JP2017161617A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of image noise and the like by using a non-contact heating method of blowing superheated steam to an unfixed toner image on a recording medium and preventing the superheated steam from making a swirl.SOLUTION: A fixing device includes: a superheated steam generating part 21 that generates superheated steam A; an inlet part 22 which is positioned on an upstream side in a conveyance direction of a recording medium 11 and to which the recording medium 11 having an unfixed toner image 12 formed thereon is carried in; a superheated steam blowing part 23 that blows, under atmospheric pressure, forward along the conveyance direction, the superheated steam A to the unfixed toner image 12 on the recording medium 11 which has been carried in from the inlet part 22; and an open outlet part 24 that is positioned on a downstream side in the conveyance direction of the recording medium 11 and lets the recording medium 11 and an air flow pass.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fixing device for fixing an unfixed toner image on a recording medium to a recording medium in an electrophotographic process, and an image forming apparatus including the fixing device. In particular, it is characterized in that an unfixed toner image on a recording medium is heated and fixed by a non-contact heating method.

  Conventionally, in an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a composite machine thereof, a toner image held on the surface of an image holding member is transferred to a recording medium, and then transferred by a fixing device. The unfixed toner image is fixed on the recording medium.

  As the fixing device, conventionally, in addition to a contact heating type fixing device using a heating roller or the like, non-contact heating method such as radiant fixing using radiant heat such as a quartz lamp or flash fixing using flash light such as a xenon lamp. In recent years, a fixing device using a non-contact heating method in which water vapor is blown onto an unfixed toner image has been developed.

  Here, as a fixing device using a non-contact heating method in which water vapor is blown onto an unfixed toner image, for example, in Patent Document 1, an unfixed toner image is fixed using a hot gas containing a considerable amount of water vapor. It is disclosed.

  Patent Document 2 discloses that a superheated steam supply unit that supplies superheated steam to a recording medium is provided, and an unfixed toner image transferred to the recording medium is heated and fixed with superheated steam. ing.

  However, the fixing devices disclosed in Patent Document 1 and Patent Document 2 have high sealing performance by narrowing the inlet and outlet portions. In particular, in Patent Document 1, a sealing member is provided at the entrance and exit of the recording medium in the fixing device to enhance the sealing performance. In Patent Document 2, the sealing space is isolated by isolating the internal space of the fixing device from the outside by a casing. Is increasing.

  However, when the hermeticity in the fixing device is increased in this way, the water vapor supplied into the fixing device is bounced back on the side of the outlet and becomes vortex, and the toner is scattered by the vortex water vapor, resulting in image noise. May occur. In addition, a recording medium that has been curled or lifted in the fixing device is caught by the exit portion, and conveyance failure or jamming is likely to occur.

JP-A-11-237801 Japanese Unexamined Patent Publication No. 2016-24225

  The present invention uses a non-contact heating method in which superheated steam is blown onto an unfixed toner image on a recording medium, and suppresses occurrence of image noise and the like by reducing the vortex in the fixing device. It is an object of the present invention to provide a fixing device and an image forming apparatus that can be used.

  In order to solve the above-described problems, the fixing device according to the present invention includes a non-contact fixing unit that melts an unfixed toner image that has undergone a transfer process in an electrophotographic process in a non-contact manner and fixes the image on a recording medium. The non-contact fixing unit includes a superheated steam generation unit that generates superheated steam, an inlet portion into which a recording medium on which the unfixed toner image is formed, and an unfixed toner image on the recording medium. A superheated steam spraying unit that sprays the superheated steam in the forward direction and the transport direction of the recording medium at atmospheric pressure, and an outlet from which the recording medium on which the toner image is fixed in a non-contact manner by the spraying of the superheated steam is carried out And at least the outlet portion has an opening property that allows airflow to pass therethrough.

  In this way, since the superheated steam is blown against the unfixed toner image on the recording medium in the forward direction with respect to the transport direction of the recording medium, the unfixed toner image is hardly distorted by the blowing of the superheated steam. Further, scattering of the unfixed toner image is reduced. In addition, since the outlet portion is open to allow airflow to pass therethrough, the airflow of the superheated steam is prevented from being bounced back at the outlet portion, and vortexes are suppressed, and scattering of an unfixed toner image due to the vortices can be reduced. Thus, the occurrence of image noise is suppressed by reducing the scattering of the unfixed toner image. Further, when the vortex of the superheated steam is suppressed, the recording medium is less likely to curl or float, and even if the recording medium is curled or lifted, the opening of the outlet portion causes the recording medium to open. Is less likely to be caught by the exit portion, and it is possible to suppress the occurrence of conveyance failure and jamming.

  Moreover, you may make it the said entrance part also have the openness which allows airflow to pass through. In this way, the openness in the non-contact fixing unit is increased, the air flow of the superheated steam is further stabilized, and the occurrence of image noise, conveyance failure and jamming are further suppressed.

  Moreover, it is preferable that the said superheated steam production | generation part produces | generates 100 degreeC or more and 400 degrees C or less superheated steam by further heating the saturated water vapor | steam obtained by heating water under atmospheric pressure. In the case of superheated steam generated in this way, gaseous water molecules cover the toner particle surface and can efficiently enter the toner particles, so that the toner particles can be heated quickly and uniformly. . In addition, since the temperature of the superheated steam is 100 ° C. or higher, it is possible to prevent the toner from being insufficiently melted and to prevent the fixing property from being lowered. be able to.

  Further, the non-contact fixing unit may include a superheated steam recovery unit that recovers superheated steam sprayed on the recording medium on the downstream side in the transport direction of the recording medium with respect to the inlet. In this way, it is possible to suppress the superheated steam sprayed onto the recording medium from diffusing out of the fixing device from the outlet portion.

  Further, the superheated steam recovery unit may include a cooling unit that cools the recovered superheated steam and returns it to water, and a water storage unit that stores the water. If it does in this way, reuse of the water by the collect | recovered water vapor | steam can be aimed at.

  A separation unit that separates water and substances other than water may be provided between the cooling unit and the water storage unit. In this way, it is possible to prevent substances other than water from being mixed into the superheated steam and sprayed onto the recording medium.

  A cover protrudes toward the recording medium so as not to contact the recording medium at the inlet portion and the outlet portion, and a protruding end of the cover of the outlet portion is more than a protruding end of the cover of the inlet portion. It may be located on the side close to the recording medium. In this way, the superheated steam flowing on the recording medium can be efficiently recovered at the protruding end of the cover of the outlet portion.

  The superheated steam recovery section may have a substantially triangular recovery nozzle that expands toward the side closer to the transported recording medium. In this way, it is possible to efficiently recover the superheated steam spreading on the recording medium.

  Further, the superheated steam spraying section may have a substantially triangular spray nozzle that spreads toward the side closer to the transported recording medium. If it does in this way, the said superheated steam to spray can be spread on the said recording medium as uniformly as possible.

  The non-contact fixing section includes a recording medium support section that supports and conveys the recording medium from the inlet section to the outlet section, and the recording medium support section rotates and drives a heat-resistant conveying belt. You may make it have. If it does in this way, conveyance of the recording medium can be performed appropriately under the high heat by the superheated steam.

  In addition, the non-contact fixing unit may include leakage prevention means for preventing the superheated steam generated by the residual heat from leaking from the superheated steam spraying unit after the heating of the superheated steam generation unit is stopped. Here, for example, even if the heating in the superheated steam generation unit is stopped due to a conveyance trouble of the recording medium generated in the fixing device, the superheated steam generated by the residual heat leaks from the superheated steam spraying unit and is stopped. May burn the recording medium. By providing the leakage prevention means, the stopped recording medium can be prevented from being burnt.

  In addition, the non-contact fixing unit may include a water droplet receiving unit that receives the generated water droplets. In this way, for example, it is possible to prevent a situation in which water droplets are dropped on the recording medium and the recording medium is soiled.

  Moreover, you may make it provide the side cover which covers the side of the said recording medium arrange | positioned along the conveyance direction of the said recording medium. In this way, diffusion of the superheated steam from the side of the recording medium can be suppressed.

  The toner to be used may be an encapsulated toner that is treated in an aqueous medium and includes a release component. Some of these toners require a relatively high fixing temperature and can be made relatively inexpensively. By using the toner as described above in a fixing device using high-temperature superheated steam, it is possible to form an image at low cost without particularly detrimental to requiring a relatively high fixing temperature.

  In addition, a pressure contact portion may be provided that adjusts the temperature by contacting and pressurizing the recording medium transported from the outlet portion and fixes the toner image on the recording medium smoothly. In this way, the surface of the toner image fixed in a non-contact manner with superheated steam can be made smooth, and the temperature adjustment can adjust the recording medium after the fixing process to an appropriate temperature that a person can touch. .

  The pressure contact portion may include a temperature sensor that detects the temperature of the pressure contact portion and a cooling unit that cools the pressure contact portion. In this way, it is possible to accurately adjust the temperature of the recording medium by the pressure contact portion.

  Further, a temperature sensor for detecting the temperature of the recording medium carried out from the outlet portion may be provided. In this way, since the temperature of the recording medium can be detected in advance before the pressure fixing by the pressure contact portion, the temperature of the recording medium can be more accurately adjusted by the pressure contact portion.

  In the image forming apparatus according to the present invention, the fixing apparatus as described above according to the present invention is used as a fixing apparatus that melts and fixes an unfixed toner image on a recording medium.

  In the fixing device according to the present invention, the superheated steam is sprayed on the unfixed toner image on the recording medium in the forward direction with respect to the transport direction of the recording medium. Is less likely to occur and scattering of unfixed toner images is reduced. In addition, since the outlet portion has an opening property through which the recording medium and the airflow pass, the superheated steam airflow is also prevented from being rebounded at the outlet portion, and a vortex is also suppressed, and scattering of an unfixed toner image due to the vortex Less. Thus, the occurrence of image noise can be suppressed by reducing the scattering of the unfixed toner image. Further, when the vortex of the superheated steam is suppressed, the recording medium is less likely to curl or float, and even if the recording medium is curled or lifted, the recording medium can be opened due to the openness of the outlet portion. Is less likely to be caught by the exit portion, and it is possible to suppress the occurrence of conveyance failure and jamming.

FIG. 3 is a schematic explanatory diagram illustrating a non-contact fixing unit and a pressure contact unit of the fixing device according to the embodiment of the present invention. It is the schematic explanatory drawing which showed the superheated steam production | generation part of the non-contact fixing part in FIG. 1, a superheated steam spraying part, and a superheated steam recovery part by planar view. It is the schematic explanatory drawing which showed the superheated steam production | generation part of the non-contact fixing part in FIG. It is the schematic explanatory drawing which showed the collection | recovery nozzle of the superheated steam recovery part of the non-contact fixing part in FIG. FIG. 2 is a schematic explanatory diagram illustrating a spray nozzle of a non-contact fixing unit in FIG. 1. It is the schematic perspective view which showed the non-contact fixing | fixed part in FIG.

  Next, a fixing device according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. The fixing device according to the present invention is not limited to the one shown in the following embodiment, and can be implemented with appropriate modifications within a range not changing the gist thereof.

  A fixing device 1 shown in FIG. 1 is a device that melts and fixes an unfixed toner image 12 on a recording medium 11 that has undergone a transfer process in an electrophotographic process, onto the recording medium 11. The pressure contact part 3 is provided.

  The non-contact fixing unit 2 is located in the casing 2a whose lower side is opened, the superheated steam generation unit 21 that generates superheated steam A, and the upstream side in the transport direction of the recording medium 11, and the unfixed toner image An inlet portion 22 into which the recording medium 11 on which the recording medium 12 is formed is carried in, and a superheated steam spraying portion that blows the superheated steam A onto the unfixed toner image 12 of the recording medium 11 that has entered the inlet portion 22 under atmospheric pressure. 23 and an outlet 24 located on the downstream side in the transport direction of the recording medium 11 and from which the recording medium 11 is unloaded.

  The non-contact fixing section 2 is provided with a recording medium support section 25 that supports and conveys the recording medium 11 from the inlet section 22 to the outlet section 24. The recording medium support section 25 has heat resistance. The conveyance belt 25a having the rotation is driven by a roller 25b.

  Here, the conveyance direction of the recording medium 11 by the conveyance belt 25a is the B direction in FIG. 1, and the B direction conveyance speed of the recording medium 11 and the B direction movement speed of the superheated steam A are substantially the same. I am doing so. In FIG. 1, the superheated steam A discharged from the superheated steam spraying unit 23 is drawn like steam, but the superheated steam A is kept in a superheated state even if the temperature falls due to contact with the outside air. Since it does not condense, it does not appear as steam. Further, since the superheated steam A has a larger amount of heat than the saturated steam at the same pressure, the molecular movement becomes more active and the density becomes smaller.

  Further, the inlet portion 22 and the outlet portion 24 are not provided with a seal member, and have an opening property through which the recording medium 11 and the airflow can pass. Plate-shaped covers 22 a and 24 a protrude from the inlet portion 22 and the outlet portion 24 toward the recording medium (downward) so as not to contact the recording medium 11.

  Here, the opening height at the inlet portion 22 is the height from the upper surface of the conveyor belt 25a to the lower end of the cover 22a. Similarly, the opening height at the outlet 24 is the height from the upper surface of the transport belt 25a to the lower end of the cover 24a. The opening height at the inlet portion 22 and the outlet portion 24 is set, for example, in a range of 5 mm to 150 mm, and preferably in a range of 10 mm to 100 mm. Further, the lower end (protruding end) of the cover 24a of the outlet portion 24 is positioned closer to the recording medium 11 (lower side) than the lower end (protruding end) of the cover of the inlet portion.

  The superheated steam spraying portion 23 is provided on the upper side of the inlet portion 22 and blows the superheated steam A obliquely downward, in the forward direction of the recording medium 11 (B direction). It is like that.

  Further, as shown in FIGS. 1 and 2, the superheated steam generation unit 21 further heats water to generate saturated steam, and further heats the saturated steam under atmospheric pressure to 100 ° C. A steam heating unit 21e that generates superheated steam A at 400 ° C. or less and supplies the superheated steam A to the superheated steam spraying unit 23, and saturated steam generated by the water heating unit 21a to the steam heating unit 21e. 21d of piping to send.

  Moreover, as shown in FIG. 3, the said water heating part 21a consists of the ceramic heater 21c which is a resistance heating element, and the heat resistant porous filter 21b provided in the upper part, for example. Here, saturated water vapor can be generated by a known method, but since the specific heat of water is as large as 1 cal / g · K (18 ° C.), it is necessary to increase the surface area of the heating part in consideration of energy saving. In particular, a water vapor generating apparatus composed of a heat-resistant porous body and a resistance heating element is particularly suitable. As the heat-resistant porous filter 21b, porous glass or porous ceramics can be used.

  In addition, the steam heating unit 21e is configured to heat, for example, a metal pipe through which saturated steam passes through electromagnetic induction heating (IH), and can change the saturated steam to superheated steam A in a short time. . Here, the generation method of the superheated steam A is not particularly limited as long as the saturated steam can be heated to 100 ° C. or higher under atmospheric pressure. However, in consideration of shortening the warm-up time, electromagnetic induction heating is performed. The excess device used is particularly suitable.

  The pipe 21d is provided with a valve 21f made of, for example, an electromagnetic solenoid so as to turn on / off the supply of saturated water vapor through the pipe 21d. The valve 21f serves as a leakage preventing means for preventing the superheated steam generated by the residual heat from leaking out of the superheated steam spraying section 23 after the heating of the steam heating section 21e is stopped. For example, when a paper jam is detected by a sensor for detecting a paper jam, the heating stop of the steam heating unit 21e and the closing operation of the valve 21f are performed simultaneously, and the saturated steam is supplied to the steam heating unit 21e. Is stopped, the generation and leakage of superheated steam is prevented.

  Further, the non-contact fixing unit 2 includes a superheated steam recovery unit 26 that recovers the superheated steam A sprayed on the recording medium 11. The superheated steam recovery unit 26 includes a recovery nozzle 261, a recovery pipe 262, a cooling unit 263, a separation unit 264, and a water storage unit 265.

  Further, the recovery nozzle 261 is provided at a position upstream of the outlet portion 24 in the transport direction of the recording medium 11 and above the outlet portion 24. The recovery nozzle 261 is provided with a suction fan 261a at a position on the upper side thereof, and recovers the superheated steam A flowing toward the outlet 24 by suctioning upward.

  The recovery pipe 262 guides the superheated steam A recovered by the recovery nozzle 261 to the cooling unit 263.

  The cooling unit 263 changes the recovered superheated steam A into liquid water using a cooling method such as a water cooling method or an air cooling method. The cooling unit 263 needs to be sufficiently cooled in order to change the phase from superheated steam A to steam and then to water, and is therefore preferably formed in an elongated tubular shape.

  The separation unit 264 is provided between the cooling unit 263 and the water storage unit 265, and separates water and substances other than water. Impurities in water supplied from the cooling unit 263 Remove. The separation unit 264 can be configured to be removable and washable or replaceable.

  In addition, the water storage unit 265 stores water from which the impurities are removed. And this water storage part 265 is equipped with the water supply pipe 265a for supplying stored water to the water heating part 21a. In addition, a water supply port for supplying water to the water storage unit 265 may be provided.

  Further, as shown in FIG. 6, the non-contact fixing unit 2 includes a side cover 27 that covers both sides of the recording medium 11. The side cover 27 is disposed along the conveyance direction of the recording medium 11 and has a height that covers the side of the recording medium support portion 25.

  Thus, in the non-contact fixing unit 2, the superheated steam A is blown against the unfixed toner image 12 of the recording medium 11 in the forward direction with respect to the transport direction of the recording medium 11. The curling of the unfixed toner image 12 due to A is less likely to occur, and the scattering of the unfixed toner image 12 is reduced.

  Further, since the outlet portion 24 has an opening property through which the recording medium 11 and the airflow pass, the airflow of the superheated water vapor A is suppressed from being bounced back by the outlet portion 24, and unfixed toner due to the vortex is suppressed. The scattering of the image 12 can also be reduced. Thus, the occurrence of image noise can be suppressed by reducing the scattering of the unfixed toner image 12. In addition, curling and floating of the recording medium 11 are less likely to occur in the recording medium 11 by suppressing the vortex of the superheated steam A, and even if the recording medium 11 is curled or lifted, the outlet 24 is opened. Therefore, the recording medium 11 is less likely to be caught by the outlet portion 24, and the occurrence of poor conveyance and jamming can be suppressed.

  Further, if the inlet portion 22 also has an opening property that allows the recording medium 11 and an air flow to pass therethrough, the opening property of the non-contact fixing unit 2 is increased, and the air flow of the superheated steam A is further stabilized. Generation of noise, conveyance failure and jam are further suppressed.

  In the superheated steam generation unit 21, saturated steam obtained by heating water is further heated under atmospheric pressure to generate superheated steam A of 100 ° C. or more and 400 ° C. or less. When superheated steam is used, gaseous water molecules cover the surface of the toner particles and can enter the interior of the toner particles efficiently, so that the inside of the toner particles can be heated quickly and uniformly.

  Here, the so-called low-temperature fixing toner is designed so that the melting temperature or softening temperature is around 100 ° C. If a toner having a softening temperature near 100 ° C. is fixed at 100 ° C. by a conventional contact heating type fixing device, a low temperature offset occurs or the fixing property becomes insufficient. However, in the case of superheated water vapor, gaseous water molecules cover the toner particle surface and can penetrate into the toner particle surface, so that the inside of the toner particle can be quickly heated. The low-temperature fixing toner as described above includes composite particles of a low-melting-point material having a melting point of 100 ° C. or lower and a high-melting-point material having a melting point of 100 ° C. or higher. And improvements such as lowering the melting point. The non-contact fixing unit 2 can quickly and uniformly heat the interior of the toner even with superheated steam at 100 ° C. Therefore, the low-melting-point substance melts in the toner particles and is absorbed by the internal penetration of water molecules. And elution on the toner surface. The image that has passed through the non-contact fixing unit 2 is in a state where a low melting point substance, in particular, a release component is eluted on the surface, and the low melting point substance eluted on the surface serves as a binder, Fix the ingredients. Even in superheated steam at 100 ° C., sufficient fixability can be ensured depending on the content of the low melting point substance.

  Here, the reason why the lower limit temperature of the superheated steam A is set to 100 ° C. is that the use environment of the MFP (multifunctional peripheral) under the atmospheric pressure lower than 1 atm is assumed, and the boiling point of water is 100 Even when the temperature is lower than 0 ° C., the non-contact fixing portion 2 needs to be superheated steam of 100 ° C. or higher, and higher temperatures are advantageous in terms of image quality, fixing properties, and high speed.

  On the other hand, when considering fixing with 100 ° C. saturated water vapor (under 1 atm), in the case of this saturated water vapor, although water molecules are in a gaseous state, they immediately become below the boiling point when they come into contact with the toner particles, and change into liquid water. Accordingly, since water molecules cannot enter the toner particles, the toner particles cannot be melted quickly and uniformly. In addition, since a large amount of moisture adheres to the surface of the toner particles, the moisture content of the obtained image is increased, and there is a possibility that the recording medium curls and wrinkles.

  Moreover, since the upper limit of the temperature of the superheated steam A is set to 400 ° C., it is possible to avoid burning and scorching of the recording medium 11 (recording paper).

  Further, when the superheated steam recovery unit 26 that recovers the superheated steam A sprayed on the recording medium 11 is provided, the superheated steam A sprayed on the recording medium 11 is prevented from diffusing out of the fixing device 1. can do.

  In addition, when the superheated steam recovery unit 26 includes the cooling unit 263 and the water storage unit 265, it is possible to reuse water by the recovered steam.

  Further, when a separation unit 264 for separating water and substances other than water is provided between the cooling unit 263 and the water storage unit 265, substances other than water are mixed into the superheated steam A and enter the recording medium 11. Spraying can be prevented.

  If the recovery nozzle 261 of the superheated steam recovery unit 26 is provided at a position upstream of the outlet 24 in the transport direction of the recording medium 11, the recovery efficiency of the superheated steam A can be increased. . Since the outlet portion 24 is open to allow air current to pass therethrough, the recovery nozzle 261 of the superheated steam recovery portion 26 is positioned at a position downstream of the outlet portion 24 in the transport direction of the recording medium 11. It is also possible to provide it.

  Further, as shown in FIG. 4, the recovery nozzle 261 may have a substantially triangular shape that spreads toward the side closer to the transported recording medium 11. According to this, the superheated steam A spread on the recording medium 11 can be efficiently recovered. The width of the recovery nozzle 261 on the widened side is preferably equal to or greater than the width of the recording medium 11. Further, if the partition wall 261b is provided in the recovery nozzle 261 so as to correspond to the substantially triangular shape, a suction can be performed with a uniform force as much as possible on the widened side.

  Further, as shown in FIG. 5, the spray nozzle 23 a may have a substantially triangular shape that expands toward a side closer to the recording medium 11 to be conveyed. According to this, the superheated steam A to be sprayed can be efficiently spread on the recording medium 11. It is desirable that the width of the spray nozzle 23a on the widened side is equal to or greater than the width of the recording medium 11. Further, if the partition wall 23b is provided in the spray nozzle 23a so as to correspond to the substantially triangular shape, the superheated steam A to be sprayed can be spread on the recording medium 11 as uniformly as possible. In addition, by providing a temperature sensor 23c in each flow path partitioned by the partition wall 23b, the temperature of the superheated steam A to be sprayed is detected, and the steam heating temperature control by the steam heating unit 21e or abnormality detection processing is performed. You may make it perform.

  Further, when the protruding end of the cover 24a of the outlet portion 24 is located closer to the recording medium 11 than the protruding end of the cover 22a of the inlet portion 22, the superheated steam A flowing on the recording medium 11 is used. Can be efficiently recovered at the protruding end of the cover 24a of the outlet portion 24.

  In addition, when the recording medium support unit 25 is configured to rotationally drive the conveyance belt 25a having heat resistance, the recording medium 11 can be appropriately conveyed under high heat by the superheated steam A. The recording medium support portion 25 may be a belt made of a metal plate, a metal plate coated with a heat-resistant polymer having high releasability such as a fluororesin, or a fluororesin fabric. In addition, in order to reduce toner contamination during double-sided printing and image noise due thereto, a belt having both heat resistance and releasability, specifically, a belt made of a fluororesin fabric is further driven to rotate. preferable.

  In addition, when the superheated steam generation unit 21 is stopped from being heated, it is provided with a water leakage prevention means (for example, a valve 21f) that prevents the superheated steam generated by the residual heat from leaking out of the superheated steam spraying unit 23. After the heating in the superheated steam generation unit 21 is stopped due to a conveyance trouble of the recording medium 11, the superheated steam A leaks from the superheated steam spraying unit 23 and the stopped recording medium 11 in the fixing device 1 is burnt. Can be prevented. In addition, it is also possible to provide a valve that is electrically turned on / off in the superheated steam spraying portion 23 as a water leakage preventing means.

  Further, a water droplet receiving means for receiving the generated water droplets may be provided, for example, in the vicinity of the spray nozzle 23a or in the vicinity of the recovery nozzle 261. In this way, when the superheated steam A comes into contact with the spray nozzle 23a or the recovery nozzle 261, it can be partially cooled to form water droplets and fall onto the recording medium 11 to prevent the image from getting wet. A water droplet receiving means can be provided on the lower side of the casing 2a of the fixing device 1 as required. The water droplet receiving means is not particularly limited as long as it has heat resistance and water absorption, but a nonwoven fabric made from heat resistant fibers such as glass fibers and aramid fibers is particularly suitable.

  Here, the toner to be used is not particularly limited as long as it is a toner that can be fixed by heat, but is preferably an encapsulated toner that is processed in an aqueous medium and includes a release component. In recent years, from the viewpoint of energy saving of fixing devices, further low-temperature fixing of toner has progressed. However, there is a trade-off relationship between low-temperature fixing of toner, heat resistance and mechanical strength of binder resin, and toner process. Compatibility between compatibility and low-temperature fixability is an issue. A chemical toner whose main binder resin is a styrene-acrylic type has a particular problem of compatibility between process compatibility and low-temperature fixability due to its molecular structure and polymer properties. On the other hand, a polyester-based chemical toner whose main binder resin is polyester is relatively easy to achieve both process compatibility and low-temperature fixability, but the cost of the binder resin is high, leading to an increase in toner cost. Since the non-contact fixing unit 2 uses superheated steam at 100 ° C. or higher, the non-fixed toner on the recording medium 11 can be heated uniformly and quickly above the melting / melting temperature, so the thermal properties of the binder resin are required. The process compatibility can be improved because it is not necessary to reduce the temperature more than that, and it is not necessary to add a low melting point substance more than necessary. Therefore, it can be said that the non-contact fixing unit 2 is suitable for a styrene-acrylic chemical toner as a main binder resin.

  Further, when the side cover 27 covering the side of the recording medium 11 is provided, diffusion of the superheated water vapor A from the side of the recording medium 11 can be suppressed. If the superheated steam A hits the side cover 27 and rebounds, a vortex may be generated in the vicinity of the side cover 27, but the vortex is generated in the vicinity of the recording medium 11 on the recording medium support portion 25. The impact of this will be minor.

  Next, the pressure contact portion 3 will be described with reference to FIG. The pressure contact unit 3 adjusts the temperature of the recording medium 11 and presses the non-contact fixing toner image 12A whose toner layer height is lowered by the non-contact fixing unit 2 to pressurize the recording medium 11 and the recording medium. 11, the non-contact fixing toner image 12 </ b> A on the surface 11 is fixed smoothly and a contact fixing toner image 12 </ b> B is obtained. By providing such a pressure contact portion 3, the surface of the non-contact fixing toner image 12A can be smoothed to obtain the contact fixing toner image 12B, and the recording medium after the fixing process can be obtained by adjusting the temperature. 11 can be lowered to an appropriate temperature that a person can touch.

  The pressure contact portion 3 includes, for example, a fixing roller 31 in which an elastic body is externally fitted to a cylindrical core metal and a pressure roller 32 in a pressure contact state. Although a sufficiently large nip portion is formed at the contact portion between the fixing roller 31 and the pressure roller 32, it is not necessary to press and crush the toner. What is necessary is just to press-contact with the pressure roller 32 by a comparatively light load. The surface layer of the fixing roller 31 is made of fluorine for the purpose of improving releasability from the melted toner image and reducing image noise caused by securing a non-offset region, toner contamination, and adhesion of a toner release component. It is preferable to have a release layer such as a coat or a PFA tube layer.

  The pressure contact unit 3 includes a temperature sensor 33 that detects the temperature of the pressure contact unit 3 in a non-contact manner, and a cooling fan 34 as a cooling unit that cools the pressure contact unit 3, for example. In this way, temperature control can be performed so that the surface temperature of the fixing roller 31 and the pressure roller 32 is equal to or lower than the high temperature offset temperature. Then, by performing temperature control using such a temperature sensor 33, it is possible to accurately adjust the temperature of the recording medium 11 delivered from the pressure contact portion 3.

  Further, a temperature sensor 35 that detects the temperature of the recording medium 11 conveyed to the pressure contact unit 3 may be provided. The temperature of the superheated water vapor A in the non-contact fixing unit 2 is in the range of 100 ° C. to 400 ° C. based on the use environment, toner thermal characteristics, toner adhesion amount, and contact time with the toner layer (fixing speed and superheated water vapor flow distance). Although the temperature of the non-contact fixing toner image 12A on the recording medium 11 that has passed through the non-contact fixing unit 2 can be detected by the temperature sensor 35, the temperature correction of the superheated steam A and the roller surface temperature are small. Adjustment and the like can be performed. As a result, the offset can be reliably suppressed, and a high-quality image can be stably obtained.

  The image forming apparatus of the present invention uses the fixing device 1 as described above in the present invention as a fixing device that melts and fixes an unfixed toner image on the recording medium 11. In such an image forming apparatus, the photosensitive member is rotated and the surface of the photosensitive member is charged by the charging device, and the image forming information is obeyed to the charged photosensitive member by the latent image forming device. Exposure is performed to form an electrostatic latent image on the surface of the photoreceptor. Then, the photosensitive member on which the electrostatic latent image is formed is developed by supplying toner from the developing device to the electrostatic latent image on the photosensitive member to form a toner image on the surface of the photosensitive member. Next, the toner image formed on the photoreceptor as described above is transferred to a recording medium, and the recording medium on which the unfixed toner image is thus formed is supplied to the fixing device 1. The recording medium on which the toner image is fixed by the fixing device 1 is discharged out of the device by a discharge roller. Of course, the image forming apparatus is not limited to a single-color image forming apparatus, and may be a full-color image forming apparatus.

1: Fixing device 2: Non-contact fixing unit 3: Pressure contact unit 11: Recording medium 12: Unfixed toner image 12A: Non-contact fixing toner image 12B: Contact fixing toner image 21: Superheated steam generation unit 21a: Water heating unit 21b: heat-resistant porous filter 21c: ceramic heater 21d: piping 21e: steam heating unit 21f: valve 22: inlet 22a: cover 23: superheated steam spraying unit 23a: spraying nozzle 24: outlet 24a: cover 25: recording medium Support section 25a: Conveying belt 25b: Roller 26: Superheated steam recovery section 27: Side cover 31: Fixing roller 32: Pressure roller 33: Temperature sensor 34: Cooling fan 35: Temperature sensor 261: Recovery nozzle 261a: Suction fan 262: Recovery piping 263: Cooling unit 264: Separation unit 265: Storage Part 265a: water supply pipe A: superheated steam

Claims (18)

In a fixing device including a non-contact fixing unit that melts and fixes a non-fixed toner image that has undergone a transfer process in an electrophotographic process onto a recording medium in a non-contact manner,
The non-contact fixing unit is
A superheated steam generator for generating superheated steam;
An inlet portion into which the recording medium on which the unfixed toner image is formed is loaded;
A superheated steam spraying unit that sprays the superheated steam on the unfixed toner image on the recording medium in the forward direction and the transport direction of the recording medium at atmospheric pressure;
A fixing device comprising: an outlet portion from which a recording medium on which a toner image is fixed in a non-contact manner by spraying of the superheated steam is carried out; and at least the outlet portion has an opening property that allows airflow to pass therethrough. .   The fixing device according to claim 1, wherein the inlet portion also has an opening property that allows airflow to pass therethrough.   3. The fixing device according to claim 1, wherein the superheated steam generation unit further generates saturated superheated steam at 100 ° C. or more and 400 ° C. or less by further heating saturated steam obtained by heating water at atmospheric pressure. A fixing device.   4. The fixing device according to claim 1, wherein the non-contact fixing unit collects the sprayed superheated steam on the downstream side in the transport direction of the recording medium from the inlet unit. 5. A fixing device comprising a superheated steam recovery section.   5. The fixing device according to claim 4, wherein the superheated steam recovery unit includes a cooling unit that cools the recovered superheated steam and returns it to water, and a water storage unit that stores the water.   The fixing device according to claim 5, further comprising: a separation unit that separates water and a substance other than water between the cooling unit and the water storage unit.   7. The fixing device according to claim 4, wherein a cover protrudes toward the recording medium so as not to contact the recording medium at the entrance and the exit, and the exit The protruding end of the cover of the portion is positioned closer to the recording medium than the protruding end of the cover of the inlet portion.   8. The fixing device according to claim 4, wherein the superheated steam recovery unit includes a substantially triangular recovery nozzle that expands toward a side closer to the transported recording medium. Fixing device.   9. The fixing device according to claim 1, wherein the superheated steam spraying unit includes a substantially triangular spray nozzle that spreads toward a side closer to the transported recording medium. Fixing device.   The fixing device according to any one of claims 1 to 9, wherein the non-contact fixing unit includes a recording medium support unit that supports and conveys the recording medium from the entrance to the exit. The fixing apparatus according to claim 1, wherein the recording medium support portion has a structure for rotating a recording medium conveyance belt having heat resistance.   11. The fixing device according to claim 1, wherein after the heating of the superheated steam generation unit is stopped, the non-contact fixing unit leaks superheated steam generated by residual heat from the superheated steam spraying unit. A fixing device comprising leakage preventing means for preventing the leakage.   12. The fixing device according to claim 1, further comprising a water droplet receiving unit that receives the generated water droplets.   13. The fixing device according to claim 1, further comprising a side cover disposed along a conveyance direction of the recording medium and covering a side of the recording medium. apparatus.   14. The fixing device according to claim 1, wherein the toner to be used is an encapsulated toner that is processed in an aqueous medium and includes a release component. .   15. The fixing device according to claim 1, wherein temperature adjustment is performed by contacting and pressurizing the recording medium carried out from the exit portion, and a toner image on the recording medium is displayed. A fixing device comprising a pressure contact portion that adheres smoothly.   16. The fixing device according to claim 1, wherein the pressure contact portion includes a temperature sensor that detects a temperature of the pressure contact portion, and a cooling unit that cools the pressure contact portion. And a fixing device.   17. The fixing device according to claim 1, further comprising a temperature sensor configured to detect a temperature of the recording medium carried out from the exit portion. An image forming apparatus comprising the fixing device according to claim 1.

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