JP2010282087A - Fixing unit, image forming apparatus, control method for fixing unit, control program and recording medium for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing unit of an outside heat fixing method that prevents damage or deterioration in the fixing unit even when trouble occurs in an outside heating means. <P>SOLUTION: The fixing unit 6 is equipped with a control section for controlling an inside heater lamp 54 and outside heater lamps 74, 75 so that the temperature of a surface of a fixing roller 50 is heated to a first set temperature while performing an image forming job (state of fixing action) and a thermistor 90 for measuring the temperature of the surface of the fixing roller 50 and giving the information of the measured temperature to the control section. In this case, the control section observes the used state of the inside heater lamp 54 and the outside heater lamps 74, 75 of the fixing roller 50 during performance of an image forming job and suppresses the heating of the fixing roller 50 by the inside heater lamp 54 when the used ratio of the inside heater lamp 54 to the outside heater lamps 74, 75 exceeds a prescribed reference value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fixing device used in an electrophotographic image forming apparatus and an image forming apparatus provided with the fixing device.

  Since an electrophotographic image forming apparatus can form high-quality images with good reproducibility and at low cost, it is used as a copying machine, a printer, a facsimile machine, and a multifunction machine having two or more of these functions. The electrophotographic image forming apparatus includes, for example, a photoreceptor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a fixing unit. The photoreceptor is a member on which an electrostatic latent image corresponding to image information is formed. The charging means charges the surface of the photoreceptor. The exposure means irradiates the charged photoreceptor surface with signal light to form an electrostatic latent image. The developing means supplies toner to the electrostatic latent image on the surface of the photoreceptor to form a toner image. The transfer unit transfers the toner image on the surface of the photoreceptor to the recording paper. The fixing unit fixes the toner image on the recording paper to the recording paper to form an image.

  As the fixing means, a fixing device including a fixing roller and a pressure roller is generally used. The fixing roller has a heating means inside, and heats and melts the toner constituting the unfixed toner image on the recording paper to fix it on the recording paper. The pressure roller is provided so as to come into pressure contact with the fixing roller, and promotes fixing of the toner onto the recording paper by pressing the recording paper against the fixing roller when the toner is heated and melted by the fixing roller. The pressure contact portion between the fixing roller and the pressure roller is called a fixing nip portion. The recording paper carrying the unfixed toner image is introduced into the fixing nip so that the toner image carrying surface of the recording paper is in contact with the surface of the fixing roller, and the unfixed toner image is fixed on the recording paper by heating and pressing. .

  By the way, in the image formation of a color image, the amount of toner used per unit area on the recording paper is about 2 to 3 times that in the case of a general black and white image. Therefore, in order to obtain a good color-fixed image by sufficiently melting the toner, in the color fixing device, the fixing roller is fixed by increasing the outer diameter of the fixing roller or by thickening the rubber layer formed on the surface of the fixing roller. Increasing the width of the nip is performed.

  However, increasing the outer shape of the fixing roller or increasing the thickness of the rubber layer formed on the surface of the fixing roller increases the heat capacity of the fixing roller. When such a fixing roller having a large heat capacity is heated only by the heating means provided inside the fixing roller, the fixing performance is improved due to the problem that the start-up time becomes long and the temperature followability of the fixing roller during continuous fixing is reduced. The problem of decreasing occurs. In order to solve these problems, a configuration has been proposed in which a heating unit is disposed outside the fixing roller and the fixing roller is heated from the surface of the fixing roller to increase the temperature increase rate of the fixing roller. Patent Document 1 discloses a fixing device of such an external heating fixing method.

JP 2003-149989 A (published on May 21, 2003)

  In the configuration in which the fixing roller is heated from the outside by an external heating device, heat is supplied from the outside to the fixing roller in order to take advantage of the characteristics. However, the surface of the fixing roller is locally heated due to the configuration. I can only do that. For this reason, while the rotation of the fixing roller is stopped, the fixing roller is heated by an internal heat source provided inside the fixing roller to keep the temperature of the fixing roller at a predetermined temperature.

  Further, the internal heat source is used as an auxiliary heating means during execution of the image forming job and during the start-up operation. Usually, a temperature measuring member such as a thermistor for controlling the fixing roller to a predetermined temperature is provided in the vicinity of the surface of the fixing roller, and a heat source provided outside or inside the fixing roller is used based on the temperature measurement result. The surface temperature of the fixing roller is maintained at a predetermined temperature.

  However, in the case where the temperature control is performed using the internal heat source preferentially and the case where the temperature control is performed using the external heat source preferentially, even if the surface temperature of the fixing roller is the same, the cross-sectional direction of the fixing roller (fixing) The temperature distribution in the radial direction of the rollers is very different. When the temperature is controlled mainly using an internal heat source, naturally, the fixing roller core part close to the internal heat source becomes very hot, and the surface of the fixing roller has the lowest temperature.

  On the other hand, when the temperature is controlled mainly using an external heat source, the surface temperature of the fixing roller is the highest, the temperature is lowered toward the inside of the fixing roller, and the temperature of the fixing roller core is lowest.

  As described above, in the external heating and fixing method having the internal heating means and the external heating means, heat can be supplied from the outside of the fixing roller, so that the rubber layer on the surface of the fixing roller can be set thick. On the other hand, when some trouble occurs and the heat supply from the external heat source becomes insufficient, the heat supply from the internal heat source increases to maintain the surface temperature of the fixing roller at a predetermined temperature. As a result, the temperature of the fixing roller core increases to an expected level or more, and the bearing member holding the fixing roller or the resin member around the fixing roller such as the drive gear may be deteriorated or damaged, or the fixing roller core The rubber material may deteriorate at the interface between the gold and the rubber layer or inside the rubber layer, and the fixing roller may eventually be damaged.

  In Patent Document 1, the temperature of the cored bar is measured by a temperature sensor provided in the cored bar of the fixing roller in the external heating fixing method, and the temperature of the fixing roller during printing is controlled using this temperature information. Is disclosed. However, since the cored bar is not a sheet passing area on the surface of the fixing roller, it is impossible to accurately control the sheet passing area of the fixing roller to a predetermined temperature based on the detected temperature of the cored bar. . In addition, if a temperature sensor for detecting the temperature of the sheet passing area of the fixing roller is separately provided, there arises a problem that the fixing device becomes large and the cost is increased.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to prevent damage or deterioration of a fixing device even when some abnormality occurs and heating by an external heating unit is not performed normally. It is to realize a fixing device of an external heating fixing method.

  The fixing device according to the present invention includes a fixing member, a pressure member pressed against the surface of the fixing member, an internal heating unit that heats the fixing member from the inside, and an external that heats the surface of the fixing member from the outside. Heating means, and having a standby state and a fixing operation state for a fixing operation. In the fixing operation state, the recording material is conveyed while conveying the recording material between the fixing member and the pressure member. In the fixing device for thermally fixing the toner image on the material onto the recording material, a first temperature measuring unit for measuring the temperature of the surface of the fixing member, and a temperature measured by the first temperature measuring unit in the fixing operation state Control the operation of the internal heating means and the external heating means so that the temperature becomes the first set temperature, and monitor the usage status of the internal heating means and the external heating means, and A controller that performs a first control that suppresses heating of the fixing member by the internal heating unit when the usage rate of the heating unit exceeds a reference value, compared to when the usage rate is equal to or less than the reference value. It is characterized by being.

The fixing device control method according to the present invention includes a fixing member, a pressure member pressed against the surface of the fixing member, an internal heating means for heating the fixing member from the inside, and a surface of the fixing member from the outside. An external heating means for heating, and has a standby state and a fixing operation state for a fixing operation. In the fixing operation state, the recording material is conveyed between the fixing member and the pressure member. A control method of a fixing device for thermally fixing a toner image on the recording material onto the recording material,
In the fixing operation state, the operations of the internal heating unit and the external heating unit are controlled so that the temperature of the surface of the fixing member becomes the first set temperature, and the usage status of the internal heating unit and the external heating unit is used. When the usage ratio of the internal heating means to the external heating means exceeds a reference value, the heating of the fixing member by the internal heating means is suppressed more than when the usage ratio is equal to or less than the reference value. The first control is performed.

  According to the above configuration, in the fixing operation state, the first temperature measurement unit measures the temperature of the surface of the fixing member, and gives information on the measured temperature to the control unit. The internal heating means and the external heating means are controlled so as to heat up to a predetermined first set temperature. In the fixing operation state, the control unit monitors the usage status of the internal heating unit and the external heating unit, and when the usage ratio of the internal heating unit to the external heating unit exceeds a predetermined reference value, The heating of the fixing member is suppressed (first control is performed).

  The use ratio can be obtained from, for example, the respective operation periods of the internal heating means and the external heating means (period in which the power is ON), the accumulated power consumption, or the power.

  Therefore, even if some abnormality occurs and the heating by the external heating means is not normally performed, the use of the internal heating means and the external heating means can be determined without providing a temperature measurement unit for measuring the temperature inside the fixing member. Abnormalities can be detected, and the temperature rise of the members inside the fixing member can be suppressed more than necessary. Therefore, damage and deterioration of the fixing member and its peripheral members can be prevented.

  The fixing device includes a driving unit that drives at least one of the fixing member and the pressure member to rotate the fixing member and the pressure member, and the control unit performs the first control as follows: The drive means so that the paper passing speed of the recording material between the fixing member and the pressure member is lower than the paper passing speed when the use ratio of the internal heating means is equal to or less than the reference value. The structure which controls this may be sufficient.

  According to the above configuration, by reducing the sheet passing speed in the fixing operation state, the amount of heat per unit time moving from the fixing member to the recording material at the time of thermal fixing is reduced, and the heating of the fixing member is performed from the external heating unit. Heating is sufficient. Therefore, the fixing device can suppress the heating of the fixing member by the internal heating unit while continuing the image forming process.

  In the fixing device, the control unit is configured to change, as the first control, the first set temperature to a temperature lower than a temperature when the use ratio of the internal heating unit is equal to or lower than the reference value. There may be.

  According to the above configuration, since the temperature of the surface of the fixing member during the fixing operation state may be lower by changing the first set temperature low, heating from the external heating unit is sufficient for heating the fixing member. become. Therefore, the fixing device can suppress the heating of the fixing member by the internal heating unit while continuing the fixing operation state.

  The fixing device includes a second temperature measuring unit that measures a temperature of a member that contacts the surface of the fixing member in the external heating unit, and the external heating unit serves as the member that contacts the surface of the fixing member. An external heating member is provided, and the control unit controls the operation of the external heating unit so that the temperature measured by the second temperature measurement unit becomes a second set temperature, and the usage rate of the internal heating unit is the reference The structure which changes the said 2nd preset temperature in the case of exceeding a value to a temperature higher than the said 2nd preset temperature in case the said usage rate is below the said reference value may be sufficient.

  According to the above configuration, in the fixing operation state, the second temperature measurement unit measures the temperature of the external heating member, gives the information on the measured temperature to the control unit, and the control unit sets the temperature of the external heating member to a predetermined value. The external heating means is controlled to heat up to the second set temperature. And when the said usage rate exceeds the said reference value, the temperature of the external heating member during image formation becomes higher by changing 2nd preset temperature highly. As a result, the amount of heat per unit time that moves from the external heating member to the fixing member increases, so that the heating from the external heating means is sufficient for heating the fixing member. Therefore, the fixing device can suppress the heating of the fixing member by the internal heating unit while continuing the image forming process.

  In the fixing device, the control unit may be configured to stop the fixing operation state as the first control.

  According to the above configuration, when the usage rate exceeds the reference value, the fixing operation state is stopped, thereby reliably suppressing the temperature rise inside the fixing member, and the fixing member and its peripheral members are damaged and Deterioration and the like can be prevented.

  The image forming apparatus of the present invention includes any one of the fixing devices described above. Therefore, the same effects as those of the fixing device described above can be obtained.

  The control unit of the fixing device may be realized by a computer. In this case, a control program for the fixing device that realizes the control unit by the computer by operating the computer as the control unit, and A computer-readable recording medium on which it is recorded is also included in the scope of the present invention.

  According to the configuration of the present invention, even when some abnormality occurs and heating by the external heating unit is not normally performed, the internal heating unit and the external unit are not provided without providing a temperature measurement unit that measures the temperature inside the fixing member. Abnormalities can be detected from the usage status of the heating means, and an unnecessarily high temperature rise of the members inside the fixing member can be suppressed. Therefore, damage and deterioration of the fixing member and its peripheral members can be prevented.

1 is a cross-sectional view schematically showing a configuration of a fixing device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically illustrating a configuration of an image forming apparatus including the fixing device illustrated in FIG. 1. FIG. 3 is an enlarged cross-sectional view illustrating a configuration of a visible image forming unit included in the image forming apparatus illustrated in FIG. 2. FIG. 3 is a block diagram illustrating a functional configuration of the image forming apparatus illustrated in FIG. 2. FIG. 2 is a block diagram illustrating a configuration for performing temperature control of a fixing roller in the fixing device illustrated in FIG. 1. FIG. 3 is an explanatory diagram showing ON / OFF states of an internal heater lamp and an external heater lamp of a fixing roller during execution of an image forming job in the image forming apparatus shown in FIG. 2. 6 is a graph showing an example of a relationship between a lighting ratio of an internal heater lamp of a fixing roller and a core metal temperature of the fixing roller. In the fixing device shown in FIG. 1, the measurement results of the lighting ratio of the internal heater lamp and the temperature of the core metal of the fixing roller and the presence or absence of thermal damage to the core metal and its peripheral members under various conditions It is. 3 is a flowchart illustrating an operation in an image forming job in the fixing device illustrated in FIG. 1. 6 is a flowchart illustrating another example of an operation in an image forming job in the fixing device illustrated in FIG. 1.

  Hereinafter, embodiments of the present invention will be described in detail.

<Configuration of image forming apparatus>
FIG. 2 is a cross-sectional view schematically showing the configuration of the image forming apparatus 1 according to the embodiment of the present invention. The image forming apparatus 1 is an electrophotographic image forming apparatus having a configuration in which four visible image forming units are arranged in tandem. In the image forming apparatus 1, four color toner images of yellow, magenta, cyan, and black are sequentially superimposed and transferred to the recording paper 8 to form a multicolor toner image, and the multicolor toner image is fixed to the recording paper 8. To form an image. Instead of the recording paper 8, a recording material such as an OHP film can be used.

  The image forming apparatus 1 includes a toner image forming unit 2, an intermediate transfer unit 3, a secondary transfer unit 4, a recording material supply unit 5, a fixing device 6, and a scanner unit 7.

  The toner image forming unit 2 includes visible image forming units 10y, 10m, 10c, and 10b. The visible image forming units 10y, 10m, 10c, and 10b are arranged in a line in this order from the upstream side in the rotational driving direction (sub-scanning direction) of the intermediate transfer belt 21, which will be described later, that is, in the direction of the arrow 27. An electrostatic latent image corresponding to the input image information of each color is formed, and toner of a color corresponding to the electrostatic latent image is supplied and developed to form a toner image of each color. The visible image forming unit 10y forms a toner image corresponding to yellow image information, the visible image forming unit 10m forms a toner image corresponding to magenta image information, and the visible image forming unit 10c corresponds to cyan image information. The visible image forming unit 10b forms a toner image corresponding to the black image information. The visible image forming unit 10y includes a photosensitive drum 11y, a charging roller 12y, an optical scanning unit 13y, a developing device 14y, and a drum cleaner 15y.

  FIG. 3 is an enlarged cross-sectional view showing the configuration of the visible image forming unit 10y of the image forming apparatus 1 shown in FIG. The visible image forming unit 10y will be described below, but the other visible image forming units 10m, 10c, and 10b have the same configuration.

  The photosensitive drum 11y is a roller-like member having a photosensitive layer on which an electrostatic latent image and a toner image are formed, supported by a driving unit (not shown) so as to be rotatable around an axis.

  As the photosensitive drum 11y, for example, a drum including a conductive substrate (not shown) and a photosensitive layer (not shown) formed on the surface of the conductive substrate can be used. As the conductive substrate, a conductive substrate having a cylindrical shape, a columnar shape, a sheet shape or the like can be used, and among them, the cylindrical conductive substrate is preferable. Examples of the photosensitive layer include an organic photosensitive layer and an inorganic photosensitive layer.

  The organic photosensitive layer includes a laminate of a charge generation layer which is a resin layer containing a charge generation material and a charge transport layer which is a resin layer containing a charge transport material, and the charge generation material and the charge transport material in one resin layer And a resin layer containing. Examples of the inorganic photosensitive layer include a layer containing one or more selected from zinc oxide, selenium, amorphous silicon and the like. A base layer may be interposed between the conductive substrate and the photosensitive layer, and a surface layer (protective layer) for mainly protecting the photosensitive layer may be provided on the surface of the photosensitive layer.

  In the present embodiment, a photosensitive drum having a diameter of 30 mm including an aluminum base tube (conductive base) connected to the ground potential (GND) and an organic photosensitive layer having a thickness of 20 μm formed on the surface of the aluminum base tube. Is used. In the present embodiment, the photosensitive drum 11y is rotationally driven at a peripheral speed of 225 mm / s in the clockwise direction.

  The charging roller 12y is a roller-like member that is rotatably supported around an axis by a driving unit (not shown) and charges the surface of the photosensitive drum 11y to a predetermined polarity and potential. A power supply (not shown) is connected to the charging roller 12y, and the surface of the photosensitive drum 11y is charged by discharging a voltage applied from the power supply. In the present embodiment, a voltage of −1200 V is applied to the charging roller 12y, and the surface of the photosensitive drum 11y is charged to −600V. Instead of the charging roller 12y, a brush type charger, a charger type charger, a corona charger such as a scorotron, or the like can be used. The optical scanning unit 13 irradiates the charged surface of the photosensitive drum 11y with laser light 13y corresponding to yellow image information, and forms an electrostatic latent image corresponding to yellow image information on the surface of the photosensitive drum 11y. . A semiconductor laser or the like can be used for the optical scanning unit 13. In the present embodiment, an electrostatic latent image having an exposure potential of −70 V is formed on the surface of the photosensitive drum 11 y charged to −600 V.

  The developing device 14y includes a developing roller 17y, a developing blade 18y, a developing tank 19y, and stirring rollers 20y and 30y. The developing roller 17y carries the yellow developer 16y on its surface, and the yellow developer 16y is electrostatically latent on the surface of the photosensitive drum 11y in the vicinity (developing nip portion) between the developing roller 17y and the photosensitive drum 11y. Supply to the image. The developing roller 17y is supported by the developing tank 19y so as to be rotatable about its axis, and a part of the developing roller 17y projects outward from an opening formed on the surface of the developing tank 19y facing the photosensitive drum 11y. It is a roller-like member that is provided so as to be close to the surface and encloses a fixed magnetic pole (not shown). The developing roller 17y is driven to rotate in the direction opposite to that of the photosensitive drum 11y. Accordingly, in the developing nip portion, the surface of the developing roller 17y and the surface of the photosensitive drum 11y move in the same direction.

  Further, a power source (not shown) is connected to the developing roller 17y, and a DC voltage (developing voltage) is applied from the power source. As a result, the yellow developer 16y on the surface of the developing roller 17y is smoothly supplied to the electrostatic latent image. In the present embodiment, a developing voltage of −420 V is applied to the developing roller 17y. The yellow toner layer on the surface of the developing roller 17y comes into contact with the photosensitive drum 11y in the developing nip portion, and the yellow developer 16y is supplied to the electrostatic latent image. The developing blade 18y is a plate-like member having one end supported by the developing tank 19y and the other end spaced apart from the surface of the developing roller 17y. The yellow is carried on the surface of the developing roller 17y. Uniform toner layer (layer regulation). The developing tank 19y is a container-like member having an internal space with an opening formed on the surface facing the photosensitive drum 11y as described above. The developing tank 19y contains a developing roller 17y and stirring rollers 20y and 30y in its internal space, and stores the yellow developer 16y.

  The developing tank 19y is supplied with the yellow developer 16y from a toner cartridge (not shown) according to the consumption status of the yellow developer 16y. In the present embodiment, the developing tank 19y is filled with a magnetic carrier in advance. The yellow toner replenished to the developing tank 19y is mixed with the magnetic carrier and used in the form of a yellow developer (yellow two-component developer) 16y. However, the present invention is not limited to this, and a single-component developer containing only yellow toner is used. Can be used in form. The stirring rollers 20y and 30y are screw-like members that are supported so as to be rotatable around an axis in the internal space of the developing tank 19y. The stirring roller 20y is provided so as to be in pressure contact with the surface of the developing roller 17y. The agitating rollers 20y and 30y feed yellow developer 16y supplied from a toner cartridge (not shown) into the developing tank 19y to the periphery of the surface of the developing roller 17y by their rotational driving. According to the developing device 14y, the yellow developer 16y in a form in which yellow toner adheres to the magnetic carrier in the developing tank 19y is supplied to the surface of the developing roller 17y by the stirring rollers 20y and 30y, and a developer layer is formed on the surface. The The developer layer is made uniform by the developing blade 18y, and then the yellow developer 16y is selectively supplied from the developer layer to the electrostatic latent image on the surface of the photosensitive drum 11y using a potential difference or the like. A yellow toner image corresponding to yellow image information is formed.

  The drum cleaner 15y removes and collects the yellow developer 16y remaining on the surface of the photosensitive drum 11y after transferring the yellow toner image on the surface of the photosensitive drum 11y to the intermediate transfer belt 21, as will be described later. According to the visible image forming unit 10y, the surface of the photosensitive drum 11y charged by the charging roller 12y is irradiated with the signal light 13y corresponding to the yellow image information from the optical scanning unit 13 to form an electrostatic latent image. Then, a yellow developer 16y is supplied from the developing device 14y to the electrostatic latent image to develop the electrostatic latent image, thereby forming a yellow toner image. As will be described later, this yellow toner image is transferred to the intermediate transfer belt 21 that is pressed against the surface of the photosensitive drum 11 y and is rotationally driven in the direction of the arrow 29. The yellow developer 16y remaining on the surface of the photosensitive drum 11y is removed and collected by the drum cleaner 15y. This image (toner image) forming operation is repeatedly executed. The visible image forming units 10m, 10c, and 10b have the same structure as the visible image forming unit 10y except that magenta toner, cyan toner, or black toner is used instead of yellow toner. In addition, “m” indicating magenta, “c” indicating cyan, and “b” indicating black are added to the end of each reference symbol, and description thereof is omitted.

  The toner contains a binder resin, a colorant, and a release agent. As the binder resin, those commonly used in this field can be used. For example, polystyrene, styrene-substituted homopolymer, styrene copolymer, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane Etc. Binder resin can be used individually by 1 type, or can use 2 or more types together. Among these binder resins, for color toners, a binder resin having a softening point of 100 to 150 ° C. and a glass transition point of 50 to 80 ° C. is preferable from the viewpoint of storage stability and durability. Polyester having a glass transition point is particularly preferred. Polyester exhibits high transparency in the softened state. When the binder resin is polyester, when a multicolor toner image in which toner images of yellow, magenta, cyan and black are superimposed on each other is fixed on the recording paper 8, the polyester itself becomes transparent. Is obtained. As the colorant, pigments and dyes for toners conventionally used in electrophotographic image forming techniques can be used. Examples of the pigment include azo pigments, benzimidazolone pigments, quinacridone pigments, phthalocyanine pigments, isoindolinone pigments, isoindoline pigments, dioxazine pigments, anthraquinone pigments, perylene pigments, and perinone pigments. , Organic pigments such as thioindigo pigments, quinophthalone pigments, metal complex pigments, inorganic pigments such as carbon black, titanium oxide, molybdenum red, chrome yellow, titanium yellow, chromium oxide, Berlin blue, metals such as aluminum powder Examples include powder. A pigment can be used individually by 1 type or can use 2 or more types together. As the release agent, for example, wax can be used. As the wax, those commonly used in this field can be used, and examples thereof include polyethylene wax, polypropylene wax, and paraffin wax. The toner contains one or more general toner additives such as a charge control agent, a fluidity improver, a fixing accelerator, and a conductive agent in addition to the binder resin, the colorant, and the release agent. it can.

  The toner is obtained by uniformly dispersing a coloring agent, a release agent, a binder resin monomer, and the like by a pulverization method in which a colorant, a release agent, and the like are melt-kneaded and pulverized with the binder resin. It can be produced according to a known method such as a suspension polymerization method in which polymerization is performed, a binder resin particle, a colorant, a release agent, or the like is aggregated with an aggregating agent, and fine particles of the obtained aggregate are heated. The volume average particle diameter of the toner is not particularly limited, but is preferably 2 to 7 μm. When the volume average particle diameter of the toner is less than 2 μm, the fluidity of the toner is lowered, and during the developing operation, the toner supply, agitation and charging become insufficient, the toner amount is insufficient, and the reverse polarity toner is increased. This may occur and a high quality image may not be obtained. On the other hand, if the volume average particle diameter exceeds 7 μm, the toner particles having a large particle diameter that is difficult to soften to the central portion increase, so that the fixability of the image to the recording paper 8 is deteriorated and the color of the image is deteriorated, In particular, in the case of fixing to OHP, the image becomes dark.

In the present embodiment, the toner has the same configuration shown below except for the pigment. The toner is a negatively chargeable insulating nonmagnetic toner having a glass transition point of 60 ° C., a softening point temperature of 120 ° C., and a volume average particle size of 6 μm. A toner amount of 5 g / m ² is required to obtain an image density with a reflection density measurement value of 1.4 by X-Rite 310 using this toner. The toner contains a polyester (binder resin) having a glass transition point of 60 ° C. and a softening point of 120 ° C., a low molecular weight polyethylene wax (release agent) having a glass transition point of 50 ° C. and a softening point of 70 ° C., and pigments of various colors. The amount is 7% by weight of the total amount of toner, the pigment content is 12% by weight of the total amount of toner, and the balance is polyester of the binder resin. The low molecular weight polyethylene wax contained in the toner is a wax having a glass transition point and a softening point lower than that of the polyester of the binder resin.

  The intermediate transfer unit 3 (see FIG. 2) includes an intermediate transfer belt 21, primary transfer rollers 22y, 22m, 22c, and 22b, support rollers 23, 24, and 25, and a belt cleaner 26. The intermediate transfer belt 21 is an endless belt-shaped toner image carrier that is stretched between support rollers 23, 24, and 25 to form a loop-shaped movement path. The intermediate transfer belt 21 includes photosensitive drums 11y, 11m, 11c, and 11b. It rotates in the direction of arrow 27 at substantially the same peripheral speed. For the intermediate transfer belt 21, for example, a polyimide film having a thickness of 100 μm can be used. The material of the intermediate transfer belt 21 is not limited to polyimide, and films made of synthetic resins such as polycarbonate, polyamide, polyester, and polypropylene, and various rubbers can be used. In the film made of synthetic resin or various rubbers, a conductive material such as furnace black, thermal black, channel black, and graphite carbon is blended in order to adjust the electric resistance value as the intermediate transfer belt 21. The toner image carrying surface 21a of the intermediate transfer belt 21 is pressed against the photosensitive drums 11y, 11m, 11c, and 11b in this order from the upstream side in the rotational driving direction of the intermediate transfer belt 21. The positions where the intermediate transfer belt 21 is pressed against the photosensitive drums 11y, 11m, 11c, and 11b are the intermediate transfer positions of the respective color toner images. Primary transfer rollers 22y, 22m, 22c, and 22b are disposed at positions facing the photosensitive drums 11y, 11m, 11c, and 11b with the intermediate transfer belt 21 interposed therebetween.

  The primary transfer rollers 22y, 22m, 22c, and 22b face the photosensitive drums 11y, 11m, 11c, and 11b via the intermediate transfer belt 21, and are opposite to the toner image carrying surface 21a on the intermediate transfer belt 21, respectively. It is a roller-like member provided in pressure contact and capable of being driven to rotate about its axis by driving means (not shown). For the primary transfer rollers 22y, 22m, 22c, and 22b, for example, a roller-shaped member that includes a metal shaft body and a conductive layer that covers the surface of the metal shaft body is used. The shaft body is formed of a metal such as stainless steel, for example. The diameter of the shaft body is not particularly limited, but is preferably 8 to 10 mm. The conductive layer is formed of a conductive elastic body or the like. As the conductive elastic body, those commonly used in this field can be used, and examples thereof include ethylene / propylene / diene rubber (EPDM), foamed EPDM, and foamed urethane containing a conductive agent such as carbon black. A high voltage is uniformly applied to the intermediate transfer belt 21 by the conductive layer. The primary transfer rollers 22y, 22m, 22c, and 22b are opposite to the charging polarity of the toner in order to transfer the toner images formed on the surfaces of the photosensitive drums 11y, 11m, 11c, and 11b onto the intermediate transfer belt 21. A polar intermediate transfer bias is applied by constant voltage control. As a result, yellow, magenta, cyan, and black toner images formed on the photoconductive drums 11y, 11m, 11c, and 11b are sequentially superimposed and transferred onto the toner image carrying surface 21a of the intermediate transfer belt 21, thereby transferring a multicolor toner image. Is formed. However, when image information of only a part of yellow, magenta, cyan, and black is input, a visible image corresponding to the color of the input image information among the visible image forming units 10y, 10m, 10c, and 10b. A toner image is formed only in the forming unit.

  The support rollers 23, 24, and 25 are provided so as to be rotatable around an axis by driving means (not shown), and the intermediate transfer belt 21 is stretched and rotated in the direction of an arrow 27. For the support rollers 23, 24, 25, for example, an aluminum cylindrical body (pipe-shaped roller) having a diameter of 30 mm and a wall thickness of 1 mm is used. The support roller 24 is pressed against a later-described secondary transfer roller 28 via the intermediate transfer belt 21 to form a secondary transfer nip portion, and is electrically grounded. The support roller 24 has a function of stretching the intermediate transfer belt 21 and a function of secondarily transferring the toner image on the intermediate transfer belt 21 to the recording paper 8.

  The belt cleaner 26 is a member for removing the toner remaining on the toner image carrying surface 21a after the toner image on the toner image carrying surface 21a of the intermediate transfer belt 21 is transferred to the recording paper 8, and the intermediate transfer belt 21 is Via the support roller 25. The belt cleaner 26 includes a cleaning blade and a toner storage container (both not shown). The cleaning blade 26a is a plate-like member that is pressed against the toner image carrying surface 21a of the intermediate transfer belt 21 by a pressing unit (not shown) and scrapes off residual toner on the toner image carrying surface 21a. For example, a blade made of a rubber material having elasticity (for example, urethane rubber) can be used as the cleaning blade 26a. The toner storage container 26b temporarily stores toner scraped off by the cleaning blade 26a.

  According to the intermediate transfer unit 3, the toner images formed on the photosensitive drums 11 y, 11 m, 11 c, and 11 b are superimposed and transferred onto a predetermined position of the toner image carrying surface 21 a of the intermediate transfer belt 21, and the toner image is transferred. It is formed. As will be described later, this toner image is secondarily transferred to the recording paper 8 at the secondary transfer nip portion. The toner, offset toner, paper dust, and the like remaining on the toner image carrying surface 21a of the intermediate transfer belt 21 after the secondary transfer are removed by the belt cleaner 26, and the toner image is transferred again to the toner image carrying surface 21a.

  The secondary transfer unit 4 includes a support roller 24 and a secondary transfer roller 28. The secondary transfer roller 28 is a roller-like member that is in pressure contact with the support roller 24 via the intermediate transfer belt 21 and is rotatably driven in the axial direction, and is rotationally driven by a driving unit (not shown).

  The secondary transfer roller 28 includes, for example, a metal shaft body and a conductive layer coated on the surface of the metal shaft body. The metal shaft body is formed of a metal such as stainless steel, for example. The conductive layer is formed of a conductive elastic body or the like. As the conductive elastic body, those commonly used in this field can be used, and examples thereof include EPDM, foamed EPDM, foamed urethane and the like containing a conductive agent such as carbon black.

  A power supply (not shown) is connected to the secondary transfer roller 28, and a high voltage having a polarity opposite to the charging polarity of the toner is applied uniformly. A pressure contact portion between the support roller 24, the intermediate transfer belt 21, and the secondary transfer roller 28 is a secondary transfer nip portion. According to the secondary transfer unit 4, the toner image on the intermediate transfer belt 21 is conveyed to the secondary transfer nip portion, and the recording paper 8 fed from a recording material supply unit 5 (described later) is secondary-transferred in synchronization therewith. The toner image and the recording paper 8 are superimposed on each other at the secondary transfer nip portion, and the toner image is secondarily transferred onto the recording paper 8. In this way, an unfixed toner image is carried on the recording paper 8. The recording paper 8 carrying the unfixed toner image is conveyed to the fixing device 6.

  The recording material supply unit 5 includes a recording material cassette 42, a pickup roller 43, and registration rollers 44a and 44b. The recording material cassette 42 stores the recording paper 8. Examples of the recording paper 8 include plain paper, coated paper, color copy dedicated paper, OHP (overhead projector) film, and postcards. The size includes A4, A3, B5, B4, postcard size, and the like. The pickup roller 43 feeds the recording paper 8 to the conveyance path P one by one. The registration rollers 44a and 44b are a pair of roller-like members provided so as to be in pressure contact with each other, and are synchronized with the transfer of the multicolor toner image on the intermediate transfer belt 21 to the secondary transfer nip portion. The recording paper 8 is fed to the nip portion. According to the recording material supply unit 5, the recording paper 8 stored in the recording material cassette 42 is fed to the transport path P one by one by the pickup roller 43, and further, the secondary transfer nip by the registration rollers 44a and 44b. Sent to the department.

  The scanner unit 7 includes a document table (not shown), a light source (not shown), and a CCD sensor 9. A document to be copied is placed on the upper surface of the document table. A plate member made of a transparent material such as transparent glass is used for the document table. The light source illuminates the document placed on the document table. The CCD sensor 9 converts the reflected light into image information (image signal) by photoelectrically converting the reflected light from the original illuminated by the light source. The CCD sensor 9 includes a conversion unit, a transfer unit, and an output unit. The conversion unit converts an optical signal that is reflected light into an electric signal, and the transfer unit sequentially transfers the electric signal to the output unit in synchronization with a clock pulse. The output unit converts the electric signal into a voltage signal, amplifies it, lowers the impedance, and outputs it. The analog signal thus obtained is converted into a digital signal by performing known image processing. The image information of the original read by the scanner unit 7 is sent to the control unit 501 that controls all operations of the image forming apparatus, and after various image processing is performed, the image information is temporarily stored in the memory and stored in the memory according to the output instruction. The image is read out and transferred to the optical scanning unit 13 to form an image on the recording paper as the recording paper 8.

  FIG. 4 is a block diagram illustrating the image forming apparatus illustrated in FIG. 2 with a functional configuration. As illustrated in FIG. 4, the image forming apparatus 1 includes a control unit 501, a storage unit 502, a calculation unit 503, an input unit 504, a display unit 505, a reading unit 506, an image processing unit 507, and an image forming unit 508. .

  The control unit 501 controls the operation of each unit of the image forming apparatus 1 including the fixing device 6 according to various determination results, calculation results, and the like in the calculation unit 503. In the control of the fixing device 6, the power supply unit 601 (see FIG. 5) is also a target. The fixing device 6 is included in the image forming unit 508 in FIG.

  The control unit 501 and the calculation unit 503 are, for example, processing circuits realized by a microcomputer, a microprocessor, or the like that includes a central processing unit (CPU).

  The storage unit 502 includes a print command via an operation panel (input unit 504) disposed on the upper surface of the image forming apparatus 1, measurement results from various sensors (not illustrated) disposed at various locations inside the image forming apparatus 1, and the like. Image information input from an external device that is not connected, various setting values and data tables for controlling the operation of each device in the image forming apparatus 1, programs for executing various controls, and the like are written. Information input through the input unit 504 is displayed on the display unit 505.

  As the storage unit 502, a unit commonly used in this field can be used. For example, a read only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), a blu-ray disk, and the like.

  The arithmetic unit 503 retrieves various data (printing commands, measurement results, detection results, image information, etc.) input to the storage unit 502 and programs for performing various controls, and performs various detections and / or determinations.

  A reading unit 506 is provided in the scanner, reads an image from a document, acquires an image signal, and supplies the acquired image signal to the image processing unit 507.

  The image processing unit 507 performs processing suitable for image formation on the image signal from the reading unit 506 and supplies the image signal to the image forming unit 508.

  The image forming unit 508 forms a visible image on the recording paper based on the image signal provided from the image processing unit 507.

  An external device (not shown) connected to the image forming apparatus 1 is, for example, an electric / electronic device that can form or acquire image information and can be electrically connected to the image forming apparatus. For example, a computer, a digital camera, a mobile terminal, a mobile phone, etc.

  Peripheral devices are, for example, a sorter and a finisher, and these perform processing such as bookbinding, punching, Z-folding, and slip-sheet insertion on recording sheets on which images have been formed. The operations of the peripheral devices are controlled by a control unit 509 included in them.

<Configuration of fixing device>
FIG. 1 is a cross-sectional view schematically showing a configuration of a fixing device 6 according to an embodiment of the present invention. As shown in FIG. 1, the fixing device 6 includes a fixing roller (fixing member) 50, a pressure roller (pressure member) 60, an external heating device 70, and a cleaning device 80.

  The fixing roller 50 is rotatably supported by a support unit (not shown) and is driven by a drive unit (not shown) to rotate in the direction of the arrow 56 at a predetermined speed. The fixing roller 50 heats and melts the toner constituting the toner image carried on the recording paper 8 and fixes the toner on the recording paper 8 together with the pressure roller 60.

  In the present embodiment, a roller-shaped member including a cored bar 51, an elastic body layer 52 and a surface layer 53 is used as the fixing roller 50. A metal having a high thermal conductivity can be used as the metal forming the cored bar 51. For example, aluminum, iron, or the like can be used. Examples of the shape of the core metal 51 include a cylindrical shape and a columnar shape. The material constituting the elastic layer 52 is not particularly limited as long as it has rubber elasticity, but is preferably superior in heat resistance. Specific examples of such a material include silicone rubber, fluorine rubber, or fluorosilicone rubber. Among these, silicone rubber having particularly excellent rubber elasticity is preferable. The material constituting the surface layer 53 is not particularly limited as long as it has excellent heat resistance and durability and weak adhesion to the toner. For example, PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) ), A fluororesin material such as PTFE (polytetrafluoroethylene), or fluororubber. The surface layer 53 is a PFA layer having a thickness of about 30 to 50 μm. In this embodiment, the fixing roller 50 is formed by forming a 2.5 mm silicone rubber layer as the elastic body layer 52 on the iron cored bar 51 having an outer diameter of 35 mm and a wall thickness of 2 mm, and further forming a 40 μm PFA as the surface layer 53. A roller having an outer diameter of 40 mm provided with a tube layer.

  The fixing roller 50 includes an internal heater lamp (internal heating means) 54 inside. The internal heater lamp 54 is applied to the recording paper 8 for shortening the start-up time from when the image forming apparatus 1 is turned on until the image can be formed, for uniform heating of the fixing roller 50 during standby, and at the time of fixing the toner image. This is to reduce a decrease in the surface temperature of the fixing roller 50 due to heat transfer. In the present embodiment, a halogen lamp is used as the internal heater lamp 54, but not limited to this, any heating means for heating the fixing roller 50 from the inside can be used. Further, the internal heater lamp 54 is disposed along the cylindrical central axis of the fixing roller 50 (here, the same as the rotation axis).

  The pressure roller 60 is rotatably provided in a state in which the pressure roller 60 is in pressure contact with the fixing roller 50 by a pressure mechanism (not shown) on the downstream side in the rotation direction of the fixing roller 50 from the vertical lowest point of the fixing roller 50. A pressure contact portion between the fixing roller 50 and the pressure roller 60 is a fixing nip portion 55. The pressure roller 60 is driven to rotate as the fixing roller 50 rotates. The pressure roller 60 promotes fixing of the toner image to the recording paper 8 by pressing the toner in the molten state against the recording paper 8 when the fixing roller 50 heat-fixes the toner image onto the recording paper 8. To do.

  In the present embodiment, a roller-like member including a metal core 61, an elastic body layer 62, and a surface layer 63 is used as the pressure roller 60. As a material for forming the cored bar 61, the elastic body layer 62, and the surface layer 63, the same metal or material as that for forming the cored bar 51, the elastic body layer 52, and the surface layer 53 of the fixing roller 50 can be used. Further, the shape of the cored bar 61 is the same as that of the fixing roller 50. In the present embodiment, the pressure roller 60 is formed by forming a 1 mm silicone rubber layer as an elastic layer 62 on an iron core bar 61 having an outer diameter of 38 mm and a wall thickness of 1 mm, and further forming a 40 μm PFA tube as a surface layer 63. A roller having an outer diameter of 40 mm provided with a layer.

  The pressure roller 60 includes a heater lamp 64 inside. The heater lamp 64 is used to reduce the startup time from when the image forming apparatus 1 is turned on until the image can be formed. This is to prevent a sudden decrease in the surface temperature. In the present embodiment, a halogen lamp is used as the heater lamp 64.

  The external heating device 70 includes a heating belt (external heating member) 71, a first pressure roller 72, a second pressure roller 73, a thermistor (temperature measurement unit) 76, and a thermostat 77.

  The heating belt 71 is an endless belt-like member stretched around a first pressure roller 72 and a second pressure roller 73. The heating belt 71 is in contact with the outer peripheral surface of the fixing roller 50 between the pressure contact between the first pressure roller 72 and the fixing roller 50 and the pressure contact between the second pressure roller 73 and the fixing roller 50. Further, the heating belt 71 is driven to rotate in the direction of the arrow 78 as the fixing roller 50 rotates in the direction of the arrow 56.

  The material of the heating belt 71 is not particularly limited as long as it has excellent heat resistance and durability. For example, a polyimide belt or a nickel electroformed belt can be used. A fluororesin layer such as PFA or PTFE may be formed on the surface (outer surface) of the heating belt 71. In the present embodiment, an endless belt is used in which a PTFE layer is coated with about 20 μm on a 90 μm-thick polyimide substrate formed in a cylindrical shape with a diameter of 31 mm.

  The first and second pressure rollers 72 and 73 are rotatably supported and are provided in pressure contact with the surface of the fixing roller 50 via the heating belt 71 by a pressure unit (not shown). The first and second pressure rollers 72 and 73 are driven to rotate as the heating belt 71 rotates in the direction of the arrow 78. As the first and second pressure rollers 72 and 73, metal rollers made of a metal having high thermal conductivity such as aluminum and iron can be used. The metal roller may have a fluororesin layer formed on the surface thereof as necessary. In the present embodiment, aluminum rollers having a wall thickness of 2 mm and an outer diameter of 16 mm are used as the first and second pressure rollers 72 and 73. The first and second pressure rollers 72 and 73 have external heater lamps (external heating means) 74 and 75, respectively. As a result, the heating belt 71 and thus the surface of the fixing roller 50 in pressure contact with the heating belt 71 are heated via the first and second pressure rollers 72 and 73. That is, the external heater lamps 74 and 75 are heating means for heating the fixing roller 50 from the outside (outer side surface). In the present embodiment, halogen lamps are used as the external heater lamps 74 and 75. The first and second pressure rollers 72 and 73 are provided on the fixing roller 50 so that their axes are parallel to each other and have a gap.

  A power source unit 601 is connected to the heater lamps 54, 64, 74, and 75, and electric power for causing the heater lamps 54, 64, 74, and 75 to generate heat is supplied. Instead of the heater lamps 54, 64, 74, 75, a general heating means can be used.

  The thermistor 76 is provided close to the heating belt 71 at a position facing the second pressure roller 73 via the heating belt 71, and measures the temperature of the heating belt 71. The measurement result by the thermistor 76 is input to the control unit 501. The control unit 501 determines whether the temperature of the heating belt 71 is lower than a set value from the measurement result of the thermistor 76. When the temperature of the heating belt 71 is lower than the set value when the fixing roller 50 is stopped, such as during standby, the control unit 501 sends an ON signal to the power supply unit 601 connected to the external heater lamps 74 and 75. Then, electric power is supplied to the external heater lamps 74 and 75 to generate heat, and the heating belt 71 is heated. When the temperature of the heating belt 71 is equal to or higher than the set value, the control unit 501 sends an OFF signal for stopping power supply to the power supply unit 601 connected to the external heater lamps 74 and 75 to stop heating the heating belt 71. To do.

  The thermostat 77 is provided so as to oppose the second pressure roller 73 via the heating belt 71 and close to the heating belt 71 at a position downstream of the thermistor 76 in the rotation direction of the heating belt 71. Detects abnormal temperature rise. A detection result by the thermostat 77 is input to the control unit 501. The control unit 501 stops power supply from the power supply unit 601 connected to the external heater lamps 74 and 75 to the external heater lamps 74 and 75 according to the detection result of the thermostat 77.

  The thermistor (temperature measuring unit) 90 is provided so as to be close to the surface (outer peripheral surface) of the fixing roller 50 and measures the temperature of the surface of the fixing roller 50. A measurement result by the thermistor 90 is input to the control unit 501. The control unit 501 determines whether the surface temperature of the fixing roller 50 is lower than a set value from the measurement result of the thermistor 90. When the temperature of the surface of the fixing roller 50 is lower than the set value in the stop state of the fixing roller 50 such as in standby, the control unit 501 sends an ON signal to the power source unit 601 connected to the internal heater lamp 54, Electric power is supplied to the internal heater lamp 54 to generate heat, and the fixing roller 50 is heated from the inside. When the surface temperature of the fixing roller 50 is equal to or higher than the set value, the control unit 501 sends an OFF signal for stopping power supply, and stops the heating of the fixing roller 50.

  The thermostat 91 is disposed between the thermistor 90 on the downstream side in the rotation direction of the fixing roller 50 of the thermistor 90 and the heating belt 71, and is provided so as to be close to the surface of the fixing roller 50. The thermostat 91 detects an abnormal temperature rise on the surface of the fixing roller 50. A detection result by the thermostat 91 is input to the control unit 501. The control unit 501 stops power supply from the power supply unit 601 connected to the internal heater lamp 54 to the internal heater lamp 54 according to the detection result of the thermostat 91.

  Note that a configuration corresponding to the thermistor 92 and the thermostat 93 may be provided for the pressure roller 60, and the control unit 501 may perform similar control based on them.

  The cleaning device 80 includes a cleaning web 81 and a cleaning pressure roller 82. The cleaning pressure roller 82 is disposed at a position facing the fixing roller 50. The cleaning pressure roller 82 is in pressure contact with the fixing roller 50 via the cleaning web 81. The cleaning web 81 is wound up so as to move in the direction of sliding with the surface of the fixing roller 50 (the direction of the arrow 83), and cleans the surface of the fixing roller 50. Further, the cleaning web 81 may abut on the heating belt 71 and clean the surface of the heating belt 71.

  The operation of the fixing device 6 including the fixing roller 50, the pressure roller 60, and the external heating device 70 is controlled by the control unit 501. When receiving an image formation instruction, the control unit 501 sends a control signal to the power supply unit 601 that supplies power to the heater lamps 54, 64, 74, and 75. The image forming instruction is input from the operation panel of the image forming apparatus 1 or from an external device such as a computer (not shown) connected to the image forming apparatus 1. Upon receiving the control signal, the power supply unit 601 supplies power to operate the heater lamps 54, 64, 74, and 75. Thereby, the surfaces of the fixing roller 50, the pressure roller 60, and the heating belt 71 are heated.

  Thermistors 90 and 92 provided in the vicinity of the fixing roller 50 and the pressure roller 60 measure the temperatures of the surfaces of the fixing roller 50 and the pressure roller 60, respectively, and the measurement results are input to the control unit 501. Based on the measurement result, the control unit 501 determines whether the surface temperatures of the fixing roller 50 and the pressure roller 60 have reached the set temperatures. When the control unit 501 determines that the surface temperatures of the fixing roller 50 and the pressure roller 60 have reached the set temperatures, the control unit 501 drives the driving unit 602 to rotate the fixing roller 50 (see FIG. 5). ) To drive the fixing roller 50 in the direction of the arrow 56. Along with this, the pressure roller 60 and the heating belt 71 are driven to rotate. In this state, the recording paper 8 carrying the unfixed toner image is conveyed from the secondary transfer portion 4 (see FIG. 2) to the fixing nip portion 55. When the recording paper 8 passes through the fixing nip portion 55, the toner constituting the toner image is heated and pressurized and fixed on the recording paper 8 to form an image.

<Temperature control of fixing device>
Here, temperature control during the printing operation will be described in detail. FIG. 5 is a block diagram showing a configuration for controlling the temperature of the fixing roller in the fixing device shown in FIG.

  5, the control unit 501 shown in FIG. 4 includes the thermistor 90, the thermostat 91, the thermistor 76, the thermostat 77, a power supply unit 601, a drive unit 602, the calculation unit 503, and the storage unit. 502 is connected.

  The power supply unit 601 supplies power to the internal heater lamp 54 of the fixing roller 50, the external heater lamps 74 and 75 of the external heating device 70, and the heater lamp 64 of the pressure roller 60. The driving unit 602 drives the fixing roller 50 to rotate. The drive unit 602 may drive the pressure roller 60 to rotate.

  The control unit 501 supplies power from the power supply unit 601 to the internal heater lamp 54 and the external heater lamps 74 and 75 based on signals from the thermistors 90 and 76 and thermostats 91 and 77 or a calculation result in the calculation unit 503. Control.

  When the image forming apparatus 1 (see FIG. 2) is on standby without executing an image forming job (image forming process), the fixing roller 50 is stopped, and the surface temperature of the fixing roller 50 is set by an internal heater lamp 54 inside. The temperature of the heating belt 71 is controlled to 190 ° C. by external heater lamps 74 and 75 inside the first pressure roller 72 and the second pressure roller 73, respectively. The controller 501 (see FIG. 4) controls the ON / OFF of each heater lamp.

  6 shows an image forming apparatus 1 shown in FIG. 2 in which an internal heater lamp 54 and external heater lamps 74 and 75 of the fixing roller 50 are being executed during the execution of an image forming job (fixing operation state, while the fixing roller 50 is rotating). It is explanatory drawing which shows the ON / OFF state of.

  When the image forming apparatus 1 receives an image forming job, the fixing roller 50 starts rotating, and at the same time, the set temperature of the heating belt 71 is changed to 220 ° C. At this time, the external heater lamps 74 and 75 of the external heating device 70 are turned on, and the fixing roller 50 is heated from the surface by the heat from the heating belt 71. At this time, the internal heater lamp 54 of the fixing roller 50 is in an OFF state. When the surface temperature of the fixing roller 50 measured by the thermistor 90 reaches a set temperature of 195 ° C., the external heater lamp 74 outside the fixing roller 50 is set even if the temperature of the heating belt 71 does not reach the set temperature of 220 ° C. , 75 are turned off. When the surface temperature of the fixing roller 50 falls below the set temperature of 195 ° C., the external heater lamps 74 and 75 outside the fixing roller 50 are turned on again.

  As described above, during the rotation of the fixing roller 50, the surface temperature of the fixing roller 50 is basically controlled by supplying heat from the heating belt 71. However, there is a limit to the heat transfer from the heating belt 71 to the fixing roller 50, and even if the temperature of the heating belt 71 reaches the set temperature of 220 ° C., the surface temperature of the fixing roller 50 reaches the set temperature of 195 ° C. If not reached, the internal heater lamp 54 provided inside the fixing roller 50 is turned on, and the fixing roller 50 is further heated from the inside. If the temperature of the heating belt 71 falls below the set temperature of 220 ° C. while the surface temperature of the fixing roller 50 does not reach the set temperature of 195 ° C., the internal heater lamp 54 of the fixing roller 50 is turned off, Instead, the external heater lamps 74 and 75 outside the fixing roller 50 are turned on again to heat the surface of the fixing roller 50 from the outside.

  That is, when the surface temperature of the fixing roller 50 reaches the set temperature, the internal heater lamp 54 and the external heater lamps 74 and 75 of the fixing roller 50 are in the OFF state. When the surface temperature of the fixing roller 50 has not reached the set temperature, if the temperature of the heating belt 71 has reached the set temperature, the internal heater lamp 54 of the fixing roller 50 is in the ON state, and the external heater lamps 74 and 75 are in the OFF state. It is. When the surface temperature of the fixing roller 50 does not reach the set temperature, and the temperature of the heating belt 71 does not reach the set temperature, the internal heater lamp 54 of the fixing roller 50 is in the OFF state and the external heater lamps 74 and 75 are in the ON state. It is.

  As described above, the surface temperature of the fixing roller 50 during execution of the image forming job is controlled based on the temperature information of the temperature measuring member such as the thermistor 90 provided in the vicinity of the surface of the fixing roller 50. This is performed by supplying heat from the outside of the fixing roller 50 by the heating belt 71 including, but depending on the situation, it is also performed from the inside of the fixing roller 50 by the internal heater lamp 54 of the fixing roller 50.

  Further, the usage ratio between the internal heater lamp 54 and the external heater lamps 74 and 75 may be adjusted by increasing or decreasing the power supplied to each.

  FIG. 7 is a graph showing an example of the relationship between the lighting ratio of the internal heater lamp 54 of the fixing roller 50 and the temperature of the core metal 51 of the fixing roller 50.

The lighting ratio of the internal heater lamp 54 here means that either the internal heater lamp 54 made of a halogen lamp or the external heater lamps 74 and 75 is lit while the fixing roller 50 is rotating (during the fixing operation of the fixing device 6). This is the ratio of the time during which the internal heater lamp 54 is lit to the time during which it is running.
Lighting ratio = (Internal heater lamp lighting time)
/ ((Internal heater lamp lighting time) + (External heater lamp lighting time))
As described above, the external heater lamps 74 and 75 are always turned ON / OFF at the same time, and the “lighting time of the external heater lamp” is not counted redundantly, and either one of the lighting times is not counted. equal. Note that when the lighting ratio of the internal heater lamp 54 increases, the temperature of the cored bar 51 increases.

  The lighting time of the internal heater lamp and the lighting time of the external heater lamp during the fixing operation are calculated from the time integration value of the ON signal sent from the control unit 501 to the power supply unit 601 of each heater lamp. The control unit 501 may store the accumulated time value of each ON / OFF signal in the storage unit 502.

  Normally, when the set temperature of the fixing roller 50 and the heating belt 71 is not changed during execution of the image forming job, the lighting ratio of the internal heater lamp becomes a substantially constant value. However, when the heat supply from the outside of the fixing roller 50 becomes insufficient due to the rotation failure of the heating belt 71, or the cleaning web 81 as a cleaning member is caught between the heating belt 71 and the fixing roller 50 for some reason. When the heat supply from the heating belt 71 to the fixing roller 50 is significantly reduced, the lighting ratio of the internal heater lamp is remarkably increased. As a result, the temperature of the cored bar 51 of the fixing roller 50 is abnormally increased, and the elastic layer of the fixing roller 50 is deteriorated or the resin member at the bearing portion of the cored bar 51 is damaged.

<Experimental result>
Hereinafter, experimental results for verifying thermal damage to the fixing roller 50 and its peripheral members generated under various conditions will be described.

  Note that there are journal portions where the elastic body layer 52 is not provided at both ends in the axial direction of the core metal 51 of the fixing roller 50. A metal ball bearing is fitted to the journal portion through a heat insulating bush made of resin (PPS). Further, a resin gear for transmitting a driving force is provided further outside in the axial direction of the journal portion. Under various conditions, all the mechanical configurations of the fixing device 6 are the same as shown in FIG. The set temperature of the surface of the fixing roller 50 was 195 ° C., the set temperature of the heating belt 71 was 220 ° C., and each heater lamp was controlled by the control shown in FIG.

In the experiment, a process speed was 225 mm / sec (paper feeding speed 50 sheets / min), and A4 paper having a basis weight of 64 g / m ² was continuously fed through 500 sheets. FIG. 8 shows the measurement result of the lighting ratio of the internal heater lamp and the temperature of the core metal 51 of the fixing roller 50 and the core metal 51 and its peripheral members in the fixing device 6 shown in FIG. 1 under various conditions. It is explanatory drawing which shows the presence or absence of thermal damage. The temperature of the cored bar 51 was measured by bringing a thermocouple into contact with the journal part.

  Case 1 is a case where the fixing device 6 is in a normal state and there is sufficient heat supply from the heating belt 71 to the fixing roller 50. Case 2 is a case where the rotation of the heating belt 71 that should be driven to rotate with respect to the fixing roller 50 has stopped. Case 3 is a case where the cleaning web 81 is caught between the fixing roller 50 and the heating belt 71.

  In Case 1, the lighting ratio of the internal heater lamp during the period when the image forming job was executed was 30%, and the temperature of the cored bar 51 reached saturation at 205 ° C. Further, no heat damage to the fixing roller 50 and its peripheral members was confirmed even after the paper was passed.

  In Case 2, the lighting ratio of the internal heater lamp during the period when the image forming job was executed was 51%, and the temperature of the core metal 51 reached saturation at 267 ° C. After passing the paper, deterioration of the heat insulating bush made of resin was confirmed.

  In Case 3, the lighting ratio of the internal heater lamp during the period when the image forming job is executed is 67%, and the temperature of the cored bar 51 reaches 300 ° C. when 300 sheets are passed. It was completely melted.

  As described above, when the heating ratio (lighting ratio) of the internal heater lamp of the fixing roller is significantly higher than usual due to a problem specific to the external heating method, only the temperature information of the thermistor and thermostat provided on the fixing roller is used. In the conventional configuration in which the heating is controlled based on the above, an abnormal temperature rise inside the fixing roller may not be detected. As a result, when some abnormality occurs, members around the fixing roller may be deteriorated or damaged.

<Control of fixing device based on lighting ratio>
Therefore, in the fixing device 6 of the present embodiment, the lighting ratio of the internal heater lamp of the fixing roller 50 during execution of the image forming job is monitored, and the control unit 501 (see FIG. 4) performs control based on the lighting ratio.

  When the control unit 501 of the image forming apparatus 1 in the standby state receives an image forming job, the internal heater lamp 54 or the external heater lamps 74 and 75 of the fixing roller 50 are turned on to heat the fixing roller 50 from the inside or the outside. . Further, the control unit 501 calculates a time integrated value of the ON signal corresponding to each heater lamp transmitted from the control unit 501 to the power supply unit 601 at a predetermined timing, and calculates the lighting ratio of the internal heater lamp from the calculated time integrated value. calculate. Then, the control unit 501 compares the lighting ratio with the reference value, and when the lighting ratio exceeds the reference value, the fixing device 6 stops the fixing operation and heating of each heater lamp. In the present embodiment, the lighting ratio is calculated for a period after the image forming job is received. However, the lighting ratio may be calculated for a period after a predetermined period has elapsed since the image forming job was received. When the temperature of the metal core 51 is 250 ° C. or lower, no thermal damage was observed on the fixing roller 50 and the surrounding resin member. Therefore, based on the experimental results shown in FIG. 8, the lighting ratio is 45% or lower. Therefore, it was determined that the temperature of the core metal 51 could be suppressed to 250 ° C. or less, and the reference value was set to 45%.

  Using the image forming apparatus 1 of the present embodiment that performs the above control, image formation is performed under the same conditions as in the case 3 of the above experiment (a state in which the cleaning web 81 is caught between the fixing roller 50 and the heating belt 71). An experiment was conducted.

  With the start of execution of the image forming job, the external heater lamps 74 and 75 are lit to raise the temperature of the heating belt 71 from the set temperature 190 ° C. in the standby state to the set temperature 220 ° C. during the fixing operation. The heater lamp 54 is not lit. For this reason, even when the heat transfer from the heating belt 71 to the fixing roller 50 is not good, the external heater lamps 74 and 75 are mainly turned on in the initial stage during the execution of the image forming job. The ratio does not increase significantly. However, since the lighting ratio of the internal heater lamp exceeded 45% when the number of sheets passed reached 20, the fixing device 6 stopped the fixing operation. In this state where 20 sheets were passed, no thermal damage was observed on the fixing roller 50 and its peripheral members.

  The fixing device 6 calculates the lighting ratio of the internal heater lamp at a predetermined timing and compares it with a reference value. When the lighting ratio exceeds the reference value, the fixing device 6 stops the fixing operation and suppresses heating by the internal heater lamp 54. As a result, deterioration or damage of the fixing roller 50 and its peripheral members can be prevented.

  In this embodiment, the fixing device stops the fixing operation when the lighting ratio exceeds a reference value. However, the present invention is not limited to this, and the fixing device (or the fixing device) is not limited to this. The control unit) may be configured to suppress the heating by the internal heating means of the fixing roller and continue the fixing operation.

  Further, when the lighting ratio exceeds the reference value, the sheet passing speed that the image forming apparatus sends to the fixing device may be decreased. The sheet passing speed can be reduced by increasing the interval between the recording sheets to be passed or reducing the process speed. By reducing the paper passing speed, the amount of heat transferred per hour from the fixing roller to the recording paper during the fixing operation is reduced, and the heat transferred from the heating belt is sufficient, and heating by the internal heater lamp of the fixing roller is sufficient. It can suppress, and a lighting ratio can also be reduced.

  As described above, when the sheet passing speed is reduced during the execution of the image forming job, the integrated value or lighting ratio of the ON state that has been measured so far is once reset, and then the lighting ratio is measured again to obtain another reference value. The comparison determination may be performed.

  When the lighting ratio exceeds the reference value, the set temperature on the surface of the fixing roller during the fixing operation may be lowered within a range that does not significantly affect the fixing capability of the fixing device. Usually, the set temperature of the surface of the fixing roller during the fixing operation is set high in consideration of a margin so that the fixing property is sufficiently maintained. In the case of the present embodiment, the set temperature of the surface of the fixing roller during the fixing operation, which is normally set at 195 ° C., may be changed to 190 ° C. when the lighting ratio exceeds the reference value. When the set temperature during the fixing operation on the surface of the fixing roller is lowered, the temperature that must be maintained on the surface of the fixing roller is lowered, so that heating by the internal heater lamp can be suppressed and the lighting ratio is also lowered. be able to.

  As described above, when the set temperature during the fixing operation on the surface of the fixing roller is lowered during the execution of the image forming job, the integrated value or lighting ratio of the ON state that has been measured is reset once, and then the lighting ratio is again set. May be measured and compared with another reference value.

  Further, when the lighting ratio exceeds the reference value, the set temperature of the surface of the fixing roller may not be changed, and the set temperature during the fixing operation of the heating belt may be increased. In the case of the present embodiment, the set temperature during the fixing operation of the heating belt, which is normally set to 220 ° C., may be changed to 225 ° C. when the lighting ratio exceeds the reference value. When the set temperature during the fixing operation of the heating belt is increased, the amount of heat transferred from the heating belt to the fixing roller increases, so that the heating of the internal heater lamp can be suppressed and the lighting ratio can also be reduced. .

  As described above, when the set temperature during the fixing operation of the heating belt is raised during the execution of the image forming job, the ON-state integrated value or lighting ratio that has been measured so far is reset once, and then the lighting ratio is measured again. Then, a comparison determination with another reference value may be performed.

  As described above, the lighting ratio exceeds the reference value, the sheet passing speed is decreased, the set temperature during the fixing operation on the surface of the fixing roller is decreased, or the set temperature during the fixing operation of the heating belt is increased. After performing the control, the lighting ratio is calculated again and compared with the same or another reference value. As a result, if the lighting ratio exceeds the reference value, the sheet passing speed may be further reduced. Then, other controls such as stopping the fixing operation may be performed to further suppress the heating of the internal heater lamp.

  When the fixing device is operating normally, the lighting ratio does not exceed the reference value. Therefore, if the lighting ratio exceeds the reference value, there is a high possibility that an abnormality has occurred in the fixing device. When the control unit detects that the lighting ratio exceeds the reference value during execution of the image forming job, the control unit may display a warning indicating that the lighting ratio has reached an abnormal value on the display unit. Accordingly, the image forming apparatus can detect that an abnormality has occurred in the fixing device without adding a new thermistor or thermostat, and can notify the user of the abnormality.

  In addition, the image forming apparatus may perform the process of calculating the lighting ratio and comparing it with the reference value every time a predetermined number of sheets are fixed or every predetermined time. The timing of the above process can be arbitrarily set.

  Note that immediately after the end of the image forming job, the temperature of the heating belt may exceed the set temperature 220 ° C. during the fixing operation due to overshoot. Under such circumstances, when a new image forming job is executed immediately after the end of the image forming job, the external heater lamp is turned off because the temperature of the heating belt has already reached the set temperature 220 ° C. during the fixing operation. The internal heater lamp is turned on. For this reason, the lighting ratio of the internal heater lamp immediately after the start of the image forming job becomes a large value, and then the lighting ratio approaches a constant value as time passes (increase in the number of fixing processes). As described above, the lighting ratio immediately after the start of the image forming job greatly depends on the previous state and varies widely. Therefore, the calculation and determination of the first lighting ratio accepts the image forming process and starts heating by each heater lamp. Then, it may be configured to be performed after the elapse of a predetermined period or after a predetermined number of processes.

  The calculation and determination of the lighting ratio may be performed for the most recent predetermined period. For example, at the stage where 100 consecutive image forming jobs are executed, the control unit may calculate the lighting ratio during the fixing operation of the last 10 out of 100 sheets and compare it with a reference value.

  Further, as a lighting ratio, a ratio of a period in which the internal heater lamp is in an ON state to a period including a time in which the internal heater lamp and the external heater lamp are in an OFF state may be used.

  Should the control unit suppress the heating of the fixing roller by the internal heating means by comparing the degree of use (use ratio) of the internal heating means with respect to the usage of the external heating means to a predetermined standard? It can be determined whether or not. Here, when the control of each heating means is not the ON / OFF control but the control for adjusting the amount of power to be energized, the control unit integrates the internal heating means with respect to the integrated power amount of the external heating means for a predetermined period. It may be determined whether or not heating of the fixing roller by the internal heating unit should be suppressed by comparing the amount of electric power with a predetermined criterion. That is, the control unit monitors the usage status such as the usage period or usage amount of the internal heating means and the external heating means, and determines whether or not the heating of the fixing roller by the internal heating means should be suppressed based on the usage status. Also good.

  A suitable reference value can be determined in advance by performing the above-described experiment.

<Control flow>
The image forming apparatus 1 according to the present embodiment is configured to apply the above processing to 10 or more image forming jobs. The lighting ratio is calculated after the fixing processing of 10 recording sheets and compared with the reference value. Based on this, the control is changed.

  FIG. 9 is a flowchart showing the operation of the image forming job in the fixing device 6 shown in FIG.

  When an instruction for a print job is input from the input unit 504 to the control unit 501, the image forming unit 508 first performs a printing process on one sheet of recording paper (S1).

  Next, when the number of prints performed in the print job is not 10 or more (No in S2), the control unit 501 determines whether or not all the print processes designated for the print job have been completed (S3). . If all the print processes specified for the print job have not been completed (No in S3), the process returns to S1 to perform the remaining print processes. When all the printing processes specified for the print job have been completed (Yes in S3), the image forming unit 508 ends the execution of the print job.

  When the number of prints performed in the print job is 10 or more (Yes in S2), the control unit 501 has accumulated time during which the internal heater lamp 54 of the fixing roller 50 is in an ON state after the print job is started. A and an accumulated time B in which the external heater lamps 74 and 75 outside the fixing roller 50 are ON are obtained (S4). And the control part 501 calculates | requires lighting ratio C = A / (A + B) (S5).

  The control unit 501 compares the reference value D stored in the storage unit 502 with the calculated lighting ratio C, and when the lighting ratio C is larger than the reference value D (Yes in S6), the control unit 501 An instruction to cancel the print job is issued to the printer 508 (S7), and the image forming unit 508 stops the printing process and ends the execution of the print job.

  When the lighting ratio C is equal to or less than the reference value D (No in S6), the process proceeds to S3, and the control unit 501 determines whether all the printing processes designated for the print job are completed.

  FIG. 10 is a flowchart showing another example of the operation in the image forming job in the fixing device 6 shown in FIG.

  When an instruction for a print job is input from the input unit 504 to the control unit 501, the image forming unit 508 first performs a printing process on one sheet of recording paper (S11).

  Next, when the number of prints performed in the print job is not 10 or more (No in S12), the control unit 501 determines whether or not all the print processes specified for the print job have been completed (S13). . If all the printing processes specified for the print job have not been completed (No in S13), the process returns to S11 to perform the remaining printing processes. When all the printing processes designated for the print job are completed (Yes in S13), the image forming unit 508 ends the execution of the print job.

  When the number of prints performed in the print job is 10 or more (Yes in S12), the control unit 501 determines the accumulated time A during which the internal heater lamp 54 of the fixing roller 50 is ON and the outside of the fixing roller 50. An accumulated time B in which the heater lamps 74 and 75 are ON is obtained (S14). And the control part 501 calculates | requires lighting ratio C = A / (A + B) (S15).

  The control unit 501 compares the reference value D stored in the storage unit 502 with the calculated lighting ratio C. If the lighting ratio C is greater than the reference value D (Yes in S16), the control unit 501 performs image formation. An instruction to reduce the sheet passing speed is output to the section 508 (S17). Further, the control unit 501 initializes the accumulated time A and the accumulated time B to 0 (S18). Thereby, when calculating | requiring the integration time A and the integration time B again in S14, the integration time after the initialization process in S18 will each be calculated | required.

  Thereafter, the process proceeds to S13, and the control unit 501 determines whether or not all the printing processes designated for the print job have been completed.

  When the lighting ratio C is equal to or less than the reference value D (No in S16), the process similarly proceeds to S13, and the control unit 501 determines whether all the printing processes specified for the print job have been completed.

  In the process of S17, instead of decreasing the sheet passing speed, the control unit 501 decreases the set temperature during the fixing operation on the surface of the fixing roller or increases the set temperature during the fixing operation of the heating belt. Etc. may be performed.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  In the present embodiment, the control unit 501 may be configured by a control integrated circuit board, or may be realized by software using a processor such as a CPU. When the control unit 501 is realized by software, for example, the control unit 501 includes a CPU (central processing unit) that executes instructions of a control program for realizing each function, a ROM (read only memory) that stores the program, and the program A random access memory (RAM) for expanding the program, a storage device (recording medium) such as a memory for storing the program and various data, and the like. An object of the present invention is to provide a recording medium in which a program code (execution format program, intermediate code program, source program) of a control program of the control unit 501 that is software that realizes the above-described functions is recorded in a computer-readable manner This is achieved by supplying the control unit 501 and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include tapes such as magnetic tapes and cassette tapes, magnetic disks such as floppy (registered trademark) disks / hard disks, and disks including optical disks such as CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  The control unit 501 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. This communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, A satellite communication network or the like can be used. Further, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE1394, USB, power line carrier, cable TV line, telephone line, ADSL line, infrared rays such as IrDA and remote control, It is also possible to use wireless such as Bluetooth (registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network. The present invention can also be realized in the form of a computer data signal (data signal sequence) embedded in a carrier wave in which the program code is embodied by electronic transmission.

  The present invention can be applied to a fixing device provided in an electrophotographic image forming apparatus and an image forming apparatus provided with the fixing device.

1 Image forming device 6 Fixing device 8 Recording paper (recording material)
50 Fixing roller (fixing member)
51, 61 Core metal 52, 62 Elastic layer 53, 63 Surface layer 54 Internal heater lamp (internal heating means)
60 Pressure roller (Pressure member)
64 Heater lamp 70 External heating unit 71 Heating belt (external heating member)
72 First pressure roller 73 Second pressure rollers 74, 75 External heater lamp (external heating means)
76, 90, 92 Thermistor (temperature measurement unit)
77, 91, 93 Thermostat 80 Cleaning means 81 Cleaning web 82 Cleaning pressure roller 501 Control unit 502 Storage unit 503 Calculation unit 504 Input unit 505 Display unit 508 Image forming unit 601 Power supply unit

Claims (9)

A fixing member; a pressure member pressed against the surface of the fixing member; an internal heating unit that heats the fixing member from the inside; and an external heating unit that heats the surface of the fixing member from the outside. And a fixing operation state for a fixing operation. In the fixing operation state, the toner image on the recording material is transferred to the recording material while conveying the recording material between the fixing member and the pressure member. In a fixing device for heat fixing on a material,
A first temperature measuring unit for measuring the temperature of the surface of the fixing member;
In the fixing operation state, the operations of the internal heating unit and the external heating unit are controlled so that the temperature measured by the first temperature measurement unit becomes the first set temperature, and the internal heating unit and the external heating unit are controlled. When the usage rate of the internal heating unit with respect to the external heating unit exceeds a reference value, the heating of the fixing member by the internal heating unit is monitored more than when the usage rate is equal to or less than the reference value. And a control unit that performs first control to be suppressed. Drive means for driving at least one of the fixing member and the pressure member to rotate the fixing member and the pressure member;
In the first control, the control unit performs the sheet passing when the sheet passing speed of the recording material between the fixing member and the pressure member is less than the reference value. The fixing device according to claim 1, wherein the driving unit is controlled so as to be lower than a speed.   The control unit, as the first control, changes the first set temperature to a temperature lower than a temperature when the use ratio of the internal heating means is equal to or less than the reference value. Or the fixing device according to 2; A second temperature measuring unit that measures the temperature of the member that contacts the surface of the fixing member in the external heating unit;
The external heating means includes an external heating member as the member that contacts the surface of the fixing member,
The control unit controls the operation of the external heating unit so that the temperature measured by the second temperature measurement unit becomes a second set temperature, and when the usage ratio of the internal heating unit exceeds the reference value, 4. The fixing device according to claim 1, wherein the second set temperature is changed to a temperature higher than the second set temperature when the use ratio is equal to or less than the reference value. 5. .   The fixing device according to claim 1, wherein the control unit stops the fixing operation state as the first control.   An image forming apparatus comprising the fixing device according to claim 1. A fixing member; a pressure member pressed against the surface of the fixing member; an internal heating unit that heats the fixing member from the inside; and an external heating unit that heats the surface of the fixing member from the outside. And a fixing operation state for a fixing operation. In the fixing operation state, the toner image on the recording material is transferred to the recording material while conveying the recording material between the fixing member and the pressure member. A control method of a fixing device for heat fixing on a material,
In the fixing operation state, the operations of the internal heating unit and the external heating unit are controlled so that the temperature of the surface of the fixing member becomes the first set temperature, and the usage status of the internal heating unit and the external heating unit is used. When the usage ratio of the internal heating means to the external heating means exceeds a reference value, the heating of the fixing member by the internal heating means is suppressed more than when the usage ratio is equal to or less than the reference value. A control method for a fixing device, wherein the first control is performed.   A control program for operating the fixing device according to claim 1, wherein the control program causes a computer to function as the control unit.   A computer-readable recording medium on which the control program according to claim 8 is recorded.

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