JP2012123107A - Image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce, in a fixing device, damage of a heating member surface caused by a separation plate that is disposed close to the heating member for separating a recording material from the heating member, and is brought into contact with the heating member by a pushing pressure or the like of the recording material.SOLUTION: The image heating device is configured to, while rotatably supporting the separation plate, dispose a rotation center of the rotation at an area between; a face which is a perpendicular face of a recording material guide face of the separation plate from the separation plate tip end and is a surface extending in the opposite direction of the guide surface; and a surface including a fixing member rotation center from the separation plate tip end.

Description

  The present invention relates to an image heating apparatus that is used in an image forming apparatus using toner such as a multifunction machine, a copying machine, a printer, and a fax machine, and more particularly to an image heating apparatus that heats a toner image formed on a recording material.

  In an image heating apparatus that heats an image on a recording material in an image forming apparatus based on electrophotographic technology, the toner image is transferred by a transfer unit, and the toner image is heated by heating and pressurizing the conveyed recording material. . A fixing device as an image heating device includes a fixing member as an image heating member and a pressure member that forms a nip portion that presses the fixing member to sandwich and convey the recording material. Then, the toner image on the recording material is fixed to the recording material at the nip portion. That is, the toner formed on the recording material is melted by heat applied from the fixing member. At this time, the melted toner has adhesiveness, and the separability of the recording material with respect to the fixing member is lowered. Therefore, as one of the technical problems of the fixing device, there is a case where the recording material on which the toner image is fixed at the nip portion is wound around the heating member after passing through the nip.

  As a configuration for reducing the damage to the fixing member while reducing the damage to the fixing member, a separation plate arranged in a non-contact manner with the fixing member can be cited. The non-contact separation plate needs to assist the separation of the recording material without contacting the heating member, and it is necessary to improve the accuracy of the distance between the separation plate tip position and the fixing member.

  In order to improve the accuracy of the tip position of the separation plate, positioning is performed with reference to the rotation center of the fixing member (Patent Document 1), and only the non-sheet passing portion abuts the separation plate against the surface of the fixing member. A device for positioning with respect to a fixing member is known (Patent Document 2).

JP 2006-259718 A JP 2008-197237 A

  However, when a force is applied to the tip of the separation plate, if the tip of the separation plate moves in a direction in contact with the fixing member, the tip of the separation plate comes into contact with the fixing member, and the surface of the fixing member is damaged. There is.

  Accordingly, the present invention reduces the contact between the separation plate and the image heating member due to the pressing of the leading end of the separation plate while the separation plate for separating the recording material from the image heating member is disposed in proximity to the image heating member. For the purpose.

  Accordingly, the present invention provides an image heating member that heats an image of a recording material, a pressure member that presses the image heating member and forms a nip portion that sandwiches and conveys the recording material, and a non-contact arrangement with the image heating member. A separating plate for separating the recording material that has passed through the nip portion from the image heating member, a supporting means having a support shaft disposed on the image heating member side, and rotatably supporting the separating plate; And a positioning unit that positions the separation plate at a position for separating the separation plate from the heating member. When the separation plate is positioned by the positioning unit, the support shaft is positioned on the image heating member side of the separation plate. It is characterized in that it is arranged between a vertical plane with respect to the separation plate passing through the tip and a surface including the tip of the separation plate and the rotation center line of the image heating member.

  According to the present invention, the separation plate for separating the recording material from the image heating member can be disposed close to the heating member, and it is possible to reduce the contact of the separation plate with the heating member due to the pressing of the leading end of the separation plate.

Sectional view showing the fixing device in the embodiment The front view which shows the fixing device in an Example Detailed view around the separator in the example Sectional drawing which shows the image forming apparatus in an Example Schematic diagram around the separator in the example

(Example)
First, the overall configuration of an image forming apparatus employing an electrophotographic system will be described with reference to FIG.

  The image forming apparatus 100 roughly includes an image forming unit that forms a toner image on a recording material, and a fixing device (image heating device) that fixes the toner image formed on the recording material by heating and pressing.

  In this embodiment, the image forming unit has a photosensitive drum 102 as an image carrier. When the image forming signal is input, the photosensitive drum 102 starts to rotate. A charger 103 for charging the photosensitive drum 102 is provided, and the surface of the photosensitive drum 102 is uniformly charged by the charger 103. An electrostatic latent image is formed on the photosensitive drum 102 by irradiating an image exposure 105 corresponding to the image from an exposure device 104 serving as an exposure unit. The electrostatic latent image is developed by a developing device 106 as a developing unit, and a toner image is formed on the photosensitive drum 102. On the other hand, the recording material S is stored in a feeding cassette 109 below the image forming apparatus and is fed by a feeding roller 110. The recording material is conveyed in synchronism with the toner image on the photosensitive drum 102 by a registration roller pair 111 as conveying means. The toner image on the photosensitive drum is electrostatically transferred onto a recording material by a transfer roller 107 as a transfer unit, and is conveyed to a fixing device 114. Thereafter, the toner remaining on the photosensitive drum 102 is removed by a cleaning device 108 as a cleaning unit.

  The toner image formed on the recording material S by the image forming unit is fixed on the recording material by being heated and pressed in the nip portion of the fixing device 114. The recording material S that has passed through the nip portion is conveyed and discharged by a discharge roller pair 112 to a discharge tray 113 at the top of the apparatus.

Next, the fixing device 114 will be described with reference to FIGS. First, it demonstrates using FIG.
The pressure belt 120, which is a pressure member, is looped around two support members, that is, a pressure roll 121 and a tension roll 122 having a function of applying belt tension, and can be circulated and rotated with a predetermined tension (for example, 200 N). Has been passed.

  The heating belt 130, which is an image heating member, is looped around two support members, that is, a driving roll 131 and a tension roll 132 having a function of applying belt tension, and can be circulated and rotated with a predetermined tension (for example, 200 N). ing.

  Here, in the present embodiment, the pressure belt 120 has heat resistance. For example, a nickel metal layer having a thickness of 50 μm, a width of 380 mm, and a circumference of 200 mm is coated with, for example, a 300 μm-thick silicon rubber and a surface layer is coated with a PFA tube.

  The heating belt 130 has a metal layer (nickel metal layer) that generates heat due to the magnetic flux generated by the coil 135 and has heat resistance. For example, a magnetic metal layer such as a nickel metal layer or a stainless steel layer having a thickness of 75 μm, a width of 380 mm, and a circumference of 200 mm is coated with, for example, a 300 μm-thick silicon rubber, and a surface layer is coated with a PFA tube.

  On the inner side of the pressure belt 120 corresponding to the inlet side of the nip portion between the pressure belt 120 and the heating belt 130 (upstream side of the pressure roll 121), a pressure pad 125 made of, for example, silicon rubber has a predetermined pressure ( For example, it is pressed against the pressure belt 120 at 400 N). As a result, a nip portion is formed together with the pressure roll 121.

  The pressure roll 121 is a roll for suspending a pressure belt 120 having an outer diameter of φ20 made of solid stainless steel, for example, and is arranged on the outlet side of the nip portion that sandwiches and conveys the recording material by the pressure belt 120 and the heating belt 130. It is installed.

  Further, the tension roll 122 is a hollow roll formed of, for example, stainless steel with an outer diameter of about 20 mm and an inner diameter of about 18 and functions as a belt tension roll. Both ends of the tension roll 122 are supported by bearings 126, and a tension spring 127 applies a 20 kgf tension to the belt.

  A pad stay 137 made of stainless steel (SUS material), for example, is provided inside the heating belt 130 corresponding to the inlet side (upstream side of the drive roll 31) of the nip portion between the heating belt 130 and the pressure belt 120. It is pressed against the pressure pad 125 with a pressure (for example, 400 N) and forms a nip portion together with the drive roll 131.

  The drive roll 131 is a roll in which a heat-resistant silicone rubber elastic layer is integrally formed on a core metal surface layer having an outer diameter of φ18 made of solid stainless steel, for example. The drive roll 131 is disposed on the exit side of the nip portion between the heating belt 130 and the pressure belt 120, and the elastic layer is elastically distorted by a predetermined amount by the pressure contact of the pressure roll 121.

  Further, the tension roll 132 is a hollow roll formed of, for example, stainless steel with an outer diameter of about φ20 and an inner diameter of about 18 and functions as a belt tension roll. Both ends of the tension roll 132 are supported by bearings 133, and a tension spring 134 applies 20 kgf of tension to the belt.

  Drive is input to the drive roll 131 from the outside by a motor (not shown) here, and the heating belt 130 is conveyed by the rotation of the drive roll 131. In order to stably convey the recording material, the drive is reliably transmitted between the heating belt 130 and the drive roll 131.

  The heating belt 130 is heated by the induction heating coil 135, the surface temperature is detected by a desired temperature detection member, and the energization amount to the induction heating coil 135 is controlled by the control unit, whereby the set target temperature is 180. Temperature controlled to ° C.

  Next, the configuration of a separation plate which is an auxiliary means for separating the recording material of the fixing device will be described with reference to FIG. FIG. 3 is an enlarged view of the circular portion of FIG. The separation plate 141 is provided with a predetermined interval at the upstream end in the recording material conveyance direction so as not to contact the heating belt 130. Further, the separation plate 141 functions as a guide member that guides the recording material to the downstream fixing discharge roller pair 142 from one end on the upstream side to one end on the downstream side. In this embodiment, the gap A between the separation plate 141 and the heating belt 130 is 0.5 mm. The separation plate 141 is supported by a separation plate holder 143 as support means. The separation plate holder 143 is rotatably supported by a separation plate rotation center shaft 144 as a support shaft at the end of the heating belt 130 in the axial direction, and the tip of the separation plate is pressurized by a spring 145 in a direction approaching the heating belt 130. The separation plate rotation center shaft 144 is disposed on the image heating member side, that is, on the heating belt 130 side with respect to the recording material conveying portion (nip portion). A shaft 146 and a roller 147 that is rotatably supported by the shaft 146 are disposed at both ends of the separation plate holder. The roller 147 is contacted and pressed against the heating belt 130 by the spring force of the spring 145. That is, when the shaft 146 and the roller 147 as positioning members abut on the heating belt 130, the distance between the tip of the separation plate 141 and the heating belt 130 can be maintained.

  With the above configuration, the separation plate 141, the separation plate holder 143, the shaft 146, and the roller 147 can be integrally rotated about the separation plate rotation center shaft 144. The tip of the separation plate 141 on the heating belt 130 side can be positioned with high accuracy by following the change in position of the surface of the heating belt 130 due to the thickness of the heating belt 130 and thermal expansion including the drive roll 131. .

  Further, the center position of the separation plate rotation center shaft 144 will be described with reference to FIG. Separating the recording material conveying surface xxx surface B (FIG. 3) of the separation plate 141 from the heating belt 130 side tip, the vertical surface C (FIG. 3) of the separation plate 141, and the heating belt 130 side tip of the separation plate 141. The plate 141 is arranged in the region E (/// region, FIG. 3) of the region divided by the surface D (FIG. 3) including the rotation center line of the driving roll 131 opposed via the heating belt 130. . Here, the recording material conveyance surface of the separation plate 141 is a surface facing the recording material on which the separation plate 141 is conveyed.

  As a result, even when the recording material presses the tip of the separation plate, the separation plate 141 generates a force in the arrow Y direction (FIG. 3) toward the center of the separation plate rotation center axis 144. As a result, the tip of the separation plate 141 moves in the direction of the arrow Y, thereby preventing the separation plate 141 and the heating belt 130 from contacting each other.

  Here, the relationship between the separation plate rotation center axis and the C and D surfaces will be described with reference to FIG. FIG. 5 schematically shows the relationship between the position of the separation plate 141, the separation plate rotation center shaft 144, the heating belt 130 and the force applied to the separation plate 141, and the relationship between the surfaces C and D.

  FIG. 5A is a diagram showing a configuration in which the center point of the separation plate rotation central axis 144 is arranged downstream of the front end of the separation plate 141 with respect to the surface C in the recording material conveyance direction. In this case, when a pressure F is generated at the tip of the separation plate, the separation plate 141 receives a rotational force in the FA direction at the center of the separation plate rotation center shaft 144. In the configuration of FIG. 5A, the FA direction is the direction in which the tip of the separation plate 141 approaches the heating belt 130, and depending on the size of the press F, the tip of the separation plate 141 and the heating belt 130 may come into contact with each other. . Therefore, the arrangement of the separation plate rotation center axis as shown in FIG.

  FIG. 5B is a diagram illustrating a configuration in which the center point of the separation plate rotation center axis 144 is arranged on the recording material conveyance side with respect to the surface D. In this case, when a pressure F is generated at the tip of the separation plate, the separation plate 141 receives a rotational force in the FA direction about the separation plate rotation center axis 144. As a result, the tip of the separation plate 141 tends to rotate along the trajectory T. The trajectory T is a trajectory for lifting the separating plate 141 upward in FIG. 5B when a pressing F is generated against the positioned separating plate 141. As a result, there is a position that is smaller than the gap A between the front end of the separation plate 141 positioned by the positioning member and the heating belt 130. In order to prevent the contact at this time, the gap A needs to be set large in advance. As a result, the distance between the leading end of the separation plate 141 and the heating belt 130 is increased, and therefore, the separation of the recording material from the heating belt 130 cannot be sufficiently improved, which is not preferable.

  On the other hand, FIG. 5C is a diagram showing a configuration in which the center point of the separation plate rotation center axis 144 is arranged in a region between the surface C and the surface D. In this case, when a pressure F is generated at the tip of the separation plate, the separation plate 141 receives a rotational force in the FA direction at the center of the separation plate rotation center shaft 144. As a result, the tip of the separation plate 141 rotates along the locus T. However, the trajectory T is configured such that the front end of the separation plate 141 is retracted from the heating belt 130 in the direction in which the distance between the front end of the positioned separation plate 141 and the heating belt 130 is wider than the gap A. Therefore, the gap A can be set small.

  More specifically, when the center point of the separation plate rotation center axis 144 is on the C plane, when the pressing F is generated, no rotation force is generated on the separation plate, and therefore the tip of the separation plate 144 is positioned at the heating belt 130. Will approach. In order to generate the force FA for retracting the separation plate 141 toward the downstream side in the recording material conveyance direction, the center point of the separation plate rotation center axis 144 is on the D surface side (recording material conveyance direction). In this case, it is desirable to be disposed upstream of the separation plate 141.

  On the other hand, when the center point of the separation plate rotation center axis 144 is on the D plane, when a press F is generated, the press F is a linear direction connecting the tip of the separation plate and the center of the drive roller, and this linear direction. The pressure is divided in the orthogonal direction. Therefore, the tip of the separation plate starts to retract in the orthogonal direction when the press F occurs. At this time, when the center point of the separation plate rotation center shaft 144 overlaps the center point of the driving roller, the center of the locus of the separation plate tip is the same concentric circle as the center of the driving roller. The interval between and will not be reduced. However, when the center point of the separation plate rotation center shaft 144 is less than the distance between the separation plate tip and the center point of the drive roller, the curvature of the circular motion of the separation plate tip is increased, so that the separation is performed during retraction. There is a risk of contact between the plate tip and the heating belt. Therefore, it is desirable that the interval connecting the leading end of the separating plate and the center point of the separating plate rotation center shaft 144 is larger than the interval connecting the leading end of the separating plate and the center point of the drive roller. As described above, there is no problem even if the center point of the separation plate rotation center axis 144 is on the D plane.

  In the case of the arrangement of FIG. 5C, if the separation plate 141 rotates more than necessary along the trajectory T, the separation plate 141 will eventually come into contact with the heating belt 130. Therefore, in the present embodiment, as a restricting member for restricting rotational movement for retreating from the position of the positioned separation plate, a hole is provided in the separation plate holder 143 as shown in FIG. 148 was placed. As a result, the rotational movement range of the separation plate 141 is restricted, and the separation plate 141 does not rotate too much so that the tip of the separation plate 141 does not approach the heating belt 130.

  With the above configuration, when the separating plate 141 is brought close to the heating belt 130, the possibility that the leading end of the separating plate 141 contacts the image heating member due to the pressing from the recording material generated at the leading end of the separating plate 141 is reduced. It becomes possible to do.

  In addition, in the present Example, it demonstrated using the structure which stretches a belt member with a some stretching roller. As a result, the relationship between the tension roller (drive roller) facing the separation plate via the belt member and the tip of the separation plate has been described. In a configuration in which a heating roller is used in place of the belt member and the separation plate separates the recording material from the heating roller, the relationship between the leading edge of the separation plate and the rotation center of the heating roller is a tension member that faces the separation plate via the belt member. This corresponds to the relationship between the roller (drive roller) and the tip of the separation plate. In a configuration in which the recording material is separated from a rotatable cylindrical belt member that is not stretched by a plurality of stretching rollers, the relationship between the leading edge of the separation plate and the rotation center of the belt member is separated via the belt member. This corresponds to the relationship between the tension roller (drive roller) facing the plate and the tip of the separation plate.

  In the present embodiment, a single color image forming unit is used as the image forming unit. However, the present invention can also be applied as a fixing device that fixes an image formed by a color image forming unit on a recording material. Can do.

114 Fixing Device 120 Pressure Belt 130 Heating Belt 141 Separation Plate 143 Separation Plate Holder 144 Separation Plate Rotation Center Axis B Recording Material Guide Surface of Separation Plate C Recording Material Guide Surface of Separation Plate in a Vertical Area of Separation Plate Recording Material Guide Surface Region on the opposite side of the region DC Region outside the DC region upstream in the recording material conveyance direction

Claims (2)

An image heating member that heats the image of the recording material, a pressure member that presses the image heating member and forms a nip portion that sandwiches and conveys the recording material, and is disposed in non-contact with the image heating member and passes through the nip portion. A separating plate for separating the recorded material from the image heating member, a support shaft disposed on the image heating member side, and supporting means for rotatably supporting the separating plate, and a separating plate from the image heating member. In an image heating apparatus having a positioning unit positioned at a position for separation,
When the separation plate is positioned by the positioning portion, the support shaft has a vertical plane with respect to the separation plate passing through the tip of the separation plate on the image heating member side, the tip of the separation plate, and the rotation center line of the image heating member. An image heating apparatus, wherein the image heating apparatus is disposed between the containing surfaces.   The image heating apparatus according to claim 1, further comprising a regulating member that regulates a range in which the separation plate rotates.

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