fixing unit 60 used in the image forming apparatus 1 according to the present embodiment illustrated in FIGS. 1 and 2. As the heating element 81, it is preferable to use a thermal head composed of a heating element divided into 20 along a direction orthogonal to the conveying direction.

  The driven roller 84 rotates following the rotational movement of the endless belt 86 and stretches the endless belt 86 in a tensioned state. As a result, the recording material P is naturally peeled from the endless belt 86 by the rigidity of the recording material P, and is discharged from the fixing nip portion.

  The endless belt 86 is wound around the driving roller 82, driven rollers 83, 84, and 85 and the heat generating element 81, and is driven to rotate at a predetermined peripheral speed without wrinkles, meandering, or speed delay as the driving roller 82 rotates. Is done. The endless belt 86 is composed of a heat-resistant base layer and a release layer, and the base layer is composed of a metal sheet made of nickel, aluminum, stainless steel, or a heat-resistant resin such as PET, PBT, polyimide, polyimide amide or the like.

  The release layer is made of silicon rubber, fluororubber, fluororesin, or the like, and is required to be easily separated from the toner image T and the recording material P. The endless belt 86 is in contact with the surface of the recording material P on which the color toner image is formed at the fixing nip portion between the heat generating element 81 and the pressure roller 87, and heats and melts the color toner image and the transparent toner image. Fix to P.

  The pressure roller 87 as a pressure unit is a roller having a rubber elastic layer with good releasability such as silicon rubber. The pressure roller 87 has an endless belt 86 sandwiched between the heat generating element 81 and is opposed to the lower surface of the heat generating element 81 with a predetermined contact pressure by a biasing means such as a spring. It rotates in the forward direction in the conveying direction of the material P.

  The cooling device 88 is disposed inside the endless belt 86 and between the heat generating element 81 located on the upstream side in the rotation direction of the endless belt 86 and the driven roller 84 located on the downstream side. Although the cooling device 88 is not particularly limited, an air-cooled heat sink made of aluminum is used here. The cooling device 88 has a length of about 80 mm along the conveyance direction of the recording material P. The cooling device 88 cools the endless belt 86, thereby adjusting the ambient temperature when the recording material P after fixing is peeled off from the endless belt 86. The cooling temperature by the cooling device 88 is a temperature of 70 ° C. or less at which the toner layer constituting the fixed image is sufficiently solidified, preferably 20 to 70 ° C., more preferably room temperature (around 25 ° C.).

  In such a configuration, the recording material P and the endless belt 86 are conveyed to the driven roller 84 in a state of being bonded via the molten toner image T. During this time, the endless belt 86 and the toner image T are transferred to each other. It is cooled by the cooling device 88.

  Therefore, when the recording material P reaches the driven roller 84, the recording material P is separated from the endless belt 86 due to the curvature of the driven roller 84 and the rigidity of the recording material P.

  As described above, the surface of the fixed image of the recording material P is smoothed, and a high gloss color image is formed.

  When such a fixing unit 80 is disposed in place of the fixing unit 60 shown in the above embodiment, a glossiness detection sensor 68 is disposed downstream of the fixing unit 80, and the glossiness after fixing is determined. The measured glossiness is recorded in the storage medium 70.

  Each of the divided heating elements of the heat generating element 81 is not heated unless an image is detected in the area of the fixing object, and only the image portion is heated by pulse energization if an image is detected. The toner image T is fixed.

  At this time, based on the heating control method similar to that of the image forming apparatus 1 according to the above-described embodiment, heating control is performed so that a desired glossiness is obtained for each region having a different image density. When the number of divided regions of the heating elements is smaller than the number of pixels, an average value for each region is taken from the image data, and heating control of the heating element 81 for each region is performed based on the information.

Here, the fixing condition and the glossiness according to the type of the recording material P were investigated using such a fixing unit 80 of the cooling peeling method. As the recording material P, two types of high-quality plain paper (70 g / m ² , RICOH TYPE6000 <70W>) and art paper (127.9 g / m ² , Mitsubishi Paper Industries: Tokuhishi art both sides) were used.

As for the glossiness of the image, five levels of glossiness were obtained by changing the heating temperature in the fixing unit 80. Here, the image forming conditions were adjusted so that the toner adhesion amount per unit area in a 100% solid portion of a single color was about 0.4 mg / cm ² .

  The gloss measurement pattern is an image gradation pattern in three-color gray, and an image gradation pattern with different image area ratios (dithered from white paper to three-color overlay) subjected to halftone processing of dither having different screen angles for each color. Several image patches are arranged side by side. The above five levels of glossiness were F to J, respectively. The gloss characteristics for each type of recording material P are shown in FIGS.

  11 is high-quality plain paper, FIG. 12 is art paper, the horizontal axis of each graph is the area ratio in the image gradation pattern, and the vertical axis is the glossiness (Gloss).

  As can be seen from FIGS. 11 and 12, the relationship between the glossiness and the heating temperature varies depending on the type of the recording material P even when the fixing unit 80 of the cooling peeling type is used.

  The second embodiment also has a glossiness test mode, and the same heating control can be performed based on the result of the glossiness test mode. By the above method, a fixed image having a desired glossiness and a high glossiness can be obtained for all recording materials P even if the density is different within the same plane.

(Embodiment 3)
FIG. 13 is a schematic configuration diagram illustrating an image forming apparatus according to the third embodiment. In the third embodiment, the image forming apparatus 2 is separated into the image forming apparatus main body 3 and the smoothing processing apparatus 4 independently.

  Of the image forming apparatus main body 3, the process in the image forming processing unit that forms an image on the recording material P is the same as that of the image forming apparatus 1 according to the embodiment, and is an electrophotographic tandem type full color image forming apparatus. . The image forming apparatus main body 3 is provided with a fixing unit 90 instead of the fixing unit 60 of the above embodiment. The full-color toner image T formed on the recording material P through the same process as the image forming apparatus 1 in the above embodiment is fixed by the fixing unit 90.

  The fixing unit 90 uses a heat roller type fixing method and is not limited as long as the toner image T is fixed by heating and pressing. In the fixing unit 90 shown in FIG. 13, a fixing roller 91 and a pressure roller 92 are arranged to face each other.

  The full color fixed image of the recording material P fixed in this way is subjected to a smoothing process by the smoothing processing device 4.

  The smoothing processing device 4 has a cooling peeling type fixing unit having the same structure as the fixing unit 80 shown in the second embodiment. Note that the same reference numerals are given to the same components as those of the fixing unit 80, and the description thereof is omitted.

  In the smoothing processing device 4, the recording material P is sandwiched and conveyed between the endless belt 86 and the pressure roller 87, and is refixed by the heating element 81 at the heating temperature for each area division. Thereafter, the recording material P is cooled by the cooling device 88 in a state where the surface of the endless belt 86 and the surface of the recording material P are in close contact with each other. As a result, the recording material P is peeled from the endless belt 86 by the curvature of the driven roller 84. As described above, the image surface of the recording material P is smoothed, and a high gloss color image is formed.

  The investigation was performed in exactly the same manner as the investigation of the fixing conditions and glossiness performed in the image forming apparatus 2 of the second embodiment.

As the recording material P, two types of high-quality plain paper (70 g / m ² , RICOH TYPE6000 <70W>) and art paper (127.9 g / m ² , Mitsubishi Paper Industries: Tokuhishi art both sides) were used. The results are shown in FIGS. 14 is high-quality plain paper, and FIG. 15 is art paper. The horizontal axis of each graph is the area ratio in the image gradation pattern, and the vertical axis is the gloss (Gloss).

  As can be seen from FIGS. 14 and 15, the results of the investigation in the fixing unit 80 according to the structure of the second embodiment are almost the same, and the relationship between the gloss level and the heating temperature differs depending on the type of the recording material P.

  The third embodiment also has a gloss test mode, and heating control similar to that of the second embodiment can be performed as reheating control based on the result of the gloss test mode.

  According to the above method, a fixed image having a desired glossiness and a high glossiness can be obtained for any recording material P even if the toner images T have different densities in the same plane. In the case of the configuration of the third embodiment, the presence / absence of the smoothing processing device 4 can be selected as an option according to the intended use, which is effective for space saving and energy saving.

  As described above, the image forming apparatus 1 according to the present embodiment can obtain a fixed image having a glossiness corresponding to the type of the recording material P.

  As described above, the heating control unit 69 uses the measurement recording material P in which a plurality of sets of toner images having an image gradation pattern whose image gradation gradually changes in the same plane, and the fixing unit 60 performs the image gradation pattern. The toner images are fixed at different heating temperatures for each set to form a fixed image, and the glossiness detection sensor 68 detects the glossiness of the fixed image for each set on the measurement recording material. The gloss value of the fixed image for each set detected in step S is stored in the storage medium 70 as image gradation pattern data in which the image gradation and the heating temperature are associated, so that the fixed image has an arbitrary glossiness. With reference to the image gradation obtained from the pixel data included in the image data, the heating temperature of the heating element 61 is controlled based on the image gradation pattern data for each set stored in the storage medium 70. ,various It is possible to obtain a fixed image of a desired degree of gloss in accordance with the recording material P classes.

  Note that the image forming apparatus 1 according to the present embodiment is applied to one image forming apparatus 1, but for example, the image forming apparatus 1 or another image forming apparatus similar to the image forming apparatus 1 is used. The glossiness depending on the temperature and the image gradation is detected by one transport in the same manner as the image forming apparatus 1, and the matrix data of the glossiness depending on the heating temperature and the image gradation is used as the image gradation pattern data. The image data can be stored in an external storage unit, and the image forming apparatus 1 and other image forming apparatuses can share image gradation pattern data and perform heating control to obtain an arbitrary gloss level. In this case, heating control for a plurality of image forming apparatuses can be performed based on image gradation pattern data acquired by one image forming apparatus 1. The external storage means may be an apparatus that is directly connected to the image forming apparatus 1 such as an external hard disk, or may be an external storage medium or storage method of a type that is stored through an electric communication line such as the Internet.

  As described above, the image forming apparatus according to the present invention has an effect that a fixed image having a desired glossiness can be obtained according to various types of recording materials. It is also useful for various electrophotographic image forming apparatuses such as facsimile machines and copy machines.

1 Image forming apparatus 60 Fixing section (fixing means)
61 Heating element (heating means)
66 Pressure roller (Pressure means)
68 Glossiness detection sensor (Glossiness detection means)
69 Heating control unit (heating control means)
70 Storage medium (storage means)
P Recording material

JP 2000-284548 A JP 11-119484 A JP 2011-170125 A

Claims (7)

Fixing means for fixing the toner image on the recording material to the recording material by nip conveyance between the heating means and the pressure means;
Glossiness detecting means for detecting the glossiness of the fixed image fixed by the fixing means;
Heating control means for applying different heating temperatures to the heating means within the same surface of the recording material;
With
The heating control means includes
Using a measurement recording material in which a plurality of image gradation pattern toner images whose image gradation gradually changes in the same plane are formed,
A fixing image is formed by fixing the toner image at a different heating temperature for each set of the image gradation patterns by the fixing unit;
The glossiness detection means detects the glossiness of the fixed image for each set on the measurement recording material,
The glossiness value of the fixed image for each set detected by the glossiness detection means is stored in the storage means as image gradation pattern data in which the image gradation and the heating temperature are associated,
The heating is performed based on the image gradation pattern data for each set stored in the storage unit with reference to the image gradation obtained from the pixel data included in the image data so that the fixed image has an arbitrary glossiness. An image forming apparatus, wherein the heating temperature of the means is controlled to be heated. The heating means includes
2. The image according to claim 1, wherein different heating temperatures are applied to a plurality of regions divided in a direction along the recording material conveyance direction and a direction orthogonal to the conveyance direction within the same surface of the recording material. Forming equipment. The heating control means includes
While changing the nip conveyance speed of the recording material in the fixing means in units of sheets, the image gradation pattern is output to the recording material to detect the glossiness,
The glossiness value of the fixed image for each set detected by the glossiness detection means is stored in the storage means as image gradation pattern data in which the image gradation, the heating temperature, and the nip conveyance speed are associated,
The image forming apparatus according to claim 1, wherein fixing conditions including a heating temperature of the heating unit and a nip conveyance speed are changed based on an image area ratio obtained from pixel data.   The image forming apparatus according to claim 1, further comprising a plurality of glossiness detection units. The fixing means is
A fixing roller for heating the recording material on which the toner image is formed;
An endless belt wrapped around a fixing roller;
A pressure roller that forms a fixing nip portion that is pressed against the fixing roller via the endless belt and nips the recording material;
A cooling means for cooling the recording material conveyed in the nip while being in close contact with the endless belt before separation from the endless belt;
5. The image forming apparatus according to claim 1, wherein the image forming apparatus is a cooling and peeling type fixing device having the above. The fixing means is
It is a fixing device of the cooling and peeling method that reheats the fixed image on the recording material once fixed,
The fixing device includes:
6. The image forming apparatus according to claim 1, wherein the image forming apparatus can be separated independently of an apparatus having an image forming processing unit for transferring a toner image onto a recording material. Using a measurement recording material in which a plurality of image gradation pattern toner images whose image gradation gradually changes in the same plane are formed, the toner images are fixed at different heating temperatures for each set of the image gradation patterns. An image gradation pattern forming step for forming a fixed image;
Glossiness detection step for detecting the glossiness of the fixed image for each set on the measurement recording material,
A storage step of storing in the storage means the gloss value of the fixed image for each set detected in the gloss level detection step as image tone pattern data in which the image tone and the heating temperature are associated;
A toner image based on the image gradation pattern data of each set stored in the storing step with reference to the image gradation obtained from the pixel data included in the image data so that the fixed image has an arbitrary glossiness A heating control step for controlling the heating temperature for fixing the recording material to the recording material;
An image forming method comprising: