JP5304614B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to efficiently utilize effective cooling of recording paper which is in a high temperature state after fixing, and exhaust heat from the recording paper after fixing. <P>SOLUTION: The image forming apparatus includes: a moisture applying device 6 applying moisture to the recording paper on which an unfixed image is thermally fixed in a fixing device 4 and whose temperature rises on a downstream side in a recording paper conveying direction of the fixing device 4; water vapor transport pipes 20a, 20b and 20c collecting water vapor evaporated from the recording paper after the moisture is applied by the moisture applying device 6, and high-temperature atmosphere around the fixing device 4 including the fixing device 4 and transporting them to a prescribed position where humidity control or temperature control is performed in the image forming apparatus 1; and condensers 21a, 21b, 21c and 21d arranged at exits of the water vapor transport pipes 20a, 20b and 20c. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a fax machine, and a multifunction machine.

  2. Description of the Related Art An electrophotographic image forming apparatus such as a copying machine or a printer has a plurality of units that generate heat such as a developing device and a fixing device. In particular, in a fixing device that fixes a toner image on a recording paper (paper) by a heating / pressing operation, the recording paper on which the toner image is transferred to a nip portion between a heating roller and a pressure roller with a built-in heater or the like is used. When carried in, the toner is softened by contact heat transfer from the heating roller, and the toner is pressed against the recording paper by a pressure roller having an elastic member (elastic layer) provided on the surface, so that a toner image is formed on the recording paper. Is established.

  As described above, since the recording paper on which the toner image is fixed by the heating / pressurizing operation by the fixing device becomes a high temperature state, the toner image is continuously fixed on the recording paper as the speed of the image forming apparatus in recent years increases. If the toner is discharged, problems such as high temperature toner melting and adhering to the overlapping recording papers occur. For this reason, an image forming apparatus provided with a cooling unit for cooling a recording sheet in a high temperature state after fixing has been proposed (see, for example, Patent Document 1).

  The image forming apparatus of Patent Document 1 has a configuration in which a heat pipe is brought into contact with a recording paper (recording material) that is in a high temperature state after fixing to cool the heat of the recording paper by heat conduction. Further, in order to utilize the exhaust heat from the recording paper after fixing, heat conduction is performed from the heat pipe to the support member that supports the pre-fixing conveyance belt provided on the upstream side of the fixing device through the heat conduction means. Thus, the recording paper before fixing is preheated.

  By the way, in the image forming apparatus of Patent Document 1, in the heat transfer from the recording paper after fixing to the heat pipe, since the recording paper is moving on the surface of the heat pipe, the recording paper and the heat pipe Heat contact loss occurred due to the heat resistance of the air layer and the heat pipe container metal at the contact interface, and the exhaust heat from the recording paper after fixing could not be used efficiently. For this reason, there has been a demand for an image forming apparatus capable of efficiently using the effective cooling of the recording paper in a high temperature state after fixing and the exhaust heat from the recording paper after fixing.

  SUMMARY OF THE INVENTION Accordingly, the present invention provides an image forming apparatus capable of efficiently using the effective cooling of the recording paper in a high temperature state after fixing and the exhaust heat from the recording paper after fixing. With the goal.

  In order to achieve the above object, the invention according to claim 1 is a fixing unit that heats an unfixed image on a recording material formed by the image forming unit and fixes the unfixed image on the recording material. In the image forming apparatus, a moisture applying unit that applies moisture to a recording material that is heated and fixed by the fixing unit and has an increased temperature on the downstream side of the fixing unit in the recording material conveyance direction. Collecting a high-temperature gas containing water vapor that evaporates from the recording material after moisture is given by the moisture-providing unit, and a high-temperature atmosphere around the fixing unit including the fixing unit, and controlling humidity in the image forming apparatus It is characterized by comprising a heat transport path for transporting to a predetermined place where temperature control is performed, and a heat exchanger disposed at the outlet of the heat transport path.

  According to a second aspect of the present invention, the predetermined portion is at least in the vicinity of a paper feed unit in which a plurality of recording materials are stored in a stacked state, in the vicinity of a developing unit in the image forming unit, and in the recording unit conveyance of the fixing unit. It is one in the vicinity of the conveyance path on the upstream side in the direction.

  According to a third aspect of the present invention, the temperature of the recording material and the atmosphere in the image forming apparatus disposed at least near the downstream of the fixing unit in the recording material conveyance direction and upstream of the fixing unit in the recording material conveyance direction, Moisture application amount adjustment for adjusting the water application amount provided to the recording material, provided in the water supply device, and a sensor for detecting the water vapor density, an exhaust means disposed on the downstream side of the heat exchanger And a control means for controlling the moisture flow rate by the exhaust gas flow rate of the exhaust means and the moisture content adjustment means, and the control means has a water vapor density of saturated steam based on sensor information detected by the sensor. The exhaust means and the moisture application amount adjusting means are controlled so that the water vapor density becomes the maximum amount without exceeding the density.

  The invention according to claim 4 is characterized in that, after the control by the control means is performed once, the control means performs the control again based on sensor information detected by the sensor.

  According to a fifth aspect of the present invention, the moisture applying unit discharges water droplets to at least one surface of the recording material after fixing, which is disposed in the vicinity of the fixing unit on the downstream side in the recording material conveyance direction. A water discharge head having a plurality of discharge ports, and after water droplets discharged from the plurality of discharge ports are applied to the surface of the recording material, each of the adjacent water droplets penetrates into the recording material and spreads. It is characterized in that at least one of the arrangement interval of the plurality of discharge ports, the number of the discharge ports, and the discharge amount from the discharge ports is optimally set so that the ranges do not overlap.

  The invention described in claim 6 is characterized in that a thermoelectric exchanger capable of converting heat into electric power is provided in the vicinity of the heat exchanger.

  The invention described in claim 7 is characterized in that the moisture applying means applies water containing at least one of a transparent agent and a brightener to the recording material in addition to water. It is said.

  The invention described in claim 8 is characterized in that an ion generating electrode for generating ions by applying a high voltage is provided in the vicinity of the downstream side of the fixing unit in the recording material conveyance direction.

  According to the present invention, moisture can be applied to the recording paper after heat-fixing to effectively cool the recording paper, so that the recording paper can be prevented from being curled and discharged. Further, when moisture is applied to the recording paper after heat-fixing, the evaporated water vapor and the exhaust heat of the high-temperature atmosphere around the fixing unit including the fixing unit are efficiently collected, and a predetermined location in the image forming apparatus is collected. Therefore, the exhaust heat utilization efficiency can be further increased.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a schematic diagram illustrating the vicinity of a fixing device of the image forming apparatus according to the first exemplary embodiment of the present invention. (A) is a figure which shows the comparative reference characteristic before and behind heat fixing when water is not provided to the recording paper after heat fixing, (b) is a figure which shows the 1st control characteristic in Embodiment 1 of this invention. The flowchart which shows the control processing in Embodiment 1 of this invention. FIG. 6 is a schematic diagram showing the vicinity of a fixing device of an image forming apparatus according to a second embodiment of the present invention. (A) is sectional drawing of a water discharge head to Embodiment 2 of this invention, (b) is a top view of a water discharge head. FIG. 3 is a cross-sectional view illustrating a state in which water droplets are applied to a recording sheet conveyed from a water discharge head. FIG. 6 is a plan view showing a state in which water droplets are applied to the recording paper conveyed from the water ejection head. The figure which shows the 2nd control characteristic in Embodiment 2 of this invention. The flowchart which shows the control processing in Embodiment 2 of this invention. FIG. 6 is a schematic diagram illustrating the vicinity of a fixing device of an image forming apparatus according to a third embodiment of the present invention. FIG. 6 is a schematic diagram showing the vicinity of a fixing device of an image forming apparatus according to a fourth embodiment of the present invention.

Hereinafter, the present invention will be described based on the illustrated embodiments.
<Embodiment 1>
FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a schematic diagram illustrating the vicinity of a fixing device of the image forming apparatus in FIG. The image forming apparatus according to the present embodiment is an example applied to an electrophotographic color printer having a fixing unit that fixes a toner image on a recording sheet by a heating / pressurizing operation.

  As shown in FIG. 1, an image forming apparatus (color printer) 1 according to the present embodiment includes four image forming units 2a, 2b, 2c, and 2d, an intermediate transfer belt 3, and a fixing device arranged in parallel at regular intervals. 4. An exposure device (not shown), paper feed cassettes 5a and 5b, and a moisture applying device 6 for applying moisture to the recording paper (recording material) after fixing are provided (details of the moisture applying device 6 will be described later). To do).

  Each of the image forming units 2a, 2b, 2c, and 2d includes a photosensitive drum 7, a developing device 8, a charger (not shown), a cleaning device (not shown), and the like, and the image forming units 2a, 2b, Each of the developing devices 2c and 2d stores Y (yellow), C (cyan), M (magenta), and K (black) toners as developers. The intermediate transfer belt 3 is stretched by a driving roller 9a and a plurality of driven rollers 9b, 9c, 9d. In the fixing device 4, a heating roller 4a incorporating a heater 10 and a pressure roller 4b are in pressure contact with each other so as to be rotatable.

  During the image forming operation of the image forming apparatus 1, the surface of each photosensitive drum 7 of each of the image forming units 2 a, 2 b, 2 c, 2 d is charged by a charger (not shown) and converted into input image information. Accordingly, after exposure is performed by an exposure device (not shown) to form an electrostatic latent image, development is performed by the developing unit 8 so that toner images of each color (yellow, cyan, magenta, black) are transferred to the respective photoreceptors. Formed on the drum 7. The toner images on the photosensitive drums 7 are transferred (primary transfer) so that the toner images of the respective colors are sequentially superimposed on the intermediate transfer belt 3 that rotates in the direction of arrow a.

  Then, a recording sheet P such as a sheet transported to a transfer portion at a predetermined timing from one selected sheet feeding cassette 5a, 5b is carried on the intermediate transfer belt 3 by the secondary transfer roller 11. The full-color toner images are transferred (secondary transfer) all at once. The recording paper P to which the toner image has been transferred is conveyed to the fixing device 4 and heated and pressed at the nip portion between the heating roller 4a and the pressure roller 4b of the fixing device 4 so that the recording paper P is transferred onto the recording paper P. The toner image is heated and fixed. The recording paper P on which the toner image is heat-fixed by the fixing device 4 is discharged to the paper discharge tray 12 (or paper discharge tray 13).

  When forming images on both sides of the recording paper, after fixing the toner image on one side of the recording paper, the toner image is once transported to the reverse transport path (not shown) and then transported again to the transfer site. Then, the image is transferred and fixed on the other side and then discharged.

  Also, the image forming apparatus 1 of the present embodiment includes a moisture applying device 6 that applies moisture to the recording paper after fixing, and the recording paper when moisture is applied to the recording paper after fixing by the moisture applying device 6. A plurality of water vapor transport pipes 20a, 20b, 20c for transporting generated (evaporated) water vapor (heat), and condensers (heat exchangers) respectively connected to the outlet sides of the water vapor transport pipes 20a, 20b, 20c ) 21a, 21b, 21c, 21d.

  As shown in FIGS. 1 and 2, the moisture applying device 6 includes a pair of water applying rollers 22 a and 22 b disposed downstream of the fixing device 4 in the recording paper conveyance direction, a water tank 23 storing water W, and water. It has a water supply pipe 24 for supplying water from the tank 23 to the water applying rollers 22a and 22b, a pump 25 for adjusting the amount of water supplied, and a valve (not shown).

  At least the surface side of the water applying rollers 22a and 22b is formed of a sponge material that easily contains water, and the water supplying rollers 22a and 22b are connected to both sides of the water applying rollers 22a and 22b in the longitudinal direction from the water supply pipe 24 into the water applying rollers 22a and 22b. Water is supplied. The water applying rollers 22a and 22b are disposed so as to be in contact with each other on the downstream side of the fixing device 4 in the recording paper conveyance direction. A rotation drive mechanism (not shown) is connected to the pair of water applying rollers 22a and 22b and the heating roller 4a and the pressure roller 4b of the fixing device 4 so that both rollers rotate in synchronization. .

  The water vapor inlet side of the water vapor transport pipes 20a, 20b, 20c is provided downstream of the water application rollers 22a, 22b in the recording paper conveyance direction. Further, a pair of blocking rollers 26a and 26b for preventing water vapor leakage are provided on the recording paper discharge side near the water vapor inlet side of the water vapor transport pipes 20a, 20b and 20c so that water vapor does not leak from the water vapor inlet. Has been placed.

  The water vapor transport pipe 20 a is connected to condensers 21 a and 21 b provided near the paper feed cassettes 5 a and 5 b, and the water vapor transport pipe 20 b is connected to a condenser 21 c provided near the conveyance path between the fixing device 4 and the secondary transfer roller 11. The water vapor transport pipe 20c is connected to a condenser 21d provided in the vicinity of each image forming unit 2a, 2b, 2c, 2d. Further, the surroundings of the water vapor transport pipes 20a, 20b, 20c and the fixing device 4 are covered with a heat insulating material (not shown). This is because the heat of the high-temperature atmosphere being transported and the latent heat of the water vapor are not lost at the location before heat transport to the predetermined location, that is, the atmosphere containing the generated water vapor is below the dew point. This is to maintain the atmosphere at a high temperature and a high dew point so that the latent heat does not change to sensible heat.

  In the condensers 21 a, 21 b, 21 c, 21 d, a drain pipe 27 for collecting drainage is arranged so as to be integrated on the outlet side, and the drain pipe 27 is connected to a drain tank 28. An exhaust fan 29 for sucking and exhausting the drain pipe 27 is disposed on the upper portion of the drain tank 28 so as to be positioned on the lower side surface of the image forming apparatus 1.

  The first and second temperature / moisture sensors 30 and 31 are disposed between the fixing device 4 and the water applying rollers 22a and 22b in the image forming apparatus 1 and in the vicinity of the upstream side of the secondary transfer roller 11 in the recording paper conveyance direction. Are arranged, and a fixing temperature sensor 32 is arranged near the heating roller 4 a of the fixing device 4. An environmental temperature / humidity sensor 33 is disposed in the vicinity of the driving roller 9a in the image forming apparatus 1.

  The first temperature / moisture sensor 30 is the temperature and moisture density (water vapor density) on the front and back sides of the recording paper before entering the nip portion between the water application rollers 22a and 22b immediately after being discharged from the fixing device 4. , And a sensor that detects the atmospheric temperature and the atmospheric water vapor density in the vicinity of the recording paper. The recording paper immediately after being discharged from the fixing device 4 changes its temperature state rapidly and is heated by the heating roller 4a on one side, so that the temperature gradient is large, as shown in FIGS. It is preferable to detect the temperature and moisture density (water vapor density) on the front and back sides of the recording paper with two sensors arranged vertically opposite to each other. Moreover, the above-mentioned moisture density and water vapor density mean the difference between liquid (water) and gas (water vapor) states, the water density corresponds to the liquid (water) state, and the water vapor density is gas (water vapor). ).

  The second temperature / moisture sensor 31 includes a temperature and moisture density (water vapor density) on one side of the recording paper before the toner (toner image) is transferred to the conveyed recording paper, and an atmosphere in the vicinity of the recording paper. It is a sensor that detects temperature and atmospheric water vapor density. Note that the recording paper before the toner (toner image) is transferred has a small difference in temperature and moisture density (water vapor density) between the front side and the back side, so that one side (the toner image is transferred). It is only necessary to detect the temperature and water vapor density on the surface side.

  The fixing temperature sensor 32 is a well-known sensor that detects the temperature of the heating roller 4 a of the fixing device 4. The environmental temperature / humidity sensor 33 is a known sensor that detects the environmental temperature / humidity in the image forming apparatus 1.

  As the first and second temperature / moisture sensors 30 and 31, for example, the measuring means described in paragraphs [0074] to [0076], FIGS. 14 and 15 of Japanese Patent Application Laid-Open No. 2007-086054 are used. Can do. This measuring means is a sensor in which a temperature / humidity sensor and a flow sensor are formed integrally with a rectifying tube.

  Further, the image forming apparatus 1 has a control unit 34 for controlling the amount of water applied to the recording paper by the water applying rollers 22 a and 22 b and the amount of drainage by the exhaust fan 29. The control unit 34 detects the moisture content (water content) of the recording paper by the first and second temperature / moisture sensors 30 and 31 so that the moisture content (water content) becomes substantially the same before and after the fixing device 4 is heated and fixed. Based on the information, the drive power of the pump 25 and the drive power of the exhaust fan 29 are controlled.

  The reason why the moisture content of the recording paper is made substantially the same before and after the heat fixing with the fixing device 4 is that the moisture content of the recording paper decreases due to the heat fixing with the fixing device 4 and the curling occurs on the recording paper. This is to prevent this. When curl occurs on the recording paper, a conveyance failure such as a jam easily occurs.

  Further, in the storage unit (not shown) of the control unit 34, based on the sensor information detected by the first and second temperature / moisture sensors 30, 31, for example, as shown in FIG. Characteristics of the recording paper surface temperature a, the atmospheric temperature b, the atmospheric water vapor density c, and the water density (water vapor density) d of the recording paper before and after the heat fixing in the case where water is not applied to the recording paper after the heat fixing (hereinafter, referred to as the following) "Comparison reference characteristic") is stored.

This comparative reference characteristic is a characteristic based on a value measured by performing an image forming operation on the recording paper conveyed from the paper feed cassettes 5a and 5b. 3A and FIG. 3B and FIG. 9 described below, the left vertical axis is temperature (° C.), and the right vertical axis is moisture density (water vapor density) (g / m ³ ). It is a scale of saturated water vapor density (g / m ³ ) at 1 atm with respect to the temperature scale of the left vertical axis. The horizontal axis is the position of the recording paper to be conveyed, the right end is the position immediately before the transfer, A is the position at the time of heat fixing in the fixing device 4, and B is the position near the blocking rollers 26a and 26b behind the fixing device 4. Thus, the position between A and B is the position from the heat fixing to the blocking rollers 26a and 26b. That is, the horizontal axis in these figures indicates that the recording paper is conveyed from the right side to the left side in the figures, and the vicinity of the second temperature / moisture sensor 31 in FIG. 1 (recording on the secondary transfer roller 11). This corresponds to the recording paper conveyance section from the upstream side of the paper conveyance direction) to the vicinity of the blocking rollers 26a and 26b behind the fixing device 4.

  As shown in the comparative reference characteristic shown in FIG. 3A, the surface temperature a of the recording paper reaches about 120 ° C. at the time of heat fixing in the fixing device 4 and then decreases to about 55 ° C. near the blocking rollers 26a and 26b. It does not drop to about 25 ° C before transfer.

  In addition, the moisture content of the recording paper is evaporated into the atmosphere by heat fixing in the fixing device 4, and the moisture density (water vapor density) d of the recording paper is reduced, but the atmospheric water vapor density c is reduced by the moisture evaporated in the atmosphere. Will increase. At the same time, the heat of the recording paper is released to the atmosphere, and the ambient temperature b rises. Note that the ambient temperature b rises due to heat generated by the heater 10 just before heat fixing in the fixing device 4.

  In addition, in the comparative reference characteristic of FIG. 3A, the characteristic of the atmospheric temperature b shows the value on the left vertical axis, but when the characteristic of the atmospheric temperature b is applied to the water vapor density shown on the right vertical axis, Since the characteristic of the atmospheric temperature b is the characteristic of the saturated water vapor density of the atmosphere corresponding to that temperature, it can be seen that the atmospheric water vapor density c does not reach the saturated water vapor density of the atmosphere corresponding to the atmospheric temperature b. However, when this water vapor touches a low temperature part in the conveyance path away from the fixing device 4 where the ambient temperature b is lowered, the saturated water vapor density is exceeded. For this reason, the moisture content of the recording paper, which is evaporated into the atmosphere by heat fixing in the fixing device 4, may cause dew condensation to a low-temperature portion such as a conveyance path, which may cause a conveyance failure of the recording paper.

  For this reason, during the image forming operation, the high temperature atmosphere around the fixing device 4 including the fixing device 4 and the waste heat of water vapor are used as regeneration energy, and at the same time, cooling by applying moisture to the recording paper after heating and fixing. It is desirable to recover the moisture content (water content) of the recording paper. That is, for example, as shown in FIG. 3B, after the toner image is heated and fixed on the recording paper by the fixing device 4, the surface temperature a of the recording paper near the blocking rollers 26a and 26b, the ambient temperature b, To recording paper after heat-fixing to obtain characteristics (hereinafter referred to as “first control characteristics”) such that the atmospheric water vapor density c and the water density (water vapor density) d of the recording paper are substantially the same as those immediately before transfer. It is necessary to perform the moisture application control (that is, the driving power control of the pump 25) and the rotation control of the exhaust fan 29 (that is, the driving power control of the exhaust fan 29). In FIG. 3B, the position C on the horizontal axis is a position where moisture is applied to the recording paper.

  Therefore, in the storage unit (not shown) of the control unit 34, the first reference characteristic shown in FIG. 3B and the first control characteristic obtained in the experiment, etc., as well as the comparative reference characteristic shown in FIG. The drive power value to the pump 25 and the drive power value to the exhaust fan 29 to be obtained are also stored, and the control unit 34 performs moisture application control to the recording paper after heat fixing and rotation control of the exhaust fan 29. The first control characteristic shown in FIG. 3B is obtained.

  Next, a process for obtaining the first control characteristic of FIG. 3B will be described with reference to the flowchart shown in FIG.

  Before starting the fixing operation at the time of the image forming operation of the image forming apparatus 1, the heater 10 in the heating roller 4a of the fixing device 4 is energized to raise the temperature of the heating roller 4a to a predetermined temperature (step S1). Then, in order to keep the thermal balance around the fixing device 4, a motor (not shown) of the exhaust fan 29 is rotationally driven to rotate the exhaust fan 29 at a predetermined rotational speed (step S2). Then, the recording paper onto which the toner image has been transferred is conveyed to the fixing device 4, and the toner image is heated and fixed on the recording paper at the nip portion between the heating roller 4a and the pressure roller 4b.

  The second temperature / moisture sensor 31 detects the surface temperature, the atmospheric temperature, the atmospheric water vapor density, and the water density (water vapor density) of the recording paper before the toner image is transferred, The temperature / moisture sensor 30 detects the surface temperature, the atmospheric temperature, the atmospheric water vapor density, and the water density (water vapor density) of the recording paper after the toner image is heat-fixed (steps S3 and S4).

  The sensor information of the recording paper, the temperature of the recording paper, the atmosphere temperature, and the water vapor density detected in steps S3 and S4 is input to the control unit 34. The control unit 34 calculates the amount of moisture applied to the recording paper in which the moisture content has evaporated based on the input sensor information and the stored first control characteristics, and further, the amount of moisture applied to the recording paper. An appropriate exhaust flow rate due to the rotation of the exhaust fan 29 corresponding to is calculated (step S5).

  Then, the control unit 34 controls the driving power of the pump 25 so that the calculated moisture application amount is applied to the recording paper, and the water application roller 22a from the water tank 23 through the valve (not shown) and the water supply pipe 24. , 22b is supplied with a predetermined amount of water (step S6). At position C, moisture is applied to the recording paper that passes through the nip portion between the water applying rollers 22a and 22b. Further, the control unit 34 controls the driving power of the exhaust fan 29 so that the calculated exhaust flow rate is obtained, and rotates the exhaust fan 29 at a predetermined rotational speed (a rotational speed faster than that in step S2). (Step S7).

  Then, the recording paper that has been given water and cooled is discharged to the outside through a pair of rotatable blocking rollers 26a and 26b that are in contact with each other.

  As in the first control characteristic shown in FIG. 3B, after the surface temperature a of the recording paper reaches about 120 ° C. at the time of heat fixing in the fixing device 4, moisture is applied to the recording paper, and the blocking roller 26a. , 26b, the temperature is lowered to about 25 ° C. before transfer.

  Further, the moisture content of the recording paper is evaporated into the atmosphere by heat fixing in the fixing device 4 and the moisture content of the recording paper is reduced. However, the moisture is given to the recording paper and the vicinity of the blocking rollers 26a and 26b. With this, the water content before transfer is almost recovered. Further, the heat of the recording paper is also released to the atmosphere, and the ambient temperature rises. However, moisture is applied to the recording paper, and the ambient temperature before the transfer is substantially recovered in the vicinity of the blocking rollers 26a and 26b. Note that the ambient temperature b rises due to heat generated by the heater 10 just before heat fixing in the fixing device 4, but in the case of the comparative reference characteristic of FIG. 3A due to appropriate exhaust by rotation of the exhaust fan 29. Is lower than.

  Further, the moisture content of the recording paper is released, and further, moisture is added to the recording paper, so that the atmospheric water vapor density c increases as compared with the comparative reference characteristic of FIG.

  In addition, the larger the atmospheric water vapor density, the greater the amount of exhaust heat that can be collected. On the other hand, the amount of water vapor that exceeds the saturated water vapor density of the atmosphere aggregates and the latent heat becomes sensible heat, making it unsuitable for collecting heat. Accordingly, since the saturated water vapor amount of the atmosphere is determined by the atmospheric temperature detected by the first temperature / moisture sensor 30, the saturated water vapor density indicated by the atmospheric temperature is set as the upper limit, and the saturated water vapor density is made smaller. Therefore, the latent heat of water vapor and the sensible heat of the atmosphere generated in the region D1 indicated by the oblique lines of the first control characteristic in FIG. 3B are collected and used for exhaust heat utilization.

  Then, the water vapor evaporated by applying moisture to the recording paper and the exhaust heat of the high-temperature atmosphere around the fixing device 4 including the fixing device 4 are exhausted by the rotation of the exhaust fan 29, and the water vapor transport pipes 20a and 20b. , 20c to the respective condensers 21a, 21b, 21c, 21d. Each condenser 21a, 21b, 21c, 21d changes the latent heat of the transported water vapor into sensible heat, and also adds exhaust heat from a high-temperature atmosphere to dissipate heat to the surroundings.

  Due to the heat radiation from the condensers 21a and 21b, the humidity of the recording paper stored in the paper feed cassettes 5a and 5b and the heat radiation from the condenser 21c to the heater 10 in the heating roller 4a by preheating the recording paper. The toner in each developing device 8 can be conditioned by reducing the amount of electric power and further by releasing heat from the condenser 21d. Drainage discharged from each condenser 21a, 21b, 21c, 21d is stored in a drainage tank 28 through a drainage pipe 27.

  As described above, the image forming apparatus 1 according to the present embodiment can effectively cool the recording sheet by applying moisture to the recording sheet after being heated and fixed, thereby preventing the recording sheet from being curled. Can be discharged well. Further, when moisture is applied to the recording paper after heat fixing, the water vapor evaporated and the exhaust heat of the high-temperature atmosphere around the fixing device 4 including the fixing device 4 are efficiently collected to control the humidity of the recording paper. Further, since it can be used for preheating before fixing the recording paper, adjusting the humidity of the toner, etc., it is possible to further improve the exhaust heat utilization efficiency.

  Conventionally, the adsorbed moisture is released from the surface of the recording paper by heat fixing and may cause condensation in the apparatus. However, the adsorbed moisture released from the surface of the recording paper is also simultaneously supplied to the condensers 21a, 21b, 21c, Since it is sent to 21d, it becomes unnecessary to deal with condensation.

  In the image forming apparatus 1, the sensor output from the environmental temperature / humidity sensor 33 that detects the environmental temperature / humidity in the image forming apparatus 1 can be used instead of the second temperature / moisture sensor 31. is there. Further, since the first temperature / moisture sensor 30 detects the temperature of the recording paper after heat fixing, the temperature of the recording paper has a correlation with the surface temperature of the heating roller 4a. Therefore, the sensor output from the fixing temperature sensor 32 can be used instead of the first temperature / moisture sensor 30.

<Embodiment 2>
FIG. 5 is a schematic view showing the vicinity of the fixing device of the image forming apparatus according to Embodiment 2 of the present invention. In the first embodiment, the pair of water applying rollers 22a and 22b is arranged on the downstream side of the fixing device 4 in the recording paper conveyance direction. However, in the present embodiment, the water discharge heads 40 and 41 arranged to face each other vertically. It is the structure which arranged. The water discharge heads 40 and 41 have the same configuration except that the top and bottom are reversed. In the present embodiment, one water discharge head 40 will be described. Other configurations are the same as those of the image forming apparatus according to the first embodiment, and members having the same functions are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIGS. 6A and 6B, the water discharge head 40 is provided with liquid chambers 43 a and 43 b on both sides of a water flow path 43 formed in the head main body 42. The other end side of the water supply pipe 24 connected to the water tank 23 is connected to the water inlet 43 a of the water flow path 43. In FIG. 5, the water supply pipe connected to the other water discharge head 41 side is not shown. In FIGS. 6A and 6B, the arrow a indicates the recording paper conveyance direction.

  A plurality of water applying nozzles 44 are formed on one surface of the head main body 42 (the surface on the side where the recording paper is conveyed) so as to communicate with the liquid chambers 43a and 43b. In addition, piezoelectric plates 45 a and 45 b for discharging water supplied to the liquid chambers 43 a and 43 b as water droplets from the water applying nozzles 44 are disposed on the other surface of the head main body 42. Third and fourth temperature / moisture sensors 46 and 47 are arranged on one surface of the head main body 42 (the surface on the side where the recording paper is conveyed).

  The third and fourth temperature / moisture sensors 46 and 47 are configured in the same manner as the first temperature / moisture sensor 30 of the first embodiment. Further, as the third and fourth temperature / moisture sensors 46 and 47, for example, the recording paper of the head main body 42 is conveyed using the atmosphere detection device described in Japanese Patent No. 3331070, paragraph [0029] and FIG. And the surface temperature of the recording paper after the toner image has been heat-fixed, the ambient temperature, and the like, by being driven by the driving method described in paragraphs [0015] to [0027]. The atmospheric water vapor density and the moisture density (water vapor density) of the recording paper can be detected.

  As shown in FIG. 6B, the third temperature / moisture sensor 46 is arranged on the upstream side of the liquid chamber 43a with respect to the recording paper conveyance direction a, and the fourth temperature / moisture sensor 47 is Further, it is disposed upstream of the liquid chamber 43b with respect to the recording paper transport direction a. A plurality of third and fourth temperature / moisture sensors 46 and 47 are provided along the recording paper width direction (vertical direction in FIG. 6B). In FIG. 6B, the central portion along the recording paper transport direction a of one surface of the head main body 42 (the surface on the side where the recording paper is transported) is omitted.

  The water application nozzles 44 in the liquid chamber 43a and the water application nozzles 44 in the liquid chamber 43b are arranged at a predetermined interval in the recording paper width direction (vertical direction in FIG. 6B) and with respect to the recording paper conveyance direction a. Are arranged in two rows. The water application nozzles 44 in each row are arranged so that their positions are shifted from each other, and the adjacent water application nozzles 44 in each row are arranged at the apex position of an equilateral triangle.

  Since the respective water applying nozzles 44 are arranged as described above, for example, as shown in FIG. 6A, a voltage is applied to the piezoelectric plates 45a and 45b of the upper water discharge head 40 so that each liquid chamber 43a, By pressurizing 43 b, water droplets Wd are discharged from each water application nozzle 44. At this time, when the heat-fixed recording paper is conveyed so as to pass through the lower surface side of the water ejection head 40, as shown in the conveyance process in the order of FIGS. 7 (a), (b), and (c), Water droplets (moisture) Wd are applied onto the recording paper P at predetermined intervals, and penetrate into the recording paper P. In FIGS. 7A, 7B, and 7C, the arrow a indicates the recording paper conveyance direction. E is a moisture permeation area that has penetrated into the recording paper P, and water vapor is released from the moisture penetration area E as the recording paper P is conveyed.

  7A and 7B show a state in which water droplets Wd are applied onto the recording paper P from the respective water application nozzles 44 in the liquid chamber 43a, and FIG. 7C shows each water application in the liquid chamber 43a. In this state, water droplets Wd are applied to the recording paper P from the water application nozzles 44 of the nozzle 44 and the liquid chamber 43b. Note that the water droplets Wd on the left side of the recording paper P in FIG. 7C are water droplets ejected from the water application nozzles 44 in the liquid chamber 43b. When the water droplet Wd is applied on the recording paper P, the water spreads while penetrating into the recording paper P, and then evaporates while generating water vapor.

  FIG. 8 is a view showing a state in which the recording paper P to which the water droplet Wd of FIG. 7C is applied is viewed from the front side. The arrow a is the recording paper conveyance direction.

  In FIG. 8, the water droplet Wd has a diameter of about 80 μm, for example, and a concentric circle indicated by a two-dot chain line around the water drop Wd has a permeation spread range of about 300 μm in diameter. In FIG. 8, E is a moisture permeation region that has penetrated into the recording paper P. In this embodiment, the arrangement intervals of the water application nozzles 44 are set so that the permeation spread ranges of the water drops Wd applied on the recording paper P from the water application nozzles 44 do not overlap. Control is performed so that the discharge timing from each water application nozzle 44 and the conveyance speed of the recording paper P are synchronized.

  In this way, by preventing the permeation spread ranges of the water droplets Wd applied on the recording paper P from the water application nozzles 44 from overlapping each other, each water droplet is released when the water vapor inside the recording paper P is released to the outside. Since water vapor is also released from the gaps in the range where W penetrates and spreads, it is possible to efficiently release water vapor. In addition, if the permeation spread range of the water droplet Wd is larger than the fiber length that maintains the strength of the recording paper P, expansion and contraction of the recording paper size occurs. In order to prevent water from being applied at once, the water 44 is dried by the nozzle 44 of the liquid chamber 43a, the degree of drying of the water droplet Wd is detected by the fourth temperature / moisture sensor 47, and the water droplet Wd from the nozzle 44 of the liquid chamber 43b is detected. Is provided on the recording paper P, the permeation spread range can be adjusted appropriately.

  Further, in the present embodiment, the storage unit (not shown) of the control unit 34 includes the second reference characteristic of FIG. 9 obtained through experiments and the like, as well as the comparative reference characteristic of FIG. The drive power value to the pump 25 and the drive power value to the exhaust fan 29 for obtaining the characteristics are also stored, and the control unit 34 controls the moisture application to the recording paper after heat fixing (that is, the drive of the pump 25). Power control) and rotation control of the exhaust fan 29 (that is, drive power control of the exhaust fan 29) are performed so that the second control characteristic of FIG. 9 is obtained.

  The second control characteristic of FIG. 9 is that after the toner image is heated and fixed on the recording paper by the fixing device 4, the surface temperature a, the atmospheric temperature b, the atmospheric water vapor density c in the vicinity of the blocking rollers 26a and 26b, The characteristic is that the moisture density (water vapor density) d of the recording paper is substantially the same as that immediately before the transfer. In FIG. 9, the horizontal axis is the position of the recording paper to be conveyed, the right end is the position immediately before the transfer, A is the position at the time of heat fixing in the fixing device 4, and B is the blocking roller behind the fixing device 4. 26a and 26b, a position C1 is a position where moisture is first applied to the recording paper by applying a voltage to the piezoelectric plate 45a, and a position C2 is a position where moisture is applied to the recording paper by applying a voltage to the piezoelectric plate 45b. It is.

  Next, processing for obtaining the second control characteristic of FIG. 9 will be described with reference to the flowchart shown in FIG.

  Before starting the fixing operation during the image forming operation of the image forming apparatus 1, the heater 10 in the heating roller 4a of the fixing device 4 is energized to increase the temperature of the heating roller 4a to a predetermined temperature (step S11). Then, in order to maintain the thermal balance around the fixing device 4, the motor (not shown) of the exhaust fan 29 (see FIG. 1) is rotationally driven to rotate the exhaust fan 29 at a predetermined rotational speed (step S12). Then, the recording paper onto which the toner image has been transferred is conveyed to the fixing device 4, and the toner image is heated and fixed on the recording paper at the nip portion between the heating roller 4a and the pressure roller 4b.

  The second temperature / moisture sensor 31 detects the surface temperature of the recording paper, the ambient temperature, the atmospheric water vapor density, and the moisture density (water vapor density) of the recording paper before the toner image is transferred, and then at the position C1. The third temperature / moisture sensor 46 detects the surface temperature, the atmospheric temperature, the atmospheric water vapor density, and the water density (water vapor density) of the recording paper after the toner image is heat-fixed (steps S13 and S14). ).

  The sensor information of the recording paper, the ambient temperature, and the water vapor density before and after the transfer and detected at steps S13 and S14 is input to the controller 34. The control unit 34 calculates the amount of moisture applied to the recording paper in which the moisture content has evaporated based on the input sensor information and the stored second control characteristics, and further, the amount of moisture applied to the recording paper. An appropriate exhaust flow rate due to the rotation of the exhaust fan 29 corresponding to is calculated (step S15).

  Then, the control unit 34 controls the driving power of the pump 25 so that the calculated moisture application amount is applied to the recording paper, and the water discharge head 40 is supplied from the water tank 23 through a valve (not shown) and the water supply pipe 24. , 41 is supplied with a predetermined amount of water (step S16). Then, by applying a voltage to one piezoelectric plate 45a and pressurizing the liquid chamber 43a, water droplets are discharged from each of the water application nozzles 44 only on the liquid chamber 43a side, and at the position C1, the water discharge heads 40 and 41 Moisture is applied to the recording paper passing between them (step S16). Further, the control unit 34 controls the driving power of the exhaust fan 29 so that the calculated exhaust flow rate is obtained, and rotates the exhaust fan 29 at a predetermined rotational speed (a rotational speed faster than that in step S12). (Step S17).

  By the way, when the recording paper is a thick paper or a resin sheet having a large heat capacity, the temperature drop of the recording paper may be small only by applying moisture at step S16, or a lot of moisture may not be applied at one time.

  Therefore, in the present embodiment, the surface temperature, the atmospheric temperature, the atmospheric water vapor density, and the water density (water vapor density) of the recording paper after the moisture is applied in step S16 by the fourth temperature / moisture sensor 47. Is detected (step S18). The control unit 34 calculates an additional water application amount to be applied to the recording paper based on the input sensor information and the stored second control characteristics, and further according to the additional water application amount. An appropriate exhaust flow rate due to the rotation of the exhaust fan 29 is calculated (step S19). The additional moisture application amount is smaller than the moisture application amount calculated in step S15.

  Then, the control unit 34 controls the drive power of the pump 25 so that the calculated additional water application amount is applied to the recording paper, and the water flow of the water discharge heads 40 and 41 from the water tank 23 through the water supply pipe 24. A predetermined amount of water is supplied to the path 43 (step S20). Then, by applying a voltage to the other piezoelectric plate 45b to pressurize the liquid chamber 43b, water droplets are discharged from each water application nozzle 44 only on the liquid chamber 43b side, and at the position C2, the water discharge heads 40, 41 Moisture is given to the recording paper passing between them.

  Further, the control unit 34 controls the drive power to the exhaust fan 29 so as to obtain the calculated exhaust flow rate, and rotates the exhaust fan 29 at a predetermined rotational speed (slower rotational speed than in step S19). (Step S21).

  Then, the recording paper that has been given water and cooled is discharged to the outside through a pair of rotatable blocking rollers 26a and 26b that are in contact with each other.

  Further, the water vapor evaporated by applying the moisture to the recording paper in two steps and the exhaust heat of the high temperature atmosphere around the fixing device 4 including the fixing device 4 are exhausted by the rotation of the exhaust fan 29. As in the first embodiment, they are sent to the condensers 21c and 21d (condensers 21a and 21b are not shown) through the water vapor transport pipes 20a, 20b and 20c, respectively. Each condenser 21a, 21b, 21c, 21d changes the latent heat of the transported water vapor into sensible heat, and also adds exhaust heat from a high-temperature atmosphere to dissipate heat to the surroundings.

  Note that the larger the atmospheric water vapor density, the greater the amount of exhaust heat that can be collected. On the other hand, the amount of water vapor above the saturated water vapor density of the atmosphere aggregates and the latent heat becomes sensible heat, making it unsuitable for collecting heat. Therefore, since the saturated water vapor amount of the atmosphere is determined by the atmospheric temperature detected by the third and fourth temperature / moisture sensors 46 and 47, the saturated water vapor density indicated by the atmospheric temperature is set as the upper limit, and less than the saturated water vapor density. To be. Therefore, the latent heat of water vapor and the sensible heat of the atmosphere generated in the region D2 indicated by the oblique lines of the second control characteristic in FIG. 9 are collected and used for exhaust heat utilization.

  As described above, also in this embodiment, when moisture is applied to the recording paper after heat fixing, the water vapor evaporated from the recording paper and the exhaust heat of the high-temperature atmosphere around the fixing device 4 including the fixing device 4 are removed. Since it can be efficiently collected and used for humidity control of the recording paper, preheating before fixing the recording paper, toner humidity control, etc., it is possible to increase the efficiency of exhaust heat utilization.

  Further, in the present embodiment, moisture can be applied to the recording paper twice based on sensor outputs from the third and fourth temperature / moisture sensors 46 and 47, so that the recording paper has a large heat capacity such as thick paper or resin. In the case of a sheet or the like, appropriate moisture can be applied to the recording paper even when the temperature drop of the recording paper is small only by applying moisture in step S16 or when a large amount of moisture cannot be applied at once.

<Embodiment 3>
FIG. 11 is a schematic view showing the vicinity of the fixing device of the image forming apparatus according to Embodiment 3 of the present invention.

  In the second embodiment shown in FIG. 5, moisture is applied to the recording paper thermally fixed from the water discharge heads 40 and 41 provided on the downstream side of the fixing device water 4, the water vapor evaporated from the recording paper, and the fixing device 4, the exhaust heat of the high-temperature atmosphere around the fixing device 4 including 4 is sent to the condenser through the water vapor transport pipe. In the present embodiment, as shown in FIG. Water is applied to the recording paper P thermally fixed from the water discharge heads 40 and 41 provided in the apparatus, and water vapor evaporated from the recording paper P and exhaust heat of the high-temperature atmosphere around the fixing device 4 including the fixing device 4 are discharged. Is supplied to the heat exchanger 48 using the Seebeck effect or the like through the water vapor transport pipe 20, and the water vapor and the exhaust heat are converted into electric power for reuse. The other basic configuration is the same as that of the second embodiment shown in FIG.

  The periphery of the fixing device 4 including the fixing device 4 is covered with a heat insulating container 49 so that the water vapor evaporated from the recording paper P and the exhaust heat of the high temperature atmosphere around the fixing device 4 including the fixing device 4 do not escape to the outside. To the heat exchanger 48 side. If the electric power obtained by the heat exchanger 48 is regenerated, for example, to a power supply unit (not shown) in the image forming apparatus, the power consumption of the image forming apparatus can be reduced. The heat exchanger 48 is installed in a container 50 having high heat insulating properties. Note that the atmosphere in the container 50 is discharged to the outside by the exhaust fan 51.

  Further, a condenser 52 is disposed inside the heat exchanger 48, and the condenser 52 converts the latent heat of the water vapor transported through the water vapor transport pipe 20 into sensible heat, and further exhausts heat from a high temperature atmosphere. In addition, by dissipating heat around it, it can be used for humidity control of recording paper, preheating before fixing the recording paper, humidity control of toner, and the like. On the downstream side of the condenser 52, a drainage tank 53 for collecting drainage is disposed.

  As described above, in the present embodiment, the water vapor evaporated from the recording paper P and the exhaust heat of the high-temperature atmosphere around the fixing device 4 including the fixing device 4 are converted into electric power by the heat exchanger 48 to generate electric power. Can be reused.

<Embodiment 4>
FIG. 12 is a schematic view showing the vicinity of the fixing device of the image forming apparatus according to Embodiment 4 of the present invention.

  In the image forming apparatus according to the second embodiment, water is supplied from the water tank 23 to the water discharge heads 40 and 41 through the water supply pipe 24. However, in this embodiment, as shown in FIG. A mixed water containing a brightener and a transparent agent for imparting glossiness and recording paper strength to the toner image on the paper is supplied to the water discharge heads 40 and 41 by a switching valve (not shown). Other configurations are the same as those of the image forming apparatus according to the third embodiment, and redundant description is omitted.

  As shown in FIG. 12, it has the water tank 23 which stored the water W, and the mixed water tank 54 which stored the mixed water S, and water and mixed water are water discharge head 40 through each water supply pipe | tube 24a, 24b. , 41. Between each water supply pipe 24a, 24b, the water tank 23, and the mixed water tank 54, the switching valve part (not shown) for selecting and supplying to either one is provided. The control unit 34 controls the driving power of the pump 25, and the water discharge head passes through the water supply pipe on the side of the selected one of the water in the water tank 23 or the mixed water in the mixed water tank 52 by a switching valve (not shown). 40 and 41 are supplied.

  When using a transparent agent with low heat resistance that dissolves or changes quality due to temperature rise during fixing, for example, during double-sided image formation operation, moisture is applied to the recording paper surface after fixing the toner image on the recording paper surface. Then, after fixing the toner image on the back surface of the recording paper, water is applied to both surfaces of the recording paper and mixed water containing a transparent agent is sequentially applied.

  As described above, in the present embodiment, since the mixed water containing a brightening agent, a transparent agent, and the like can be applied to the recording paper after heat fixing in addition to the provision of moisture, the toner image fixed on the recording paper can be easily glossed. And the strength of the recording paper can be easily increased. Further, when the glossiness is imparted to the toner image, as shown in FIG. 8, when water droplets containing a transparent agent are imparted to the surface of the recording paper, they are arranged in a minute dot pattern with a gap on the surface of the recording paper. Therefore, when the recording paper surface is coated in a film shape without a gap, the gloss of the transparent agent becomes difficult to visually recognize the image (toner image) due to the reflection of the surface. However, in the above-described embodiment, non-glare transmission is possible. A high quality image (toner image) can be obtained.

  In addition, as shown in FIG. 12, an ion generating electrode 55 is installed near the water vapor transport pipe 20 in the heat insulating container 49, and a high voltage is applied to the ion generating electrode 55 to cause ions in the heat insulating container 49. By generating, ozone and NOx generated by the developing device in the image forming apparatus, which has absorbed the atmosphere outside the fixing device 4 from the opening portion of the heat insulating container 49, is decomposed. It is possible to neutralize the adsorption odor and the like of the recording paper generated when the toner image is thermally fixed.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Intermediate transfer belt 7 Photosensitive drum 4 Fixing device 4a Heating roller 4b Pressure roller 6 Moisture applying device 20a, 20b, 20c Water vapor transport pipes 21a, 21b, 21c, 21d Condenser 22a, 22b Water applying roller 30 First temperature / moisture sensor 31 Second temperature / moisture sensor 34 Control unit 40, 41 Water discharge head 44 Water application nozzle 45a, 45b Piezoelectric plate 46 Third temperature / moisture sensor 47 Fourth temperature / moisture sensor 48 Heat exchanger 55 Ion generating electrode

JP 2003-233227 A

Claims (8)

In an image forming apparatus having a fixing unit that heats and fixes an unfixed image on a recording material with respect to an unfixed image formed on the recording material by an image forming unit.
A moisture applying unit that applies moisture to a recording material that has been heated and fixed by an unfixed image on the downstream side of the fixing unit in the recording material conveyance direction, and whose temperature has risen;
A high-temperature gas containing water vapor evaporating from the recording material after moisture is applied by the moisture applying unit, and a high-temperature atmosphere around the fixing unit including the fixing unit are collected, and humidity control or adjustment in the image forming apparatus is performed. A heat transport path for transporting to a predetermined location for heating;
An image forming apparatus comprising: a heat exchanger disposed at an outlet of the heat transport path.   The predetermined portion is at least one of the vicinity of a paper feeding unit in which a plurality of recording materials are stored in a stacked state, the vicinity of a developing unit of the image forming unit, and the vicinity of a conveyance path upstream of the fixing unit in the recording material conveyance direction. The image forming apparatus according to claim 1, wherein: A sensor for detecting the temperature and water vapor density of the atmosphere in the recording material and the image forming apparatus, which is disposed at least near the downstream side in the recording material conveyance direction of the fixing unit and upstream in the recording material conveyance direction of the fixing unit; An exhaust means disposed on the downstream side of the heat exchanger, a moisture application amount adjusting means for adjusting the moisture application amount provided to the recording material, provided in the moisture application means, and an exhaust flow rate of the exhaust means And a control means for controlling the amount of moisture applied by the moisture content adjusting means,
The control means, based on the sensor information detected by the sensor, the exhaust means and the moisture application amount adjusting means so that the water vapor density does not exceed the saturated water vapor density and the water vapor density becomes the maximum amount. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled.   4. The image forming apparatus according to claim 3, wherein after the control by the control unit is performed once, the control unit performs the control again based on sensor information detected by the sensor. The water applying unit has a plurality of discharge ports disposed near the downstream side of the fixing unit in the recording material conveyance direction, and has a plurality of discharge ports for discharging water droplets to at least one surface of the recording material after fixing. Have a head,
After the water droplets ejected from the plurality of ejection ports are applied to the surface of the recording material, at least the plurality of ejection ports so that the ranges of the adjacent water droplets that permeate and spread into the recording material do not overlap. 5. The image forming apparatus according to claim 1, wherein any one of an arrangement interval, a number of the discharge ports, and a discharge amount from the discharge ports is optimally set.   6. The image forming apparatus according to claim 1, further comprising a thermoelectric exchanger capable of converting heat into electric power in the vicinity of the heat exchanger.   7. The method according to claim 1, wherein the moisture applying unit applies water containing at least one of a transparent agent and a brightener to the recording material in addition to water. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein an ion generating electrode that generates ions by applying a high voltage is provided in the vicinity of the downstream side of the fixing unit in the recording material conveyance direction.

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