JP2013052999A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that reliably conveys a recording medium on which an image is formed, and suppresses the generation of wrinkle and twist on the recording medium.SOLUTION: The image forming apparatus 1 includes: a conveying member 51 for holding and conveying the recording medium of which the image is formed on a conveying surface; a pressing member 52 arranged opposite to the conveying surface; and a pressing release means for repeating a motion of separating the pressing member 52 from the conveying surface to come close to the conveying surface, with respect to the recording medium conveyed by the conveying member 51.

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that conveys a recording medium on which an image on a conveying surface is formed by pressing a recording medium with a pressing member.

  The following Patent Document 1 discloses an ink jet recording apparatus. The ink jet recording apparatus includes a recording head that ejects ink, a drum rotating body that supports the recording medium, a holding mechanism that supports the recording medium on the drum rotating body, a control unit that controls the holding mechanism, and a drum rotating body. And a heating mechanism that is disposed so as to apply heat energy to the recording medium. The recording head discharges ink and records an image on a recording medium. After the recording medium is held on the drum rotating body by the holding mechanism, thermal energy is applied to the recording medium by the heating mechanism, and the drying or curing reaction of the recording medium is promoted. Thereafter, the holding mechanism releases the holding of a part of the recording medium and holds it again. These operations of the holding mechanism are controlled by the control unit.

  According to the ink jet recording apparatus configured as described above, even when heat energy is applied to the recording medium to promote the drying or curing reaction of the ink, the recording medium is prevented from wrinkling or floating and high-definition image recording is performed. There are features that can be performed.

  Patent Document 2 below discloses an image forming apparatus. The image forming apparatus includes a recording medium width detecting unit that detects the width of the recording medium in a direction perpendicular to the conveying direction of the recording medium in the process of conveying the recording medium and fixing the recorded image. The width of the recording medium detected by the recording medium width detecting means is subtracted from the width of the normal recording medium obtained in advance. If a difference greater than a certain value is detected, it is assumed that an abnormal state of wrinkling or wrinkling has occurred in the recording medium, and the recording medium is ejected without performing the transporting and fixing processes of the recording medium when the abnormality occurs. .

  According to the image forming apparatus configured as described above, occurrence of wrinkling or curling of the recording medium is detected, and damage to the roller or the like due to jamming or curling or curling of the recording medium is detected in the transporting and fixing processes of the recording medium. Can be prevented.

JP 2007-144773 A JP 2003-63691 A

  However, in the ink jet recording apparatus described in Patent Document 1, after the recording medium is heated by the heating mechanism, the holding of the recording medium is released by the holding mechanism, but immediately after that, the recording medium is pressed again by the roller. . For this reason, depending on the distorted state generated in the recording medium, wrinkles may be generated when the recording medium is pressed again using a roller. In addition, the simple release of the recording medium held by the holding mechanism cannot cope with the point of preventing wrinkles against various deformations of the recording medium.

  Further, in the image forming apparatus described in Patent Document 2, a recording medium width detection unit is used, and a recording medium is used when an abnormal situation such as a wrinkle or a wrinkle occurs in the recording medium from the width of the recording medium obtained in advance. Has been discharged. For this reason, a recording medium with the possibility of occurrence of wrinkles and wrinkles can be excluded, but it is not a fundamental solution for preventing wrinkles and wrinkles.

  In consideration of the above-described facts, the present invention provides an image forming apparatus that can reliably convey a recording medium on which an image is formed and can suppress the occurrence of wrinkling and wrinkling of the recording medium.

  In order to solve the above-described problem, an image forming apparatus according to claim 1 includes a conveyance member that holds and conveys a recording medium on which an image is formed on a conveyance surface, and a pressing member that is disposed to face the conveyance surface. And a press release unit that repeats the operation of separating the pressing member from the conveyance surface and bringing it close to the conveyance surface with respect to the recording medium conveyed by the conveyance member.

  According to the first aspect of the present invention, the transport member holds and transports the recording medium on which the image is formed on the transport surface. The recording medium partially expands as the image is formed. If the recording medium is continuously pressed by the pressing member, wrinkles and wrinkles occur. Since the pressing member is repeatedly separated from the conveying surface by the pressing release means, it is possible to release the distortion that causes the wrinkles and wrinkles before wrinkles and wrinkles occur. On the other hand, the press release means can repeatedly bring the transport member close and press and hold the recording medium on the transport surface by the press member, so that the recording medium can be stably held and transported on the transport surface. By stably holding and transporting the recording medium, it is possible to prevent the recording medium from being disturbed by the air current, and to prevent damage such as deformation and breakage of the recording medium. In addition, as a result of preventing the recording medium from being damaged, it is possible to prevent a reading failure of a position sensor that reads the conveying position of the recording medium, and to prevent a conveying failure.

  An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, wherein the pressing member is a conveying roller disposed across both sides of the conveying surface, and the pressing release means is a side portion of the conveying surface. And a guide member having a convex portion on which an end of the pressing member rides as the transport surface moves in the transport direction.

  According to the invention described in claim 2, the pressing member is constituted by a conveying roller straddling both sides of the conveying surface. The pressing release means includes a guide member having a convex portion that the transport roller rides on. Since the approaching operation and the separating operation of the conveying roller can be repeatedly performed using the convex portion of the guide member, the structure of the pressing release means can be easily realized.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the guide roller has an outer diameter that is the same as the outer diameter of the conveying roller, while climbing a convex portion at the end of the conveying roller. Is provided.

  According to the invention which concerns on Claim 3, the guide roller which rides on the convex part of a guide member at the edge part of a conveyance roller is arrange | positioned. The guide roller rotates along the convex portion when riding on the convex portion, and this rotational force is transmitted to the conveying roller. Even when the transport roller is separated from the transport surface, the transport roller is rotated by the rotational force transmitted from the guide roller, so that there is no relative speed difference between the transport speed (rotational speed) of the transport roller and the transport speed of the recording medium. Therefore, the recording medium can be transported smoothly.

  An image forming apparatus according to a fourth aspect is the image forming apparatus according to the second or third aspect, wherein at least the conveyance roller between the position where the conveyance roller is closest to the conveyance surface and the position immediately before the convex portion. The shape is a curved surface shape in which the proximity speed of the conveyance roller becomes slower than the conveyance speed of the conveyance surface as it approaches the closest position from immediately before.

  According to the fourth aspect of the present invention, the convex portion has a curved surface shape in which the proximity speed of the conveyance roller is slower than the conveyance speed of the conveyance surface as the convex portion approaches the closest position. The curved surface shape only needs to be formed immediately after the position where the transport rollers are most separated from the closest position. Since the proximity speed decreases as the conveyance roller approaches the conveyance surface, the impact of the conveyance roller on the recording medium conveyed on the conveyance surface can be reduced. Therefore, even if the conveyance roller repeatedly approaches and presses the recording medium, it is possible to prevent the recording medium from being damaged.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the pressing release means includes a biasing member that biases the pressing member toward the conveying surface.

  According to the invention described in claim 5, the urging member urges the pressing member toward the conveying surface. Since the pressing member presses the recording medium against the conveying surface, the recording medium can be conveyed faithfully with respect to the movement of the conveying surface in the conveying direction. On the other hand, the pressing member is pressed against the convex portion of the guide member by the urging member, and the pressing member can be moved faithfully to the shape of the convex portion.

  An image forming apparatus according to a sixth aspect is the image forming apparatus according to any one of the second to fourth aspects, wherein the conveying member is an impression cylinder that conveys the recording medium while rotating, and the guide member is conveyed. It has a fastening long hole extending in the direction, and is detachably attached to the side wall of the impression cylinder through a fastening long hole by a fastening member.

  According to the invention described in claim 6, the guide member is detachably attached to the side portion of the impression cylinder using the fastening member. The guide member has a fastening slot extending in the transport direction, and the guide member can be appropriately moved along the fastening slot in the transport direction. Therefore, it is possible to adjust the operation timing for separating and approaching the pressing member according to the image formed on the recording medium, and to appropriately release the distortion of the recording medium that occurs according to the image.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the first aspect, the pressing release means is connected to the pressing member, and an actuator that moves the pressing member away from and close to the conveying surface, and the actuator is separated. And a control unit that repeatedly controls the operation and the approaching operation.

  According to the invention described in claim 7, the pressing release means is configured to include an actuator connected to the pressing member and a control unit for repeatedly controlling the operation thereof. The pressing release means can be realized by a simple configuration of the actuator and the control unit.

  The image forming apparatus according to claim 8 is the image forming apparatus according to claim 7, wherein the control unit stops the operation of the actuator when the thickness of the recording medium is equal to or greater than the set thickness, and the thickness of the recording medium is determined. Is less than the set thickness, the operation of the actuator is executed, and the operation of the actuator is controlled according to the type of thickness of the recording medium.

  According to the eighth aspect of the present invention, when the thickness of the recording medium is equal to or greater than the set thickness, the recording medium is stiff, and even if the recording medium is pressed by the pressing member, it is difficult to buckle and hardly cause wrinkles. . When the thickness of the recording medium is less than the set thickness, the recording medium is weak, and when the recording medium is pressed by the pressing member, it tends to buckle and wrinkle easily. The set thickness is threshold information set in advance, and is set to, for example, 157 gsm in the case of plain paper. When the thickness of the recording medium is equal to or greater than the set thickness, the control unit performs control to stop the operation of the actuator, so that the press release means is not operated unnecessarily in the conveyance of the recording medium in which wrinkles are unlikely to occur. . When the thickness of the recording medium is less than the set thickness, the control unit performs control to execute the operation of the actuator, and operates the press releasing means to suppress the occurrence of wrinkling and wrinkling in the conveyance of the recording medium. it can.

  An image forming apparatus according to a ninth aspect is the image forming apparatus according to the seventh aspect, wherein the control unit controls the operation of the actuator in accordance with the type of image on the recording medium.

  According to the ninth aspect of the present invention, depending on the direction of the fiber flow relative to the conveyance direction of the recording medium and the type of image (pattern of the image formation region)

The forms of wrinkles and wrinkles that occur on the recording medium are different. Since the pressing member can be separated from the transport surface and brought close to the transport surface according to the form of the wrinkle or curl, the recording medium can be reliably held and transported while the recording medium is curled or twisted. Can be prevented.

  An image forming apparatus according to a tenth aspect is the image forming apparatus according to the first aspect, wherein the pressing member is a conveying roller disposed across both sides of the conveying surface, and the press releasing means is disposed on the conveying roller. And a pressing release groove that is recessed closer to the axial center side than the pressing surface of the conveying roller.

  According to the invention described in claim 10, since the pressing member is constituted by the conveying roller and the pressure releasing means is constituted by the pressing releasing groove provided in the conveying roller, the pressing releasing means is realized by a simple configuration. be able to.

  An image forming apparatus according to an eleventh aspect is the image forming apparatus according to any one of the first to tenth aspects, wherein ink is applied to the recording medium upstream of the conveying member and the pressing member of the conveying unit in the conveying direction. An image forming unit for forming a discharged image is provided.

  According to an eleventh aspect of the present invention, the image forming apparatus is an ink jet type image forming apparatus including an image forming unit that ejects ink onto a recording medium. Since this image forming apparatus forms an image on a recording medium using ink containing a lot of moisture, the extension of the area on the recording medium where the image is formed (the area where the ink is attached) is compared with the area where the image is not formed. Large, the recording medium is likely to wrinkle or wrinkle due to the difference in elongation. Therefore, it is effective for this type of image forming apparatus.

  According to the present invention, since the above-described configuration is provided, an image forming apparatus that can reliably transport the recording medium on which an image is formed and can suppress the occurrence of wrinkling and wrinkling of the recording medium is provided. can do.

1 is a conceptual diagram illustrating an overall configuration of an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a perspective view of a fixing unit of the image forming apparatus illustrated in FIG. 1. FIG. 3 is an enlarged side view of a main part of the fixing unit shown in FIG. 2. FIG. 3 is an enlarged front view of a main part of a fixing unit shown in FIG. 2. It is a schematic diagram which shows the shape of the press release means of the fixing part shown in FIG. (A) The figure which shows the relationship between the operation | movement of the press release means of the image forming apparatus which concerns on Example 1, and the recording medium in which the image was formed, (b) The other recording media in which the operation | movement of the press release means and the image were formed (C) is a diagram showing the relationship between the operation of the press release means and the recording medium on which another image is formed. FIG. 6 is an enlarged configuration diagram of a main part including a fixing unit and a pressure release unit of an image forming apparatus according to a second embodiment of the present invention. FIG. 6 is an enlarged front view of a main part including a fixing unit and a pressure release unit of an image forming apparatus according to a third embodiment of the present invention. It is a principal part expansion perspective view of the fixing | fixed part and press release means shown in FIG. FIG. 10 is a cross-sectional view of a pressing member (conveying roller) and a pressing release unit of the fixing unit illustrated in FIGS. 8 and 9.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings. In the following description, components having the same function are denoted by the same reference numerals, and the description thereof is omitted because it is redundant.

Example 1
Embodiment 1 of the present invention describes an example in which the present invention is applied to an ink jet type image forming apparatus as an image forming apparatus.

<Overall configuration of image forming apparatus>
As shown in FIG. 1, the image forming apparatus 1 according to the embodiment mainly includes a paper feeding unit 10, a processing liquid application unit 20, a drawing unit 30, a drying unit 40, a fixing unit 50, and a paper discharge unit 60. . The image forming apparatus 1 applies recording agents of each color from ink jet recording heads 32K, 32M, 32C, and 32Y as an example of a droplet discharge device to a recording medium 2 held on a drawing drum (impression cylinder) 31 of a drawing unit 30. A color image is formed by discharging. The recording medium 2 is, for example, paper. In addition, black, magenta, cyan, and yellow color inks are used as recording agents. This type of image forming apparatus 1 is an impression type direct drawing type ink jet recording apparatus. Further, the image forming apparatus 1 applies a treatment liquid (ink aggregation treatment liquid) onto the recording medium 2 before discharging the recording agent, and reacts the treatment liquid with the recording agent to form an image on the recording medium 2. An on-demand type image forming apparatus employing a two-component reaction (aggregation) system.

  The paper supply unit 10 is a mechanism that supplies the recording medium 2 to the processing liquid application unit 20. A recording medium 2 that is a sheet is stacked on the paper supply unit 10. The paper feed unit 10 is provided with a paper feed tray 11. The paper feed tray 11 feeds the recording medium 2 one by one to the processing liquid application unit 20. The image forming apparatus 1 can form images on various recording media 2 having different paper types and paper sizes. In the first embodiment, a sheet paper (cut sheet) is used as the recording medium 2 and an image forming method will be described.

  The processing liquid application unit 20 is a mechanism that applies the processing liquid to the recording surface (image forming surface) of the recording medium 2. The treatment liquid is a recording agent applied in the drawing unit 30, here ink, and includes a component that aggregates or thickens the color material (pigment or dye) in the ink. When the treatment liquid comes into contact with the ink, separation of the ink coloring material and the solvent is promoted.

  In order to agglomerate or thicken the color material, for example, a treatment liquid that reacts with the ink to precipitate or insolubilize the color material in the ink, or a process that generates a semi-solid substance (gel) containing the color material in the ink. Use of a liquid etc. is mentioned. The method for causing the reaction between the ink and the treatment liquid includes a method in which the anionic coloring material in the ink and the cationic compound in the treatment liquid are reacted, and an ink having a different pH and the treatment liquid are mixed. The method of agglomerating the pigment by changing the pH of the ink by causing dispersion of the pigment in the ink, the method of causing the dispersion destruction of the pigment in the ink by reaction with the polyvalent metal salt in the treatment liquid, and the like is there. As a method for applying the treatment liquid, there are a method for ejecting the treatment liquid, a method for applying using a roller, a method for uniformly spraying using a spray, and the like.

  The treatment liquid application unit 20 includes a supply cylinder 21, a treatment liquid drum 22, and a treatment liquid application device 23. The treatment liquid drum 22 is a drum that holds the recording medium 2 and conveys the recording medium 2 while rotating. Although not shown in detail, on the outer peripheral surface of the treatment liquid drum 22, holding means (grippers) having claws that sandwich the end of the recording medium 2 in the transport direction are disposed.

  Similarly, although not shown in detail, a suction hole is provided on the outer peripheral surface of the treatment liquid drum 22, and suction means for performing suction is connected to the suction hole. The recording medium 2 can be held in close contact with the peripheral surface of the treatment liquid drum 22 by the suction holes and suction means. The peripheral surface of the treatment liquid drum 22 functions as a transport surface (transport path) of a transport unit that transports the recording medium 2.

  The processing liquid coating device 23 is disposed to face the outer peripheral surface of the processing liquid drum 22. The processing liquid coating device 23 is in pressure contact with the processing liquid container in which the processing liquid is stored, the anilox roller partially immersed in the processing liquid in the processing liquid container, and the recording medium 2 on the anilox roller and the processing liquid drum 22. And a rubber roller for transferring the measured processing liquid to the recording medium 2. In the processing liquid coating device 23, the processing liquid can be applied to the recording medium 2 while being measured. In the treatment liquid application unit 20, a warm air heater 25 and a heater 26 for drying the treatment liquid applied to the recording medium 2 are sequentially disposed downstream of the treatment liquid application device 23 in the conveyance direction of the recording medium 2. ing. The hot air heater 25 and the heater 26 dry the solvent component in the treatment liquid after the treatment liquid has been deposited, and prevent the color material from floating. The color material floating is a phenomenon in which ink droplets float on the processing liquid and dots cannot be formed at a desired position. As the heater 26, an infrared heater (IR heater) is used in the first embodiment. The IR heater efficiently heats an object having a high water content and is suitable for drying moisture.

  The recording medium 2 to which the processing liquid is applied in the processing liquid applying unit 20 is transferred from the processing liquid drum 22 to the drawing drum 31 of the drawing unit 30 through the transfer drum 71 of the intermediate transport unit 70. The drawing unit 30 holds the recording medium 2 on the peripheral surface and conveys it while rotating, and forms an image on the recording medium 2 using a recording agent (ink) facing the outer peripheral surface of the drawing drum 31. And an image forming unit 32. The image forming unit 32 is provided with ink jet recording heads 32K, 32Y, 32M, and 32C that discharge color inks from the nozzles. The recording head 32K discharges black ink as a recording agent. Similarly, the recording head 32Y ejects yellow ink as a recording agent. The recording head 32M discharges magenta ink as a recording agent. The recording head 32C discharges cyan ink as a recording agent. Similar to the treatment liquid drum 22, the drawing drum 31 includes a holding unit having a claw that sandwiches the conveyance direction end of the recording medium 2 on the outer peripheral surface thereof.

  In the image forming apparatus 1 according to the first embodiment, the recording heads 32K, 32Y, 32M, and 32C of the image forming unit 32 have a length corresponding to the maximum width of the image forming area, and adopt a full-line inkjet method. . Although not shown, nozzle ejection port arrays in which a plurality of nozzle ejection ports are arranged over the entire width of the image forming area are disposed on the respective ink ejection surfaces of the recording heads 32K, 32Y, 32M, and 32C. That is, the nozzle discharge port array extends in a direction orthogonal to the conveyance direction of the recording medium 2 (the rotation direction of the drawing drum 31).

  Although not shown, a suction hole is provided on the outer peripheral surface of the drawing drum 31, and this suction hole is connected to a suction device. The suction force working from the suction device through the suction hole sucks the recording medium 2 to the outer peripheral surface of the drawing drum 31, and the recording medium 2 is held in close contact with the outer peripheral surface of the drawing drum 31.

  Ink is ejected from the recording heads 32K, 32Y, 32M, and 32C to the image forming surface (recording surface) of the recording medium 2 held on the outer peripheral surface of the drawing drum 31, respectively. As described above, since the treatment liquid is applied to the recording surface in advance in the treatment liquid application unit 20, when the ink comes into contact with the treatment liquid, the pigment and the resin particles dispersed in the ink are aggregated to generate an aggregate. . By generating this condensate, an image can be formed on the recording surface of the recording medium 2 while suppressing problems such as pigment flow on the recording medium 2.

  As shown in FIG. 1, the recording medium 2 on which an image is formed in the drawing unit 30 is transferred from the drawing drum 31 to the drying drum (pressure drum) 41 of the drying unit 40 through the transfer drum 73 of the intermediate conveyance unit 72. The drying unit 40 is a mechanism that blows away moisture contained in the solvent in the ink, that is, the solvent separated by the aggregation action, and dries the image. The drying unit 40 includes a drying drum 41, hot air heaters 42a to 42d and heating heaters 43a to 43c disposed on the recording surface side of the recording medium 2 conveyed on the outer peripheral surface thereof, and a recording medium 2 (not shown). And a heating mechanism disposed on the opposite side of the recording surface.

  Here, four warm air heaters 42a to 42d are arranged at regular intervals from the upstream side in the transport direction of the recording medium 2 toward the downstream side in the transport direction. The number of arrangement of the hot air heaters 42a to 42d is not particularly limited. The warm air heaters 42a to 42d heat the ink (recording agent) discharged from the drawing unit 30 to the recording medium 2 with warm air (dry it with heat and air), and dry the image.

  Three heaters 43a, 43b, and 43c are arranged at regular intervals from the upstream side in the transport direction of the recording medium 2 to the downstream side in the transport direction. The heater 43a is disposed between the warm air heaters 42a and 42b, the heater 43b is disposed between the warm air heaters 42b and 42c, and the heater 43c is disposed between the warm air heaters 42c and 42d. Has been placed. The number of heaters 43a-43c arranged is not particularly limited. In the first embodiment, as the heaters 43a to 43c, an IR heater that can efficiently heat an object having a high water content and is suitable for drying moisture is used. Furthermore, a carbon heater in which carbon fibers are enclosed in a quartz tube using an inert gas is effective in reducing power consumption.

  As the heating mechanism, for example, a mechanism is used in which a heating member is pressed from the opposite side of the recording surface of the recording medium 2 to directly transfer heat by contact to heat the ink and dry the image. The surface temperature of the drying drum 41 is preferably set to, for example, 50 ° C. or more using an internal heating mechanism. Drying is accelerated by heating from the opposite side of the recording surface of the recording medium 2, and image destruction during fixing can be prevented. The upper limit of the surface temperature of the drying drum 41 is not particularly limited, but from the viewpoint of safety of maintenance work such as removal of ink attached to the surface of the drying drum 41 by cleaning (preventing burns due to high temperature). It is set to 75 ° C. or lower (preferably 60 ° C. or lower).

  In addition, the higher the surface temperature of the drying drum 41 is, the larger the expansion and contraction of the recording medium 2 is. Therefore, by setting it lower within a range where the drying property can be ensured, the occurrence of curling and cockle of the recording medium 2 can be suppressed. .

  Similar to the treatment liquid drum 22, the drying drum 41 includes a holding unit having a claw that sandwiches the conveyance direction end of the recording medium 2 on the outer peripheral surface thereof. The drying unit 40 holds the recording surface of the recording medium 2 on the outer peripheral surface of the drying drum 41 with the recording surface of the recording medium 2 outside, and the recording surface of the recording medium 2 is curved in a convex shape along the curvature of the outer peripheral surface of the drying drum 41. Dry while rotating. Therefore, by adopting such a conveyance mode, it is possible to prevent the recording medium 2 from wrinkling and floating, and to prevent dry spots caused by these.

  The recording medium 2 subjected to the drying process in the drying unit 40 is transferred from the drying drum 41 to the fixing drum 51 of the fixing unit 50 through the transfer cylinder 75 of the intermediate conveyance unit 74. The fixing unit 50 is not shown in FIG. 1, although a fixing drum 51 that functions as a conveying member, a fixing conveying roller 52 that is disposed on the outer peripheral surface of the fixing drum 51 and functions as a pressing member, is omitted in detail later. And press release means to be described. Further, an inline sensor 66 is disposed at a position facing the outer peripheral surface of the fixing drum 51 and downstream of the transport roller 52 in the transport direction.

  Similar to the processing liquid drum 22, the fixing drum 51 includes a holding unit having a claw 53 (see FIGS. 6A to 6C) that sandwiches an end of the recording medium 2 in the conveyance direction. . By the rotation of the fixing drum 51, the recording medium 2 is conveyed with the recording surface facing outward, and fixing processing by the conveying roller 52 is performed on the recording surface. Further, an inspection by the inline sensor 66 is performed.

  The conveyance roller 52 heats and pressurizes the recording agent (ink here) formed on the recording surface of the recording medium 2. By this heating and pressurization, resin particles, particularly self-dispersing polymer particles, contained in the ink are welded to form a film of the ink. Specifically, the conveyance roller 52 functions as a nip roller that presses the fixing drum 51 and sandwiches the recording medium 2 between the conveyance roller 52 and the conveyance surface of the fixing drum 51. The nip pressure is set to 0.3 MPa, for example, and the fixing process is performed at this nip pressure.

  In the first embodiment, the transport roller 52 has a heating function in which a halogen lamp is incorporated in a hollow pipe made of metal such as aluminum having good thermal conductivity, and the whole pipe is heated by lighting the halogen lamp. The conveyance roller 52 is adjusted to a temperature of 60 ° C. to 80 ° C., for example.

  By heating the recording medium 2 while transporting the recording medium 2 using the transport roller 52, thermal energy equal to or higher than the glass transition temperature (Tg) of the resin particles (latex) contained in the ink can be applied to the ink. As a result, the resin particles are melted, and the melted resin particles are pressed into the irregularities of the recording medium 2 for fixing, and the irregularities on the surface of the image are smoothed to obtain gloss on the surface of the image. . In addition, the image can be prevented from being destroyed at the time of fixing, and the physical strength of the image can be increased by the effect of increasing the temperature of the image.

  The inline sensor 66 has a final state such as a pattern check, a moisture amount check, a surface temperature check, a glossiness check, etc., in an image formed on the recording medium 2 after the fixing process is performed in the fixing unit 50. Detection is performed. For example, a CCD line sensor can be used as the inline sensor 66.

  A paper discharge unit 60 is disposed downstream of the fixing unit 50 in the conveyance direction of the recording medium 2. The paper discharge unit 60 includes a discharge tray 61. Between the discharge tray 61 and the fixing drum 51 of the fixing unit 50, a transfer drum 63 disposed in contact with the fixing drum 51, a transport belt 65 that moves as the transfer drum 63 rotates, and a transfer drum And a tension roller 64 that applies tension to the transport belt 65. These construct a paper discharge transport mechanism. In this paper discharge transport mechanism, the recording medium 2 is transported from the transfer drum 63 to the transport belt 65, and the transported recording medium 2 is discharged to the discharge tray 61.

  The discharge tray 61 is provided with a cold air jet nozzle 62. The cold air ejection nozzle 62 ejects cold air to the discharged recording medium 2 and cools the recording medium 2 to adjust the temperature and humidity (seasoning).

  The image forming apparatus 1 shown in FIG. 1 includes a recording agent storage tank (ink storage tank), a processing liquid supply mechanism, a cleaning mechanism, various sensors, and the like, although not shown. The recording agent storage tank has a function of storing and storing the recording agents of the respective colors supplied to the recording heads 32K, 32Y, 32M, and 32C of the image forming unit 32. The processing liquid supply mechanism has a function of supplying the processing liquid to the processing liquid application unit 20. The cleaning mechanism has a function of cleaning and adjusting each of the recording heads 32K, 32Y, and 32M. The various sensors include a position sensor that detects the transport position of the recording medium 2 in the transport path of the recording medium 2, a temperature sensor that detects the temperature during each process, and the like.

  In the image forming apparatus 1, the conveyance path of the recording medium 2 from the paper feed tray 11 of the paper feeding unit 10 to the paper discharge unit 60, the processing liquid drum 22 that conveys the recording medium 2 in the conveyance path, and the drawing drum 31, the drying drum 41, the fixing drum 51, and the like constitute a conveying means.

  Further, the image forming apparatus 1 may include a plurality of seasoning devices having the same function as the cold air jet nozzle 62 disposed in the paper discharge unit 60. Further, the seasoning device may have a structure that can move between the paper discharge unit 60 and the paper supply unit 10.

<Configuration of Fixing Unit and Press Release Unit>
In the fixing unit 50 of the image forming apparatus 1 according to the first embodiment, as illustrated in FIGS. 2 to 4, the fixing drum (conveying member) 51 is an impression cylinder having a hollow cylindrical structure, and an outer peripheral surface having a curved surface. Is used as the transfer surface. The recording medium 2 on which an image is formed is held on the conveyance surface, and the recording medium 2 moves from the upstream side in the conveyance direction (drying unit 40 side) to the downstream side (the paper discharge unit 60 side) as the fixing drum 51 rotates. It is conveyed toward.

  The conveyance roller (pressing member) 52 is a roller having an outer diameter (diameter) dimension smaller than the outer diameter (diameter) dimension of the fixing drum 51 and having a hollow cylindrical structure. An outer peripheral surface having a curved surface of the conveying roller 52 is used as a pressing surface, and the pressing surface presses and holds the recording medium 2 conveyed to the conveying surface. The axial direction of the conveying roller 52 is set in parallel with the axial direction of the fixing drum 51, and the conveying roller 52 is disposed across both sides of the fixing drum 51. That is, the dimension in the width direction of the pressing surface of the conveyance roller 52 is set to be equal to the dimension in the width direction of the conveyance surface of the fixing drum 51.

  The pressing release unit has a function of repeating the operation of moving the conveyance roller 52 away from the conveyance surface and approaching the conveyance surface with respect to the recording medium 2 conveyed by the fixing drum 51. As shown in FIGS. 2 to 5, the pressure release means is disposed at a predetermined interval on the side of the conveyance surface of the fixing drum 51 (both sides in the first embodiment), and as the conveyance surface moves in the conveyance direction. A guide member 511 having a convex portion (cam-shaped portion) 511C on which the end of the conveying roller 52 rides is provided.

  The guide member 511 is a plate-like member that is disposed on the side of the fixing drum 51 and extends along at least a part of the conveyance surface. Since the conveyance surface of the fixing drum 51 has a curved surface, as shown in FIG. 5, the shape of the portion (guide surface) that contacts the conveyance roller 52 side of the guide member 511 is a convex portion 511C. It is comprised by the shape which added. The press releasing unit according to the first embodiment conveys the recording medium 2 on which an image is formed while pressing and holding the recording medium 2 on the conveying surface using the conveying roller 52, and the distortion of the recording medium 2 partially generated by the formation of the image. Is released repeatedly before drowning or drowning occurs. Fine adjustment is necessary in accordance with the thickness of the recording medium 2 to be conveyed. Here, the distance at which the conveying roller 52 is separated from the conveying surface is 2 mm in order to suppress the floating of the recording medium 2 from the conveying surface. It is set as follows.

  As shown in FIG. 3 in particular, the guide member 511 is provided with a fastening slot 512 that extends in the conveyance direction of the recording medium 2. The guide member 511 is mechanically fixed by attaching the fastening member 513 to the side portion of the fixing drum 51 through the fastening long hole 512. For example, a screw, a screw or the like is used as the fastening member. The fastening long holes 512 are disposed at two locations (three or more locations) in order to attach the guide member 511 to the fixing drum 51 without slight movement.

  Further, since the fastening elongated hole 512 is used to attach the guide member 511 to the fixing drum 51, the length of the fastening elongated hole 512 is the position of the convex portion 511C in the conveying direction with respect to the conveying surface. Adjustments can be made. In the image forming apparatus 1 according to the first embodiment, since the fixing drum 51 is provided with the claw 53 of the holding unit every 180 degrees, two sheets are shifted by 180 degrees on one side of the fixing drum 51. The guide member 511 is disposed. Accordingly, a total of four guide members 511 are disposed on both sides of the fixing drum 51. The number of guide members 511 is not limited to this number, and one or three or more guide members may be provided on one side.

  The guide member 511 is made of, for example, a material such as a metal or a resin that has moderately high mechanical rigidity, excellent wear resistance, and is suitable for machining.

  As shown in FIG. 5, the shape of the convex portion 511 </ b> C of the guide member 511 between at least the position where the conveying roller 52 is closest to the conveying surface and the position immediately before the position approaches the closest position from immediately before, The curved surface shape is such that the proximity speed of the conveyance roller 52 is slower than the conveyance speed of the conveyance surface. The curved surface shape only needs to be formed immediately after the position where the transport roller 52 is farthest from the closest position. Since the approach speed decreases as the transport roller 52 approaches the transport surface, the impact of the transport roller 52 on the recording medium 2 transported to the transport surface can be reduced. Therefore, even if the conveyance roller repeatedly approaches and presses the recording medium 2, the recording medium 2 is not damaged.

  The pressing release means is further connected to the end portions (here, both end portions) of the transport roller 52, rides on the convex portion 511C of the guide member 511, and has the same outer diameter as the outer diameter of the transport roller 52. It has. The guide roller 522 rotates along the convex portion 511 </ b> C when riding on the convex portion 511 </ b> C, and this rotational force is transmitted to the conveying roller 52. The transport roller 52 is rotated by the rotational force transmitted from the guide roller 522 even when being separated from the transport surface. That is, there is no relative speed difference between the conveyance speed (rotational speed) of the conveyance roller 52 and the conveyance speed of the recording medium 2, so that the recording medium 2 can be smoothly conveyed.

  The pressing release means further includes a biasing member 524. One end of the urging member 524 is attached to the rotation shaft 521 of the conveying roller 52 with a connecting member 522 interposed, and the other end is attached to a housing (not shown) of the image forming apparatus 1 via a base base 525. For example, a coil spring is used as the urging member 524, and this urging member 524 has a function of constantly urging (pressing) the pressing surface of the conveying roller 52 to the conveying surface via the connecting member 522.

<Operation of Fixing Unit and Press Release Unit>
The operation of the pressing release means according to the first embodiment shown in FIGS. 2 to 5 is as follows. First, the recording medium 2 on which an image is formed on the conveyance surface of the fixing drum 51 is held and conveyed in the fixing unit 50. The leading end of the recording medium 2 in the transport direction is held by the claw 53 of the holding means (see FIG. 6), and when the recording medium 2 is transported, the recording roller 2 starts to be pressed between the recording medium 2 and the transport surface. .

  Here, the form of wrinkles and wrinkles that occur on the recording medium 2 differs depending on the direction of fiber flow relative to the conveyance direction of the recording medium 2 and the type of image (pattern of the image forming area). In the first embodiment, when a normal sheet is used for the recording medium 2, the sheet in which the pulp fibers have a vertical flow with the long side in the vertical direction belongs to the T-th (longitudinal) sheet type. Further, a sheet in which the pulp fibers flow horizontally with the long side in the vertical direction belongs to the Y-type (landscape) sheet type.

  The recording medium 2 shown in FIG. 6A belongs to the Tth paper type, and is conveyed from the bottom to the top in FIG. This recording medium 2 has a flow of pulp fibers in a direction intersecting with the conveyance direction, and an area 2b where no image is formed in the center of the recording surface in a direction that coincides widely with the conveyance direction, and both sides of the recording surface And a region 2a where an image is formed in a direction that is wider than the set width and coincides with the conveying direction. Here, the region 2a where the image is formed is a solid region to which ink is attached as a recording agent. The set width is a threshold value calculated by experiments, simulations, and the like, and its value varies depending on the type of paper, for example, thickness, paper quality, etc., but is set to 80 mm here. The area 2b where no image is formed is an area as it is with the material of the paper without ink adhesion. The recording medium 2 is greatly stretched in the direction coinciding with the transport direction as indicated by arrows in FIG.

  The recording medium 2 on which such an image is formed gradually increases in distortion from the front stage side to the rear stage side in the transport direction, and the distortion generated on the rear stage side is larger than the distortion generated on the front stage side. When the fixing drum 51 is rotated, the pressing release means moves (rotates) the guide member 511 in the transport direction following the fixing surface, and moves away from the transport surface of the transport roller 52 according to the shape of the convex portion 511C. Proximity to the transfer surface is performed. The increasing distortion on the rear stage side of the recording medium 2 is instantaneously released by the separating operation of the conveying roller 51 before the wrinkles or the wrinkles occur. In FIG. 6A, the symbol X indicates the level (pressing level) at which the conveying roller 52 is close to the conveying surface, and the symbol Y indicates the level at which the conveying roller 52 is separated from the conveying surface (distortion release level). Here, the upstream side in the transport direction of the recording medium 2 is an area upstream from the center in the transport direction of the recording medium 2. Further, the downstream side in the conveyance direction of the recording medium 2 is an area downstream from the center in the conveyance direction of the recording medium 2.

  Further, the recording medium 2 shown in FIG. 6B belongs to the Y-th paper type, and is transported from the bottom to the top in FIG. This recording medium 2 has a flow of pulp fibers in a direction coinciding with the conveyance direction, and a region 2b where no image is formed in the center of the recording surface and in a direction intersecting the conveyance direction widely, and conveyance of the recording surface A region 2a in which an image is formed in a direction that coincides with the conveying direction is wider than the set width in each of a front stage and a rear stage that coincide with the direction.

  In the recording medium 2 on which such an image is formed, the elongation of the region 2a where the image is formed becomes larger as indicated by the arrow in the drawing with respect to the region 2b where the image is not formed. In particular, since the leading end of the recording medium 2 in the transport direction is held by the claw 53, distortion increases in the preceding stage in the transport direction. When the fixing drum 51 is rotated, the pressing release means moves (rotates) the guide member 511 in the transport direction following the fixing surface, and moves away from the transport surface of the transport roller 52 according to the shape of the convex portion 511C. Proximity to the transfer surface is performed. The increasing distortion on the front side of the recording medium 2 is instantaneously released by the separating operation of the conveying roller 51 before the wrinkle or the wrinkle occurs.

  The timing of the start and end of the approaching operation and the separating operation of the transport roller 52 to the transport surface is changed by changing the mounting position of the guide member 511 in the transport direction, or exchanged with another guide member 511 having a different arrangement position of the convex portion 511C. Make adjustments.

  Further, the recording medium 2 shown in FIG. 6C belongs to the T-th paper type, and is conveyed from the bottom to the top in FIG. This recording medium 2 has a flow of pulp fibers in a direction crossing the conveyance direction, and a region 2a in which an image is formed on the recording surface in a direction that is narrower and coincides with the conveyance direction in a category that does not satisfy the set value. And a region 2b in which no image is formed across the recording surface in the conveyance direction. The area 2a where the image is formed and the area 2b where the image is not formed are repeatedly arranged in a direction intersecting the transport direction.

  In the recording medium 2 on which such an image is formed, the direction in which the area 2a where the image is formed coincides with the conveyance direction as indicated by an arrow in the figure with respect to the area 2b where the image is not formed. And the distortion increases in the entire conveyance direction (all stages). When the fixing drum 51 is rotated, the pressing release means moves (rotates) the guide member 511 in the transport direction following the fixing surface, and moves away from the transport surface of the transport roller 52 according to the shape of the convex portion 511C. Proximity to the transfer surface is performed. In the entire recording medium 2, the increasing distortion is instantaneously released by the separating operation of the conveying roller 51 before wrinkles or wrinkles occur.

  Further, the press release means adjusts (controls) the operation according to the thickness type of the recording medium 2 in addition to or independently of the paper type and image type of the recording medium 2. May be. When the thickness of the recording medium 2 is equal to or larger than the set thickness, the recording medium 2 is strong (physical strength against bending and bending) is high, and even if the recording medium 2 is pressed by the conveying roller 52, it is difficult to buckle. It is hard for wrinkles to occur. When the thickness of the recording medium 2 is less than the set thickness, the recording medium 2 is weak (physical strength is low), and when the recording medium 2 is pressed by the transport roller 52, it is likely to buckle and wrinkle easily. The set thickness is threshold information set in advance, and is set to, for example, 157 gsm in the case of plain paper.

  When the thickness of the recording medium 2 is equal to or greater than the set thickness, the pressing release unit does not separate the transport roller 52 from the transport surface and does not perform an approach operation to the transport surface. When the thickness of the recording medium 2 is less than the set thickness, the pressing release unit performs the separation operation of the conveyance roller 52 from the conveyance surface and the proximity operation to the conveyance surface.

  In the fixing unit 50, the recording medium 2 that has been subjected to the fixing process without causing wrinkles or wrinkles by the pressing release unit is conveyed to the paper discharge unit 60.

<Characteristics of Example 1>
The image forming apparatus 1 according to the first embodiment configured as described above includes a pressing release unit in the fixing unit 50. The recording medium 2 partially expands as the image is formed. If the recording medium 2 is continuously pressed by the conveying roller (pressing member) 52, wrinkles and wrinkles occur. Since the conveyance roller 52 is repeatedly separated from the conveyance surface by the pressing release means, the distortion that causes the wrinkles and the wrinkles can be released before the wrinkles and the wrinkles are generated. On the other hand, the pressing release means repeatedly brings the conveying roller 52 close and can press and hold the recording medium 2 on the conveying surface by the conveying roller 52, so that the recording medium 2 can be stably held and conveyed on the conveying surface. . A fan, which will not be described, is provided inside the image forming apparatus 1, and an airflow is generated inside the fan when the fan is driven. When the recording medium 2 is lifted from the conveyance surface of the fixing drum 41, an air current flows into a gap generated by the float between the conveyance surface and the recording medium 2, and the recording medium 2 is disturbed by the air current. In order to prevent such a phenomenon, the pressing release means repeatedly presses down the recording medium 2 even after the distortion is repeatedly released by the conveying roller 52. Therefore, the recording medium 2 is prevented from being violated, and the recording medium is deformed or bent. Damage can be prevented. Further, as a result of preventing the recording medium 2 from being damaged, it is possible to prevent a reading failure of a position sensor (in this case, the inline sensor 66) that reads the conveying position of the recording medium 2, and to prevent a conveyance failure, a pattern check failure, etc. Problems can be prevented.

  Further, in the image forming apparatus 1, the pressing release unit includes a guide member 511 having a convex portion 511 </ b> C. Since the approaching operation and the separating operation of the transport roller 52 can be repeatedly performed using the convex portion 511C of the guide member 511, the structure of the pressing release unit can be easily realized.

  In the image forming apparatus 1, the pressing release unit includes a guide roller 522 at the end of the transport roller. The guide roller 522 rotates along the convex portion 511 </ b> C when riding on the convex portion 511 </ b> C, and this rotational force is transmitted to the conveying roller 52. Even when the transport roller 52 is separated from the transport surface, the transport roller 52 is rotated by the rotational force transmitted from the guide roller 522, so that there is no relative speed difference between the transport speed of the transport roller 52 and the transport speed of the recording medium 2. Therefore, the recording medium 2 can be transported smoothly.

  Further, in the image forming apparatus 1, the pressing release unit has a curved surface shape on the convex portion 511 </ b> C of the guide member 511. Since the approach speed decreases as the transport roller 52 approaches the transport surface, the impact of the transport roller 52 on the recording medium 2 transported to the transport surface can be reduced. Therefore, even if the conveyance roller 52 repeatedly approaches and presses the recording medium 2, it is possible to prevent the recording medium 2 from being damaged.

  In the image forming apparatus 1, the pressing release unit includes a biasing member 524 that biases the transport roller 52 toward the transport surface. Since the conveyance roller 52 presses the recording medium 2 against the conveyance surface, the recording medium 2 can be conveyed faithfully with respect to the movement of the conveyance surface in the conveyance direction. On the other hand, the conveyance roller 52 is pressed against the convex portion 511C of the guide member 511 by the urging member 524, and the conveyance roller 52 can be moved faithfully to the shape of the convex portion 511C.

  Further, in the image forming apparatus 1, the pressing release unit has a fastening elongated hole 512 in the guide member 511 and is detachably attached to the side wall of the fixing drum 51 through the fastening elongated hole 512 by the fastening member. The guide member 511 can be appropriately moved in the transport direction along the fastening elongated hole 512. Therefore, according to the image formed on the recording medium 2, it is possible to adjust the operation timing at which the conveying roller 52 is separated and approached, and the distortion of the recording medium 2 generated according to the image can be released as appropriate.

  Further, in the image forming apparatus 1, the press releasing unit can adjust the approaching operation and the separating operation of the transport roller 52 according to the thickness type of the recording medium 2.

  Further, in the image forming apparatus 1, the press releasing unit can adjust the approaching operation and the separating operation of the transport roller 52 according to the paper type and the image type of the recording medium 2.

(Example 2)
The second embodiment of the present invention describes a modification of the pressing release unit of the image forming apparatus 1 according to the first embodiment.

<Overall configuration of image forming apparatus>
As shown in FIG. 7, the pressure release unit of the image forming apparatus 1 according to the second embodiment is connected to a conveyance roller (pressing member) 52, and an actuator 526 that moves the conveyance roller 52 away from and close to the conveyance surface, and an actuator 526. And a controller (controller) 100 that repeatedly controls the operation of separating and the operation of bringing them close to each other.

  For the actuator 526, for example, a small, light and inexpensive electromagnetic solenoid is used. The actuator 526 is connected to a connecting member 523 interposed between the transport roller 52 and the biasing member 524. The control unit 100 does not need to be provided with a dedicated control unit, and also serves as a system controller (not shown) that controls the entire system of the image forming apparatus 1. The operation program of the actuator 526 is stored in a memory connected to the system controller through a common bus, and the operation of the actuator 526 is controlled using the stored program.

  In the pressing release unit of the image forming apparatus 1 according to the second embodiment, according to the paper type and the image type of the recording medium 2 described with reference to FIGS. 6A to 6C described above, or It is easy to control the operation of the actuator 526 according to the thickness of the recording medium 2. This control is executed using the control unit 100 as follows.

(1) When the recording medium 2 has a fiber flow in a direction intersecting the transport direction and an image having a width equal to or larger than the set width is formed in a direction that coincides with the transport direction (see FIG. 6A), the control unit 100 Stops the operation of the actuator 526 at the front stage in the transport direction, and executes the operation of the actuator 526 at the rear stage in the transport direction.

(2) When the recording medium 2 has a fiber flow in a direction coinciding with the transport direction and an image having a width equal to or larger than the set width is formed in a direction intersecting the transport direction (see FIG. 6B), the control unit 100 Performs the operation of the actuator 526 at the front stage in the transport direction, and stops the operation of the actuator 526 at the rear stage in the transport direction.

(3) When the recording medium 2 has a fiber flow in a direction crossing the transport direction and an image having a width less than the set width is formed in a direction coinciding with the transport direction (see FIG. 6C), the control unit 100 Performs the operation of the actuator 526 in all stages in the transport direction.

  The control unit 100 stops the operation of the actuator 526 when the thickness of the recording medium 2 is equal to or greater than the set thickness, and executes the operation of the actuator 526 when the thickness of the recording medium 2 is less than the set thickness.

  The control unit 100 is connected to the operation unit 101. The operation unit 101 is an operation unit that operates the image forming apparatus 1, and sets whether to drive the actuator 526 by an operation from the operation unit 101, whether the drive is manual, or whether the drive is automatic. Can do.

  In the press release unit according to the second embodiment, the actuator 526 is used to perform the operation of approaching the transport roller 52 to the transport surface and the separation operation from the transport surface, and is similar to the operation of the press release unit according to the first embodiment described above. Therefore, detailed description is omitted.

<Features of Example 2>
The image forming apparatus 1 according to the second embodiment includes an actuator 526 and a control unit 100 to construct a press release unit. A pressing release unit can be realized by a simple configuration of the actuator 526 and the existing control unit 100.

  In the image forming apparatus 1, the press release unit controls the operation of the actuator 526 in accordance with the type of the recording medium 2 and the type of image formed on the recording medium 2 using the control unit 100. The control unit 100 can freely control the actuator 526 based on various programs. Depending on the type of recording medium 2 and the type of image, the form of wrinkles and wrinkles that occur in the recording medium 2 differs. Since the conveyance roller 52 can be separated from the conveyance surface and brought close to the conveyance surface in accordance with the form of the wrinkle or curling, the recording medium 2 can be curled or curled while the recording medium 2 is securely held and conveyed. Can be prevented.

(Example 3)
The third embodiment of the present invention describes a modification of the pressing release unit of the image forming apparatus 1 according to the first embodiment.

<Overall configuration of image forming apparatus>
As shown in FIGS. 8 to 10, the pressure release unit of the image forming apparatus 1 according to the third embodiment is disposed on the conveyance roller 52 and is depressed toward the axial center side of the pressure surface of the conveyance roller 52. A groove 52T is provided.

  The press release groove 52 </ b> T extends across both sides of the transport roller 52. The pressing release grooves 52T according to the third embodiment are arranged in parallel every 90 degrees, and four are arranged on the pressing surface. The number of arrangement of the press release grooves 52T is not limited. In addition, the conveying roller 52 in which the number of pressing release grooves 52T is one, two, three, five, or more is prepared in advance, and is changed as appropriate according to the type of the recording medium 2 and the type of image. You may do it.

  In Example 3, the outer diameter (diameter) of the conveyance roller 52 is set to, for example, 30 mm-80 mm. At this time, the groove width of the press release groove 52T is 5 mm in consideration of the release of distortion and the maintenance of an appropriate pressure. Set to -30 mm.

  In the pressing release means according to the third embodiment, the pressing release groove 52T is used to perform the operation of moving the conveying roller 52 close to the conveying surface and the separating operation from the conveying surface, and the operation of the pressing releasing means according to the first embodiment described above. Since it is the same, detailed description is abbreviate | omitted.

<Features of Example 3>
In the image forming apparatus 1 according to the third embodiment, the pressing release unit is configured by a pressing release groove 52 </ b> T provided in the conveyance roller 52. Accordingly, the pressing release means can be realized with a simple configuration.

  Further, since the groove width of the pressing release groove 52T is set to 5 mm to 30 mm, it is possible to prevent the recording medium 2 from being wrinkled or twisted while reliably holding and transporting the recording medium 2.

<Other examples>
The present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the present invention. For example, in an ink jet image forming apparatus, the ink supply method for supplying ink directly from an ink storage tank to the print head 32K or the like, the ink circulation method for supplying ink to the print head 32K or the like while circulating the ink, etc. The invention can be applied.

  Further, the present invention is not limited to the fixing drum and its conveyance surface as the conveyance member and its conveyance surface. For example, when a belt conveyance mechanism is employed, the conveyance member is a belt, and the conveyance surface is a belt surface. Similarly, the pressing member is not limited to the conveying roller, and a belt may be employed. Further, the present invention can be applied to an offset printing machine as an image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Recording medium 10 Paper supply part 20 Processing liquid provision part 30 Drawing part 40 Drying part 50 Fixing part 51 Fixing drum (conveyance member)
52 Conveying roller (pressing member)
511 Guide member 511C Convex portion 512 Fastening hole 513 Fastening member 52 Guide roller 523 Connecting member 524 Energizing member 60 Paper discharge portions 70, 72, 74 Intermediate transport portions 71, 73, 75 Transfer cylinder 100 Control portion 101 Operation portion

Claims (11)

A conveying member that holds and conveys a recording medium having an image formed on the conveying surface;
A pressing member disposed to face the conveying surface;
Press release means for repeating the operation of separating the pressing member from the conveying surface and bringing it close to the conveying surface with respect to the recording medium conveyed by the conveying member;
An image forming apparatus comprising: The pressing member is a conveyance roller disposed across both sides of the conveyance surface,
The pressing release means includes a guide member disposed on a side portion of the transport surface at a predetermined interval, and having a convex portion on which an end of the pressing member rides as the transport surface moves in the transport direction. The image forming apparatus according to claim 1, wherein:   The image forming apparatus according to claim 2, wherein a guide roller that rides on the convex portion and has the same outer diameter as the outer diameter of the conveying roller is disposed at an end portion of the conveying roller. apparatus.   As the shape of the convex portion between at least the position where the conveying roller is closest to the conveying surface and the position immediately before it approaches the position closest to the immediately preceding position, with respect to the conveying speed of the conveying surface The image forming apparatus according to claim 2, wherein the image forming apparatus has a curved shape in which a proximity speed of the conveying roller is slow.   The image forming apparatus according to claim 1, wherein the pressing release unit includes a biasing member that biases the pressing member toward the conveyance surface. The conveying member is an impression cylinder that conveys the recording medium while rotating;
3. The guide member according to claim 2, wherein the guide member has a fastening elongated hole extending in the conveying direction, and is detachably attached to the side wall of the impression cylinder through the fastening elongated hole by the fastening member. Item 5. The image forming apparatus according to any one of Items 4 to 5. The pressing release means is
An actuator connected to the pressing member to move the pressing member away from and close to the conveying surface;
A controller that repeatedly controls the movement of the actuator and the movement of the actuator; and
The image forming apparatus according to claim 1, further comprising:   The control unit stops the operation of the actuator when the thickness of the recording medium is equal to or greater than a set thickness, and executes the operation of the actuator when the thickness of the recording medium is less than the set thickness. The image forming apparatus according to claim 7, wherein the operation of the actuator is controlled according to a type of thickness of the medium.   The image forming apparatus according to claim 7, wherein the control unit controls the operation of the actuator according to a type of image on the recording medium. The pressing member is a conveyance roller disposed across both sides of the conveyance surface,
2. The image forming apparatus according to claim 1, wherein the pressing release unit includes a pressing release groove disposed on the transport roller and recessed toward the axial center of the pressing surface of the transport roller.   11. The image forming unit according to claim 1, further comprising an image forming unit that discharges ink onto the recording medium to form an image on the upstream side of the transport unit with respect to the transport member and the pressing member in the transport direction. The image forming apparatus according to claim 1.