JP6234878B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus.

  Japanese Patent Application Laid-Open No. 2004-228561 is a fixing device that includes a heating roller and a backup roller, and fixes the toner transferred onto the recording medium by pressurizing and heating, and includes a separation member that separates the recording medium from the fixing roller. What you have is shown. In this fixing device, the separating member is made of a thin rectangular metal plate.

JP 2007-183666 A

  However, in the technique described in Patent Document 1, condensation may occur on the separation member, and water droplets on the separation member may adhere and the recording medium may get wet.

  It is an object of the present invention to provide a fixing device and an image forming apparatus that can prevent a recording medium from getting wet due to condensation of a separating member.

The fixing device according to the present invention includes a rotating fixing member and a pressure member that forms a nip portion in contact with the fixing member, and conveys a recording medium on which a toner image is formed, sandwiched between the nip portion. The fixing unit that fixes the toner image to the recording medium by heating while heating, the plate-like separation member that separates the recording medium discharged from the nip part from the fixing member, and the separation member are held. A holding member and an abutting member attached to the separation member, the separation member being downstream of the nip portion in the conveyance direction of the recording medium and in the width direction of the fixing member perpendicular to the conveyance direction. And a separation guide portion that is arranged to face the fixing member and extends in a guide direction along the conveyance direction, and separates and guides the recording medium from the fixing member, and the separation guide portion Feeding extends from the downstream end of the direction, the a extending portion are bent with respect to the separation guide portion in a direction away from said recording medium toward the downstream side in the transport direction, the separating guide in the width direction provided on the outside of the section, it has a said mounted portion abutting member is attached, the abutting member is fixed between the fixing member and the separation guide portion by abutting on the fixing member A gap is formed .

The image forming apparatus according to the present invention, characterized in that the chromatic image forming unit for forming a toner image on a recording medium, and the fixing device for fixing on the recording medium the toner image formed on the recording medium And

  According to the present invention, it is possible to prevent the recording medium from getting wet due to condensation of the separation member.

1 is a schematic diagram illustrating a configuration of an image forming apparatus having a fixing device according to an embodiment. 1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment. 1 is a cross-sectional view illustrating a configuration of a fixing device according to an embodiment. It is sectional drawing of a separation unit and its periphery. It is sectional drawing of a separation unit. It is a perspective view of a separation unit. FIG. 4 is a diagram illustrating a state in which a sheet is conveyed in a fixing device. It is sectional drawing of a separation plate and a holding member. It is a perspective view of a separation plate and a holding member. It is a perspective view which shows the state before attachment of a contact member. It is a perspective view which shows the state after attachment of a contact member. (A) And (b) is the side view and sectional drawing of a guide roller, respectively. It is a figure which shows the modification of a guide roller.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Configuration of Image Forming Apparatus]
FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus 1 having a fixing device 500 according to the present embodiment. The image forming apparatus 1 is an apparatus that forms an image by fixing a toner image, which is a developer image formed on a recording medium, by a fixing device 500. Specifically, the image forming apparatus 1 is an electrophotographic printing apparatus, and here is a color printer.

  The image forming apparatus 1 includes a paper tray 100, a paper feeding unit 200, a paper transport unit 300, an image forming unit 400, and a fixing device 500.

  The paper tray 100 stores paper P as a recording medium in a stacked state. The paper tray 100 is configured to raise the paper P stored therein to a predetermined height.

  The paper feeding unit 200 is provided on the feeding side of the paper tray 100 and feeds the paper P stored in the paper tray 100 one by one. The paper feeding unit 200 includes a pickup roller 201, a feed roller 202, and a separation piece 203. The pickup roller 201 is provided so as to come into pressure contact with the paper P that has risen to a predetermined height, and feeds the paper P. The feed roller 202 and the separation piece 203 separate and feed the paper P fed by the pickup roller 201 one by one.

  The paper transport unit 300 transports the paper P that has been fed out by the paper feed unit 200 to the image forming unit 400. The paper transport unit 300 includes transport roller pairs 301 and 302 for transporting the fed paper P.

  The image forming unit 400 forms a toner image on the paper P transported from the paper transport unit 300. The image forming unit 400 includes four toner image forming units 410K, 410Y, 410M, and 410C, and a transfer unit 420. The toner image forming units 410K, 410Y, 410M, and 410C form black (K), yellow (Y), magenta (M), and cyan (C) toner images, respectively. The toner image forming units 410K, 410Y, 410M, and 410C are arranged in series along the direction in which the sheet is conveyed, and are provided detachably with respect to the apparatus main body 2. The transfer unit 420 transfers the color toner images formed by the toner image forming units 410K, 410Y, 410M, and 410C onto the paper P.

  The toner image forming unit 410K includes a photosensitive drum 411 as an image carrier that carries a toner image, a charging roller 412 as a charging device that charges the surface of the photosensitive drum 411, and an electrostatic surface on the surface of the charged photosensitive drum 411. An optical head 413 as a latent image forming apparatus or exposure apparatus that forms a latent image, and a developing roller 414 as a developing apparatus that forms a toner image on the photosensitive drum 411 by developing the electrostatic latent image with toner as a developer. And a cleaning blade 415 as a cleaning device for cleaning the surface of the photosensitive drum 411. The configuration of the toner image forming units 410Y, 410M, and 410C is the same as that of the toner image forming unit 410K except for the color of the toner to be used, and thus the description thereof is omitted.

  The transfer unit 420 includes a transfer belt 421, a drive roller 422, a tension roller 423, and four transfer rollers 424. The transfer belt 421 is an endless member that electrostatically attracts the paper P and transports it in the direction of the arrow A1 in the figure. The drive roller 422 drives the transfer belt 421, and the tension roller 423 stretches the transfer belt 421 together with the drive roller 422. The four transfer rollers 424 are arranged to face the four photosensitive drums 411 with the transfer belt 421 interposed therebetween, and respectively transfer the toner images on the corresponding photosensitive drums 411 to the upper surface of the paper P by Coulomb force. The transfer belt 421 sends out the paper P on which the toner image is transferred to the fixing device 500.

  The fixing device 500 fixes the toner image formed on the paper P by the image forming unit 400 to the paper P with heat and pressure. The fixing device 500 will be described in detail later.

  On the downstream side of the fixing device 500, a pair of discharge rollers 601 and 602 that convey the paper P sent out from the fixing device 500 and discharge it from the discharge port 603, and a stacking unit that stacks the paper P discharged from the discharge port 603 604 is provided. A reversing unit 700 is provided as a configuration for performing double-sided printing. The reversing unit 700 reverses the sheet P sent out from the fixing device 500 and conveys it to the sheet conveying unit 300. The reversing unit 700 includes transport roller pairs 701 to 704 that transport the paper P, and transport path switching guides 705 and 706 that switch the transport path of the paper P.

  As shown in FIG. 2, the image forming apparatus 1 further includes a control unit 801, a drive unit 802, and a power supply unit 803. The control unit 801 includes, for example, a central processing unit (CPU), and controls the operation of the image forming apparatus 1. The driving unit 802 includes, for example, a motor, and supplies driving force to each unit of the image forming apparatus 1 such as the fixing device 500 in accordance with an instruction from the control unit 801. The power supply unit 803 supplies power or voltage to each unit of the image forming apparatus 1 such as the fixing device 500 in accordance with an instruction from the control unit 801.

[Configuration of Fixing Device]
Hereinafter, the configuration of the fixing device 500 will be described.
FIG. 3 is a cross-sectional view showing the configuration of the fixing device 500 according to the present embodiment. In FIG. 3, the fixing device 500 includes a fixing unit 10, a separation unit 30, a conveyance roller pair 50, and paper guides 71, 72, and 73.

  The fixing unit 10 includes a fixing belt 11 as a rotating fixing member, and a pressure roller 16 as a pressure member that contacts the fixing belt 11 to form a nip portion (or contact portion) N1. The toner image is fixed on the paper P by heating the paper P on which the image is formed while being sandwiched between the nip portions N1. The fixing unit 10 is assembled to a fixing frame 21 fixed to the apparatus main body 2. Hereinafter, the direction in which the paper P is transported by the fixing unit 10 is referred to as “paper transport direction”.

  In FIG. 3, the fixing unit 10 includes a fixing belt 11, a fixing roller 12, a heating member 13, a belt guide 14, a fixing pad 15, and a pressure roller 16.

  The fixing belt 11 is an endless member that heats and melts the toner image on the paper P. The fixing belt 11 extends in the width direction perpendicular to the paper transport direction (direction perpendicular to the paper surface of FIG. 3). The width direction of the fixing belt 11 coincides with the width direction of the paper P orthogonal to the paper transport direction. Hereinafter, a direction parallel to the width direction of the fixing belt 11 is simply referred to as “width direction”. The surface of the fixing belt 11 is coated with fluorine. On the inner peripheral side of the fixing belt 11, a fixing roller 12, a heating member 13, a belt guide 14, and a fixing pad 15 are arranged in this order. The fixing roller 12, the heating member 13, the belt guide 14, and the fixing pad 15 all extend in the width direction.

  The fixing roller 12 is rotatably supported by the fixing frame 21 and is connected to the driving unit 802 via a gear (not shown). The fixing roller 12 rotates in a predetermined rotation direction (arrow A2 direction in FIG. 3) by a driving force from the drive unit 802, and rotates the fixing belt 11 in a predetermined rotation direction (arrow A3 direction in FIG. 3). The fixing roller 12 includes a metal pipe and a silicon sponge layer that is an elastic layer formed on the outer periphery of the metal pipe.

  The heating member 13 is a member that heats the fixing belt 11. Specifically, the heating member 13 includes a heater 13 a that is a heat source that generates heat when power is supplied from the power supply unit 803, and a heat transfer member 13 b that transmits heat of the heater 13 a to the fixing belt 11. The heating member 13 is pressed against the inner peripheral surface of the fixing belt 11 by a spring 22 that is an urging member. The spring 22 is disposed between the support member 23 fixed to the fixing frame 21 and the heating member 13.

  The belt guide 14 is fixed to the fixing frame 21 and contacts the inner peripheral surface of the fixing belt 11 to guide the movement of the fixing belt 11.

  The fixing pad 15 is supported by the fixing frame 21 and is urged toward the pressure roller 16 by a spring 24 that is an urging member. The spring 24 is disposed between the support member 23 and the fixing pad 15. The fixing pad 15 includes a rubber contact portion 15a that contacts the fixing belt 11, and a metal frame 15b that supports the contact portion 15a.

  The pressure roller 16 extends in the width direction and is disposed so as to face the fixing roller 12 and the fixing pad 15 with the fixing belt 11 interposed therebetween. The pressure roller 16 is pressed against the fixing roller 12 and the fixing pad 15 with the fixing belt 11 sandwiched between them by a spring (not shown), and forms a nip portion N1 between the pressure roller 16 and the fixing belt 11. The pressure roller 16 is rotatably supported by the fixing frame 21 and rotates in the direction of arrow A4 in FIG. 3 as the fixing roller 12 rotates. The pressure roller 16 includes a metal pipe and a silicon rubber layer that is an elastic layer formed on the outer periphery of the metal pipe.

  In addition, the fixing unit 10 includes a temperature detection member 25 that detects the temperature of the fixing belt 11, and an overheat prevention member 26 that prevents overheating of the fixing unit 10. The temperature detection member 25 is a thermistor, for example, and outputs a detection result to the control unit 801. The overheat prevention member 26 is, for example, a thermostat, and cuts off the power supply from the power supply unit 803 to the heater 13a when the temperature of the heat transfer member 13b reaches a predetermined temperature.

  The separation unit 30 is disposed on the downstream side of the fixing unit 10 in the sheet conveyance direction, and separates and guides the sheet P discharged from the nip portion N1 from the fixing belt 11. The separation unit 30 plays a role of preventing the paper P from being wound around the fixing belt 11.

  The conveyance roller pair 50 is disposed on the downstream side of the separation unit 30 in the sheet conveyance direction, and further conveys the sheet P that has passed through the separation unit 30. The conveyance roller pair 50 is a conveyance roller pair disposed first on the downstream side of the fixing unit 10 in the sheet conveyance direction, that is, a conveyance roller pair immediately after the fixing unit 10. The pair of conveyance rollers 50 includes two conveyance rollers 51 and 52 that are in contact with each other to form a nip portion (or contact portion) N2. The two conveying rollers 51 and 52 are rotated by the driving force from the driving unit 802 and convey the sheet P with the nip portion N2. From the viewpoint of suppressing the occurrence of wrinkles on the paper P, the transport speed VE of the paper P by the transport roller pair 50 is set to be higher than the transport speed VF of the paper P by the fixing unit 10, and VE> VF. Yes.

  The sheet guides 71 to 73 extend in the sheet conveyance direction, and guide the sheet P discharged from the fixing unit 10 toward the conveyance roller pair 50. The paper guides 71 to 73 have a plurality of ribs extending in the paper conveyance direction arranged in the width direction. The paper guides 71 to 73 are made of resin. The paper guide 71 is disposed to face the separation unit 30, the paper guide 72 is disposed adjacent to the paper guide 71 on the downstream side in the paper conveyance direction, and the paper guide 73 is paper to the separation unit 30. It is arranged adjacent to the downstream side in the transport direction.

  Between the separation unit 30 and the paper guide 73 and the paper guides 71 and 72, a paper transport path 80 through which the paper P is transported is formed. The separation unit 30 and the paper guide 73 are disposed above the paper conveyance path 80 and face the printing surface of the paper P. On the other hand, the paper guides 71 and 72 are disposed below the paper transport path 80. Here, the printing surface of the paper P is a surface on which the toner image of the paper P is formed. In double-sided printing, the surface on which the toner image is formed immediately before.

[Configuration of separation unit]
FIG. 4 is a cross-sectional view of the separation unit 30 and its surroundings. FIG. 5 is a cross-sectional view of the separation unit 30. FIG. 6 is a perspective view of the separation unit 30. Hereinafter, the configuration of the separation unit 30 will be described with reference to FIGS. 4 to 6.

  The separation unit 30 includes a separation plate 31 as a separation member, a holding member 32, contact members (or spacers) 33 and 34, springs 35 and 36 as urging members, a guide roller 37, and a paper guide 38.

  The separation plate 31 is a member that separates the paper P discharged from the nip portion N1 from the fixing belt 11. The separation plate 31 is disposed opposite or close to the fixing belt 11 on the downstream side of the nip portion N1 in the paper conveyance direction. The separation plate 31 is a plate-like member, and is preferably thin from the viewpoint of preventing dew condensation, and specifically, it is preferably 0.5 mm or less. The separation plate 31 is formed by processing, for example, one sheet metal. Here, the separation plate 31 is made of a stainless steel plate having a thickness of 0.3 mm.

  The separation plate 31 includes a separation guide portion 31a that separates the paper P discharged from the nip portion N1 from the fixing belt 11, and an extension portion 31b that extends from the downstream end of the separation guide portion 31a in the paper conveyance direction. Have. These will be described in detail later.

  The holding member 32 is a member that holds the separation plate 31. Specifically, the holding member 32 holds the extending portion 31 b of the separation plate 31. The holding member 32 is a plate-like member extending in the width direction, and has a plate thickness that is thicker than the separation plate 31. The holding member 32 is made of the same material as that of the separation plate 31 so that the thermal expansion coefficient is the same as that of the separation plate 31. The holding member 32 is formed by processing one sheet metal, for example. Here, the holding member 32 is made of a stainless steel plate having a plate thickness of 1.0 mm. The separation plate 31 is fixed to the holding member 32 by spot welding, for example. The holding member 32 is supported by the fixing frame 21 so as to be rotatable around a rotation axis extending in the width direction. Specifically, the holding member 32 is rotatably attached to a shaft 41 that is fixed to the fixing frame 21 and extends in the width direction.

  The contact members 33 and 34 are attached to the separation plate 31, and form a fixed gap G between the separation plate 31 (specifically, the separation guide portion 31 a) and the fixing belt 11 by contacting the fixing belt 11. To do. The gap G is, for example, 0.2 to 0.5 mm. The contact members 33 and 34 are made of a resin having good sliding properties. The contact members 33 and 34 are attached to both end portions of the separation plate 31 in the width direction. Specifically, the contact members 33 and 34 are regions (hereinafter referred to as “maximum sheet passing”) in the width direction in which the maximum width sheet that can be conveyed by the fixing device 500 (or that can be used by the image forming apparatus 1) is conveyed. It is arranged on both outer sides of the “region”. The contact members 33 and 34 are fixed to the holding member 32 while being positioned by the separation plate 31. Here, the contact members 33 and 34 are screwed to the holding member 32 by male screws 42 and 43, respectively.

  The springs 35 and 36 urge the holding member 32 in a direction in which the contact members 33 and 34 come into contact with the fixing belt 11. Specifically, the springs 35 and 36 are torsion springs, and their coil portions are arranged around the shaft 41, one arm is locked to the holding member 32, and the other arm is locked to the fixing frame 21. Yes. Due to the urging force of the springs 35 and 36, the contact members 33 and 34 are in contact with the fixing roller 12 with the fixing belt 11 interposed therebetween, and the separation plate 31 is arranged with a certain gap G from the fixing belt 11.

  The guide roller 37 is arranged on the downstream side of the separation plate 31 (specifically, the separation guide portion 31a) in the paper conveyance direction, and guides the paper P discharged from the fixing unit 10 while rotating along the paper conveyance direction. To do. The guide roller 37 extends over the maximum sheet passing area in the width direction. The length in the width direction of the guide roller 37 is longer than the width of the maximum sheet passing area. The guide roller 37 is disposed in the vicinity of the separation plate 31. The guide roller 37 is disposed so as to protrude from the surface of the separation plate 31 that contacts the paper P (specifically, the lower surface 31h of the separation guide portion 31a described later) to the paper P side (or the paper conveyance path 80 side). Is done. The guide roller 37 is disposed so as to contact the printing surface of the paper P.

  The guide roller 37 is configured to rotate following the paper P when the paper is conveyed. Specifically, the guide roller 37 is supported by the holding member 32 so as to be rotatable around a rotation axis extending in the width direction. More specifically, the holding member 32 is supported at both ends in the width direction via bearings 44. Further, outside the holding member 32 in the width direction, E-rings 45 for preventing falling off are attached to both ends of the guide roller 37 to restrict the movement of the guide roller 37 in the axial direction.

  The paper guide 38 extends in the paper transport direction and guides the paper P discharged from the fixing unit 10. The paper guide 38 is fixed to the holding member 32. Specifically, the paper guide 38 is screwed to the holding member 32 with a male screw 46. The paper guide 38 has an upstream guide 38a and a downstream guide 38b. The upstream guide 38 a is a guide member that guides the paper P and is disposed on the downstream side of the separation guide portion 31 a and the upstream side of the guide roller 37 in the paper transport direction so as to face the extension portion 31 b. The upstream guide 38a is arranged so that the paper P does not come into contact with the extending portion 31b. The downstream guide 38b is disposed on the downstream side of the guide roller 37 in the paper transport direction and guides the paper P. The upstream guide 38a and the downstream guide 38b have a plurality of ribs arranged in the width direction and extending in the sheet conveyance direction so that the contact area with the sheet P becomes small.

FIG. 7 is a diagram illustrating how the paper P is conveyed in the fixing device 500.
As shown in FIG. 7, the guide roller 37 is disposed so that the guide roller 37 contacts the paper P when the paper P is stretched between the fixing unit 10 and the conveyance roller pair 50. Specifically, when viewed from the width direction, the guide roller 37 includes an exit (an end portion on the downstream side in the paper conveyance direction) of the nip portion N1 of the fixing unit 10 and an inlet (a paper conveyance direction) of the nip portion N2 of the pair of conveyance rollers 50. It is arranged so as to protrude toward the sheet conveyance path 80 from the straight line connecting the upstream end).

  Further, the paper guide 38 is disposed so that the paper guide 38 does not come into contact with the paper P when the paper P is stretched between the fixing unit 10 and the conveying roller pair 50. Specifically, the upstream guide 38a is disposed so as not to protrude toward the sheet conveyance path 80 from a straight line that contacts the outer periphery of the guide roller 37 through the exit of the nip portion N1 of the fixing unit 10 when viewed from the width direction. Is done. The downstream guide 38b is disposed so as not to protrude toward the sheet conveyance path 80 from a straight line that contacts the outer periphery of the guide roller 37 through the entrance of the nip portion N2 of the conveyance roller pair 50 when viewed in the width direction.

  Further, the paper guides 71 to 73 are also arranged so that the paper guides 71 to 73 do not come into contact with the paper P when the paper P is stretched between the fixing unit 10 and the conveying roller pair 50. Specifically, when viewed from the width direction, the sheet guide 73 does not protrude toward the sheet conveyance path 80 from the straight line that contacts the outer periphery of the guide roller 37 through the entrance of the nip portion N2 of the conveyance roller pair 50. Be placed.

  In the fixing device 500, when the paper P is stretched between the fixing unit 10 and the conveyance roller pair 50, the paper P contacts only the guide roller 37 between the fixing unit 10 and the conveyance roller pair 50. Composed.

Hereinafter, the configuration of the separation unit 30 will be described in more detail.
(Configuration of separation plate)
FIG. 8 is a cross-sectional view of the separation plate 31 and the holding member 32 when cut along a plane perpendicular to the width direction. FIG. 9 is a perspective view of the separation plate 31 and the holding member 32. The configuration of the separation plate 31 will be described mainly with reference to FIGS. 8 and 9.

  The separation plate 31 includes a separation guide portion 31a that separates and guides the paper P discharged from the nip portion N1 from the fixing belt 11, an extension portion 31b that extends from the separation guide portion 31a, and contact members 33 and 34. Are attached portions 31c and 31d to which are attached.

  The separation guide portion 31a is disposed on the downstream side of the nip portion N1 in the sheet conveyance direction so as to face or be close to the fixing belt 11 along the width direction. The separation guide portion 31a has a long shape extending in the width direction, and extends over the maximum sheet passing area in the width direction. The length in the width direction of the separation guide portion 31a is longer than the width of the maximum sheet passing area.

  The separation guide portion 31a extends in the guide direction (left and right direction in FIG. 8) along the paper conveyance direction. The length L1 in the guide direction of the separation guide portion 31a is preferably short from the viewpoint of preventing condensation, and specifically, is preferably 5 mm or less, and is 4 mm here.

  The separation guide portion 31a includes a leading end portion 31e that is an end portion on the upstream side in the paper transport direction and a rear end portion 31f that is an end portion on the downstream side in the paper transport direction. The front end portion 31e and the rear end portion 31f extend in the width direction in parallel with each other.

  The separation guide portion 31a has an upper surface 31g and a lower surface 31h. The upper surface 31g and the lower surface 31h are surfaces extending in the guide direction and the width direction, and are opposed to each other in the thickness direction of the separation guide portion 31a (the direction perpendicular to the guide direction and the width direction, the vertical direction in FIG. 8). The lower surface 31h is coated with fluorine.

  In the following, for convenience of explanation, as indicated by arrows X, Y, and Z in FIGS. 8 and 9, the direction parallel to the guide direction is the “X direction”, the direction parallel to the width direction is the “Y direction”, X A direction orthogonal to the Y direction (thickness direction of the separation guide portion 31a) is referred to as a “Z direction”. The Z direction coincides with, for example, the vertical vertical direction or the vertical direction of the fixing device 500. Among the X directions, the direction on the paper transport direction side is referred to as “+ X direction”, and the opposite direction is referred to as “−X direction”. Of the Y direction, the right side (the front side in FIG. 8) of the fixing device 500 viewed from the + X direction side is referred to as “+ Y direction”, and the opposite direction is referred to as “−Y direction”. Of the Z direction, the direction from the paper conveyance path 80 toward the separation guide portion 31a is referred to as “+ Z direction”, and the opposite direction is referred to as “−Z direction”. In other drawings, arrows indicating the X, Y, and Z directions are also illustrated.

  The extension part 31b is provided so as to extend from the rear end part 31f of the separation guide part 31a. The extending portion 31b is bent with respect to the separation guide portion 31a (or the guide direction) in a direction away from the paper P (or a plane including the lower surface 31h) toward the downstream side in the paper transport direction. That is, the separation plate 31 is bent in a direction away from the paper P on the downstream side in the paper transport direction. The bending angle of the separation plate 31 (or the inclination angle of the extending portion 31b with respect to the separation guide portion 31a) θ is preferably 30 degrees or more, and here, 45 degrees. Therefore, the separation plate 31 is bent by 45 degrees in the direction away from the paper transport path 80 at a portion 4 mm away from the leading end 31 e in the + X direction. In this example, the separation plate 31 is bent, but may be curved, for example.

  The extending portion 31b has a long shape extending in the Y direction, and extends over the entire length of the separation guide portion 31a in the Y direction. Here, the “full length” is not limited to the full length in a strict sense, but includes a substantially full length.

  The attached portions 31c and 31d are provided on the outer side in the Y direction (+ Y direction side, −Y direction side) of the separation guide portion 31a, respectively. Details of the attached portions 31c and 31d will be described later.

(Configuration of holding member)
Next, the configuration of the holding member 32 will be described mainly with reference to FIGS. 8 and 9.
The holding member 32 has a separation plate fixing portion 32 a that fixes the separation plate 31. An extending portion 31b is in contact with and fixed to the separation plate fixing portion 32a. The separation plate fixing portion 32a contacts the back surface of the extension portion 31b on the side opposite to the paper conveyance path 80. Further, the separation plate fixing portion 32a contacts the extension portion 31b over the entire length of the extension portion 31b in the Y direction. Specifically, the separation plate fixing portion 32a contacts the entire back surface of the extending portion 31b. Here, “full length” and “whole” are not limited to the full length and the whole in a strict sense, respectively, but include substantially the whole length and the whole. The extending part 31b is fixed to the separation plate fixing part 32a by spot welding at a plurality of welding points WP along the Y direction.

  In addition, the holding member 32 includes contact member fixing portions 32b and 32c for fixing the contact members 33 and 34, guide roller support portions 32d and 32e for supporting the guide roller 37, and paper guide fixing for fixing the paper guide 38. Part 32f.

  The contact member fixing portions 32b and 32c are provided on the outer side in the Y direction (+ Y direction side, −Y direction side) of the separation plate fixing portion 32a, respectively. Details of the contact member fixing portions 32b and 32c will be described later.

  The guide roller support portions 32d and 32e are provided on the outer side in the Y direction (+ Y direction side and −Y direction side) of the separation plate fixing portion 32a, and the shaft 41 is inserted into the bearing holding portion 32g that holds the bearing 44. It has an insertion hole 32h and a locking portion 32i for locking the arms of the springs 35 and 36.

  The paper guide fixing portion 32 f is provided on the + Z direction side of the separation plate fixing portion 32 a and has a female screw 32 j that is screwed into the male screw 46.

(Contact member positioning structure)
FIG. 10 is a perspective view showing a state before the contact member 33 is attached, and FIG. 11 is a perspective view showing a state after the contact member 33 is attached. The positioning structure of the contact member 33 will be described mainly with reference to FIGS. 10 and 11.

  The mounted portion 31 c of the separation plate 31 has a mounted surface 31 i to which the contact member 33 is mounted. The mounted surface 31i forms the same plane as the lower surface 31h of the separation guide portion 31a. Specifically, the attached portion 31c is formed so as to extend in the + Y direction from the separation guide portion 31a, and an upper surface and a lower surface that form the same plane as the upper surface 31g and the lower surface 31h of the separation guide portion 31a ( (Attached surface) 31i. The attached surface 31 i comes into contact with an attachment surface 33 a provided on the contact member 33.

  The contact member 33 has an engaging portion 33b, and the attached portion 31c has an engaged portion 31j. The engaged portion 31j positions the position of the abutting member 33 with respect to the separation plate 31 in the X direction by engaging with the engaging portion 33b. Specifically, the engaged portion 31j is provided on the attached surface 31i, and the engaging portion 33b is provided on the attaching surface 33a. More specifically, the engagement surface 31i is provided with two engagement holes 31k and 31l. The engagement holes 31k and 31l penetrate in the Z direction and are arranged at a predetermined interval in the X direction. The attachment surface 33a is provided with two engagement protrusions 33c and 33d, and the engagement protrusions 33c and 33d are fitted into the engagement holes 31k and 31l, thereby contacting the separation plate 31 in the X and Y directions. The position of the member 33 is positioned. Note that it is only necessary that the contact member 33 can be positioned. For example, one engagement hole and one engagement protrusion may be provided.

  The attached portion 31c is provided farther from the fixing belt 11 than the separation guide portion 31a, and the tip portion 31m on the −X direction side of the attachment portion 31c is retracted in the + X direction from the tip portion 31e of the separation guide portion 31a. Formed in position. On the other hand, the contact member 33 includes a contact piece 33e that contacts the fixing belt 11 and a support piece 33f that supports the contact piece 33e. 33 f of support pieces have the attachment surface 33a, and oppose the to-be-attached surface 31i. The contact piece 33e protrudes in the −X direction from the support piece 33f, and is formed so as to protrude from the −Z direction side of the attached portion 31c to the + Z direction side, and the distal end portion 31m of the attached portion 31c. It is sandwiched between the fixing belt 11. The contact piece 33e has a contact surface 33g that contacts the fixing belt 11 at the tip portion on the −X direction side.

(Abutting member fixing structure)
Next, a structure for fixing the contact member 33 will be described mainly with reference to FIGS. 10 and 11.
The contact member fixing portion 32b of the holding member 32 is provided so as to face the attached portion 31c of the separation plate 31 in the Z direction. Here, the contact member fixing portion 32b is provided on the + Z direction side of the attached portion 31c. The contact member fixing portion 32b has a female screw 32k extending in the Z direction.

  The attached portion 31c has a through hole 31n penetrating in the Z direction at a position corresponding to the female screw 32k (see FIG. 9). The through hole 31n is provided between the two engagement holes 31k and 31l. The engagement holes 31k and 31l and the through hole 31n are arranged linearly in the X direction.

  The contact member 33 has a through hole 33h penetrating in the Z direction at a position corresponding to the female screw 32k. The through hole 33h is provided between the two engaging protrusions 33c and 33d, and the engaging protrusions 33c and 33d and the through hole 33h are arranged linearly in the X direction.

  The male screw 42 is screwed into the female screw 32k of the holding member 32 through the through hole 33h of the contact member 33 and the through hole 31n of the attached portion 31c. Thereby, the contact member 33 is fixed to the holding member 32.

  Note that the positioning structure and the fixing structure of the contact member 34 are the same as described above, and a description thereof will be omitted.

(Configuration of guide roller)
12A and 12B are a side view and a sectional view of the guide roller 37, respectively. Hereinafter, the configuration of the guide roller 37 will be described with reference to FIGS.

  The guide roller 37 has a shaft 37a that is rotatably provided and extends in the width direction. If the shaft 37a is bent, the desired effect of the guide roller 37 may not be sufficiently obtained. Therefore, the shaft 37a desirably has high rigidity, and is preferably made of metal. Here, the shaft 37a is made of free-cutting steel (SUM24L) having a diameter of 4 mm.

  A heat insulating layer 37b is provided on the outer periphery of the shaft 37a. The heat insulating layer 37b has a lower thermal conductivity than the shaft 37a. The heat insulating layer 37b is preferably made of a foam (or sponge), and more preferably a heat resistant foam. Here, since it has high heat insulation and heat resistance, a foamed melamine resin is used. The thickness of the heat insulating layer 37b is preferably 1 mm or more, for example, 1 mm to 2 mm, and 1.5 mm here. The heat insulating layer 37b is fixed to the shaft 37a with an adhesive.

  A release layer 37c is provided on the outer periphery of the heat insulating layer 37b. The release layer 37c has a higher release property with respect to the toner than the heat insulating layer 37b. Preferably, the release layer 37c is made of a fluorine-based material (specifically, a fluororesin). Here, the release layer 37c is composed of a tube made of a fluorine-based material, specifically, a heat-shrinkable PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) tube. The PFA tube is thermally contracted to cover the surface of the heat insulating layer 37b.

  Here, the more the air layer (or bubbles) contained in the foam, the lower the thermal conductivity of the foam, the more likely the surface temperature of the guide roller 37 to rise, and a high effect on condensation can be obtained. Therefore, the smaller the density of the foam, the higher the effect on condensation. The density here refers to the mass of the foam divided by the volume of the foam in the mounted state (for example, the state installed between the shaft and the PFA tube) (the sum of the volume of the resin and the volume of the bubbles). Value.

When an experiment was performed using the image forming apparatus of the present embodiment, when a melamine sponge having a density of 0.015 g / cm ³ was used, a sufficient effect on condensation was obtained. When a silicon sponge having a density of 1.14 g / cm ³ was used, the effect was less than when a melamine sponge was used, but it was more effective than a case where a heat insulating layer was not provided. The density of a free state of the melamine sponge is 0.010 g / cm ^3, the density of a free state of the silicon sponge was 1.0 g / cm ^3. Here, the density in the free state is a value obtained by dividing the mass of the foam by the volume of the foam in a state before mounting.

[Operation of Image Forming Apparatus]
Hereinafter, the operation of the image forming apparatus 1 will be described.
Upon receiving a print command from a host device (not shown), the control unit 801 controls each unit of the image forming apparatus 1 so that the following printing operation is performed.

  Referring to FIG. 1, the sheets P stored in the sheet tray 100 are fed one by one by the sheet feeding unit 200 and conveyed to the transfer belt 421 by the sheet conveying unit 300. On the other hand, the toner image forming units 410K, 410Y, 410M, and 410C form toner images on the photosensitive drum 411, respectively. The toner images of the respective colors formed on the respective photoconductive drums 411 are sequentially superimposed and transferred onto the paper P on the transfer belt 421 by the transfer unit 420. The sheet P on which the toner image is transferred is nipped and conveyed by the nip portion N1 of the fixing device 500. At this time, the toner image is heated and pressurized and fixed on the paper P. The fixed sheet P is conveyed by the conveyance roller pair 50 and the discharge roller pairs 601 and 602 and is discharged to the stacking unit 604.

  Referring to FIGS. 2 and 3, in fixing device 500, power supply from power supply unit 803 to heating member 13 is started by the start of the printing operation, and heating member 13 heats fixing belt 11. In addition, the driving of the fixing roller 12 by the driving unit 802 is started, the fixing roller 12 rotates, and the fixing belt 11 and the pressure roller 16 rotate in conjunction with the rotation. The control unit 801 controls the power supplied to the heating member 13 based on the detected temperature of the temperature detecting member 25 so that the temperature of the fixing belt 11 becomes a predetermined temperature. The control unit 801 controls the conveyance of the paper P based on the detected temperature of the temperature detection member 25 so that the paper P reaches the nip portion N1 after the temperature of the fixing belt 11 reaches a fixable temperature. .

  3 and 4, when the paper P passes through the nip portion N1, the paper P stuck to the fixing belt 11 is separated from the fixing belt 11 by the separation plate 31 and conveyed. Specifically, the paper P is separated by the separation guide portion 31a and moves in contact with the lower surface 31h of the separation guide portion 31a. Thereafter, the paper P is guided and moved by the paper guides 38, 71 to 73 and the guide roller 37, and reaches the conveyance roller pair 50. At that time, the paper P does not come into contact with the extending portion 31 b of the separation plate 31.

  Since the sheet conveying speed VE of the conveying roller pair 50 is faster than the sheet conveying speed VF of the fixing unit 10, the conveying roller pair 50 conveys the sheet P while pulling. For this reason, as shown in FIG. 7, the paper P is transported in a stretched state between the transport roller pair 50 and the fixing unit 10. At this time, the paper P comes into contact with the guide roller 37, and the guide roller 37 rotates in the direction of the arrow A5 in FIG.

  During the printing operation, the sheet P is heated by the fixing unit 10, so that water vapor is generated from the sheet P, and condensation may occur in a portion where the surface temperature of the fixing device 500 is low.

  In the present embodiment, the separation guide portion 31 a is in the vicinity of the fixing belt 11, is thin and short, and has a small heat capacity. Therefore, the temperature rises rapidly due to heat from the fixing belt 11. For this reason, dew condensation does not occur in the separation guide portion 31a (that is, the portion of the separation plate 31 that contacts the paper P). On the other hand, since the extension part 31b is in contact with the holding member 32 having a large heat capacity, the temperature is less likely to rise than the separation guide part 31a, and condensation tends to occur. However, since the paper P does not come into contact with the extending portion 31b, even when the extending portion 31b is condensed, the paper P does not come into contact with water droplets on the extending portion 31b and get wet.

  Since the heat insulating layer 37b is provided between the shaft 37a and the release layer (surface layer) 37c, the surface temperature of the guide roller 37 is quickly increased by the heat from the fixing belt 11. For this reason, condensation is unlikely to occur on the guide roller 37.

  Since the paper guide 38 has a rib shape and has a small contact surface with the paper P, even when the paper guide 38 is condensed, water droplets are hardly attached to the paper P, and even if the paper guide 38 is attached, the paper guide 38 is slight.

[effect]
According to the present embodiment described above, the following effects (1) to (11) can be obtained.
(1) A portion of the separation plate 31 on the downstream side in the sheet conveyance direction is bent in a direction away from the sheet P. According to this configuration, the paper P can be prevented from getting wet due to condensation on the separation plate 31. Specifically, compared with the case where the separation plate is not bent, the region of the separation plate that contacts the paper can be narrowed, and adhesion of water droplets on the separation plate 31 to the paper P can be suppressed. . More specifically, the upstream portion of the separation plate 31 is close to the fixing belt 11 and thus easily warms up, so that condensation does not easily occur. On the other hand, the downstream portion of the separation plate 31 is farther from the fixing belt 11 than the upstream portion and is less likely to be heated and is likely to cause condensation, but is bent in a direction away from the paper P. Water droplets hardly adhere to P. Furthermore, since the rigidity can be increased by bending the separation plate 31, the separation plate 31 can be thinned to reduce the heat capacity, thereby suppressing the occurrence of condensation. As a result, a high-quality printed matter can be obtained. For example, a high-quality image can be obtained even when the speed is increased.

  (2) The downstream portion (extending portion 31 b) of the separation plate 31 is in contact with and fixed to the holding member 32. According to this configuration, it is possible to more effectively prevent the paper P from getting wet due to condensation on the separation plate 31. Specifically, the upstream portion of the separation plate 31 is not brought into contact with the holding member 32, so that dew condensation can be suppressed. On the other hand, in the downstream portion of the separation plate 31, dew condensation is likely to occur due to contact with the holding member 32, but it is possible to suppress adhesion of water droplets to the paper P by bending it away from the paper P. Can do.

  (3) The holding member 32 has a thicker thickness than the separation plate 31. According to this configuration, deformation such as bending of the separation plate 31 can be suppressed by the holding member 32, and the separation plate 31 can be made thin.

  (4) The extending portion 31b extends over the entire length of the separation guide portion 31a in the width direction, and the holding member 32 contacts the extending portion 31b over the entire length of the extending portion 31b in the width direction. According to this configuration, deformation such as bending of the separation plate 31 can be satisfactorily suppressed.

  (5) The mounted portion 31c has a mounted surface 31i that forms the same plane as the lower surface 31h of the separation guide portion 31a, and the contact member 33 has a mounting surface 33a that contacts the mounted surface 31i. According to this configuration, the contact member 33 can be accurately positioned with a simple configuration, and the gap G can be formed with high accuracy. Specifically, the contact member 33 can be easily and accurately positioned with respect to the separation plate 31 in the Z direction. Further, the engagement portion 33b is provided on the attachment surface 33a, and the engagement portion 31j that engages with the engagement portion 33b is provided on the attachment surface 31i, whereby the contact member 33 is moved in the X direction with respect to the separation plate 31. Positioning can be easily performed with high accuracy.

  (6) The contact member 33 is fixed to the holding member 32 while being positioned by the attached portion 31c. According to this configuration, since the contact member 33 is fixed to the holding member 32, it is not necessary to increase the thickness of the separation plate 31 in order to fix the contact member 33.

  (7) The guide roller 37 is disposed so as to protrude to the paper P side from the surface of the separation plate 31 that contacts the paper P (specifically, the lower surface 31h). According to this configuration, the paper P can be guided by the guide roller 37 so as to be away from the separation plate 31 (specifically, the lower surface 31h). As a result, contact between the paper P and the separation plate 31 can be reduced, and toner adhesion from the paper P to the separation plate 31 and toner adhesion from the separation plate 31 to the paper P can be suppressed.

  (8) The guide roller 37 extends over the maximum sheet passing area in the width direction. According to this configuration, image defects caused by the guide roller 37 can be suppressed. Specifically, when the guide roller has a short width dimension and the guide roller is in contact with a part of the paper P, an image defect such as a contact mark of the guide roller on the printed image may occur. There is. For example, streaks may occur on the printed image due to the toner being peeled off from the paper by the edge of the guide roller, or the peeled toner adhering to another paper portion. Further, there may be a difference in gloss on the printed image between a portion that contacts the guide roller and a portion that does not contact the guide roller. On the other hand, according to the present configuration, it is possible to avoid the above problem caused by the guide roller coming into contact with a part of the sheet.

  (9) The guide roller 37 has a release layer 37c on the surface. Thereby, the adhesion of toner from the paper P to the guide roller 37 can be suppressed.

  (10) The guide roller 37 has a heat insulating layer 37b provided on the outer periphery of the shaft 37a. Thereby, the heat transfer between the surface of the guide roller 37 and the shaft 37a can be suppressed, and the condensation of the guide roller 37 can be suppressed.

  (11) In the fixing device 500, when the paper P is stretched between the fixing unit 10 and the conveyance roller pair 50, the paper P contacts only the guide roller 37 between the fixing unit 10 and the conveyance roller pair 50. Configured to do. According to this configuration, when the paper P is conveyed in a stretched state, it is possible to prevent the toner image from being distorted by the paper P being rubbed by a paper guide or the like.

  In the present specification, “parallel” is not limited to parallel in a strict sense, but includes substantially parallel.

  Further, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist of the present invention.

  For example, the guide roller 37 may be modified as shown in the following (a) to (h), and these modified examples may be appropriately combined.

  (A) The heat insulation layer 37b is not limited to a foam, and may be made of, for example, a solid resin material. For example, when the heat capacity or thermal conductivity of the shaft 37a is sufficiently small, or when the heat insulating layer 37b is sufficiently thick, solid can be used.

  (B) The release layer 37c is not limited to a fluororesin tube, and may be formed by, for example, a fluororesin coat.

  (C) The heat insulating layer 37b may be omitted, and the release layer 37c may be provided on the surface of the shaft 37a. For example, when the heat capacity or thermal conductivity of the shaft 37a is sufficiently small, the heat insulating layer 37b can be omitted.

  (D) The release layer 37c may be omitted, and the heat insulating layer 37b may be provided as a surface layer on the surface of the shaft 37a. For example, when the release property of the heat insulating layer 37b is sufficiently high, the release layer 37c can be omitted.

  (E) The heat insulating layer 37b and the release layer 37c may be omitted, and the guide roller 37 may be configured only by the shaft 37a. For example, when the heat capacity or thermal conductivity of the shaft 37a is sufficiently small and the releasability is sufficiently high, the heat insulating layer 37b and the release layer 37c can be omitted.

  (F) An air layer may be provided inside the shaft 37a. Thereby, the heat capacity and thermal conductivity of the shaft 37a can be reduced. In one example, a hollow cylindrical member may be used as the shaft 37a.

  (G) The guide roller 37 may be configured such that, in the width direction, at least one end portion of the heat insulating layer 37b is positioned inside the corresponding end portion of the release layer 37c. In the example of FIG. 13, in the width direction, the length of the foam 37b is shorter than the PFA tube 37c, and the end 37d of the foam 37b is inward by a length L2 (for example, 2 mm) from the end 37e of the PFA tube 37c. Is located. According to this structure, it can prevent that the heat insulation layer (foam) 37b protrudes outside the mold release layer (PFA tube) 37c by thermal expansion.

  (H) The guide roller 37 may be rotated by a driving force from the driving unit 802. In this case, the guide roller 37 is driven so that the moving speed of the surface thereof is the same as the moving speed of the paper P.

  The guide roller 37 may be disposed between the fixing unit 10 and the conveyance roller pair 50 and may be provided at a place other than the separation unit 30. Further, the guide roller 37 may be omitted.

  In the above-described embodiment, the color printer has been described. However, the present invention can be applied to other types of image forming apparatuses such as a monochrome printer, a copying machine, a facsimile machine, and a multi-function peripheral (MFP). It is.

  DESCRIPTION OF SYMBOLS 1 Image forming apparatus, 10 Fixing part, 11 Fixing belt, 16 Pressure roller, 30 Separation unit, 31 Separation plate, 31a Separation guide part, 31b Extension part, 31c, 31d Mounted part, 31f Rear end part, 31h Lower surface 31i mounted surface, 31j engaged portion, 31k, 31l engaging hole, 31n through hole, 32 holding member, 32k female screw, 33, 34 abutting member, 33a mounting surface, 33b engaging portion, 33c, 33d Engagement protrusion, 33h through hole, 37 guide roller, 42 male screw, 400 image forming unit, 500 fixing device.

Claims (18)

A rotating fixing member, and a pressure member that forms a nip portion in contact with the fixing member, and heats the recording medium on which the toner image is formed while being sandwiched between the nip portions and conveyed. A fixing unit for fixing a toner image on the recording medium;
A plate-shaped separation member that separates the recording medium discharged from the nip portion from the fixing member;
A holding member for holding the separating member ;
An abutting member attached to the separating member ;
The separating member is
The recording medium is disposed downstream of the nip portion in the conveyance direction of the recording medium, facing the fixing member along the width direction of the fixing member orthogonal to the conveyance direction, and extends in the guide direction along the conveyance direction. A separation guide portion for separating and guiding the recording medium from the fixing member;
An extending portion that extends from the downstream end of the separation guide portion in the transport direction and is bent with respect to the separation guide portion in a direction away from the recording medium toward the downstream side in the transport direction ;
Provided outside the separation guide portion in the width direction, it has a <br/> and the attached part of the abutment member is attached,
The fixing device is characterized in that the contact member makes contact with the fixing member to form a fixed gap between the separation guide portion and the fixing member .   The fixing device according to claim 1, wherein the extending portion is fixed in contact with the holding member.   The fixing device according to claim 1, wherein the holding member is a plate-like member having a plate thickness larger than that of the separation member.   4. The separation guide unit according to claim 1, wherein the separation guide portion extends in a width direction over an area in which a recording medium having a maximum width that can be conveyed by the fixing device is conveyed. The fixing device described. The extending portion extends over the entire length of the separation guide portion in the width direction,
5. The fixing device according to claim 1, wherein the holding member is in contact with the extending portion over the entire length of the extending portion in the width direction. 6.   The fixing device according to claim 1, wherein the separation member and the holding member are made of the same material. The separation guide portion has a surface extending in the guide direction and the width direction,
The attached portion has an attached surface that forms the same plane as the surface of the separation guide portion;
Said abutment member, said fixing device according to any one of claims 1, characterized in that it has a contact with the mounting surface on the installation surface 6. The contact member has an engaging portion,
Wherein the attachment portion, said engagement by engagement portion engaging, claims 1 to 7, characterized in that it comprises an engagement portion for positioning a position of the contact member with respect to the separating member in the guide direction The fixing device according to any one of the above. The engaged portion is provided on the attached surface,
The fixing device according to claim 8 , wherein the engaging portion is provided on the mounting surface. The engaged portion has one or more engaging holes provided in the attached surface;
The fixing device according to claim 9 , wherein the engagement portion includes one or more engagement protrusions provided on the attachment surface and fitted into the one or more engagement holes. Said abutment member, said in a state of being positioned by the mounting portion, a fixing device according to any one of claims 1 to 10, characterized in that fixed to the holding member. The holding member has a female screw extending in a thickness direction orthogonal to the guide direction and the width direction,
The contact member and the attached portion are provided at a position corresponding to the female screw, and have a through hole penetrating in the thickness direction,
The fixing device includes a male screw that fixes the contact member to the holding member by being screwed with the female screw through the through hole of the contact member and the attached portion. The fixing device according to claim 11 . The guide member according to any one of claims 1 to 12 , further comprising a guide member that is disposed on the downstream side of the separation guide portion in the transport direction so as to face the extension portion and guides the recording medium. The fixing device according to 1. The guide roller according to claim 1, further comprising a guide roller that is disposed on the downstream side of the separation guide unit in the transport direction and guides the recording medium discharged from the fixing unit while rotating along the transport direction. 14. The fixing device according to any one of items 1 to 13 . The fixing device according to claim 14 , wherein the guide roller is disposed so as to protrude toward the recording medium from a surface of the separation guide portion that contacts the recording medium. The guide roller fixing device according to claim 14 or 15, characterized in that it is rotatably supported by the holding member. The guide rollers in the width direction, according to any one of claims 14 to recording medium of the maximum width that can be conveyed in the fixing device is characterized in that extending over the region to be conveyed 16 Fixing device. An image forming unit for forming a toner image on a recording medium;
An image forming apparatus characterized in that have a fixing device according to any one of claims 1 to 17 for fixing the toner image formed on the recording medium to the recording medium.

Images