JP5077191B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a fixing unit that heats and fixes an unfixed image formed using a liquid developer and transferred onto a recording medium. The present invention relates to an image forming apparatus having means for recovering the solvent of the agent.

  2. Description of the Related Art An electrophotographic image forming apparatus that forms an electrostatic latent image on a photoconductor (photosensitive drum), adheres toner to the image, and transfers and fixes the image on paper or the like is widely used. In particular, in an image forming apparatus that requires higher image quality and higher resolution, such as an office printer for large-scale printing and an on-demand printing apparatus, a wet process using a liquid developer that has a small toner particle diameter and is less likely to cause toner image disturbance. Development methods are being used.

  In recent years, an image using a high-viscosity and high-concentration liquid developer, which is composed by dispersing toner as a solid content composed of a resin and a pigment in an insulating liquid “carrier liquid” such as silicone oil at a high concentration. Forming devices have been proposed.

  When developing using this liquid developer, a thin layer of developer is formed on a developer carrier such as a developing roller, and the thinned developer is brought into contact with the photoreceptor. It is common to develop.

  The latent image on the surface of the photoreceptor is developed with a thin layer of liquid developer, and a toner image is formed on the surface of the photoreceptor. This toner image is transferred to a recording medium. Alternatively, the toner image is first temporarily transferred to an intermediate transfer member or the like and then secondarily transferred to a recording medium.

  The toner image transferred to the recording medium is fixed on the recording medium, which is usually paper, by being pressurized and heated by a fixing device. However, a toner image is originally developed using a liquid developer in which toner is dispersed in a carrier liquid as a solvent, and a solvent (hereinafter also referred to as a carrier liquid) is used not only between toners but also between toners and between toner papers. )It is included. Moreover, it has a fairly high viscosity.

  It is known that the presence of a high-viscosity carrier liquid hinders fixability during toner image fixing. For example, since the toner image and the recording medium are wet with the carrier liquid, the fixability of the toner image is lowered, and the image may be crushed or disturbed during pressure fixing.

  On the other hand, a technique for efficiently removing a solvent (carrier liquid) from an unfixed toner image at the time of fixing has been developed. For example, a technique has been proposed in which more carrier liquid is volatilized from an unfixed toner image by increasing the nip width of heat fixing or preheating before fixing.

  However, even if a technique for efficiently vaporizing the solvent with less heat energy is developed, there is a problem in that the evaporated carrier liquid is released into the atmosphere as it is. These solvent gases may contain a small amount of VOC (volatile organic compound), which may adversely affect people and the environment.

  From the viewpoint of safety, it is necessary to prepare a system for collecting and treating the volatile solvent. Such a technique has also been developed (see, for example, Patent Documents 1 and 2).

  Patent Document 1 proposes a technique for removing solvent gas by introducing solvent gas generated in the machine into the purification chamber and circulating the solvent through the purification chamber so that the filter gas is passed many times.

  Patent Document 2 includes an oxidation catalyst unit in an image forming apparatus, a duct that guides carrier vapor generated in the fixing unit to the oxidation catalyst unit, and a suction fan, and controls the speed of the suction fan in accordance with data. Techniques for performing are presented.

  However, these techniques have no idea of recovering and reusing the carrier liquid. For example, in the method of collecting vapor with a filter, even if it can be collected, it is difficult to easily desorb, recover and circulate the carrier liquid. Also, in the method using an oxidation catalyst, the carrier liquid itself is decomposed, so that it cannot be reused.

  A technique that removes the solvent vapor and can be reused as much as possible has been desired and developed. For example, Patent Document 3 discloses a technique for providing a path for circulating the solvent gas generated in the machine, arranging a cooling-type recovery device, performing a recovery process, and then heating the exhaust gas having a reduced concentration to return it to the fixing unit. Proposed.

In consideration of recovery and reuse of carrier liquid vapor, a cooling type solvent recovery apparatus is desirable in this way. The vapor generated in the fixing device or the like is led to a solvent recovery device by a duct or the like, and cooled to be liquefied. The carrier liquid liquefied with the water vapor in the air can be reused as the carrier liquid after separation from water.
JP-A-8-334984 JP 2005-316366 A JP-A-9-204121

  As described above, in consideration of the reuse of the carrier liquid as the solvent, a technique for cooling and recovering the carrier liquid vapor that volatilized during fixing is preferable. However, it is necessary to cool the entire air including the carrier liquid vapor, and considering the size of the apparatus, power consumption, and generation of frost, the cooling temperature is almost limited to around 0 ° C. Accordingly, a vapor having a concentration corresponding to the saturated vapor pressure at that temperature remains without being liquefied and is contained in the exhaust gas in a small amount.

  There is no problem with the VOC concentration in the exhaust, but if exhaust is continuously performed in a closed space, there is a possibility that the accumulated VOC may adversely affect people and the environment. Therefore, a processing technique for a solvent recovery apparatus that can suppress the total discharge amount of VOC is desired.

  The object of the present invention is to solve the above-mentioned problems, and to control the vapor concentration in the exhaust gas from the solvent recovery device and recover the exhaust gas from the solvent device when recovering and reusing the solvent vapor volatilized in the fixing device or the like. An object of the present invention is to provide an image forming apparatus capable of reducing the amount itself and suppressing the total discharge amount of solvent vapor.

  In order to solve the above problems, the present invention has the following features.

1. A fixing unit that heats and fixes an unfixed image formed using a liquid developer in which toner is dispersed in a solvent and transferred onto the recording medium, and surrounds the fixing unit, and is volatilized from the recording medium by the fixing unit. A solvent storage means for temporarily storing the solvent vapor, a solvent recovery means for cooling the solvent vapor and recovering it as a liquid solvent, and a solvent vapor stored in the solvent storage means. And a solvent transfer means for transferring the solvent storage means together with the air in the solvent storage means to the solvent recovery means, and detecting the concentration of the vapor of the solvent stored in the solvent storage means And a transfer adjusting means for adjusting the transfer amount of the solvent vapor by the solvent transferring means based on the concentration detected by the concentration detecting means, the transfer adjusting means comprising: A constant reference concentration is compared with the concentration detected by the concentration detecting means, and the transfer amount is increased if the detected concentration exceeds the predetermined reference concentration, and the transfer amount is decreased if the detected concentration is lower than the predetermined reference concentration. Adjusting the amount of the solvent vapor transferred by the solvent transfer means, and having a temperature detection means for detecting the ambient temperature in the solvent storage means, the predetermined reference concentration is a temperature detected by the temperature detection means An image forming apparatus characterized by being determined in accordance with a saturated vapor concentration of the solvent .

2. The transfer adjusting means transfers the solvent by a predetermined transfer amount when the concentration detected by the concentration detection means exceeds the predetermined reference concentration, and stops the transfer when the concentration is lower than the predetermined reference concentration. 2. The image forming apparatus according to 1, wherein the amount of vapor transferred is adjusted .

3. 3. The image forming apparatus according to 2, wherein the predetermined reference concentration is set to 50% or more and 90% or less of the saturated vapor concentration of the solvent at the temperature detected by the temperature detecting unit .

4). A fixing unit that heats and fixes an unfixed image formed using a liquid developer in which toner is dispersed in a solvent and transferred onto the recording medium, and surrounds the fixing unit, and is volatilized from the recording medium by the fixing unit. A solvent storage means for temporarily storing the solvent vapor, a solvent recovery means for cooling the solvent vapor and recovering it as a liquid solvent, and a solvent vapor stored in the solvent storage means. And a solvent transfer means for transferring the solvent storage means together with the air in the solvent storage means to the solvent recovery means, and detecting the concentration of the vapor of the solvent stored in the solvent storage means And a transfer adjusting means for adjusting the transfer amount of the solvent vapor by the solvent transferring means based on the concentration detected by the concentration detecting means, the transfer adjusting means comprising: A constant reference concentration is compared with the concentration detected by the concentration detecting means, and the transfer amount is increased if the detected concentration exceeds the predetermined reference concentration, and the transfer amount is decreased if the detected concentration is lower than the predetermined reference concentration. The amount of the solvent vapor transferred by the solvent transfer means is adjusted, the solvent storage means includes a casing containing the fixing means, and a heat source provided separately from the fixing means and for adjusting the ambient temperature in the casing. An image forming apparatus comprising:

  5). The solvent transfer means has a duct that couples the solvent storage means and the solvent recovery means, and a blower that blows air through the duct, and the transfer adjustment means controls the blower of the blower. The image forming apparatus according to any one of claims 1 to 4, wherein a transfer amount of the vapor of the solvent is adjusted.

  According to the image forming apparatus of the present invention, when the solvent vapor volatilized by the fixing device or the like is recovered and reused, the solvent storage means for temporarily storing the solvent vapor, and the solvent transfer means for transferring to the recovery apparatus And a solvent recovery means for cooling and recovering, detecting the concentration of the solvent vapor temporarily stored in the solvent storage means, and adjusting the transfer amount by the solvent transfer means based on them. Thus, the transfer amount, that is, the exhaust amount itself can be reduced in a state where the vapor concentration in the exhaust gas from the solvent recovery means is controlled, and therefore the total discharge amount of the solvent vapor can be suppressed.

  An embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings.

  Liquid development using a liquid developer is used in image forming apparatuses such as copying machines, simple printing machines, and printers. In general, an electrophotographic image forming process is commonly used for these. First, the electrophotographic wet image forming unit will be described with reference to FIG. 1, and further a fixing device that heats and fixes a toner image before fixing that has been developed using a liquid developer and transferred to a recording medium. Furthermore, the configuration and functional operation of the solvent storage device for temporarily storing the vapor of the carrier liquid volatilized at the time of fixing, the solvent transfer device for transferring it to the solvent recovery device, the solvent recovery device for cooling and liquefying and recovering the vapor, etc. This will be described (see FIGS. 2 and 3).

(Configuration of image forming unit and functional operation)
A configuration example of an image forming unit in the image forming apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view illustrating a schematic configuration example of an image forming unit in a wet image forming apparatus.

  In FIG. 1, reference numeral 1 denotes a photosensitive drum, which functions as an image carrier. The image forming unit 10 is centered on the photosensitive drum 1 and has a charging device 2 for uniformly charging the surface of the photosensitive drum 1, and an LED or laser beam on the charged photosensitive drum 1. , An exposure device 3 for forming an electrostatic latent image, a liquid developing device 4 for developing the electrostatic latent image using a liquid developer, and a transfer device 5 for transferring the developed toner image to a transfer material 7. And a cleaning device 6 for removing the liquid developer remaining on the surface of the photosensitive drum after transfer.

  In some cases, before and after the liquid developing device 4, a device for applying or collecting a part of the liquid developer in advance is provided. Here, a squeeze device 91 for removing excess liquid developer from the developed toner image is provided after the liquid developing device 4.

  The transfer material 7 may be a recording medium such as a recording sheet as it is, or may be configured to transfer to the recording medium again using an intermediate transfer belt or the like as the transfer material 7. In the present embodiment, the transfer material 7 is described as a recording medium, that is, a recording sheet (hereinafter referred to as a recording sheet).

  In general, the liquid developing device 4 carries a thin layer of a liquid developer on its surface, a developing roller 41 for developing a latent image on the photosensitive drum 1 as an image carrier, and a liquid developer 8 on its surface. Developer tank 44 and the like.

  In FIG. 1, only one liquid developing device 4 is disposed, but a plurality of liquid developing devices 4 may be disposed for color image formation. The color development method, the presence / absence of intermediate transfer, and the like may be set arbitrarily, and an arbitrary arrangement according to it can be taken.

  The photosensitive drum 1 rotates in the direction of arrow A shown in FIG. 1, and the charging device 2 charges the surface of the rotating photosensitive drum 1 to about several hundred volts by corona discharge or the like. On the downstream side of the charging device 2 in the rotation direction of the photosensitive drum, an electrostatic latent image whose surface potential is lowered to about 100 V or less is formed by the laser beam emitted from the exposure device 3.

  A liquid developing device 4 is disposed further downstream of the exposure device 3, and the electrostatic latent image formed on the photosensitive drum 1 is developed using the liquid developer 8.

  In the liquid developing device 4, a liquid developer 8 in which toner is dispersed in an insulating solvent (hereinafter also referred to as carrier liquid) is accommodated in a developer tank 44, and the liquid developer is provided on the surface of the developing roller 41. 8 is supplied, and a thin layer of the liquid developer 8 is carried on the developing roller 41.

  Further, due to the potential difference between the developing roller 41 and the electrostatic latent image on the photosensitive drum 1, the toner particles in the thin layer of the liquid developer 8 carried on the developing roller 41 become an electrostatic latent image on the photosensitive drum 1. Moving, the electrostatic latent image is developed.

  The developed toner image on the photosensitive drum 1 contains toner and carrier liquid. The squeeze device 91 is, for example, a squeeze roller, and removes excess carrier liquid from the developed toner image. The carrier liquid on the squeeze roller is removed by the blade 92.

  In the transfer device 5, the recording paper 7 transported at the same speed as the peripheral speed of the photosensitive drum 1 is charged by the recording paper transport belt 52, or a voltage is applied by the transfer roller 51, so The developed toner image is transferred onto the recording paper 7.

  A cleaning device 6 (for example, a cleaner blade) that removes the liquid developer 8 remaining on the surface of the photosensitive drum 1 is disposed on the downstream side of the transfer device 5. The cleaning device 6 removes the liquid developer 8 remaining on the photosensitive drum 1.

  The recording paper 7 onto which the toner image has been transferred by the transfer device 5 is conveyed to the fixing device 93 and is discharged after heating and fixing.

  Details of the heating of the toner image at the time of fixing, volatilization of the carrier liquid by the heating, the recovery device for the vapor of the evaporated carrier liquid, and the processing will be described later.

(Developer composition)
The liquid developer 8 used for development will be described. In the liquid developer 8, colored toner particles are dispersed at a high concentration in a carrier liquid as a solvent. In addition, additives such as a dispersant and a charge control agent may be appropriately selected and added to the liquid developer 8.

  Any carrier liquid can be used without particular limitation as long as it is generally used as an electrophotographic developer. In consideration of safety, an insulating, non-volatile solvent at room temperature is used. Examples of the non-volatile solvent include silicon oil, mineral oil, paraffin oil, mineral oil, and the like.

  The toner particles are mainly composed of a resin and a pigment or dye for coloring. The resin has a function of uniformly dispersing pigments and dyes in the resin and a function as a binder when being fixed to the recording material.

  Examples of the resin that can be used include thermoplastic resins such as polystyrene resin, styrene-acrylic resin, acrylic resin, polyester resin, epoxy resin, polyamide resin, polyimide resin, and polyurethane resin. A plurality of these resins may be mixed and used.

  Commonly commercially available pigments and dyes used for coloring the toner can also be used. For example, carbon black, bengara, titanium oxide, silica, phthalocyanine blue, phthalocyanine green, sky blue, benzidine yellow, lake red D, etc. can be used as the pigment. Solvent red 27, acid blue 9, or the like can be used as the dye.

  As a method for adjusting the liquid developer, it can be adjusted based on a commonly used technique. For example, the resin and the pigment are melt kneaded using a pressure kneader, a roll mill or the like at a predetermined blending ratio and uniformly dispersed, and the obtained dispersion is finely pulverized by, for example, a jet mill. Further, by classifying the obtained fine powder with, for example, an air classifier, a colored toner having a predetermined particle diameter can be obtained.

  Subsequently, the obtained toner is mixed with an insulating liquid as a carrier liquid at a predetermined blending ratio. This mixture can be uniformly dispersed by a dispersing means such as a ball mill to obtain a liquid developer.

  The volume average particle diameter of the toner is suitably in the range of 0.1 μm or more and 5 μm or less. When the average particle diameter of the toner is less than 0.1 μm, the developability is greatly lowered. On the other hand, when the average particle diameter exceeds 5 μm, the quality of the image is deteriorated.

  An appropriate ratio of the toner particles to the liquid developer is about 10 to 50% by mass. When the amount is less than 10% by mass, the toner particles are liable to settle, and there is a problem in stability over time during long-term storage. Further, in order to obtain a required image density, it is necessary to supply a large amount of developer, the carrier liquid adhering to the paper increases, and it must be dried at the time of fixing, and steam is generated, resulting in environmental problems. If it exceeds 50% by mass, the viscosity of the liquid developer becomes too high, making it difficult to manufacture and handle.

  The viscosity of the liquid developer is preferably from 0.1 mPa · s to 10,000 mPa · s at 25 ° C. When it is 10,000 mPa · s or more, it becomes difficult to stir the carrier liquid and the toner, and the burden on the apparatus surface for obtaining a uniform liquid developer is large.

(Configuration and functional operation for solvent recovery and reuse)
FIG. 2 shows a configuration diagram of an apparatus (a solvent storage device, a solvent transfer device, a solvent recovery device, etc.) for recovering and reusing the vapor of the solvent volatilized from the fixing device. FIG. 3 is a block diagram showing the relationship between the functional operations of the devices.

  With reference to FIG.2 and FIG.3, the structure and functional operation | movement for collection | recovery and reuse of the vapor | steam of a solvent (carrier liquid) are demonstrated.

<Configuration of fixing device>
As described above with reference to FIG. 1, the unfixed image formed by the image forming unit 10 is conveyed to the fixing device 93 and fixed by heating. The form of the heating device used for fixing is not particularly selected, but a roller fixing device is used here.

  In FIG. 2, the fixing device 93 includes a fixing roller 93 a and a pressure roller 93 b that are in pressure contact with each other, and sandwiches the recording paper 7 conveyed by the conveying device 52. A heat source 94 is included in the fixing roller 93a and the pressure roller 93b, and an unfixed image on the recording paper 7 is fixed by pressing and heating at a nip portion controlled to a fixing temperature. That is, the fixing device 93 functions as a fixing unit.

<Configuration of solvent storage device>
In the fixing device 93, the carrier liquid contained in the unfixed image is volatilized by heating. In order to collect this, a solvent storage device 110 that temporarily stores the solvent is provided. The solvent storage device 110 has a casing 111 and a heat source 112 and functions as a solvent storage means.

  The casing 111 seals the fixing device 93 that is a source of solvent evaporation so that the vapor of the evaporated solvent does not leak to the outside. In order to keep the atmospheric temperature as uniform and high as possible in the casing 111, it is preferable to use an auxiliary heat source 112 such as a hot plate, a fan, or the like.

  Further, in the casing 111, a temperature detection device 141 as temperature detection means for detecting the ambient temperature and a concentration detection device 142 (hereinafter referred to as a gas concentration meter) as concentration detection means for detecting the vapor concentration (gas concentration) of the carrier liquid. Also called). There are various types of gas concentration meters, but there is no particular concern. Here, an NDIR type measuring device that detects the gas concentration on a carbon number basis was used (PPMC basis).

  These atmospheric temperatures and gas concentrations are used to adjust the amount of temporarily stored gas transferred to the solvent recovery device 130 using the solvent transfer device 120 described below.

<Configuration of solvent transfer device>
The solvent transfer device 120 includes a duct 121 that couples the solvent storage device 110 and the solvent recovery device 130 described below, and temporarily stores the solvent vapor together with the air containing the solvent vapor from the solvent storage device 110 to the solvent recovery device 130. It has a blower 122 for transferring. That is, the solvent transfer device 120 functions as a solvent transfer unit.

  Further, in order to control the transfer of the air containing the solvent vapor by the blower 122, a transfer adjusting device 150 that functions as a transfer adjusting means is provided.

  The transfer adjustment device 150 has a control device 151, and drives the blower 122 to adjust the transfer amount by the solvent transfer device 120 based on the temperature and gas concentration detected by the temperature detection device 141 and the concentration detection device 142. Control.

  The gas concentration (predetermined reference concentration) serving as a reference for adjustment is calculated by taking into consideration the average carbon number 15 of IP2028 and calculating the gas concentration at which the humidity is 70% under the ambient temperature as a threshold (control PPM). Do. Details will be described later.

<Configuration of solvent recovery device>
Inside the solvent recovery device 130 is a cooling device 131 where the vapor of the carrier liquid is cooled and liquefied, and the carrier liquid and moisture accumulate in the recovery container 132. That is, the solvent recovery device 130 functions as a solvent recovery means.

  Thereafter, the moisture and the carrier liquid are sent to a separator (not shown). The mixture is easily separated because it separates into two layers, and the recovered carrier liquid is reused.

  On the other hand, in the solvent recovery device 130, the air after the majority of the carrier liquid vapor is liquefied is exhausted from the exhaust port 133 in a state of containing a gas (VOC) corresponding to the saturated vapor pressure at a cooled temperature. It will be done.

  The adjustment of the transfer amount to the solvent recovery device 130 based on the temporarily stored gas concentration and the atmospheric temperature described above is not only for suppressing the concentration of gas contained in the exhaust gas but also for suppressing the total discharge amount. The concept of adjusting the transfer amount for that purpose will be described below.

(Recovery operation control to reduce total solvent emissions)
<About the total solvent emission control method>
As described above, in the wet image forming apparatus in which the carrier liquid is volatilized and dried from the recording medium by the fixing device 93 and is recovered by the cooling type solvent recovery device 130, the gas is discharged from the solvent recovery device 130. A small amount of carrier liquid (VOC) remains and is contained. The concentration of this VOC is determined by the temperature of the exhausted gas (saturated vapor pressure).

  Therefore, first of all, it is necessary to suppress the concentration of discharged VOC. For this purpose, it is required to sufficiently cool, increase the recovery efficiency of the carrier liquid, lower the temperature of the exhaust gas, lower the saturated vapor pressure, and suppress the concentration of the remaining VOC.

  However, it is necessary to cool the entire air including the carrier liquid vapor, and considering the size of the apparatus, power consumption, and generation of frost, the cooling temperature is almost limited to around 0 ° C. Therefore, a vapor having a concentration corresponding to the saturated vapor pressure at that temperature remains without being liquefied and is contained in the exhaust gas.

  In addition, even if the concentration of discharged VOC is suppressed to a very small level so as not to cause a problem, if exhaust is continuously performed in a closed space, there may be a problem that adversely affects people and the environment. Therefore, it is necessary not only to control the concentration of discharged VOC but also to suppress the total discharge amount.

  The total amount of VOC emission is determined by VOC concentration × discharge air volume. As described above, the concentration of the discharged VOC is determined by the gas temperature (saturated vapor pressure). Therefore, to reduce the total amount of VOC emissions, it is effective to minimize the total amount of exhausted air.

  The amount of air exhausted from the solvent recovery device 130 depends on the amount of air flow transferred from the solvent storage device 110 to the solvent recovery device 130. In the present embodiment, in order to reduce the VOC exhaust air volume, the solvent vapor generated from the fixing device 93 is temporarily stored and stored in the casing 111 of the solvent storage device 110, and a sufficient concentration ( In a state where the predetermined reference concentration is reached, the transfer air volume is adjusted so as to be transferred to the solvent recovery device 130. As a result, control is performed to minimize the amount of air discharged from the solvent recovery device 130.

  Sufficient concentration (predetermined reference concentration) is a control concentration value that serves as a threshold for adjusting the transfer amount, and does not reach the saturated vapor concentration at that temperature, but it should be set as high as possible. desirable. For example, an appropriate concentration corresponding to about 50% or more and 90% or less of the saturated vapor concentration at that temperature is preferably set.

  By performing such control, a sufficiently concentrated solvent vapor is sent to the solvent recovery device 130, the vapor is cooled to a predetermined temperature in the solvent recovery device 130, the vapor concentration is reduced to the saturated vapor pressure, and the exhaust is discharged. Do. That is, considering the characteristics of the cooling recovery method, the exhaust air volume can be reduced to reduce the total VOC emissions.

  A specific carrier liquid vapor recovery operation control will be described below.

<Solvent recovery operation control flow>
FIG. 4 is a flowchart showing an example of the procedure of solvent vapor recovery operation control. With reference to FIG. 4, an example of the procedure of the solvent vapor recovery operation control will be described.

  In the flow of FIG. 4, when the control is started, first, in step S11, it is determined whether or not the fixing device 93 is driven. The fact that the fixing device 93 is driven means that the fixing operation of the recording paper 7 is performed, and the solvent volatilization occurs.

  When the fixing device 93 is driven, step S12 is executed. If the fixing device 93 is not driven, the process proceeds to step S18 to stop the control.

  In step S12, the cooling device 131 of the solvent recovery device 130 is put into a driving state. The air containing the solvent vapor is prepared to be transferred from the solvent storage device 110.

  In step S <b> 13, the control device 151 of the transfer adjustment device 150 acquires the detection temperature of the temperature detection device 141 and the detection concentration of the concentration detection device 142.

  The detected temperature is the ambient temperature in the casing 111 of the solvent storage device 110, and it is better to be as high as possible from the viewpoint of increasing the saturated vapor pressure of the solvent vapor, that is, sufficiently increasing the concentration. In consideration of the ability of the cooling device 131 of the solvent recovery device 130, it is desirable to control the temperature to an appropriate temperature using a heat source 112 such as a hot plate.

  In step S14, the control device 151 of the transfer adjusting device 150 refers to the control table and acquires a control concentration value (predetermined reference concentration) corresponding to the detected temperature.

  The control table is a data table in which the saturated vapor pressure is obtained with respect to the temperature, and the concentration determined at a predetermined ratio (here 70%, for example) with respect to the concentration corresponding to the vapor pressure is used as the control concentration value. It is. The detected control temperature can be obtained by referring to the corresponding control concentration value.

  In step S15, the control device 151 of the transfer adjustment device 150 compares the detected concentration with the control concentration value and determines whether or not the detected concentration is exceeded. If the control concentration value is exceeded (step S15; YES), step S16 is executed. If not exceeded (step S15; NO), step S17 is executed.

  In step S16, assuming that the detected concentration exceeds the control concentration value and has reached a sufficient concentration, the control device 151 of the transfer adjustment device 150 transfers the solvent vapor from the solvent storage device 110 to the solvent recovery device 130. The air blower 122 of the solvent transfer device 120 is set in a driving state.

  On the other hand, in step S17, the detected concentration is equal to or less than the control concentration value and has not reached a sufficient concentration, the control device 151 of the transfer adjustment device 150 is to temporarily store the solvent vapor in the solvent storage device 110, The blower 122 of the solvent transfer device 120 is stopped.

  By appropriately determining and executing the operation of step S16 or step S17, the solvent vapor reaching a sufficient concentration can be sent to the solvent recovery device 130 together with air, and the amount of air to be transferred is relatively minimized. be able to. That is, the amount of air discharged from the solvent recovery device 130 can also be suppressed, and the total amount of VOC discharged can be suppressed.

  As a processing procedure of the collection operation, the process returns to step S11 and the same processing is repeated from step S11. Each time, depending on the detected concentration of the temporarily stored solvent vapor, the driving state or the stopping state of the blower 122 is selected in steps S15 to S17.

  In this flow, the blower 122 is controlled by ON / OFF of the driving state or the stopped state in Step S15 to Step S17, but the form of control is not limited to this. For example, when the detected concentration exceeds the control concentration value, the transfer amount is increased, and when the detected concentration is lower than the control concentration value, the transfer amount is decreased. May be.

  The point is that the control mode is such that air containing solvent vapor is transferred in a state of sufficient concentration in light of the control concentration value.

  If stop of the driving of the fixing device 93 is detected in step S11 in the process of repeated processing, the collecting operation is also ended. Proceeding to step S18, the recovery operation is stopped.

  In step S18, the cooling device 131 of the solvent recovery device 130 is stopped. There is no longer any transfer from the solvent storage device 110 for air containing solvent vapor.

  In step S <b> 19, assuming that there is no more solvent vapor generation in the fixing device 93, the control device 151 of the transfer adjustment device 150 stops the blower device 122 of the solvent transfer device 120.

  This is the end of the solvent vapor recovery operation. By performing such control, a sufficiently concentrated solvent vapor is sent to the solvent recovery device 130, the vapor is cooled to a predetermined temperature in the solvent recovery device 130, the vapor concentration is reduced to the saturated vapor pressure, and the exhaust is discharged. Do. That is, by reducing the exhaust air volume, the total VOC emission can be reduced.

  The wet image forming apparatus shown in FIG. 1 was used to form an unfixed image on the recording paper. Fixing of the unfixed image and recovery of the carrier liquid were performed by a mechanism having a configuration as shown in FIG.

  As the carrier liquid, Idemitsu Kosan Co., Ltd. IP Solvent 2028 was used.

  As the toner, a black toner in a color copier C350 manufactured by Konica Minolta Business Technologies, Ltd. was pulverized to an average particle diameter of 3 μm and added to the carrier liquid.

  Further, 25% by mass of a dispersant (Solsperse 13940 manufactured by Avicia) was added to the toner amount.

The created image was a solid image, and the toner adhesion amount on the recording paper was set to 3 g / m ² and the carrier liquid amount at that time was set to ² g / m ² .

  Also, printing rates of 100% and 50% were prepared. The liquid amount of the unfixed image on the recording medium is mostly the liquid trapped between the toners, and the liquid amount on the medium is almost half when the printing rate is half.

<Operating conditions for carrier liquid recovery>
The recording paper having the unfixed image was passed through the fixing device for 1 hour at a speed of 60 sheets / powder at A4. The carrier liquid recovery operation described with reference to FIGS. 2 and 4 was performed, and the discharge amount of the carrier liquid vapor (VOC) was evaluated. The collection operation and evaluation conditions are shown below.

  The fixing roller temperature was set to 180 ° C., and the ambient temperature in the casing was adjusted to one of two levels (45 ° C. or 100 ° C.) using a heat source for temperature adjustment.

  As the concentration detection apparatus, an NDIR type gas concentration meter that detects on a carbon number basis (PPMC) was used. In calculation, the carrier liquid (IP2028) used was controlled in consideration of the average carbon number of 15 and compared with the control concentration value on a PPM basis.

  As the control concentration value, 70% of the concentration corresponding to the saturated vapor pressure at each temperature was set for each temperature. Control was performed to turn the blower ON / OFF depending on whether or not the control concentration value was exceeded.

The air volume of the blower was set to 1 m ³ / min. This was set as an air volume capable of transferring an air volume sufficiently exceeding the air volume when all of the input carrier liquid volume was volatilized and included as a control concentration value.

Different conditions are described for each example.
In Example 1, the printing rate of an unfixed image is 100%, and the ambient temperature is 45 ° C.
In Example 2, the printing rate of an unfixed image is set to 50%, and the ambient temperature is set to 45 ° C.
In Example 3, the printing rate of an unfixed image is 100%, and the ambient temperature is 100 ° C.
In Example 4, the printing rate of an unfixed image is set to 50%, and the ambient temperature is set to 100 ° C.

In the comparative example, the transfer amount was not adjusted, and the blower was always driven.
In Comparative Example 1, the unfixed image printing rate is set to 100% and the ambient temperature is set to 45 ° C.
In Comparative Example 2, the printing rate of an unfixed image is set to 50% and the ambient temperature is set to 45 ° C.

  In order to determine the transfer amount, the time when the blower was driven was recorded for each example. The concentration at the exhaust port of the solvent recovery device was measured and recorded.

In each example and comparative example, the set temperature of the cooling device was 2 ° C., and the temperature of the exhaust from the exhaust port was 2 to 3 ° C. The exhaust gas concentration was also constant at about 30 PPM. The exhausted VOC concentration is calculated to be 0.3 g / m ^{3 in} all cases.

The VOC total discharge amount was calculated by VOC concentration (0.3 g / m ³ ) × air volume (1 m ³ / min) × blower driving time.

<Experimental result>
The results in each example and comparative example are shown in Table 1.

According to Table 1, in Comparative Examples 1 and 2, the air blower is always driven, and the total displacement is 60 m ³ . Therefore, the total discharge amount of VOC is 18 g at 60 m ³ × 0.3 g / m ³ regardless of the printing rate.

  In Examples 1 and 2, the atmospheric temperature is 45 ° C. as in Comparative Examples 1 and 2, but the blower driving time is reduced to around 40 minutes, and the total discharge amount of VOC is suppressed to about 12 g. .

  In Examples 3 and 4, the air blower drive time is further reduced by setting the atmospheric temperature as high as 100 ° C. The transfer time is reduced to 1.7 minutes (printing rate 100%) and 1.2 minutes (printing rate 50%) in order to transfer a sufficiently high concentration gas to the recovery device. The total VOC emissions are also greatly suppressed to 0.51 g and 0.36 g, respectively.

  In this embodiment, the ambient temperature is set to 45 ° C. or 100 ° C., but it is not always necessary to perform temperature control in such a fixed manner. In actuality, even if there is a change in the temperature of the atmosphere, if the control concentration value for each temperature is prepared as table data, the control concentration value may be controlled to change immediately according to the temperature change.

  Further, as described above, it is desirable that the air blower can control the air flow rate itself, such as changing the rotation speed, instead of the ON / OFF control. In such a case, by estimating the amount of vapor that volatilizes based on the expected value of the printing rate and adhesion amount (for example, feedback from a dot counter, etc.), not only ON / OFF, but also the air volume is changed accordingly. The gas concentration to be transferred can be adjusted more appropriately, and the transfer amount can be suppressed.

  As described above, according to the image forming apparatus of the present embodiment, when the solvent vapor volatilized by the fixing device or the like is recovered and reused, the solvent storage means for temporarily storing the solvent vapor and the recovery apparatus A solvent transfer means for transferring and a solvent recovery means for cooling and recovering are provided, the concentration of the solvent vapor temporarily stored in the solvent storage means is detected, and the transfer amount by the solvent transfer means is adjusted based on them. Thus, the transfer amount, that is, the exhaust amount itself can be reduced in a state where the vapor concentration in the exhaust gas from the solvent recovery means is controlled, and therefore the total discharge amount of the solvent vapor can be suppressed.

  In addition, the above-mentioned embodiment is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is sectional drawing which shows the schematic structural example of the image formation part in a wet image forming apparatus. It is sectional drawing which shows the schematic structural example of the apparatuses (a solvent storage apparatus, a solvent transfer apparatus, a solvent collection apparatus, etc.) for collection | recovery and reuse of the vapor | steam of the solvent volatilized from the fixing apparatus. FIG. 3 is a block diagram showing a relation of functional operations of each device in FIG. It is a flowchart which shows the example of a procedure of collection | recovery operation control of the solvent vapor | steam in the apparatus of FIG.

Explanation of symbols

1 Photosensitive drum (image carrier)
2 Charging device 3 Exposure device 4 Liquid developing device 5 Transfer device (transfer roller, recording paper transport belt)
6 Cleaning device (cleaner blade)
7 Transfer material (recording paper)
8 Liquid developer 10 Image forming part 41 Developing roller (developer carrier)
44 Developer tank 93 Fixing device (fixing roller, pressure roller)
DESCRIPTION OF SYMBOLS 110 Solvent storage apparatus 111 Casing 112 Heat source 120 Solvent transfer apparatus 121 Duct 122 Blower apparatus 130 Solvent recovery apparatus 131 Cooling apparatus 132 Recovery container 133 Exhaust port 141 Temperature detection apparatus 142 Concentration detection apparatus 150 Transfer adjustment apparatus 151 Control apparatus

Claims (5)

A fixing unit that heat-fixes an unfixed image that is formed using a liquid developer in which toner is dispersed in a solvent and is transferred onto a recording medium;
A solvent storage unit that surrounds the fixing unit and temporarily stores the vapor of the solvent volatilized from the recording medium by the fixing unit;
Solvent recovery means for cooling the solvent vapor and recovering it as the liquid solvent;
An image forming apparatus comprising: a solvent transfer unit configured to transfer the vapor of the solvent stored in the solvent storage unit to the solvent recovery unit together with air in the solvent storage unit;
Concentration detecting means for detecting the concentration of vapor of the solvent stored in the solvent storing means;
A transfer adjusting unit that adjusts the amount of the solvent vapor transferred by the solvent transferring unit based on the concentration detected by the concentration detecting unit;
The transfer adjusting means is
Compare the predetermined reference concentration with the concentration detected by the concentration detecting means, and increase the transfer amount if the detected concentration exceeds the predetermined reference concentration, and decrease the transfer amount if the detected concentration falls below, Adjusting the transfer amount of the solvent vapor by the solvent transfer means ;
Having temperature detection means for detecting the ambient temperature in the solvent storage means,
The image forming apparatus, wherein the predetermined reference concentration is determined according to a saturated vapor concentration of the solvent at a temperature detected by the temperature detecting unit . The transfer adjusting means is
When the concentration detected by the concentration detection means exceeds the predetermined reference concentration, the transfer is performed with a predetermined transfer amount, and when the concentration is lower than the predetermined reference concentration, the transfer of the solvent vapor by the solvent transfer means is stopped. The image forming apparatus according to claim 1 , wherein adjustment is performed. 3. The image forming apparatus according to claim 2 , wherein the predetermined reference concentration is set to 50% or more and 90% or less of the saturated vapor concentration of the solvent at the temperature detected by the temperature detecting unit. . A fixing unit that heat-fixes an unfixed image that is formed using a liquid developer in which toner is dispersed in a solvent and is transferred onto a recording medium;
A solvent storage unit that surrounds the fixing unit and temporarily stores the vapor of the solvent volatilized from the recording medium by the fixing unit;
Solvent recovery means for cooling the solvent vapor and recovering it as the liquid solvent;
An image forming apparatus comprising: a solvent transfer unit configured to transfer the vapor of the solvent stored in the solvent storage unit to the solvent recovery unit together with air in the solvent storage unit;
Concentration detecting means for detecting the concentration of vapor of the solvent stored in the solvent storing means;
A transfer adjusting unit that adjusts the amount of the solvent vapor transferred by the solvent transferring unit based on the concentration detected by the concentration detecting unit;
The transfer adjusting means is
Compare the predetermined reference concentration with the concentration detected by the concentration detecting means, and increase the transfer amount if the detected concentration exceeds the predetermined reference concentration, and decrease the transfer amount if the detected concentration falls below, Adjusting the transfer amount of the solvent vapor by the solvent transfer means;
The solvent reservoir means, said a casing which encloses the fixing means, said fixing means and images forming device you; and a heat source for adjusting the separately provided atmospheric temperature in the casing. The solvent transfer means has a duct that couples the solvent storage means and the solvent recovery means, and a blower that blows air through the duct,
5. The image forming apparatus according to claim 1, wherein the transfer adjusting unit adjusts the transfer amount of the solvent vapor by controlling the blowing of the blowing device. 6.

Images