JP2010210762A - Image forming apparatus, image forming method, program and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately perform control of a fixing condition using surface diffused light by accurately measuring the surface diffused light even when a toner adhesion amount is varied. <P>SOLUTION: A fixing device 30 fixes a toner image transferred to recording material, a spectral colorimeter 41 measures a spectral reflectance factor Rf on a front surface of the fixed toner image, a spectral colorimeter 42 measures a spectral reflectance factor Rb on a back surface of the fixed toner image, and a calculation part 152 computes a difference value (Rf-Rb) to calculate the surface diffused light corresponding to the difference value. A fixing condition controller 110 controls a fixing condition (temperature) based on the calculated surface diffused light. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a color copying machine, a color printer, and a color FAX using an electrophotographic system, and a fixing condition setting method.

  In recent years, color image forming apparatuses such as color printers and color copiers are required to improve the output image quality. In an electrophotographic image forming apparatus configured as a printer, a copier, a facsimile, or a complex machine thereof, an electrostatic latent image is written by irradiating light onto a photosensitive drum charged by a charging device. By supplying toner to the photosensitive drum by a developing device, the electrostatic latent image is developed as a toner image (forming a toner image), and the toner image is directly on a predetermined recording material such as recording paper or in the middle An image forming process is performed in which the image is indirectly transferred via an intermediate recording material such as a transfer belt and finally heated and fixed by a heating roller or the like provided in the fixing device.

  Such an image forming apparatus is formed on a recording sheet due to a change in toner adhesion amount or toner image fixability due to a change in an environment in which the apparatus is installed or aged deterioration of a photosensitive drum or a developer. The color reproducibility and glossiness typified by the image density vary. Therefore, a method is widely used in which the image density and glossiness are monitored and the results are fed back to control the density and glossiness so that the desired density and glossiness can be obtained even if each part of the apparatus fluctuates. . There are the following techniques as conventional examples related to these.

  For example, the density of the image before and after fixing of the control patch image to be output and the glossiness of the image after fixing are measured, and the density control value (image forming condition) is determined from the density measurement result, and the density There is an apparatus for controlling the gloss control value (fixing condition) based on the control value and the measurement result of the gloss level (see, for example, Patent Document 1).

  Similarly, there is also an apparatus for determining the density and the glossiness by measuring the density of the control patch before and after fixing the toner image, and controlling the image forming conditions and the fixing conditions based on them (for example, Patent Document 2). See).

  Here, the image forming conditions are, for example, a setting value of a developing bias potential, a setting value of a charging potential of an image carrier (photosensitive member), an exposure intensity for the image carrier (exposure intensity for writing an electrostatic latent image) One or a plurality of set values of the ratio between the peripheral speed of the rotating image carrier and the peripheral speed of the developing roller rotating opposite to this (so-called peripheral speed ratio). And mainly relates to control of the toner adhesion amount. The fixing conditions include, for example, one or a plurality of fixing temperatures, nip pressures, and recording material conveyance speeds, and mainly relate to control of fixing properties.

  However, the conventional technique for controlling the fixing conditions using the above-described glossiness and density as target values has a problem that a desired color cannot be reproduced for the following reasons.

  First, it will be explained that the color reproducibility depends not only on the toner adhesion amount but also on the fixing property. When the image is irradiated with light in a normal colorimetry system and the reflected light is measured, the reflected light to be measured includes surface diffused light reflected from the image surface and reflected light from the toner layer. Yes. When this surface diffused light increases, the light reflected without touching the color material inside the toner layer increases, and the reproducible color space becomes smaller (the color becomes dull).

  FIG. 23A shows the relationship between surface diffused light and saturation. FIG. 23A shows how the saturation decreases as the surface diffused light increases. Thus, it can be seen that the color reproducibility depends on the surface diffused light. Since this surface diffused light depends on the surface state of the image, that is, the fixability, it can be seen that the color reproducibility depends on the fixability.

  FIG. 24 is a diagram for explaining the principle of measurement of surface diffused light. FIG. 24A shows how the reflectance of a toner image is measured by a measurement system of 0/45 ° (0 ° incidence, 45 ° light reception). At this time, the reflected light 201 to be measured includes reflected light (surface diffused light) 201 a from the surface of the toner layer 211 and reflected light (internally reflected light) 201 b from the toner layer 212. Reference numeral 211 denotes a recording material.

  On the other hand, FIG. 24B shows a state in which a transparent film 213 having a mirror surface is optically adhered to the surface of the toner image of FIG. 24A and is measured by the same optical system as in FIG. Show. Here, the A layer and the B layer are in optical contact refers to a state in which there is no air layer between them and the interface between them is optically continuous. At this time, the reflected light 202a on the surface in FIG. 24B is specularly reflected because the surface is in a mirror state as described above, and is reflected in the 0 ° direction. Further, as described above, the toner layer 212 and the transparent film 213 are in optical contact, and no air layer or the like exists between them. Further, it is preferable that the refractive indexes are equal to prevent reflected light from being generated at the interface between the toner layer 212 and the transparent film 213. Therefore, at this time, the reflected light 202 received is only the internally reflected light 202b. Since the internally reflected light 201b and 202b are equal, by subtracting 202 from the measured value 201, the internally reflected light is canceled and the surface diffused light 201a can be obtained. The surface diffused light thus obtained can be directly incorporated into the color evaluation because the color colorimetry system and the measurement system are equal as described above.

  As described above, when the fixing property changes due to deterioration of the apparatus over time, it is desirable that the fixing conditions can be controlled so that the target color reproduction can be maintained. However, as described above, the conventional technique of measuring the glossiness and density and controlling the fixing conditions cannot achieve the desired color reproduction.

  First, since the glossiness differs in color and measurement system, the color cannot be directly evaluated from the glossiness. FIG. 25 shows a measurement optical system for glossiness and color. FIG. 25A shows a glossiness measurement system, and FIG. 25B shows a color measurement system. As shown in FIG. 25 (a), the gloss level measures specularly reflected light, whereas as shown in FIG. 25 (b), the color measures diffused light. Accordingly, the glossiness is not directly related to the color and cannot be used for the evaluation of the color (note that the 0/45 ° system (0 ° incidence, 45 ° light reception) is shown in FIG. 25 (b). The system also includes 0 / d (measurement with an integrating sphere), etc. In any case, the color measurement system measures diffuse light).

  Further, the glossiness has no one-to-one correlation because the measurement system is different from the surface diffused light using the same measurement system as the color. FIG. 23B shows the relationship between glossiness and surface diffused light. As described above, the gloss level is for measuring regular reflection light and is related to the unevenness of the surface. However, as shown in FIG. 23B, the surface diffused light is not uniquely determined for a certain gloss level. It has some width. Therefore, the surface diffused light cannot be controlled by the glossiness. As described above, the target color can be reproduced by controlling the surface diffused light. However, since the glossiness cannot control the surface diffused light as described above, the target color cannot be reproduced indirectly by the glossiness.

  Next, when the density is used for controlling the fixing conditions, since the density is calculated only from the average value of the spectral reflectance or the value of the absorption band, the L * a * b * value representing the color is uniquely determined by the density. I can't. That is, even if the density is controlled to a desired value, the L * a * b * value of the reproduced color may be deviated, so that the target color cannot be controlled. Even if the spectral reflectance (spectral density) is measured and used for control, the spectral reflectance is a value including both internally reflected light and surface diffused light, that is, fluctuation in toner adhesion amount and fixability. Including both fluctuations. Therefore, when the density changes, it cannot be determined whether the toner adhesion amount fluctuation or the fixing property fluctuation is caused, and appropriate control cannot be performed.

  Therefore, the applicant previously proposed an image forming apparatus that measures surface diffusion light on a patch image transferred and fixed on a recording material and controls fixing conditions based on the measured surface diffusion light. By controlling the fixing conditions based on light, it is possible to obtain a desired color reproduction (Japanese Patent Application No. 2008-238089).

  By the way, in the method proposed above, in the measurement principle of the surface diffused light shown in FIG. 24, the reflection characteristic 1 in the specular state shown in FIG. Using a spectrocolorimeter or the like, the non-specular reflection characteristic 2 corresponding to FIG. 24A is measured, and surface diffused light is calculated from the reflection characteristics 1 and 2. This method is based on the assumption that the toner adhesion amount does not vary.

  However, in an actual image forming apparatus, the toner adhesion amount also varies depending on the environment in which the apparatus is installed and the aging of the apparatus. At this time, the reflection characteristic 2 changes according to the fluctuation of the toner adhesion amount, but the reflection characteristic 1 stored in the memory does not follow the fluctuation of the toner adhesion amount and remains constant. Originally, the measurement principle of the surface diffused light shown in FIG. 24 was based on the premise that the toner images of (a) and (b) are the same. Since both are the same, even if the toner adhesion amount fluctuates, the fluctuation amount is common to both, so it is canceled out when the difference is taken, and the surface diffused light can be obtained correctly.

  However, in the previously proposed method, the reflection characteristics in the mirror surface state corresponding to FIG. 24B are treated as fixed, so that fluctuations in the toner adhesion amount cannot be absorbed, and the surface diffused light enters as noise. End up. As a result, there has been a problem that the surface diffused light cannot be measured correctly when the toner adhesion amount fluctuates.

The present invention has been made in view of the above problems,
An object of the present invention is to provide an image forming apparatus, a method, a program, and a recording medium that perform high-precision fixing condition control using surface diffused light by accurately measuring surface diffused light even when the toner adhesion amount fluctuates. To provide a medium.

  The present invention provides an image forming unit that forms a patch toner image having an area ratio of 100% and transfers the patch toner image to a recording material, a fixing unit that fixes the toner image transferred to the recording material under predetermined fixing conditions, and the fixing An image forming apparatus comprising: surface diffused light acquiring means for obtaining surface diffused light from the surface of the toner image obtained; and control means for controlling the predetermined fixing condition based on the acquired surface diffused light. The surface diffused light acquiring means includes first measuring means for measuring the first reflection characteristic from the surface of the toner image formed on the transparent film, and second from the back surface of the toner image on the transparent film. The main feature is that it comprises second measuring means for measuring reflection characteristics and surface diffused light calculating means for calculating surface diffused light from the first and second reflection characteristics.

  According to the present invention, even if the toner adhesion amount fluctuates, the surface diffused light is accurately measured, so that the fixing condition control using the surface diffused light can be performed with high accuracy.

The system configuration | structure of Example 1 of this invention is shown. 1 illustrates a configuration of an image forming unit according to a first exemplary embodiment. The structural example of the spectral colorimeter of Example 1 is shown. It is a figure explaining the acquisition principle (black back) of surface diffused light. It is a figure explaining the acquisition principle (white back) of surface diffused light. 3 is a flowchart illustrating a fixing condition control operation according to the first exemplary embodiment. The patch images of Examples 1 and 3 are shown. The correspondence between Rf-Rb and surface diffused light is shown. The table referred in Example 1, 3, 4, 5 is shown. The correspondence relationship between the fixing temperature / conveying speed and the surface diffused light is shown. The system configuration | structure of Example 2 is shown. 2 illustrates a configuration of an image forming unit according to a second exemplary embodiment. The system configuration | structure of Example 3 is shown. 3 shows a configuration of an image forming unit according to Embodiment 3. 9 is a flowchart illustrating a fixing condition control operation according to the fourth exemplary embodiment. The correspondence between adhesion amount and surface diffused light is shown. The system configuration | structure of Example 5 is shown. 10 illustrates a configuration of an image forming unit according to a fifth exemplary embodiment. 9 is a flowchart illustrating a fixing condition control operation according to the fifth exemplary embodiment. The correspondence relationship between the fixing temperature and the surface diffused light in the plain paper / OHP mode is shown. The fixing conditions and the like in the plain paper mode referred to in the sixth embodiment will be shown. 10 is a flowchart of a fixing condition control operation according to the sixth embodiment. It is a figure explaining the prior art (relationship between surface diffused light and saturation). It is a figure explaining prior art (measurement of surface diffused light). It is a figure explaining a prior art (measurement optical system).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  Example 1 is an example in which the spectral reflectance is used as the reflection characteristics 1 and 2, and the measuring means 1 and 2 which are spectrocolorimeters are arranged facing each other. In general, the image forming apparatus holds different setting values (modes) of fixing conditions for an OHP sheet and plain paper, but this embodiment is a preferred embodiment for the fixing condition control in the OHP mode.

  FIG. 1 shows a system configuration of Embodiment 1 of the present invention. In FIG. 1, reference numeral 100 denotes an image forming unit having a paper feeding unit 21, a writing optical system 24, an image forming unit 103 that forms a toner image on a photosensitive drum by a process step according to an electrophotographic process and transfers the toner image to a recording material. A fixing condition control unit 120 includes a driver 111 that controls predetermined fixing conditions, for example, a driver 111 that energizes a heater so as to reach a predetermined fixing temperature, a storage unit 112 that stores fixing conditions, and the like. , A main control unit that controls the entire image forming apparatus; 130, an image processing unit that executes various image processing; 140, an operation display unit that has a function of displaying various input settings and the state of the apparatus; , A memory 151 for storing data to be described later, a surface diffused light calculation unit having a calculation unit 152 for calculating the surface diffused light, and 30 a fixing roller 31 and a pressure roller 32 A fixing device having, 41 and 42, described later spectrophotometer, 33, 34 heater, 35a, b is a thermistor for detecting the fixing temperature. Reference numeral 160 denotes a surface diffused light acquisition unit including the spectrocolorimeters 41 and 42 and the surface diffused light calculation unit 150.

  FIG. 2 shows in detail the configuration of the image forming unit 100, the fixing unit 30, and the spectrocolorimeters 41 and 42 shown in FIG. The apparatus shown in FIG. 2 is a tandem color image forming apparatus that employs an intermediate transfer member 27, which is an example of an electrophotographic color image forming apparatus, but may have other configurations such as a revolver color image forming apparatus. .

  This color image forming apparatus includes a paper feeding unit 21, photoconductors (22Y, 22M, 22C, 22K) for each station arranged in parallel for development colors, injection charging means (23Y, 23M, 23C, 23K) as primary charging means, Toner cartridge (25Y, 25M, 25C, 25K), developing means (26Y, 26M, 26C, 26K), intermediate transfer member 27, transfer roller 28, cleaning means 29, fixing device 30, spectral colorimeter 41, 42, etc. Prepare.

  Next, the operation of the color image forming apparatus shown in FIGS. This operation is comprehensively controlled by the main control unit 120. The image forming unit 100 forms an electrostatic latent image by irradiating the charged photosensitive drum with exposure light by the writing optical system 24 based on the exposure time converted by the image processing unit 130. Is developed to form a single color toner image, the single color toner images are superimposed to form a multicolor toner image, the multicolor toner image is transferred to the recording material 11, and the multicolor toner image on the recording material 11 is transferred. Is fixed by the action of heat and pressure.

  In FIG. 2, photosensitive drums 22Y, 22M, 22C, and 22K are configured by applying an organic photoconductive layer to the outer periphery of an aluminum cylinder, and rotate by receiving a driving force of a driving motor (not shown). Rotates the photoconductive drums 22Y, 22M, 22C, and 22K in the counterclockwise direction according to the image forming operation.

  As primary charging means, four chargers 23Y, 23M, 23C, and 23K for charging the photosensitive drums of yellow (Y), magenta (M), cyan (C), and black (K) are provided for each station. In configuration, each charger is provided with a sleeve 23YS, 23MS, 23CS, 23KS.

  Exposure light to the photosensitive drums 22Y, 22M, 22C, and 22K is sent from the writing optical systems 24Y, 24M, 24C, and 24K, and selectively exposes the surfaces of the photosensitive drums 22Y, 22M, 22C, and 22K. The electrostatic latent image is formed.

  As developing means, in order to visualize the electrostatic latent image, four developing units 26Y, 26M for developing yellow (Y), magenta (M), cyan (C), and black (K) for each station, Each developing device is provided with a sleeve 26YS, 26MS, 26CS, and 26KS. Each developing device is detachably attached.

  The intermediate transfer member 27 is in contact with the photosensitive drums 22Y, 22M, 22C, and 22K, and rotates in the clockwise direction when forming a color image, and rotates with the rotation of the photosensitive drums 22Y, 22M, 22C, and 22K. A single color toner image is transferred. Thereafter, a transfer roller 28 (to be described later) comes into contact with the intermediate transfer member 27 to sandwich and convey the recording material 11, and the multicolor toner image on the intermediate transfer member 27 is transferred to the recording material 11.

  The transfer roller 28 contacts the recording material 11 at the position 28a while transferring the multicolor toner image onto the recording material 11, and is separated to the position 28b after the printing process.

  The fixing device 30 melts and fixes the transferred multi-color toner image while conveying the recording material 11. As shown in FIGS. 1 and 2, the fixing device 30 includes a fixing roller 31 that heats the recording material 11 and the recording material 11. A pressure roller 32 for press-contacting the fixing roller 31 and thermistors (thermometers) 35a and 35b are arranged on the surfaces of these rollers in a state where they are in contact with each other with a slight pressure. Further, the fixing temperature at that time is successively monitored by the thermistor 35, and the recording material conveyance speed is successively monitored by a speedometer (not shown). Although the number of thermistors is two, a plurality of thermistors may be arranged for reasons such as device configuration and accuracy improvement. The monitored temperature value is fed back to the fixing condition control unit 110.

  The recording material 11 after the toner image is fixed is discharged to a discharge tray (not shown) by a discharge roller 81, and the image forming operation is completed. The cleaning unit 29 cleans the toner remaining on the intermediate transfer member 27. Waste toner after the four color toner images formed on the intermediate transfer member 27 are transferred to the recording material 11 is removed from the cleaner container. Stored in

  Next, with reference to FIG. 1, the outline of the control operation of the fixing conditions in the image forming apparatus will be described. The image forming apparatus includes an image processing condition, a memory for storing patch images, an image processing unit 130 including an IC for performing image processing, a fixing condition control unit 110 for storing and controlling fixing conditions, and a created patch. A surface diffused light acquisition unit 160 that acquires surface diffused light from an image is included. Here, a transparent film (OHP sheet) is used as the recording material (the reason will be described later). As described above, the toner image is transferred to and fixed on the OHP sheet, the reflection characteristics of the patch image after fixing are measured by the spectrocolorimeters 41 and 42, and the measured value is input to the surface diffused light calculation unit 150. Input and calculate surface diffused light. Subsequently, the fixing condition control unit 110 controls the fixing conditions according to the information from the surface diffused light calculation unit 150.

  The surface diffused light calculation unit 150 inputs measurement values from the spectrocolorimeters 41 and 42 that measure the spectral reflectances 1 (Rf) and 2 (Rb) for the image fixed on the OHP sheet, and calculates the calculation unit 152. The difference value (Rf−Rb) between the spectral reflectance 1 (Rf) and the spectral reflectance 2 (Rb) input in step S4 is calculated, and the conversion between Rf−Rb and surface diffused light stored in advance in the memory 151 is performed. The surface diffused light is calculated with reference to the equation or the conversion table (the measurement principle will be described later).

  The spectrocolorimeters 41 and 42 are arranged downstream of the fixing device 30 in the recording material conveyance path toward the image forming surface of the recording material 11 (OHP sheet) and the back surface thereof, and are formed on the recording material 11. Spectral reflectances 1 and 2 are detected for the fixed image. By arranging the spectrocolorimeters 41 and 42 inside the color image forming apparatus, it becomes possible to automatically detect the fixed image before discharging it to the paper discharge unit.

  FIG. 3A shows a configuration example of the spectrocolorimeters 41 and 42. The spectrocolorimeters 41 and 42 include a light source 51 such as a halogen lamp, a lens 52 for shaping a collimator lens, a spectroscopic element 54 such as a slit 53 and a concave diffraction grating, a light receiving element 55 such as a C-MOS sensor, and a light trap 56. In addition, it is configured by an IC (not shown) that processes received light data.

  The light source 51 and the lens 52 are arranged on a straight line perpendicular to the surface of the recording material 11 and irradiate the recording material 11 with light perpendicularly. The slit 53 and the spectroscopic element 54 are arranged in a direction of 45 ° with respect to the direction perpendicular to the recording material surface. Of the reflected light from the measurement object, the light reflected in the 45 ° direction passes through the slit 53 and then is split. The light is dispersed by the element 54 and received by the light receiving element 55. The light trap 56 is installed on the side opposite to the incident direction, and absorbs light transmitted through the recording material 11. In the embodiment, 0/45 ° (0 ° incidence, 45 ° light reception) is used, but an integrating sphere such as 0 / d (SCE) may be used as described above. Further, from the measurement principle described later, since the measurement optical system can measure either a black back or a white back, a white plate or the like may be used instead of the light trap 56.

  As described above, the spectral reflectances 1 and 2 are measured by the spectral colorimeters 41 and 42 with respect to the toner image fixed on the recording material 11 (OHP sheet) and sent to the calculation unit 152. The calculation unit 152 calculates a difference value Rf−Rb between the transmitted spectral reflectances 1 (Rf) and 2 (Rb), and at the same time, from the memory 152, as shown in FIGS. 8A and 8B described later. A surface diffusion is obtained by reading a conversion formula (FIG. 8A) or a conversion table (FIG. 8B) between the Rf-Rb and the surface diffused light and converting the calculated Rf-Rb into the surface diffused light. Calculate the light. Then, the calculated surface diffused light is compared with the upper limit value of the surface diffused light stored in the memory 152 in advance. If the surface diffused light exceeds the upper limit value, the surface diffused light or the difference value from the upper limit value is fixed. This is sent to the condition control unit 110. The fixing condition control unit 110 controls the fixing conditions based on the sent data.

  The principle of acquiring surface diffused light will be described with reference to FIG. FIG. 4 shows that the surface of the toner image formed on the transparent film (OHP sheet) is irradiated with light perpendicularly and the light is reflected (FIG. 4 (a)), contrary to (a), the OHP sheet. FIG. 4B shows a state in which light is vertically irradiated on the back surface of the light and reflected. Further, a light trap (not shown) is installed on the side opposite to the light incident side, and the light that has passed through the OHP sheet is not reflected to the incident light side (black back). At this time, if the light is received in the 45 ° direction, the reflected light Rf to be measured is reflected light (surface diffused light) S1 from the toner layer surface and backscattered from the inside of the toner layer, as shown in FIG. It consists of the light Sb1 and So1 that combines the reflected light from the interface of the OHP sheet and the scattered light from the inside. Similarly, as shown in FIG. 4B, the reflected light Rb to be measured is reflected light (surface diffused light) S2 from the toner layer surface, backscattered light Sb2 from the inside of the toner layer, and the OHP sheet. It consists of So2 that combines the reflected light from the interface and the scattered light from the inside. Further, the transmittances of the toner layer and the OHP sheet are represented by T and To, respectively.

  Comparing each value of the reflected light to be measured, (1) Backscattering Sb1 and Sb2 inside the toner layer are substantially equal. (2) Since the reflected light So1 (a) from the OHP sheet passes through the toner layer, the transmittance T of the toner layer is applied. On the other hand, So2 (b) is not attenuated by the toner layer. Considering the light in the absorption band of the toner layer now, So1 is significantly attenuated by the toner layer, so it is much smaller than So2. (3) Since the surface diffused light S2 (b) passes through the inside of the toner layer as in the case of (2), it is greatly attenuated. Accordingly, S2 is much smaller than S1.

  Therefore, the magnitude relationship as shown in FIG. 4 (c) is established for Sb, So, and S, and if the difference between the two is taken, (1) Sb is canceled and (2) So is only So2 as a constant term. (3) Only S1 remains in S. As a result, the difference value between the reflected light Rf and the reflected light Rb is Rf−Rb = S1 + (constant).

  The above results can be obtained even when paper or a white plate is installed on the side opposite to the light incident side (white back). FIG. 5 shows a case where paper is placed on the side opposite to the incident side in FIG. At this time, similarly to FIG. 4, when the reflected lights Rf and Rb received in the 45 ° direction are considered, the reflected lights Rp1 and Rp2 from the paper are further included as compared with the case of FIG. 4 (black back). Since the reflected light Rp1 and Rp2 pass through the toner layer and the OHP layer, Rp1 and Rp2 are substantially equal, and the other components of the reflected light are the same as those in FIG. 4, so the difference between the reflected light Rf and Rb. Since the values Rf-Rb cancel out Rp1 and Rp2, the same result as in FIG. 4 (blackback) is obtained.

FIG. 8C shows the relationship between Rf-Rb and surface diffused light. As shown in FIG. 8C, Rf-Rb and the surface diffused light have a linear relationship. Thereby, surface diffused light can be acquired in the following procedures using an OHP sheet.
(A) The reflected light is measured with a 0/45 ° optical system on the front side of the toner image formed on the OHP sheet (measurement result; Rf).
(B) From the back side of the OHP sheet, the reflected light is measured with the same optical system (measurement result; Rb).
(C) A difference value Rf−Rb between the two is calculated.
(D) Using the relational expression (or conversion table) between Rf-Rb and surface diffused light as shown in FIGS. 8A and 8C, surface diffused light is obtained from Rf-Rb. The above procedure is established for both blackback and whiteback.

  FIG. 6 is a flowchart of the fixing condition control operation according to the first embodiment. The fixing condition control operation is to form a patch image on an OHP and control the fixing condition using the image after fixing, and is controlled by the main control unit 120 and the fixing condition control unit 110.

  First, the patch image is transferred to a recording material (OHP sheet) (step S1) and fixed on the recording material (step S2). Subsequently, the spectral reflectance 1 (Rf) is measured from the front side of the fixed patch image (step S3), and then the spectral reflectance 2 (Rb) is measured from the back side (step S4). Then, a difference value between Rf and Rb is calculated, and surface diffused light corresponding to the difference value is obtained using a conversion formula or a conversion table (step S5).

  Subsequently, it is determined whether or not the acquired surface diffused light is not more than an upper limit value (step S6). When the surface diffused light is equal to or less than the upper limit value, a series of this process is terminated. On the other hand, if the surface diffused light is not less than or equal to the upper limit value, it is further determined whether there is room for control of fixing conditions (step S7). If there is room for control of fixing conditions, the fixing conditions are controlled (step S8). ), The process returns to step S1, and the above-described operation is repeated.

  As described above, the operation for controlling the fixing condition based on the acquired surface diffused light is started upon receiving a request for controlling the fixing condition from the user, or when a predetermined number of sheets are printed, the fixing condition control is automatically performed. May start. Further, the fixing condition control may be started at the time of fixing adjustment at the time of shipment from the factory, at the time of maintenance and inspection by a service person (particularly when the fixing device and the roller are replaced), and the like. Further, the control (setting) of the fixing condition may be performed by an instruction from the operation display unit 140 or a special operation by a service person having a specific technique.

  In steps S1 and S2, control patch data is sent from the storage unit 112 to the image processing unit 130, a patch is formed on the OHP sheet, and the toner is heated and fixed by the fixing device 30. Here, the fixing conditions used for heat fixing are the latest fixing conditions stored in the storage unit 112.

  FIG. 7A shows an example of a patch image that is heat-fixed on the OHP sheet. In FIG. 7A, patches each having a C, M, Y, and K monochrome area ratio of 100% are arranged in a line in the OHP sheet conveyance direction. The reason why a patch with an area ratio of 100% is used is that a patch with an area ratio of 100% is optimal for confirming a change in fixability. Of course, instead of a single color, a patch with an area ratio of 100% for secondary colors such as R, G, and B may be used. Further, the reason why they are arranged in a line in the OHP sheet conveyance direction is to consider a case where the fixing device 30 has fixing unevenness in a direction (main scanning direction) perpendicular to the OHP sheet conveyance direction. . In FIG. 7A, one patch is arranged for each color. However, in order to improve the measurement accuracy, a plurality of patches of the same color are arranged, surface diffused light is obtained for each patch by a method described later, and the average is obtained. It may be taken.

  In step S <b> 3 of FIG. 6, the spectral reflectance 1 (Rf) is measured by the spectrocolorimeter 41 for each color patch heat-fixed on the OHP sheet. In step S4, as in step S3, the spectral reflectance 2 (Rb) is measured by the spectrocolorimeter 42 from the back side of the OHP sheet for each color patch heat-fixed on the OHP sheet. In step S <b> 5, the calculation unit 152 calculates a difference Rf−Rb between the spectral reflectance 1 and the spectral reflectance 2. Then, the surface diffusion light corresponding to the calculated Rf-Rb is calculated with reference to the conversion formula or conversion table of Rf-Rb and surface diffusion light stored in advance in the memory 151. In step S6, the calculated surface diffused light is compared with the upper limit value of the surface diffused light stored in advance in the memory 151 for each color. As a result of the comparison, if the surface diffused light is less than or equal to the upper limit value, the series of processes in FIG. 6 is terminated, and if the surface diffused light is not less than or equal to the upper limit value, the surface diffused light and the upper limit value, or the difference value thereof, It is sent to the fixing condition control unit 110.

  FIGS. 8A and 8B show a conversion formula (a) or a conversion table (b) between Rf-Rb and surface diffused light read from the memory in step S5 of FIG. As shown in FIG. 8A, a conversion equation for converting Rf-Rb into surface diffused light is used. Alternatively, as shown in FIG. 8B, numerical values are held in a table format, and Rf-Rb is converted into surface diffused light using the numerical values.

  FIG. 9A is an example of a data table read from the memory in step S6 of FIG. The data table in FIG. 9A includes the type of the OHP sheet and the upper limit value of the surface diffused light of each color of C, M, Y, and K.

  As described above, Rf−Rb is calculated using the absorption band of each color in the spectral data. However, considering the conversion into surface diffused light in step S5 and the comparison with the upper limit value in step S6, when calculating Rf-Rb in step S5, a method using a value at a certain wavelength in the absorption band, A method of taking an average value in the absorption band can be considered. By setting the spectral data to a single value, it is possible to facilitate subsequent conversion to surface diffused light and comparison with the upper limit value. Of course, the surface diffused light may be calculated for each wavelength and then averaged, or the upper limit value of the surface diffused light stored in the memory 151 may be stored as spectral data in the absorption band and compared for each wavelength. The results may be summarized to determine whether or not the surface diffused light is below the upper limit value.

  In steps S7 and S8 in FIG. 6, the fixing conditions are controlled based on the sent data. First, in step S7, it is determined whether there is room for control in the fixing conditions (usually, it is determined that there is room in the first cycle). Here, there is room for control in the fixing conditions means that the surface diffused light can be further reduced by appropriately controlling the fixing conditions. If it is determined that there is room for control, the fixing conditions are controlled in step S8. Then, after updating the fixing condition stored in the storage unit 112 to the latest value, the process returns to step S1 and the control flow is executed again.

  Hereinafter, specific examples of the fixing condition control in steps S7 and S8 will be described. The aim of fixing condition control is to reduce the surface diffused light and keep it below the upper limit. Examples of the fixing conditions to be controlled include a fixing temperature, a nip pressure, and a recording material conveyance speed. Here, the nip pressure and the conveyance speed are constant, and the fixing temperature, which is the surface temperature of the fixing roller 31 and the pressure roller 32 detected by the thermistors 35a and 35b, is considered as a control target.

  FIG. 10A shows the change of the surface diffused light with respect to the fixing temperature. As shown in the figure, the surface diffused light has a downwardly convex curve with respect to the fixing temperature. The reason is that in the region where the fixing temperature is low, the toner is not sufficiently melted and a lot of irregularities remain on the surface, so that the surface diffused light becomes large. As the fixing temperature is raised, the toner is sufficiently melted, surface irregularities are reduced, and surface diffused light is reduced. However, if the fixing temperature is raised above a certain level, this time, hot offset begins to occur, peeling occurs on the toner surface, resulting in unevenness, resulting in an increase in surface diffused light. Therefore, in order to reduce the surface diffused light, the fixing temperature may be controlled so as to approach the minimum point of the curve in FIG.

  The significance of determining whether there is room for control in the fixing conditions in step S7 in FIG. 6 will be described. Even if the fixing property deteriorates due to aging of each component constituting the fixing device 30 and the surface diffused light is made as small as possible by the method described later (even if the minimum point in FIG. 10A is reached), A case where the value of the surface diffused light exceeds the upper limit value of the surface diffused light stored in the memory 151 can be considered. Step S7 is a processing step considering such a case. Even if it is determined in step S6 that the surface diffused light exceeds the upper limit value, if it is determined in step S7 that the surface diffused light has reached the minimum point, step S7 is performed. Then, the control flow of the fixing conditions in FIG. 6 ends.

  As described above, the control of the fixing temperature is to control the fixing temperature so as to approach the minimum point in FIG. 10A. However, since the fixing roller 31 and the pressure roller 32 are deteriorated with age, the fixing temperature is controlled. However, the value of the surface diffused light is not always the same. Further, the fixing temperature measured by the thermistors 35a and 35b cannot always be measured in the same manner, and the measured value varies from time to time. Therefore, the curve in FIG. 10A is only relative and fluctuates from time to time. That is, controlling the fixing temperature means bringing the temperature close to the temperature corresponding to the minimum point in FIG. Therefore, for example, it is meaningless to store the temperature of the minimum point in FIG. 10A in advance and control the fixing temperature using the temperature as a target value. It is necessary to determine and control the current position with respect to the minimum point in (a).

  Hereinafter, an example of the fixing temperature control method will be described. First, considering that the rough characteristics (such as the magnitude of the differential coefficient) of the curve in FIG. 10A do not change, a predetermined temperature ΔT to be changed at the time of fixing temperature control is stored in the storage unit 112 in advance. Then, a patch image is output under the latest fixing conditions (fixing temperature) once stored in the storage unit 112, surface diffusion light is measured, and the measured surface diffusion light is temporarily stored in the storage unit 112. . If the surface diffused light exceeds the upper limit value in step S6 of FIG. 6, the fixing temperature is changed by ΔT, the process returns to step S1, a patch image is output again, and the surface diffused light is measured. Then, the measured surface diffused light and the surface diffused light in the immediately preceding cycle stored in the storage unit 112 are compared. If the surface diffused light is reduced at this time, it can be seen that the minimum point in FIG. 10A has been approached, so the fixing temperature may be controlled in that direction. On the other hand, if the surface diffused light is increased, it can be seen that the surface diffused away from the minimum point, and thus the fixing temperature may be controlled in the opposite direction. In this way, the relative position at the present time with respect to the minimum point in FIG. 10A, that is, the direction for controlling the fixing temperature is obtained, and the above cycle is repeated until the surface diffused light becomes sufficiently small, that is, in the memory 151. What is necessary is just to repeat until it falls below the memorize | stored upper limit or reaches the minimum point in Fig.10 (a).

  The predetermined temperature ΔT is a temperature that is neither excessive nor excessive. In other words, once the fixing temperature is changed by ΔT, ΔT is too large to jump over the minimum point. On the other hand, if ΔT is too small, the fixing condition control flow is repeated many times. The cycle must be repeated, wasting time and money. ΔT is desirably large when the fixing temperature is far from the minimum point, and is small when close to the minimum point. Therefore, this ΔT may be input manually, for example, by a serviceman every time the control flow cycle shown in FIG. 6 is performed, and in the case of automatic control, an optimal control method for this ΔT is selected in advance. It is desirable to store in the storage unit 112.

  When the surface diffused light always exceeds the upper limit value of the surface diffused light stored in the memory 151 due to deterioration of the fixing device 30 or the like (in step S7, it is determined that there is no room for control in the fixing condition). In other words, a method of updating the upper limit value of the surface diffused light stored in the memory 151 to a value at the minimum point in FIG. As a result, when the surface diffused light always exceeds the upper limit value (before update), when the update is not performed, it is performed every time the fixing condition control flow is started. It is possible to omit the cycle of searching for the minimum point in FIG. This is because if the upper limit value of the surface diffused light is updated, it is determined that the surface diffused light is below the upper limit in step S6 when the flow of FIG. It is. By doing this, it is possible to avoid wasting time and costs by outputting the patch image many times in vain.

  In the above description, the fixing temperature is used as the fixing condition. However, other fixing conditions such as the conveyance speed of the recording material may be used as the control factor. FIG. 10B shows the relationship between the conveyance speed and the surface diffused light. However, FIG. 10B shows the case where the fixing temperature is a value at which the surface diffused light becomes sufficiently small. At this time, the relationship between the conveyance speed and the surface diffused light draws a downwardly convex curve as in FIG. The reason is that when the conveyance speed is low, heat is excessively conducted to the toner image, so that hot offset occurs and the surface diffused light becomes large. As the conveying speed is increased, the heat transmitted to the toner image is reduced, the hot offset is eliminated, and the surface diffused light is reduced. When the conveyance speed is further increased, the heat is not sufficiently transferred to the toner image and the surface is not sufficiently melted, so that the surface diffused light becomes large. Therefore, even if the control factor is changed to the conveyance speed, it is possible to control the surface diffused light in the same manner as at the fixing temperature. Further, after the fixing temperature is controlled, a method of additionally controlling the conveyance speed may be employed. Thereby, surface diffused light can be controlled more appropriately.

  According to the present invention, the surface diffused light can be obtained by measuring the surface diffused light from the front and back sides of the transparent film, while offsetting the fluctuation of the pigment scattering component due to the fluctuation of the toner adhesion amount. Based on the surface diffused light, fixing conditions in the OHP mode can be controlled.

  According to the present invention, the surface diffused light corresponding to the difference value between the reflection characteristics 1 and 2 can be calculated using the conversion table stored in the storage unit.

  According to the present invention, surface diffused light can be obtained by using spectral reflectance as the reflection characteristics 1 and 2.

  According to the present invention, it is possible to detect an increase in surface diffused light due to aging of the apparatus and the like, and control to reduce the surface diffused light.

  According to the present invention, surface diffused light can be obtained by using the same optical system as the measuring means 1 and 2.

  According to the present invention, by using a 0/45 ° optical system as a measurement optical system, it is possible to obtain surface diffused light that can be directly incorporated into color evaluation.

  In Example 1, the spectrocolorimeter 41 is disposed on the image forming surface side of the toner image formed on the OHP sheet, and the spectrocolorimeter 42 is disposed on the back side of the image forming surface of the toner image. The spectral reflectances 1 and 2 were measured. However, since the spectrocolorimeter is not cheap, the cost can be reduced if the spectral reflectances 1 and 2 can be measured with a single spectrocolorimeter.

  Therefore, Example 2 shows an example in which an OHP sheet is reversed using a single spectrocolorimeter.

  FIG. 11 shows a system configuration of the second embodiment. FIG. 11 shows a configuration in which the spectrocolorimeter 42 is removed from FIG. FIG. 12 shows the configuration of the image forming unit in FIG. The difference from the first embodiment (FIG. 2) is that the spectrocolorimeter 42 is removed and transport paths R2 and R3, path switching claws 71 and 72, and a transport roller 83 are added.

  The operation of the color image forming apparatus of FIGS. 11 and 12 is the same as that of FIG. The outline of the control operation of the fixing conditions in the image forming apparatus of the second embodiment is almost the same as that of the first embodiment (FIG. 1). However, in Example 2, the spectral reflectances 1 and 2 are measured by the spectral colorimeter 41. Further, the spectral reflectances 1 and 2 are sent from the spectral colorimeter 41 to the calculation unit 152, and the calculation unit 152 calculates the surface diffused light using the sent data.

  The movement of the recording material 11 (OHP sheet) and the colorimetry procedure in Example 2 will be described. In the recording material 11, the toner image is transferred by the transfer belt 27 through the conveyance path R 1, heated and fixed by the fixing device 30, and the spectral reflectance 1 is measured by the spectrocolorimeter 41. Thereafter, the recording material 11 is moved to the conveyance path R3 by the path switching claws 71 and 72a, and then moved to the conveyance path R2 by the path switching claw 72b, and the conveyance roller 83 is rotated in the reverse direction. In this state, it is returned to the transport path R1. Then, the spectral reflectance 2 of the recording material 11 turned upside down is measured by the spectrocolorimeter 41. Thereafter, the recording material 11 is discharged to the paper discharge unit by the conveying rollers 81 and 82.

  As described above, the spectral reflectances 1 and 2 are measured using the spectrocolorimeter 41. Note that the fixing condition control procedure in the second embodiment is the same as that in the first embodiment (FIG. 6).

  In Examples 1 and 2, spectral reflectance was used as the reflection characteristics 1 and 2, and a spectrocolorimeter was used as the measuring means. In Example 3, as the reflection characteristics 1 and 2, the reflectance when using a single wavelength or narrow band light (red light) is measured to obtain surface diffused light. is there. The configuration of the image forming apparatus according to the third embodiment can be applied to both the first and second embodiments, but the second embodiment is applied here. In the third embodiment, red single-wavelength light or narrow-band light is used. As described later, single-wavelength light other than red light or narrow-band light (for example, blue light and green light) is used. Also good.

  FIG. 13 shows a system configuration of the third embodiment. FIG. 13 shows a configuration in which the spectrocolorimeter 41 of Example 2 (FIG. 11) is configured in place of the reflectance measuring instrument 43 using single wavelength light, and other components are the same as those in FIG. . FIG. 14 is a diagram in which the spectrocolorimeter 41 in the configuration of the second embodiment (FIG. 12) is configured in place of the reflectance measuring device 43 using single wavelength light.

  FIG. 3B shows the configuration of the reflectometer 43 using single wavelength light. The reflectance measuring instrument 43 includes a single-wavelength or narrow-band red light source 61 such as a red diode, a light receiving element 62 such as a photodiode, a light trap 63, and an IC (not shown) that processes received light data.

  The light source 61 is installed perpendicular to the recording material 11 and irradiates light perpendicularly to the recording material 11. The light receiving element 62 is installed in a 45 ° direction with respect to the vertical direction of the recording material 11, and detects reflected light from the recording material 11. As in the first and second embodiments, the light trap 63 may be replaced with a white plate.

  The procedure of fixing condition control in the third embodiment is the same as that in the first and second embodiments (FIG. 6). However, unlike the first and second embodiments, the patch image created in step S1 and the table of upper limit values of surface diffused light read from the memory 151 in step S6 are single-color patches and tables.

  FIG. 7B is a patch image created in the third embodiment. In Example 3, since single wavelength light (or narrow band light) is used, a single color is also used for the patch image. As described above, since the reflected light measuring device 43 uses red light as a light source, cyan is used for a patch image. The reason for this combination is that the cyan absorption band is the red light band.

  In Example 1, the measurement principle of the present invention described with reference to FIGS. 4 and 5 is established in the toner absorption band. In other words, this means that the present invention can be implemented only by using a light source having a wavelength band in the absorption band of the created toner image. Therefore, although the cyan patch and the red light source are used in this embodiment, the combination of the toner and the light source is not limited to this as long as the light source has a wavelength in the toner absorption band.

  FIG. 9B shows the upper limit value of the surface diffused light stored in the memory 151. As described above, since cyan is used for the patch image, the upper limit value of the surface diffused light may be only the cyan value.

  According to the present invention, surface diffused light can be obtained with a simpler apparatus by using the reflectance of light of a single wavelength or narrow band as the reflection characteristics 1 and 2.

  In Examples 1 to 3, the reflection characteristics 1 and 2 were measured to obtain Rf-Rb, and the surface diffused light was calculated using a conversion formula (or conversion table) with the surface diffused light. Further, as shown in FIGS. 8A and 8C, since Rf-Rb and the surface diffused light have a linear relationship, controlling the fixing condition directly using Rf-Rb is effective for controlling the surface diffused light. It is synonymous with acquiring and controlling fixing conditions.

  Therefore, in this embodiment, a method for controlling fixing conditions using Rf-Rb instead of surface diffused light is shown. As the configuration of the image forming apparatus in the present embodiment, any of the above-described first to third embodiments can be applied, but here, the second embodiment is applied.

  FIG. 15 is a flowchart of fixing condition control according to the fourth embodiment. In FIG. 15, steps 15 and 16 are different from the processing of FIG. In step S15, Rf-Rb is calculated. In step S16, Rf-Rb calculated in step S15 is compared with the upper limit value of Rf-Rb stored in the memory 151 in advance. In steps S17 and S18, fixing conditions are controlled using Rf-Rb as a control target.

  FIG. 9C shows the upper limit value of Rf−Rb stored in advance in the memory 151. In step S16, it is determined whether or not Rf−Rb is equal to or lower than the upper limit value with reference to the upper limit value. FIG. 10C shows the relationship between the fixing temperature and Rf−Rb. As shown in FIG. 10C, the relationship between Rf-Rb and the fixing temperature is the same as the relationship between the surface diffused light and the fixing temperature shown in FIG. The method for controlling the surface diffused light of Examples 1 to 3 can be applied.

  According to the present invention, the fixing conditions can be controlled more easily by controlling the fixing conditions using the difference values of the reflection characteristics 1 and 2 instead of the surface diffused light.

  In Examples 1 to 4, when surface diffusion light (or Rf-Rb) is acquired and the fixing conditions are controlled, even if the toner adhesion amount fluctuates, FIGS. 9A, 9B, and 9C are used. The upper limit value of the surface diffused light (or Rf-Rb) shown is constant. However, as shown in FIG. 16A, the surface diffused light changes according to the amount of toner attached. That is, if the toner adhesion amount is different, the optimum surface diffused light is also different.

  Therefore, in this embodiment, when a toner image is formed, the toner adhesion amount of the formed toner image is measured, and the fixing condition is controlled according to the optimum value (target value) of the surface diffused light according to the measurement result. An example is shown. Although any of the first to fourth embodiments can be applied to the present embodiment, the second embodiment is applied here.

  FIG. 17 shows a system configuration of the fifth embodiment. FIG. 17 is configured by adding a densitometer 44 (before the fixing device 30) to the configuration of the second embodiment (FIG. 11). Other components are the same as those in FIG.

  FIG. 18 shows the configuration of the image forming unit of FIG. The densitometer 44 is installed on the front side of the fixing device 30 with respect to the recording material conveyance direction, whereby the density of the toner image on the recording material 11 before fixing can be measured. As a method of estimating the toner adhesion amount from the image density before fixing, for example, there is a method described in Patent Document 3.

  As a specific method for obtaining the adhesion amount from the density, after detecting the density of the image before fixing, for example, a conversion table of density and adhesion amount as shown in FIG. 16B is stored in the storage medium (memory 151) in advance. The amount of adhesion can be calculated using the conversion table.

  FIG. 3C shows the configuration of the densitometer 44. The densitometer 44 includes a light source 71 such as a gas-filled filament lamp, a light receiving element 72 such as a photodiode, an IC (not shown) that processes received light data, and the like.

  The light source 71 is installed perpendicular to the recording material 11 and irradiates light onto the recording material 11 perpendicularly. The light receiving element 72 is installed in a 45 ° direction with respect to the vertical direction of the recording material 11 and detects reflected light from the recording material 11.

  FIG. 19 is a flowchart of the fixing condition control operation according to the fifth embodiment. In FIG. 19, step S22 (step of detecting the image density before fixing and estimating the adhesion amount) is added to the flowchart of FIG. Other processes are the same as those in FIG.

  The patch image is transferred onto the recording material 11 (OHP sheet) (step S21), the density is detected, and the toner adhesion amount is estimated (step S22). The toner image is fixed on the OHP sheet (step S23), the reflection characteristics 1 and 2 are detected (steps S24 and S25), and the surface diffused light is calculated (step S26). The upper limit value of the surface diffused light corresponding to the toner adhesion amount estimated in step S22 is read and compared with the calculated surface diffused light (step S27). At this time, if the surface diffused light is not more than the upper limit value, a series of control operations are finished, and if the surface diffused light is not less than the upper limit value in step S27, it is determined whether there is room for further fixing condition control. (Step S28) If it is determined that there is room, the fixing conditions are controlled, and the process returns to Step S21. The above operation is repeated until the surface diffused light becomes sufficiently small.

  FIG. 16B is a conversion table for estimating the toner adhesion amount from the density detected in step S22 and is stored in the memory 151 in advance. In step S22, after the density is detected, this table is read from the memory, and the detected density is converted into a toner adhesion amount using this table.

  FIG. 9D is a table that stores the upper limit value (target value) of the surface diffused light, which is stored in advance in the memory 151. The upper limit value of the surface diffused light maintains a value for each adhesion amount. In step S27, when determining whether or not the calculated surface diffused light is equal to or lower than the upper limit value, the upper limit value of the surface diffused light corresponding to the toner adhesion amount estimated in step S22 is read from the table (see above). If the upper limit value for the estimated toner adhesion amount is not included in the table, it may be interpolated using a value near the adhesion amount) and compared with the calculated surface diffused light. In this way, the surface diffused light can be controlled according to the target value (upper limit value) corresponding to the toner adhesion amount.

  According to the present invention, the toner adhesion amount of the toner image transferred to the recording material can be acquired, and can be controlled to an appropriate value according to the adhesion amount acquired surface diffusion light.

  According to the present invention, it is possible to acquire the adhesion amount by converting the density using the adhesion amount conversion table that detects the density of the toner image transferred to the recording material and converts the detected density into the adhesion amount.

  Examples 1 to 5 are examples in which surface diffused light (or Rf-Rb) is obtained using an OHP sheet, and fixing conditions such as a fixing temperature are controlled based on the result. As described above, in general, an image forming apparatus sets different fixing condition modes for an OHP sheet and plain paper. In Examples 1 to 5, an OHP sheet is used and suitable for the OHP mode, but other modes such as the plain paper mode cannot be directly controlled.

  Therefore, in this embodiment, an embodiment in which the fixing condition in the plain paper mode is indirectly controlled based on the surface diffused light measured using the OHP sheet is shown. The configuration of the image forming apparatus of the present embodiment can be applied to any of the first to fifth embodiments, but the fifth embodiment is applied here.

  FIG. 20 shows changes in surface diffused light with respect to fixing temperature. Surface diffused light measured using an OHP sheet in the OHP mode (hereinafter referred to as OHPonOHP mode) and surface diffused light measured using plain paper in the plain paper mode. (Hereinafter referred to as plain paper on plain paper mode). The surface diffused light in the OHPonOHP mode is obtained by the method of Example 5. The surface diffused light in the plain paper on plain paper mode can be measured according to the principle described with reference to FIG.

  FIG. 20 shows a graph of the OHPonOHP mode and a graph of the plain paper on plain paper mode. The positions and shapes of the graphs are different from each other, and the temperatures of the local minimum points are shifted by ΔTlocal-min.

  As described above, the position and shape of the graph are affected by changes in the environment such as the toner adhesion amount, fixing conditions (nip pressure, conveyance speed) other than the fixing temperature, and humidity. Therefore, the deviation of the minimum point is uniquely determined by fixing the toner adhesion amount, the fixing conditions other than the fixing temperature (each value of the plain paper mode and the OHP mode), and the above-mentioned environmental conditions to one. The value can be determined by experiment. For example, as shown in FIG. 21 (b), if the relationship between the set value of each factor and the difference ΔTlocal-min between the minimum points is obtained and stored in advance, the minimum point in the plain paper mode is changed from the minimum point in the OHP mode. The value of is known. When the environment changes, the graph of FIG. 20 is also affected. However, since the influence is common in the OHPonOHP mode and the plain paper on plain paper mode, the influence on the relative positional relationship between the two is small. FIG. 21B does not include environmental factors.

  FIG. 22 is a flowchart illustrating the control operation of the fixing condition (fixing temperature) according to the sixth embodiment. Steps S31 to S36 in FIG. 22 are the same as those in FIG. 19 (Embodiment 5). The toner image is transferred to a recording material (OHP sheet), and the density of the toner image after transfer is measured to obtain the toner adhesion amount. Thereafter, the toner image is fixed and surface diffused light is acquired (steps S31 to S36). The surface diffused light acquired in step S36 is compared with the upper limit value of the surface diffused light stored in advance in the storage unit 112 (step S37). At this time, if the surface diffused light is less than or equal to the upper limit value, it is determined that the apparatus has not deteriorated over time and the same is true in the plain paper mode, and the series of control flows is terminated.

  If the surface diffused light exceeds the upper limit value, it is determined whether or not the minimum point shown in FIG. 20 has been reached (step S38). If it is determined that the minimum point has not been reached, fixing conditions for the OHP mode are determined. Is controlled (step 39), and the process returns to step S31.

  If it is determined that the minimum point has been reached, the fixing condition control in the OHP mode is terminated, and the fixing condition in the plain paper mode is controlled based on the determined fixing condition in the OHP mode (steps S40 to S42). With the above processing, the fixing condition control operation is completed.

  When it is determined in step S38 that the minimum point has been reached, the fixing conditions (fixing temperature) in the plain paper mode are controlled by executing steps S40 to S42. First, the latest OHP mode fixing conditions (TOHP in FIG. 20) set in step S39 are read. Subsequently, as shown in the table of FIG. 21A, the fixing condition (except for the fixing temperature) and the amount of adhesion stored in the storage unit 112 in advance are referred to. Then, ΔTlocal-min is determined by referring to the table of FIG. 21B based on the read TOHP, the fixing condition in the plain paper mode, and the adhesion amount (step S40). Then, the minimum temperature Tpaper in the plain paper mode is obtained by adding ΔTlocal-min to the fixing temperature TOHP in the OHP mode read in advance (step S41). Then, the fixing temperature Tpaper obtained in step S41 is set as the fixing condition in the plain paper mode (step S42). As described above, the fixing condition in the plain paper mode is controlled.

  Note that the graph of FIG. 20 also changes due to aging degradation of the apparatus, but in that case, the shift ΔTlocal-min of the minimum point in both modes may also change. Therefore, an item such as the cumulative number of output devices may be added to the table for obtaining ΔTlocal-min shown in FIG. 21B so that ΔTlocal-min corresponding to the number of output sheets can be obtained.

  The present invention supplies a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and a program in which a computer (CPU or MPU) of the system or apparatus is stored in the storage medium. This is also achieved by reading and executing the code. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments. As a storage medium for supplying the program code, for example, a hard disk, an optical disk, a magneto-optical disk, a nonvolatile memory card, a ROM, or the like can be used. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on an instruction of the program code. A case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included. Further, after the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. This includes the case where the CPU or the like provided in the board or function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing. Further, the program for realizing the functions and the like of the embodiments of the present invention may be provided from a server by communication via a network.

DESCRIPTION OF SYMBOLS 21 Paper feed part 24 Writing optical system 30 Fixing apparatus 31 Fixing roller 32 Pressure roller 33, 34 Heater 35a, b Thermistor 41, 42 Spectrocolorimeter 110 Fixing condition control part 111 Driver 112 Storage part 120 Main control part 130 Image Processing unit 140 Operation display unit 150 Surface diffused light calculation unit 151 Memory 152 Calculation unit 160 Surface diffused light acquisition unit

JP 2006-171104 A JP 2006-267165 A JP 2007-147946 A

Claims (13)

  An image forming unit that forms a patch toner image having an area ratio of 100% and transfers the patch toner image to a recording material, a fixing unit that fixes the toner image transferred to the recording material under predetermined fixing conditions, and the fixed toner An image forming apparatus comprising: surface diffused light acquisition means for obtaining surface diffused light from the surface of an image; and control means for controlling the predetermined fixing condition based on the acquired surface diffused light. The diffused light acquisition means measures the first reflection characteristic from the surface of the toner image formed on the transparent film, and the second reflection characteristic from the back surface of the toner image on the transparent film. An image forming apparatus comprising: a second measuring unit configured to calculate surface diffused light from the first and second reflection characteristics.   The surface diffused light calculating means includes a calculating means for calculating a difference value between the first reflection characteristic and the second reflection characteristic, and a storage means for storing a conversion table between the difference value and the surface diffused light, The image forming apparatus according to claim 1, wherein the surface diffused light calculating unit calculates surface diffused light corresponding to the calculated difference value using a conversion table stored in the storage unit.   The first and second reflection characteristics are spectral reflectances, and the surface diffused light calculation means calculates surface diffused light using the values of the first and second reflection characteristics in the absorption band of the toner image. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the first and second reflection characteristics are reflectances of light having a single wavelength or a narrow band wavelength, and the wavelength range is included in an absorption band of the toner image. .   The control means includes an upper limit value storage means for storing an upper limit value of the surface diffused light, and the surface diffused light acquired by the surface diffused light acquisition means and the surface diffused light stored in the upper limit value storage means. 2. The image forming apparatus according to claim 1, wherein an upper limit value is compared, and fixing conditions are controlled based on the comparison result.   An adhesion amount acquisition means for acquiring a toner adhesion amount of a toner image transferred to the recording material; and an upper limit value storage means for storing an upper limit value of surface diffused light for each toner adhesion amount; With reference to the upper limit value storage means, the upper limit value of the surface diffused light corresponding to the acquired toner adhesion amount is read, and the upper limit value of the surface diffused light and the surface diffused light acquired by the surface diffused light acquiring means The image forming apparatus according to claim 1, wherein the fixing conditions are controlled based on the comparison result.   A density detection unit that detects a density of the toner image transferred to the recording material; and an adhesion amount conversion table that converts the detected density into a toner adhesion amount, and the adhesion amount acquisition unit includes the adhesion amount conversion unit. The image forming apparatus according to claim 6, wherein a toner adhesion amount corresponding to the detected density is acquired with reference to a table.   The image forming apparatus according to claim 1, wherein the control unit controls a fixing condition using a difference value between the first reflection characteristic and the second reflection characteristic instead of the surface diffused light.   2. The image forming apparatus according to claim 1, wherein the first and second measuring units are the same measuring optical system.   The image forming apparatus according to claim 9, wherein the measurement optical system is an optical system that receives light perpendicularly to the recording material surface and receives light in a direction of 45 ° with respect to a direction perpendicular to the recording material surface.   An image forming step of forming a patch toner image having an area ratio of 100% and transferring it to a recording material, a fixing step of fixing the toner image transferred to the recording material under a predetermined fixing condition, and the fixing toner image An image forming method comprising: a surface diffused light acquiring step for obtaining surface diffused light from a surface; and a control step for controlling the predetermined fixing condition based on the acquired surface diffused light, wherein the surface diffused light The acquisition step includes a first measurement step for measuring the first reflection characteristic from the surface of the toner image formed on the transparent film, and a second measurement for measuring the second reflection characteristic from the back surface of the toner image on the transparent film. 2. An image forming method comprising: 2 measuring steps; and a surface diffused light calculating step for calculating surface diffused light from the first and second reflection characteristics.   The program for making a computer implement | achieve the image forming method of Claim 11.   A computer-readable recording medium having recorded thereon a program for causing a computer to implement the image forming method according to claim 11.

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