JP2006175644A - Inkjet image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet image forming apparatus which enables an inkjet head to draw a definite dot diameter without receiving the influence of a heat generated at a heating part such as a heat fixing part, and which can acquire always stable inkjet drawing properties. <P>SOLUTION: The problem is solved by providing a heating part case having an inlet and an outlet for carrying a recording medium and a vent opening communicating with the outside of the case, and surrounding a heating means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to the technical field of an inkjet image forming apparatus, and more specifically, inkjet image formation that can perform stable ink discharge while suppressing temperature changes of an ink discharge portion that forms an image on a recording medium by an inkjet method. Relates to the device.

  In an image forming apparatus that outputs a color image or the like, an ink jet system that forms an image by ejecting ink from an ink jet head and attaching the ejected ink to a recording medium has a simple structure and facilitates downsizing of the apparatus. It is widely used because it exists. As an image forming apparatus (inkjet printer) using an inkjet method, an electrostatic drive method, a thermal method, a piezo method, and the like are known. The inks used in these ink jet printers include dye-based inks in which a dye is dissolved in an aqueous or non-aqueous solvent, pigment-based inks in which a pigment is dispersed in an aqueous or non-aqueous solvent, pigments and dyes, etc. There are inks in which colored particles in which a coloring material and a resin are combined are dispersed in a solvent.

Fixation of an image drawn with dye-based ink and pigment-based ink is generally performed by evaporation of an ink solvent by natural drying or penetration into a recording medium.
However, when coated paper or film is used as the recording medium, the effect of penetrating the ink solvent into the recording medium cannot be expected. A heat fixing method for fixing is used.
Even when a recording medium having ink solvent permeability is used, in order to improve the fixability by natural drying, if a solvent that easily evaporates is used as the solvent constituting the ink, the ink is ejected to the nozzle outlet. Problems such as clogging occur, and the use of processed paper having excellent solvent absorbability as recording paper (recording medium) results in an increase in cost. For this reason, it has also been proposed to heat and fix an image by conveying the recording medium after drawing between a heating roller and a pressure roller (see, for example, Patent Document 1).

  On the other hand, fixing an image drawn with ink in which colored particles are dispersed in a solvent fixes the image by applying heat after drawing and fusing a resin combined with a coloring material onto the recording medium. This is done by a heat fixing method.

Furthermore, in an inkjet printer, for the purpose of obtaining high image quality equivalent to a photograph and long-term image storage stability, it has been proposed to perform fixing in as short a time as possible after drawing using pigment-based ink, As a device configuration for that purpose, a fixing unit that heats and heat-fixes the recording medium while being pressurized and conveyed between the two belt surfaces may be disposed immediately after the downstream side of the ink head unit (inkjet head unit). It has been proposed (see, for example, Patent Document 2).
Japanese Patent No. 2860123 JP 2003-80692 A

  In a printer using the heat fixing method, the temperature in the printer, particularly in the vicinity of the heat fixing portion, increases due to the heat generated in the heat fixing portion. Therefore, as in the printer described in Patent Document 2, when the heat fixing unit is arranged immediately after the downstream side of the ink jet head, or in order to make the apparatus compact, the head and the heat fixing unit are close to each other. When arranged, the heat of the heat fixing unit greatly affects the temperature of the head unit.

The ink ejectability of the inkjet head is extremely sensitive to temperature. When the temperature in the vicinity of the inkjet head changes, the ink discharge amount changes due to changes in the physical properties of the ink in the ink discharge section, and the drawn dot diameter changes. Further, if the temperature rises too much, there arises a problem that the ink is dried and fixed at the discharge portion and cannot be discharged (clogging).
In particular, a concentrated electrostatic ink jet head that discharges ink concentrated by electrostatic force can discharge ultrafine droplets of ink by the action of electrostatic force, and can perform ultrahigh-definition drawing. However, even a slight change in temperature affects the ejection of ultrafine droplets of ink, so it is extremely important to keep the head temperature stable.

  However, in the conventional printer as described above, the problem that the heat of the heat fixing unit affects the head portion and thereby the drawing performance is not studied.

  The object of the present invention is to solve the above-mentioned problems of the prior art, and the ink jet head is not affected by the heat generated in the heating part such as the heat fixing part, so that a constant dot diameter can be drawn. Another object of the present invention is to provide an ink jet image forming apparatus capable of obtaining stable ink jet drawing performance by always performing stable ink ejection.

In order to solve the above problems, the present invention has an ink discharge section that discharges ink toward a recording medium, and an image forming unit that forms an image by attaching the discharged ink to the recording medium;
Conveying means for conveying the recording medium;
Heating means for the recording medium disposed downstream of the image forming means in the conveying direction of the recording medium;
The present invention provides an inkjet image forming apparatus having a recording medium inlet and outlet, and a heating part case surrounding the heating means, which has a vent hole communicating with the outside of the case.

  Here, it is preferable to have a discharge unit that discharges the heated air in the heating unit case from the vent hole, and the discharge unit discharges the heated air in the heating unit case to the outside of the inkjet image forming apparatus. It is preferable to discharge.

Moreover, it is preferable to have a ventilation means which sends air into the said heating part case from the said vent hole.
Moreover, it is preferable that at least a part of the heating part case is made of a heat insulating material.

Further, the ink contains particles including a charged color material and a solvent,
Preferably, the image forming means forms an image on the recording medium by ejecting ink droplets from the ink ejection section by applying an electrostatic force to the ink.

  According to the present invention, the above configuration can prevent the influence of heat from a heating part such as a heat fixing part in the ink jet head, and can keep the temperature of the drawing part stable, thereby reducing the constant dot diameter. Drawing can be performed, and high-quality drawing can be stably performed.

  The ink jet image forming apparatus according to the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

Hereinafter, as an embodiment in which the effect of the present invention is particularly great, an electrostatic inkjet image forming apparatus that performs image formation by an electrostatic drive method will be described as an example. However, the present invention is not limited to this, and may be an image forming apparatus that forms an image by various ink jet methods such as a thermal type and a piezo type.
Hereinafter, in the electrostatic inkjet image forming apparatus, the case where the color material particles in the ink are positively charged will be described as an example. However, the present invention is not limited to this, and conversely, the ink You may use what charged the color material particle | grains in the inside negatively. In this case, the polarity of each part that acts on image formation (drawing) may be set to the opposite polarity to the following example.

  FIG. 1 is a conceptual diagram showing the configuration of the first embodiment of the inkjet image forming apparatus of the present invention. The ink jet image forming apparatus 10 (hereinafter simply referred to as the image forming apparatus 10) shown in FIG. 1 controls the ejection of ink containing charged color material particles (charged fine particles) by electrostatic force, and 4 on the recording medium P. After color printing and forming a full color image, the formed image is fixed by contact heating with a heating roller (fixing roller). The holding means 12 for the recording medium P, the conveying means 14, the drawing means (image) Forming means) 16, fixing means 18, drawing part case 20 surrounding the drawing part by drawing means 16, outside air introduction means 22 connected to drawing part case 20, and temperature control means provided in outside air introduction means 22 24, a fixing unit case 26 surrounding the fixing unit 18, an exhaust unit 28 connected to the fixing unit case 26, and a solvent recovery unit 30, which are enclosed in the housing 11. .

First, the holding means 12 for the recording medium P will be described.
The holding unit 12 includes a paper feed tray 34 that holds the recording medium P before drawing, a pickup roller 36, and a paper discharge tray 38 that holds the recording medium P after drawing.

  The paper feed tray 34 holds a plurality of recording media P to be used for drawing, and is inserted into the housing 11 from the left side of the housing 11 in FIG. The pickup roller 36 is disposed in the vicinity of the front end portion (right end portion in the drawing) of the mounting portion of the paper feed tray 34. At the time of drawing an image, the recording medium P is taken out from the paper feed tray 34 one by one by the pickup roller 36 and supplied to the conveying means 14 for the recording medium P. In the vicinity of the pickup roller 36, in order to easily separate the recording medium P stocked in layers, a neutralizing brush, a neutralizing roller, an air blowing blower, and the like for neutralizing the recording medium P are provided. Is preferred.

  The paper discharge tray 38 holds the recording medium P on which an image has been formed, and is provided at the end of the transport path of the recording medium P inside the housing 11, and its leading end (the leading end in the transport direction of the recording medium P). Side) is located outside the housing 11. The recording medium P after drawing is transported by the transport means 14 and discharged onto the paper discharge tray 38.

Next, the conveying means 14 for the recording medium P will be described.
The transport means 14 transports the recording medium P along a predetermined path from the paper feed tray 34 to the paper discharge tray 38, and includes a pair of transport rollers 40, a transport belt 42, rollers 44a and 44b, and conductive. Platen 46, recording medium P charger 48 and static eliminator 50, separation claw 52, and discharge roller 54. A fixing unit 18 to be described later is provided between the separation claw 52 and the discharge roller 54, and a guide plate is provided between the separation claw 52 and the fixing unit 18 and between the fixing unit 18 and the discharge roller 54. Is arranged. As the conveying means 14, other than the illustrated ones, normal conveying members such as a conveying roller pair, a conveying belt, and a conveying guide are appropriately arranged at an appropriate interval for conveying the recording medium P. Also good.

  The conveyance roller pair 40 is provided at a position between the pickup roller 46 and the conveyance belt 42. The recording medium P taken out from the paper feed tray 34 by the pickup roller 46 is nipped and conveyed by the conveying roller pair 40 and the conveying belt 42 and is supplied to a predetermined position on the conveying belt 42.

  The conveyor belt 42 is a loop-like endless belt, and is stretched around two rollers 44a and 44b. At least one of the rollers 44a and 44b is connected to a drive source (not shown) and is driven to rotate at a predetermined speed during drawing. Thereby, the conveyance belt 42 rotates clockwise in the drawing, and conveys the recording medium P electrostatically attracted to the conveyance belt 42 at a predetermined speed.

  The conveyance belt 42 has an insulating surface (front surface) on which the recording medium P is electrostatically attracted and an electrically conductive surface (back surface) in contact with the rollers 44a and 44b. In addition, a conductive platen 46 is disposed on the inner peripheral surface side of the transport belt 42 across a position facing the charger 48 and a position facing an inkjet head 68 described later. The conductive platen 46 is grounded. Thereby, the conveyance belt 42 also functions as a counter electrode of the inkjet head 68 at a position facing the inkjet head 68.

  The conductive platen 46 is preferably disposed so as to slightly protrude from the line connecting the outer circumferences of the rollers 44a and 44b to the inkjet head 68 side. By arranging in such a manner, it is possible to apply tension to the conveyor belt 42 and suppress fluttering of the conveyor belt 42.

  The charger 48 for the recording medium P includes a scorotron charger 58 and a negative high-voltage power supply 60. The scorotron charger 58 is disposed on the conveyance path of the recording medium P between the conveyance roller pair 40 and the drawing unit 16 so as to face the surface of the conveyance belt 42. The scorotron charger 58 is connected to the negative terminal of the negative high voltage power supply 60, and the positive terminal of the negative high voltage power supply 60 is grounded.

  The surface of the recording medium P is uniformly charged to a predetermined negative high potential by a scorotron charger 58 connected to a negative high-voltage power supply 60, and a constant DC bias voltage (for example, about −1.5 kV required for drawing). ) Is applied. Accordingly, the recording medium P is electrostatically adsorbed on the insulating surface of the transport belt 42.

  The static eliminator 50 for the recording medium P includes a corotron static eliminator 62, an AC voltage source 64, and a high voltage power source 66. The corotron static eliminator 62 is disposed on the downstream side of the drawing unit 16 in the conveyance direction of the recording medium P so as to face the surface of the conveyance belt 42. The corotron static eliminator 62 is connected to a high voltage power source 66 via an AC voltage source 64, and the other end of the high voltage power source 66 is grounded.

  The recording medium P after drawing is neutralized by the corotron neutralizer 62 and then separated from the conveying belt 42 by the separation claw 52 disposed on the downstream side thereof. The recording medium P separated from the conveyance belt 42 is conveyed to the fixing unit 18, conveyed while being subjected to fixing processing by the fixing unit 18, and then discharged to the discharge tray 38 by the discharge roller 54.

Next, the drawing means (image forming means) 16 will be described.
The drawing means 16 uses ink containing charged color material particles, controls the ejection of ink with electrostatic force according to the image data, and forms an image according to the image data on the recording medium P. And an electrostatic ink jet head 68, a head driver 70, an ink circulation mechanism 72, and a position detector 74 for the recording medium P.

  In the inkjet head 68, the ink discharge portion is held on the surface of the conveyor belt 42 (held on the surface of the conveyor belt 42) at a position where the recording medium P is conveyed in a stable plane state on the conveyance path of the recording medium P by the conveyor belt 42. The recording medium P is disposed at a predetermined distance from the surface of the recording medium P to be recorded. In the illustrated example, the ink jet head 68 is disposed opposite to the conveying belt 42 supported by the conductive platen 46 between the rollers 44a and 44b.

  The ink jet head 68 is an electrostatic ink jet head that controls ink ejection by applying an electrostatic force to ink in the ink ejection section. The inkjet head 68 is a line head capable of simultaneously forming an image for one row, and cyan (C), magenta (M), yellow (Y), black (B) for forming a full-color image. 4) discharge heads of four colors. The specific configuration of this ejection head, the method of driving the inkjet head 68 (each color ejection head) by the head driver 70, the ink circulation mechanism 72 and the ink used in the inkjet head 68 will be described later.

  The position detector 74 of the recording medium P is a conventionally known position detecting means such as a photosensor, and is a predetermined position on the upstream side of the inkjet head 68 on the conveyance path of the recording medium P (in the illustrated example, a pair of conveyance rollers). 40 and a position between the charger 48 and the surface of the conveyance belt 42 on which the recording medium P is conveyed. The position information of the recording medium P detected by the position detector 74 is supplied to the head driver 70.

  The head driver 70 is a driver for the inkjet head 68 and is connected to the inkjet head 68 via a drive signal cable. In the illustrated example, the head driver 70 is attached to the center upper portion in the figure inside the housing 11. Image data is input to the head driver 70 from an external device, and position information of the recording medium P is input from the position detector 74. Then, the head driver 70 controls the ejection timing of each color ejection head of the inkjet head 68 according to the position information of the recording medium P, and ejects each color ink from each color ejection head according to the image data. A full-color image corresponding to the image data is formed on the medium P.

Next, the fixing unit 18 will be described.
The fixing unit 18 heats and fixes the image formed on the recording medium P by the drawing unit 16 using a fixing roller (heating roller), and includes a heating roller 80 and a pressure roller 82. The fixing unit 18 fixes the image formed on the recording medium P by heating and pressing the recording medium P by nipping and conveying the recording medium P by the heating roller 80 and the pressure roller 82. In other words, the color material particles in the ink on the recording medium P are softened and melted by the heating and pressure applied by the heating roller 80 and the pressure roller 82, and are fixed to the recording medium P to fix the image.

  The heating roller 80 has a built-in heating source such as a heater or a halogen lamp inside, and heats the recording medium P in contact with the image forming surface of the recording medium P. The heating roller 80 has a rotational axis fixed, and is rotationally driven by a rotational driving means (not shown). Alternatively, when a pressure roller 82 to be described later is rotationally driven, the heating roller 80 is not rotationally driven but is frictionally driven by the rotating pressure roller 82 (by the friction of the roll surface with the pressure roller 82). It may be configured to rotate).

  The axis of the pressure roller 82 is arranged in parallel with the axis of the heating roller 80 and presses the heating roller 80 with a predetermined pressing force that is uniform in the roll axis direction. As a result, the recording medium P conveyed between the heating roller 80 and the pressure roller 82 and the color material particles on the recording medium P are pressed. The pressure roller 82 may be a heating roll having a heating source. Further, the pressure roller 82 is rotationally driven by a rotational driving means (not shown) so that the peripheral speed at the clamping portion is the same as that of the heating roller 80. The rotation driving unit of the pressure roller 82 may have a driving source that is separate from the rotation driving unit of the heating roller 80 or may be connected to a common driving source. When the heating roller 80 is rotationally driven, the pressure roller 82 is not connected to a driving source and is frictionally driven by the rotating heating roller 80 (rotated by friction of the roll surface with the heating roller 80. It may be configured.

  It is preferable that the surfaces of the heating roller 80 and the pressure roller 82 have excellent releasability. For example, the surfaces of the heat roller 80 and the pressure roller 82 are preferably made of silicone rubber, fluororubber, fluororesin, or the like, and a release agent such as oil is preferably applied. .

The surface temperature of the heating roller 80 and the pressing force of the recording medium P by the pressure roller 82 (nip force between the heating roller 80 and the pressure roller 82) may be set as appropriate so as to ensure stable fixability. The surface layer of the heating roller 80 and the pressure roller 82 is made of an elastic material, and the recording medium P and the heating roller 80 are brought into surface contact by the pressing force of the pressure roller 82, so that a sufficient heating and pressing time for fixing is achieved. It is also preferable to ensure this.
Further, it is preferable that the pressure roller 82 is a driving roll and the heating roller 80 is a driven roll, and the product hardness of the surface of the heating roller 80 is smaller than the product hardness of the pressure roller 82.

  The fixing unit 18 is not limited to the one using the heating roller 80 and the pressure roller 82, and may be one that heats and fixes the recording medium P while being sandwiched and conveyed by the heating roller and the conveyance belt. The recording medium P may be fixed by heating the recording medium P with an arbitrary heating unit while nipping and conveying the recording medium P between the conveyance belts. In addition, various heat fixing means such as those in which the heating means and the pressure means are provided separately, and those in which the preliminary heating means is provided in advance of the heat fixing means are applicable.

Next, the drawing unit case 20 and the outside air introduction means 22 will be described.
In the present embodiment, as a preferred embodiment, a drawing unit case 20 surrounding the drawing unit of the drawing unit 16 is provided. The drawing unit case 20 is a case surrounding a drawing unit by the inkjet head 68, that is, an ink discharge unit of the inkjet head 68 and a holding unit for the recording medium P facing the inkjet head 68.
In the image forming apparatus 10 of the present invention, the drawing unit case 20 is not an essential component, but by providing the drawing unit case 20, the drawing unit is isolated from other parts, and in the heating unit such as the fixing unit 18. It is preferable because the influence of the generated heat can be more reliably prevented from affecting the ink discharge portion.

  In the image forming apparatus 10 of FIG. 1, the drawing unit case 20 includes an inkjet head 68, a head driver 70, a part of an ink supply path 78a and an ink recovery path 78b, a transport belt 42 and rolls 44a and 44b. A conductive platen 46 disposed on the inner peripheral side of the conveying belt 42 so as to face the ink jet head 68, and a position detector disposed on the outer peripheral side (upper side in the drawing) of the conveying belt 42 so as to face the conveying belt 42. 74, the charger 48 and the static eliminator 50, and conveying means such as guide plates and separation claws 52 disposed on the upstream side and the downstream side of the conveying belt 42 are included.

The drawing unit case 20 has an opening 20a that is a carry-in port for carrying the recording medium P into the upstream side of the conveyance belt 42, an opening 20b that is a carry-out port for carrying out the recording medium P from the downstream side of the conveyance belt 42, and drawing. An outside air inlet 20c for introducing air outside the part case 20 is provided, and the other parts are almost sealed. The sizes of the openings 20a and 20b are set so that the amount of air that is sufficient for carrying in and out of the recording medium P and substantially the same or slightly smaller than the amount of outside air introduced from the outside air introduction port 20c passes. . As a result, the inside of the drawing unit case 20 becomes almost equal to or slightly higher than the outside thereof, and an air flow from the inside of the drawing unit case 20 to the outside is generated in the vicinity of the openings 20a and 20b, and the opposite air flow is suppressed. To do.
Note that the drawing unit case 20 has an opening for discharging the air inside the drawing unit case 20 in addition to the openings 20a and 20b as long as the inside of the drawing unit case 20 can be maintained at a pressure that is substantially equal to or slightly higher than the outside. It may be.

  The drawing unit case 20 is preferably partially or entirely made of a heat insulating material. In this case, the main body of the drawing unit case 20 may be made of a heat insulating material, a heat insulating member may be appropriately attached to the outside of the drawing unit case 20 made of an arbitrary material, or the drawing unit made of a heat insulating material. A heat insulating member may be appropriately attached to the case 20. Thereby, it is possible to prevent the influence of heat from others from reaching the inside of the drawing unit case 20. In the illustrated example, a heat insulating member 94 is provided on the surface of the drawing unit case 20 on the fixing unit 18 side (downstream in the conveyance direction of the recording medium P). Thereby, in particular, it is possible to more effectively prevent heat from the fixing unit 18 serving as a heating unit from being transmitted to the inside of the drawing unit case 20.

An outside air introduction means 22 is connected to the outside air introduction port 20c.
The outside air introduction means 22 introduces air outside the casing 11 (fresh air) into the drawing unit case 20, and includes an outside air introduction fan 84 attached to the outside air introduction port 20c, and an outside air introduction fan. 84, a filter 86 attached to the outer side of 84 (the side opposite to the drawing unit case 20), a duct 88 that connects the outside air introduction fan 84 and filter 86 to the outside of the apparatus, and temperature control means provided at the end of the duct 88. 24.

The temperature adjusting means 24 adjusts the temperature of the outside air taken in from the outside in order to send air at a constant temperature into the drawing unit case 20. In the illustrated example, the temperature control means 24 is attached to the inner wall on the left side of the housing 11 in the drawing and is connected to the end of the duct 88, but the temperature control means 24 is provided in the middle of the duct 88. Also good. Thus, by using the temperature control means 24, it is possible to always introduce a constant temperature of air into the drawing unit case 20. Alternatively, for example, by providing a temperature sensor inside the drawing unit case 20 and appropriately controlling the temperature of the air introduced into the drawing unit case 20 by the temperature adjusting means 24 based on the temperature detection result by the temperature sensor, The temperature inside the drawing unit case 20 may be kept constant. In this case, the temperature sensor is preferably provided in the vicinity of the inkjet head 68.
When the outside air having a temperature range that does not affect the drawing in the drawing unit 16 can be supplied to the inside of the drawing unit case 20 without using the temperature adjustment unit 24, such as when the temperature change of the outside air is small, the temperature adjustment unit 24 may not be provided.
Furthermore, it is more desirable that a humidity control means is provided at the end or middle of the duct 88. In that case, by controlling the humidity of the air sent to the inside of the drawing unit case 20 by the humidity control means, it is possible to always introduce air with a constant humidity into the drawing unit case 20, The humidity of the case 20 can be kept constant. Moreover, it is good also as a form provided with a humidity control means, without providing the temperature control means 24. FIG.

When the outside air introduction fan 84 is rotated, outside air is taken in from the connection port of the duct 88 (temperature adjusting means 24) to the outside of the apparatus, and the temperature of the taken outside air is adjusted by the temperature adjusting means 24. The foreign matter is removed and introduced into the drawing unit case 20.
Outside air introduced from the outside air introduction port 20 c flows from the outside air introduction port 20 c to the opening 20 a or the opening 20 b inside the drawing unit case 20, and is exhausted from the openings 20 a and 20 b to the outside of the drawing unit case 20.

  In this manner, outside air having a constant temperature is introduced into the drawing unit case 20 from the outside air inlet 20c, and the air inside the drawing unit case 20 is discharged from the openings 20a and 20b. Air heated by heat generated in other parts of the image forming apparatus 10 can be prevented from flowing into the drawing unit case 20, and the temperature inside the drawing unit case 20 can be stably maintained.

  In the image forming apparatus 10 of the present invention, as will be described later, the fixing unit 18 that is a heating unit is surrounded by a fixing unit case 26. Therefore, an increase in the environmental temperature due to the influence of heat from the fixing unit 18 is suppressed inside the housing 11. Therefore, the outside air introduction unit 22 may send the air inside the housing 11 to the drawing unit case 20. At this time, it is preferable to send the air of a portion where the influence of heat is as small as possible, such as a portion away from the heating unit such as the fixing unit 18, to the drawing unit case 20. In the openings 20a and 20b, particularly in the portion of the opening 20b adjacent to the fixing unit 18, the air heated from the inside to the outside is created to prevent the air heated by the fixing unit 18 from entering the drawing unit case 20. And the temperature of the drawing unit can be kept stable.

  The drawing unit case 20 may be provided so that the drawing unit case 20 surrounds only the drawing unit formed by the ink jet head 68 and the vicinity thereof. In this way, by setting the drawing unit case 20 to a size that surrounds the minimum range including the drawing unit, a wide interval between the drawing unit case 20 and the fixing unit case 26 can be secured, and the fixing unit case 26 can be secured within the fixing unit case 26. It is also possible to minimize the possibility that the influence of heat generated in the above will reach the inside of the drawing unit case 20.

Next, the fixing unit case 26 and the exhaust unit 28 which are features of the present invention will be described.
The fixing unit case 26 surrounds the fixing unit 18 which is a heat fixing unit, thereby preventing the heated air caused by the heat generated by the fixing unit 18 from freely diffusing, and the heat of the fixing unit 18 is outside the fixing unit case 26. In particular, the transmission to the drawing means 16 is suppressed.
The fixing unit case 26 has an opening 26 a that is a carry-in port for carrying the recording medium P from the upstream side of the fixing unit 18, an opening 26 b that is a carry-out port for carrying the recording medium P to the downstream side of the fixing unit 18, and fixing. A vent hole 26c leading to the outside of the part case 26 is provided, and the other parts are almost sealed. An exhaust unit 28 is connected to the vent 26 c, and heated air inside the fixing unit case 26 is discharged to the outside by the exhaust unit 28.

The sizes of the openings 26a and 26b are set so that the amount of air that is sufficient for carrying in and out of the recording medium P and substantially the same as or slightly smaller than the amount of air discharged from the vent 26c passes. As a result, the inside of the fixing unit case 26 becomes almost equal to or slightly lower than the outside thereof, and an air flow from the outside to the inside of the fixing unit case 26 is generated in the vicinity of the openings 26a and 26b, and the opposite air flow is suppressed. it can.
In addition, as long as the inside of the fixing unit case 26 can be kept at an approximately equal pressure or a low pressure with respect to the outside thereof, the fixing unit case 26 has openings other than the openings 26a and 26b through which the outside air passes. You may have.

  The fixing unit case 26 is preferably partially or entirely made of a heat insulating material. In this case, the main body of the fixing unit case 26 may be made of a heat insulating material, or a heat insulating member may be attached to the outer surface or the inner surface of the fixing unit case 26 made of any material partially or entirely. Alternatively, a heat insulating member may be appropriately attached to the fixing unit case 26 made of a heat insulating material. Thereby, it is possible to suppress or prevent the heat generated by the fixing unit 18 (heating roller 80) from being transmitted to the outside of the fixing unit case 26. In the illustrated example, the entire fixing unit case 26 is made of a heat insulating material, and a heat insulating member 96 is provided on the surface of the fixing unit case 26 on the drawing unit 16 side (upstream side in the conveyance direction of the recording medium P). Yes. Thereby, it is possible to more effectively suppress or prevent heat from being transmitted to the drawing means 16.

The exhaust unit 28 collects heat (exhaust heat) inside the fixing unit case 26 by discharging the air inside the fixing unit case 26 to the outside of the housing 11, and is provided at the vent 26 c. The exhaust fan 90 is attached, and a duct 92 that connects the exhaust fan 90 and the outside of the apparatus is provided.
When the exhaust fan 90 rotates, the air inside the fixing unit case 26 is drawn out and is discharged outside the apparatus through the duct 92.

  In the case where a heat fixing unit other than that using the heating roller 80 and the pressure roller 82 is used as the fixing unit 18, the fixing unit case 26 may be provided so as to surround at least the heating region of the fixing unit 18. When the heating unit and the pressure unit are provided separately as the fixing unit 18, the fixing unit case 26 may be provided so as to surround at least the heating unit. When the preheating unit is provided prior to the fixing unit 18, the preheating unit and the fixing unit 18 are preferably surrounded by the same fixing unit case 26 or a separate fixing unit case 26, but in the vicinity of the drawing unit 16. Only the heating means (preliminary heating means) disposed on the fixing unit case 26 may be enclosed.

Further, the fixing unit case 26 is configured such that the fixing unit case 26 (the heat insulating member 96 attached to the main body or the fixing unit case 26) contacts the drawing unit case 20 (the heat insulating member 94 attached to the main body or the drawing unit case 20). Although substantially all of the air discharged from the drawing unit case 20 may be sent to the fixing unit case 26, the drawing unit case 20 (the heat insulating member 94) and the fixing unit case 26 as shown in the drawing. A space is provided between the heat insulating member 96 and the air flow from the inside of the drawing unit case 20 to the outside of both cases, and the flow of air from the outside of both cases to the inside of the fixing unit case 26 is formed. It is preferable to do so.
Furthermore, the wider the space between the drawing unit case 20 and the fixing unit case 26, the lower the possibility that the heat generated in the fixing unit case 26 will reach the inside of the drawing unit case 20.

Next, the solvent recovery means 30 will be described.
In the illustrated image forming apparatus 10, the end of the duct 92 of the exhaust unit 28 opposite to the fixing unit case 26 is connected to the solvent recovery unit 30.
The solvent recovery means 30 recovers the dispersion solvent evaporated from the ink when the image is fixed by the fixing means 18, and has an activated carbon filter. Moreover, the solvent collection | recovery means 30 may be further equipped with the exhaust fan, when the ventilation force of the exhaust fan 90 is not enough to let the activated carbon filter of the solvent collection | recovery means 30 pass, and to discharge | emit gas.

  When the ink solvent evaporates during fixing by the fixing unit 18, the air in the vicinity of the fixing unit 18 contains a dispersed solvent component. The air containing the dispersed solvent component is exhausted from the inside of the fixing unit case 26 by the exhaust fan 90 and passes through the activated carbon filter of the solvent recovery means 30, so that the solvent component is adsorbed and removed by the activated carbon filter, The removed air is discharged to the outside of the housing 11.

In the image forming apparatus 10, there is no problem even if the aqueous solvent is used as the ink solvent, or even if it is a non-aqueous solvent, the solvent-containing air generated at the time of fixing has a low solvent concentration. In some cases or when the solvent recovery means can be attached to the outside of the housing 11, the solvent recovery means 30 may not be provided.
Further, instead of the solvent recovery means 30, a solvent recovery means such as an activated carbon filter may be provided inside the fixing unit case 26. In this case, the air discharged from the fixing unit case 26 is directly connected to the casing from the duct 92. 11 to the outside.

  If the heat insulation effect by the drawing unit case 20 is sufficiently high and the temperature inside the drawing unit case 20 does not affect the temperature inside the drawing unit case 20 slightly, the air inside the fixing unit case 26 is removed. In addition, it may be configured to be discharged into the housing 11. Alternatively, even when the drawing unit case 20 is not provided, the air from the fixing unit case 26 is discharged to a location in the housing 11 that does not affect the drawing unit 16, such as a location sufficiently away from the drawing unit 16. If possible, the air inside the fixing unit case 26 may be discharged into the housing 11. In that case, it is preferable to provide a solvent recovery means for recovering the solvent from the air inside the housing 11 inside the housing 11 as necessary.

  Further, the solvent recovery means draws in order to recover the dispersed solvent that evaporates from the ink ejected at the ejection portion of the inkjet head 68 and the dispersed solvent that spontaneously evaporates from the ink that forms the unfixed image on the recording medium P. It may be provided as appropriate inside the part case 20 or inside the housing 11.

Next, the ejection head of the inkjet head 68 will be described.
As described above, the inkjet head 68 is a line head capable of simultaneously forming an image for one row, and cyan (C), magenta (M), yellow (Y), and yellow for forming a full-color image. A discharge head for four colors of black (B) is provided. Since the discharge heads for the respective colors basically have the same configuration, the discharge head 160 for one color will be described below.

  FIG. 3 is a schematic diagram for explaining a specific structure of the ejection head 160 in the electrostatic inkjet head 68. FIG. 3A is a schematic cross-sectional view showing a part of the ejection head 160, and FIG. FIG. 3B is a schematic cross-sectional view taken along line III-III in FIG. The ejection head 160 is a multi-channel head having a plurality of nozzles two-dimensionally, but here, only two ejection sections are shown in order to clearly show the configuration. FIG. 3 also shows the conveying belt 42 facing the ejection head 160, but the positional relationship between them is shown upside down from FIG.

  The ejection head 160 includes a head substrate 162, an ink guide 164, a nozzle substrate 166, an ejection electrode 168, and a floating conductive plate 176. The ejection head 160 is disposed so that the tip of the ink guide 164 that is the ejection (flying) point of the ink droplet R faces the conveyance belt 42 that supports the recording medium P that serves as a counter electrode.

  The head substrate 162 and the nozzle substrate 166 are flat substrates common to all the nozzles of the ejection head 160, and are made of an insulating material. The head substrate 162 and the nozzle substrate 166 are arranged at a predetermined interval, and an ink flow path 178 is formed therebetween. The ink Q in the ink flow path 178 includes color material particles charged with the same polarity as the voltage applied to the ejection electrode 168. At the time of drawing, the ink circulation mechanism 72 (see FIG. 1) causes the ink Q to flow in a predetermined direction. In the example shown in a), the ink is circulated in the ink flow path 178 from the right side to the left side (in the direction of arrow a in the drawing) at a predetermined speed (for example, an ink flow of 200 mm / s). Hereinafter, a case where the color material particles in the ink are positively charged will be described as an example.

  In the nozzle substrate 166, nozzles 174 serving as ejection openings for the ink Q are perforated, and a plurality of nozzles 174 are two-dimensionally arranged at a predetermined interval. In addition, an ink guide 164 for determining the discharge (flying) point of the ink Q is disposed at the center of the nozzle 174.

  The ink guide 164 is made of an insulating resin flat plate having a predetermined thickness with a projecting tip portion 164 a, and is disposed on the head substrate 162 at a position corresponding to each nozzle 174. The ink guide 164 has a base portion 164b common to a plurality of ink guides 164 arranged in the same row (left-right direction in FIG. 3A, vertical direction in FIG. 3B), and this base portion 164b. Is fixed on the head substrate 162 with the floating conductive plate 176 interposed therebetween.

  The leading end portion 164a of the ink guide 164 is disposed so as to protrude from the outermost surface of the ejection head 160 on the recording medium P (conveying belt 42) side. The shape and configuration of the tip portion 164a stabilizes the discharge point of the ink Q (ink droplet R), and the ink Q is sufficiently supplied at the tip portion 164a to concentrate the colorant particles in the ink Q to a preferable state. It is set so that it can be made. For example, in order to substantially increase the dielectric constant of the tip portion 164a, a shape in which the tip portion 164a is gradually narrowed toward the ejection direction, a notch that forms an ink guide groove is formed in the vertical direction in the figure. A material obtained by evaporating metal on the tip portion 164a is suitable.

  On the surface of the nozzle substrate 166 on the recording medium P side (the upper surface in the drawing), ejection electrodes 168 are arranged so as to surround each nozzle 174. Further, on the recording medium P side of the nozzle substrate 166, an insulating layer 170a covering the upper side (upper surface) of the discharge electrode 168, and a sheet-like guard electrode 172 disposed above the discharge electrode 168 via the insulating layer 170a, And an insulating layer 170b covering the upper surface of the guard electrode 172.

  The discharge electrode 168 is formed in a ring shape, that is, a circular electrode for each discharge portion on the upper side of the nozzle substrate 166 in the drawing, that is, on the surface on the recording medium P side so as to surround the periphery of the nozzle 174 opened in the nozzle substrate 166. Is arranged as. The electrode shape of the ejection electrode 168 is not limited to a circular electrode, and may be a substantially circular shape, a divided circular electrode, a parallel electrode, or a substantially parallel electrode.

  The ejection electrode 168 is controlled by the head driver 70, and a predetermined pulse voltage is applied according to the image data. As described above, the recording medium P charged to a voltage opposite in polarity to the charged color material particles in the ink is held by the conveyor belt 42 at a constant speed at a position facing the ink guide 164. Is done. The recording medium P is charged with a negative high voltage (for example, −1500 V), and a predetermined electric field is formed between the ejection electrode 168 and the ink Q so as not to be ejected.

  When the discharge electrode 168 is in the discharge off state (discharge standby state), the pulse voltage is set to 0 V or a low voltage. In this state, the electric field strength of the ejection portion is the electric field strength due to the bias voltage (or the voltage obtained by superimposing the off-state pulse voltage on the bias voltage), which is lower than the strength necessary for ejecting the ink Q. Since it is set, the ink Q is not ejected. However, due to the low electric field in the discharge standby state, the color material particles in the ink are concentrated in the tip portion 164 a of the ink guide 164 inside the nozzle 174.

  When the ejection electrode 168 is in the ejection-on state, a pulse voltage is applied, and a high-voltage pulse voltage (for example, 400 to 600 V) is superimposed on the bias voltage. The ink Q becomes sufficiently strong and the ink Q concentrated on the tip portion 164a of the ink guide 164 flies as an ink droplet R. Since the size of the ink droplet R is extremely small, high-resolution and high-quality image formation can be performed.

  In this way, on / off of the ejection electrodes 168 of the ejection units arranged over the entire width of the recording medium P is controlled according to the image data, and the recording medium P conveyed at a predetermined speed has a predetermined value. By ejecting ink at the timing, a two-dimensional image is formed on the recording medium P.

  The guard electrode 172 is disposed between the ejection electrodes 168 of the adjacent ejection units, and is for suppressing electric field interference generated between the ink guides 164 of the adjacent ejection units. The guard electrode 172 is a sheet-like electrode such as a metal plate that is common to all the discharge portions of the discharge head 160, and corresponds to the discharge electrode 168 formed around each nozzle 174 that is two-dimensionally arranged. Is perforated. By providing the guard electrode 172, even when the nozzles 174 are arranged at a high density, the influence of the electric field of the adjacent nozzles 174 can be minimized, and the dot size and the dot drawing position can always be kept stable.

  A floating conductive plate 176 is arranged on the surface of the head substrate 162 on the ink flow path 178 side. The floating conductive plate 176 is in an electrically insulated state (high impedance state), and generates an induced voltage in accordance with the voltage value applied to the ejection unit during drawing, and the ink flow path 178 In the ink Q, the color material particles migrate to the nozzle substrate 166 side. In addition, a coating film (not shown) that is electrically insulating is formed on the surface of the floating conductive plate 176 to prevent destabilization of the physical properties and components of the ink due to charge injection into the ink and the like. Has been. As this insulating coating film, one having corrosion resistance to ink is used.

  By providing the floating conductive plate 176, the color material particles in the ink Q in the ink flow path 178 migrate to the nozzle substrate 166 side, and the concentration of the color material particles in the ink Q that passes through the nozzle 174 of the nozzle substrate 166. Can be increased to a predetermined concentration, and the concentration of the colorant particles in the ink Q to be ejected as the ink droplets R can be stabilized at the predetermined concentration by being concentrated on the tip portion 164a of the ink guide 164.

  In the illustrated example, the discharge electrode has a single-layer electrode structure, but in addition to this, for example, a first discharge electrode connected in the column direction and a second discharge electrode connected in the row direction are provided. A two-layer electrode structure may be used, and the first discharge electrode and the second discharge electrode may be arranged in a matrix to perform matrix driving. According to such a matrix driving method, both high integration of ejection electrodes and simplification of driver wiring can be realized simultaneously.

  The ink circulation mechanism 72 includes an ink tank 76, a pump (not shown), an ink supply path 78a, and an ink recovery path 78b. The ink tank 76 is disposed on the bottom surface inside the housing 11 and is connected to the inkjet head 68 via an ink supply path 78a and a recovery path 78b.

  In the ink tank 76, four colors of ink including color material particles of each color and a dispersion solvent for dispersing the color material particles are held. The ink of each color in the ink tank 76 is supplied by the pump to the discharge head of each color of the inkjet head 68 via the ink supply path 78a. Further, the extra ink of each color that was not used for drawing is collected by the pump into the ink tank 76 of each color via the ink collection path 78b.

  Next, the ink Q (ink composition) used in the inkjet head 68 will be described. In the electrostatic ink jet head 68, the ink Q is formed by dispersing color material particles (including color material and charged fine particles) in a solvent (ink solvent, carrier liquid).

The carrier liquid (ink solvent) is preferably a dielectric liquid (nonaqueous solvent) having a high electrical resistivity (10 ⁹ Ω · cm or more, preferably 10 ¹⁰ Ω · cm or more). When a carrier liquid having a high electrical resistivity is used, the carrier liquid itself is less likely to receive charge injection due to the voltage applied by the discharge electrode, and the concentration of charged particles (charged fine particle component) can be increased. Can be concentrated. Further, the carrier liquid having a high electrical resistivity can contribute to prevention of electrical conduction between adjacent ejection electrodes. Further, when ink made of such an electric low-efficiency liquid is used, ink can be ejected satisfactorily even under a low electric field.

The relative dielectric constant of the dielectric liquid used as the carrier liquid is preferably 5 or less, more preferably 4 or less, and still more preferably 3.5 or less. By setting the relative dielectric constant in such a range, an electric field effectively acts on the colorant particles in the carrier liquid, and migration easily occurs.
The upper limit value of the specific electric resistance of such a carrier liquid is preferably about 10 ¹⁶ Ωcm, and the lower limit value of the relative dielectric constant is preferably about 1.9. The reason why it is desirable that the electric resistance of the carrier liquid is in the above range is that if the electric resistance is low, ink ejection under a low electric field is deteriorated, and the reason why the relative dielectric constant is preferably in the above range is the reason. This is because, when the dielectric constant increases, the electric field is relaxed by the polarization of the solvent, and the color of the dots formed thereby becomes thin or causes blurring.

  The dielectric liquid used as the carrier liquid is preferably a linear or branched aliphatic hydrocarbon, alicyclic hydrocarbon, or aromatic hydrocarbon, and halogen-substituted products of these hydrocarbons. For example, hexane, heptane, octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L, Isopar M (isopar: trade name of Exxon), Shellsol 70, Shellsol 71 (shellsol: trade name of Shell Oil), Amsco OMS, Amsco 460 Solvent (trade name of Amsco: Spirits), Silicone oil (for example, KF-96L manufactured by Shin-Etsu Silicone) or the like can be used alone or in combination.

  The color material particles dispersed in such a carrier liquid (ink solvent) may be dispersed in the carrier liquid as the color material itself as color material particles, but preferably the dispersed resin particles for improving the fixing property Containing. When the dispersed resin particles are included, the pigment is generally coated with the resin material of the dispersed resin particles to form resin-coated particles, and the dye is colored with the dispersed resin particles to form colored particles. Is common.

As the color material, any pigments and dyes that have been conventionally used in inkjet ink compositions, printing (oil-based) ink compositions, or electrophotographic liquid developers can be used.
As the pigment used as the color material, regardless of inorganic pigments or organic pigments, those generally used in the technical field of printing can be used. Specifically, for example, carbon black, cadmium red, molybdenum red, chrome yellow, cadmium yellow, titanium yellow, chromium oxide, viridian, cobalt green, ultramarine blue, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment Conventionally known pigments such as quinacridone pigments, isoindolinone pigments, dioxazine pigments, selenium pigments, perylene pigments, perinone pigments, thioindigo pigments, quinophthalone pigments, metal complex pigments, and the like are not particularly limited. Can be used.
As dyes used as coloring materials, azo dyes, metal complex dyes, naphthol dyes, anthraquinone dyes, indigo dyes, carbonium dyes, quinoneimine dyes, xanthene dyes, aniline dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes And oil-soluble dyes such as phthalocyanine dyes and metal phthalocyanine dyes.

Further, as dispersed resin particles, for example, rosins, rosin-modified phenol resins, alkyd resins, (meth) acrylic polymers, polyurethane, polyester, polyamide, polyethylene, polybutadiene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl alcohol, acetal-modified Products, polycarbonate and the like.
Among these, from the viewpoint of ease of particle formation, the weight average molecular weight is in the range of 2,000 to 1,000,000 and the polydispersity (weight average molecular weight / number average molecular weight) is 1.0 to 5 Polymers in the range of 0.0 are preferred. Furthermore, from the viewpoint of ease of fixing, a polymer having any one of a softening point, a glass transition point, and a melting point within a range of 40 ° C. to 120 ° C. is preferable.

  In the ink Q, the content of the color material particles (the total content of the color material particles or further dispersed resin particles) is preferably contained in the range of 0.5 to 30% by weight with respect to the whole ink, and more preferably. Is preferably contained in the range of 1.5 to 25% by weight, more preferably 3 to 20% by weight. If the content of the colorant particles is reduced, problems such as insufficient printed image density or difficulty in obtaining a strong image due to difficulty in obtaining the affinity between the ink Q and the surface of the recording medium P are likely to occur. On the other hand, when the content increases, it becomes difficult to obtain a uniform dispersion liquid, or the ink Q is easily clogged with the inkjet head 68 or the like, and it is difficult to obtain stable ink discharge. It is.

  Moreover, the average particle diameter of the color material particles dispersed in the carrier liquid is preferably 0.1 to 2 μm, more preferably 0.2 to 1.5 μm, and still more preferably 0.4 to 1 μm. This particle size is determined by CAPA-500 (trade name, manufactured by Horiba, Ltd.).

After the colorant particles are dispersed in the carrier liquid (a dispersant may be used if necessary), the chargeant is added to the carrier liquid to charge the colorant particles, and the charged colorant The ink Q is obtained by dispersing particles in a carrier liquid. When dispersing the colorant particles, a dispersion medium may be added as necessary.
As an example of the charge control agent, various materials used in electrophotographic liquid developers can be used. Also, “Recent development and commercialization of electrophotographic development systems and toner materials”, pages 139 to 148, “The Basics and Applications of Electrophotographic Technology” edited by Electrophotographic Society, pages 497 to 505 (Corona Inc., published in 1988), Yuji Harasaki Various charge control agents described in "Electrophotography" 16 (No. 2), p. 44 (1977) can also be used.

  The colorant particles are charged particles having the same polarity as the driving voltage applied to the ejection electrode, and the charge amount is preferably 5 to 200 μC / g, more preferably 10 to 150 μC / g, and still more preferably 15 It is in the range of ˜100 μC / g.

In addition, since the electric resistance of the dielectric solvent may change due to the addition of the charge control agent, the distribution ratio P defined below is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. And
P = 100 × (σ1−σ2) / σ1
Here, σ1 is the electrical conductivity of the ink Q, and σ2 is the electrical conductivity of the supernatant obtained by applying the ink Q to the centrifuge. The electrical conductivity was measured using an LCR meter (AG-4311 manufactured by Ando Electric Co., Ltd.) and an electrode for liquid (LP-05 type manufactured by Kawaguchi Electric Manufacturing Co., Ltd.) under the conditions of an applied voltage of 5 V and a frequency of 1 kHz. This is the measured value. Centrifugation was performed for 30 minutes using a small high-speed cooling centrifuge (Tomy Seiko Co., Ltd. SRX-201) under conditions of a rotational speed of 14500 rpm and a temperature of 23 ° C.
By using the ink Q as described above, migration of charged particles is likely to occur and concentration is facilitated.

The electrical conductivity of the ink Q is preferably 100 to 3000 pS / cm, more preferably 150 to 2500 pS / cm, and still more preferably 200 to 2000 pS / cm. By setting the electric conductivity in the above range, the voltage applied to the ejection electrodes does not become extremely high, and there is no fear of causing electrical continuity between adjacent ejection electrodes.
The surface tension of the ink Q is preferably in the range of 15 to 50 mN / m, more preferably 15.5 to 45 mN / m, and still more preferably 16 to 40 mN / m. By setting the surface tension within this range, the voltage applied to the ejection electrode does not become extremely high, and the ink does not leak around the head and become contaminated.
Furthermore, the viscosity of the ink Q is preferably 0.5 to 5 mPa · sec, more preferably 0.6 to 3.0 mPa · sec, and still more preferably 0.7 to 2.0 mPa · sec.

As an example, such an ink Q can be prepared by dispersing color material particles in a carrier liquid to form particles, and adding a charge adjusting agent to the dispersion medium to cause the color material particles to be charged. Specific methods include the following methods.
(1) A method in which a color material or further dispersed resin particles are mixed (kneaded) in advance, and then dispersed in a carrier liquid using a dispersant as required, and a charge adjusting agent is added.
(2) A method in which a coloring material, or further dispersed resin particles and a dispersing agent are simultaneously added to a carrier liquid, dispersed, and a charge adjusting agent is added.
(3) A method in which a coloring material and a charge adjusting agent, or further dispersed resin particles and a dispersing agent are simultaneously added to a carrier liquid and dispersed.

Hereinafter, the operation of the image forming apparatus 10 will be described.
At the start of drawing, the recording medium P stored in the paper feed tray 34 is picked up one by one by the pickup roller 36 and is nipped and conveyed by the conveying roller pair 40, and then the inside of the drawing unit case 20 from the opening 20 a of the drawing unit case 20. It is carried in and supplied to a predetermined position on the conveyor belt 42. The recording medium P supplied on the conveyance belt 42 is charged to a negative high potential by the charger 48 and is electrostatically attracted to the surface of the conveyance belt 42.

The recording medium P electrostatically attracted to the surface of the transport belt 42 is moved at a predetermined constant speed as the transport belt 42 is moved, and an image corresponding to image data is formed on the surface of the recording medium P by the ink jet head 68.
Here, the drawing portion by the ink jet head 68 is surrounded by the drawing portion case 20, and outside air adjusted in temperature is introduced into the drawing portion case 20 from the outside air introduction port 20c, and the inside from the openings 20a and 20b. By discharging the air, the inside of the drawing unit case 20 is maintained at a substantially constant temperature, so that the ejection performance of the inkjet head 68 can be stably maintained.

The recording medium P after image formation (drawing) is neutralized by the static eliminator 50, separated from the transport belt 42 by the separation claw 52, discharged from the opening 20 b of the drawing unit case 20, and then the fixing unit case 26. The toner is carried into the fixing unit case 26 from the opening 26 a and supplied to the fixing unit 18.
In the fixing unit 18, the recording medium P is nipped and conveyed by the heating roller 20 and the pressure roller 22, whereby the unfixed image formed on the recording medium P is fixed.
Here, since the fixing unit 18 is surrounded by the fixing unit case 26, the air heated by the fixing unit 18 does not diffuse around. Further, since the air heated by the fixing unit 18 inside the fixing unit case 26 is discharged from the vent 26c to the outside of the housing 11, the influence of the heat generated by the fixing unit 18 on the drawing unit 16 is affected. Can be suppressed. Therefore, the ink is not dried or clogged in the ink discharge portion of the ink jet head 68, and a stable amount of ink can always be discharged from the ink jet head 68. An image can be formed on the recording medium P.

  The recording medium P that has passed through the fixing unit 18 is unloaded from the opening 26 b of the fixing unit case 26, discharged to the discharge tray 38 by the discharge roller 54, and stocked in the discharge tray 38.

Next, a second embodiment of the present invention will be described with reference to FIG.
In the first embodiment, the fixing unit case 26 is discharged from the inside of the fixing unit case 26 by the exhaust unit 28 to the outside of the housing 11 by discharging the air heated by the heat generated in the fixing unit 18. The internal heat of the case was discharged to prevent the environmental temperature inside the case from increasing, and the air heated by the fixing unit 18 was prevented from moving toward the drawing unit 16 (the drawing unit case 20).
In contrast, in the present embodiment, instead of the exhaust unit 28, a blower unit (outside air introduction unit) for sending air into the fixing unit case 26 is provided, and the outside air is sent to the fixing unit case 26, and the fixing unit case 26. The heated air inside is then discharged out of the fixing unit case 26.

FIG. 2 is a conceptual diagram showing the configuration of the second embodiment of the inkjet image forming apparatus of the present invention. Inkjet image forming apparatus 100 shown in FIG.
Is an electrostatic inkjet image forming apparatus similar to the image forming apparatus 10 described above. The image forming apparatus 100 is different from the image forming apparatus 10 in that the image forming apparatus 100 includes a blowing unit 102 that blows outside air to the fixing unit case 26 instead of the exhaust unit 28 that discharges heated air from the fixing unit case 26. In other respects, the configuration is basically the same as that of the image forming apparatus 10 in FIG. 1, and therefore, the same components are denoted by the same reference numerals, and different points will be mainly described below.

In the image forming apparatus 100, a blowing unit 102 is connected to the vent 26 c of the fixing unit case 26.
The blower unit 102 sends air outside the housing 11 into the fixing unit case 26. The blowing unit 104 is attached to the vent 26c and the outside of the blowing fan 104 (the fixing unit case 26). And a duct 108 that connects the blower fan 104 and the filter 106 to the outside of the apparatus.

When the blower fan 104 rotates, outside air is taken in from the connection port of the duct 108 to the outside of the apparatus, and the taken-in outside air is removed by the filter 106 and is sent to the inside of the fixing unit case 26.
The outside air sent from the vent 26 c flows from the vent 26 c to the opening 26 a or 26 b inside the fixing unit case 26 and is exhausted from the openings 26 a and 26 b to the outside of the drawing unit case 20. As for the amount of outside air fed by the blowing means, the amount (momentum) of air discharged from the openings 26a and 26b (particularly the opening 26a) is discharged from the openings 20a and 20b (particularly the opening 20b) of the drawing unit case 20. It is set to be equal to or slightly smaller than the amount of air (momentum).

  The high-temperature air discharged from the opening 26a is directed toward the drawing unit case 20, but the air inside the drawing unit case 20 is also discharged from the opening 20b of the drawing unit case 20 with an equal or slightly strong momentum. Therefore, high-temperature air from the fixing unit case 26 is suppressed from entering the drawing unit case 20, and collides between the drawing unit case 20 and the fixing unit case 26, and the drawing unit case 20 and the fixing unit case 26. Head in any direction between. As a result, the temperature inside the fixing unit case 26 can be prevented from becoming excessively high, the ambient temperature can be prevented from rising, and the influence of the heat generated in the fixing unit 18 on the drawing unit 16 can be reduced. Can be prevented.

In the present embodiment, it is desirable to provide the drawing unit case 20. Alternatively, the air in the fixing unit case 26 may be positively discharged from an opening different from the opening 26 a and hardly discharged from the opening 26 a so that the heated air does not go to the drawing unit 16.
When the drawing unit case 20 is provided, the drawing unit case 20 (the heat insulating member 94 attached to the main body or the drawing unit case 20) and the fixing unit case 26 (the heat insulating member 96 attached to the main body or the fixing unit case 26). ), It is essential to secure an interval for releasing the air discharged from both cases.
Furthermore, it is preferable to provide a solvent recovery means 30 for recovering the solvent from the air in the entire interior of the housing 11 at an appropriate location inside the housing 11 as in the illustrated example.

  The inkjet image forming apparatus according to the present invention has been described in detail above. However, the present invention is not limited to the various embodiments described above, and various improvements and modifications may be made without departing from the spirit of the present invention. Of course.

1 is a conceptual diagram illustrating a configuration of a first embodiment of an inkjet image forming apparatus of the present invention. It is a conceptual diagram which shows the structure of 2nd Embodiment of the inkjet image forming apparatus of this invention. 2 is a conceptual diagram illustrating a configuration of a discharge head 160 of an inkjet head 68 in the image forming apparatus 10, where (a) is a schematic cross-sectional view illustrating a part of the discharge head 160, and (b) is a III- It is a typical sectional view in line III.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 100 Inkjet image forming apparatus 11 Case 12 Holding means 14 Conveying means 16 Drawing means (image forming means)
DESCRIPTION OF SYMBOLS 18 Fixing means 20 Drawing part case 20a, 20b Opening 20c Outside air introduction port 22 Outside air introduction means 24 Temperature control means 26 Fixing part case 26a, 26b Opening 26c Air discharge port 28 Exhaust means 30 Solvent collection means 68 Inkjet head 70 Head driver 72 Ink Circulation mechanism 80 Heating roller (fixing roller)
82 Pressure roller 84, 98 Outside air introduction fan 86, 99 Filter 88 Duct 90 Exhaust fan 92 Duct 94, 96 Heat insulation member 102 Blowing means 104 Blower fan 106 Filter 160 Discharge head

Claims (6)

An image forming unit that has an ink discharge unit that discharges ink toward a recording medium, and forms an image by attaching the discharged ink to the recording medium;
Conveying means for conveying the recording medium;
Heating means for the recording medium disposed downstream of the image forming means in the conveying direction of the recording medium;
An inkjet image forming apparatus comprising: a heating part case that surrounds the heating means, and has a carry-in port and a carry-out port for the recording medium, and a vent hole communicating with the outside of the case.   The inkjet image forming apparatus according to claim 1, further comprising a discharge unit that discharges the heated air in the heating unit case from the vent.   The inkjet image forming apparatus according to claim 2, wherein the discharge unit discharges the heated air in the heating unit case to the outside of the inkjet image forming apparatus.   The inkjet image forming apparatus according to claim 1, further comprising a blowing unit that sends air from the vent into the heating unit case.   The inkjet image forming apparatus according to claim 1, wherein at least a part of the heating unit case is made of a heat insulating material. The ink contains particles including a charged color material and a solvent,
6. The image forming unit forms an image on the recording medium by ejecting ink droplets from the ink ejection unit by applying an electrostatic force to the ink. An ink jet image forming apparatus according to claim 1.

Images